The Eyes iii

THE FACTS ON FILE ENCYCLOPEDIA OF HEALTH AND MEDICINE

IN FOUR VOLUMES: VOLUME 1

An Amaranth Book iv The Eyes

To your health!

The information presented in The Facts On File Encyclopedia of Health and Medicine is provided for research purposes only and is not intended to replace consultation with or diagnosis and treatment by medical doctors or other qualified experts. Readers who may be experiencing a condition or disease described herein should seek medical attention and not rely on the information found here as medical advice.

The Facts On File Encyclopedia of Health and Medicine in Four Volumes: Volume 1

Copyright © 2007 by Amaranth Illuminare

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The Facts on File encyclopedia of health and medicine / Amaranth Illuminare and Deborah S. Romaine. p. ; cm. “An Amaranth book.” Includes index. ISBN 0-8160-6063-0 (hc : alk. paper) 1. Medicine—Encyclopedias. 2. Health—Encyclopedias. [DNLM: 1. Medicine—Encyclopedias—English. 2. Physiological Processes—Encyclopedias—English. WB 13 R842f 2006] I. Title: Encyclopedia of health and medicine. II. Romaine, Deborah S., 1956- III. Facts on File, Inc. IV. Title. R125.R68 2006 610.3—dc22 2005027679

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This book is printed on acid-free paper. The Eyes v

CONTENTS VOLUME 1

Foreword by Maureen Pelletier, M.D., C.C.N., F.A.C.O.G. vii How to Use The Facts On File Encyclopedia of Health and Medicine ix Preface to Volume 1 xiii The Ear, Nose, Mouth, and Throat 1 The Eyes 65 The Integumentary System 125 The Nervous System 212 The Musculoskeletal System 290 Pain and Pain Management 361 Medical Advisory Review Panel 391 Index 395

v vi The Eyes FOREWORD

A big part of my role as a physician is educating your body in isolation from other body structures my patients about their health. I take as much and functions. Your body attempts to compensate time as each person needs to explain prevention and adjust, often without your awareness, until it measures, test results, and treatment options. I can no longer accommodate the injury or illness. encourage questions. But in the moment, sitting The symptoms you bring to your doctor may there in my office, most people do not yet know reflect this compensation, for example frequent what to ask me. By the time questions flood headaches that point not to brain tumor (as many their thoughts, they may be back at work or at people fear but is very rare) but to eye strain or home. muscle tension or sometimes to hypertension Numerous events and circumstances can chal- (high blood pressure). lenge health, and we all need to know what In my medical practice I emphasize integrative actions we can take to keep ourselves healthy as health care, embracing the philosophy that health well as to obtain appropriate treatment for health exists as the intricate intertwining of the body’s conditions that do affect us. Knowledge empow- many systems, structures, and functions. So, too, ers all of us to make informed and appropriate does the care of health. I received my medical decisions about health care. Certainly there is no degree from Tufts University School of Medicine shortage of reference material. Yet there is so in Boston, an institution noted for remaining at much information available today! Even for the forefront of the medical profession. I also physicians, it is challenging to keep up. How can completed clinical programs in Mind-Body Medi- you get to the core of what you want to know, cine at Harvard University, Integrative Medicine at reliably and to the level of detail you need? the University of Arizona School of Medicine, and The Facts On File Encyclopedia of Health and Medi- Medical Acupuncture at the University of Califor- cine is a great resource for up-to-date health infor- nia-Los Angeles (UCLA). I am a board-certified mation presented in a manner that is both obstetrician-gynecologist, a board-certified clinical comprehensive and easy to understand no matter nutritionist, and a licensed acupuncturist. I see what your level of medical knowledge. The ency- patients in my practice in Cincinnati, Ohio; I clopedia organizes entries by body system. The teach, I lecture, and I frequently go on television progression of body systems—and entries— and radio to talk about health topics. In each of throughout the encyclopedia presents topics the these areas, I encourage people to think about way you think about them. their health and health concerns from an integra- Going beyond this basic structure, however, is tive perspective. When you understand your another layer of organization that particularly health from multiple dimensions, you can better appeals to me, which is a comprehensive structure understand what to do to keep yourself as healthy of cross references that integrates entries across as possible. body systems. After all, your body functions in an I wish you the best of health for all of a long, integrated way; so, too, should a reference series satisfying life. But when the time comes that you that discusses your body’s health. Not very much must make decisions about medical care, I want that happens with your health affects one part of you to have the knowledge to make informed vii viii Foreword choices that are right for you. Whether you start Encyclopedia of Health and Medicine to be a most here and move on to more specialized resources valuable reference resource. or locate all the information you need within —Maureen M. Pelletier, M.D., C.C.N., these four volumes, you will find The Facts On File F.A.C.O.G. HOW TO USE THE FACTS ON FILE ENCYCLOPEDIA OF HEALTH AND MEDICINE

Welcome to The Facts On File Encyclopedia of Health with its surroundings and the external envi- and Medicine, a four-volume reference set. This ronment. comprehensive resource is an indispensable refer- • Volume 2 presents the cell- and fluid-based ence for students, allied health professionals, body systems that transport nutrients, remove physicians, caregivers, lay researchers, and people molecular wastes, and provide protection from seeking information about health circumstances infection. and conditions for themselves or others. Entries • Volume 3 presents the biochemical body sys- present the latest health concepts and medical tems that support cellular functions. knowledge in a clear, concise format. Readers may easily accumulate information and build a com- • Volume 4 presents topics that apply across plete medical profile on just about any health or body systems (such as “Fitness: Exercise and medical topic of interest or concern. Health”) or that address broad areas within health care (such as “Preventive Medicine”). A New Paradigm for the • The appendixes provide supportive or additional Health and Medical Encyclopedia reference information (such as “Appendix X: As the art and science of health and medicine con- Immunization and Routine Examination tinues to evolve, with complex and elegant discov- Schedules”). eries and new techniques, medications, and treatments emerging all the time, the need has Following Research Pathways arisen for a new paradigm for the encyclopedia of The Facts On File Encyclopedia of Health and Medi- health and medicine—a rethinking of the old, and cine’s organization and structure support the increasingly outmoded, presentations. Carefully reader’s and researcher’s ease of use. Many ency- researched and compiled, The Facts On File Encyclope- clopedia users will find all the information they dia of Health and Medicine offers many distinguishing desire within one volume. Others may use several features that present readers and researchers with or all four of the encyclopedia’s volumes to arrive an organization as up-to-date and compelling as the at a comprehensive, multifaceted, in-depth under- breakthrough information its entries contain. standing of related health and medical concepts Recognizing the current emphasis on present- and information. Researchers efficiently look up ing a truly integrative approach to both health information in The Facts On File Encyclopedia of and disease, The Facts On File Encyclopedia of Health Health and Medicine in several ways. and Medicine organizes content across volumes Each section’s entries appear in alphabetical within a distinctive format that groups related order (except the entries in Volume 4’s “Emer- entries by body system (for example, “The Cardio- gency and First Aid” section, which are grouped vascular System”) or by general health topic (for by type of emergency). The researcher finds a example, “Genetics and Molecular Medicine”): desired entry by looking in the relevant volume and section. For example, the entry for acne is in • Volume 1 presents the sensory and structural Volume 1 in the section “The Integumentary Sys- body systems that allow the body to engage tem” and the entry for stomach is in Volume 3 in ix x How to Use the section “The Gastrointestinal System.” The Following the path of an encyclopedic entry’s researcher can also consult the index at the back internal cross references, as shown above, can of the volume to locate the entry, then turn to the illuminate connections between body systems; appropriate page in the volume. define and apply medical terminology; reveal a Terms that appear in SMALL CAPS within the text broad matrix of related health conditions, issues, of an entry are themselves entries elsewhere in and concerns; and more. The SMALL CAPS cross ref- The Facts On File Encyclopedia of Health and Medicine. erences indicated within the text of encyclopedic Encyclopedia users can look up the entries for entries lead encyclopedia users on wide-ranging those terms as well, for further information of research pathways that branch and blossom. potential interest. Such SMALL CAPS cross references At the end of the entry for hypertension a list typically provide related content that expands of cross references gathered in alphabetical order upon the primary topic, sometimes leading the links together groups of related entries in other user in new research directions he or she might sections and volumes, such as smoking cessa- otherwise not have explored. tion in Volume 4’s “Lifestyle Variables: Smoking For example, the entry hypertension is in the and Obesity,” to provide specific, highly relevant section “The Cardiovascular System.” The entry research strings. These see also cross references also presents a comprehensive discussion of the health appear in SMALL CAPS, identifying them at a glance. condition hypertension (high blood pressure), Encyclopedia users are encouraged to look here covering symptoms, diagnosis, treatment options, for leads on honing research with precision to a risk factors, and prevention efforts. Among the direct pathway of connected entries. numerous SMALL CAPS cross references within the So, extensive cross-references in The Facts On hypertension entry are the entries for File Encyclopedia of Health and Medicine link related topics within and across sections and volumes, in • retinopathy, an entry in the section “The both broad and narrow research pathways. This Eyes” in Volume 1, which discusses damage to approach encourages researchers to investigate the eye that may result from untreated or beyond the conventional level and focus of infor- poorly managed hypertension mation, providing logical direction to relevant • blood pressure, an entry in the Volume 2 sec- subjects. Each cross-referenced entry correspond- tion “The Cardiovascular System,” which dis- ingly has its own set of cross references, ever cusses the body’s mechanisms for maintaining widening the web of knowledge. appropriate pressure within the circulatory sys- tem Using the Facts On File Encyclopedia of Health and Medicine • stroke and heart attack, entries in Volume 2’s Each section of the encyclopedia begins with an “The Cardiovascular System” about significant overview that introduces the section and its key health conditions that may result from hyper- concepts, connecting information to present a tension comprehensive view of the relevant system of the • kidney, an entry in the section “The Urinary human body or health and medical subject area. System” in Volume 3, which discusses the kid- For most body systems, this overview begins with ney’s role in regulating the body’s electrolyte a list and drawings of the system’s structures and balances and fluid volume to control blood incorporates discussion of historic, current, and pressure future contexts. • atherosclerosis, diabetes, hyperlipidemia, Entries present a spectrum of information from and obesity, entries in the sections “The Car- lifestyle factors and complementary methods to diovascular System” in Volume 2, “The the most current technologic advances and Endocrine System” in Volume 3, and “Lifestyle approaches, as appropriate. Text that is set apart or Variables: Smoking and Obesity” in Volume 4, bold within an entry gives an important health and all of which are health conditions that con- warning, or targets salient points of interest to add tribute to hypertension layers of meaning and context. Lists and tables How to Use xi collect concise presentations of related informa- • Entries for diagnostic procedures begin with a tion for easy reference. general discussion of the test or procedure and Each type of entry (mid-length and longer) then incorporate content under the subhead- incorporates consistent elements, identified by ings “Reasons for Doing This Test,” “Prepara- standardized subheadings: tion, Procedure, and Recovery,” and “Risks and Complications.” • Entries for health conditions and diseases begin with a general discussion of the condition and Entries in Volume 4’s section “Emergency and its known or possible causes and then incorpo- First Aid” are unique within the orientation of The rate content under the subheadings “Symptoms Facts On File Encyclopedia of Health and Medicine in and Diagnostic Path,” “Treatment Options and that they feature instructional rather than infor- Outlook,” and “Risk Factors and Preventive mational content. These entries do not replace Measures.” appropriate training in emergency response • Entries for surgery operations begin with a gen- and first aid methods. Rather, these entries pro- eral discussion of the procedure and then incor- vide brief directives that are appropriate for guid- porate content under the subheadings “Surgical ing the actions of a person with little or no first aid Procedure,” “Risks and Complications,” and training who is first on the scene of an emergency. “Outlook and Lifestyle Modifications.” Each volume concludes with a complete, full • Entries for medication classifications begin with index for the sections and entries within the vol- a general discussion of the type of medication ume. Volume 4 of The Facts On File Encyclopedia of and its common uses and then incorporate con- Medicine contains a comprehensive index for all tent under the subheadings “How These Med- four encyclopedia volumes that researchers can ications Work,” “Therapeutic Applications,” and use to quickly and easily determine which vol- “Risks and Side Effects.” umes contain desired sections or entries. xii How to Use

The Facts On File Encyclopedia of Health and Medicine in Four Volumes

Volume 1 Volume 4 The Ear, Nose, Mouth, and Throat Preventive Medicine The Eyes Alternative and Complementary Approaches The Integumentary System Genetics and Molecular Medicine The Nervous System Drugs The Musculoskeletal System Nutrition and Diet Pain and Pain Management Fitness: Exercise and Health Volume Index Human Relations Surgery Lifestyle Variables: Smoking and Obesity Substance Abuse Volume 2 Emergency and First Aid The Cardiovascular System Appendixes: The Blood and Lymph I. Vital Signs The Pulmonary System II. Advance Directives The Immune System and Allergies III. Glossary of Medical Terms Infectious Diseases IV. Abbreviations and Symbols Cancer V. Medical Specialties and Allied Health Fields Volume Index VI. Resources VII. Biographies of Notable Personalities VIII. Diagnostic Imaging Procedures Volume 3 IX. Family Medical Tree The Gastrointestinal System X. Immunization and Routine Examination The Endocrine System Schedules The Urinary System XI. Modern Medicine Timeline The Reproductive System XII. Nobel Laureates in Physiology or Medicine Psychiatric Disorders and Psychologic Conditions Selected Bibliography and Further Reading Volume Index Series Index: Volumes 1–4 PREFACE TO VOLUME 1

Leading the reader into the four-volume The Facts structures of the inner ear also regulate the body’s On File Encyclopedia of Health and Medicine through balance, integrating with the nervous system as Volume 1 are the structures and functions that well as the musculoskeletal system (as anyone lead the body’s way in the world. These are the who has found it challenging to walk after spin- body systems that equip the body to interact with ning in circles well knows). its external environment. Some people refer to these as the “interface” systems, drawing from the The Eyes concepts and terminology of computers. These Sight is so highly refined in humans that many systems allow the body to receive and respond to people consider it the most important of the five sensory input. senses. The structures of vision function inde- pendently from other sensory structures, though The Ear, Nose, Mouth, and Throat the brain combines sensory information to Volume 1’s first section is the “The Ear, Nose, develop complex perspectives about the body’s Mouth, and Throat.” Through these structures the placement and function within its external envi- body receives auditory, olfactory, and gustatory ronment. sensory information—sounds, smells, and tastes. The two eyes work independently as well, The throat does double duty as the conduit to though synchronously. The brain blends and carry both air and nutrition, essential sustenance interprets the information it receives from each for the body, and also makes possible the uniquely eye to form images that have spatial dimension. human form of communication—speech. This provides depth perception, which interplays The functions of these sensory organs and with proprioception (the body’s sense of its place- structures overlap and integrate with each other ment within its physical environment) and move- in ways such that the loss of one sensory system ment. The loss of vision in one eye requires the affects others. Speech is difficult without the abil- brain to rely more on other sensory input and on ity to hear, for example, and the sensory path- learned responses to help the body navigate in a ways for smell and taste are so intertwined that dimensional world. both networks become impaired when one or the other does not function properly. Olfactory nerve The Integumentary System fibers are capable of detecting thousands of odors, The structures of the integumentary system— enhancing the brain’s ability to interpret hundreds skin, nails, and hair—cover and protect the body of flavors with input from only four basic taste from the external environment as well as provide qualities (sweet, sour, salt, and bitter). the basis for appearance and identity. Integument The sense of touch resides in specialized nerves is Latin for “cloak,” an apt term for the system that populate the surface of the skin in varying that envelops the body and literally holds it concentrations to provide different levels of tactile together. response. The lips and fingertips, for example, are The integumentary system provides front-line exquisitely sensitive, while the surfaces of the defense against infection as a barrier as well as arms and legs are less responsive to touch. The through immune cells and substances that reside xiii xiv Preface among the skin cells, helps maintains fluid and and strength. They use leverage and oppositional body temperature, and contains millions of sen- function to move the body—walk, run, jump, sory nerve cells. Most of the body’s pain receptors skip, and even turn cartwheels. These functions are among these nerve cells. Remarkably resilient require coordination with the nervous system, and flexible, the skin continually renews itself. sensory systems, and balance structures within the inner ear. Health conditions that affect the muscu- The Nervous System loskeletal system—ranging from injuries such as The nervous system is both command central (the sprains and fractures to degenerative processes brain) and intercellular highway (the nerves), such as osteoarthritis—are among the most com- orchestrating every function within the body— mon reasons people seek medical care. more often than not without conscious awareness of its myriad activities. The nervous system inter- Pain and Pain Management prets and responds to sensory information, contin- The final section in Volume 1 is “Pain and Pain uously adjusting and accommodating its functions. Management”—not, of course, a body system but These functions require chemical messengers— rather a discipline (specialty) within the practice neurotransmitters—as well as electrical activity of medicine that examines the interactions of the among cells. Nerves range in size from microscopic foundational body systems that, when disrupted, to several feet in length. result in pain. A complex physiologic experience, pain typically arising from multiple causes that The Musculoskeletal System cross these body systems. Consequently, so must Giving the body the ability to resist the force of its treatment approaches. The entries in “Pain and gravity to provide shape and mobility is the mus- Pain Management” cover the mechanisms of pain culoskeletal system—the bones, connective tis- as well as health conditions in which pain is the sues, and muscles. These structures have density primary symptom. The Eyes xv

THE FACTS ON FILE ENCYCLOPEDIA OF HEALTH AND MEDICINE

IN FOUR VOLUMES: VOLUME 1 xvi The Eyes THE EAR, NOSE, MOUTH, AND THROAT

The structures of the ear, nose, mouth, and throat carry out the functions of hearing, balance, smell, taste, speech, and swallowing. Practitioners in the medical field of otolaryngology specialize in providing care for these structures. This section, “The Ear, Nose, Mouth, and Throat,” presents a discussion of the structures and their functions, an overview of otolaryngologic health and disorders, and entries about the health conditions that can affect them.

Structures of the Ear, Nose, Mouth, and Throat Functions of the Ear, Nose, Mouth, and Throat EAR SINUSES The ears, nose, and mouth (along with the eyes) outer ear frontal are the primary features of the head and face. auricle (pinna) ethmoid They form the hallmarks of recognition and indi- auditory canal sphenoid vidual identity throughout life. Yet the functions middle ear maxillary of these features are far more than cosmetic. They TYMPANIC MEMBRANE (eardrum) olfactory bulb are important for survival as well as for refined EUSTACHIAN TUBE olfactory nerve ending sensory perception, making it possible to compre- inner ear MOUTH hend and interact with the external environment. malleus (hammer) lips Taste and smell, the chemosenses, provide the incus (anvil) cheeks combined sensation of flavor—a blend of the stapes (stirrup) tongue mouth’s ability to perceive four distinct tastes and oval window taste buds the nose’s ability to detect thousands of odors. COCHLEA palate Hearing allows the BRAIN to register sounds across organ of Corti SALIVARY GLANDS a broad spectrum of frequency and volume. round window parotid The structures responsible for sensory percep- cochlear NERVE submandibular tion begin to take shape as early as the third week bony labyrinth glossopharyngeal of embryonic development and function at a fairly membranous labyrinth lingual high level by birth. These senses—taste, smell, semicircular canals sublingual and hearing—serve as basic survival mechanisms vestibule buccal for newborns, helping them identify their moth- saccule labial ers, food sources, and hazards until other senses utricle THROAT and cognitive abilities adequately develop. Sur- vestibular nerve uvula vival also depends on the ability to suck or chew NOSE pharynx and swallow, requiring coordinated movements of nasal cavity epiglottis the structures of the mouth and throat. The nasal septum hyoid bone brain’s temporal lobe, which processes hearing, nostrils larynx language, and speech as well as smell, takes a mucous lining VOCAL CORDS developmental leap about three months after a nasal conchae baby’s birth, vastly expanding sensory perceptions and communication capabilities. Further cerebral 1

The Ear, Nose, Mouth, and Throat 3 development continues well into ADOLESCENCE, drawing fluid into the middle ear. Though the refining the brain’s ability to interpret and catego- fluid may relieve the sensation of pressure, it fur- rize the signals the senses send to it. ther constrains middle ear function. Blocked Functions of the ear: hearing and balance eustachian tubes establish ideal conditions for Hearing (audition) occurs through air conduction middle ear INFECTION (OTITIS media), allowing BAC- and BONE conduction of sound waves. The struc- TERIA to move into the middle ear. Until about age tures of the outer and middle ear facilitate air con- 10, the eustachian tubes are nearly horizontal. As duction. The outer ear, called the auricle or pinna, the child’s facial structure lengthens with maturity is a structure of CARTILAGE and SKIN that extends the eustachian tubes shift and angle downward from the side of the head. Its somewhat dishlike from the ears to the throat, improving their ability structure serves to “catch” sound waves traveling to drain congestion and remain open. through the air; its ridges and curves channel The vibration of the stapes against the oval those sound waves into the auditory canal. The window amplifies the energy of the sound waves auditory canal funnels and focuses the sound and sets in motion the fluid (endolymph) within waves, directing them to the TYMPANIC MEMBRANE the cochlea on the other side of the oval window. or eardrum, which vibrates in response. The tym- Fluid further focuses and aligns the sound waves panic membrane marks the end of the outer ear into patterns. A second membrane, the round and the start of the middle ear, creating a sealed window, dissipates excessive vibration into the chamber. Its vibration activates, in sequence, the fluid of the inner ear (perilymph) on its other side. three tiny auditory ossicles, or bones, of the mid- The moving endolymph within the cochlea in dle ear: first the malleus (hammer), then the incus turn stimulates microscopic fibers along a mem- (anvil), and finally the stapes (stirrup). The flat of brane that forms a structure within the cochlea the stapes rests against the oval window, a small called the organ of Corti. The fibers resonate to translucent membrane in the wall of the COCHLEA. specific sound waves, activating NERVE impulses in This point of contact represents the transition specialized cells called HAIR cells. The cochlear from the middle ear to the inner ear and from an nerve carries the nerve impulses to the eighth cra- environment of air to one of fluid. nial nerve (vestibulocochlear nerve), which in The middle ear is pressurized, allowing the turn transmits them to the brain’s temporal lobe. tympanic membrane and the auditory ossicles to The temporal lobe filters, interprets, and analyzes vibrate freely and without resistance. The the nerve impulses, translating them into sound EUSTACHIAN TUBE, a short canal of tissue, connects messages including language. the middle ear with the upper throat at the back The bony structures of the head and face also of the nose. Somewhat like an elongated valve, it conduct sound waves. Bone conduction bypasses serves to equalize pressure between the middle the outer and middle ears. Sound waves instead ear and the external environment. Swallowing travel as vibrations along the bones to the inner and yawning force air into the eustachian tube, ear, where they pass to the bony part of the causing it to open (sometimes with a perceptible cochlea. The vibrations of the bony cochlea pass to pop). Unequal pressure between the middle ear the endolymph, and the rest of the hearing and the atmosphere causes the tympanic mem- process unfolds. Sounds conveyed through bone brane to bulge in the direction of the lower pres- conduction are significantly restricted in tonal sure, altering its ability to convey the vibrations of range and volume because they bypass the ampli- sound waves. Circumstances that prevent the fying structures of the tympanic membrane and eustachian tube from opening to balance air pres- auditory ossicles. The sound waves of one’s own sure, such as a cold that fills the nasal passages voice travel primarily through bone conduction and eustachian tubes with congestion, causes the along the bones of the face, which explains why it sensation of muffled hearing and pressure in the seems so different when heard as a recording in ear. When pressure in the middle ear remains which the sound waves travel by air conduction. lower than the atmospheric pressure for a pro- The inner ear also manages the body’s balance longed time, the body attempts to compensate by and motion in relation to gravity. The structures 4 The Ear, Nose, Mouth and Throat and functions that do so make up the vestibular The nose is also the body’s organ of smell, system. The bony labyrinth, which also houses the responsible for the functions of olfaction. The first cochlea, supports the membranous labyrinth. Five cranial nerve (olfactory nerve) terminates in the fluid-filled structures within the membranous olfactory bulb and a bristlelike patch of olfactory labyrinth sense motion and movement: the three nerve endings along the roof of the nose. These semicircular canals, which sense rotational move- olfactory nerve endings detect the presence of ment, and the saccule and utricle, which sense odor molecules in the air that enters the nose. linear movement. The saccule senses movement Fibers of the palatine nerves, which detect taste, that is up-and-down; the utricle senses back-and- are also present along the floor of the nose, forth and left-to-right movement. These structures though not nearly in the abundance with which are all open to one another; however, they form a they infiltrate the mouth. The brain interprets the closed network among themselves that contains blend of nerve impulses from the palatine nerve endolymph. Movement causes shifts in pressure of endings and the olfactory nerve endings and inte- the endolymph, which nerve cells register and grates them into perceptions of flavor. send as electrical impulses to the vestibular nerve. Functions of the mouth and throat: taste, swal- The vestibular nerve conveys these impulses to lowing, and speech The mouth and throat make it the eighth cranial nerve, which in turn carries possible to eat and speak. The powerful masseter them to the brain. The brain interprets the muscles open and close the mandible (lower jaw), vestibular messages along with other input from generating over 500 pounds per square inch of sensory nerve cells (proprioceptors) located pressure as the TEETH come together to bite and in throughout the body, nearly instantaneously excess of 3,500 pounds per square inch of force at responding with neuromuscular signals that initi- the back teeth (molars) with chewing. The hyoid ate movement. bone helps anchor the back of the tongue, another Extremes of movement, such as rapid swinging powerful MUSCLE. The SALIVARY GLANDS, present in or spinning, can temporarily disrupt the vestibular pairs on each side of the mouth, produce two to system, causing dizziness and NAUSEA. Some people three pints of saliva every day. This watery liquid experience such symptoms with less extreme contains enzymes and mixes with food to begin movement, such as riding in a car, boat, or airplane, breaking it down, an early stage of digestion, as known commonly as motion sickness. More seri- well as to soften it for swallowing. The cheeks, ous dysfunctions and disorders of the vestibular tongue, and lips help contain food within the system, such as MÉNIÈRE’S DISEASE and LABYRINTHITIS, mouth and push it to the back of the throat for can result in debilitating loss of balance. swallowing; they also shape the flow of air and Functions of the nose: breathing and smell The create the formation of words during speech. nose protrudes from the front of the face. Its These functions require muscular control and placement allows it to draw air into the body in coordination. one of life’s most basic activities, BREATHING. Most The sense of taste is called gustation. Though of the nose’s external structure is CARTILAGE and common perception is that the bumps on the SKIN; the nasal bone is less than one half inch long. tongue are the taste buds, taste buds are micro- The ethmoid, vomer, and maxilla bones frame the scopic. The bumps are called papillae; they contain back of the nose. Ridges in these bones, the nasal clusters of taste buds. Each taste bud contains conchae, direct the flow of air into the SINUSES. dozens of taste cells. Though taste buds for the These chambers, along with the nose’s mucus lin- four categories of taste—sweet, sour, salt, and bit- ing, moisturize and warm each breath so it does ter—are present throughout the mouth, the not irritate the airways and lungs. A tissue wall, roughly 10,000 of them on the tongue align in the nasal septum, divides the nasal cavity into two patterns of concentration: channels, the nostrils. Tiny hairs line the inner nostrils and are responsible for keeping the nasal • Taste buds on the tip of the tongue are concen- passages clear of debris. trated to detect sweet. The Ear, Nose, Mouth, and Throat 5

• Taste buds on the sides of the tongue are con- the common causes of dysfunctions affecting swal- centrated to detect sour and salt. lowing and speech. • Taste buds at the back of the tongue are con- centrated to detect bitter. Health and Disorders of the Ears, Nose, Mouth, and Throat Three CRANIAL NERVES—the 7th (facial), 9th Disorders and dysfunctions of the ears, nose, (glossopharyngeal), and 10th (vagus)—carry mouth, and throat range from structural defects nerve impulses related to taste to the brain. At its present at birth to infections to trauma resulting most primitive level, taste helps the brain deter- from ACCIDENTAL INJURIES or diseases such as mine what is safe and what is hazardous to eat. CANCER. Disturbances of taste, smell, hearing, and Sweet substances generally contain sugars and balance may accompany numerous health condi- carbohydrates, essential nutrients for energy, tions from COLDS to DIABETES, stroke, and Parkin- whereas bitter substances may contain acids or son’s disease. Health experts estimate that about 2 chemicals that are potentially harmful. Recent million Americans have diminished, altered, or research indicates that gustation is far more com- lost functions of taste and smell. More than 28 plex than simple delineation among taste buds, million have a perceptible loss of hearing ability; 2 however, with some scientists speculating that million of them are profoundly deaf (unable to taste represents learned interpretations as much as hear at a functional level). Disturbances of balance response to specific qualities. Further, taste and resulting from dysfunctions of the inner ear affect smell are inextricably intertwined. Though distinct as many as 45 million Americans. nerve impulses from each reach the brain, the Nearly everyone experiences the most frequent brain analyzes them and creates collective inter- health condition that affects the chemosenses pretations. simultaneously: the common cold. Its familiar The functions of breathing and swallowing share symptoms include nasal congestion and runny the structures of the throat. The chamber at the nose (RHINORRHEA), sore throat (PHARYNGITIS), and back of the mouth and the top of the throat is the the sensation of “stuffy” ears and muffled hearing pharynx; it receives both air and food. A flap of car- (and sometimes dizziness, when the congestion tilage at the base of the pharynx, the epiglottis, alters the inner ear’s balance mechanisms). This closes across the TRACHEA when swallowing and choreography of discomfort results from the inti- opens to allow the passage of air during inhalation mate integration of both structure and function of and exhalation. The small flap of tissue that hangs these senses. visibly at the back of the throat, the uvula, is an Limiting or avoiding exposure to loud noise extension of the soft palate. Doctors are uncertain could protect millions of people from hearing loss. of the uvula’s function; it may help keep swallowed Surgical and technological advances hold great food from entering the nasal passages. promise for restoring some kinds of hearing loss. The larynx is a sequence of connected cartilage Though some diminishment occurs naturally with structures that makes speech possible. Air passing aging, hearing, taste, and smell require minimal through the larynx causes these cartilages and the effort to maintain healthy function across the folds of tissue known as the VOCAL CORDS to spectrum of age. vibrate, generating sounds. The muscles of the throat help move the sound vibrations into the Traditions in Medical History mouth, which then forms them into noises and Before the advent of ANTIBIOTIC MEDICATIONS and words. Hearing further helps shape speech, pro- vaccines in the middle of the 20th century, many of viding instant auditory feedback. It is difficult, today’s commonplace ailments involving the ears, although not impossible, for someone who has nose, mouth, and throat were serious and even life- profound HEARING LOSS to speak clearly enough for threatening illnesses. Otitis media (middle ear others to understand. STROKE and neuromuscular infection), though less common or perhaps simply disorders such as PARKINSON’S DISEASE are among less frequently diagnosed 50 years ago than it is 6 The Ear, Nose, Mouth and Throat today, accounted for much childhood deafness and allowing tiny and fully programmable hearing aids frequently led to the complication of MASTOIDITIS, a that fit far enough within the auditory canal to be bacterial infection in the porous mastoid bone undetectable. Computerized adjustments accom- behind the ear that in turn often spread to the modate individual variations in tonal loss, helping brain, causing MENINGITIS or ENCEPHALITIS. Even TON- people screen out the kinds of noise interference SILLITIS frequently resulted in abscesses in children that have made the traditional HEARING AID a less and adults alike; tonsillectomy, in the absence of than ideal solution. The COCHLEAR IMPLANT, which adequate ANESTHESIA, was not an option. debuted in the 1980s, makes hearing possible for These infections had grim outlooks, leading to thousands of people with sensorineural hearing desperate treatments such as lancing (cutting open loss for whom hearing aids do not work. Hair-thin the ABSCESS or infection) and application of chemi- wires reside within the inner ear, receiving input cal disinfectants (for example, iodine and carbolic from outside the ear and conveying it directly to acid), which were the standard of treatment for the hair cells within the cochlea in much the same external wounds. The highly toxic nature of these way nerves do. External components collect and, approaches became a calculated risk in the fight using digital technology, interpret sound signals. for life. Lancing an abscess opened a direct chan- Other advances mark improvements in treat- nel into the bloodstream for the BACTERIA, virtually ments for ear infections, sinus infections, seasonal guaranteeing rapid death due to SEPTICEMIA (“blood allergies, and operations on structures of the oro- poisoning” or septic shock). The alternative, how- facial structures. Infants born with cleft deformi- ever, was suffocation from the swelling that closed ties today will grow up with little evidence of this off the throat. DIPHTHERIA and PERTUSSIS (whooping once disfiguring CONGENITAL ANOMALY, as advances COUGH), bacterial infections of the throat, in anesthesia and surgical techniques now permit remained the leading causes of childhood death surgeons to perform corrective procedures early in until the 1950s. Today antibiotics, surgery, and childhood and often in a single operation. Endo- routine childhood vaccinations have relegated scopic surgery reduces risk for numerous opera- these diseases, for the most part, to entries in text- tions on the nose, middle and inner ear, and books and encyclopedias. throat. New understandings of immune function and allergy response have led to new treatment Breakthrough Research and Treatment Advances approaches for chronic SINUSITIS and ALLERGIC RHINI- Some the most profound breakthroughs in oto- TIS. Current research continues to explore age- laryngology have been in the area of hearing loss. related changes in hearing, seeking approaches to Digital technology brings the computer to the ear, head off hearing loss. A

acoustic neuroma A noncancerous tumor of the NETIC RESONANCE IMAGING (MRI) can usually deter- eighth cranial (vestibulocochlear) NERVE. Acoustic mine the presence of an acoustic neuroma. neuromas typically grow over years to decades Treatment depends on the extent of symptoms and in some people cause no symptoms; doctors and the person’s overall health status. For many detect them incidentally. An acoustic neuroma people, especially those who have no symptoms, does not invade the surrounding tissues, though it the preferred treatment is watchful waiting can become life-threatening if it becomes large (observation and regular tests to monitor the enough to put pressure on the structures of the tumor’s growth). Surgery to remove the tumor or brainstem. Most often doctors do not know why RADIATION THERAPY to shrink the tumor is an option acoustic neuromas develop and classify them as when symptoms interfere with QUALITY OF LIFE or idiopathic (of unknown cause). Acoustic neuro- affect vital brainstem functions such as regulation mas sometimes occur with neurofibromatosis type of BREATHING and HEART RATE or motor control. 2, a rare hereditary disorder in which fibrous Each method has risks and benefits; individual growths develop in the CRANIAL NERVES and SPINAL health circumstances also influence the decision. NERVES. When it exists with no symptoms, acoustic Early symptoms of acoustic neuroma are vague neuroma does not interfere with the regular activ- and often perceived as normal consequences of ities of living or present any threat to health. For aging because the tumor is so slow growing it typ- most people who experience symptoms and ically appears in the later decades of life. Early undergo treatment, recovery is complete. Idio- symptoms include pathic acoustic neuromas do not return, though acoustic neuromas associated with neurofibro- • gradual loss of hearing, especially difficulty matosis type 2 often recur. Other than neurofibro- understanding speech, in one EAR matosis type 2, there are no known risk factors or preventive measures for acoustic neuroma. • TINNITUS (rushing or roaring sound) in one ear See also AGING, OTOLARYNGOLOGIC CHANGES THAT • balance disturbances such as dizziness or loss of OCCUR WITH; CENTRAL NERVOUS SYSTEM; MÉNIÈRE’S DIS- balance with motion EASE; SURGERY BENEFIT AND RISK ASSESSMENT; VESTIBU- LAR NEURONITIS. Advanced symptoms occur when the tumor’s size begins to encroach on nearby structures such adenoid hypertrophy Enlargement of the ADE- as the seventh cranial (facial) nerve. Such symp- NOIDS, structures of LYMPHOID TISSUE at the back of toms might include facial PAIN and disturbances of the NOSE. The purpose of the adenoids is to trap and facial expression. An AUDIOLOGIC ASSESSMENT helps destroy pathogens (disease-causing agents) in chil- determine the level of HEARING LOSS and whether it dren; by ADOLESCENCE the adenoids atrophy (shrink) affects one or both ears. Hearing loss in both ears and in adults are not distinguishable. When the suggests causes other than acoustic neuroma; it is adenoids swell, they can block the nasal passage. very rare that a person would have two tumors, This disrupts BREATHING and can affect the speech. one affecting each vestibulocochlear nerve. MAG- The eustachian tubes open near the adenoids; 7 8 The Ear, Nose, Mouth and Throat swollen and infected adenoids can trap BACTERIA in changes facilitate the ability to form words. By late the EUSTACHIAN TUBE and middle EAR. Adenoid childhood, many difficulties with speech begin to hypertrophy is a leading cause of OTITIS media (mid- resolve. Continued development of the brain’s dle ear INFECTION) in children. temporal lobe, which processes hearing and lan- Symptoms of adenoid hypertrophy include guage as well as taste and smell, expands and refines speech capabilities and sensory inter- • frequent ear infections pretations. Whereas a child may perceive a flavor • MOUTH breathing as “chocolate,” an adult will discern that same fla- • snoring, and, when hypertrophy is severe, vor in terms of multiple descriptors. OBSTRUCTIVE SLEEP APNEA Otolaryngologic Changes in Late Life • POSTNASAL DRIP In healthy adults, sensory perceptions, balance, • bad breath (HALITOSIS) and language capacity remain intact well into the sixth or seventh decade. Beyond this point, many Because the adenoids atrophy with physical people experience alterations in taste and smell, maturation, doctors prefer to treat occasional and particularly hearing. Health conditions that infections with appropriate ANTIBIOTIC MEDICATIONS. become more prevalent with age, such as STROKE ALLERGIC RHINITIS can also cause adenoid hypertro- and PARKINSON’S DISEASE, also affect sensory func- phy. When adenoid infections become chronic or tions as well as swallowing and speech. when the swelling does not retreat, doctors may Taste cells, located within taste buds, are the recommend adenoidectomy (surgery to remove only sensory cells that regenerate, and they do so the adenoids). Once the adenoids are removed, regularly throughout life. By midlife the rate of any related health problems go away. regeneration slows, and a person at age 60 has See also SURGERY BENEFIT AND RISK ASSESSMENT; about half as many taste cells as at age 30. The TONSILLITIS. more significant influence on the perception of taste, however, is the loss of olfactory receptors in aging, otolaryngologic changes that occur with the nose. The body does not replenish these spe- The natural changes that take place in the struc- cialized sensory cells, which detect thousands of tures and functions of the EAR, NOSE, THROAT, and odors in comparison to the four basic qualities the MOUTH as a person grows older. Age-related sense of taste detects. By age 70 there are about a changes manifest in late childhood, as facial struc- third as many olfactory receptors as at age 30. tures elongate, and again in the sixth decade and These changes influence a person’s interest in food beyond, as some diminishment of function, partic- and desire to eat, which commonly becomes a ularly sensory perception, develops. reason for inadequate nutrition and diet in the Otolaryngologic Changes in Late Childhood elderly. As well, the loss of teeth due to DENTAL Though the senses of hearing, taste, and smell are CARIES (cavities) and gum diseases such as PERI- fully developed by about one month of age, ODONTAL DISEASE, and decreased saliva production, changes in facial structure later in childhood alter diminish the ability to chew, further restricting some aspects of function. The rounded facial food choices. structures of the young child begin to change The clinical term for age-related HEARING LOSS is around age five or six and continue into early PRESBYCUSIS. The HAIR cells within the COCHLEA, ADOLESCENCE. The head elongates, expanding the which respond to the frequencies of the vibrations nasal and oral passages. The eustachian tubes that pass into the inner EAR, are extraordinarily lengthen and angle downward, improving their sensitive. By the sixth or seventh decade of life, ability to remain patent (open and clear of conges- the fibers of the hair cells, particularly those sensi- tion). The arch of the palate (roof of the mouth) tive to high frequency vibrations, break and expe- flattens, and the permanent TEETH come in. Con- rience other damage. This causes loss of the ability trol of the tongue, lips, and other muscular struc- to register sounds in those frequencies, which tures of the face and neck improves. These manifests as hearing loss. As these are the fre- audiologic assessment 9 quencies of normal conversation, the loss, though and the audiologist sits in a control booth. gradual, becomes apparent. Hearing aids that Common audiometric procedures include amplify sound waves in these frequencies can help restore the function of hearing. OTOSCLEROSIS • Pure-tone audiometry, which measures the (fusion of the auditory ossicles, the tiny bones of range of sound a person can hear. For this pro- the inner ear) and damage to tissues that results cedure, the audiologist produces tones at cer- from impaired blood circulation (caused by ATHER- tain frequencies and intensities, and the person OSCLEROSIS, for example) also diminish hearing. indicates whether he or she hears them. The See also BRAIN; EUSTACHIAN TUBE; GENERATIONAL audiologist tests each EAR separately. HEALTH-CARE PERSPECTIVES; NUTRITIONAL ASSESSMENT; • Conditioned-play audiometry and visual-rein- SPEECH DISORDERS; SWALLOWING DISORDERS. forcement audiometry, which adapt conven- tional audiometry to children. These methods audiologic assessment Tests to measure hearing use games and visual rewards to elicit responses ability and to determine the extent of HEARING LOSS. to the tones. An audiologic assessment consists of preliminary • Speech audiometry, which determines the low- screening and procedures to test specific dimen- est sound frequency and intensity at which a sions of hearing. A comprehensive audiologic person can hear and repeat two-syllable spoken assessment may take up to an hour to complete words (speech-reception threshold), and how though requires no preparation and involves no well the person can hear and repeat single-syl- discomfort. Basic screening for hearing ability and lable words spoken at a consistent intensity loss should begin in infancy (90 percent of new- (word recognition). borns born in hospitals in the United States are • Pure-tone BONE-conduction audiometry, which tested before discharge or at the first newborn well- delivers tones through a vibrating device placed care visit) and continue through life. Health experts against the bone near the ear. This bypasses the recommend routine screening tests for hearing loss outer and middle ear when there are conduc- in adults every five years, more frequently when tive obstructions present (such as OTITIS media there are risk factors, such as noise exposure. or compacted cerumen in the auditory canal). Preliminary Examination The first step in an audiologic assessment is a pre- The audiologist reports results in decibel (dB) of liminary examination in which the audiologist threshold (sound intensity) for 500 Hertz (Hz), examines the structures of the outer and middle 1,000 Hz, and 2,000 Hz, the frequencies of every- ears with an otoscope. This examination, called an day speech and activities. An audiogram summa- OTOSCOPY, helps detect structural anomalies as well rizes and presents this information for each ear in as mechanical impediments to sound conduction a graphic presentation. Any identified hearing loss (such as compacted CERUMEN in the auditory canal may require additional tests. or an infected or damaged TYMPANIC MEMBRANE). Other Hearing Tests The preliminary examination also includes a Sometimes health-care providers need further health history in which the audiologist asks ques- information to identify the nature and cause of tions about any existing hearing loss, risk factors hearing loss, particularly in infants and young chil- for hearing loss (including noise exposure), med- dren. Other tests for refined assessment include ications, and illnesses such as MEASLES and RUBELLA (German measles). • auditory evoked potentials, in which electrodes Audiometry attached to the head measure NERVE transmis- An audiologist conducts the procedures of audiom- sions in response to sound etry, a battery of tests that measure the ability to • auditory brainstem response, an auditory discern sounds at different frequencies (pitch) and evoked potential that specifically measures the intensities (volume). During the audiometric response of the eighth cranial nerve (vestibulo- examination the person sits in a soundproof booth cochlear or auditory nerve) 10 The Ear, Nose, Mouth and Throat

• otoacoustic emissions, which measure the often can correct conductive hearing loss through response of the cochlea to sound stimulation medical or surgical interventions. Sensorineural • acoustic immittance measures, which assess the hearing loss requires hearing aids or other solu- function of the middle ear: tions (such as a COCHLEAR IMPLANT) to improve hearing ability. Mild hearing loss (26 to 30 dB) is † tympanometry, to assess eardrum function the point at which a person is likely to benefit † acoustic reflex, to determine whether the from a HEARING AID. At the level of severe hearing ear responds to loud sounds loss (71 to 90 dB), a person is unable to under- † static acoustic impedance, to measure vol- stand speech without a hearing aid. Because hear- ume of air within the ear canal ing is essential for development of language and • balance assessment to determine vestibular communication skills, it is especially important to function/dysfunction provide immediate intervention for hearing loss in children. Understanding Results See also AGING, OTOLARYNGOLOGIC CHANGES THAT Audiologic assessment helps determine the appro- OCCUR WITH; NOISE EXPOSURE AND HEARING; OTOSCLE- priate therapeutic course for hearing loss. Doctors ROSIS; OTOTOXICITY. B

barotrauma Damage to the structures of the EAR during air travel. Some people benefit from nasal resulting from the ear’s inability to equalize pres- decongestant sprays that clear the nasal passages sure with abrupt and extreme changes in atmos- and eustachian tubes. Recreational divers are at pheric pressure. Such changes most often occur in greatest risk for inner ear barotrauma; pressure situations of sudden altitude change such as air changes are most drastic nearer the surface than travel or diving, though also may result from a deep in the water. sharp blow to the ear that forces a blast of air into See also BLISTER; EUSTACHIAN TUBE; HEMORRHAGE. the auditory canal. Any of the three parts of the ear—outer, middle, and inner—can experience benign paroxysmal positional vertigo (BPPV) A injury from barotrauma. disorder of the inner EAR in which certain posi- tions of the head cause sudden and severe, though • Outer ear barotrauma typically takes the form brief, episodes of VERTIGO (sensations of spinning of small, painful blisters and hemorrhages or motion). Many people experience symptoms along the walls of the auditory canal. upon awakening from sleep, as they roll from one • Middle ear barotrauma commonly includes a position to another or tilt their heads. Though the ruptured TYMPANIC MEMBRANE (eardrum). The vertigo episode typically lasts only a few minutes, pressure within the middle ear can become it can result in feelings of NAUSEA and dizziness as intense before the tympanic membrane gives well as balance disturbances, that continue for way, causing much PAIN. With rupture the pres- several hours. sure immediately equalizes, though hearing Doctors believe calcifications called otoconia, ability temporarily diminishes. small “stones” of calcium carbonate, cause BPPV. • Inner ear barotrauma causes sudden and usu- Otoconia occur naturally in the utricle and sac- ally significant VERTIGO (extreme dizziness and cule, two of the structures within the inner ear balance disturbances) and HEARING LOSS that can that are part of the vestibular system, the body’s be permanent. balance mechanisms. When otoconia escape from the utricle they can enter the semicircular canals, Most outer and middle ear barotrauma heals on where they collide with NERVE endings that send its own. Many ruptured eardrums heal naturally, positional messages to the BRAIN. These collisions though large or irregular tears require surgical overwhelm the messaging network. The otoconia repair (TYMPANOPLASTY). Inner ear barotrauma may tend to dissolve in the inner ear fluid over time. require surgery to repair damaged structures and About half the people who develop BPPV may result in permanent functional loss if the experience head trauma or serious INFECTION, such damage is extensive. as OTITIS (ear infection) or SINUSITIS (sinus infec- Preventive measures to reduce the likelihood of tion), before BPPV symptoms begin, leading doc- barotrauma include chewing gum, frequent swal- tors to believe that such assaults on the integrity lowing, and yawning during activities that involve of the inner ear jars the otoconia out of the changes in barometric pressure such as descending utricle.

11 12 The Ear, Nose, Mouth and Throat

Symptoms and Diagnostic Path perform to attempt to jolt the otoconia out of the The key symptom of BPPV is sudden, severe, and semicircular canals and at least into the vestibule limited episodes of vertigo without TINNITUS (ring- if not back into the utricle. These maneuvers suc- ing or rushing sound in the ears) or hearing ceed 70 to 90 percent of the time. impairment. The presence of either or both of the Rarely the otolaryngologist may recommend latter suggests another disorder. Symptoms tend to one of two operations for BPPV if it continues for occur with certain positions, though symptoms longer than a year without response to other can occur even when avoiding trigger positions. treatment: Between episodes, there are no symptoms. The pattern of symptoms is fairly conclusive, though • Posterior ampullar neurectomy severs a branch of the nerve that conveys motion signals from doctors typically conduct a comprehensive AUDIO- the utricle, ending its ability to send messages LOGIC ASSESSMENT to determine whether there is of motion to the brain. any HEARING LOSS with the expectation that results will be normal. • Posterior canal plugging seals the involved Other diagnostic procedures for BPPV may semicircular canal so the otoconia can no include longer float in its fluid.

• Dix-Hallpike test, positional test performed dur- Surgery nearly always ends BPPV; when it does ing physical examination; positive for BPPV not, further examination typically reveals compli- when it causes NYSTAGMUS (rapid and involun- cating factors or conditions that contribute to the tary darting movements of the eyes) or brings symptoms. Nearly everyone who develops BPPV on an episode of vertigo eventually recovers fully from the condition, with balance restored to normal. During the course of • caloric test, in which the doctor gently instills the condition and while undergoing treatment warm and then cold water into each ear; nor- with one of the maneuvers, doctors recommend mal response evokes vertigo and abnormal avoiding positions that may trigger symptoms, response, diagnostic of BBPV, evokes little or no especially tilting the head back, until BPPV symp- vertigo toms no longer occur. Once BPPV is resolved, it • electronystagmography, in which tiny electrodes generally does not recur. placed around the eyes detect the abnormal darting eye movements characteristic of vertigo Risk Factors and Preventive Measures Otoconia seem to naturally occur in many people, • imaging procedures such as COMPUTED TOMOGRA- causing problems only when they become lodged PHY (CT) SCAN or MAGNETIC RESONANCE IMAGING in vestibular structures such that they interfere (MRI) to rule out other possible causes for the with the movement of fluid that is essential for symptoms balance. It also appears that the body’s natural The combination of test results and history of processes dissolve and absorb the otoconia over symptoms helps the doctor distinguish BPPV from time, so most of these calcifications do not become other disorders that affect the vestibular system. large enough to obstruct the vestibular channels. Because doctors do not know what causes otoconia Treatment Options and Outlook to form, there are no known methods for prevent- For many people who have BPPV, the symptoms ing them. Prompt treatment for ear and sinus infec- simply go away over time, generally within sev- tions to reduce further trauma to the inner ear may eral months, as the inner ear fluid dissolves the help keep otoconia from causing symptoms. otoconia. Some people benefit from ANTIHISTAMINE See also ACOUSTIC NEUROMA; MÉNIÈRE’S DISEASE; MEDICATIONS or scopolamine, drugs that suppress OPERATION; SURGERY BENEFIT AND RISK ASSESSMENT; vestibular function, or antinausea medications. VESTIBULAR NEURONITIS. There are several positional treatments (among the most commonly used are the Epley maneuver blowing the nose The process of clearing mucus and the Semont maneuver) that some doctors and congestion from the nasal passages. Blowing broken nose 13 the NOSE generates significant pressure that can See also LARYNGITIS; PHARYNGITIS; SPEECH DISOR- force congestion into the SINUSES and eustachian DERS; SWALLING DISORDERS; VOCAL CORD NODULE; tubes. The best method is to blow through both VOCAL CORD POLYP. nostrils with a gentle and steady pressure with the head upright, pausing between blows to allow broken nose A FRACTURE of the nasal BONE, typi- gravity to help move congestion downward cally resulting from a direct blow. The NOSE is toward the nostrils. Short, hard bursts of blowing especially vulnerable to impact injuries, and the can activate a REFLEX action, which commonly nasal bones are the most commonly fractured on occurs after a SNEEZE, in which the nasal passages the face. Injury to the CARTILAGE and other tissues briefly swell and fill with mucus. Doctors believe of the nose often accompanies a nasal fracture; this reflex congestion occurs as a protective meas- these injuries are typically painful and result in ure to block harmful substances from entering the significant swelling and bruising. A fracture can nose, as sneezing is a mechanism for ejecting for- displace the bones and the cartilage, altering the eign matter from the nose. Applying unscented flow of air through the nose, and can result in lotion or aloe to the SKIN around the nostrils helps bleeding within the nasal passages. Ice applied to protect against irritation and INFLAMMATION from the area as soon as possible after the injury helps frequent nose blowing. contain the swelling. See also COLDS; EPISTAXIS; EUSTACHIAN TUBE; FOR- Most often the doctor will order X-rays of the EIGN OBJECTS IN THE EAR OR NOSE; NASAL VESTIBULITIS; face to confirm a nasal fracture as well as to deter- POSTNASAL DRIP; RHINORRHEA; SINUSITIS. mine whether other fractures, such as of the orbital bones around the eyes, also exist. The doc- Bogart-Bacall syndrome An overuse condition tor often can reduce (reposition) a simple nasal affecting the VOCAL CORDS and larynx. The key char- fracture by external manipulation done with local acteristic is a low, husky speaking voice (such as ANESTHESIA (closed reduction). Injury more exten- immortalized by famed actors Humphrey Bogart sive than a simple nasal fracture typically requires and Lauren Bacall, the namesakes of this condi- surgery to return the bones to their normal posi- tion). Speaking in the lower registers of pitch tions (open reduction). A protective splint worn strains the muscles of the larynx and the tissues of over the nose helps safeguard the fracture from the vocal cords, causing symptoms such as voice further injury while it heals. The bones become fatigue (inability to maintain volume when speak- set in about a week; the fracture heals fully in four ing), soreness or PAIN in the THROAT, and hoarseness to six weeks. Sometimes after HEALING is complete or raspiness when speaking. Treatment focuses on the structures of the nose remain out of align- improving breath control to speak when the lungs ment, which can affect BREATHING. Such complica- contain an adequate volume of air. Efficient tions require further medical assessment by an BREATHING during speech lessens the tension of the otolaryngologist or facial surgeon and may re- muscles in the throat that control the vocal cords quire further surgery. Most nasal fractures heal and flow of air. Some people, particularly women, uneventfully and have no long-term conse- whose voices are naturally in a higher register of quences. pitch than the voices of men, benefit from VOICE See also RHINOPLASTY; SEPTAL DEVIATION; SURGERY THERAPY to learn to speak at a higher pitch. BENEFIT AND RISK ASSESSMENT; X-RAY. C canker sore Ulcerous sores, also called aphthous Researchers have yet to identify any preventive ulcers, that develop inside the MOUTH. The typical measures to keep canker sores from developing. canker sore is round, with a slightly white center See also COLD SORE; NONSTEROIDAL ANTI-INFLAM- and a red rim. Sometimes a tingling or burning MATORY DRUGS (NSAIDS); NUTRITIONAL NEEDS. sensation precedes the eruption of the sore. A canker sore is painful and irritating for three to cauliflower ear A casual and descriptive term five days, then begins to heal and generally goes for an auricle (external EAR) damaged and away in about three weeks. Researchers do not deformed through trauma. Cauliflower ear is com- know what causes canker sores, though the ten- monly associated with repeated injury such as dency to develop canker sores appears to run in occurs with boxing. However, even a single blow families. Theories about the causes of canker sores to the ear significant enough to cause bleeding can include immune function abnormalities, nutri- result in deformity as the cartilaginous structure of tional deficiencies, and FOOD ALLERGIES. Some the external ear heals. CARTILAGE has no BLOOD women notice canker sores are more common supply of its own but instead draws nutrients from when they are menstruating. the blood supply of the SKIN. Any damage that dis- Treatment targets relieving the discomfort and rupts blood flow (such as injury that causes bleed- may include ing) causes cartilage tissue to die. Where cartilage dies, the structure it supports shrinks as the skin • frequently rinsing the mouth with a weak solu- around it heals, forming the characteristic irregu- tion of saltwater, hydrogen peroxide, diphen- larities of cauliflower ear. hydramine liquid, or milk of magnesia (rinse Prompt treatment of any injury to the external and spit, do not swallow any of these solutions) ear to minimize the interruption of blood flow and • applying milk of magnesia or a topical anes- control any INFECTION that may develop helps pre- thetic preparation for oral use directly to the vent deformity. Ear PIERCINGS into the upper ear canker sore with a cotton swab that become repeatedly infected or cause scarring also can result in cauliflower ear. OTOPLASTY (sur- • taking acetaminophen or a nonsteroidal anti- gery to alter the appearance of the auricle) can inflammatory DRUG (NSAID) for generalized improve the auricle’s appearance though may not pain relief be able to restore it to its natural structure. A key • taking a lysine supplement preventive measure is wearing appropriate head- • avoiding foods and seasonings that irritate the gear during activities that expose the outer ears to canker sores the risk of traumatic injury. See also ATHLETIC INJURIES; BLEEDING CONTROL; Prescription medications containing amlexanox LACERATIONS. (such as the brand-name product Aphthasol) may reduce INFLAMMATION and expedite HEALING when cerumen A soft waxy secretion, commonly sores are large or occur frequently. Such medica- called EAR wax, that the glands in the auditory tions come in topical and mouthrinse preparations. (ear) canal produce to help remove debris from 14 cleaning the ear 15 within the canal. Cerumen is usually yellowish rays, COMPUTED TOMOGRAPHY (CT) SCAN, and MAG- brown in color and its presence is normal, though NETIC RESONANCE IMAGING (MRI) of the head. Treat- many people attempt to clean it from the ears for ment requires overcoming any INFECTION with aesthetic reasons. Most health experts recommend ANTIBIOTIC MEDICATIONS and sometimes surgery to against using cotton swabs within the auditory remove the cholesteatoma and clean the area. canal for this purpose; it is possible for the swab to Treatment often restores hearing, though when compact the cerumen, push foreign objects deeper the cholesteatoma is large or has been present for into the ear, or damage the TYMPANIC MEMBRANE a long time the otolaryngologist may be unable to (eardrum). Tightly compacted cerumen can block repair the damage to the middle ear. Damage that sound waves from traveling through the auditory occurs within the inner ear often is permanent. canal, interfering with hearing, and create Prompt treatment of sinusitis or otitis minimizes unequal pressure, causing balance disturbances. It the risk for cholesteatomas to develop, though also can trap water in the auditory canal, allowing these growths are not preventable. Early diagnosis fungal or bacterial INFECTION to develop. Softening and treatment of cholesteatoma offers the best drops help loosen compacted cerumen so the ear’s opportunity to prevent permanent hearing loss natural mechanisms can push it out of the audi- and vestibular (inner ear) dysfunction. Untreated tory canal. When this does not work, removal cholesteatoma can result in profound hearing loss may require a health-care provider to perform EAR in the affected ear as well as MASTOIDITIS and LAVAGE or other techniques. MENINGITIS. For further discussion of cerumen within the See also ACOUSTIC NEUROMA; TYMPANOPLASTY; X-RAY. context of otolaryngologic structure and function, please see the overview section “The Ear, Nose, cleaning the ear Hygienic measures to keep the Mouth, and Throat.” ears clear of debris. For the most part, the ears are See also CLEANING THE EAR; FOREIGN OBJECTS IN THE self-cleaning. Tiny hairs (cilia) line the inside of EAR OR NOSE. the auditory canal, moving in wavelike motions to sweep particles of dust and pollen, as well as cholesteatoma A growth that develops within sloughed SKIN cells, to the outer edge of the EAR. the middle EAR. Most cholesteatomas develop as a CERUMEN, or ear wax, helps collect these particles consequence of frequent middle ear infections (OTI- for easy removal. Most people need only to wash TIS media) or chronically blocked eustachian tubes, the outer ear during regular bathing to remove such as by frequent SINUSITIS (sinus infection) or any accumulations of cerumen and debris. How- ALLERGIC RHINITIS. A cholesteatoma starts as an out- ever, many people feel the need to wipe the inside pouching of SKIN on or near the TYMPANIC MEMBRANE of the auditory canal with cotton swabs. Most (eardrum). SKIN cells accumulate inside the pouch, health-care providers recommend against this. causing it to enlarge and exert pressure against the Persistent swabbing of the auditory canal can lead tympanic membrane and auditory ossicles (tiny to compacted or impacted cerumen that blocks the bones of the middle ear). Over time the increased canal, interfering with hearing as well as prevent- pressure can destroy the auditory ossicles, causing ing the ear’s normal cleansing mechanisms from HEARING LOSS. A large cholesteatoma can also exert functioning. It also is possible for pieces of the cot- pressure inward against the inner ear, causing VER- ton swabbing to come off inside the canal, creating TIGO and balance disturbances. obstructions, and to perforate the TYMPANIC MEM- Symptoms of cholesteatoma include the sensa- BRANE with the tip of the swab. A doctor should tion of fullness in the affected ear, diminished evaluate any concerns about excess cerumen or hearing, dizziness and vertigo if there is pressure foreign objects in the ear. A health-care provider against the inner ear, and aching or dull PAIN can perform EAR LAVAGE when additional cleaning behind the ear. Symptoms are often positional and is necessary. A popular admonition among oto- may worsen at night, especially pain. Some people laryngologists is, “Never put anything smaller than experience a puslike drainage, often apparent on an elbow into the ear.” the pillow. The diagnostic path may include X- See also FOREIGN OBJECTS IN THE EAR OR NOSE. 16 The Ear, Nose, Mouth and Throat cleft palate/cleft palate and lip Congenital Treatment Options and Outlook anomalies in which the bones of the face that Nearly always surgery is the treatment of choice to form the roof of the MOUTH fail to close properly in close the cleft, for functional as well as aesthetic the early stages of embryonic development. These reasons. Surgeons generally prefer to do these structures originate as separate entities and, in the operations as early as the infant’s health permits, course of normal embryonic development, join typically between the ages of 3 and 18 months. together by 10 weeks of gestation. Cleft defects, Mild to moderate defects often require only a sin- known clinically as congenital craniofacial anom- gle operation. Extensive deformities may require alies, occur in varying degrees and combinations two or three operations done in stages, with fol- that may include separations of the hard palate, low-up speech therapy. Severe deformities that soft palate, upper gum, and upper lip. The most involve the upper gum and structure of the TEETH common presentation is isolated cleft palate (the may require ongoing orthodontic and dental defect involves only the roof of the mouth), or work, along with speech therapy, extending into cleft palate and lip (the defect extends from the ADOLESCENCE. The outlook following surgical repair roof of the mouth to the external lip). These is exceptional, with few complications for most anomalies are the fourth most common type of infants as they grow older. By adulthood there birth defect in the United States, affecting about 1 generally is little apparent evidence of the cleft or in 1,000 infants born each year. its repair. An intact palate is necessary for proper eating, swallowing, and speech. An infant with a cleft Risk Factors and Preventive Measures palate, and especially cleft palate and lip combina- Cleft palate and cleft lip appear to be random tion, often cannot suck well enough to obtain ade- occurrences though are common with certain quate nutrition. A complete cleft palate blends the genetic disorders such as DOWN SYNDROME. Some nasal and oral openings into a single chamber, studies suggest that these disorders are more com- which interferes with BREATHING. Craniofacial mon among infants of mothers who take certain anomalies also occur among the deformities of antiseizure medications or ANTIANXIETY MEDICATIONS numerous other congenital syndromes. There is a in the benzodiazepine family. Cleft palate and cleft particular correlation between isolated cleft palate lip are also more frequent among children of and other congenital defects, notably HEART anom- women who drink ALCOHOL and smoke cigarettes alies. Because of these correlations, doctors evalu- before and during pregnancy. Other studies show ate newborns with cleft palate defects for other that taking folic acid and vitamin B supplements congenital disorders. during pregnancy, which is a standard practice in PRENATAL CARE in the United States to reduce the Symptoms and Diagnostic Path likelihood of NEURAL TUBE DEFECTS, helps prevent Doctors detect most cleft palate defects shortly craniofacial clefts. When a woman gives birth to a after birth or in early childhood. Many clefts are child who has a cleft palate, any subsequent chil- visible or palpable (the doctor can feel the defect dren are more likely than normal to have the by running a finger along the roof of the infant’s same kind of disorder. mouth). A missing or bifid (two-part) uvula, the See also CONGENITAL ANOMALY, CONGENITAL HEART small flap of tissue that hangs from the soft palate DISEASE; FETAL ALCOHOL SYNDROME; OPERATION; SMOK- at the back of the THROAT, often though not always ING AND HEALTH; SURGERY BENEFIT AND RISK ASSESS- indicates a cleft palate. Doctors may not detect MENT; SWALLOWING DISORDERS; VACTERL; X-RAY. minor cleft palate disorders until the infant has trouble eating or does not appear to be gaining cochlea The organ of the inner EAR that converts weight. X-rays, COMPUTED TOMOGRAPHY (CT) SCAN, sound waves to NERVE impulses. Contained within and MAGNETIC RESONANCE IMAGING (MRI) are among the bony labyrinth, the cochlea resembles a snail the procedures that can confirm and define the shell. Thousands of specialized nerves, called HAIR extent of the defect. cells because of the fine fibers that project from cold sore 17 them, line the fluid-filled inner chamber of the though children who have been profoundly deaf cochlea. The membrane that contains the hair cells since birth (prelingual loss of hearing) typically do is the organ of Corti. Sound waves activate the hair not acquire hearing and speaking skills compara- cells, which convert the stimulation into nerve sig- ble to those of children who have normal hearing. nals. The nerve signals converge at the cochlear See also AUDIOLOGIC ASSESSMENT; SIGN LANGUAGE. nerve, which carries them to the vestibulocochlear nerve (eighth cranial nerve) for transport to the cold sore An eruption of the HERPES SIMPLEX BRAIN. The hair cells are very sensitive and vulnera- virus 1 (HSV1) in the form of a sore with a crusty ble to damage from excessive noise. The longest of scab, most commonly on the lips. Less commonly the hair cells are those that respond to sounds in HSV2, the variation of the herpes simplex VIRUS the decibel range of normal speech; because of their that causes GENITAL HERPES, causes sores around the length, they are the most vulnerable to such dam- MOUTH. Which variation of the herpes virus that is age. Hair cells also break off with aging. Damaged responsible does not matter. People sometimes cochlear hair cells do not regenerate. refer to cold sores as FEVER blisters because they For further discussion of the cochlea within the tend to appear with fever or during viral infections context of otolaryngologic structure and function, such as COLDS; doctors believe viral infections are please see the overview section “The Ear, Nose, among the triggers that activate HSV1. Hormonal Mouth, and Throat.” shifts during MENSTRUATION and exposure to the See also AGING, OTOLARYNGOLOGIC CHANGES THAT sun also appear to activate HSV1. OCCUR WITH; COCHLEAR IMPLANT; CRANIAL NERVES; HSV1 lies dormant in the nerve endings in the HEARING LOSS; PRESBYCUSIS. SKIN near the sites where cold sores have previ- ously occurred and, when activated, causes new cochlear implant An inner EAR prosthesis to sores to erupt. Many people experience itching or provide a degree of hearing ability for those who tingling at the site in the 24 to 36 hours before a have profound HEARING LOSS—greater than a 90 cold sore erupts. Doctors call this the prodrome decibel (dB) loss of hearing—in both ears and stage. When sores are present the herpes virus is receive no benefit from hearing aids. This tiny highly contagious and easily spread to other body electronic device receives incoming sound waves locations as well as to other people through con- and translates them into frequency impulses that tact or shared items such as drinking glasses, stimulate undamaged auditory nerve fibers that straws, and eating utensils. Rubbing the EYE after remain within the COCHLEA. The NERVE fibers con- finger contact with a cold sore can spread the vey the impulses to the BRAIN via the cochlear virus to the eye, where it can infect the CORNEA nerve. Though there are several designs of and cause scarring that can lead to blindness. Fre- cochlear implant, all feature external components quent HAND WASHING is an effective method for and internally implanted electrodes. restricting the spread of the virus. Because the nerve fibers within the cochlea are Treatment options are limited. Doctors may limited the impulses those fibers convey to the prescribe ANTIVIRAL MEDICATIONS for recurrent or brain are also limited, leaving “gaps” in speech. severe episodes of cold sores. These medications Over time, the person learns where these gaps are appear to shorten the course of the INFECTION from and learns to interpret many of them into intelligi- the usual 7 to 10 days to 3 to 5 days when taken ble units of language. It can take adults several or applied at the first indication (ideally in the years to develop proficient hearing skills. The level prodrome stage) of activation. Numerous topical of restored hearing generally correlates to the products to provide relief and moisturization are length of time between the onset of profound available over the counter, though these prepara- hearing loss and placement of the cochlear tions do not shorten the course of the infection. implant. Children who receive cochlear implants Some people have fewer cold sores when they typically learn or regain language understanding take lysine supplements. Cold sores typically heal and speech skills more quickly than adults, without scarring or other complications. 18 The Ear, Nose, Mouth and Throat

See also CANKER SORE; CORNEAL INJURY; OCULAR Acute Cough HERPES SIMPLEX. An acute cough generally accompanies a health condition of sudden onset such as an upper respi- cough The forceful expulsion of air through the ratory INFECTION (colds, flu, BRONCHITIS, PNEUMONIA), airway as a REFLEX designed to prevent matter, SINUSITIS (sinus infection), and PHARYNGITIS. An including mucus, from entering the LUNGS. Cough acute cough can be either productive or nonpro- can be a symptom of many health conditions, ductive though is usually productive because the from minor and temporary irritations of the phar- IMMUNE SYSTEM increases mucus production to help ynx (upper THROAT) and structures of the airways, rid the body of the PATHOGEN. ANTIBIOTIC MEDICA- such as those COLDS and allergens can cause, to TIONS are necessary to treat infections that are bac- serious and potentially life-threatening conditions terial. Viral infections typically run their course such as laryngeal CANCER, TUBERCULOSIS, CHRONIC and do not require medications except to relieve OBSTRUCTIVE PULMONARY DISEASE (COPD), and LUNG symptoms. In infections, coughs are often produc- CANCER. Cough also can signal a blockage of the tive, bringing up dead cells and other debris that airway, which is a medical emergency. Occasion- the body needs to clear from the airways. POST- ally cough is an undesired SIDE EFFECT of certain NASAL DRIP, which irritates the pharynx, is a key medications, notably the angiotensin-converting cause of coughs related to upper respiratory infec- enzyme (ACE) inhibitor medications prescribed to tions. treat HYPERTENSION (high BLOOD PRESSURE). Coughs fall into two major classifications: acute COVERING A COUGH and chronic. Acute cough comes on suddenly and Coughs can spread infections both through lasts less than three weeks; chronic cough contin- droplets in the air and through hand contact. ues for longer than three weeks. Within these Health experts recommend coughing into the classifications, cough may be productive (bring up crook of the arm rather covering the mouth with mucus or sputum) or nonproductive (typically a the hands. Frequent HAND WASHING also helps dry, hacking cough). Treatment depends on the reduce the spread of pathogens. kind of cough and focuses on first eliminating any underlying causes. There are two main classifica- Chronic Cough tions of cough medications: antitussive (suppresses A chronic cough may signal an underlying health the cough) and expectorant (thins the mucus). condition or may exist as a response to continued irritation, most commonly cigarette smoking. When Cough Is an Emergency Other common causes of chronic cough include A sudden cough, especially one that comes on when eating, may indicate that the person has • GASTROESOPHAGEAL REFLUX DISORDER (GERD), in aspirated (inhaled into the airway) a particle of which gastric acid from the stomach enters and food or other object. Do not allow someone who irritates the throat starts coughing while eating to leave the table • asthma and seasonal allergies unattended. Instead, ask the person to give a ver- bal answer to the question, “Are you okay?” If the • chronic sinusitis person cannot speak to answer the question, he or • pulmonary diseases such as chronic bronchitis, she likely has a blocked airway. COPD, and BRONCHIECTASIS

Aspiration is a medical emergency that Generally, eliminating the underlying cause of requires prompt response. Perform a chronic cough also eliminates the cough. A signifi- cant risk with smoker’s cough is that it develops so HEIMLICH MANEUVER immediately for a blocked airway. Call 911 for emergency gradually the smoker may not realize how often medical aid if the coughing or choking he or she coughs. The cough may exist as a continues. response to the irritation of smoking or may signal a serious health condition such as lung disease or croup 19 throat or lung cancer. A doctor should evaluate See also ALLERGIC RHINITIS; ALLERGY; PERTUSSIS; chronic cough in smokers on a regular basis to PULMONARY EMBOLISM; SMOKING AND HEALTH. monitor for more significant health problems. SMOKING CESSATION may end the cough; cough that croup A viral INFECTION of the upper respiratory continues longer than six months beyond smoking tract that produces a characteristic barking COUGH, cessation may indicate another health condition most commonly in children under age three. and requires a doctor’s assessment. Other symptoms include rapid BREATHING, a high- Treating Cough pitched noise with inhalation (stridor), and FEVER. In many children, the top of the airway at the Treatment focuses first on eliminating any under- back of the THROAT becomes swollen and con- lying reasons for cough. Antibiotic medications are gested, reducing the flow of air. The barking helpful only when there is a bacterial infection. cough results from air being forced through this The most effective cough suppressant medications narrowed passage as the body attempts to clear are those which contain DEXTROMETHORPHAN, ben- the congestion of the infection. Croup often fol- zonatate, or NARCOTICS such as codeine and lows COLDS and its symptoms tend to worsen at hydrocodone. Products containing benzonatate (a night. The most effective treatment is prompt non-narcotic) or narcotics require a doctor’s pre- exposure to moist air. Parents often find that as scription and are not generally appropriate for soon as they get the child buckled into the car seat chronic cough. Products containing dextromethor- for the late-night trip to the hospital emergency phan are numerous and available over the room, coughing lessens and breathing eases. The counter; extended-release products can provide cool night air helps open the airways. Often it relief for 10 to 12 hours per DOSE. brings the child relief to sit, wrapped in a blanket Expectorants help thin mucus and secretions so for warmth, with a parent in the night air for a the coughing mechanism can more easily bring few minutes. An alternative method is to turn on them out of the airways. Doctors do not agree on a hot shower and close the bathroom door so the whether expectorants are truly helpful, and there bathroom fills with steam, then sit with the child are few clinical research studies that have investi- in the steam. gated their effectiveness. The most common The child needs immediate medical attention expectorant in cough products sold in the United when symptoms States is guaifenesin. Manufacturers recommend drinking plenty of water when taking products • last longer than three days containing guaifenesin; some health experts believe increased water intake alone is adequate • include a fever higher than 102ºF to thin mucus. • suggest that the child is not getting enough Most cough products, both prescription and oxygen, such as CYANOSIS (blue lips) over the counter, combine ingredients, so it is • include excessive drooling important to read product labels carefully. Prod- ucts may include a cough suppressant and an Though frightening for parents, croup is most expectorant as well as a decongestant, an antihis- often self-limiting and has few complications. tamine, and other substances. Maintaining ade- Because croup is viral, ANTIBIOTIC MEDICATIONS do quate moisture in the air (as with a cool not bring about any improvement in symptoms. humidifier), drinking plenty of liquids, and avoid- And, being viral, croup is contagious, spread ing substances that irritate the throat and airways through droplets in the air from coughing as well are effective nonmedication methods for manag- as by hand contact. ing cough, especially chronic cough. See also BREATH SOUNDS; EPIGLOTTITIS; PERTUSSIS. D–E

deafness See HEARING LOSS. Many causes of HEARING LOSS arise as a result of damage to or dysfunction of the structures of the dental caries The clinical term for cavities, ero- outer and middle ear. The inner ear is entirely sions through the enamel of the TEETH that expose sealed from the external environment. Fluid the inner pulp and sometimes the NERVE of the bathes the delicate structures of the inner ear, tooth. A dentist is the health-care provider who helping protect them as well as isolate them from diagnoses and treats dental caries. Untreated den- external stimuli that could affect their functions. tal caries can lead to INFECTION of the tooth’s root Most disturbances of balance, often called vestibu- structure and potentially an ABSCESS of the nerve lar dysfunction, stem from problems with the canal, health conditions that require treatment inner ear. with ANTIBIOTIC MEDICATIONS as well as dental care. The accumulation of BACTERIA can contribute to COMMON CONDITIONS AFFECTING HALITOSIS (bad breath). A cavity that penetrates THE EAR, HEARING, AND BALANCE into the inner tooth often causes TOOTHACHE. ACOUSTIC NEUROMA BAROTRAUMA Appropriate ORAL HYGIENE and routine dental care CHOLESTEATOMA HEARING LOSS can help prevent dental caries. LABYRINTHITIS MÉNIÈRE’S DISEASE See also GINGIVITIS; PERIODONTAL DISEASE. MYRINGITIS OTITIS (INFECTION) OTOSCLEROSIS OTOTOXICITY ear The structures of the ear support the func- TINNITIS VERTIGO tions of hearing and balance. The ear has three divisions: For further discussion of the ear within the context of otolaryngologic structure and function, • The outer ear consists of the auricle (pinna) please see the overview section “The Ear, Nose, and auditory canal, structures that collect, Mouth, and Throat.” focus, and channel sound waves. See also AUDIOLOGIC ASSESSMENT; COCHLEAR • The middle ear consists of the auditory ossicles, IMPLANT; HEARING AID. three tiny bones that vibrate in sequence to focus and amplify sound. earache A generalized term for sensations of • The inner ear contains the COCHLEA, which con- pressure, discomfort, and PAIN in the area of the verts sound waves to NERVE impulses, and the EAR. Pain messages from other structures of the structures of the vestibular system that regulate head and neck, such as the NOSE and THROAT, also balance, the bony labyrinth, and the semicircu- sometimes appear to come from the ear (referred lar canals. pain). A common cause of earache in children is OTITIS media (INFECTION of the middle ear). The TYMPANIC MEMBRANE, or eardrum, separates Congestion in the eustachian tubes can cause the outer ear and the middle ear; the EUSTACHIAN fluid to accumulate between the TYMPANIC MEM- TUBE connects the middle ear with the THROAT to BRANE (eardrum) and the inner ear, creating equalize pressure on both sides of the eardrum. increased pressure, which causes pain. A child 20 epiglottitis 21 who is too young to speak may pull or tug at the There are two kinds of electrolarynx in com- ears. INFLAMMATION or infection of the auditory mon use: canal, commonly called swimmer’s ear, is a fre- quent cause of earache in older children and • The transcervical electrolarynx rests against the adults. Referred pain in adults may indicate health neck or the cheek and sends vibrations through conditions such as temporomandibular JOINT the muscles of the neck. Similar in appearance (TMJ) disorder, dental problems, SINUSITIS, TONSILLI- to a small flashlight, the transcervical electro- TIS, and PHARYNGITIS. larynx requires one hand to hold it in place and Treatment depends on the underlying cause of has a finger-activated switch. the earache. ANTIHISTAMINE MEDICATIONS can reduce • The intraoral electrolarynx uses a small tube, congestion due to allergic response. ANTIBIOTIC somewhat like a straw, that rests along the MEDICATIONS are necessary when the infection is inside of the cheek and sends vibrations directly bacterial. ANALGESIC MEDICATIONS to relieve pain, to the structures of the mouth. Some models such as acetaminophen and NONSTEROIDAL ANTI- mount components in a denture or orthodontic INFLAMMATORY DRUGS (NSAIDS), can ease the discom- device. An external amplifier and speaker proj- fort while HEALING takes place. Generally, treating ect the sound. the underlying reason for the pain causes the ear- ache to go away. Nearly all models of either kind operate on bat- See also BAROTRAUMA; EUSTACHIAN TUBE; TEMPORO- teries and are easy for most people to use. The MANDIBULAR DISORDERS. transcervical electrolarynx requires enough remaining healthy muscle tissue in the neck to eardrum See TYMPANIC MEMBRANE. transmit vibration. It is not a viable option when there is extensive tissue loss due to injury, such as ear lavage Gentle flushing of the outer EAR to trauma or BURNS, or surgery, such as for laryngeal remove accumulated CERUMEN or foreign objects. CANCER. The vibrating diaphragm of the electrolar- Typically a health-care provider performs ear ynx cannot produce the same intensity or range of lavage in the doctor’s office or a clinical setting, tone as the natural structures of the healthy lar- using a bulb syringe to instill warm water or other ynx, resulting in speech that tends to be machine- liquid and a basin to collect the solution as it like and difficult to understand. drains from the auditory canal (ear canal). Ear See also ESOPHAGEAL SPEECH; LIGAMENT; SMOKING lavage generally does not cause discomfort. People AND CANCER; TRACHEOSTOMY. who have middle or inner ear disorders, vestibular disorders, or MYRINGOTOMY tubes in place should epiglottitis A severe and rapidly progressing not undergo ear lavage. INFECTION of the epiglottis, a broad flap of tissue in See also CLEANING THE EAR; FOREIGN OBJECTS IN THE the back of the THROAT that closes when swallow- EAR OR NOSE. ing to prevent food from entering the TRACHEA (windpipe). Epiglottitis brings on severe swelling ear wax See CERUMEN. in the throat, obstructing the flow of air through the trachea. Death can occur in minutes if the electrolarynx A handheld device that makes swelling completely blocks the airway. speech possible for people who have undergone LARYNGECTOMY (surgical removal of the larynx) or Epiglottitis is a medical emergency that whose larynx is otherwise nonfunctional. The requires immediate hospital care. normal larynx consists of the VOCAL CORDS, CARTI- LAGE, MUSCLE, and ligaments. These tissues vibrate Although epiglottitis can affect people of any to generate the sounds the structures of the MOUTH age, it most commonly occurs in children ages convert into speech. The electrolarynx uses a rap- two to seven years. The main cause of epiglottitis idly moving diaphragm to generate vibrations that in children is bacterial infection with Haemophilus can help restore speaking ability. influenzae type b (Hib). In adults, epiglottis gener- 22 The Ear, Nose, Mouth and Throat ally follows bacterial PHARYNGITIS such as “strep” fingers, especially in children, and presence of for- throat. eign objects in the nasal passages), BREATHING dry Symptoms of the infection begin suddenly and and especially cold air, heavy sneezing, nasal worsen rapidly. Key symptoms include polyps, and external trauma such as a blow to the nose or face. Epistaxis may also indicate deviated • sore throat septum, which alters the flow of air through the • high FEVER (above 102°F) nostrils and exposes the nasal lining to chronic • gasping for breath and stridor (high-pitched irritation. sounds on inhalation) People who have bleeding disorders, regularly take NONSTEROIDAL ANTI-INFLAMMATORY DRUGS • profuse drooling (NSAIDS) including aspirin, or who have uncon- • desire to sit upright with the neck extended trolled HYPERTENSION (high BLOOD PRESSURE) are and the head tilted forward more likely to experience heavy epistaxis, though these circumstances do not usually cause the Treatment is immediate hospitalization for bleeding. Epistaxis is usually self-limiting (the administration of intravenous ANTIBIOTIC MEDICA- bleeding stops following initial treatment) and TIONS and often insertion of a breathing tube to does not require a doctor’s attention. maintain breathing until the swelling subsides. This A doctor should evaluate bleeding that persists course of treatment typically brings the infection after taking basic measures to stop the nosebleed. under control within 48 to 72 hours, though hospi- A heavy blood flow may require, with local anes- talization may be necessary for a week or longer. thetic, cauterization to seal the bleeding area or Prompt medical treatment of epiglottitis usually medicated packing (gauze strips, absorbent pled- leads to complete recovery. The routine IMMUNIZA- gets, or nasal tampons) placed into the area of the TION of infants and children with the Hib vaccine bleeding to hold continuous pressure against the has greatly contributed to the steady decrease in blood vessels. Doctors typically prescribe a course instances of this life-threatening infection. of oral ANTIBIOTIC MEDICATIONS when it is necessary See also BACTERIA; BREATH SOUNDS; TONSILLITIS. to place nasal packing, to safeguard against SINUSI- TIS (bacterial INFECTION of the SINUSES) or TOXIC epistaxis The clinical term for a bloody NOSE. The SHOCK SYNDROME (a serious systemic bacterial infec- inner nasal passages have a rich and plentiful sup- tion). The doctor must remove any nasal packing, ply of BLOOD vessels, and there are many causes typically three days after its placement. for epistaxis. During an episode of epistaxis, blood When extended treatment becomes necessary, may come from the nostrils or from the back of the doctor will also request blood tests to assess the nose and into the nasopharynx (back of the blood cell counts and CLOTTING FACTORS and may THROAT). Most people who have normal clotting do choose to admit the person to the hospital for not lose a significant amount of blood during an monitoring of the bleeding as well as the ability to epistaxis episode, even when bleeding appears maintain adequate breathing. Severe bleeding profuse. Blood loss often appears greater than it is may require BLOOD TRANSFUSION or infusions of because the blood mixes with nasal secretions. clotting factors. Rarely surgery is necessary to To slow or stop epistaxis: halt the bleeding, usually when the cause is external trauma or there are underlying health 1. Keep the head upright. conditions that prevent the body’s clotting mecha- 2. Apply firm pressure to both nostrils using the nisms from properly functioning. Most often epis- thumb and forefinger. taxis is a minor problem that quickly resolves, 3. Hold the pressure for at least 10 minutes with- though a doctor should evaluate recurring nose- out release. bleeds. See also BACTERIA; BLEEDING CONTROL; COAGULA- The most common causes of epistaxis are TION; NASAL POLYP; SEPTAL DEVIATION; THROMBOCY- injuries due to local irritation (notably insertion of TOPENIA. eustachian tube 23 esophageal speech A learned method to restore son then learns to force air from the trachea into verbal communication for people who have the esophagus instead of taking air in through the undergone LARYNGECTOMY (surgical removal of the mouth and forcing it into the esophagus. This is larynx, or voice box). When the THROAT is intact, somewhat more natural and many people find it air coming out of the LUNGS passes through the an easier technique to master. VOCAL CORDS and other structures of the larynx, See also ELECTROLARYNX. generating sound vibrations that travel to the MOUTH. The mouth then forms these vibrations eustachian tube An elongated, valvelike chan- into words. Laryngectomy removes the throat; air nel of tissue that connects the middle EAR and the instead enters and leaves the TRACHEA through a THROAT. The eustachian tube relaxes or constricts surgically created opening, or stoma. For to equalize the pressure between the middle ear esophageal speech, the person takes air into the and the external environment. The sensation of mouth and swallows it, which sends the air into the ears “popping” indicates air moving through the ESOPHAGUS (tube that carries food to the STOM- the eustachian tube. Congestion easily blocks the ACH). When the esophagus expels the air back into eustachian tube, particularly in children because the mouth, the force of the moving air generates their small, compact facial structure causes the sound in the form of a burp or belch. The mouth eustachian tubes to be nearly horizontal. In adults, then forms these bursts of air into words. The the eustachian tubes angle downward from the technique takes considerable practice; however, it ear to the throat, thwarting progression of fluid is possible produce a fairly natural voice, although from the throat to the middle ear. Blocked certain sounds may be difficult to form and under- eustachian tubes result in a feeling of fullness in stand. the ears and can set the stage for OTITIS media Tracheoesophageal speech is a variation of (INFECTION of the middle ear). esophageal speech in which the surgeon creates For further discussion of the eustachian tubes an opening between the trachea and the esopha- within the context of otolaryngologic structure gus at the point of the stoma, called a tracheo- and function, please see the overview section “The esophageal puncture, and inserts a small shunt Ear, Nose, Mouth, and Throat.” (connecting tube) with a one-way valve. The per- See also PHARYNGITIS. F foreign objects in the ear or nose Material that from the auditory canal, bringing the insect enters the EAR or NOSE. This is a common occur- with it. rence with young children, who tend to put objects into their noses and ears. Typically, the Do NOT put water into the ear canal in object is visible, though drainage or odor may sig- an attempt to remove an insect or other nal an undetected obstruction that is causing an foreign object. Water may cause the INFECTION. Attempts to retrieve or clear the object insect or object to swell, lodging it more can result in pushing it instead farther into the firmly into the ear canal. auditory canal or nasal passages; there is a risk with foreign objects in the nose of inhaling them When there is an object in the nose: into the airways or LUNGS. A health-care provider should assess and remove any foreign object that 1. Breathe through the mouth to avoid inhaling does not come out of the ear or nose with mini- the object or lodging it farther into the nasal mal effort, as well as any circumstance in which passages. an infection might exist. Particles of food and 2. Hold the clear nostril shut and breathe out objects such as paper wads attract moisture and through the blocked nostril. can swell, lodging more firmly in the ear or nose. To treat an insect in the ear: 3. Do not blow forcefully or insert anything into the nose to attempt to prod or pull the object 1. Lie on the side with the affected ear up. free. 2. Use an eyedropper to gently fill the auditory If these techniques are not effective, a health- canal with warm mineral oil or olive oil. care provider will need to remove the object. 3. Wait a few minutes for the oil to suffocate the Removal of the foreign object is nearly always a insect. complete remedy, unless there is a secondary 4. Often the insect will float to the top of the infection that requires further treatment. canal. If it does not, turn the head so the See also BLOWING THE NOSE; CLEANING THE EAR; EAR affected ear is down and allow the oil to drain LAVAGE.

24 G gag reflex A rapid and intense contraction of the ple who smoke cigarettes, or use smokeless pharyngeal muscles to expel material before it tobacco, and women who are pregnant have enters the THROAT. Touching the back of the soft increased susceptibility for gingivitis. palate activates the gag REFLEX in most people, See also CANKER SORE; DENTAL CARIES; ORAL causing a retching action. The gag reflex is more HYGIENE; SMOKING AND HEALTH. sensitive in some people, interfering with health examinations of the throat or dental examinations glossitis An INFLAMMATION of the tongue that is and treatment. HYPNOSIS and BIOFEEDBACK are two typically the result of irritation, viral or bacterial methods by which people can learn to delay or INFECTION, vitamin B deficiency, or ANEMIA. Glossitis minimize the gag reflex. Health conditions that may also develop as an opportunistic condition in can activate the gag reflex include severe PHARYN- people who have IMMUNE SYSTEM disorders. GITIS, EPIGLOTTITIS, and profuse POSTNASAL DRIP. Sprays to anesthetize the throat, such as to treat A rare though potentially life-threaten- relieve sore throat PAIN or for ENDOSCOPY proce- ing complication of glossitis is swelling dures, temporarily numb the nerves in the soft that causes the tongue to block the air- palate to subdue the gag reflex. A reduced or way. This requires emergency medical absent gag reflex, which can result in potentially attention. life-threatening ASPIRATION, may occur with STROKE and neurologic disorders such as CEREBRAL PALSY In glossitis, the tongue often hurts, has a charac- and PARKINSON’S DISEASE. teristic “beefy” appearance, and has a surface that is See also SWALLOWING DISORDERS. deep red and smooth. Swallowing and speaking may be difficult. Most glossitis responds to corticos- gingivitis INFLAMMATION of the gum tissue around teroid mouthrinses to reduce the inflammation. the TEETH. Most gingivitis is an early form of PERI- Mouthrinses with diphenhydramine may also ODONTAL DISEASE. Signs of gingivitis include painless bring relief. A bacterial infection requires treatment bleeding (spontaneous or with brushing) and with ANTIBIOTIC MEDICATIONS; a yeast infection swollen gums that may be bright red or shiny. requires treatment with ANTIFUNGAL MEDICATIONS. Some people develop painless sores or ulcerations Dietary changes or nutritional supplements are on the gums that indicate INFECTION. Though peo- necessary when vitamin B or iron deficiency is the ple may seek medical care because of the bleeding, cause. Appropriate treatment typically resolves the dentists and periodontists provide dental-based symptoms, and the tongue returns to normal. care for gingivitis. People who have DIABETES, peo- See also BACTERIA; HALITOSIS; ORAL HYGIENE.

25 H

hairy tongue The common term for the circum- LOCAL CAUSES SYSTEMIC CAUSES stance of overgrown filiform papillae on the OF HALITOSIS OF HALITOSIS tongue, a condition known clinically as lingua vil- poor ORAL HYGIENE PEPTIC ULCER DISEASE losa. Filiform papillae are long, resemble hairs, food stuck between TEETH GASTROESOPHAGEAL REFLUX and do not contain taste buds. Their purpose is to inadequate saliva DISORDER (GERD) help move food during chewing and swallowing. production certain cancers Normally the wear and tear of this function breaks TONSILLITIS, adenoiditis, SINUSITIS DIABETES them off, a process called desquamation. Various POSTNASAL DRIP LIVER disease circumstances inhibit desquamation, allowing the kidney disease filiform papillae to grow up to 10 times longer than normal. The overgrown filiform papillae then Treatment for underlying conditions often trap food debris and other substances that impart reduces or eliminates halitosis. When the source is color (such as coffee and tea), giving the charac- ineffective ORAL HYGIENE, improved brushing and teristic “colored hair” appearance of hairy tongue. flossing techniques can help clean food debris The causes of hairy tongue are numerous and from the MOUTH, which reduces the presence of include eating habits centered around soft foods, sulfur-producing bacteria. Medications can cause which do not scrape the tongue, and inadequate dry mouth and even leave unpleasant odors in the ORAL HYGIENE. mouth. Some people are predisposed to mouth From a medical perspective hairy tongue is conditions that support the presence of bacteria. harmless, though people in whom it develops tend Typically, a dentist treats halitosis related to oral to find it aesthetically displeasing and in some it hygiene, PERIODONTAL DISEASE, DENTAL CARIES, and tickles or irritates the soft palate during swallow- other dental conditions. A doctor may recommend ing. Brushing the tongue as a routine aspect of approaches to minimize halitosis that exists sec- oral hygiene, or using a tongue scraper, nearly ondary to other health conditions. Thyme, euca- always restores the desquamation process and lyptus, peppermint, and caraway are among the reduces the length of the filiform papillae. Hairy herbal remedies for halitosis. tongue is also slang for a bad hangover, probably See also GINGIVITIS; GLOSSITIS; HAIRY TONGUE. stemming from the correlation between chronic ALCOHOL abuse and poor oral hygiene habits. hearing aid An external device that amplifies See also HALITOSIS. sound to compensate for HEARING LOSS. A hearing aid incorporates a receiver (microphone) to pick halitosis The clinical term for bad breath. up sound waves, an amplifier to magnify the Halitosis can indicate numerous local or systemic sound waves, and a battery that powers the health conditions. Local halitosis occurs when an receiver and amplifier. Sound quality with a hear- abundance of BACTERIA that release sulfur as a waste ing aid is different from sound quality the natural byproduct colonize in the mouth. Systemic halitosis EAR perceives, and it takes time to become accus- occurs as a response to metabolic and chemical tomed to using hearing aids. Hearing aids cannot changes that the disease process causes in the body. restore normal hearing though they can increase 26 hearing aid 27 the range of frequency and pitch the ear can that is completely implanted (with the receiver detect through amplification and modulation. embedded in a pouch of tissue behind the ear) Hearing aids are most effective in sensorineural and one that has internal and external compo- hearing loss and can improve hearing in one ear nents (the receiver hangs behind the ear). or both ears. Implantable middle ear devices accommodate Kinds of Hearing Aids moderate to severe hearing loss and typically There are five kinds of hearing aids in common become an option when conventional external use today: hearing aids are ineffective. One other style, the body hearing aid, attaches • Completely in the canal (CIC) hearing aids are to the belt or fits within a pocket. About the size the smallest available and fit well into the audi- of a cellular phone, the body hearing aid can con- tory canal. They are barely visible when in tain a very large amplifier and comparable battery place. CIC hearing aids are most effective for to power it. Wires run from the body hearing aid mild to moderate hearing loss. People who unit to the ears. Though significantly less conven- have small auditory canals or limited manual ient than other styles of hearing aids, the body dexterity may not be able to use CIC hearing hearing aid can make limited HEALING possible for aids. CIC hearing aids allow the wearer to use people with profound hearing loss. the telephone without adaptive devices. BTE hearing aids can be analog or digital; CIC, • In the canal (ITC) hearing aids fit into the ITC, and ITE hearing aids and implantable middle start of the auditory canal. A bit larger than ear devices are digital. Analog units receive CIC hearing aids, ITC hearing aids are some- incoming sound waves and transmit them directly what noticeable when in place. They are easier to the amplifier; they make sound only louder. to handle than CIC hearing aids and also are Many people consider analog technology out- most effective for mild to moderate hearing dated, though it nonetheless provides improved loss. hearing across a broad spectrum of hearing loss. • In the ear (ITE) hearing aids fit at the opening Some analog hearing aids have manual volume of the auditory canal and are visible on the controls and others can accept a wider range of outer ear (auricle). The larger size of ITE hear- adjustment via computer programming. Digital ing aids give them the capacity to contain larger hearing aids convert incoming sound waves to amplifiers, extending the range of hearing loss binary signals that are much faster to process elec- they can accommodate. ITE hearing aids are tronically. Many digital models use computer effective for mild to moderately severe hearing microchips to allow a broad range of customized loss. adjustments that can filter out certain sounds • Behind the ear (BTE) hearing aids drape over (such as background noise) and independently the external ear (auricle), with the housing for enhance or subdue specific frequencies of sound. the electronics and battery behind the ear. A Digital hearing aids are programmable and provide thin tube runs from the BTE hearing aid over sounds closer to natural hearing, though they are the front of the auricle and into the auditory significantly more expensive than analog hearing canal. BTE hearing aids accommodate the aids. For many people cost is a framing factor in broadest range of hearing loss because they can choosing a hearing aid because most health insur- hold larger amplifiers and the larger batteries ance plans do not provide coverage for hearing necessary to provide power. aids. • Implantable middle ear devices are surgically Adjusting to Hearing Aids implanted in the middle ear. They attach to and Hearing aids cannot replace natural hearing or directly stimulate the auditory ossicles, the tiny restore the function of hearing to normal. Simplis- bones in the middle ear that amplify and trans- tically, hearing aids overstimulate the remaining mit sound to the inner ear. There are two varia- sensorineural structures of the inner ear so they tions of implantable middle ear devices, one can respond to sound signals. People using hear- 28 The Ear, Nose, Mouth and Throat ing aids must learn to consciously filter unneces- perceives tones between frequencies of 500 Hz sary noise and sounds. In natural hearing, the (very low) and 4,000 Hz (very high). AUDIOLOGIC structures of the ear and the BRAIN work in close ASSESSMENT measures the intensity of sound integration to receive, transmit, and interpret required to hear tones at certain levels within the sound waves. Hearing aids disrupt that integra- range of normal hearing and reports deviations in tion. Sound interpretation becomes a conscious decibels (dB) of loss. Hearing loss begins when the activity, though with practice it becomes auto- level of loss reaches 16 dB. Health experts classify matic. It takes concentration and focus to partici- hearing loss greater than 90 dB as profound; at pate in ordinary conversation, and many people this level the ability to hear the normal sounds of find the effort tiring even when they become pro- everyday activities is lost. Though profound hear- ficient at it. However, most people find the effort a ing loss can occur in only one ear, the term typi- reasonable trade-off for the return of some hear- cally refers to lack of hearing in both ears. Most ing ability. health-care providers use the American Speech- See also COCHLEAR IMPLANT; QUALITY OF LIFE; SIGN Language-Hearing Association (ASLHA) classifica- LANGUAGE. tion system for assessing the degree of hearing loss. hearing loss The diminishment of hearing abil- Hearing loss may result from damage (congeni- ity. Hearing loss can be temporary or permanent, tal or acquired) to the nerves and related struc- sudden or progressive, unilateral (affect only one tures of the inner ear that receive and transmit EAR) or bilateral (affect both ears), partial or pro- sound signals to the BRAIN; this is sensorineural found (total), congenital or acquired. There are hearing loss. It accounts for 90 percent of all hear- two kinds of hearing loss: sensorineural (NERVE) ing loss and is usually permanent. Hearing loss and conductive. About 28 million Americans have also may result from circumstances that prevent some level of hearing loss; 30 percent of them are sound waves from traveling through the outer over age 65 and 20 percent are under age 18. and middle ears; this is conductive hearing loss About 1 in 1,000 infants born in the United States and is often correctable with medications or sur- each year has a congenital hearing loss. gery. Temporary conductive hearing loss is com- Though there are numerous dimensions to mon, especially in children who have middle ear hearing, audiologists measure hearing loss in infections (OTITIS media). Congestion due to COLDS terms of sound intensity. Healthy human hearing and allergies is a common cause of temporary con-

DEGREE OF HEARING LOSS Classification Level of Loss Loss Threshold minimal (slight) 16 to 25 dB ticking of a watch, normal BREATHING mild 26 to 30 dB hum of electrical appliances moderate 31 to 50 dB falling rain, whispering, residential neighborhood noise, library, typical office, normal voice of a child moderately severe 51 to 70 dB normal conversation, washing machine, sewing machine, vacuum cleaner, birds, freeway traffic, normal television volume severe 71 to 90 dB telephone ringing, alarm clock, doorbell, city traffic, noisy restaurant, flushing toilet profound 91 db or greater hair dryer, small power tools, crying infant, shouting, police/fire/medical aid siren hearing loss 29 ductive hearing loss in adults. Compacted CERUMEN • perception that “everyone” mumbles when (ear wax) in the auditory canal and OTOSCLEROSIS speaking (fusion of the auditory ossicles, the tiny bones of • unable to hear the telephone or doorbell ring the middle ear) are common causes of treatable conductive hearing loss. Damage to the areas of • volume is past the halfway mark when listen- the brain that process hearing, speech, and lan- ing to television or radio guage can result in auditory processing disorders • easier to hear someone talking when looking in which, though the structures and mechanical directly at him or her functions of hearing may remain intact, the per- • restaurants are “too noisy” for conversation son cannot understand spoken words. Typically other language impairments, such as the abilities TINNITUS (sensation of roaring or buzzing sound to read and write, also exist with auditory process- in one ear or both ears) may be an early sign of ing disorders. sensorineural hearing loss. Children with unde- Hearing loss in children, whether congenital or tected hearing loss may fail to respond when spo- acquired, has significant developmental conse- ken to or to follow instructions, have difficulty in quences. It is now the standard of care in the school, seem to mumble or slur their words, or be United States to test newborns for hearing in the developmentally delayed especially in language first few weeks of life, with regular screening for skills. hearing difficulties at well child checks and rou- Diagnosing hearing loss begins with physical tine medical examinations through ADOLESCENCE. examination of the outer and middle ears to look The ability to hear forms the basis for understand- for obvious problems such as compacted cerumen, ing language. Early intervention to correct or inflamed or damaged TYMPANIC MEMBRANE accommodate hearing loss in prelingual children is (eardrum), and structural anomalies. An audio- essential for appropriate development and com- logic assessment then measures hearing response munication. A teacher’s voice in a classroom proj- to a variety of tests. If questions remain about the ects an intensity of about 70 dB; children with cause of the hearing loss, the doctor may request hearing loss at this level or greater will be unable COMPUTED TOMOGRAPHY (CT) SCAN or MAGNETIC RESO- to hear in school. NANCE IMAGING (MRI). The majority of hearing loss in adults is acquired. Excessive noise exposure and changes Treatment Options and Outlook related to aging (PRESBYCUSIS) are the most com- Medical or surgical treatments can restore most mon causes of acquired adult hearing loss. Hear- conductive hearing loss. Sensorineural hearing ing loss may also result from health conditions, loss requires interventions such as hearing aids, such as ACOUSTIC NEUROMA and MÉNIÈRE’S DISEASE, which amplify sound, or cochlear implants, which that interfere with the functions of hearing. directly stimulate nerve cells in the inner ear. Trauma, such as FRACTURE of the bones in the Hearing lost as a result of health conditions such face and head or BURNS that damage the external as acoustic neuroma often returns when the neu- ear, can cause hearing loss. Various medica- roma is removed. Accommodations for profound tions, including certain antibiotics, diuretics, anti- hearing loss include training in lip reading and hypertensives, high doses of aspirin, and SIGN LANGUAGE. CHEMOTHERAPY drugs, also can damage or destroy Hearing loss, however subtle, can significantly hearing. affect on a person’s ability to function in, and enjoy, everyday life. Even mild to moderate hearing loss Symptoms and Diagnostic Path removes many common sounds from daily experi- Sudden hearing loss in adults is typically obvious. ence. Early intervention and appropriate accom- Progressive hearing loss is often subtle and noticed modation can mitigate to the extent possible much more by others than the person experiencing the hearing loss. Hearing aids, though they cannot loss. Common indicators of diminishing hearing restore normal sound quality and hearing, make it ability include possible to participate in conversation and to hear 30 The Ear, Nose, Mouth and Throat many of the sounds that provide orientation to engine, chain saw, rock concert, sporting event in one’s personal environment. With accommodation, a stadium or arena) damages the HAIR cells within most people with hearing loss are able to fully par- the cochlea. The US Occupational Safety and ticipate in nearly all activities those who have nor- Health Administration (OSHA) establishes guide- mal hearing can experience. In the United States, lines and regulations for protection from exposure the Americans with Disabilities Act (ADA) requires to noise in the workplace. Other mechanisms that public facilities and most employers to provide rea- contribute to age-related hearing loss are likely sonable accommodations for people who have pro- genetic; research continues in this area as well. found hearing loss. Because numerous medications can damage the structures of the inner ear, it is important to Risk Factors and Preventive Measures always ask the doctor or pharmacist whether this The most significant risk factors for acquired hear- is a potential SIDE EFFECT. When it is, ask if there ing loss are age and noise exposure. Researchers are alternatives that are less risky for hearing. Ill- are exploring the processes of aging that cause nesses such as MEASLES, though now less common hearing loss, looking for ways to mitigate or elimi- because of vaccines, also can cause hearing loss. nate them. Limiting noise exposure appears to be RUBELLA (German measles) remains a leading one way to help reduce sensorineural hearing loss, cause of congenital hearing loss. even as a component of aging. Just 15 minutes of See also APHASIA; BAROTRAUMA; NOISE EXPOSURE exposure to noise at greater than 115 dB (jet AND HEARING; OTOTOXICITY; PRENATAL CARE. L

labyrinthitis An INFLAMMATION or INFECTION of the SEA are also necessary, at least until the inflamma- vestibular system, the body’s balance mechanism tion or infection is under control. within the inner EAR. The sudden onset of VERTIGO See also ACOUSTIC NEUROMA; BACTERIA; BENIGN (feeling of spinning) is the characteristic symptom. PAROXYSMAL POSITIONAL VERTIGO (BPPV); MÉNIÈRE’S Many people also experience transitory or tempo- DISEASE; VESTIBULAR NEURONITIS. rary hearing problems and TINNITUS (a ringing or roaring sound). When an infection is present, it laryngectomy Surgical removal of the larynx, can be viral or bacterial. Bacterial labyrinthitis typ- which includes the VOCAL CORDS and other struc- ically develops as a consequence of chronic OTITIS tures that produce sound for the function of media (middle ear infection). Doctors believe viral speech. Surgeons perform the majority of laryn- labyrinthitis develops when the bloodstream car- gectomies to treat CANCER due to cigarette smok- ries a VIRUS into the inner ear. Inflammatory ing. Laryngectomy results in the loss of the ability labyrinthitis may be an autoimmune condition; to speak. doctors are not certain of its etiology (origin and In laryngectomy, the surgeon makes an incision development). It is sometimes difficult to diagnose in the neck and removes the structures of the lar- and distinguish the kind of labyrinthitis because ynx, typically including the vocal cords and upper access to the inner ear is so limited. Often in bac- portion of the TRACHEA as well as surrounding MUS- terial labyrinthitis there are signs of infection CLE tissue to obtain a cancer-free margin. The around the TYMPANIC MEMBRANE (eardrum), or ESOPHAGUS, which carries food from the MOUTH to might be signs of infection elsewhere including the STOMACH, remains intact. In the OPERATION’s the mastoid (MASTOIDITIS) and less commonly, final stage the surgeon creates a permanent open- MENINGITIS. ing through the neck into the trachea, called a Bacterial labyrinthitis has potentially serious stoma, for BREATHING. complications, including destruction of the The operation takes five to eight hours for the labyrinth and COCHLEA, which results in permanent surgeon to perform, and most people stay in the and profound HEARING LOSS. It requires treatment hospital for 10 to 14 days following the surgery. with ANTIBIOTIC MEDICATIONS. Untreated bacterial Rehabilitation begins immediately and includes labyrinthitis also can extend into other infections instruction to care for the stoma as well as swal- such as mastoiditis and meningitis. Viral labyrinthi- lowing exercises. Many people also start to learn tis and inflammatory labyrinthitis generally do not ESOPHAGEAL SPEECH, though speech therapy is most leave lasting damage. Because distinguishing the extensive during outpatient rehabilitation follow- cause of labyrinthitis is sometimes difficult and the ing discharge from the hospital. The surgical consequences of untreated bacterial labyrinthitis wound heals completely in about six to eight can be severe, doctors typically prescribe antibiotics weeks. when the diagnosis is unclear, even though antibi- Occasionally doctors diagnose the cancer early otics will not treat viral labyrinthitis. Sometimes enough to permit a partial laryngectomy, in which medications to suppress vertigo and resulting NAU- the surgeon removes only the tumor and tissues

31 32 The Ear, Nose, Mouth and Throat in proximity to it. With partial laryngectomy the of the THROAT. A congenital laryngocele may not airway and often part of the vocal structures cause symptoms until environmental stressors that remain intact, so breathing and speech are normal create increased laryngeal pressure cause it to after recovery, though the quality and volume of enlarge. Musicians who play wind instruments are the voice may change. particularly vulnerable to laryngoceles, as are peo- See also CANCER RISK FACTORS; CANCER TREATMENT ple with OBSTRUCTIVE SLEEP APNEA. Occasionally a OPTIONS AND DECISIONS; ELECTROLARYNX; HEALING; laryngeal tumor causes a laryngocele. SMOKING AND CANCER; SMOKING AND HEALTH; SURGERY Hoarseness, a feeling that there is something BENEFIT AND RISK ASSESSMENT. caught in the throat, dry COUGH, and a soft lump vis- ible on the external throat are among the most laryngitis Irritation or INFLAMMATION of the lar- common symptoms. A large laryngocele can cause ynx (voice box) that results in hoarseness or loss stridor (a high-pitched noise with inhalation) and of voice. Most laryngitis is viral, though may difficulty swallowing. The diagnostic path typically accompany or follow a bacterial INFECTION such as includes COMPUTED TOMOGRAPHY (CT) SCAN or MAG- STREP THROAT. Laryngitis is also common in people NETIC RESONANCE IMAGING (MRI) of the throat and who strain their voices through loud singing, laryngoscopy (examining the inside of the throat yelling, and extended talking, and in people who through a lighted, flexible scope). Because a laryn- smoke or who work or live in environments that gocele presents a prime opportunity to trap BACTE- are smoky. Resting the voice by speaking softly RIA that cause INFECTION as well as the potential to (though not whispering as it further stresses the interfere with BREATHING and swallowing, the treat- tissues of the larynx) and sucking on hard candy ment of choice is an OPERATION through an incision or COUGH drops help soothe the irritated tissues. A in the neck to close or remove the laryngocele. cool-mist humidifier, especially when sleeping, See also BREATH SOUNDS; ENDOSCOPY; SWALLOWING helps reduce irritation. Most laryngitis goes away DISORDERS. within 10 to 14 days and does not need medical treatment. Bacterial laryngitis requires treatment leukoplakia Precancerous patches, or lesions, with an appropriate ANTIBIOTIC MEDICATIONS. inside the MOUTH. The patches are light-colored A doctor should evaluate laryngitis when: and most commonly form on the tongue and insides of the cheeks. Irritation to these tissues • hoarseness/discomfort last longer than 14 days over time, such as from all forms of tobacco use • an accompanying cough produces yellow or and poorly fitting dentures or dental bridges, green sputum causes leukoplakia to develop. In a type of leuko- • FEVER is greater than 101ºF plakia specific to people with HIV or AIDS, hairy leukoplakia, the patches look like white fuzz. Frequent or extended laryngitis might indicate Hairy leukoplakia often is one of the earliest signs the presence of VOCAL CORD NODULE, VOCAL CORD of HIV INFECTION. Leukoplakia may also affect the POLYP, or laryngeal CANCER. VULVA in women. Biopsy to examine the cells of See also BOGART-BACALL SYNDROME; COLDS; the patches confirms the diagnosis. In some peo- EPIGLOTTITIS; PHARYNGITIS; SMOKING AND HEALTH; TON- ple, removing the source of the irritation causes SILLITIS; VIRUS. the leukoplakia to go away. Often doctors prefer to remove the lesions surgically, which generally is laryngocele An air-filled bulge (herniation) that an office procedure with local ANESTHESIA. When develops within the tissues of the larynx (voice the irritation continues, or in the presence of box), often among the folds of the VOCAL CORDS. HIV/AIDS, leukoplakia may return. Laryngocele may be present at birth as a CONGENITAL See also ORAL HYGIENE; SMOKING AND CANCER; ANOMALY or develop later in life, often as a conse- SMOKING AND HEALTH; TOBACCO USE OTHER THAN quence of persistent pressure against the structures SMOKING. M

mastoiditis An INFECTION in the mastoid BONE the surgeon removes the entire mastoid bone. behind the EAR. Mastoiditis typically develops as a Most people recover fully following treatment, consequence of untreated or chronic OTITIS media though should have an AUDIOLOGIC ASSESSMENT to (middle ear infection) when BACTERIA migrate determine whether there is residual HEARING LOSS. from the middle ear to the adjacent mastoid bone. See also ABSCESS; SURGERY BENEFIT AND RISK The rather porous structure of the mastoid bone, ASSESSMENT. which is more a collection of small cavities than a solid structure, provides an ideal habitat for bacte- Ménière’s disease A disorder of the inner EAR ria. Untreated mastoiditis can spread to the nasal that results in balance and hearing disturbances. SINUSES as well as the MENINGES (membranes sur- Doctors do not know for certain what causes rounding the BRAIN and SPINAL CORD), causing bac- Ménière’s disease. There are numerous approaches terial MENINGITIS, and to the brain itself, causing to treating the condition’s symptoms though there ENCEPHALITIS. These infections are potentially fatal is no known cure for the disease. The most signifi- and require immediate medical treatment. Though cant consequence of Ménière’s disease is perma- mastoiditis was once a common cause of child- nent and progressive HEARING LOSS. About 2.5 hood death, it has become rare since the advent of million Americans have Ménière’s disease. ANTIBIOTIC MEDICATIONS. The disease is also called endolymphatic PAIN behind the ear, FEVER, and a recent episode hydrops, a reference to the dilation of the struc- of otitis media are the leading indications of acute ture in the inner ear called the membranous mastoiditis. The person may also have swelling labyrinth. Researchers believe the dilation signals and tenderness in the mastoid area, and the auri- an abnormal accumulation of fluid within the cle (external ear) may appear to stick out from the membranous labyrinth, though do not know what side of the head. Chronic mastoiditis may be sub- causes that accumulation. Current research sug- clinical; that is, the infection causes few overt gests that the dilation results in small tears that symptoms until it spreads beyond the mastoid or allow the fluid within the membranous labyrinth, destroys mastoid bone tissue. Diagnosis includes the endolymph, to mix with fluid outside the blood tests and cultures of any fluid in the ear to membranous labyrinth, the perilymph. The two look for signs of infection, and occasionally COM- fluids have different chemical compositions; some PUTED TOMOGRAPHY (CT) SCAN. In most cases of acute researchers believe changes in the electrolyte con- mastoiditis, antibiotic medications and occasion- tent that occur when the fluids mix cause vestibu- lar dysfunction that results in the specific ally MYRINGOTOMY (insertion of a small tube constellation of symptoms that define Ménière’s through the TYMPANIC MEMBRANE to allow fluid to drain from the middle ear) successfully eradicate disease. Continued or repeated dilation likely the infection. Chronic mastoiditis sometimes results in repeated tears and recurrent symptoms. requires surgery to open, drain, and occasionally Symptoms and Diagnostic Path remove portions of the mastoid structure. Severe Most otolaryngologists look for four cardinal, or mastoiditis may require mastoidectomy, in which defining, symptoms that occur with repeated 33 34 The Ear, Nose, Mouth and Throat episodes (recurrent symptoms) when distinguish- reduce the vertigo. When the vertigo is such that ing Ménière’s disease from other forms of vestibu- it prohibits the activities of living for an extended lar dysfunction. These are time, surgically cutting the vestibular NERVE ends the nerve messages the labyrinth sends to the • VERTIGO (sensation that the person or the envi- BRAIN yet preserves hearing. When vertigo is ronment is spinning or whirling), often with severe and hearing loss is complete, labyrinthec- NAUSEA and vomiting, and sometimes debilitat- tomy becomes a treatment option. The otolaryn- ing loss of balance gologist may surgically remove the labyrinth or • TINNITUS (rushing or roaring sound) in one ear, instill a DRUG, such as the antibiotic gentamicin, often worse during vertigo attacks into the inner ear that chemically destroys the • hearing loss in one ear that returns with the NERVE endings in the labyrinth. conclusion of each episode of symptoms The outlook for people who have Ménière’s though progressively worsens with multiple disease is variable and unpredictable. About 20 episodes percent have only one attack; typically there are few long-term consequences when this is the case, • sensation of fullness or congestion in one ear though some people experience mild permanent hearing loss. About 40 percent have recurrent Symptoms may last 20 minutes to several attacks, sometimes years apart, that medical treat- hours, and may fluctuate within, as well as vary ments effectively mitigate. Hearing loss tends to among, episodes. Doctors disagree on whether all worsen with each episode of symptoms, however, four symptoms must exist to constitute Ménière’s and can become profound (complete) in the disease, and whether symptoms other than vertigo affected ear. Another 20 percent have frequent must involve only one ear. Diagnosis is primarily and debilitating attacks that do not respond to by exclusion, with findings to rule out other medical treatments. For these people, Ménière’s vestibular dysfunctions and causes. Diagnostic disease significantly interferes with QUALITY OF LIFE tests and procedures often include and often produces moderate to severe hearing loss over a relatively short period of time. The • OTOSCOPY (visualization of the auditory canal and middle ear with a lighted instrument) remaining 20 percent of people who have Ménière’s disease fall along the continuum. • complete blood count (CBC) to look for signs of The most favorable improvement for those who infection or immune response have repeated episodes of symptoms is with ver- • COMPUTED TOMOGRAPHY (CT) SCAN or MAGNETIC tigo, which seems to go away roughly 10 years RESONANCE IMAGING (MRI) to rule out tumors and after diagnosis in about 70 percent of people. Doc- structural problems tors have no explanation for this; though medical • NEUROLOGIC EXAMINATION to rule out ACOUSTIC treatments can lessen the severity of vertigo dur- NEUROMA or disorders affecting the CRANIAL ing attacks, they do not appear to influence this NERVES 10-year resolution marker. • AUDIOLOGIC ASSESSMENT to evaluate hearing loss Risk Factors and Preventive Measures Findings that fail to support any other diagno- There are no known measures to prevent Ménière’s sis, in combination with the four cardinal symp- disease from developing in the first place. Lifestyle toms, point to a diagnosis of Ménière’s disease. factors appear to influence the return and severity of symptoms in many people who have the condi- Treatment Options and Outlook tion, though researchers have yet to establish Treatment largely focuses on relieving symptoms definitive connections. These factors include the and varies depending on the relief various efforts amount of sodium in the diet, fluid consumption provide. Common treatments may include antin- and balance, smoking, stress, and certain food trig- ausea medications, anticholinergic medications, gers. Many people find that restricting dietary ANTIHISTAMINE MEDICATIONS, and scopolamine to sodium and limiting fluid intake reduce the fre- myringotomy 35 quency of episodes because it helps prevent the please see the overview section “The Ear, Nose, accumulation of fluid throughout the body, includ- Mouth, and Throat.” ing in the inner ear. The doctor may also prescribe See also NOSE. a diuretic medication to further minimize fluid retention. Local and online support groups can pro- myringitis INFLAMMATION and irritation of the vide encouragement and anecdotal information TYMPANIC MEMBRANE (eardrum), usually as the about successful symptom management methods. result of a viral or bacterial INFECTION. The charac- See also BENIGN PAROXYSMAL POSITIONAL VERTIGO teristic symptom is the sudden onset of PAIN, (BPPV); LABYRINTHITIS; PERIPHERAL NERVOUS SYSTEM; sometimes severe. Many people also experience VESTIBULAR NEURONITIS. temporary HEARING LOSS in the affected EAR. In bul- lous myringitis (also called myringitis bullosa), mouth The facial structure that provides the sen- fluid-filled, blisterlike vesicles form on the tym- sory function of taste, performs the mechanics of panic membrane and cause intense pain. Some- speech, and prepares food for entry into the gas- times the doctor lances, or carefully punctures trointestinal system. The base of the skull estab- with a MYRINGOTOMY scalpel, the vesicles to release lishes the roof of the mouth; the mandible, or lower the fluid and relieve the pain. OTITIS media, infec- jaw, establishes the floor of the mouth. The muscu- tion of the middle ear, can extend to involve the lar cheeks help move food through the mouth dur- tympanic membrane. The pain associated with ing mastication (chewing) as well as shape the this form of myringitis often includes the sensa- mouth for forming the sounds of speech. The tion of pressure. Doctors typically prescribe ANTIBI- tongue contains most of the taste buds, specialized OTIC MEDICATIONS to treat the infection and papillae (or bumps) that contain the taste cells, ANALGESIC MEDICATIONS to relieve the pain. Appro- though some taste buds appear on the soft palate priate treatment resolves most myringitis in 10 to and back of the THROAT. The tongue also moves food 14 days, and any temporary hearing loss returns. through the mouth and then pushes it to the top of Occasionally myringitis causes the tympanic mem- the throat for swallowing. The tongue’s shape and brane to perforate, which may require further placement within the mouth help direct the flow of medical treatment. air and sound during speech. The TEETH function See also RUPTURED EARDRUM; TYMPANOPLASTY. primarily to tear and pulverize food and also pro- vide a solid structure for the tongue to push against myringotomy A surgical incision in the TYMPANIC during speech. SALIVARY GLANDS produce saliva, MEMBRANE (eardrum) to allow fluid in the middle which keeps the inside of the mouth wet and aids EAR to drain out. Fluid in the middle ear is a key in breaking down food to pass down the throat. symptom of OTITIS media (middle ear infection). The buildup of pressure causes considerable PAIN COMMON CONDITIONS AFFECTING and can cause the tympanic membrane to perfo- THE STRUCTURES OF THE MOUTH rate (tear or rupture). When otitis media is CANKER SORE CLEFT PALATE/CLEFT PALATE chronic or recurrent, the surgeon places a tympa- COLD SORE AND LIP nostomy tube in the incision to retain a pathway GLOSSITIS DENTAL CARIES for drainage to continue. The tube is very small HALITOSIS HAIRY TONGUE and generally falls out within several months, PERIODONTAL DISEASE LEUKOPLAKIA then the opening in the tympanic membrane SIALOLITHIASIS SIALADENITIS heals closed. The OPERATION is a same-day surgery SPEECH DISORDER SIALORRHEA done under general anesthetic, and usually takes TOOTHACHE THRUSH no longer than 20 minutes per ear. Recovery is rapid. For further discussion of the mouth within the See also MASTOIDITIS; RUPTURED EARDRUM; SURGERY context of otolaryngologic structure and function BENEFIT AND RISK ASSESSMENT; TYMPANOPLASTY. N

nasal polyp A noncancerous, fleshy growth ventable cause of HEARING LOSS and accounts for as within the interior NOSE. Polyps are outgrowths of much as 60 percent of impaired hearing ability. the mucous membrane and extend from the Several natural mechanisms attempt to protect membrane on a stemlike projection called a pedi- the EAR from damage due to loud noises. The tym- cle. Polyps have a rich BLOOD supply and bleed eas- panic REFLEX serves to stiffen the structures of the ily. Because of this and because there is a chance middle ear, reducing their ability to amplify for them to become cancerous over time, doctors sound. In response to a loud noise, two muscles in prefer to surgically remove them. Nasal polyps the middle ear reflexively contract. The tensor that form in the air passages and SINUSES can tympani MUSCLE pulls on the malleus, and the obstruct the flow of air, interfering with BREATHING. stapedius muscle pulls on the stapes—the first and Chronic irritation (such as from ALLERGIC RHINITIS) third bones, respectively, of the auditory ossicles. and INFECTION (such as SINUSITIS) seem to encourage The effect of this reflex straightens the ossicular the growth of polyps; treating the underlying con- chain (the sequence of the ossicles), restricting the ditions helps prevent polyps from recurring. Mul- movement of the bones and dampening their abil- tiple nasal polyps are common in people who ity to amplify and transfer sound waves. The ear have CYSTIC FIBROSIS. also may experience a temporary threshold shift See also INTESTINAL POLYP; VOCAL CORD POLYP. in response to sudden loud noises, such as gun- shots and fireworks. The burst of noise appears to nasal vestibulitis A bacterial INFECTION of the stun the HAIR cells, rendering them nonresponsive HAIR follicles around the base of the nostrils that to sound waves in the relevant frequency range. A results in INFLAMMATION and irritation of the tis- temporary threshold shift causes sounds to seem sues. Symptoms include redness, swelling, and muffled. As long as there is no further exposure to PAIN. Sometimes the tissue becomes raw and loud noise, the hair cells gradually return to func- bleeds. Nasal vestibulitis typically develops with tion and hearing returns to normal. However, extended sneezing and nose blowing such as continued or repeated exposure results in the occurs with COLDS and ALLERGIC RHINITIS. Treatment damage becoming permanent. with topical and occasionally oral ANTIBIOTIC MED- ICATIONS generally resolves the infection within 10 Measuring Sound Volume to 14 days, though symptoms should improve The unit of measure for sound volume is the deci- within 2 or 3 days. Most people experience com- bel (dB). The decibel system is logarithmic; each plete recovery with no residual complications, increase of 10 dB represents a 10-fold increase in though occasionally an ABSCESS develops that sound volume. A noise that measures 60 dB, such requires further medical care. as the sound of normal conversation, is 10 times See also BLOWING THE NOSE; SNEEZE. louder than a noise that measures 50 dB, such as the sound of falling rain. A clap of thunder, 120 noise exposure and hearing Excessive exposure dB, is 10 times louder than shouting directly into to noise can temporarily or permanently damage someone’s ear, 110 dB. A rock concert (130 dB) is hearing. Excessive noise exposure is the most pre- 10 times louder than thunder. 36 nose 37

Most hearing experts agree that exposure to movies on television or in theaters can exceed 120 sounds louder than 85 dB begins to damage the dB. Stereos played beyond the halfway point on hair cells in the COCHLEA, which activate the nerves the volume indicator, especially when using head- that translate sound waves into NERVE impulses. phones, quickly pass the 100 dB mark. Children’s Sounds at higher frequencies (2,000 Hz and noise-making toys can reach 110 dB to 140 dB. above) do more damage at the same decibel level than sounds at lower frequencies (under 800 Hz). Ear Protection Much of human conversation takes place between The most effective protection against noise expo- 2,000 Hz and 4,000 Hz. Damage to the hair cells sure is to avoid it. As this is not always practical or responsible for sound translation in this frequency possible, health experts recommend (and in the range is particularly devastating. workplace OSHA requires) wearing hearing pro- tection for exposure to sound at 90 dB for longer Noise Exposure than eight hours and for any exposure that Nearly everyone faces exposure to noise at levels exceeds 90 dB. There are two kinds of ear protec- capable of causing damage to the hair cells and tion: ear plugs and ear muffs. ultimately hearing loss. The sounds of city traffic, Ear plugs fit snugly into the auditory canal and a noisy restaurant, and a flushing toilet all meas- block sound waves from traveling to the middle ure in at about 85 dB. The US Occupational Safety and inner ear. They are available in various mate- and Health Administration (OSHA) has estab- rials and in different sizes and shapes; finding ear lished regulations limiting noise exposure in the plugs that fit properly and comfortably can take workplace. These regulations stipulate the amount some experimentation. Custom ear plugs are also of time an employee may experience noise expo- available, made specifically to fit an individual’s sure at certain decibel levels, prohibit exposure ears. A common complaint about ear plugs is that without protection to sounds over 115 dB, and they block so much sound that conversation is dif- prohibit exposure of any kind to sounds over 140 ficult. This dampening of the sound is called atten- dB. The OSHA Web site (www.osha.gov) publishes uation. Some designs of ear plugs contain current noise regulations and guidelines. channels that allow sounds at certain frequencies Musicians face the unique conundrum of need- to pass through. This improves the ability to hear ing to hear the full range of pitch while protecting and understand speech. Customized ear plugs for their hearing from its intensity, particularly in musicians can block selected sounds so the musi- group settings such as playing in a band or orches- cian can hear the tones and pitches necessary to tra. Yet musicians playing in a rock concert may play or sing. experience bursts of exposure at 150 dB, as loud Ear muffs fit over the ears with a strap that holds as a jet taking off, which causes permanent dam- them in place. They form a seal around the ear, age to the inner ear after only a minute or two. which prevents sound waves from traveling into The audience at a symphony concert experiences the auditory canal. As with ear plugs, there are var- a sound level of 110 dB, equivalent to a car horn, ious designs that offer different levels of effective- and peaks near 140 dB. Musicians playing the vio- ness and comfort. Ear muffs tend to muffle all lin, flute, and trombone face continued exposure sound, though ear muffs and ear plugs have com- to 110 dB or greater at frequencies above 2,000 parable ability to block noise, about 30 dB. People Hz, among the most damaging of exposures. Peo- exposed to noise louder than 100 dB to 110 dB ple who work in construction, steel working, min- should use both ear plugs and ear muffs, which in ing, air travel, manufacturing, and public safety combination can block up to about 45 dB. also face increased exposure to noise that threat- See also AUDIOMETRIC ASSESSMENT; COCHLEAR ens hearing. IMPLANT; HEARING AID; OCCUPATIONAL HEALTH AND Noise exposure exists in personal environments SAFETY. as well. Appliances such as hair dryers, blenders, coffee grinders, and even coffee makers can gener- nose The facial structure that serves as the organ ate 90 dB of sound or louder. The decibel level of of smell as well as the portal through which air 38 The Ear, Nose, Mouth and Throat enters and leaves the pulmonary system. Air mon cosmetic procedures that plastic surgeons enters the nose through the nostrils, passing perform. beneath the olfactory NERVE endings. Odor mole- cules activate the nerve endings, which convert COMMON CONDITIONS AFFECTING the stimulation into nerve signals the olfactory THE STRUCTURES OF THE NOSE nerve (first cranial nerve) transmit to the BRAIN. ALLERGIC RHINITIS BROKEN NOSE The air then swirls through the paranasal SINUSES, EPISTAXIS NASAL POLYP cavities within the bones that form the face. The NASAL VESTIBULITIS RHINORRHEA sinuses warm and moisturize the air, bringing it SEPTAL DEVIATION SEPTAL PERFORATION closer to the temperature and humidity of the SINUSITIS inner airways. Because it extends from the face, For further discussion of the nose within the the nose is vulnerable to traumatic injury and also context of otolaryngologic structure and function to environmental exposure hazards such as FROST- please see the overview section “The Ear, Nose, BITE and SUNBURN. Numerous dermatological con- Mouth, and Throat.” ditions can affect the outer nose, among them See also CRANIAL NERVES; MOUTH; OPERATION; ACNE, ROSACEA, SKIN CANCER, ACTINIC KERATOSIS, and THROAT. KERATOACANTHOMA. Surgery to alter the appearance of the nose, RHINOPLASTY, is one of the most com- nosebleed See EPISTAXIS. 0

obstructive sleep apnea A disorder in which case, WEIGHT LOSS AND WEIGHT MANAGEMENT are key blockage of the airways takes place during sleep to treatment. Lifestyle modifications, such as when the structures of the neck and THROAT relax, avoiding ALCOHOL or medications that cause sleepi- causing BREATHING to stop for periods of time. The ness (such as ANTIHISTAMINE MEDICATIONS or sleep characteristic symptoms are a repeated pattern aids), can improve the body’s ability to retain con- during sleep of loud, heavy snoring followed by a trol over the muscles of the throat. Some people period of silence followed by gasping or snorting benefit from surgery to remove excess tissue at and tiredness during waking hours. The snoring the back of the throat (uvulopalatopharyngo- indicates the structures of the throat are relaxing plasty). A continuous positive airway pressure and the passage for air is narrowing; the silence (CPAP) device to maintain pressure against the indicates relaxation has reached the point at airways and to keep them open is often an effec- which no air is getting through. The gasping or tive treatment when other approaches are not snorting is a reflexive reaction to the drop in the appropriate or not successful. blood’s oxygen level; it serves to restart breathing. See also SLEEP DISORDERS; WEIGHT LOSS AND WEIGHT The cycle results in continuous interruption of MANAGEMENT. sleep, leaving the person deprived of rest. The repeated episodes of oxygen deprivation can cause oral hygiene Self-care methods for maintaining or contribute to numerous health problems, health of the TEETH, gums, and MOUTH. Oral health- including HYPERTENSION (high BLOOD PRESSURE), care providers recommend brushing the teeth at ARRHYTHMIA (irregular heartbeat), PULMONARY least twice daily and flossing or using an interden- HYPERTENSION, and HEART FAILURE (reduced ability of tal device to clean between the teeth once daily. the HEART to pump BLOOD). People who snack throughout the day should Many people who have obstructive sleep apnea brush more frequently to clear away food debris are not aware that they do, though often their and BACTERIA that accumulate after eating. Appro- partners complain about their snoring. Often the priate oral hygiene helps maintain the health of first indication is the uncontrollable urge to fall the teeth, gums, and other structures of the asleep during the day, which may occur at danger- mouth and also reduces the risk of INFECTION in ous times, such as when driving. Frequent people who have tongue, lip, or other oral PIERC- headaches, lack of energy, and irritability are other INGS. Tooth decay and gum disease develop more symptoms. The diagnostic path includes a detailed rapidly in people who have diminished saliva pro- sleep questionnaire and careful physical examina- duction, have DIABETES, or who smoke. Further tion with a focus on the structures of the MOUTH preventive care measures include regular visits to and neck. The doctor may also request a sleep lab the dentist and dental hygienist for cleaning assessment, in which the person spends the night and examination to detect oral health problems under observation and with electronic monitoring such as GINGIVITIS, PERIODONTAL DISEASE, and oral to objectively assess the sleep experience. CANCER. About 40 percent of people who have obstruc- See also HALITOSIS; SJÖGREN’S SYNDROME; SMOKING tive sleep apnea have obesity. When this is the AND HEALTH; TOBACCO USE OTHER THAN SMOKING. 39 40 The Ear, Nose, Mouth and Throat otitis An INFLAMMATION of the EAR, typically the studies have failed to conclusively demonstrate a middle ear (otitis media) or the outer ear (otitis more rapid rate of recovery with antibiotics when externa). Otitis can affect the inner ear (otitis there is no effusion. The treatment guidelines interna), though more often doctors identify inner reflect the growing concern among health-care ear problems as LABYRINTHITIS and related condi- providers that inappropriate antibiotic use is tions. The most common cause of otitis is responsible for an alarming increase in the strains INFECTION. Otitis media often follows a cold or of bacteria that are resistant to antibiotics. The other upper respiratory infection. Otitis can be guidelines suggest acute (comes on suddenly) or chronic (lingers at a subclinical level or recurs). • focusing on pain relief by giving the child appropriate doses of ibuprofen or acetamino- Otitis Media phen Otitis media is one of the most frequent reasons • allowing 48 to 72 hours for the child’s natural parents take their children to see the doctor. immune response to bring the infection and Young children are particularly susceptible to otitis inflammation under control media because the eustachian tubes are nearly • prescribing an antibiotic as the first line of horizontal until the child’s facial structure begins treatment only in children under six months of to elongate at about age six or seven. The change age or who have a history of recurrent otitis in facial structure pulls the eustachian tubes into media more angled positions. The purpose of the • prescribing amoxicillin as the antibiotic of first EUSTACHIAN TUBE is to maintain pressure equilib- rium between the middle ear and the external choice unless there is a clinical reason (such as environment. Inequities in pressure allow fluid to sensitivity or known resistance) to prescribe a accumulate in the middle ear, which inflames the different antibiotic tissues and provides fertile ground for bacterial Acute otitis media generally clears up in 10 to growth. The eustachian tubes in a child are also 14 days. Chronic or recurrent otitis media may prone to becoming congested, which can feed require a more extended course of antibiotic ther- fluid and BACTERIA into the middle ear. apy or MYRINGOTOMY with placement of tympanos- Symptoms of otitis media are primarily PAIN and tomy tubes. Adenoidectomy (surgery to remove FEVER. Very young children often tug at the the ADENOIDS) may be necessary when other meas- affected ear, are fussy and sleep fitfully, and may ures fail to eradicate the infection. Many children not want to nurse or bottle-feed. Older children experience temporary HEARING LOSS with otitis can say that their ears hurt or may complain of media. Repeated infections may cause permanent HEADACHE. When there is a ruptured eardrum, hearing damage. there is usually pus-filled or blood-tinged drainage from the ear. Pain lessens when the eardrum gives Otitis Externa way because this releases the pressure. It is not A common name for otitis externa is swimmer’s possible for a parent to determine whether a child ear. Infections of the outer ear are most common has an ear infection; the doctor must examine the in the summer months when water activities, ear with an otoscope. The doctor looks for signs of especially outdoors, are prevalent. Otitis externa effusion, the collection of fluid behind the TYM- develops when water and bacteria become trapped PANIC MEMBRANE (eardrum). When effusion is pres- in the auditory canal. Sometimes excessive CERU- ent, the preferred treatment is an oral antibiotic MEN production contributes to the situation. Treat- medication. ment depends on the cause of the inflammation The American Academy of Pediatrics issued and irritation. Taking care to thoroughly dry the treatment guidelines in 2004 that emphasize auditory canals after bathing, showering, or swim- selective use of ANTIBIOTIC MEDICATIONS for acute ming can help prevent otitis externa. otitis media without effusion. Clinical research See also ANTIBIOTIC RESISTANCE; OTORRHEA. otoscopy 41 otoplasty Surgery to alter the appearance of the responsible. Other conditions such as DERMATITIS of auricle (external EAR). Otoplasty can be cosmetic the auditory canal may improve with topical COR- (to improve appearance) or restorative (to treat TICOSTEROID MEDICATIONS. When the drainage is congenital deformities or those that result from cerumen, gently rinsing the ears with warm water trauma and BURNS). The auricle is primarily CARTI- during bathing helps remove the excess. LAGE and SKIN; the cartilage gives the external ear See also CLEANING THE EAR; FOREIGN OBJECTS IN THE its shape and position on the side of the head. EAR OR NOSE. Numerous causes account for abnormalities. Oto- plasty can remodel the cartilage to alter the size, otosclerosis Abnormal growth of BONE tissue shape, and placement of the auricle and even around the auditory ossicles in the middle EAR, reconstruct an auricle that is missing or severely causing one or more of the ossicles to become deformed. locked into place or fused against the other ossi- See also CAULIFLOWER EAR; PIERCINGS; PLASTIC cles. Most commonly affected is the stapes (stir- SURGERY. rup), the final of the three auditory ossicles in the sequence of sound wave amplification and trans- otorrhea A discharge from the EAR. Most com- mittal. Conductive HEARING LOSS, which is the pri- monly otorrhea signals the presence of OTITIS, an mary symptom of otosclerosis, occurs as INFECTION of the outer ear (otitis externa) or the movement of the auditory ossicles becomes middle ear (otitis media). Otorrhea is normal after increasingly limited. Occasionally otosclerosis MYRINGOTOMY and placement of tympanostomy involves the COCHLEA, causing sensorineural hear- tubes, as the purpose of these procedures is to ing loss and sometimes vestibular dysfunction drain accumulated fluid from the middle ear. such as balance disturbances and VERTIGO. Drainage that is yellowish green typically contains An AUDIOLOGIC ASSESSMENT identifies the hearing pus. Red-tinged discharge contains BLOOD. Either loss. The otolaryngologist may request a COMPUTED of these may indicate otitis media with a perfo- TOMOGRAPHY (CT) SCAN or MAGNETIC RESONANCE IMAG- rated TYMPANIC MEMBRANE (RUPTURED EARDRUM). ING (MRI) to visualize the structures of the inner Drainage that is yellowish brown and thick may ear and to confirm the diagnosis. Surgical treat- be excessive CERUMEN, often in response to the ments often can restore conductive hearing loss to ear’s attempts to clear matter from the auditory near normal hearing. An OPERATION to remove the canal or to soothe irritated tissues. immobilized ossicle and replace it with a pros- thetic ossicle can permanently restore hearing in Bright bleeding or drainage from the most people. Surgery is less successful in restoring ear that is watery and clear requires hearing loss due to cochlear otosclerosis, though a emergency medical attention. HEARING AID often can improve hearing. See also SURGERY BENEFIT AND RISK ASSESSMENT; Trauma to the head, such as from a blow or a TINNITUS. fall, can cause outright bleeding from the ear and may indicate a BONE FRACTURE. Trauma also can otoscopy A basic visual examination of the cause CEREBROSPINAL FLUID to leak into the middle outer and middle EAR using an otoscope, a hand- ear and drain from the outer ear when a perfora- held, lighted device with a magnifying lens. The tion allows the fluid to pass from the middle ear to otoscope has cone-shaped tips in varying sizes that the outer ear or from the NOSE (RHINORRHEA) when fit into the start of the auditory canal. With an the tympanic membrane is intact. Drainage of otoscope, the doctor can examine the auditory cerebrospinal fluid also sometimes occurs follow- canal for injury, INFLAMMATION, INFECTION (OTITIS ing surgery to remove an ACOUSTIC NEUROMA; in externa) blockages such as foreign objects or com- any other circumstance it may indicate MENINGITIS. pacted CERUMEN, and structural deformities. The Treatment targets the underlying cause. ANTIBI- doctor also can visualize the outer surface of the OTIC MEDICATIONS are necessary when otitis is TYMPANIC MEMBRANE for inflammation, infection, 42 The Ear, Nose, Mouth and Throat

OTOTOXIC MEDICATIONS Medications Commonly Prescribed to Treat Ototoxic Effects ANGIOTENSIN-CONVERTING ENZYME HYPERTENSION TINNITUS, HEARING LOSS (ACE) inhibitors: enalapril, usually temporary, reversible when lisinopril, ramipril, quinapril, medication stopped trandolapril aminoglycoside antibiotics: in intravenous form: hearing loss, balance disturbances amikacin, gentamicin, kantamycin, Acinetobacter, Enterobacter, Pseudomonas, some degree of loss is often neomycin, streptomycin. and Mycobacter infections permanent; risk increases when also tobramycin in topical form: ear drops following taking any other medications with myringotomy ototoxic effects aspirin (salicylic acid) PAIN, INFLAMMATION, mild anticoagulant tinnitus, hearing loss with high doses, balance disturbances usually temporary, reversible when medication stopped platinum-derived CHEMOTHERAPY certain cancers (BLADDER, LUNG, ovarian moderate to severe hearing loss agents: carboplatin, cisplatin STOMACH, testicular) usually permanent loop diuretics: bumetanide, hypertension, congestive heart failure, tinnitus, hearing loss usually temporary, ethacrynic acid, furosemide, KIDNEY disease reversible when medication stopped torsemide macrolide antibiotics: Helicobacter pylori infection (PEPTIC hearing loss, sometimes severe azythromycin, clarithromycin, ULCER DISEASE), Legionella PNEUMONIA usually temporary, reversible when erythromycin (LEGIONNAIRES’ DISEASE), alternative when medication stopped when there are allergies to penicillin and cephalosporin antibiotics

NONSTEROIDAL ANTI-INFLAMMATORY pain, inflammation, arthritis tinnitus, mild to moderate hearing loss, DRUGS (NSAIDS): balance disturbances over the counter (OTC): ibuprofen, usually temporary, reversible when naproxen sodium, ketoprofen medication stopped prescription: oxaprozin, diclofenic, etodolac, meloxicam, celecoxib, bismuth subsalicylate (for example, gastrointestinal upset, DIARRHEA tinnitus, mild to moderate hearing loss, Pepto-Bismol) balance disturbances usually temporary, reversible when medication stopped quinine, chloroquine, quinidine MALARIA, arrhythmias, leg cramps tinnitus, mild to moderate hearing loss, balance disturbances, vertigo usually temporary, reversible when medication stopped ototoxicity 43 perforation, deformities, movement, and signs of • TINNITUS (sensation of ringing or rushing sound) increased pressure in the middle ear such as • indications of HEARING LOSS, such as difficulty bulging or fluid that suggests otitis media (middle understanding conversation or being unable to ear infection). Otoscopy is the primary diagnostic hear the telephone ring procedure for many conditions affecting the outer • balance disturbances and dizziness ear, and the first step of the diagnostic path for conditions affecting the middle ear. Otoscopy can- • VERTIGO (sensation of spinning) not determine hearing ability or HEARING LOSS. Report any of these symptoms to the doctor See also AUDIOLOGIC ASSESSMENT; MYRINGITIS; RUP- immediately, though do not stop taking any med- TURED EARDRUM. ications until discussing the circumstances with him or her. Most ototoxic medications appear to ototoxicity A medication SIDE EFFECT that results act on the delicate HAIR cells in the COCHLEA, stun- in damage to the functions and structures of the ning or destroying their ability to translate sound EAR and hearing. The damage can be temporary, in waves into NERVE signals. Ototoxicity is most dev- which case symptoms recede and hearing returns astating when it affects high-frequency hearing, when the person stops taking the medication, or the range of normal conversation. permanent. Numerous medications can be oto- Numerous industrial chemicals are also oto- toxic at therapeutic doses, making it prudent to toxic. They include butyl nitrite, carbon disulfide, weigh this potential consequence against the hexane, manganese, lead, mercury, styrene, and anticipated benefits of the medication. Often med- toluene. Hearing loss resulting from exposure to ication options are available that can achieve the these chemicals is often permanent. desired therapeutic effect without the risk for oto- See also AUDIOLOGIC ASSESSMENT; NOISE EXPOSURE toxicity. AND HEARING; OCCUPATIONAL HEALTH AND SAFETY; TOXIC Symptoms of ototoxicity include OPTIC NEUROPATHY. P periodontal disease Inflammatory and some- marily an infection among children, peritonsillar times infectious damage to the gums. Periodontal ABSCESS is most common among adults in early disease causes gum tissue to recede from the midlife. Doctors are uncertain what causes a peri- TEETH, which allows teeth to loosen. It also exposes tonsillar abscess to develop, though it will often the less protected area of the tooth to BACTERIA follow another infection such as tonsillitis, PHARYN- that cause tooth decay, resulting in DENTAL CARIES GITIS or mononucleosis. (cavities) and potential INFECTION such as ABSCESS Symptoms emerge suddenly. They include of the root canal. Periodontal disease is the leading cause of tooth loss in adults. Dental care providers • severe and usually one-sided PAIN in the throat estimate that up to 60 percent of American adults • pain in the EAR on the opposite side from the have some degree of periodontal disease. abscess with swallowing Symptoms of periodontal disease include • FEVER • a whispery, hoarse voice • painless bleeding, especially when brushing the teeth • neck stiffness and sometimes swelling on the front of the neck • swollen, shiny, or red gums • difficulty swallowing • gaps between the gums and the teeth • inability to fully open the mouth (called tris- • loose teeth mus) • HALITOSIS (bad breath) that does not improve with brushing or mouthwash Symptoms and physical examination typically make the diagnosis, though the doctor may per- Dentists provide diagnosis and treatment for form a laryngoscopy to more closely examine the periodontal disease. Appropriate ORAL HYGIENE can throat. After swabbing the peritonsillar area for prevent most periodontal disease; identifying peri- culture, treatment with intravenous ANTIBIOTIC odontal disease early allows opportunity for thera- MEDICATIONS begins. The person remains hospital- peutic interventions to thwart permanent damage. ized until the swelling goes down and the pain Some health experts believe there are connections abates, at which point antibiotic therapy shifts to between the body’s inflammatory response, peri- oral doses for the remainder of treatment at home. odontal disease, and other health conditions such When the abscess is large or has the potential to as ATHEROSCLEROSIS and CORONARY ARTERY DISEASE interfere with BREATHING, the doctor may choose to (CAD). surgically open and drain it (under anesthesia). See also GINGIVITIS; INFLAMMATION. This provides dramatic relief. Most people recover fully and without complications in about two peritonsillar abscess A serious and painful weeks. INFECTION of the tissues around the tonsils in the See also ENDOSCOPY; EPIGLOTTITIS; MONONUCLEOSIS, back of the THROAT. Unlike TONSILLITIS, which is pri- INFECTIOUS.

44 presbycusis 45 pharyngitis INFLAMMATION and irritation of the can cause COUGH, especially when lying down or pharynx (the top part of the THROAT), often due to asleep. Swallowed postnasal drip often causes viral or bacterial INFECTION. Seasonal allergies, NAUSEA. environmental irritants such as smoke, and Mucus production is the body’s natural mecha- uncontrolled GASTROESOPHAGEAL REFLUX DISORDER nism for removing pathogens and debris from the (GERD) are also common causes of pharyngitis, nasal passages, and it is normal for it to increase as often called sore throat. a protective measure when there is irritation to the nasal passages. Treatment focuses on identify- Pharyngitis that interferes with BREATH- ing the underlying cause of continued excessive ING or swallowing requires emergency production. ANTIBIOTIC MEDICATIONS are helpful medical care. only when the cause is bacterial INFECTION. Med- ications to reduce INFLAMMATION in the nasal pas- Many pathogens can cause infections. Doctors sages, such as oral ANTIHISTAMINE MEDICATIONS or estimate that viruses cause about 60 percent of nasal sprays, can help reduce mucus production; pharyngitis and BACTERIA cause about 30 percent. however, overuse of nasal sprays results in Distinguishing the responsible PATHOGEN guides rebound congestion (increased mucus production treatment, as bacterial pharyngitis requires treat- when not using the spray). Drinking plenty of flu- ment with ANTIBIOTIC MEDICATIONS. It is difficult to ids helps keep mucus thin, making it easier for the determine the cause of pharyngitis on the basis of body to expel. Humidified air may reduce irrita- symptoms. The only conclusive diagnostic meas- tion to the nasal passages to slow mucus produc- ure is a throat culture to identify what pathogens tion. are present. See also BACTERIA; BLOWING THE NOSE; FOREIGN The primary symptom of pharyngitis is a OBJECTS IN THE EAR OR NOSE; RHINORRHEA; SNEEZE. scratchy or sore throat. Other symptoms may occur, depending on the cause, such as FEVER, presbycusis The natural diminishment of hear- HEADACHE, COUGH, and SNEEZE. Most viral pharyngi- ing ability that occurs with aging. HEARING LOSS tis runs its course in 7 to 10 days. Bacterial affects both ears, is sensorineural, and progresses pharyngitis greatly improves within 2 days of initi- in a predictable pattern, beginning with sounds in ating antibiotic therapy, though it is essential to the high frequency range (2,000 Hz to 4,000 Hz). take the antibiotic medication until it is gone. Researchers do not know the precise mechanisms Reducing or eliminating exposure to irritants such through which presbycusis takes place, though as cigarette smoke and pollen helps with nonin- most believe it occurs through a cumulative loss of fectious pharyngitis. A doctor should evaluate cells from the inner EAR, the NERVE pathways to acute pharyngitis (pharyngitis that comes on sud- the BRAIN, and within the brain itself. Many factors denly) that continues longer than 10 days, and influence the rate of progression. One third of chronic pharyngitis (ongoing or recurrent) on a adults between age 65 and 74 and half of those regular basis. Chronic pharyngitis can signal other beyond age 74 have age-related hearing loss. health problems, such as laryngeal CANCER. Health conditions that affect blood circulation and See also ALLERGIC RHINITIS; LARYNGITIS; POSTNASAL nerve function, such as ATHEROSCLEROSIS and DIA- DRIP; SINUSITIS; SMOKING AND HEALTH; STREP THROAT. BETES, intensify the effects of age-related changes. Noise exposure can exacerbate the rate and nature postnasal drip Mucus from the NOSE that flows of hearing loss. Older adults also are more likely to down the back of the THROAT. Postnasal drip is a take medications that have ototoxic side effects, common complaint and may accompany various such as loop diuretics and certain antihypertensive health conditions, including COLDS, ALLERGIC RHINI- medications. TIS, SINUSITIS, and OTITIS media. Postnasal drip is a Early indications of presbycusis, which may common cause of PHARYNGITIS because it irritates become apparent when a person is in his or her the tissues at the back of the throat (pharynx) and late 50s or early 60s, include difficulty hearing 46 The Ear, Nose, Mouth and Throat certain sounds and words, because the frequency improve hearing ability, though the progressive range that is lost is that of conversation. Turning loss of hearing may eventually exceed the capabil- up the volume on the television and perceptions ity of the HEARING AID. that other people are mumbling are also signs of See also AGING, OTOLARYNGOLOGIC CHANGES THAT hearing loss. There are no known methods for OCCUR WITH; NOISE EXPOSURE AND HEARING; OTOTOXIC- preventing presbycusis. Hearing aids often ITY; PRESBYOPIA. R

rhinoplasty Plastic surgery to repair or recon- rhinorrhea The medical term for runny NOSE. struct the NOSE. Surgeons perform rhinoplasty Mucus discharge from the nose is the body’s operations for cosmetic and for reconstructive rea- mechanism for removing foreign matter. Numer- sons. Cosmetic rhinoplasty is the most commonly ous factors can cause rhinorrhea. Among the most performed PLASTIC SURGERY procedure in the United common are exposure to allergens, such as pollen States, with more than 350,000 operations each and dust, and INFECTION, such as COLDS, SINUSITIS, year. Reconstructive rhinoplasty helps restore the OTITIS, and PHARYNGITIS. In young children, foreign function and appearance of the nose when there objects in the nose also commonly cause rhinor- are structural defects such as SEPTAL DEVIATION or rhea. Discharge that contains pus or blood sug- following serious trauma (such as a BROKEN NOSE) gests infection. and conditions such as SKIN CANCER or other can- cers affecting the nose. Clear, watery nasal drainage following Rhinoplasty is nearly always an AMBULATORY SUR- head trauma requires immediate med- GERY performed under general or local ANESTHESIA. ical attention as this may indicate that The surgeon may reshape the CARTILAGE and occa- CEREBROSPINAL FLUID is leaking. sionally the BONE. Swelling and discoloration are common following the OPERATION, gradually dimin- Rebound rhinorrhea can develop with exces- ishing over two to three weeks. Bleeding and INFEC- sive use of nasal sprays as well as oral deconges- TION are among the potential risks of rhinoplasty. tants and ANTIHISTAMINE MEDICATIONS. When the Because the nose has an abundant blood supply, doctor can identify the underlying cause, treat- surgeons typically insert compression packing into ment targets that cause. Otherwise, treatment tar- the nose for one to three days after surgery, which gets relief of symptoms. Topical decongestants applies pressure to minimize bleeding and maintain (nasal sprays) are the treatment of first choice, the integrity of the reshaping. The packing carries a applied for a short and defined period of time. The risk of TOXIC SHOCK SYNDROME, a serious systemic doctor may also recommend oral decongestants or bacterial infection. The surgeon should promptly antihistamines. evaluate any FEVER or increase in PAIN. See also BLOWING THE NOSE; EPISTAXIS; FOREIGN As with any surgery, the results of rhinoplasty OBJECTS IN THE EAR OR NOSE; SNEEZE/COUGH ETIQUETTE. can vary. It is important to understand the limita- tions and consequences of the operation and to ruptured eardrum A tear in the TYMPANIC MEM- have realistic expectations for cosmetic results. BRANE, or eardrum, that results from trauma of Reconstructive rhinoplasty may require several some kind. The primary symptoms are operations to achieve the desired outcome. Most people can return to their regular activities within • sudden and sharp PAIN from the EAR two weeks. See also BLEPHAROPLASTY; OTOPLASTY; RHYTIDO- • drainage (when the cause is INFECTION) PLASTY; SURGERY BENEFIT AND RISK ASSESSMENT. • TINNITUS (a ringing or roaring sound)

47 48 The Ear, Nose, Mouth and Throat

• HEARING LOSS in the affected ear The doctor’s otoscopic examination of the ear, which allows visualization of the tympanic mem- A tear in the tympanic membrane causes it to brane, confirms the diagnosis. Most ruptured lose tension, which affects hearing as the breach eardrums heal without intervention in about six affects the eardrum’s ability to vibrate. When weeks, with hearing gradually improving as the infection (OTITIS media) causes the rupture, the tympanic membrane regains integrity and tension. pain of the tear is followed by relief of pain For a large tear, the otolaryngologist may put a because the tear releases the fluid that has accu- small paper patch over the opening to help protect mulated in the middle ear behind the tympanic the inner ear while the tear heals or may perform membrane. Other common causes of ruptured an OPERATION (TYMPANOPLASTY) to repair the dam- eardrum include aged eardrum. Earplugs are necessary during bathing or showering to keep water from entering • exposure to a sudden, loud noise the auditory canal during the time the tear is • BAROTRAUMA (damage from rapid and extreme HEALING. Hearing typically returns when the tear changes in pressure) heals. A potentially significant consequence of • puncture from a foreign object inserted into the ruptured eardrum is formation of a ear, such as a cotton swab or hair pin (bobby CHOLESTEATOMA, a cystlike growth in the inner ear pin) being used to clean CERUMEN (ear wax) that can permanently damage hearing. from the auditory canal See also MYRINGITIS; MYRINGOTOMY; OTOSCOPY. S

salivary glands Structures within the MOUTH that septal deviation A shift from midline in the produce saliva, a watery fluid that mixes with nasal septum (wall of tissue that separates the air food during chewing and maintains the mouth as pathways of the NOSE). Septal deviation can cause a moist environment. The major salivary glands various health conditions such as chronic SINUSITIS are primarily along the floor of the mouth (the (INFECTION), EPISTAXIS (nosebleed), and obstructed sublingual and submandibular glands) and at BREATHING. It can occur as a natural defect or result the back of the mouth just below the EAR from trauma such as a blow to the nose. The treat- (parotid glands). These glands produce a steady ment of choice is surgical correction (septoplasty) supply of saliva that trickles into the mouth to to restore the septum to midline. Septal deviation moisturize mucous membranes. Stimuli related to often accompanies structural anomalies of the eating, such as the smell or appearance of food, nose that cause people to seek RHINOPLASTY (surgi- activate an increased flow of saliva to meet the cal reconstruction of the nose). needs of mastication (chewing). Enzymes in saliva See also SEPTAL PERFORATION; SURGERY BENEFIT AND begin to break down foods to prepare them for RISK ASSESSMENT. digestion. The facial and glossopharyngeal nerves, the septal perforation An abnormal opening in the seventh and ninth CRANIAL NERVES respectively, nasal septum (wall of tissue within the NOSE that regulate the functions of the salivary glands. The divides the nostrils), that occurs as the result of glossopharyngeal NERVE also handles nerve chronic irritation, trauma, or cancer. Septal perfo- impulses for the sense of taste. Small mineral cal- ration may develop with long-term use of nasal culi, or stones, can block the salivary ducts that oxygen, long-term use of corticosteroid nasal drain saliva from the salivary glands, causing PAIN sprays (such as to treat ALLERGIC RHINITIS), inhala- and swelling (SIALOLITHIASIS). Excessive saliva (SIAL- tion of illicit drugs such as COCAINE or aerosols and ORRHEA), or drooling, can a symptom of various glues, foreign objects in the nose, chronic digital neurologic conditions, including CEREBRAL PALSY trauma (picking the nose), or long-term exposure and PARKINSON’S DISEASE, and often accompanies to chromates such as chromic acid and chromium SWALLOWING DISORDERS. Saliva production tem- (used in electroplating and other industrial appli- porarily increases in young children who are cations). Septal perforation sometimes occurs as a teething, likely an attempt by the body to soothe consequence of RHINOPLASTY, particularly when the discomfort of the new TEETH erupting through there have been several operations. the surface of the gums. The parotid glands swell Symptoms of septal perforation may include a with the MUMPS. whistling sound when BREATHING, nasal discharge, For further discussion of the salivary glands and bleeding (EPISTAXIS). The preferred treatment within the context of otolaryngologic structure for most septal perforations is surgical repair (sep- and function please see the overview section “The toplasty), though it is sometimes necessary to first Ear, Nose, Throat, and Mouth.” remedy the underlying cause. The doctor may See also SIALADENITIS. place a nasal septal prosthesis, commonly called a

49 50 The Ear, Nose, Mouth and Throat nasal button, that fits into the perforation to cre- parotid SALIVARY GLANDS. Its primary symptoms are ate a temporary closure. Untreated septal perfora- PAIN and swelling when it blocks the flow of saliva tion results in frequent infections and continued from the gland. Sometimes the calculus remains erosion of the nasal lining as well as CARTILAGE. symptomless and undetected until it shows up on See also FOREIGN OBJECTS IN THE EAR OR NOSE; an X-RAY done for other reasons such as a routine OCCUPATIONAL HEALTH AND SAFETY; RHINORRHEA; SUR- dental exam. Doctors sometimes use COMPUTED GERY BENEFIT AND RISK ASSESSMENT. TOMOGRAPHY (CT) SCAN, ULTRASOUND, or sialography to confirm the diagnosis. A small calculus may sialadenitis INFLAMMATION and swelling of a sali- pass from the gland on its own. Because the risk vary gland, usually a submandibular or parotid of INFECTION is high, however, doctors prefer to gland. Common causes include surgically remove salivary calculi. The OPERATION involves making a small incision into the salivary • SIALOLITHIASIS, in which a small “stone” or min- gland and extracting the calculus. Recovery is usu- eral calculus blocks the flow of saliva and irri- ally complete, though some people have recurrent tates the tissues of the involved salivary gland episodes or experience narrowing (stricture) of the affected salivary duct. Researchers do not know • bacterial INFECTION, which can develop when what causes salivary calculi to develop. the blockage persists because the MOUTH con- See also SIALADENITIS; SURGERY BENEFIT AND RISK tains an abundance of BACTERIA ASSESSMENT. • viral infection with various viruses, including MUMPS, coxsackie, INFLUENZA, herpes, and sialorrhea Excessive saliva production that may human immunodeficiency virus (HIV) result in drooling or choking if there are impair- • AUTOIMMUNE DISORDERS such as SJÖGREN’S SYN- ments to swallowing. Sialorrhea often accompa- DROME and SYSTEMIC LUPUS ERYTHEMATOSUS (SLE) nies neurologic disorders and BRAIN injuries that affect the parasympathetic NERVOUS SYSTEM, which Diagnosis arises mostly through physical regulates the functions of most of the body’s examination and other clinical indicators, though glands. People who have sialorrhea are at risk for sometimes the doctor will order X-rays or other ASPIRATION (inhaling excessive saliva into the air- imaging procedures to help distinguish the cause ways and LUNGS), choking, INFECTION, and irritation or to determine whether an ABSCESS (pocket of of the SKIN around the face and neck. Sialorrhea infection) is present. Treatment focuses on the also presents significant hygienic concerns and underlying cause of the inflammation. Bacterial often is embarrassing to the person who has it. sialadenitis requires treatment with ANTIBIOTIC Anticholinergic medications, which “dry out” MEDICATIONS. Antibiotics are not helpful for viral the body, curtail sialorrhea in many people. These sialadenitis, which typically improves in 10 to 14 medications also affect neurotransmitters in the days. Regardless of cause, drinking plenty of flu- brain, however, which can have unintended detri- ids, frequently rinsing the mouth with warm salt- mental effects on motor function. Some people water or applying warm compresses (moist heat) benefit from botulinum toxin A injections (BOTU- to the outside of the face over the affected area, LINUM THERAPY) into the tissues surrounding the and taking a nonsteroidal anti-inflammatory drug salivary glands, which temporarily paralyzes the (NSAID) such as ibuprofen can help relieve dis- muscles that release saliva. Other treatment comfort. approaches include surgery to remove or obstruct See also BACTERIA; HIV/AIDS; NONSTEROIDAL ANTI- portions of the submandibular salivary glands, INFLAMMATORY DRUGS (NSAIDS); VIRUS; X-RAY. which produce about 80 percent of the saliva, and therapy to improve muscle control and swallow- sialolithiasis The formation of a crystallized ing ability. Treatment success depends on the mineral deposit, called a salivary calculus underlying causes. (“stone”), in a salivary gland. Sialolithiasis most See also NEUROTRANSMITTER; SIALADENITIS; commonly involves the submandibular and SIALOLITHIASIS. sinusitis 51 sign language A nonverbal language that serves of BONE commonly called the cheek bone, and the as a system of communication for people who are frontal sinuses, above the inside corners of the hearing impaired. Sign language uses hand signals eyes near the bridge of the nose, are the sinuses to represent letters of the alphabet and gestures to that most commonly become congested as a result represent words, phrases, and concepts. As in spo- of COLDS, allergies, and infections. The sinuses also ken languages, sign languages incorporate an function as sound chambers that give the voice extensive vocabulary with rules that govern its resonance and amplification. Sinus congestion presentation (grammar and syntax). The sign lan- limits this function, resulting in a characteristic guages most used in the United States are “nasal” voice. For further discussion of the sinuses within the • American Sign Language (ASL) derives its context of otolaryngologic structure and function structure from French Sign Language, which please see the overview section “The Ear, Nose, was the first formal sign language, and is a Mouth, and Throat.” unique language separate from spoken English. See also ALLERGIC RHINITIS; NASAL POLYP; SINUSITIS. ASL is the third most common language in the United States. sinusitis INFLAMMATION of the SINUSES. The most • Signing Exact English (SEE) evolved in the common causes of sinusitis are INFECTION and envi- early 1970s as a method to manually code spo- ronmental irritation such as seasonal allergies ken English for children learning to read and (ALLERGIC RHINITIS). Sinusitis affects an estimated 37 for people without hearing impairment who million Americans each year. It can be acute (lasts communicate with those who have hearing a few weeks), chronic (lasts months to years), or impairment. recurrent (occurs in repeated acute episodes). • Pidgin Signed English (PSE) blends aspects of Doctors further define chronic sinusitis by the ASL and SEE for colloquial or casual communi- extent of permanent damage to the mucous lining cation. of the nasal passages. Long-term chronic sinusitis causes narrowing of the openings through which Though sign languages may carry a culture’s mucus drains out of the sinuses. name, such as American Sign Language or Japan- ese Sign Language, there is no correlation Symptoms and Diagnostic Path between the sign language and the culture’s spo- The symptoms of sinusitis include ken language. Nor are sign languages necessarily similar to each other. • PAIN across the cheek bones or between the The BRAIN processes sign languages differently eyes from spoken languages. Because spoken languages • pain in the upper jaw and TEETH form the basis for reading and writing, prelingual • persistent HEADACHE that is worst on awakening children who have profound HEARING LOSS may in the morning and improves through the day easily learn a sign language and yet have difficulty though does not entirely go away learning to read and write. • nasal congestion See also BRAILLE; COGNITIVE FUNCTION AND DYS- FUNCTION. • frequent sneezing • thick, colored discharge from the nostrils sinuses Cavities within the facial bones around • POSTNASAL DRIP the NOSE, also called the paranasal sinuses, that warm and moisten inhaled air. Mucous membrane Some people with sinusitis also have FEVER, lines the sinuses, providing a continuous supply of COUGH, and PHARYNGITIS (from the postnasal drip). moisture. Mucus production increases in response The diagnostic path includes careful examination to irritation, for example, from environmental of the inside of the NOSE. For acute sinusitis the particles (pollen, smoke), viruses, and BACTERIA. doctor may make the diagnosis on the basis of The maxillary sinuses, on the face along the ridge what he or she observes. Doctors seldom order 52 The Ear, Nose, Mouth and Throat regular X-rays, once the standard of diagnosis, and taste messages incorrectly. Dysfunctions that because the results are not reliable. For chronic affect the perceptions of smell and taste are com- sinusitis the otolaryngologist conducts an exten- mon side effects of medications, consequences of sive examination that includes a COMPUTED TOMOG- health conditions such as STROKE, and dimensions RAPHY (CT) SCAN and ENDOSCOPY to directly evaluate of aging. Disturbances of smell and taste affect the condition of the sinuses. The doctor may also one’s ability to enjoy daily pleasures such as the culture a sample of the nasal discharge to identify fragrances of flowers and the flavors of foods. But the BACTERIA that are present. smell and taste are not only matters of QUALITY OF LIFE. These chemosenses, as researchers refer to Treatment Options and Outlook them, also provide early warning of potentially Acute bacterial sinusitis requires to treatment with hazardous circumstances. Many spoiled foods, for an ANTIBIOTIC MEDICATIONS. Decongestant medica- example, smell and taste rancid. In the United tions help relieve stuffiness and congestion by States, natural gas distributors add the chemical constricting the blood vessels that supply the mercaptan, which smells strongly like rotten eggs, mucous tissue within the nose. ANTIHISTAMINE MED- to pipelines and storage tanks to warn of gas leaks. ICATIONS mitigate the body’s immune response to Because the functions and disturbances of smell allergens such as dust and pollen that cause local and taste are nearly inseparable, disturbances of irritation of the nasal tissues. one affect the other. Most commonly, diminished Chronic bacterial sinusitis often requires irriga- smell reduces the ability to perceive flavors. tion of the sinuses with a solution of antibiotic Though the taste cells within the taste buds may and decongestant, which the otolaryngologist does remain fully functional, the brain requires the as an office procedure. Home treatment may detailed NERVE signals the olfactory bulb gathers include an oral antibiotic, humidifier to add mois- and sends to interpret flavors. The brain perceives ture to the air, and saline nose drops to keep the primarily bitterness when taste is the only sense nasal passages moist. Moisture helps reduce irrita- sending messages about chocolate, for example, tion and swelling. Surgery may be necessary to because cocoa, chocolate’s key ingredient, is a bit- correct any problems such as septal defect, SEPTAL ter substance. The brain interprets the distinctive PERFORATION, and NASAL POLYP, or to widen the nasal sweetness and flavor of chocolate only when the ostia (openings in the sinuses). olfactory sensors detect and report the hundreds of odor molecules that chewing releases from the Risk Factors and Preventive Measures chocolate, which then swarm into the NOSE from Sinusitis is more common in people who have the back of the THROAT. As much as 80 percent of seasonal rhinitis (allergies). The presence of aller- the perception of flavor derives from smell. gens causes the nasal passages to swell, establish- ing ideal conditions for bacteria to grow. Keeping Symptoms and Diagnostic Path seasonal rhinitis symptoms under control helps Though about 200,000 Americans seek medical reduce congestion. Sinusitis is also more common care for disturbances of taste and smell, health in people with structural anomalies of the nose experts believe millions live with diminished or such as SEPTAL DEVIATION. Untreated, chronic, or altered chemosenses without realizing it. People recurrent OTITIS media (ear infection) can funnel are most likely to notice disturbances that come bacteria to the base of the nose via the EUSTACHIAN on suddenly or involve distinctive changes. Most TUBE. Prompt, appropriate treatment for acute people report problems with taste, though typi- sinusitis helps limit recurrent and chronic infec- cally the culprit is more often related to smell. tions. Symptoms can range from isolated to total loss of See also ALLERGEN; SNEEZE; X-RAY. smell, taste, or both. People may notice they no longer taste the seasonings in foods or smell the smell and taste disturbances Dysfunctions of flowers in a garden. With some health conditions smell and taste result in the inability to perceive such as PARKINSON’S DISEASE, perceptions of flavor odors and tastes or the BRAIN interpreting smell change. People who have DIABETES or HYPERTENSION smell and taste disturbances 53 often experience general reductions in chemosen- changes may persist or become permanent. RADIA- sory perceptions. TION THERAPY to the head or neck also alters Physical obstructions The most common cause chemosensory perception, often permanently. of taste and smell disturbances is congestion, Nerve damage Smell and taste disturbances can which blocks contact between odor molecules and result from damage to the nerves that carry odor sensors in the nose. Congestion results from chemosensory messages to the brain, such as a wide range of circumstances, most of which are might occur with injury or neurologic diseases. temporary or transient (come and go). These The first cranial nerve (olfactory nerve) carries include COLDS, ALLERGIC RHINITIS (seasonal allergies), most odor messages to the brain, with the fifth and SINUSITIS. Mechanical obstructions such as cranial nerve (trigeminal nerve) conveying limited nasal polyps or SEPTAL DEVIATION alter the flow of signals. Three CRANIAL NERVES—the seventh (facial air through the nose so that odor molecules pass nerve), ninth (glossopharyngeal nerve), and tenth by only a small section of the olfactory epithelium, (vagus nerve)—convey taste messages to the the patch of nerve endings extending from the brain. Trauma such as from a BROKEN NOSE can olfactory bulb. Dental problems that cause irrita- damage the olfactory nerve endings in the roof of tion in the MOUTH, especially of the tongue, can the nose. Chronic exposure to cigarette smoke or disrupt the functions of taste cells. inhaled drugs (notably cocaine as well as cortico- Aging The aging process is the second-leading steroid nasal sprays used to treat ASTHMA and aller- cause of diminished taste and smell. Researchers gic rhinitis) also damages these hairlike structures. estimate that diminished chemosensory percep- tion affects more than half of people over age 65; Treatment Options and Outlook by age 80 the loss is significant enough to interfere Treatment for smell and taste disorders targets the with the desire to eat. The olfactory epithelium in underlying causes of the disturbances to the the nose loses about 1 percent of its nerve cells extent doctors can identify them. Approaches each year. Though the tongue renews taste buds include every few weeks throughout most of life, the rate • reducing exposure to environmental irritants of replacement slows in the later decades. By age such as cigarette smoke and allergens 80, the number of taste cells in the mouth has diminished by as much as 40 percent. In combina- • treating chronic sinusitis, dental disease, and tion with the loss of olfactory nerve endings, there allergic rhinitis often is the perception of complete inability to • removing nasal polyps and correcting septal perceive flavors. defects in the nose • evaluating regular medications being taken to Health conditions and medication side effects identify any that can interfere with smell and Many health conditions can cause disturbances of taste smell and taste. Among those most frequently • looking for patterns of chemosensory distur- implicated are diabetes, hypertension, SARCOIDOSIS, bance BELL’S PALSY, Parkinson’s disease, ALZHEIMER’S DIS- EASE, and MULTIPLE SCLEROSIS. Olfactory auras (per- Often, idiopathic taste and smell disturbances ceptions of smells) often precede migraine (those of undetermined cause) improve on their headaches and epileptic seizures. Numerous med- own over time. Changes due to diseases tend to ications affect taste and smell, notably ANTIBIOTIC follow the course of the underlying condition, MEDICATIONS, levodopa (to treat Parkinson’s dis- progressively worsening along with the principal ease), angiotensin-converting enzyme (ACE) condition, as in Parkinson’s disease or multiple inhibitors (antihypertensive medications), “statin” sclerosis. lipid-lowering medications, and CHEMOTHERAPY agents such as cisplatin and methotrexate. Taste Risk Factors and Preventive Measures and smell usually return to normal after stopping Treating infections promptly and avoiding irritants the medication, though chemotherapy-related that interfere with olfactory and gustatory func- 54 The Ear, Nose, Mouth and Throat tions are the most effective measures for protect- sneeze so often that their noses become raw and ing the chemosenses. Subclinical sinusitis (ongo- irritated. Nasal sprays containing decongestants ing sinus infection that does not have symptoms), help reduce swelling of the nasal passages; those structural defects of the nose (such as nasal polyps containing antihistamines help subdue the nose’s and septal deviation), and allergic rhinitis are the local reaction to allergens. These approaches are most common causes of disturbances involving often effective in reducing sneezing episodes. these senses. Most are correctable, which nearly Increasing the moisture content of the nasal always restores smell and taste. Other efforts mucosa, such as by BREATHING humidified air and include reducing exposure to cigarette smoke, drinking plenty of fluids, helps relieve irritation. industrial pollutants, and inhaled drugs such as Many viruses, such as those that cause COLDS cocaine. Unfortunately age-related diminishment and INFLUENZA, have adapted their structures to is permanent. Most people with smell and taste take advantage of the sneeze mechanism, using it disturbances can learn methods to accommodate to disperse themselves to new hosts. To reduce the the diminished perception of flavor with season- spread of these infections, health experts recom- ings (other than salt and sugar) to enhance foods mend sneezing into disposable tissues and discard- and beverages. ing them, then washing the hands thoroughly See also AGING, OTOLARYNGOLOGICAL CHANGES THAT with soap and water. OCCUR WITH; NASAL POLYP; SJÖGREN’S SYNDROME; Some people sneeze when they step into sun- SMOKING AND HEALTH. light or look up at a sunlit sky, called photic sneez- ing. Doctors do not know why photic sneezing sneeze A REFLEX that forcefully expels air occurs, though it is an inherited trait. Some through the NOSE. A sneeze originates with an irri- researchers speculate that sunlight (or any very tation to the mucous membranes in the nose, bright light) stimulates brain activity near the sometimes perceptible as a tickling sensation and brain’s sneeze center, which sends the message to other times not noticeable, that activates NERVE the body to sneeze. About one in four people impulses. The fifth cranial nerve (trigeminal experiences photic sneezing. nerve) carries the impulse to a cluster of special- See also BAROTRAUMA; BLOWING THE NOSE; CRANIAL ized neurons (nerve cells) in the brainstem (the NERVES; HAND WASHING; NASAL VESTIBULITIS; SNEEZE/ part of the BRAIN that regulates the body’s basic COUGH ETIQUETTE; VIRUS. vital functions including reflexes). Scientists call this area the sneeze center, though they do not sore throat See PHARYNGITIS. know its precise location because it is not physi- cally distinct from other portions of the brainstem. speech disorders Conditions that affect the abil- The sneeze center sends nerve signals back to the ity of structures of the MOUTH and THROAT to form body through numerous nerve pathways that acti- the sounds necessary for speech. Health-care vate a coordinated response. providers often refer to these conditions as disor- A sneeze results when the brainstem signals the ders of articulation to distinguish them from VOCAL CORDS to close, allowing air pressure to build LEARNING DISORDERS that may affect speech. Learn- in the airway, then signals the DIAPHRAGM and vari- ing disabilities typically involve BRAIN function, ous muscles in the chest, THROAT, and face to con- whereas speech or articulation disorders involve tract and the vocal cords to open. This sequence of the mechanics of speech. events expels air through the nose with great Many speech disorders arise from structural force; researchers have measured sneezes leaving anomalies that become apparent during early the nose at the equivalent of 100 miles per hour. childhood, such as CLEFT PALATE/CLEFT PALATE AND The pressure blows mucus and irritants from the LIP, incorrect placement of the TEETH as they erupt, nose. or deviations in the size and shape of the oral cav- When the irritation stops, the cycle of the ity. Functional difficulties, such as tongue control sneeze reflex ends. People who have a health con- and lip placement during articulation, may also dition such as SINUSITIS or ALLERGIC RHINITIS may cause or contribute to speech disorders. HEARING swallowing disorders 55

LOSS, neurologic conditions that affect control of priate treatment, most people experience the muscles of the face and throat, and brain improvement, and many people experience com- injury are additional factors that influence the plete restoration, of speech. Children may need ability to speak, particularly in adults. STROKE is a ongoing speech therapy as their facial features leading cause of speech disability in adults. continue to grow and change. Symptoms of speech disorders range from the See also APHASIA; VOICE THERAPY. obvious to the subtle and may include swallowing disorders Conditions that impair the • omitted sounds, in which certain consistent functions of the muscles and nerves of the THROAT, sounds do not appear in speech, for example, interfering with the ability to swallow. The clinical leaving the starting or ending consonants off term for this impairment is dysphagia. Swallowing words disorders often exist with neuromuscular disorders • substituted sounds, in which one sound substi- such as AMYOTROPHIC LATERAL SCLEROSIS (ALS) and tutes for another, such as w for r (wabbit) MUSCULAR DYSTROPHY, and as a consequence of damage to portions of the BRAIN resulting from • distorted sounds, in which extra noises such as STROKE or TRAUMATIC BRAIN INJURY (TBI). Dysphagia whistling or whooshing accompany certain can affect any aspect of the swallowing process, words or letters from chewing to entry of the swallowed material • slurred, slow sounds, called dysarthria, which into the STOMACH. Swallowing problems in young represent an inability to coordinate the neuro- infants may indicate structural anomalies. Swal- logic and muscular functions necessary for lowing disorders are common among the elderly speech and in people of any age who have significant physical debility. Speech disorders may indicate disorders of The symptoms of swallowing disorders may vary brain function; a comprehensive NEUROLOGIC EXAM- in severity and sometimes with circumstances. For INATION helps make this determination. Speech dif- example, dysphagia may manifest when the person ficulties that suddenly arise suggest a physical is very tired or eats certain foods though not be basis, such as injury to the brain (stroke) or dam- apparent at other times. Symptoms may include age to the NERVE pathways between the brain and the face. Speech disorders may also appear as a • SIALORRHEA (drooling) component of learning disabilities and other • extended chewing because the food will not developmental factors. In children, the reasons for move to the back of the throat for swallowing speech disorders sometimes remain unclear, • difficulty initiating swallowing though speech therapy often can eliminate the symptoms. • inability to swallow certain kinds of substances The first goal of treatment is to remedy any such as liquids apparent physical causes such as cleft palate or • frequent choking misaligned teeth. Other treatment targets • weight loss (secondary to inability to consume strengthening the muscles of the tongue and face adequate calories) in conjunction with learning proper placement of the tongue and lips during speech. This is the The diagnostic path includes a careful health venue of speech therapy, which provides instruc- history and complete physical examination. Swal- tion to help with forming the mouth positions and lowing studies evaluate the coordination and con- movements necessary for articulation. The speech trol of muscles involved in moving food from the therapist, also called speech-language pathologist, MOUTH to the stomach. A BARIUM SWALLOW X-ray, in may use video and audio recordings in combina- which the person swallows a solution containing tion with physical findings to assess the extent and barium that coats the ESOPHAGUS, or videofluo- possible causes of speech disorders and to develop roscopy can show irregularities in the passageway methods to overcome the difficulties. With appro- to the stomach. COMPUTED TOMOGRAPHY (CT) SCAN or 56 The Ear, Nose, Mouth and Throat

MAGNETIC RESONANCE IMAGING (MRI) can provide ful for some people. Surgery may be necessary to added visualization of the throat and upper gas- correct esophageal strictures that narrow the pas- trointestinal tract. Laryngoscopy allows the doctor sageway for food. to examine the structures of the inside of the Most people experience improvement with throat. The diagnostic path may also include a treatment, though swallowing disorders resulting NEUROLOGIC EXAMINATION to determine the presence from degenerative conditions such as Parkinson’s of conditions such as PARKINSON’S DISEASE that can disease are likely to worsen as the disease pro- affect the ability to swallow. gresses. In such situations, alternatives such as Treatment depends on the underlying cause. ENTERAL NUTRITION or PARENTERAL NUTRITION (supple- Sometimes medications to relax certain muscles or mental or replacement feedings) may become nec- reduce the flow of saliva improve the functions of essary. Family members of those who have chewing and swallowing. Swallowing therapy swallowing disorders should know how to per- (provided by a speech-language pathologist) can form the HEIMLICH MANEUVER to dislodge food that teach methods to strengthen muscles and improve becomes aspirated into the TRACHEA. coordination of the steps of swallowing as well as See also ACHALASIA; CALORIE. ways to prepare food and position it in the mouth for most effective swallowing. BIOFEEDBACK is help- swimmer’s ear See OTITIS. T

toothache PAIN in a tooth or in the jaw. A “sore throat” typically refers to discomfort Toothache typically suggests DENTAL CARIES (cavities) involving any of these structures. The muscles of or other dental problems. Dentists provide care the throat participate in swallowing, BREATHING, when this is the case. Early intervention minimizes and speech. The Adam’s apple, a bulge in the CAR- tooth loss, the extent of other damage such as to TILAGE visible on the front of the throat (more visi- the gums and jaw, and the extent of treatment. ble in men than women though present in both) marks the position of the THYROID GLAND and PARA- Persistent jaw pain, particularly when THYROID GLANDS. it extends from the shoulder into the neck and jaw, can be an early warning COMMON CONDITIONS AFFECTING THE THROAT sign of HEART ATTACK. A physician should ADENOID HYPERTROPHY COUGH evaluate such pain without delay. CROUP EPIGLOTTITIS LARYNGEAL CANCER LARYNGITIS NONSTEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS) LARYNGOCELE OBSTRUCTIVE SLEEP APNEA such as ibuprofen and naproxen effectively relieve PERITONSILLAR ABSCESS PHARYNGITIS most tooth pain in the short term. Topical anes- POSTNASAL DRIP SWALLOWING DISORDERS thetics or products containing clove oil, designated TONSILLITIS VELOPHARYNGEAL INSUFFICIENCY for oral use (use in the mouth), temporarily VOCAL CORD CYST VOCAL CORD NODULE relieve pain when applied to the tooth surface or VOCAL CORD PARALYSIS VOCAL CORD POLYP surrounding gum tissue. Good ORAL HYGIENE and adequate dietary calcium and vitamin D help For further discussion of the throat within the maintain tooth health. context of otolaryngologic structure and function A toothache sometimes indicates health condi- please see the overview section “The Ear, Nose, tions such as SINUSITIS (sinus infection), OTITIS (ear Mouth, and Throat.” infection), migraine HEADACHE, TEMPOROMANDIBULAR See also NOSE. DISORDERS, and NEURALGIA (INFLAMMATION and irrita- tion) affecting the nerves that supply the face. thrush A yeast (FUNGUS) INFECTION of the inner Physicians provide care for these conditions. MOUTH. The fungus Candida albicans causes thrush, See also GINGIVITIS; PERIODONTAL DISEASE; TEETH. which appears in the mouth as reddened patches with a white discharge. Doctors may use the throat The collective term for the structures at broader terms CANDIDIASIS or moniliasis. C. albicans the back of the MOUTH that provide passage to the is a common fungus present in the healthy body, structures and organs of the trunk. The throat kept in check by the BACTERIA that are also present. includes the pharynx, which carries food to the It becomes pathogenic (disease causing) only ESOPHAGUS and air to the TRACHEA, and the larynx, when there are disturbances to the body’s natural or voice box, which contains the VOCAL CORDS. The balance that allows it to flourish. tonsils are at the back and top of the throat; the Thrush is most common in infants between the tongue extends to the front and top of the throat. ages of 1 month and 10 months, though it can 57 58 The Ear, Nose, Mouth and Throat occur at any age. Often, and especially in infants, people live with low-grade tinnitus that, though doctors do not know what disturbs the balance to annoying when noticed, generally does not affect allow thrush to develop. Known causes include daily living. For some people, however, tinnitus is treatment with ANTIBIOTIC MEDICATIONS, as antibi- severe enough to interfere with concentration and otics reduce the overall level of bacteria in the even hearing to the extent of causing disability. body. IMMUNE DISORDERS such as HIV/AIDS often pre- Any health conditions that diminish the move- vent the body from adequately controlling its bac- ment of sound into the ear from the external terial balance. environment, such as accumulated CERUMEN or an Doctors generally diagnose thrush based on ear INFECTION (OTITIS media or otitis externa) can appearance of the characteristic lesions (patches) intensify the tinnitus. in the mouth. Sometimes the doctor will gently The diagnostic path begins with an otoscopic scrape away the white surface of a LESION, which examination to look for obvious blockages or reveals the underlying reddened sore and con- other physical causes. The doctor will also request firms the diagnosis. Treatment is rinsing the a comprehensive AUDIOLOGIC ASSESSMENT to deter- mouth with an antifungal solution such as nys- mine whether any hearing loss exists; this helps tatin oral suspension. For young infants, dabbing narrow the potential reasons for the tinnitus. the solution onto the lesions is sometimes more Treatment targets the underlying cause. There are effective. Treatment continues for 48 hours after few effective treatments for idiopathic tinnitus the last lesion disappears. C. albicans also can erupt (tinnitus that is present without an apparent as DIAPER RASH and vaginal infection. cause) or for tinnitus that accompanies PRESBYCUSIS See also LEUKOPLAKIA; VAGINITIS. (age-related hearing loss). Many people benefit from using intentional background noise (sound tinnitus The perception of a ringing, humming, masking) to mitigate the tinnitus and from learn- roaring, or rushing sound in the EAR when there is ing conscious refocusing methods. no external auditory stimulation. Tinnitus may See also HEARING AID; OTOTOXICITY. affect one ear or both ears. There is a growing view among otolaryngologists that tinnitus is an tonsillitis An INFECTION of the tonsils (lymph early indication of sensorineural HEARING LOSS, structures at the back of the THROAT). Tonsillitis is heralding damage (temporary or permanent) to common and often recurrent in children. Conven- the HAIR cells within the COCHLEA that translate tional wisdom holds that the tonsils (and the sound waves into NERVE messages. Tinnitus is a nearby ADENOIDS) serve to produce antibodies to common symptom of various vestibular disorders help the body protect itself against invading such as ACOUSTIC NEUROMA and MÉNIÈRE’S DISEASE. pathogens (disease-causing agents such as viruses Numerous medications also can cause tinnitus, and BACTERIA). However, in the modern environ- notably ANTIBIOTIC MEDICATIONS known as amino- ment there is an overwhelming abundance of glycosides (such as gentamicin and streptomycin) pathogenic agents, which many health experts and loop diuretics (such as furosemide). believe accounts for the prevalence of tonsillitis. Occasionally tinnitus results from health condi- Some researchers believe that the tonsils are tions that affect the flow of BLOOD in the head, such becoming, or have become, vestigial structures as HYPERTENSION (high BLOOD PRESSURE) and ATHERO- akin to the appendix. SCLEROSIS. These conditions may increase the turbu- The characteristic symptoms of tonsillitis are lence of the blood, making it possible to hear the blood as it flows through the arteries. When these • PAIN and swelling at the back of the throat conditions are severe enough, the doctor can also • difficulty swallowing hear the sounds by listening through a stethoscope • FEVER placed at various locations on the head. • HEADACHE Tinnitus is common, with some experts assert- ing that nearly every adult will experience the The tonsils may appear enlarged and reddened, symptom at some time in his or her life. Many and may ooze pus or be covered in small white tympanoplasty 59 dots. The infectious agent may be viral or bacter- The tympanic membrane is vulnerable to perfo- ial; the doctor is likely to swab the throat to per- ration, commonly called RUPTURED EARDRUM. Perfo- form a rapid strep test to check for streptococci ration may occur as a result of injury, such as bacteria. Streptococci tend to migrate to other penetration of an object or from a sharp blow to parts of the body such as the HEART valves, making the outer ear, or spontaneously. Fluid accumula- any strep infection potentially dangerous. A throat tion in the middle ear behind the tympanic mem- culture can determine the presence of other path- brane, usually the consequence of INFECTION, is the ogenic bacteria. Bacterial tonsillitis, including STREP most common cause of spontaneous perforation. THROAT requires treatment with ANTIBIOTIC MEDICA- Spontaneous perforation generally heals without TIONS. Viral tonsillitis generally runs its course intervention. Traumatic perforation may require within two weeks. In either case, ANALGESIC MED- surgical repair (TYMPANOPLASTY). ICATIONS such as acetaminophen or ibuprofen can In addition to amplifying and transferring provide pain and fever relief. sound waves, the tympanic membrane protects the middle and inner ear from bacteria and debris. Children should not receive aspirin for A perforated eardrum exposes the delicate struc- pain or FEVER because of the potential tures behind it to possible infection and other for REYE’S SYNDROME, a rare but serious damage. Repeated spontaneous perforation due to complication. chronic OTITIS media (middle ear infection) can permanently scar the tympanic membrane, The otolaryngologist may recommend tonsillec- restricting its ability to vibrate. The otolaryngolo- tomy (an OPERATION to remove the tonsils) when gist may insert a small tube through the tympanic recurrent tonsillitis causes the tonsils to remain membrane to allow collected fluid to drain enlarged to the extent that they interfere with (MYRINGOTOMY) as a preventive measure in chil- BREATHING. Indications of this include loud dren who have chronic ear infections. snoring when sleeping and mouth breathing See also CLEANING THE EAR; FOREIGN OBJECTS IN THE when awake, particularly in children. Enlarged EAR OR NOSE; HEARING LOSS; MYRINGITIS. tonsils can cause OBSTRUCTIVE SLEEP APNEA, in which there are episodes during sleep when the person tympanoplasty Surgical reconstruction of the does not breathe. In the normal course of devel- TYMPANIC MEMBRANE (eardrum). Damage to the opment, the tonsils atrophy (shrink) as ADOLES- tympanic membrane can occur as a result of scar- CENCE approaches, and by early adulthood ring due to repeated OTITIS media (middle EAR tonsillitis is uncommon. For this reason many INFECTION), traumatic injury, and acquired defects doctors prefer to manage tonsillitis medically such as might remain following removal of a rather than surgically unless ANTIBIOTIC RESISTANCE CHOLESTEATOMA (pocketlike growth). The otolaryn- develops. gologist cuts out a small piece of FASCIA (thin con- See also EPIGLOTTITIS; LARYNGITIS; OTITIS; PHARYNGI- nective tissue that covers muscle) from the TIS; PERITONSILLAR ABSCESS; SINUSITIS; VIRUS. temporal MUSCLE at the point of incision behind the ear when the OPERATION begins; this becomes tympanic membrane A thin piece of tissue that the new tympanic membrane. Restoration of stretches across the base of the auditory canal (EAR hearing varies and may depend on factors not canal). The tympanic membrane, commonly related to the tympanoplasty. Infection, which called the eardrum, vibrates in response to sound may be present in the middle ear at the time of waves that reach it by traveling from the outer ear the surgery, can cause the new tympanic mem- through the auditory canal. The vibrations amplify brane to fail. About 80 percent of adults who the sound waves, which activate the auditory ossi- undergo tympanoplasty experience improvement cles, tiny bones in the middle ear, to set in motion in hearing and reduced otitis. the cascade of events that results in NERVE signals See also MYRINGOTOMY; OTOPLASTY; RHINOPLASTY; traveling to the BRAIN. SURGERY BENEFIT AND RISK ASSESSMENT. V velopharyngeal insufficiency Inadequate clo- vertigo The perception of movement, usually sure the velopharyngeal sphincter, a MUSCLE at the spinning, when none is taking place. Vertigo rep- back of the soft palate, that directs air flow to the resents the body’s inability to accurately interpret NOSE or to the MOUTH. Velopharyngeal insufficiency its position and movement within its environ- often accompanies CLEFT PALATE/CLEFT PALATE AND ment. People with vertigo feel either that they are LIP anomalies and interferes with both speech and moving or the setting around them is moving. swallowing. It also can occur as a complication of Vertigo occurs when the balance mechanisms of tonsillectomy and adenoidectomy, operations to the vestibular system, including the NERVE path- remove the tonsils and ADENOIDS, respectively, and ways to the BRAIN, malfunction. The disturbance of neurologic damage, such as from STROKE, that can range from mild and brief to extended and restricts neuromuscular function of the pharynx. debilitating. Vertigo is a symptom of numerous The hallmark symptoms of velopharyngeal insuffi- health conditions that can be vestibular (affecting ciency are nasal speech and regurgitation food the structures of the inner EAR) or neurologic into the back of the nose with swallowing. Some- (affecting the brain or nerves). Situations that times the person has chronic or recurrent SINUSITIS overstimulate the vestibular system, such as spin- resulting from food particles becoming trapped in ning rapidly in circles (as in carnival rides) or the sinuses. The doctor may be able to feel a previ- experiencing gravitational force (as in taking off in ously undiagnosed cleft in the hard palate beneath a jet or a space shuttle), also often generate tem- an intact soft palate. ULTRASOUND or COMPUTED porary vertigo. TOMOGRAPHY (CT) SCAN can confirm the diagnosis. Treatment for velopharyngeal insufficiency Causes of Vertigo when the cause is a structural anomaly begins Vertigo develops when the brain receives conflict- with surgery to restore sphincter function to the ing or incomplete information from the vestibular extent possible. Operations may include repair of system about the body’s orientation in its environ- a cleft palate or reconstructive surgery to extend ment. This can occur because injury or disease the soft palate (pharyngoplasty) to make the damages the structures of the vestibular system or velopharyngeal opening smaller. Most people sub- the parts of the NERVOUS SYSTEM that convey bal- sequently need speech therapy to retrain oral- ance and movement information to the brain. facial structures to form the sounds the Brain injury, such as from trauma or STROKE, that velopharyngeal insufficiency kept them from affects parts of the brainstem involved in move- properly making. These therapeutic interventions ment also can result in vertigo. typically restore complete function, though may Most commonly vertigo reflects dysfunction of not be appropriate or successful when the cause of the vestibular system and the structures of the the velopharyngeal insufficiency is neurologic inner ear. The semicircular canals, three fluid- damage or a neuromuscular disorder. filled loops, detect rotational movements. The sac- See also OPERATION; SPEECH DISORDERS; SURGERY cule and the utricle, also fluid-filled chambers, BENEFIT AND RISK ASSESSMENT; SWALLOWING DISORDERS. detect linear (horizontal and vertical) movements.

60 vestibular neuronitis 61

The nerve cells in these structures send a continu- these structures, surgical interventions are typi- ous stream of signals to the movement centers of cally viable options only when there is also pro- the brain, which in turn direct the muscles to found and irreversible HEARING LOSS. respond in ways that keep the body upright and stable. This flow of communication takes place Preventing Vertigo immeasurably fast and without conscious aware- Situational vertigo is preventable by avoiding the ness, as long as all components of the system are circumstances that cause it. Pathologic vertigo functioning properly. results from underlying disease processes that Situational disruptions of vestibular functions often are not possible to mitigate. Methods such as (such as a carnival ride creates) resolve sponta- focusing the eyes in the direction of movement neously when the stimulatory overload stops and can sometimes minimize a vertigo episode. Some the body returns to normal functions, though vertigo is positional, so avoiding the positions pre- residual sensations of NAUSEA or queasiness may vents the vertigo. Quick movements of the head, remain. Pathologic disruptions—changes brought particularly upward, are known to bring on ver- about by damage or disease—often result in per- tigo in many conditions in which vertigo occurs sistent balance disturbances, the key symptom of (such as Ménière’s disease). which is vertigo. Space flight is providing an ideal opportunity for researchers to study the mechanisms of bal- Relieving Vertigo ance and vertigo, as nearly all astronauts experi- Situational vertigo, such as from spinning in cir- ence vertigo under the extreme gravitational and cles, resolves itself when the environmental stim- centrifugal forces to which leaving and reentering ulation stops. When vertigo is pathologic, certain the earth’s gravitational field subjects them as well ANTIHISTAMINE MEDICATIONS, commonly marketed as the absence of gravity during space flight. The for relief of motion sickness, often provide relief. normally functioning vestibular system uses grav- Researchers do not know the mechanisms ity as its point of reference for determining the through which antihistamines intercede with body’s position and movement. Researchers hope vestibular functions. Most antihistamines that can that gaining understanding of how the body relieve vertigo also cause substantial drowsiness, adapts to the absence of gravity will shed light on making them unsuitable in situations that require how the vestibular system functions as well as alertness and concentration. dysfunctions, leading to new preventions and Maintaining the focus of the eyes on the direc- treatments for vertigo and the conditions for tion of movement can help stabilize the vestibular which it is a symptom. system. This method provides additional informa- See also ACOUSTIC NEUROMA; BENIGN PAROXYSMAL tion to the brain via sight about the body’s posi- POSITIONAL VERTIGO (BPPV); LABYRINTHITIS. tion and movement. It also is a diagnostic device in helping distinguish the nature of the dysfunc- vestibular neuronitis A dysfunction of the tion: vestibular or neurologic. Many people obtain vestibular system that causes sudden and severe relief from ACUPUNCTURE and acupressure. Pressure VERTIGO (sensation of spinning) with accompany- bands are available that activate the acupuncture ing NAUSEA, VOMITING, and balance disturbances. points on the inner wrists; rubbing the earlobes The prevailing view is that viral infections cause activates the acupuncture points there. vestibular neuronitis. Because hearing remains Surgical interventions may become necessary unaffected, doctors believe the INFECTION inflames to treat severe, unremitting vertigo that becomes the vestibular NERVE, the branch of the eighth cra- disabling. These are procedures of final resort, as nial nerve (vestibulocochlear nerve) leading from they create permanent disruptions in the vestibu- the vestibular structures to the BRAIN. INFLAMMA- lar system such as severing the vestibular nerve or TION causes the vestibular nerve to transmit con- removing the labyrinthine structures of the inner fused and erroneous signals to the brain. The ear. Because the function of hearing also uses brain responds to the incoming signals as though 62 The Ear, Nose, Mouth and Throat they were legitimate, instructing the body to react thazine (Phenergan) and the over-the-counter to movement that is not occurring or failing to products dimenhydrinate (Dramamine), meclizine direct reaction when there is movement. This con- (Antivert, Bonine) and diphenhydramine fusion results in vertigo and a sense of spatial dis- (Benadryl). The two prescription medications orientation. Vestibular neuronitis most commonly diazepam (Valium) and clonazepam (Klonopin) occurs in adults between the ages of 40 and 60. appear to act on the vestibular system directly to subdue the vertigo, though cause more sedation Symptoms and Diagnostic Path than antihistamines and can be addictive when The distinguishing symptoms of vestibular neu- used for an extended period of time. ACUPUNCTURE ronitis are severe vertigo and one-sided balance gives some people relief. Most people recover disturbances without TINNITUS or HEARING LOSS. Any completely and are free from residual conse- hearing-related symptoms suggest a different diag- quences in three to four weeks. A small percent- nosis. The vertigo causes nausea and often vomit- age experiences recurrent episodes over the ing. Attempts to move, or to move the head, result following months to years, though the severity of in repeated vertigo. The symptoms often are debil- symptoms diminishes with each episode. itating, with the person falling toward the affected side when attempting to walk and sometimes Risk Factors and Preventive Measures when attempting to sit upright. Symptoms appear Because doctors do not know for certain what abruptly though often follow a cold or occur causes vestibular neuronitis, they cannot identify among groups of people who are in close contact. risk factors or preventive measures. Prompt diagno- An initial episode of symptoms can last 7 to 10 sis and treatment help relieve symptoms more days. quickly but do not appear to alter the course of the The diagnostic path is fairly straightforward; inflammation or affect the likelihood of RECURRENCE. any pattern of vestibular disturbance that includes See also CRANIAL NERVES; BENIGN PAROXYSMAL POSI- additional symptoms is likely to have a different TIONAL VERTIGO (BPPV); LABYRINTHITIS; MÉNIÈRE’S DIS- cause. Confirming diagnostic signs the doctor EASE. looks for include vocal cord cyst A saclike growth on the vocal • horizontal NYSTAGMUS (rapid movements of the cord that usually develops as a result of persistent EYE with certain positions or movements) irritation such as from smoking or GASTROE- • diminished or absent response to caloric testing SOPHAGEAL REFLUX DISORDER (GERD), which may (alternating warm and cool water infused into flush the VOCAL CORDS with gastric juices when an the auditory canal) individual is lying down and especially when he or she is sleeping. A vocal cord cyst often contains Imaging procedures are not likely to offer diag- fluid though can contain solid tissue. A cyst can nostic information unless the doctor is uncertain develop deep within the vocal folds, causing sig- of the diagnosis, in which case MAGNETIC RESONANCE nificant changes or difficulties with the voice. The IMAGING (MRI) or COMPUTED TOMOGRAPHY (CT) SCAN primary symptom of vocal cord cyst is hoarseness. can rule out other conditions such as ACOUSTIC Though vocal cord cysts are noncancerous, oto- NEUROMA. laryngologists generally operate to remove them because they tend to enlarge. Endoscopic surgery Treatment Options and Outlook allows the otolaryngologist to remove most vocal The VIRUS causing the vestibular neuronitis must cord cysts through the THROAT. Recovery from the run its course, which typically takes 10 to 14 days. surgery takes two to four weeks; most people ben- During this time, certain ANTIHISTAMINE MEDICATIONS efit from follow-up VOICE THERAPY to teach meth- used to treat motion sickness can provide relief ods for preserving vocal cord integrity and voice from the vertigo and associated nausea. These quality. antihistamines include the prescription medica- See also OPERATION; SMOKING AND HEALTH; VOCAL tions hydroxyzine (Atarax, Vistaril) and prome- CORD NODULE; VOCAL CORD POLYP. vocal cords 63 vocal cord nodule A noncancerous, fibrous cord. This closes the gap between the cords and growth on the vocal cord, usually the result of encourages both sets of cords to vibrate equally. overusing the voice through repeated shouting, These measures improve, and often restore, vocal singing, or public speaking. Vocal cord nodules cord function. typically develop in book-matched pairs on the See also SPEECH DISORDERS; SWALLOWING DISOR- folds of the VOCAL CORDS at points where the cords DERS; VOCAL CORD CYST; VOCAL CORD NODULE; VOCAL vibrate in contact with each other. Nodules arise CORD POLYP. from the epithelium, or surface layer of tissue, that covers the vocal cords (unlike vocal cord vocal cord polyp A fleshy growth on the vocal polyps, which arise from the mucous membrane cord. Vocal cord polyps occur singly, rather than that forms the vocal cords). Vocal cord nodules paired as do vocal cord nodules, though more have the appearance of calluses and cause the than one polyp may be present. A polyp arises voice to take on a “breathy” quality, though some from the mucous membrane that forms the VOCAL people also experience hoarseness. The otolaryn- CORDS; it grows out from the vocal cord on a stem- gologist can remove vocal cord nodules through like appendage, which allows the polyp to move the THROAT using endoscopic surgery. The surgical freely as the vocal cord vibrates. The location and wound takes about six weeks to heal, after which size of the polyp determine the ways that it inter- VOICE THERAPY helps the person learn methods to feres with speech and hence its symptoms, which protect the vocal cords and voice. Because vocal can include a “breathy” quality to the voice, cord nodules develop through overuse, they are hoarseness, difficulty “starting” the voice, and likely to recur with continued extensive speaking sometimes loss of the voice. or singing. Polyps develop as a result of irritation such as See also VOCAL CORD CYST; VOCAL CORD POLYP. from smoking, chronic POSTNASAL DRIP, environ- mental pollutants, and allergic PHARYNGITIS. Because vocal cord paralysis The inability of the vocal polyps in other locations of the body, such as the cord, a membranous flap of tissue in the larynx, to intestines and the SINUSES, occasionally become open or close properly with the passage of air. cancerous, otolaryngologists recommend prompt PARALYSIS may affect one vocal cord or both VOCAL surgical removal. Most people fully recover within CORDS. Paralysis that affects both vocal cords is rare four to six weeks. VOICE THERAPY can teach methods and often affects BREATHING, as air cannot move to preserve and protect the voice. Continued expo- freely through the THROAT. Symptoms include sure to the causative irritants, such as cigarette hoarseness, a “breathy” quality to the voice, dimin- smoke, is likely to result in recurrent polyps. ished vocal volume, and occasionally throat PAIN. See also OCCUPATIONAL HEALTH AND SAFETY; OPERA- Vocal cord paralysis often develops without an TION; SMOKING AND HEALTH; VOCAL CORD CYST; VOCAL identifiable cause, though also results from injury CORD NODULE. to the throat or nerves that supply the throat, BRAIN injury (such as trauma or from STROKE), and neuro- vocal cords A paired fold of thick, fibrous tissue logic conditions such as MULTIPLE SCLEROSIS and in the back of the larynx that vibrate with the pas- PARKINSON’S DISEASE. People who use their voices sage of air to produce sounds. The vocal cords run extensively, such as singers and teachers, are espe- lengthwise in the larynx. Muscles that attach the cially prone to vocal cord paralysis. vocal cords to the larynx contract and relax to The diagnostic path typically includes laryn- change the tautness of the vocal cords, producing goscopy to examine the larynx and vocal cords. variations in sound tone and volume. The vocal Because vocal cord paralysis often goes away on cords relax during BREATHING to allow free passage its own, doctors often take a watchful waiting of air through the larynx. The “talk test” for AERO- approach in combination with VOICE THERAPY to BIC EXERCISE is an indirect measure of the volume improve voice function and quality. If the paraly- of air flowing through the THROAT: being unable to sis continues, the otolaryngologist can inject a speak during exercise means air flow is high bulking agent such as collagen into the paralyzed enough that the vocal cords cannot contract. 64 The Ear, Nose, Mouth and Throat

Singing and extended talking can greatly strain mechanical aspects of vocal cord function, MUSCLE the vocal cords, resulting in inflammation (LARYN- control and coordination, and breath control. Voice GITIS) that causes the voice to sound scratchy or therapy typically follows operations on the VOCAL hoarse. Environmental irritants such as pollen or CORDS and larynx to restore voice volume and qual- smoke can also cause laryngitis. Cigarette smoking ity. Professionals who use their voices, such as is particularly stressful for the vocal cords, causing singers and lecturers, may find voice therapy bene- extended irritation that may result in chronic ficial in overcoming the deleterious effects of over- hoarseness and growths such as a VOCAL CORD CYST using the voice. A voice therapist also may work or VOCAL CORD POLYP. Cancerous tumors related to with a person who has had a LARYNGECTOMY (surgi- smoking can develop on the vocal cords. Loss of cal removal of the larynx) to improve the quality of the vocal cords, such as due to LARYNGECTOMY (sur- alternate articulation methods such as ESOPHAGEAL gical removal of the larynx) for laryngeal CANCER, SPEECH or ELECTROLARYNX speech. results in loss of the voice. The techniques of voice therapy vary according For further discussion of the vocal cords within to the diagnosed speech disorder or clinical situa- the context of otolaryngologic structure and func- tion, the person’s speaking needs, and the desired tion please see the overview section “The Ear, outcome. Voice therapy may incorporate resting Nose, Mouth, and Throat.” the voice completely, which allows only 15 min- See also CONDITIONING; ESOPHAGEAL SPEECH; SMOK- utes of total voice use in a 24-hour period of time. ING AND HEALTH; VOICE THERAPY. Other techniques focus on using the breath to generate voice volume and quality, and learning voice therapy Methods and techniques for to adjust the pitch of the voice rather than only improving the ability of the larynx (voice box) to volume to add emphasis to speech. produce speech. Voice therapy focuses on the See also OPERATION; VOCAL CORD PARALYSIS. THE EYES

The eyes conduct the function of vision. Practitioners who provide care for the eyes and vision may be ophthalmologists (medical doctors who specialize in ophthalmology, providing medical and surgical treatment for diseases of the EYE) or optometrists (doctors of optometry who specialize in diagnosing and correcting REFRACTIVE ERRORS of vision). This sec- tion, “The Eyes,” presents a discussion of the structures of the eye and how they function to provide the sense of sight, an overview of VISION HEALTH and disorders, and entries about the health conditions that can affect the eyes and vision.

Structures of the Eye conduit from the EYE to the brain through which EYELIDS IRIS the brain receives about two thirds of the infor- LACRIMAL (TEAR) GLANDS PUPIL mation it processes about the environment out- CONJUNCTIVA ANTERIOR CHAMBER side the body. SCLERA AQUEOUS HUMOR The eye resides within the protective enclosure CORNEA LENS of the orbit, a socket of BONE in the skull. Thin CHOROID POSTERIOR CHAMBER pads of fat cover the orbital bones to cushion the RETINA CILIARY BODY eye. A small opening in the back of the orbit RODS CILIARY PROCESSES allows passage of the optic nerve and the blood CONES CILIARY MUSCLES vessels that supply the eye. The eyelids, upper and MACULA VITREOUS HUMOR lower, blink—automatically open and close—15 OPTIC DISK OPTIC NERVE to 20 times a minute to rinse the eye with tears. Reduced blink rate is a characteristic of neurologic Functions of the Eye disorders such as PARKINSON’S DISEASE; increased Ancient philosophers viewed the eyes as the win- blink rate occurs with eye irritation such as CON- dows to the soul, based on the belief that the JUNCTIVITIS and diseases such as MENINGITIS. The PINEAL GLAND, located deep within the BRAIN, held tears then drain from the lacrimal sac at the inner the soul. Their rudimentary understanding of corner of the eye into the upper NOSE. The eyelids anatomy and physiology led them to conclude also close to protect the eye from hazards such as that the optic nerves connected the pineal gland foreign objects and very bright light, and to cover and the soul directly to the outside world through the eye during sleep to keep it moist. The eye- the eyes. Though modern knowledge of the lashes, extending from the eyelids, also help keep body’s structure and function clarifies that no foreign objects from striking the eye and the eye- such physical pathway exists, ancient scientists brows channel sweat around the eyes. were not entirely off track. The pineal gland does Six muscles attach the eye to the orbit, func- appear to receive direct information from the tioning in pairs as well as in coordination with external environment, which influences its pro- one another to move the eye. These muscles inte- duction of MELATONIN, a HORMONE related to the grate into the sclera, the fibrous outer layer of the body’s circadian cycles (cycles of wakefulness and eye, and extend to the back of the orbit where sleep). Researchers do not fully understand the they anchor to the bone. When one MUSCLE in a mechanisms of this, and it is possible the OPTIC pair contracts, the other relaxes. Typically both NERVE plays some role. However, the primary eyes move in tandem, which allows the eyes to function of the optic NERVE is to provide a direct simultaneously focus on the same object. This 65

The Eyes 67 provides depth perception and accommodates darken in response to sun exposure. In the retina, each eye’s “blind spot.” Some people have the these cells form a “blackout screen” that elimi- ability to intentionally move their eyes indepen- nates reflection, allowing lightwaves to reach and dent of each other, though unintentional disparate activate the rods and cones without interference. movement generally indicates a pathologic condi- The macula, a small circular area in the center of tion. Discordant movement may characterize neu- the retina, contains the most dense distribution of rologic disorders such as progressive supranuclear cones and handles fine detail vision. The “blind palsy (PSP) and TRAUMATIC BRAIN INJURY (TBI). spot,” the point at which the optic nerve enters Abnormal eye movements also accompany the retina, is the optic disk; it contains no rods or vestibular disorders (disturbances of the balance cones. RETINITIS PIGMENTOSA (hereditary degenera- mechanisms of the inner EAR). tion of the retina) and RETINAL DETACHMENT (separa- tion of the retina from the choroid) are among the MUSCLES THAT MOVE THE EYE conditions that can affect the retina, resulting in • Superior oblique and inferior oblique rotate the eye impaired vision and blindness. primarily in a circular motion. The physics of vision Lightwaves pass through • Superior rectus and inferior rectus move the eye pri- the cornea and the LENS to enter the eye through marily up and down. the pupil, the opening in the circular muscle that • Lateral rectus and medial rectus move the eye prima- rings the lens, the iris. The iris is the colored part rily side to side. of the eye; the pupil in its center appears black because it reveals the dark interior of the eye. The How the eye “sees” The sclera gives the eye its iris dilates (increases the size of) the pupil to allow shape and rigidity. The front part of the sclera more light to enter the eye and constricts forms the “white” of the eye, the coloration com- (decreases the size of) the pupil to reduce the light ing from the white pigmentation of the fiber cells. that enters the eye. The cornea and the lens each In its center, the sclera becomes transparent, form- refract, or bend, the entering lightwaves. The cil- ing the CORNEA. The middle layer of the eye’s wall iary muscles contract and relax to move the lens, is the choroid, a thin, dark membrane rich in which thickens or flattens, respectively, to BLOOD vessels. The choroid loosely attaches to and improve focus. After about age 40 the lens gradu- nourishes the sclera and the eye’s innermost layer, ally loses its FLEXIBILITY, accounting for age-related the RETINA, where sight becomes vision. difficulty with near vision (PRESBYOPIA). Specialized cells infuse the retina, which lines Refracted light forms a final focal point that, in the back of the inner eye. These cells, rods and the healthy eye, aligns in a pattern on the retina cones, convert lightwaves into electrical impulses. at the back of the eye. The mechanics of this Rods are the most plentiful, numbering about 120 refractory process are such that the image result- million on each retina, and detect light in percep- ing on the retina is upside down. When interpret- tions of shades of gray. Cones detect color and ing and assembling nerve signals from the eye, the detail; there are about 6 million of them on each brain automatically reverses the image to perceive retina. Cones are sensitive to red, green, or blue. it right-side up. Refractive ASTIGMATISM, HYPEROPIA, Rods and cones contain photosensitive chemicals and MYOPIA when the final focal point falls short of that react to different wavelengths of light. The or extends beyond the retina, resulting in images reactions alter the electrical charges of the rods that are out of focus or distorted. and cones, creating nerve signals. Each minute of Helping keep the lightwaves from fragmenting wakefulness thousands of these impulses traverse during refraction are two chambers of fluid, the the optic nerves, carrying messages the brain then aqueous humor, which fills the space between the interprets and assembles as visual images. cornea and the lens (the anterior chamber), and The optic nerve, which contains more than a the vitreous humor, which fills the interior of the million nerve fibers, carries these signals to the eye. The ciliary processes, specialized folds of the brain. The pigmented cells of the retina are rich in eye’s choroid layer that extend into the posterior melanin, the same chemical that causes the SKIN to chamber at the corners of the lens behind the iris, 68 The Eyes produce aqueous humor. This watery fluid is RETINOPATHY of prematurity, a leading cause among about the consistency of saliva and serves also to children of vision impairments ranging from STRA- lubricate and nourish the cornea. Aqueous humor BISMUS (inability to focus both eyes on the same circulates through the anterior chamber between object) to legal blindness. the cornea and the lens, then drains from the eye via the drainage angle, a channel between the iris Traditions in Medical History and the cornea. Dysfunction of the drainage angle As refractive errors are very common, practition- is a hallmark characteristic of GLAUCOMA. ers throughout history have tried various and Vitreous humor forms when the eye completes sometimes hazardous methods for improving or its development during the final trimester of ges- restoring vision. The earliest documentation of tation. A substance similar to water in chemical corrective lenses for this purpose dates to 16th composition and to gelatin in consistency, vitreous China. European traders who traveled to China humor maintains the eye’s shape and helps keep noted the elderly holding quartz crystal lenses to the retina smooth and even against the back of see objects close to them. Eyeglasses set in frames the eye. The volume of vitreous humor increases and worn on the face began to appear in Europe as the eye grows though otherwise remains con- in the 17th and 18th centuries. By the late 19th stant (unlike the aqueous humor, which the eye century inventors were experimenting with glass continuously produces). Around age 40 years the lenses placed directly on the eye. These attempts vitreous humor begins to liquefy as a normal produced large, heavy, and ultimately unfeasible process of aging, causing VITREOUS DETACHMENT, lenses that covered the entire surface of the eye. which usually has little effect on vision though The contact lens finally became a reality in the can produce FLOATERS (fragments of tissue that 1950s with the advent of high-tech plastics that become suspended in the vitreous humor). were lightweight, optically clear, and inert (did not react with body fluids). Subsequent advances VISION IMPAIRMENT over the next 30 years brought about lenses made • Refractive errors occur when the focal point of light- of surgical plastics that allow oxygen to reach the waves entering the eye fails to align properly on the cornea, much improving comfort and safety. By RETINA (ASTIGMATISM, nearsightedness, farsightedness). the 1990s, daily wear disposable contact lenses • Functional limitations result when corrected vision became the standard of contact lens correction. remains insufficient to allow participation in activities CATARACT, the clouding and discoloration of the or occupations that require sight. eye’s lens that develops with aging, has for cen- • Legal blindness exists when corrective measures can- turies been the leading cause of blindness in not restore VISUAL ACUITY to 20/200 or VISUAL FIELD to adults. It also is one of the earliest documented greater than 20 degrees. vision problems for which practitioners used sur- gical treatments to remedy, perhaps because the Health and Disorders of the Eyes cause of the problem, the cloudiness, was so More than 150 million Americans have a VISION apparent. CATARACT EXTRACTION AND LENS REPLACE- IMPAIRMENT that requires CORRECTIVE LENSES (eye- MENT has become so commonplace in contempo- glasses or contact lenses)—30 percent of men and rary ophthalmology that the procedure is no less 40 percent of women. About 12 million Ameri- an expectation for restoring vision than are eye- cans have uncorrectable vision impairments that glasses for correcting refractive errors. In about 20 result in functional limitations; 10 percent of them minutes, the ophthalmologist removes the meet the criteria for legal blindness. Among those clouded lens and replaces it with a synthetic one. who have uncorrectable vision impairments, 50 Ancient physicians, lacking the benefits of the percent are age 65 or older. Though the eyes arise anesthetics that make the surgery painless for directly from the evolving brain very early in fetal today’s patients, became skilled at “couching” a development, their formation becomes complete cataract in only seconds. The procedure required during the final 12 weeks of PREGNANCY. Infants the doctor to distract the patient long enough to born before 32 weeks of gestation are at risk for puncture the cornea and push the lens out of the The Eyes 69 line of vision. The lens remained within the eye as attached over the lens can have similar effect. though resting, hence the term “couching.” The Implantable replacement lenses are expanding result was less than perfect because the person lost beyond their initial application in cataract extrac- the refractive ability of the lens, but the procedure tion and replacement to offer nearly ideal vision restored enough vision to allow one to function in for people with severe astigmatism or myopia daily life. In the 1950s ophthalmologists began (nearsightedness). removing the cataract from the eye, but not until Cataract extraction and lens replacement now the 1970s did technology and technique converge routinely restores sight for more than 90 percent in procedures that incorporated a replacement of people who otherwise would lose vision to lens. cataracts. Other surgical procedures offer hope for altering the course of glaucoma. New treatments Breakthrough Research and Treatment Advances may stem the loss of vision due to AGE-RELATED The evolution of knowledge and advances in laser MACULAR DEGENERATION (ARMD). These conditions technology are converging to present treatment are the leading causes of vision impairments that options that were science fiction a decade ago. lead to functional limitations or legal blindness New procedures are greatly expanding the poten- among adults. And research continues to explore tial for permanent correction of disorders and a “bionic” PROSTHETIC EYE that can convert light- defects of the eye, including refractive disorders, waves to nerve impulses and transmit them to the that reduces and may eventually even eliminate brain. Such a prosthesis would function similarly the need for corrective lenses. Refined laser tech- to the COCHLEAR IMPLANT used to restore some types niques such as LASIK allow ophthalmologists to of neurosensory HEARING LOSS. Because many of reshape the cornea in precise, microscopic incre- the conditions that result in vision impairment are ments. Implantable rings inserted around the edge not preventable, technological innovations such as of the cornea can help flatten and reshape it to these appear to be the future of ophthalmologic alter its refractive ability. Permanent contact lenses treatment. A age-related macular degeneration (ARMD) A • “missing pieces” in the field of vision, such as progressive condition that results in the gradual parts of words or gaps in the appearance of deterioration of the macula, the portion of the lines or objects RETINA that provides the ability to see fine detail, • the need for increased light to perform tasks and loss of vision from the center of the field of that require close vision vision. ARMD is the leading cause of VISION IMPAIR- • faded colors MENT, resulting in functional limitations and legal blindness in people over the age of 50. ARMD • tendency to look slightly to the side of objects develops when the retina’s BLOOD supply dimin- to see them clearly ishes. The macula’s high concentration of cones, • distorted or wavy lines on linear objects such as the cells responsible for color and fine detail signs, doorways, and railings (suggests wet vision, makes it especially vulnerable to damage ARMD) and its cells begin to die. The death of the cells result in diminished vision. ARMD may affect one As the macular degeneration progresses, a blind eye at first, though nearly always affects both eyes spot in the center of vision becomes apparent and as it progresses. enlarges. Wet ARMD progresses far more rapidly There are two forms of ARMD, atrophic (com- than dry ARMD. A simple screening test called the monly known as dry) and neovascular (commonly AMSLER GRID can show the gaps in vision that known as wet). All ARMD begins as the atrophic occur with either form of ARMD. The ophthal- form, in which the nourishing outer layer of the mologist uses further procedures, such as OPHTHAL- retina withers, or atrophies. Approximately 90 MOSCOPY and SLIT LAMP EXAMINATION, to visualize the percent of ARMD remains in this form and pro- retina and macula and determine which form of gresses slowly. In the remaining 10 percent, new ARMD is present and how extensive the damage. blood vessels begin to grow erratically within the The ophthalmologist looks for signs of exudation choroid, the blood-rich membrane that nourishes (swelling of the tissue that oozes fluid) that sug- the retina. These blood vessels are thin and fragile, gests wet ARMD, and for drusen (spots of depig- and bleed easily. The resulting hemorrhages cause mentation on the macula that signal the loss of the retina to swell, distorting the macula and retinal cells). For wet ARMD, the ophthalmologist accelerating the loss of cells. may perform a diagnostic procedure called fluo- rescein angiography, in which the ophthalmologist injects fluorescein dye into a VEIN and then takes Symptoms and Diagnostic Path photographs of the retina as the dye flows ARMD begins insidiously and people tend to through its blood vessels. attribute early symptoms to the normal changes of aging. Early symptoms include Treatment Options Treatment options for ARMD are limited, and at • blurring of words when reading this time there really are no treatments for dry

70 aging, vision and eye changes that occur with 71

ARMD. Some research studies demonstrate the • have CARDIOVASCULAR DISEASE (CVD) such as rate of degeneration slows with increased con- HYPERTENSION (high blood pressure), ATHEROSCLE- sumption of the antioxidants lutein and zeaxan- ROSIS, or CORONARY ARTERY DISEASE (CAD) thin, and vitamins A, C, and E. For wet ARMD the laser treatments photocoagulation and photody- People who have more than one risk factor, namic therapy are sometimes effective in sealing especially when one of the risk factors is family bleeding blood vessels and thwarting their growth, history, should frequently and regularly monitor though they cannot permanently halt the neovas- their vision using the Amsler grid. Early diagnosis cularization or restore vision already lost. Photo- is particularly important with wet ARMD, for coagulation uses a hot laser to cauterize the blood which limited treatment options exist. ARMD vessels but also destroys cells in the vicinity of the develops in people over age 50. An ophthalmolo- targeted blood vessels. With photodynamic ther- gist should evaluate changes that alter the field of apy, the ophthalmologist injects a photosensitive vision, especially those that take the form of dis- DRUG into the person’s veins, then uses a cool laser tortions or “missing pieces.” Regular ophthalmic to target blood vessels in the retina when the drug examinations are important to detect ARMD as reaches them. The light of the laser is not intense well as other conditions that affect the eye and enough to burn the tissue though activates the vision with advancing age. drug, which then destroys the blood vessels. See also AGING, VISION AND EYE CHANGES THAT OCCUR WITH; HEMORRHAGE; OPHTHALMIC EXAMINATION; Outlook and Lifestyle Modifications RETINAL DETACHMENT; VISION HEALTH. For most people who have ARMD vision declines slowly and may affect only one eye for a long time aging, vision and eye changes that occur with before affecting the other eye as well. Because the The structures of the EYE and the processes of loss affects the center of the field of vision, vision vision begin to undergo changes in the late fourth loss is not complete though affects activities that or early fifth decade of life. By age 65, 50 percent require detailed focus, such as reading and driv- of people have vision impairments. By age 80, ing, and typically reaches the level of legal blind- more than 90 percent of people have vision ness. Numerous community and health-care impairments. Treatment can mitigate some of resources can assist with adaptive methods to these changes, such as PRESBYOPIA and CATARACT. accommodate diminishing vision. Even with wet Some conditions that affect the eye and vision ARMD, which progresses more rapidly and more develop secondary to other health conditions that severely than dry ARMD, some vision remains. are more prevalent in older people, such as DIA- Causes and Preventive Measures BETES, HYPERTENSION, and KIDNEY disease, all of Researchers do not know what causes ARMD, which can cause RETINOPATHY. Much loss of vision though it appears to have a hereditary component related to aging is progressive and permanent, in that it runs in families. There are few treat- interfering with activities such as driving, reading ments, and there is no cure, though there is evi- and other close work, and seeing at night. How- dence that antioxidants slow the rate of ever, most people retain the ability to see well deterioration and the loss of vision. Vision loss is enough to function in everyday activities. permanent. As yet there are no known measures Adaptations to accommodate the changes of to prevent ARMD. It appears that ARMD is more the eye and vision with aging are numerous and common in people who: can help maintain a desirable QUALITY OF LIFE for many people. CORRECTIVE LENSES or reading glasses • smoke cigarettes are effective for presbyopia. Surgery can improve vision impairments such as cataract (CATARACT • have blue or green eyes EXTRACTION AND LENS REPLACEMENT), corneal damage • experience extensive exposure to ultraviolet (corneal reshaping or CORNEAL TRANSPLANTATION), rays, as in sunlight exposure and PTOSIS and ECTROPION (BLEPHAROPLASTY). Magni- 72 The Eyes

EYE CHANGES OF AGING AND THEIR EFFECTS ON VISION Physical Change Resulting Health Condition Effect on Eyes or Vision death of cones in the macula AGE-RELATED MACULAR DEGENERATION (ARMD) diminished VISUAL ACUITY in the center of vision white rim around the CORNEA arcus senilis none

LENS cloudiness and discoloration CATARACT blurred or hazy vision; faded colors; progressive loss of vision

“STROKE” of the OPTIC NERVE that ISCHEMIC OPTIC NEUROPATHY diminished visual acuity; decreased interrupts the flow of blood VISUAL FIELD; progressive loss of vision slowed chemical reactions in NIGHT BLINDNESS diminished visual acuity in low-light the rods circumstances liquefaction of the vitreous humor VITREOUS DETACHMENT FLOATERS loss of lens FLEXIBILITY PRESBYOPIA diminished ability to focus on near objects atrophy (weakening) of the eyelid PTOSIS; ECTROPION partial occlusion of visual field; can cause muscles and tissues, shifting of CONJUNCTIVITIS, KERATITIS, CORNEAL INJURY the orbital fat pads

fiers for reading and close work, adjustments on nant eye and “ignores” nerve signals from the televisions and computers to enlarge screen nondominant, or “lazy,” eye. Untreated amblyopia images, voice-activated telephone dialers, high- can result in permanent vision impairment or intensity light sources, and screen readers with legal blindness. voice output are among the devices available to The diagnostic path includes close examination accommodate low vision. of the eyes to determine whether other disease See also GENERATIONAL HEALTH-CARE PERSPECTIVES; processes are present that might account for the VISION HEALTH. vision deficit. Treatment targets those processes, such as cataracts or REFRACTIVE ERRORS, when they amblyopia A VISION IMPAIRMENT, commonly called exist. When the eye is otherwise healthy and nor- “lazy eye,” in which the pathways between the mal, treatment consists of forcing the brain to rely EYE and the BRAIN do not properly handle the on the amblyopic eye, usually by patching the processes of sight. Amblyopia is most common in dominant eye for structured periods of time. children. The impairment often develops when Sometimes the ophthalmologist will substitute there are circumstances that allow one eye to atropine drops in the eye, which dilate the pupil become dominant in sending NERVE impulses to and distort the eye’s ability to focus, when a child the brain, such as STRABISMUS (the inability of the refuses to wear an eye patch or an eye patch is eyes to focus on the same object) or congenital otherwise not the most appropriate therapeutic cataracts (opacity of the lens). Amblyopia can also choice. The dilation interferes with the eye’s abil- develop when there is significant disparity in the ity to focus, forcing the brain to interpret nerve refractive capabilities of the eyes, such as when messages from the untreated eye. one eye is hyperopic (farsighted) or myopic (near- When detected and treated in children who are sighted) and the other eye has normal vision. The under age 9, most amblyopia responds to treat- brain becomes accustomed to messages the domi- ment and vision returns. Delayed or inadequate astigmatism 73 treatment may result in permanent dysfunction Astigmatism may affect one EYE or both eyes. Typi- of the eye–brain pathways, as these become cally the irregularity results in two focal points of entrenched by age 9 or 10. After this time the light that reach the RETINA instead of a single focal vision pathways are well established and ambly- point, resulting in blurred or distorted images. opia can no longer develop. Astigmatism often coexists with HYPEROPIA (far- See also ASTIGMATISM; HYPEROPIA; MYOPIA; PTOSIS. sightedness) or MYOPIA (nearsightedness) and tends to run in families. Corrective measures Amsler grid A basic test to detect or monitor the include eyeglasses, contact lenses, and REFRACTIVE progression of AGE-RELATED MACULAR DEGENERATION SURGERY. Mild astigmatism may not produce (ARMD), a condition in which the macula, the area noticeable vision disturbances, in which case it on the RETINA responsible for fine detail vision, does not require correction. The success of correc- deteriorates. The Amsler grid is a square with tive measures depends on the extent and nature evenly spaced horizontal and vertical lines, and a of the corneal irregularities. Astigmatism often dot in the center of the grid. The grid’s four corners accompanies age-related changes in the eyes and and lines should appear visible, straight, and intact. vision, and is a common SIDE EFFECT of CORNEAL Wavy lines, gaps in the lines, or missing segments TRANSPLANTATION. suggest damage to the macula. Such a result Less commonly astigmatism results from irreg- requires further examination from an ophthalmol- ularities in the surface of LENS, called lenticular ogist who specializes in retinal disorders. astigmatism. Options to correct for lenticular astig- See also VISUAL ACUITY. matism are CORRECTIVE LENSES or lens-replacement surgery to implant an intraocular lens. astigmatism A common refractive error of vision See also CATARACT EXTRACTION AND LENS REPLACE- that results from an irregularly shaped CORNEA. MENT; REFRACTION TEST; REFRACTIVE ERRORS. B black eye Bleeding into the tissues around the of the outer surface of the eyelid, typically along EYE resulting from trauma to the area, such as a the rim at the base of the eyelashes. Posterior ble- blow or surgical OPERATION. As with any other pharitis affects the inner surface of the eyelid, typ- bruise, the bleeding causes swelling and discol- ically resulting from blocked oil glands oration. The most significant concerns with a (meibomian glands) along the eyelid. Symptoms black eye are damage to the eye or fractures of the of either form of blepharitis may include orbital bones, which require immediate medical attention. • itching or burning sensation • crusting along the eyelids, especially upon Seek immediate medical attention if awakening these symptoms accompany a black • swelling and redness eye: • PHOTOPHOBIA (excessive light sensitivity) • seeing dark spots (FLOATERS) or flashes of light • excessive tearing • any cuts on the insides of the eyelids • blurry vision or on the eye • blurry, distorted, or double vision Blepharitis may develop as a result of other • numbness on same side of the face conditions such as DERMATITIS or ROSACEA (disorders • trouble moving the eye to look up, that cause SKIN inflammation). When this is the down, or to either side case, treatment targets the underlying condition. When the cause of the inflammation is bacterial, Treatment for a simple black eye is cold to the treatment is topical and sometimes oral ANTIBIOTIC area as quickly as possible after the injury occurs MEDICATIONS. Occasionally the viruses HERPES SIM- and at frequent intervals during the first 24 hours PLEX I (which causes cold sores) and HERPES ZOSTER or until the PAIN subsides and the swelling stabi- (which causes shingles) can infect the eyes. Viral lizes. A black eye may take two weeks to fully infections such as these cause symptoms until heal, and undergoes a number of color changes as they run their course, typically in 7 to 10 days. HEALING progresses. People who participate in Whatever the cause of the inflammation, moist, sports such as softball, baseball, basketball, tennis, warm compresses help loosen crusted secretions racquetball, soccer, and similar events should wear and keep the eyelids clean. EYE care professionals appropriate eye protection. recommend gently washing the eyelids with a See also BLEPHAROPLASTY; ORBITAL CELLULITIS; RETI- mixture of water and baby (tear-free) shampoo. NAL DETACHMENT; RHINOPLASTY; TRAUMA TO THE EYE; Blepharitis tends to be chronic so good eyelid VITREOUS DETACHMENT. hygiene helps minimize recurrences as well as dis- comfort during episodes. blepharitis INFLAMMATION of the eyelids. The See also BACTERIA; CHALAZION; CONJUNCTIVITIS; most common causes of blepharitis are INFECTION DANDRUFF; DRY EYE SYNDROME; HORDEOLUM; ORBITAL and irritation. Anterior blepharitis is INFLAMMATION CELLULITIS. 74 braille 75 blepharoplasty A surgical OPERATION to remove eyelid muscles. Surgery to remove muscle tissue excess tissue from the eyelids to correct drooping (myectomy) or to cut the nerves supplying the upper eyelids and “baggy” lower eyelids. Such eyelid muscles (neurectomy) may provide relief. conditions most commonly develop as a conse- Though therapeutic measures can control symp- quence of aging or extensive weight loss or when toms, as yet there is no cure for blepharospasm. there is damage to the nerves that control the eye- See also BOTULINUM THERAPY; PTOSIS; SURGERY BEN- lid muscles (such as with PARKINSON’S DISEASE). An EFIT AND RISK MANAGEMENT; TIC. ophthalmologist or a plastic surgeon performs ble- pharoplasty, usually as an AMBULATORY SURGERY blindness See VISION IMPAIRMENT. (also called outpatient or same-day surgery). Recovery takes two to four weeks; there can be significant swelling, bruising, and discoloration braille A tactile (touch-based) system of written especially during the first two weeks after the language that features patterns of raised dots to operation. Cold compresses help reduce these represent letters of the alphabet, common words symptoms. The risks of blepharoplasty include and contractions, mathematical symbols, and punctuation. Named after its developer, Louis excessive bleeding and INFECTION. Braille (1809–1852), braille allows people who are See also BLACK EYE; BLEPHAROSPASM; PLASTIC SUR- blind to read and, with adaptive typewriters and GERY; PTOSIS; RHINOPLASTY; RHITIDOPLASTY; SURGERY computer technology, to write. Six dots, in two BENEFIT AND RISK ASSESSMENT. columns of three dots each, form the foundation blepharospasm Involuntary closure of the eyelid for braille; the presence or absence of dots in spe- that results from dysfunction of or damage to the cific patterns identifies the letter, number, symbol, nerves that control the muscles of the eyelids. or concept. There are a number of braille varia- Episodes of closure may range from brief (a tions, or codes, in common use in the United minute) to extended (several hours). Extended States. The major ones are these: closure interferes with vision. Doctors do not know what causes blepharospasm, though it is a • American literary braille code uses about 250 symptom of numerous neurologic and neuromus- patterns to create book-length materials using cular disorders that affect MUSCLE control such as short-form words, contractions, single-cell PARKINSON’S DISEASE and DYSTONIA. Blepharospasm words, and symbols; patterns may have multi- that develops without an apparent underlying dis- ple meanings interpreted by context. order is benign essential blepharospasm. Ble- • Grade 2 braille code is an abbreviated variation pharospasm often begins with minor twitches and of American literary braille code used primarily tics or squinting, progressing over time to forceful for recreational reading materials such as nov- and prolonged contraction of the eyelid muscles. els and nonacademic nonfiction. PHOTOPHOBIA (sensitivity to light) is common. • Grade 1 braille code is the basic alphabet and Fatigue and CAFFEINE may initiate episodes of spasms. numerals 0 through 9. The diagnostic path may include a NEUROLOGIC • Nemeth braille code contains about 600 EXAMINATION to determine whether underlying unique, specialized patterns that are distinct neurologic disorders exist. Blepharospasm requires from American literary braille code for use in treatment when it begins to interfere with the mathematics and science. activities of everyday life. Moderate ble- • Computer braille code provides a mix of Ameri- pharospasm often responds to MUSCLE RELAXANT can literary braille code, Nemeth braille code, MEDICATIONS such as clonazepam (Klonopin) or and unique symbols for computer program- Lioresal (Baclofen), or to medications used to treat ming and instruction documentation. Parkinson’s disease such as levodopa. Many peo- ple obtain long-term relief from injections of botu- • Music braille code is specialized for transcribing linum toxin, which temporarily paralyzes the musical scores. 76 The Eyes

Learning each variation of braille code is like cornea, pushing the cornea into closer contact learning a different language. Most people learn with the eyelid and resulting in further irritation. the one or two variations they are most likely to Bullae, or blisters, develop as the cornea’s attempt use. People whose vision is intact also can learn to relieve the discomfort, much as blisters develop braille, and should if they have regular interac- on the feet or hands in reaction to friction. tions with people who are blind. Many communi- Early symptoms of bullous keratopathy are a ties have schools and consultants who teach sensation of grittiness in the eye, blurred vision, braille as well as libraries that provide braille pub- excessive tearing, and PHOTOPHOBIA (sensitivity to lications. Most public signage in the United States light). When bullae form, and especially when includes braille translations. they rupture, the PAIN often is severe. The oph- See also VISION IMPAIRMENT. thalmologist can diagnose bullous keratopathy using SLIT LAMP EXAMINATION of the cornea, a pain- bullous keratopathy Swelling (edema) and blis- less procedure that combines an intense light tering of the CORNEA. Bullous keratopathy most focused in a slit with magnification through a commonly develops as a complication following ophthalmologic microscope. Eye drops or oint- CATARACT EXTRACTION AND LENS REPLACEMENT or other ment with a higher saline concentration than surgery on the EYE, though it also may develop as tears helps draw fluid out of the cornea, reducing a consequence of chronic irritation such as might the swelling. Soft contact lenses, which absorb occur with DRY EYE SYNDROME. fluid from the eye and shield the cornea from con- The healthy cornea is about 75 percent water. tact with the eyelid, relieve discomfort for many One function of the cells that surround the cornea people. Bullous keratopathy tends to be chronic, is to maintain this fluid balance. Irritation and and over time may result in damage to the cornea trauma that damage these cells diminishes their that requires the cornea’s surgical removal (kera- ability to function, and the cornea retains more totomy) or CORNEAL TRANSPLANTATION. water. The swelling stretches the surface of the See also BLISTER; KERATITIS; UVEITIS. C

cataract Cloudiness and discoloration of the often suggest genetic disorders such as DOWN SYN- LENS. Cataracts become increasingly common with DROME. A congenital cataract that is in the line of advancing age, affecting half of all people age 80 vision (on the visual axis) can cause significant and older. Cataracts were once a leading cause of vision impairment or blindness because the path- age-related blindness. Today ophthalmologists sur- ways for vision develop in the infant’s first few gically remove cataracts and replace the lens with months of life. Ophthalmologists usually remove a prosthetic intraocular lens (IOL) that restores such cataracts as soon as possible. Other congeni- vision. tal cataracts may be small and located so they are Cataracts result from protein deposits that accu- inconsequential to vision; ophthalmologists gener- mulate within the lens. These deposits disperse ally take an approach of watchful waiting with light in much the same way cracks in a window these. might splinter sunlight shining through. The frag- Cataracts of diabetes GLUCOSE, which can be mented light creates areas of accentuated bright- present in high blood levels with DIABETES, inter- ness, causing the halos and sensitivity to lights at acts with the protein structure of the lens, causing night. The opacity of the cataract interferes with protein clumping. People who have type 1 the refractive function of the lens, causing blurry (INSULIN-dependent) diabetes are at greatest risk or hazy vision. The yellow or gray discoloration of for cataracts of diabetes, which often develop at a the lens common with mature or “ripe” cataracts young age. People who have type 2 diabetes or filters the lightwaves that enter the EYE, particu- insulin resistance also are at increased risk. Devel- larly affecting those in the spectrum of blue. The oping cataracts account in part for the vision dis- location of the cataract on the lens determines the turbances that are among the symptoms of nature and extent of VISION IMPAIRMENT. diabetes. Treatment for cataracts of diabetes is the Age-related cataracts Most cataracts develop as same as for age-related cataracts. a function of aging. Protein structures within the body, including the lens of the eye, begin to Symptoms and Diagnostic Path change. The lens becomes less resilient. Such Because cataracts develop slowly, symptoms changes make it easier for proteins to clump become gradually noticeable. Symptoms usually together, forming areas of opacity that eventually affect only one eye (though cataracts may develop form cataracts. Nuclear cataracts form in the concurrently in both eyes) and may include nucleus (gelatinous center) of the lens and are the most common type of age-related cataract. Corti- • blurry or hazy vision cal cataracts form in the cortex, or outer layer, of • double vision the lens and often do not affect vision. • halos around lights at night Congenital cataracts Infants may be born with cataracts. A congenital cataract affecting only one • difficulty seeing at night eye typically is idiopathic (without identifiable • colors appearing faded or dull, or difficulty per- cause); congenital cataracts affecting both eyes ceiving shades of blue and purple

77 78 The Eyes

stage of its development. The vast majority of peo- Gradual loss of vision at middle age and ple who undergo cataract extraction fully recover beyond may be a symptom of AGE- without complications and experience VISUAL ACU- RELATED MACULAR DEGENERATION (ARMD)or ITY correctable to 20/40 or better. GLAUCOMA. Untreated, these conditions result in significant and permanent Surgical Procedure vision impairments. Any decrease in Cataract extraction is nearly always an outpatient vision requires an ophthalmologist’s or surgery performed under local anesthetic and a optometrist’s prompt evaluation. mild general sedative for comfort. There are three surgical procedures for cataract extraction. Each The ophthalmologist can see cataracts during takes 20 to 30 minutes for the ophthalmologist to OPHTHALMOSCOPY, a painless procedure for examin- complete. Many variables influence the ophthal- ing the interior of the eye. mologist’s choice for which to use. Treatment Options and Outlook Phacoemulsification The most commonly per- formed cataract extraction procedure is pha- CATARACT EXTRACTION AND LENS REPLACEMENT is the coemulsification, which requires a tiny incision treatment of choice for nearly all cataracts. There into the capsule containing the lens. The ophthal- is no element of time-sensitivity for the surgery. mologist first uses ULTRASOUND to liquefy the cen- Though VISUAL ACUITY will progressively deteriorate tral nucleus (inner, gelatinous portion of the lens) as the cataract enlarges, there is no permanent and then uses aspiration to remove it. Last the harm to vision by waiting to extract the cataract. ophthalmologist removes the cortex (outer layer Following cataract surgery, more than 90 percent of the lens) from the capsule in multiple segments. of people experience vastly improved vision. Some Extracapsular cataract extraction The extra- people who are unable to receive an IOL because capsular cataract extraction procedure requires a of other eye conditions will need to wear a special slightly larger incision in the capsule, through contact lens or eyeglasses to carry out the refrac- which the ophthalmologist removes the central tive functions of the extracted lens. Nearly every- nucleus of the lens intact, then removes the cortex one will still need reading glasses to accommodate in multiple segments. PRESBYOPIA. Lens replacement After extracting the cataract, Risk Factors and Preventive Measures the ophthalmologist inserts either a monofocal or Cataracts are primarily a consequence of aging. multifocal IOL to give the eye the ability to focus. Cataracts also can develop as a SIDE EFFECT of long- Contemporary lens designs allow the ophthalmol- term STEROID use (therapeutic or performance ogist to fold the lens, insert it into the lens capsule enhancing). Cigarette smoking, excessive ALCOHOL through the tiny incision used to extract the consumption, and extended exposure to sunlight cataract, and unfold the IOL to place it in position. (ultraviolet rays) are among the lifestyle factors associated with early or accelerated cataract devel- BENEFITS AND RISKS OF CATARACT EXTRACTION opment. There are no known methods for pre- Benefits Risks venting cataracts. restores vision postoperative PAIN and swelling See also AGING, EYE AND VISION CHANGES THAT improves QUALITY OF LIFE (uncommon) OCCUR WITH; ANABOLIC STEROIDS AND STEROID PRECUR- postoperative INFECTION SORS; CORTICOSTEROID MEDICATIONS; SMOKING AND (uncommon) HEALTH. RETINAL DETACHMENT (rare) cataract extraction and lens replacement An OPERATION to remove the LENS from the EYE after a Risks and Complications CATARACT (cloudy occlusion in the lens) forms and Most ophthalmologists prescribe antibiotic and replace it with a prosthetic intraocular lens (IOL). anti-inflammatory eye drops applied to the eye for Ophthalmologists can extract a cataract at any four to six weeks following surgery, and recom- cicatricial pemphigoid 79 mend wearing dark glasses in bright light to help ring and pain, the ophthalmologist may recom- protect the eye from light sensitivity. Swelling and mend excising (surgically removing) a chalazion irritation of the tissues around the operated eye is that does not go away or that recurs. The proce- normal in the first few weeks following surgery. dure, with local anesthetic to numb the eyelid, Clear vision may take four to six weeks, though takes only a few minutes in the doctor’s office. many people experience dramatic improvement The wound typically heals within two weeks and immediately. Though the short-term risks of leaves no scarring. Inflammatory skin conditions cataract extraction and lens replacement are such as DERMATITIS or ROSACEA can block the eye- minor, RETINAL DETACHMENT can occur months to lid’s glands, causing a chalazion to develop. Care- years following surgery. ful eyelid hygiene helps keep secretions from Cataract extraction is a permanent solution for accumulating. cataracts. Once removed, cataracts cannot grow See also BLEPHARITIS; CONJUNCTIVITIS; OPERATION. back. Some people do develop a complication called posterior capsule opacity, in which the cicatricial pemphigoid An autoimmune disor- membrane behind the IOL becomes cloudy der in which painful blisters form on the inner (opaque). This is a complication that results when surfaces of the eyelids (and may form on other residual cells that remain after removal of the lens mucus membranes, such as in the MOUTH and begin to grow across the membrane, causing the NOSE). SCAR tissue that forms after the blisters heal membrane to thicken. A follow-up procedure, continues to irritate the inner eyelids as well as either yttrium-aluminum-garnet (YAG) laser cap- the outer surface of the EYE (sclera and CORNEA). sulotomy or conventional surgery, is necessary to The blisters commonly involve the lacrimal (tear) remove the membrane. glands and ducts, reducing tear production and causing DRY EYE SYNDROME. Cicatricial pemphigoid Outlook and Lifestyle Modifications occurs when the body’s IMMUNE SYSTEM produces About 90 percent of people experience vastly antibodies that attack the cells that form the improved vision after cataract extraction. How- mucus membranes. Trauma appears to activate ever, other eye problems or underlying conditions the eruptions of blisters and may be as inconse- (such as RETINOPATHY of diabetes) can affect the quential as rubbing the eye or the irritation such quality of vision. Many people do need eyeglasses as occurs with exposure to environmental particu- after cataract extraction, as the IOL does not lates such as pollen and dust. Some people first adjust for focus as does a natural lens. It is impor- experience outbreaks of cicatricial pemphigoid fol- tant to see the ophthalmologist for follow-up and lowing eye operations such as CATARACT EXTRACTION routine eye care as recommended. AND LENS REPLACEMENT or BLEPHAROPLASTY. See also AGE-RELATED MACULAR DEGENERATION The diagnostic path includes laboratory tests to (ARMD); BULLOUS KERATOPATHY; HYPEROPIA; MYOPIA; assess the levels of antibodies in the blood, partic- PRESBYOPIA; SMOKING AND HEALTH; SURGERY BENEFIT ularly IMMUNOGLOBULIN G (IGG) and IMMUNOGLOBIN A AND RISK ASSESSMENT. (IGA), the antibodies most closely associated with cicatricial pemphigoid. Treatment focuses on chalazion A painless, hard nodule that arises reducing BLISTER formation and minimizing scar- from a gland (meibomian or sebaceous) along the ring, typically by taking oral CORTICOSTEROID MED- edge of the eyelid, the result of glandular secre- ICATIONS or IMMUNOSUPPRESSIVE MEDICATIONS. As with tions that granulate. A chalazion may extend deep other AUTOIMMUNE DISORDERS, cicatricial pem- into the structure of the eyelid. A chalazion some- phigoid tends to be chronic and recurrent. The times forms at the site of a recurrent HORDEOLUM persistent irritation can result in damage to the (an infected eyelid SEBACEOUS GLAND, also called a cornea that causes VISUAL IMPAIRMENT and, when stye). Often a small chalazion will go away on its severe, results in blindness. own, without treatment. Moist heat applied to the See also ANTIBODY; CONJUNCTIVITIS; CORNEAL eyelid helps dissolve the granulated material and TRANSPLANTATION; ECTROPION; HUMAN LEUKOCYTE ANTI- draw it from the gland. Because of the risk of scar- GEN (HLA). 80 The Eyes color deficiency A VISION IMPAIRMENT in which nafil (Viagra) can temporarily intensify the per- the ability to distinguish certain, and rarely all, ception of blue. colors is impaired. Color deficiency represents a See also VISION HEALTH; VISUAL ACUITY. shortage of normal cones, the specialized cells on the RETINA that detect color. Cones contain photo- conjunctivitis An INFLAMMATION of the conjunc- sensitive chemicals that react to red, green, or tiva, or mucous tissue that lines the inside of the blue. The most common presentation of color eyelids. There are many causes for conjunctivitis, deficiency, accounting for about 98 percent of commonly called pink EYE, including INFECTION color deficiency, is red/green deficiency, in which (bacterial, viral, or fungal) and contact contamina- the person cannot distinguish red and green. A tion such as due to pollen or substances in the air small percentage of people cannot distinguish blue or on the fingers that irritate the tissues. Infectious and yellow. Rarely, a person sees only in shades of conjunctivitis is highly contagious and very com- gray. mon, especially in children. Symptoms include Color perceptions occur when lightwaves of certain frequencies (lengths) activate the photo- • red, swollen conjunctiva and sclera (inner eye- chemicals in cones that are sensitive to the fre- lids and the “white” of the eye) quency. The BRAIN interprets the varying • itchy or scratchy sensation intensities and blends of the photochemical responses. Color deficiency occurs when the cones • thick, yellowish discharge that crusts that perceive one of the three primary colors (red, • PHOTOPHOBIA (sensitivity to light) green, blue) do not function properly. The most common test for color vision and color The doctor can usually diagnose conjunctivitis deficiency is a series of disks that contain dots of from its appearance. Typical treatment is applica- color in random patterns with a structured pattern tion of an antibiotic medication in ophthalmic of differing color within the field. The structured preparation (drops or ointment). Most conjunc- pattern may be a number (most commonly) or an tivitis dramatically improves with 48 hours of ini- object. There is no treatment to compensate for tiating treatment, though symptoms may resolve color deficiency. People who are color-deficient gradually over 10 to 14 days, and does not require learn to accommodate the deficiency through further medical attention. The doctor may culture mechanisms such as memorizing the locations of the discharge when there is reason to suspect colored objects (such as the sequence of lights in a CHLAMYDIA or GONNORHEA is the cause, or when traffic signal) and by making adaptations in their symptoms do not improve with treatment. Warm, personal environments. A person may have friends moist compresses help relieve discomfort and clear or family members sort clothing by color, for exam- away the discharge. Frequent HAND WASHING helps ple, and label the color groups. Some people who prevent spreading the infection. Untreated con- have mild color deficiency experience benefit from junctivitis, particularly when chlamydia or gonor- devices such as colored glasses and colored contact rhea is the infectious agent, can cause permanent lenses that filter the lightwaves that enter the EYE. A damage to the CORNEA, which results in VISUAL yellow tint may improve blue-deficient color IMPAIRMENT or blindness. vision, for example. See also ALLERGIC CONJUNCTIVITIS; ANTIBIOTIC MED- Most color deficiency is an X-linked genetic ICATIONS; BACTERIA; FUNGUS; SEXUALLY TRANSMITTED 1 MUTATION, affecting about 8 percent of men and ⁄2 DISEASE (STD) PREVENTION; VIRUS. percent of women. Color deficiency may also develop with AGE-RELATED MACULAR DEGENERATION cornea The transparent portion of the sclera, the (ARMD), RETINOPATHY, neurologic disorders such as EYE’s outer layer. The cornea functions as a win- MULTIPLE SCLEROSIS, and HEAVY-METAL POISONING such dow to allow light to enter the eye and is the first as lead or mercury. Antimalarial drugs can cause point of refraction (bending lightwaves to focus permanent changes in the RETINA that affect color them on the RETINA). Irregularities in the surface of vision; the ERECTILE DYSFUNCTION medication silde- the cornea can distort refraction, resulting in corneal transplantation 81

ASTIGMATISM. Though the cornea has no BLOOD ves- The ophthalmologist can identify a corneal sels it has numerous NERVE endings that make it injury with FLUORESCEIN STAINING, a simple and pain- highly sensitive. Because it is the outermost por- less procedure. Any areas of injury on the cornea tion of the eye, the cornea is also highly vulnera- absorb the fluorescein dye, causing them to glow ble to injury. green under blue light. Serious injuries to the For further discussion of the cornea within the cornea, or embedded foreign objects, may require context of ophthalmologic structure and function immediate surgery to minimize loss of vision. please see the overview section “The Eyes.” Treatment for injuries that affect only the surface of See also CORNEAL INJURY; CORNEAL TRANSPLANTA- the cornea may include ophthalmic ANTIBIOTIC MED- TION; LENS; REFRACTIVE ERRORS. ICATIONS (drops or ointment) and patching of the affected eye. Protective eyewear, worn whenever corneal injury Lacerations, punctures, and blunt there is the potential for particles or objects to strike trauma to the CORNEA. Because of its position, the eye, helps prevent corneal injuries. somewhat protruding at the front of the EYE, the See also CORNEAL TRANSPLANTATION; TRAUMA TO cornea is at risk for damage that can jeopardize THE EYE. vision. corneal transplantation The replacement of a Corneal injuries require immediate diseased CORNEA with a healthy donor cornea. In medical attention. Any puncture or the United States, ophthalmologists perform more penetrating wound to the eye is a med- than 45,000 corneal transplantations each year; ical emergency. Loosely patch both eyes up to 90 percent of people who receive trans- to minimize eye movement. planted corneas experience restored vision; suc- cess depends on the reason for the transplant. Dust, dirt, pollen, and other particulates in the Ophthalmologists may recommend corneal trans- air can scratch the surface of the cornea. Particles plantation to treat: that adhere to the inside of the upper eyelid or objects that slash across the cornea before the eye- • BULLOUS KERATOPATHY lid reflexively closes may cause lacerations (cuts) • KERATOCONUS to the cornea. Though the cornea has no blood vessels and thus cannot bleed, it has numerous • KERATITIS nerve endings that unmistakably sound the alert • significant CORNEAL INJURY when injury occurs. Injury to the cornea also can diminish VISUAL ACUITY. Puncture or penetrating Donor corneas are harvested within a few injuries can destroy the cornea and expose the hours of death and can be preserved for up to 14 inner eye to traumatic damage as well as days. Current practice does not employ blood type INFECTION. Even minor ABRASIONS and lacerations or tissue type matching for corneal transplanta- can cause temporary vision impairment as well as tion, though some studies suggest matching the present the risk for infection. Loss of the eye is blood type of donor and recipient reduces the risk possible when a significant penetrating wound for rejection. allows the inner contents of the eye to escape. Symptoms of corneal injury include CORNEA DONATION • discomfort ranging from a scratchy sensation to Nearly anyone can donate his or her corneas after death. There is no cost to the donor. An eye frank PAIN bank coordinates the harvesting, testing, storage, • PHOTOPHOBIA (sensitivity to light) and dispensing of donated corneas. Many states • excessive tearing incorporate organ donor authorization with dri- • inability to keep the eye open ver’s licenses. People should tell family members that they wish to donate their corneas. • blurred or distorted vision 82 The Eyes

Corneal transplantation surgery takes place corrective lenses Eyeglasses or contact lenses with a local anesthetic to numb the eye and an that alter the focal point of the lightwaves enter- intravenous sedative medication for relaxation ing the EYE to correct REFRACTIVE ERRORS of vision, and comfort. The operation takes 45 to 60 min- including HYPEROPIA (farsightedness), MYOPIA (near- utes. From the donor cornea, the ophthalmologist sightedness), ASTIGMATISM (blurred or distorted uses a trephine, a device that cleanly punches out vision), and PRESBYOPIA (age-related hyperopia). a buttonlike segment of the cornea’s center. Using The eye’s natural focusing structures, the CORNEA a surgical microscope, the ophthalmologist then and the LENS, gather lightwaves and refract (bend) removes a similarly shaped segment from the dis- them toward their centers. The cornea refracts the eased cornea and places the donor button in its lightwaves first. The lens, which can thicken or place. Very fine suture, sometimes thinner than a flatten to refine its focal efforts, refracts the some- human hair, secures the donor corneal button in what focused lightwaves that come to it from the position and remains in the eye for three months cornea. In normal vision, this sequence results in to one year. The ophthalmologist often removes the focal point of the lightwaves striking the the sutures a few at a time as HEALING progresses, RETINA. using an ophthalmic anesthetic to numb the When refractive errors exist the focal point falls affected eye, depending on the rate of vision in front of or behind the retina, resulting in improvement. Some sutures may remain in place blurred images. Corrective lenses add a third level indefinitely. of refraction to compensate for the error, bending Full recovery typically takes about a year. Some the lightwaves before they enter the cornea to people will have ASTIGMATISM and require CORREC- realign their focal point. The direction of refrac- TIVE LENSES following corneal transplantation, tion depends on the refractive error: resulting from irregularities in the shape of the cornea that develop during healing. Corneal trans- • In myopia, the focal point falls short of the plantation may correct another VISION IMPAIRMENT retina. A lens that corrects for myopia bends such as HYPEROPIA (farsightedness) or MYOPIA (near- the lightwaves inward, narrowing the span of sightedness) because the OPERATION changes the light as it enters the cornea to lengthen the shape of the cornea. focal point. Such a lens is thicker at the edges The most common complication of corneal than in the middle (concave); it is a minus transplantation is rejection of the transplanted spherical correction. cornea, which occurs overall in about 15 percent • In hyperopia, the focal point extends beyond of corneal transplantations. Rejection is most the retina. A lens that corrects for hyperopia likely to take place in the first two years after the bends the lightwaves outward, broadening the operation. Early detection and prompt treatment span of light as it enters the cornea to shorten with ophthalmic CORTICOSTEROID MEDICATIONS can the focal point. Such a lens is thicker in the reverse the rejection process. Signs of rejection center than at the edges (convex); it is a plus include spherical correction. • In astigmatism, irregularities in the surface of • diminished VISUAL ACUITY the lens cause a second focal point. A lens that • PAIN corrects for astigmatism refracts along a specific • redness of the eye axis, realigning the lightwaves. This is a cylin- der correction. • PHOTOPHOBIA (sensitivity to light) Corrective lenses can, and often do, combine Other complications that can occur include spherical and cylindrical corrections. A multifocal INFECTION and bleeding within the eye. lens further incorporates a correction for presby- See also ORGAN TRANSPLANTATION; PHOTOTHERAPEU- opia in the form of a bifocal, trifocal, or progres- TIC KERATECTOMY (PTK). sive lens. The bottom of the lens is a plus section, corrective lenses 83 added to the corrective prescription, that accom- lenses in use today: gas permeable (hard) and modates the limited ability of the lens to focus on hydrophilic (soft). Gas-permeable contact lenses near objects (such as when reading). float on a layer of tears over the center of the cornea and often are the contact lens of choice to Eyeglasses correct for moderate to significant astigmatism as Eyeglasses are plastic resin or polycarbon, and less well as KERATOCONUS, a condition in which the commonly glass, lenses ground to the thicknesses cornea’s center bulges outward. Gas-permeable and shapes necessary to achieve the desired lenses also can correct for mild to moderate refractive specifications. Because eyeglasses are myopic and hyperopic refractive errors. Made of external to the eye, they can correct for a broad rigid polymers of fluorocarbon and polymethyl range of refractive errors and are the most com- methacrylate, gas-permeable lenses allow oxygen mon means of refractive correction. Eyeglasses molecules to pass through but do not absorb mois- also can contain tints and dyes that change their ture from the eye. Hydrophilic contact lenses color; some have additives that provide protection cover the entire cornea and can correct for mild to from ultraviolet light. About 85 percent of people moderate myopia and hyperopia. Soft and flexi- who have refractive errors of vision wear eye- ble, hydrophilic lenses contain a high percentage glasses to correct them. of water and draw additional moisture from the Bifocal and trifocal eyeglasses have a clear shift tears to remain hydrated. A special kind of (sometimes visible as a line on the lens) to the hydrophilic lens, the toric lens, is necessary to cor- presbyopic correction; a progressive lens transi- rect for astigmatism. A toric lens has varying tions to the presbyopic correction. Reading glasses thicknesses that compensate for corneal irregulari- such as those available without an eye care practi- ties to correct refraction. tioner’s prescription, are magnifying lenses that Contact lenses can incorporate correction for enlarge close objects, requiring the lens to make moderate presbyopia, though this tends to be a less of an adjustment to bring them into focus. less satisfactory approach than eyeglasses. There How well reading glasses work depends on are two methods for accommodating presbyopia whether there are refractive errors that remain with contact lenses: progressive or bifocal lenses uncorrected. With aging, most people develop at and monovision. Progressive or bifocal contacts least a small degree of astigmatism, which can function much the same as progressive or bifocal result in blurred or distorted images not related to eyeglasses, with the lower portion of the lens con- presbyopia. taining the presbyopic correction. Because contact The primary risk of wearing eyeglasses is trau- lenses shift position on the eye with blinking and matic injury due to a blow that strikes the glasses. when the wearer alters the angle of the head The energy of such a blow concentrates initially at (such as when lying down), the presbyopic correc- the contact points on the NOSE. The frame may tion may not remain in an effective position. break, causing lacerations to the face. Of more sig- Monovision takes the approach of modifying the nificant consequence is a blow that breaks the BRAIN’s interpretation of visual signals. One eye, lens, which can result in vision-threatening injury usually the dominant eye, wears a contact lens to the eye. Polycarbonate lenses have the highest with the refractive correction. The other eye wears inherent shatter resistance; plastic resin and glass a contact lens with the presbyopic correction. The lenses should have shatter-resistant coatings or brain learns to distinguish which signals to inter- additives. People who engage in physical activities pret, accepting those from the dominant eye dur- such as ball sports should wear polycarbonate eye- ing normal visual activities and those from the glasses or custom protective eyewear. other eye when reading or doing close-focus work. Contact Lenses The primary risks of wearing contact lenses are Contact lenses fit directly onto the eye, covering damage to the cornea and INFECTION. Even the cornea. There are two basic kinds of contact hydrophilic lenses can irritate the cornea and 84 The Eyes cause corneal ABRASIONS, particularly in dusty, minus or plus, according to the direction the cor- windy, or dry environmental conditions. Contact rection shifts the focal point. For example, the fol- lenses tend to accumulate protein deposits that lowing prescription corrects for myopia and cause irritation. Most hydrophilic lenses are dis- astigmatism: posable, so frequent replacement helps minimize OD – 5.75 + 0.50 164 this as a problem. The optician may need to clean OS – 6.00 +1.75 115 or gently grind the surface of gas-permeable lenses to clear away deposits. Contact lens hygiene, This prescription denotes different refractive including diligent HAND WASHING before handling corrections for the right eye (OD) and left eye lenses and storing lenses in the appropriate disin- (OS). The minus diopter is the spherical correction fectant solution, is essential. for the myopia; the plus diopter is the cylindrical correction for the astigmatism, and the last num- Reading a Corrective Lens Prescription ber is the axis position for the cylindrical correc- Optometrists and ophthalmologists measure tion. A lens with a strong correction may also refractive errors in diopters, a representational include an adjustment that tilts the lens to alter its scale of the distance in front of or behind the eye’s optical center, the prism, allowing a thinner lens lens the focal point of lightwaves entering the eye to deliver the same corrective power or to accom- must shift to allow the light waves to clearly focus modate a significant difference in the refractive on the retina. The larger the diopter number, the correction for each eye (anisometropia). more the lens refracts, or bends, the light. A cor- See also REFRACTION TEST; REFRACTIVE SURGERY; rective lens prescription represents the diopter as VISION IMPAIRMENT. D

dacryocystitis INFLAMMATION of the lacrimal dacryostenosis Narrowing of the lacrimal (tear) (tear) ducts, typically the nasolacrimal ducts in the duct, usually congenital, that blocks the flow of corners of the EYE near the NOSE. Dacryocystitis tears. An infant does not produce a great volume develops when there is a blockage of the lacrimal of tears during the first few weeks to months after duct, which may result from DACRYOSTENOSIS (nar- birth, so the doctor may not suspect or diagnose rowing of the lacrimal duct), INFECTION, or chronic dacryostenosis until the infant is three to four irritation such as might occur with ALLERGIC RHINI- months of age. The most common symptom is TIS or ALLERGIC CONJUNCTIVITIS. Dacryocystitis can be tears that overflow the eye and run down the face acute (of sudden onset) or chronic (recurrent or (epiphora). Most infants outgrow dacryostenosis long-standing). It also can be congenital (the by age six months, so doctors tend to take an result of defects of the lacrimal gland and duct approach of watchful waiting. When dacryosteno- structures) or acquired. Most people who have sis persists, the doctor may dilate the lacrimal duct acquired dacryocystitis are over age 65. (under anesthetic) to gently stretch and enlarge Common symptoms include the opening for tears to pass unimpeded. Untreated dacryostenosis can result in frequent • redness and swelling between the eye and the episodes of DACRYOCYSTITIS (infected lacrimal ducts) bridge of the nose in adulthood. Appropriate treatment can com- • rhinitis (runny nose) pletely resolve dacryostenosis. See also INFECTION; ORBITAL CELLULITIS. • PAIN • overflowing tears • FEVER when an infection is present dark adaptation test A test that assesses the ability to see in a dimly lighted environment. The doctor can typically diagnose dacryocystitis There are several ways to perform a dark adapta- based on its presentation. Dye tests, in which tion test. One of the most common is to have the the doctor places a special dye in the eye and person sit in a dimly lit room. The examiner watches to see whether the dye discolors nasal shines a light into the EYE, gradually increasing the discharge, help identify the extent of blockage light’s intensity until the person reports seeing the causing the inflammation. Treatment includes light. The examiner notes the light’s intensity and ANTIBIOTIC MEDICATIONS when there is an infection, the length of time it takes for the light to become or procedures to dilate the lacrimal duct when noticeable. Depending on the reason for the test, there is no infection. Sometimes surgery is neces- the examiner may direct the light to different sary to correct dacryostenosis or other structural parts of the RETINA to test the responsiveness of the defects. Appropriate treatment resolves the dacry- rods (the cells responsible for low-light vision). A ocystitis. decrease in dark adaptation response is normal See also BLEPHARITIS; EYE PAIN; OPERATION; ORBITAL with aging as the photochemical reactions in the CELLULITIS. eye slow.

85 86 The Eyes

See also AGING, VISION AND EYE CHANGES THAT dry eye syndrome A condition in which the OCCUR WITH; ELECTRORETINOGRAPHY; NIGHT BLINDNESS; lacrimal (tear) glands do not produce enough tears RETINITIS PIGMENTOSA; RETINOPATHY. or the tears evaporate too quickly, causing the EYE to become dry and irritated. Dry eye syndrome diplopia The medical term for double vision, a has numerous causes, the most common of which circumstance in which a person perceives a single are aging, medication side effects, and extended object as a two distinct images. Diplopia can be exposure to a dry or dusty environment. People vertical (images one above the other) or horizon- who work in occupations that require close focus, tal (images beside each other). Diplopia that is such as with computers or assembly-line tasks, present when using both eyes and goes away also may develop dry eyes as a result of insuffi- when covering one EYE is binocular; diplopia that cient blinking. Dry eyes also may accompany persists even when one eye is covered is monocu- autoimmune conditions such as SYSTEMIC LUPUS lar. Each has different clinical implications. ERYTHEMATOSUS (SLE), RHEUMATOID ARTHRITIS, and Numerous health conditions can cause diplopia or SJÖGREN’S SYNDROME. Cigarette smoking exacer- have diplopia among their symptoms. bates dry eye syndrome. The symptoms of dry eye syndrome include Causes of Causes of redness, itching, and the sensation of grit in the Monocular Diplopia Binocular Diplopia eyes. The diagnostic path targets identifying the ASTIGMATISM BRAIN injury (traumatic or underlying cause when possible. ANTIHISTAMINE CATARACT STROKE) MEDICATIONS, antihypertensive medications, ANTIDE- DRY EYE SYNDROME BRAIN TUMOR PRESSANT MEDICATIONS, and medications to treat KERATOCONUS DIABETES PARKINSON’S DISEASE commonly cause dry eyes as a PTERYGIUM cranial NERVE disorders SIDE EFFECT; sometimes switching to a different RETINOPATHY GRAVES’S OPHTHALMOPATHY medication reduces eye dryness and irritation. STRABISMUS MULTIPLE SCLEROSIS Treatment is frequent use of artificial tears or MYASTHENIA GRAVIS restasis drops and remedying any identifiable cause when possible. The ophthalmologist may The diagnostic path begins with basic OPHTHALMIC treat persistent dry eye syndrome with lacrimal EXAMINATION and NEUROLOGIC EXAMINATION. The find- plugs (also called punctal plugs), tiny segments of ings of these exams determine the direction and acrylic that become soft and gelatinous when nature of further testing. As diplopia is a symptom inserted into the lacrimal ducts. These plugs slow rather than a condition, treatment targets the the drainage of tears from the eye. Some recent underlying cause. In degenerative disorders such as studies suggest that increasing dietary intake of MULTIPLE SCLEROSIS and MYASTHENIA GRAVIS, diplopia essential fatty acids, notably linoleic and gamma- may persist or worsen as the condition progresses. linolenic acids, improves the eye’s ability to pro- For monocular diplopia, patching the affected eye duce tears. may alleviate the double image. See also AGING, VISION AND EYE CHANGES THAT See also AMBLYOPIA; CRANIAL NERVES; STRABISMUS; OCCUR WITH; ALLERGIC CONJUNCTIVITIS; ALLERGIC RHINI- VISION IMPAIRMENT. TIS; BLEPHARITIS; CONJUNCTIVITIS. E ectropion Loss of elasticity or control of the eye- electroretinography A test that measures the lid, usually the lower eyelid, that causes it to sag electrical activity of the RETINA’s rods and cones in away from the EYE. Ectropion allows tears to over- response to light stimulation. The ophthalmologist flow the lid rather than remaining in the eye. It places anesthetic drops in the EYE to numb it, then also fails to protect the eye, and especially the attaches an electrode to the surface of the CORNEA. CORNEA, permitting dryness and exposure to envi- The electrode detects electrical impulses on the ronmental particles that create irritation and pos- retina when the ophthalmologist flashes a beam of sibly injury to the cornea and sclera (“white” of light onto the retina, and sends signals to the elec- the eye). Common causes of ectropion include troretinograph machine. An electroretinogram is the recording the machine makes of the retina’s • aging responses. Electroretinography helps diagnose dis- orders of the retina such as RETINAL DETACHMENT • damage to the nerves that control the eyelids and RETINITIS PIGMENTOSA. • CICATRICIAL PEMPHIGOID See also DARK ADAPTATION TEST; RETINOPATHY; SLIT LAMP EXAMINATION. Ectropion is a common symptom of BELL’S PALSY, a temporary paralysis of one side of the face entropion Deformity of the eyelid in which the that results from INFLAMMATION of the seventh cra- lip of the lid, including the eyelashes, curls inward nial NERVE (facial nerve), and also may accompany toward the EYE. Scarring that results from CICATRI- neurologic disorders such as PARKINSON’S DISEASE CIAL PEMPHIGOID (an AUTOIMMUNE DISORDER in which and MULTIPLE SCLEROSIS. painful blisters repeatedly form on the insides of With ectropion the eye feels irritated and the eyelids) or recurrent CONJUNCTIVITIS (INFLAMMA- scratchy. Tear production becomes excessive as the TION or INFECTION of the inner lining of the eyelids) eye attempts to lubricate and protect itself, and is a common cause of entropion. Entropion may tears typically run over the lip of the lid and onto also develop for unknown reasons (idiopathic). the cheeks. The doctor can diagnose ectropion The ophthalmologist can diagnose entropion by its based on its appearance. Treatment is typically presentation. The irritation of the lid and lashes surgery to tighten the lid structure to permit the against the surface of the eye is painful and can lid to stay against the eye. Whether the ectropion cause significant damage to the CORNEA, resulting recurs depends on the underlying cause. in VISION IMPAIRMENT and perhaps the need for Untreated ectropion may result in extensive dam- CORNEAL TRANSPLANTATION. Treatment seeks to age to the surface of the eye and cornea, including relieve the irritation. In mild entropion, lubricat- INFECTION, that interferes with vision and the ing eye drops may be sufficient to protect the eye. health of the eye. Moderate to severe entropion requires surgery to See also AGING, VISION AND EYE CHANGES THAT restore the eyelid to its appropriate structure. OCCUR WITH; CONJUNCTIVITIS; CORNEAL INJURY; CRANIAL Once corrected, entropion usually does not recur. NERVES; ENTROPION; KERATITIS. See also CORNEAL INJURY; ECTROPION; KERATITIS.

87 88 The Eyes enucleation Surgical removal of a cancerous EYE help relieve the irritation until the inflammation or a severely diseased or damaged eye. The OPERA- subsides. This is usually the only treatment neces- TION, performed under general ANESTHESIA, takes sary. Some studies suggest a correlation between about an hour. After removing the eye, the surgeon episcleritis and hormonal shifts such as occur with places an implant to fill the shape of the socket and the MENSTRUAL CYCLE or MENOPAUSE. Episcleritis is provide a means of attaching a PROSTHETIC EYE. A three times more common in women than men. pressure dressing stays in place over the eye orbit Episcleritis does not affect vision or result in any for one to two days to minimize swelling and allow long-term effects on the health of the eye. the implant to become firmly rooted in the con- See also CONJUNCTIVITIS; KERATITIS; SCLERITIS. junctival tissue. During this time it is common as well as frightening for people to have difficulty exophthalmos Bulging outward of the EYE, opening the other eye, as the eyes are accustomed sometimes called poptosis. Most exophthalmos to functioning together. Once the bandage comes results from Graves’s disease and is a classic symp- off and the eyelid of the operated eye is free to tom of this form of HYPERTHYROIDISM. Thyroid- move, the eyelid for the unoperated eye resumes related exophthalmos results from swelling of the normal functioning. Complete HEALING takes about tissues around the eye and within the orbit that six weeks, during which time it is necessary to place develops in reaction to the high levels of thyroid anti-inflammatory and antibiotic drops in the oper- HORMONE present in the circulation. Other causes ated eye socket to keep swelling and the risk for of exophthalmos include ORBITAL CELLULITIS, the INFECTION to a minimum. autoimmune disorder Wegener’s granulomatosis, Though the operation is uncomplicated and the and FRACTURE of the facial or orbital bones that body quickly heals following the surgery, enucle- push the eye out of place. Less common causes of ation can be a difficult procedure for people to exophthalmos include tumors of the eye, OPTIC accommodate emotionally. Even when the eye NERVE, or BRAIN that protrude into the orbital has been visionless for a long time, the prospect of socket and ANEURYSM (ballooning of the arterial losing the eye troubles many people. The modern wall) of the internal carotid ARTERY, a branch of prosthetic eye is typically such a close match for which runs behind the eye. Exophthalmos can the remaining eye that it is unapparent to other affect one eye (unilateral) or both eyes (bilateral), people. Once the operative site heals, the eye orbit and when bilateral can affect one eye more promi- (socket) and implant require little care or atten- nently than the other. tion beyond cleaning the external eyelid area for hygienic purposes. Exophthalmos can cause significant and See also ANTIBIOTIC MEDICATIONS; RETINOBLASTOMA; permanent vision impairment, and SURGERY BENEFIT AND RISK MANAGEMENT; VISION requires prompt treatment. IMPAIRMENT. episcleritis INFLAMMATION of the episclera, the The diagnostic path begins with an OPHTHALMO- membrane that covers the sclera (fibrous outer LOGIC EXAMINATION and blood tests to assess thyroid layer, the “white,” of the EYE). Most episcleritis is function. When Graves’s disease or hyperthy- idiopathic (occurs for unknown reasons), though roidism is the cause, treatment to restore appro- the condition sometimes accompanies AUTOIMMUNE priate levels of thyroid hormones often though DISORDERS such as RHEUMATOID ARTHRITIS and not always returns the eye to its normal position. REITER’S SYNDROME. Episodes are self-limiting Persistent exophthalmos may prevent the eyelids though may recur over time, with each episode of from closing over the eye, exposing the CORNEA to inflammation generally lasting 7 to 10 days. excessive dryness and potential trauma. Untreated Symptoms may include mild irritation and red- exophthalmos results in VISION IMPAIRMENT that can ness, and occasionally a nodule (bump) on the progress to blindness. surface of the sclera. The doctor can diagnose epis- See also AUTOIMMUNE DISORDERS;GRAVES’S OPH- cleritis by its appearance. Lubricating eye drops THALMOPATHY. eye pain 89 eye The organ of vision. The paired eyes work in detect color (cones) and brightness (rods). These coordination to present NERVE impulses the BRAIN cells convert the light to nerve impulses that con- interprets as dimensional (stereovisual) images. verge at the back of the retina at the optic disk, The function of sight requires close integration their portal to the optic nerve. The optic nerve among the structures of the eye, the neurologic sys- conveys the signals to the brain, which interprets tem, and the muscular system. Each eye is a fluid- them as images. 1 filled, elongated globe of fibrous tissue, about ⁄4 inch from front to back and 1 inch from top to bot- COMMON CONDITIONS OF THE EYE tom and side to side, contained within the protec- AMBLYOPIA ASTIGMATISM tive cavity of the orbital socket in the skull. The BLEPHARITIS CATARACT OPTIC NERVE, the second cranial nerve, provides a CONJUNCTIVITIS CORNEAL INJURY direct pathway from the back of the eye to the DRY EYE SYNDROME EYE STRAIN brain. Six muscles move each eye up and down, FLOATERS GLAUCOMA from side to side, and in rotation. These muscles HORDEOLUM HYPEROPIA direct the eye toward objects within the VISUAL FIELD ISCHEMIC OPTIC NEUROPATHY KERATITIS and hold the eyes steady. KERATOCONUS MYOPIA The process of vision begins when lightwaves NIGHT BLINDNESS PRESBYOPIA enter the eye through the CORNEA, a transparent RETINAL DETACHMENT RETINITIS PIGMENTOSA portion of the eye’s tough outer layer, the sclera. RETINOPATHY STRABISMUS The cornea’s convex front surface initially refracts VISION IMPAIRMENT the lightwaves for preliminary focusing. The cornea is soft and flexible but fixed; it does not For further discussion of the eye within the adjust or move. The LENS, a transparent and flexi- context of ophthalmologic structure and function ble convex disk behind the cornea, further refracts please see the overview section “The Eyes.” the lightwaves. Tiny muscles at the edge of the See also AGING, VISION AND EYE CHANGES THAT lens, the ciliary muscles, cause the lens to thicken OCCUR WITH; CRANIAL NERVES. or flatten to adjust the degree of refraction for optimal focus. The resulting light pattern strikes eye pain Sensations discomfort involving the EYE the RETINA, activating the specialized cells that and its supporting structures. Eye PAIN may vary

COMMON CAUSES OF EYE PAIN Quality of Pain Possible Causes Medical Attention Required itchy or scratchy sensation DRY EYE SYNDROME, ALLERGIC self-care such as artificial tears or CONJUNCTIVITIS, dirty contact ANTIHISTAMINE MEDICATIONS; timely doctor’s lenses, EYE STRAIN assessment if symptoms persist after self-care efforts to relieve them burning and PHOTOPHOBIA, may CONJUNCTIVITIS, HORDEOLUM, prompt doctor’s assessment; infections require include discharge CHALAZION, BLEPHARITIS, KERATITIS, antibiotic medications DACRYCYSTITIS, ENTROPION burning, photophobia, excessive BULBOUS KERATOPATHY, CICATRICIAL immediate medical attention tearing, visible blisters on surface PEMPHIGOID, corneal abrasion of the eye sharp, deep, or intense pain that may ORBITAL CELLULITIS, trauma to eye, medical emergency increase with, or prevent, eye GLAUCOMA, optic neuritis, chemical movement or flash BURNS 90 The Eyes from scratchy irritation to intense and debilitating eye strain The sensation of tiredness and irrita- pain. Much eye pain in the form of burning and tion of the eyes, often accompanying long periods itching arises from minor and treatable causes that of time involved in performing the same task such affect the structures around the eye rather than as reading, computer work, watching television, the eye itself. Eye pain that is throbbing, stabbing, playing video games, and assembly work. EYE deep, or accompanies visual disturbances may strain generally results from overuse of the mus- suggest conditions such as GLAUCOMA. cles that move the eyes. The overuse tires the muscles, which become less responsive to the Eye pain that is sudden and severe, focusing needs of the eyes. The difficulty generates accompanies partial or complete loss of temporary vision disturbances such as blurring, vision, prevents movement of the eye, and may also cause muscle tension headaches. or follows TRAUMA TO THE EYE or face Insufficient blinking, which causes the eyes to requires emergency medical attention. become dry and irritated, often accompanies the When there is the possibility of pene- overuse. trating eye injury, loosely patch both These measures can help relieve eye strain: eyes to minimize movement. • Blink frequently. The diagnostic path begins with careful exami- • Use artificial tears to improve the moisture con- nation of both eyes, which may include OPHTHAL- tent of the eyes. MOSCOPY, FLUORESCEIN STAINING when the doctor • Make sure lighting is of the appropriate inten- suspects CORNEAL INJURY, TONOMETRY to measure the sity and placement. pressure inside the eye, and SLIT LAMP EXAMINATION for further assessment of the RETINA and other • Reduce glare and reflection. structures of the inner eye. The doctor may place • Look away from close tasks every 10 to 15 min- an anesthetic medication (numbing eye drops) in utes to focus on objects in the distance. the eye to determine whether the pain is coming from the surface of the eye, in which case the pain • Wear reading glasses or CORRECTIVE LENSES to will go away, or from within the eye, in which accommodate PRESBYOPIA. case the pain will persist. Often the doctor will • Wear eye protection when in environments also conduct basic tests of VISUAL ACUITY such as a that are dusty or windy, and when in the sun. SNELLEN CHART reading. People who wear contact lenses should remove Contrary to popular belief, eye strain (such as them at the first sign of discomfort. Treatment for reading in dim light) does not cause permanent eye pain targets the underlying cause. Most minor VISION IMPAIRMENT. However, eye strain may result causes resolve without complications or perma- from undetected vision impairment, such as ASTIG- nent VISION IMPAIRMENT. Causes such as severe MATISM and HYPEROPIA, that affect the eye’s ability corneal injury (BURNS, lacerations), glaucoma, and to focus on near objects. An ophthalmologist or ORBITAL CELLULITIS seriously threaten vision and can optometrist should evaluate eye strain that persists result in permanent and complete vision loss despite efforts to improve the visual environment. without urgent and appropriate treatment. See also ERGONOMICS; HEADACHE; MUSCLE; OCCUPA- See also RETINAL DETACHMENT. TIONAL HEALTH AND SAFETY; VISION HEALTH. F

farsightedness See HYPEROPIA. Floaters may take various shapes and sizes, and typically move around the VISUAL FIELD, changing flashes Visual phantoms that appear as spots of position with blinking or eye movement. Most light. An ophthalmologist should evaluate occur- floaters are harmless, though large floaters may rences of flashes, as they can be symptoms of RETI- interfere with vision. Holding the eye still may NAL DETACHMENT or other conditions affecting the allow the floater to settle to the bottom of the eye, RETINA. Flashes represent stimulation of the rods out of the visual field. A sudden increase in the and cones, the cells of vision carpeting the retina, number of floaters, or floaters that occur in com- that occurs when the gelatinous fluid holding the bination with FLASHES, can signal a retinal tear or retina in place (vitreous humor) moves across RETINAL DETACHMENT. Prompt intervention is neces- them. Because the NERVE signals these cells send to sary to prevent further retinal damage and pre- the BRAIN encode patterns of light, the brain inter- serve vision. Floaters may also indicate UVEITIS. prets messages from them as light. A blow to the Large floaters may remain indefinitely; small head that causes a person to “see stars” has similar floaters may eventually break apart and become effect when it is forceful enough to jostle the vit- absorbed into the vitreous humor. There is no reous humor against the retina. Flashes may treatment for floaters. appear as multiple spots of light, “light showers,” See also VISION IMPAIRMENT; VITREOUS DETACHMENT. or lightning-like streaks. The ophthalmologist typically performs a full fluorescein staining A simple procedure for OPHTHALMIC EXAMINATION to assess the integrity of diagnosing CORNEAL INJURY or foreign objects in the the retina. Prompt treatment is necessary to inter- EYE. The ophthalmologist places a strip of paper vene with a retinal tear or retinal detachment, to containing fluorescein at the edge of the eye. The preserve vision. Isolated flashes of light generally dye rapidly leaches into the tears. Some people are harmless and may occur for various reasons. experience a slight burning sensation when the Lines or waves of light that last 20 to 60 minutes dye washes across the eye for the first time. Blink- are common with migraine headaches and have ing disperses the tears across the CORNEA. With the no significance for vision or the health of the eye. regular room lights turned off, the ophthalmolo- See also FLOATERS; HEADACHE; VISION IMPAIRMENT; gist shines a cobalt blue light on the eye. Any VITREOUS DETACHMENT. breach in the eye’s surface shows as bright green. The tears wash the fluorescein from the eye floaters Fragments of inner EYE material that within a few minutes. float through the vitreous humor, casting shadows See also OPHTHALMIC EXAMINATION; SLIT LAMP against the RETINA as entering light strikes them. EXAMINATION; TRAUMA TO THE EYE.

91 G

glaucoma A serious and progressive EYE condi- sure to increase in the anterior chamber. Increased tion in which the cells at the front of the OPTIC pressure in the chambers puts increased pressure NERVE where it intersects with the RETINA, the reti- on the inner eye, causing intraocular pressure to nal ganglia, die, resulting in vision loss. Early diag- rise. Extreme or extended elevations in intraocu- nosis and treatment can minimize vision loss. lar pressure compress the optic disk, causing nerve Health experts estimate that 5 million Americans cells to die. have glaucoma, though only about 2 million of them know it. Glaucoma is the third-leading cause Acute closed-angle glaucoma requires of blindness in the United States, primarily emergency medical attention. Without because it remains undetected until damage to the immediate treatment, severe to com- optic NERVE becomes significant. Glaucoma plete vision loss can occur within hours becomes more common after age 65, though there of the onset of symptoms. is a congenital form that manifests in early child- hood (congenital glaucoma). Open-angle glaucoma is chronic, progressing Until the late 1990s ophthalmologists perceived over years, and is the most common form of glau- glaucoma to be the exclusive consequence of coma, accounting for about 85 percent. Closed- increased pressure within the eye (INTRAOCULAR angle glaucoma can be acute, with the sudden PRESSURE) that caused the death of retinal ganglia onset of severe symptoms, or chronic with symp- cells. Current understanding of the disease process toms similar to those of open-angle glaucoma. The of glaucoma affirms the death of retinal ganglia function and dysfunction of aqueous humor cells as the cause of damage to the optic nerve, drainage is the dimension of glaucoma doctors though recognizes that numerous factors, intraoc- and researchers understand most clearly, and most ular pressure being only one among them, con- treatment approaches target reducing aqueous tribute to this damage. About 30 percent of people humor production or improving its drainage from who have glaucoma have normal intraocular pres- the eye. Less clear are the other factors that con- sure, and only about 10 percent of people who tribute to death of the retinal ganglia cells and cor- have elevated intraocular pressure have glaucoma. responding destruction of the optic disk. These There are two general forms of glaucoma: open factors are especially significant for the 30 percent angle and closed angle (also called angle-closure). of people who have glaucoma with normal The designations refer to whether the channel intraocular pressure. Researchers are investigating through which aqueous humor drains from the the roles of genetics, autoimmune processes, and eye, called the angle, is open but dysfunctional correlations with conditions such as DIABETES and (open-angle glaucoma) or becomes blocked by the HYPERTENSION (high BLOOD PRESSURE). iris (closed-angle glaucoma). In glaucoma, the drainage angle either malfunctions (open-angle Symptoms and Diagnostic Path glaucoma) or a segment of the iris seals over it The key symptom of chronic glaucoma, open- (closed-angle glaucoma). When the aqueous angle or closed-angle, is the gradual and painless humor cannot properly drain, it causes the pres- loss of VISUAL ACUITY and VISUAL FIELD. Often the 92 glaucoma 93 pattern of progression begins with loss of periph- OPHTHALMIC EXAMINATION including fundus exami- eral (outside) vision. Over time the field of vision nation to assess the condition of the optic disk. becomes increasingly narrow, which people often The ophthalmologist will also conduct a visual describe as “tunnel vision.” Other symptoms acuity test and a peripheral vision test. Other pro- include excessive tearing (especially with close cedures that can help diagnose glaucoma in its focus tasks such as reading), halos around lights at early stages or quantify the extent of damage in night, aching eyes, and headaches. Sudden throb- moderate to advanced glaucoma are ULTRASOUND of bing PAIN in the eye, loss of vision, severe the eye and OPTICAL COHERENCE TOMOGRAPHY (OCT). HEADACHE, halos around lights, and a dilated pupil in the affected eye are symptoms of acute closed- Treatment Options and Outlook angle glaucoma. Acute closed-angle requires emergency measures to relieve intraocular fluid and the accumulation GLAUCOMA SYMPTOMS of aqueous humor. Such measures typically Chronic (Open-Angle or include a combination of procedures to open the Closed-Angle) Acute Closed-Angle drainage angle, ophthalmic medications to lower slow loss of peripheral vision sudden, throbbing PAIN in intraocular pressure, and systemic medications to “blind spots” in the field of the EYE draw fluid from cells (osmotics). The ophthalmol- vision sudden, severe HEADACHE ogist is also likely to administer medications for halos around lights at night sudden restriction or loss pain and to minimize NAUSEA and vomiting. Ongo- teary eyes with close focus of vision ing treatment with glaucoma medications or glau- tasks dilated pupil in affected coma surgery is then necessary. Ophthalmic achiness in the affected eye eye medications (drops, inserts, and ointments) to NAUSEA and vomiting open the drainage angle and lower intraocular pressure are the standards of treatment for chronic Though eye care practitioners routinely use glaucoma of either form, and typically can control TONOMETRY to screen for increased intraocular pres- glaucoma for many years. sure, this test alone is not sufficient to detect glau- Surgery becomes an option to treat glaucoma coma. Detecting glaucoma requires a full that becomes advanced or does not respond to

COMMON GLAUCOMA MEDICATIONS Type of Drug Actions alpha-blockers (apraclonidine, brimonidine)—topical reduce aqueous humor production by slowing function of ophthalmic preparations ciliary processes; increase drainage of aqueous humor beta-blockers (betaxolol, carteolol, levobunolol, reduce aqueous humor production by slowing function of the metipranolol, timolol)—topical ophthalmic preparations; ciliary processes oral products sometimes used carbonic anhydrase inhibitors (brinzolamide, reduce aqueous humor production by blocking the action of the dorzolamide)—topical ophthalmic preparations enzyme necessary for its production, carbonic anhydrase miotics (pilocarpine, carbachol)—topical ophthalmic increase drainage of aqueous humor preparations prostaglandin analogs (latanoprost, travoprost, bimatoprost, increase drainage of aqueous humor via secondary routes unoprostone)—topical ophthalmic preparations 94 The Eyes medication therapy. Surgical treatments for glau- Graves’s ophthalmopathy Changes in the EYE coma include the following: that occur as a result of Graves’s disease, a form of HYPERTHYROIDISM, and occasionally as a result of • For iridotomy, the ophthalmologist uses an other forms of thyroid disease. The most promi- ophthalmologic laser to place a small opening nent feature of Graves’s ophthalmopathy is EXOPH- in the iris. The opening provides another route THALMOS, an outward bulging or protrusion of the of drainage for the aqueous humor and helps eyes that often is the first indication of Graves’s keep the iris from blocking the drainage angle disease. The exophthalmos results from enlarged in open-angle glaucoma. extraocular muscles (the muscles that move the • For trabeculoplasty, the ophthalmologist uses eye) and edema (swelling due to retained fluid) in an ophthalmologic laser to make numerous the tissues around the eye and within the ocular “dots” in the trabecular meshwork—the fanlike orbit (eye socket). This circumstance restricts the network of tiny channels at the end of the ability to move the eyes, particularly upward and angle that disperse the draining aqueous side to side, as well as to close the eyelids. Graves’s humor—to expand its the draining capacity. ophthalmopathy can involve only one eye (unilat- • For trabeculotomy, the ophthalmologist places eral) though most often involves both eyes (bilat- an aqueous shunt, a tiny opening from the eral). Symptoms and consequences range from anterior chamber through the sclera, to allow mild to severe, with about 5 percent of people aqueous humor to drain to the outside of the experiencing substantial loss of vision that may eye. include loss of the eye. Graves’s ophthalmopathy can appear before there are any indications of • For cytophotocoagulation, the ophthalmologist Graves’s disease, at the onset of hyperthyroid uses an ophthalmologic laser to destroy por- symptoms, or months to years after the diagnosis tions of the ciliary processes to reduce aqueous of Graves’s disease. humor production. Graves’s ophthalmopathy presents a significant threat to vision. The swelling in and around the Early diagnosis and treatment offer the best orbit pressures the structures of the eye and can opportunity for minimizing vision loss. It is impor- compress the OPTIC NERVE, which can result in OPTIC tant to diligently follow the directions for using NERVE ATROPHY (the death of cells in the optic glaucoma medications, as glaucoma requires con- NERVE) and permanent VISION IMPAIRMENT. The sistent control. Appropriate treatment can slow external pressure against the eye also raises the the progression of vision loss in most people who pressure inside the eye (INTRAOCULAR PRESSURE), have glaucoma. which can result in GLAUCOMA. The combination of Risk Factors and Preventive Measures exophthalmos and restricted lid movement pre- Age is the most significant risk factor for glau- vents the eyelids from closing completely, which coma; glaucoma is uncommon in people under allows the CORNEA to become dry. The resulting age 40 and about two thirds of people who irritation and INFLAMMATION (KERATITIS) reduces develop glaucoma are over age 65. Glaucoma is VISUAL ACUITY and also exposes the inner eye to more common in people of African American and INFECTION. Though the symptoms that threaten Asian ethnicity and tends to run in families. Glau- vision eventually subside, many of the changes coma also is more likely to develop in people who that result, including exophthalmos and vision have hypertension, ATHEROSCLEROSIS, diabetes, and impairment, are permanent. severe MYOPIA (nearsightedness) and in people Symptoms and Diagnostic Path who take CORTICOSTEROID MEDICATIONS. Prevention The symptoms of Graves’s ophthalmopathy focuses on regular ophthalmic examinations to include detect glaucoma early in its course. See also AGE-RELATED MACULAR DEGENERATION • exophthalmos (sometimes called poptosis) (ARMD); CATARACT; LASER SURGERY; VISION HEALTH. • DIPLOPIA (double vision) Graves’s ophthalmopathy 95

• CONJUNCTIVITIS (inflammation of the inner eye- • ANTIBIOTIC MEDICATIONS to treat bacterial infec- lids) tion of the eyelids (BLEPHARITIS), conjunctiva • diminished visual acuity (blurry or distorted (conjunctivitis), and cornea (keratitis) vision) In the second stage of Graves’s ophthalmopa- • PHOTOPHOBIA (sensitivity to light) thy, the progression of symptoms ends. However, • excessive tearing the changes that have occurred are permanent. Fibrous deposits replace lymphocytes in the eye As these symptoms are distinctive for Graves’s muscles, maintaining their enlargement and con- ophthalmopathy, the doctor often can make the tinuing the exophthalmos. Treatment in this stage diagnosis based on their presentation. Tests of thy- targets minimizing these permanent consequences roid HORMONE levels in the BLOOD confirm Graves’s through surgeries to relieve the pressure within disease, if not already diagnosed. Conventional the orbit (orbital decompression), reduce the size OPHTHALMIC EXAMINATION and SLIT LAMP EXAMINATION of the extraocular muscles (myectomy), and allow the ophthalmologist to assess the status of reconstruct the eyelids so they close completely vision and health of the structures of the eye. A over the eye (BLEPHAROPLASTY). Corneal reshaping COMPUTED TOMOGRAPHY (CT) SCAN helps assess the (keratoplasty) or CORNEAL TRANSPLANTATION may be extent of orbital swelling and compression of the necessary to restore vision when damage to the optic nerve. cornea is extensive. If infection resulted in loss of the eye, the ophthalmologist will place a PROS- Treatment Options and Outlook THETIC EYE. The course of Graves’s ophthalmopathy seems to unfold in two stages, regardless of treatment for or Risk Factors and Preventive Measures status of the underlying hyperthyroidism. The first stage is the acute or active phase, during which Graves’s ophthalmopathy occurs only in conjunc- symptoms emerge. During this stage, which tion with thyroid disorders, nearly always hyper- extends over 18 to 30 months, ophthalmologic thyroidism. It may appear months to several years treatment focuses on reducing pressure on the eye before other clinical indications of hyperthy- and stabilizing vision, and may include roidism, or a comparable time after beginning treatment for hyperthyroidism. Prompt diagnosis • ophthalmic lubricating drops or ointment to and treatment are essential to preserve vision, as keep the cornea hydrated the changes that occur with Graves’s ophthal- mopathy are generally permanent. An ophthal- • patching the eyes at night to protect the mologist should evaluate any changes in the corneas during sleep appearance of the eyes. Regular eye examinations • NONSTEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS) help screen for Graves’s ophthalmopathy as well to reduce inflammation and relieve discomfort as other eye health problems. • CORTICOSTEROID MEDICATIONS to suppress the See also AUTOIMMUNE DISORDERS; BACTERIA; VISION body’s immune response HEALTH. H

hordeolum A bacterial INFECTION of a gland or an extends past the RETINA, causing the images the eyelash follicle along the edge of the eyelid, com- retina registers to be blurred. The refractive error monly known as a stye. A hordeolum causes occurs because the distance from the front to the swelling, redness, PAIN, and a discharge that leaves a back of the eye is shorter than normal. Symptoms crusty layer on the eyelids during sleep. The doctor of hyperopia include can usually diagnose hordeolum by its presenta- tion. BLEPHARITIS (infection of the inside surface of • squinting when reading or doing close work the eyelid) and CONJUNCTIVITIS (infection of the con- • HEADACHE junctiva, the membrane lining the eyelids) may instigate, accompany, or follow hordeolum. The • fatigued eye muscles (aching around the eyes) doctor often chooses to anesthetize the area and • blurred vision when looking at near objects yet lance (make tiny punctures or incisions under ster- clear vision when looking at distant objects ile conditions) the hordeolum to drain its contents and relieve the pressure. Further treatment is oph- CORRECTIVE LENSES (eyeglasses or contact lenses) thalmic ANTIBIOTIC MEDICATIONS, typically in oint- can compensate for hyperopia by altering the focal ment form, applied to the area. Sometimes oral point of lightwaves so it falls directly on the retina. antibiotic medications are also necessary. Warm, They do so by refracting (bending) the lightwaves moist compresses soothe the irritated tissues and outward. REFRACTIVE SURGERY, which permanently help draw out any remaining pus. alters the shape of the CORNEA, can provide refrac- Most hordeola clear up in 7 to 10 days with tive correction for people with mild to moderate treatment and heal without residual conse- hyperopia. Hyperopia sometimes occurs following quences. A hordeolum does not itself cause VISION refractive surgery for MYOPIA (nearsightedness) as IMPAIRMENT, though untreated hordeola can lead to a consequence of overcorrection. Eye profession- significant EYE problems if the infection spreads to als denote refractive corrections in units of meas- other structures of the eye. Some people experi- ure called diopters. For hyperopia, the expression ence recurring hordeola, while others experience of diopter is a positive number. Corrective lenses only a single episode. A hordeolum may also form for hyperopia have a magnifying appearance that the basis for a CHALAZION (painless nodule) to make the eyes look bigger than they are. develop in its place. Hyperopia is less common than myopia, affect- See also BACTERIA; ECTROPION; ENTROPION. ing about 20 to 25 percent of adults. Few people who have hyperopia have greater than +6 hyperopia A refractive error, commonly called diopters of refractive error, so nearly always cor- farsightedness, in which the EYE has difficulty rective measures result in normal VISUAL ACUITY. focusing on near objects. Hyperopia results when See also ASTIGMATISM; PRESBYOPIA; REFRACTIVE the focal point of lightwaves entering the eye ERRORS.

96 I

intraocular pressure The pressure within the EYE as a result of INFECTION, such as CONJUNCTIVITIS that that maintains the eye’s form and structure. Nor- spreads to involve other structures of the eye. Iri- mal intraocular pressure in an adult is 12 to 22 tis also occurs as part of the inflammatory process millimeters of mercury (mm Hg). A device called a in AUTOIMMUNE DISORDERS such as RHEUMATOID tonometer measures intraocular pressure, either ARTHRITIS. The symptoms of iritis include through light contact against the anesthetized eye or via the force of resistance to a puff of air blown • irritation and a “gritty” sensation in the eye against the eye’s surface (a noncontact method • redness of the eye that does not require anesthetic drops). Elevated • PHOTOPHOBIA (sensitivity to bright light) intraocular pressure is called ocular hypertension. Lower than normal intraocular pressure is called • blurry vision ocular hypotension. • excessive tearing Ocular hypertension (greater than 21 mm Hg) is a hallmark sign of GLAUCOMA, an eye condition The ophthalmologist can diagnose iritis based that, if untreated, results in complete loss of on the appearance of the iris and the eye, though vision. Other health conditions that can increase will additionally perform a SLIT LAMP EXAMINATION intraocular pressure include tumors that press to look for involvement of other structures of the against the eye, ORBITAL CELLULITIS, and GRAVES’S eye. Treatment is ophthalmic ANTIBIOTIC MEDICA- OPHTHALMOPATHY. Increased intraocular pressure TIONS (eye drops or ointment) when the ophthal- damages the cells on the front of the OPTIC NERVE mologist suspects bacterial infection and (the retinal ganglia), leading to permanent VISION ophthalmic CORTICOSTEROID MEDICATIONS to reduce IMPAIRMENT. Ophthalmic medications that reduce the inflammation. When the cause of the inflam- intraocular pressure work through various mecha- mation is systemic, the ophthalmologist may pre- nisms, depending on the cause of the increased scribe anti-inflammatory medications such as pressure. corticosteroids or NONSTEROIDAL ANTI-INFLAMMATORY Ocular hypotension, in which the intraocular DRUGS (NSAIDS). Treatment usually resolves the pressure is lower than normal (less than 12 mm symptoms without residual VISION IMPAIRMENT. Hg), characterizes chronic UVEITIS (INFLAMMATION of Untreated or recurrent iritis can have long-lasting the structures of the eye) and of certain tumors of effects on vision, including increased INTRAOCULAR the eye. Ocular hypotension also sometimes PRESSURE. accompanies systemic HYPOTENSION (low BLOOD See also BACTERIA; EPISCLERITIS; GLAUCOMA; KER- PRESSURE) and as a SIDE EFFECT of medications, ATITIS; SCLERITIS; UVEITIS. notably general anesthesia agents. See also OPHTHALMIC EXAMINATION; TONOMETRY; ischemic optic neuropathy Damage to the OPTIC VITRECTOMY; VITREOUS DETACHMENT. NERVE resulting from insufficient blood supply, sometimes called “STROKE” of the optic nerve. iritis INFLAMMATION of the iris, the MUSCLE sur- Ischemic optic neuropathy is occurs most com- rounding the pupil of the EYE. Iritis may develop monly in people over age 55 and causes mild to 97 98 The Eyes complete VISION IMPAIRMENT. There are two forms: Treatment for arteritic ischemic optic neuropa- arteritic, associated with giant-cell arteritis (an thy is CORTICOSTEROID MEDICATIONS to reduce the inflammatory disorder of the arteries that typically INFLAMMATION. Vision loss, however, is irreversible. affects the temporal arteries) and nonarteritic, There are no effective treatments for the nonar- which correlates with CARDIOVASCULAR DISEASE (CVD) teritic form, which does not appear to improve such as HYPERTENSION (high BLOOD PRESSURE) and with corticosteroids. Lifestyle modifications such ATHEROSCLEROSIS. Other conditions associated with as SMOKING CESSATION improve circulation in gen- the nonarteritic form include DIABETES, HYPOTENSION eral with the presumption that such improvement (low blood pressure), and RHEUMATOID ARTHRITIS. also affects optic structures. ASPIRIN THERAPY, such Vision impairment due to ischemic optic neu- as prescribed as a prophylactic measure for HEART ropathy comes on suddenly. In a characteristic pat- ATTACK and stroke, may have a preventive effect tern, a person wakes up in the morning with with the arteritic form. It is especially important to noticeable loss of VISUAL ACUITY and VISUAL FIELD. manage underlying health conditions that affect This may continue for several days, improving as circulation, such as hypertension and diabetes. the day goes on, though in short order becomes When the ischemic optic neuropathy affects permanent. The diagnostic path begins with OPH- only one EYE, the person can make adaptations THALMOSCOPY and SLIT LAMP EXAMINATION to visualize and adjustments to accommodate the vision the optic disk (portion of the optic nerve that impairment that do not necessarily require sub- attaches to the RETINA), which appears pale and stantial changes in lifestyle. Most people can still swollen. Diagnosis of giant cell arteritis by temporal read, work, and perform other functions of daily ARTERY biopsy confirms the diagnosis of the arteritic living with visual acuity in only one eye. Ischemic form of ischemic optic neuropathy. Doctors arrive optic neuropathy that involves both eyes can sig- at the diagnosis of the nonarteritic form on the nificantly affect lifestyle. basis of symptoms and ruling out other causes. See also TOXIC OPTIC NEUROPATHY; VASCULITIS. K

keratitis INFLAMMATION of the CORNEA, usually the keratoconus A degenerative disorder in which result of an INFECTION. The cause of the infection is the CORNEA thins, allowing it to protrude from the more commonly viral, such as HERPES SIMPLEX or surface of the EYE in somewhat of a cone shape. HERPES ZOSTER, than bacterial. Symptoms of infec- Keratoconus affects both eyes though often pro- tious keratitis include gresses at different rates in each eye. Ophthalmol- ogists do not know what causes keratoconus, • redness and irritation of the EYE and conjunc- though it appears to run in families. Keratoconus tiva (inner eyelids) is painless though results in progressive VISION • discomfort or PAIN IMPAIRMENT, typically in the forms of MYOPIA (near- • excessive tearing sightedness) and ASTIGMATISM (distortions of vision resulting from the irregular surface of the cornea). • difficulty keeping the eye open As these REFRACTIVE ERRORS are the primary symp- • diminished VISUAL ACUITY (usually blurred vision) toms, the keratoconus may not become apparent • eye discharge or crusting until the coning becomes obvious. Treatment for mild to moderate keratoconus is Viral keratitis usually runs its course without rigid gas-permeable contact lenses, which correct complication, though occasionally a secondary the refractive errors of vision as well as help con- bacterial infection may develop. ANTIVIRAL MEDICA- tain the shape of the cornea. As the keratoconus TIONS sometimes shorten the course of chronic progresses, however, contact lenses become less herpes infections. Bacterial keratitis typically fol- effective, and the thinned cornea may not be able lows a CORNEAL INJURY, such as an abrasion or lac- to tolerate them. Keratoconus ultimately destroys eration, and requires treatment with ophthalmic the cornea and is a leading reason for CORNEAL ANTIBIOTIC MEDICATIONS. Chronic or recurrent ker- TRANSPLANTATION, which replaces the diseased atitis can cause permanent scarring of the cornea, cornea with a donor cornea. Corneal transplanta- resulting in diminished visual acuity such as ASTIG- tion successfully restores vision in about 90 per- MATISM. Extensive corneal damage may require cent of people who have keratoconus and CORNEAL TRANSPLANTATION. undergo the procedure. SUNBURN is the most common cause of noninfec- In 2004 the US Food and Drug Administration tious keratitis. Extended exposure to the sun, espe- (FDA) approved a new treatment for keratoconus, cially on or around water, exposes the surface of corneal inserts, which are tiny plastic rings the the eye to the same ultraviolet rays that cause sun- ophthalmologist implants along the edge of the burn of the SKIN. Ultraviolet burns to the cornea are cornea. The corneal inserts flatten the cornea, painful; treatment with ophthalmic CORTICOSTEROID reducing the coning. Corneal inserts come in dif- MEDICATIONS helps reduce the inflammation. ferent thicknesses to allow less or more flattening See also BACTERIA; CONJUNCTIVITIS; EPISCLERITIS; and are replaceable. IRITIS; SCLERITIS; SUN PROTECTION; UVEITIS; VIRUS. See also CORNEAL INJURY; CORRECTIVE LENSES.

99 L–M

lens The primary focusing structure of the EYE, tions, and may include TRAUMATIC BRAIN INJURY located in the center at the front of the eye. The (TBI), STROKE, and medication response such as lens is transparent, convex (rounded outward on with narcotic use, which causes the muscles to each side), round, and flexible. A thin membrane relax. Eye disorders often affect only one eye (uni- encloses the lens. Tiny muscles at the front edges lateral mydriasis), whereas systemic conditions of its sides, the ciliary muscles, contract to flatten typically affect both eyes (bilateral mydriasis). the lens and relax to thicken the lens. These PHOTOPHOBIA (sensitivity to bright light) often adjustments alter light refraction (the angle at accompanies mydriasis as the dilated pupil cannot which the lens bends lightwaves entering the eye) limit light from entering the eye. VISION IMPAIRMENT to accommodate near and distant vision. The most depends on the extend of the dilation; a fully common health conditions that affect the lens are dilated pupil prevents focus on near objects. PRESBYOPIA, in which the FLEXIBILITY of the lens The diagnostic path begins with a basic OPH- diminishes with aging, and CATARACT, in which THALMIC EXAMINATION including SLIT LAMP EXAMINA- protein deposits cloud the lens and obscure vision. TION and OPHTHALMOSCOPY, unless there is clear The lens is also vulnerable to accidental injury, evidence that the mydriasis results from systemic particularly from blunt force (such as a baseball) causes. TONOMETRY, which measures the pressure or puncture. within the eye (INTRAOCULAR PRESSURE), determines For further discussion of the lens within the whether glaucoma is present. Tears of the iris are context of ophthalmologic structure and function typically apparent when looking at the eye as they please see the overview section “The Eyes.” distort the iris (the colored portion of the eye). See also CATARACT EXTRACTION AND LENS REPLACE- Inflammation of the iris (IRITIS) often reddens the MENT; CORNEA; HYPEROPIA; MYOPIA; REFRACTIVE ERRORS; eye and is apparent with ophthalmoscopy. Further RETINA; VISION IMPAIRMENT. diagnostic measures turn to NEUROLOGIC EXAMINA- TION. Treatment targets the causative condition. mydriasis Excessive or persistent dilation of the See also EYE PAIN; NARCOTICS; TRAUMA TO THE EYE. pupil that is a symptom of ophthalmic or systemic conditions. The ophthalmologist may induce myopia A refractive error commonly called mydriasis, using topical atropine, to examine the nearsightedness, in which the EYE has difficulty inner EYE. Therapeutic mydriasis using atropine- focusing on distant objects. Myopia results when based ophthalmic drops is an alternate treatment the focal point of lightwaves entering the eye falls for AMBLYOPIA. Two eye conditions can cause short of the RETINA, causing the images the retina mydriasis: GLAUCOMA and damage to the iris. In the registers to be blurred. The refractive error occurs healthy eye the iris, a muscular membrane, con- because the distance from the front to the back of trols the opening of the pupil. INFLAMMATION of or the eye is longer than normal. Symptoms of tears in the iris affect its ability to function, which myopia include also can result in mydriasis. Other causes of mydriasis are systemic, involv- • squinting when looking at distant objects ing damage to NERVOUS SYSTEM structures and func- • straining to see when driving 100 myopia 101

• difficulty seeing the ball when playing baseball, alters the shape of the CORNEA, provides refractive tennis, and similar sports correction for mild to moderate myopia (–1 to –15 • frequent headaches at the end of the day diopters). In 2004 the US Food and Drug Adminis- tration (FDA) approved an implantable contact CORRECTIVE LENSES (eyeglasses or contact lenses) lens to improve severe myopia (–15 to –30 can compensate for myopia by altering the focal diopters). Severe myopia sometimes cannot be point of lightwaves so it falls directly on the retina. fully corrected, resulting in VISION IMPAIRMENT with They do so by refracting, or bending, the light- functional limitations or legal blindness. Myopia is waves inward. Eye professionals denote refractive the most common refractive error, affecting about corrections in units of measure called diopters. For 35 percent of adults. myopia, the expression of diopter is a negative See also ASTIGMATISM; HYPEROPIA; PRESBYOPIA; number. REFRACTIVE SURGERY, which permanently REFRACTIVE ERRORS. N

nearsightedness See MYOPIA. itself a condition. Nystagmus nearly always indi- cates VISION IMPAIRMENT; if congenital, the impair- night blindness Impaired dark adaptation result- ment may improve or completely resolve with ing from slowed photochemical reactions in the age. Vision impairment in adults depends on the rods, the specialized cells of the RETINA that per- underlying cause of the nystagmus. Temporary ceive contrast and detect visual images in low induced nystagmus, such as may occur with light. Night blindness becomes increasingly com- caloric testing (warm or cool water infused into mon after middle age. The person with night the auditory canal) to assess disorders of the blindness may be unable to see at all in dim light vestibular system, does not affect vision, although or may experience delayed adjustment when vestibular disorders can cause nystagmus. going from a lighted environment to a dim or dark environment. A diminished VISUAL FIELD with Causes of Causes of restricted peripheral vision also contributes to Congenital Nystagmus Acquired Nystagmus night blindness, as the outer edge of the retina ALBINISM (absence of retinal vestibular disorders where peripheral vision takes place contains pigmentation) brainstem or cerebellum mostly rods. congenital macular defects damage or tumor There are not many treatment options for night congenital CATARACT MULTIPLE SCLEROSIS blindness. Nutritional supplementation of vitamin absence of iris TRAUMATIC BRAIN INJURY(TBI) A and the antioxidants LUTEIN and ZEAXANTHIN, anomalies of the OPTIC NERVE TRAUMATIC BRAIN INJURY(TBI) which some studies show help maintain the chronic ALCOHOL abuse health of the eye and improve the functioning of the rods, seem to aid some people. Adequate light- The diagnostic path includes a comprehensive ing when reading and especially when watching OPHTHALMIC EXAMINATION and NEUROLOGIC EXAMINA- television or movies reduces the need for the TION. Treatment targets the underlying cause. eye to make accommodations for changing light. Some adults who have acquired nystagmus Increased lighting can compensate for dimin- receive relief from the muscle relaxant medication ished dark adaptation in static settings such as baclofen (Lioresal), which interrupts NERVE signals rooms and offices, though it is not possible to from the BRAIN to the muscles that control the make similar accommodations for functions such eyes. The long-term consequences for vision as driving. depend on the cause and duration of the nystag- See also AGING, EYE AND VISION CHANGES THAT mus. Occasionally nystagmus occurs as an unde- OCCUR WITH; ANTIOXIDANT; PRESBYOPIA; VISION HEALTH. sired SIDE EFFECT of antiseizure medications, and typically goes away with switching to another nystagmus Involuntary movements of the eyes, medication. usually rapid and repetitive. Nystagmus can be See also BENIGN PAROXYSMAL POSITIONAL VERTIGO congenital or acquired; in either circumstance it is (BPPV); DIPLOPIA; MUSCLE RELAXANT MEDICATIONS; PHO- a symptom of underlying disorders rather than TOPHOBIA; STRABISMUS.

102 O

ocular herpes simplex An INFECTION of the eyes ocular herpes zoster INFECTION of the eyes with with HERPES SIMPLEX VIRUS 1 (HSV-1), which causes the varicella zoster VIRUS, a member of the HERPES cold sores, or herpes simplex virus 2 (HSV-2), SIMPLEX family of viruses that causes CHICKENPOX which causes GENITAL HERPES. The virus spreads to and shingles. After the infectious stage of chicken- the eye to cause the initial infection via contami- pox subsides, the virus submerges itself in NERVE nation from contact with an existing herpes sore roots. It may reemerge years to decades later, elsewhere on the body. Ocular herpes simplex fea- erupting in a rash of painful blisters along a nerve tures similar eruptions of sores on the surface of tract that hosts the virus. Ocular herpes zoster the EYE and inside the eyelids. The sores are very occurs when an outbreak that affects the face, painful and can cause permanent scarring of the usually along the tract of the trigeminal nerve, CORNEA. spreads to the EYE. Usually the outbreak affects About half of people who have one outbreak of only the eye on the same side of the face as the ocular herpes simplex will experience a second; shingles eruption, though sometimes the shingles about 20 percent have persistently recurring infec- eruption affects both sides of the face. When this tions, ranking ocular herpes simplex as the leading is the case, ocular herpes zoster can affect both infectious cause of corneal destruction. A serious eyes as well. As in other locations, the shingles complication of ocular herpes simplex is stromal blisters in the eye cause intense PAIN. KERATITIS, in which the IMMUNE SYSTEM begins to The blisters and pain are characteristic of ocular attack the stromal cells that make up the cornea. herpes zoster, making it possible for the doctor to This leads to scarring deep within the cornea, make the diagnosis based on their presentation. resulting in distortions of vision and diminished Treatment typically includes ANTIVIRAL MEDICATIONS VISUAL ACUITY. (such as acyclovir), ophthalmic CORTICOSTEROID The sores of ocular herpes simplex are charac- MEDICATIONS to reduce INFLAMMATION, tricyclic ANTI- teristic of the infection. The antiviral medication DEPRESSANT MEDICATIONS to prevent postherpetic acyclovir may reduce the severity of outbreaks of NEURALGIA, and ANALGESIC MEDICATIONS to relieve the infection when taken at the first sign of symp- pain. Symptoms may take several weeks to several toms. Some studies show that taking acyclovir for months to resolve. Numerous complications are 12 months significantly reduces recurrent ocular possible that can have long-term consequences for herpes simplex. However, there is no cure for vision, including GLAUCOMA and CATARACT. Ocular herpes infection. Damage that occurs as a conse- herpes zoster very seldom recurs, though this is a quence of infection is permanent. Infection- risk for those who are immunocompromised such control methods, such as frequent HAND WASHING as with HIV/AIDS or receiving IMMUNOSUPPRESSIVE and keeping the fingers away from the eyes, can THERAPY such as following ORGAN TRANSPLANTATION. help prevent initial infection. See also BLISTER; CORNEAL TRANSPLANTATION. See also ANTIVIRAL MEDICATIONS; AUTOIMMUNE DIS- ORDERS; COLD SORE; CORNEAL INJURY; CORNEAL TRANS- ophthalmic examination The basic diagnostic PLANTATION. procedures an ophthalmologist uses to assess the

103 104 The Eyes health of the EYE and vision, and detect problems tomas (small blind spots in the field of vision), with the structures and functions of the eye. The which are both symptoms of glaucoma and RETINI- standard ophthalmic examination includes several TIS PIGMENTOSA. components. For certain parts of the examination the ophthalmologist may place drops in the eyes Slit Lamp Examination that anesthetize the eye and dilate the pupils, to The SLIT LAMP EXAMINATION, also called a biomicro- facilitate examining the structures of the back of scopic examination, uses light focused as an elon- the eye such as the RETINA and optic disk. Some gated slit in combination with magnification. Slit people experience mild stinging when the drops lamp examination allows the ophthalmologist to first enter the eye. There is otherwise no discom- closely examine the front structures of the eye fort with an ophthalmic examination. The com- including the sclera, CORNEA, iris, and LENS. It is a plete exam takes about 10 minutes. common procedure for diagnosing cataract. The ophthalmologist may also use FLUORESCEIN STAINING Physical Examination to check for CORNEAL INJURY such as ABRASIONS or The ophthalmologist begins with an examination lacerations. of the orbital tissues, outer eyelids, inner eyelids, and conjunctiva (membrane lining the inner eye- Ophthalmoscopy lids) of first one eye and then the other, checking The ophthalmoscope is a hand-held device that to see that the eyelids open and close properly and resembles a flashlight. It has narrowly focused looking for any growths or irritation. The ophthal- beam of light and a magnifying lens. The ophthal- mologist then checks the movement of the eyes, mologist uses it to examine the inner structures of typically by asking the person to follow the track the back of the eye known collectively as the fun- of an object such as a pen. Using a small light, the dus: the retina, optic disk, and macula. The oph- ophthalmologist checks the reaction of the pupils. thalmologist usually dilates the pupil for These procedures help the ophthalmologist to OPHTHALMOSCOPY. This test helps detect numerous assess the basic neurologic aspects of the eye’s problems of the eye including RETINAL DETACHMENT, functions. RETINOPATHY, OPTIC NERVE ATROPHY, and PAPILLITIS. Conditions such as glaucoma cause characteristic Visual Acuity and Visual Field changes to the fundus. The familiar SNELLEN CHART test for VISUAL ACUITY features lines of letters in differing sizes and order Tonometry of presentation. Covering first one eye and then The tonometer is a device that measures INTRAOCU- the other, the person reads the line with the LAR PRESSURE (the pressure within the eye). The smallest letters that appear clear. The ophthalmol- most simple variation involves measuring the ogist records the result as a ratio that represents force it takes for a puff of air to indent the cornea, actual visual acuity compared to a standard of a noncontact test. For more accurate results the 20/20, with a score of 20/20 being what the nor- ophthalmologist numbs the eye with anesthetic mal eye sees at a distance of 20 feet. Diminished drops and touches a TONOMETRY probe against the visual acuity may result from REFRACTIVE ERRORS surface of the eye to measure the pressure. such as MYOPIA (nearsightedness) or HYPEROPIA (far- Tonometry is a basic screening test for glaucoma, sightedness), or signal conditions of the eye such for which increased intraocular pressure is a key as CATARACT or GLAUCOMA. symptom. The ophthalmologist tests for basic VISUAL FIELD See also AMSLER GRID; REFRACTION TEST; SCOTOMA; by having the person focus on an object in the dis- VISION HEALTH. tance and signal when he or she can see an object (such as a pen the ophthalmologist holds) that ophthalmoscopy Examination of the EYE using moves into the field of normal vision. This test an ophthalmoscope, a hand-held, lighted magnify- assesses peripheral vision and helps detect sco- ing lens. The ophthalmoscope projects a narrowly optic nerve atrophy 105 focused beam of light that illuminates the struc- CONDITIONS THAT CAN AFFECT THE OPTIC NERVE tures of the eye. Ophthalmoscopy is the essential aging GLAUCOMA introductory examination of the eye and can ISCHEMIC OPTIC NEUROPATHY TOXIC OPTIC NEUROPATHY determine what, if any, further diagnostic proce- PAPILLEDEMA PAPILLITIS dures are necessary. Ophthalmoscopy allows the RETINAL DETACHMENT RETINITIS PIGMENTOSA doctor to examine the inner surfaces of the eye- RETROBULBAR OPTIC NEURITIS RETINOPATHY lids, general surface of the eye (sclera and CORNEA), pupil response, and iris. It also allows the For further discussion of the optic nerve within doctor to visualize the inner structures at the back the context of ophthalmologic structure and func- of the eye, notably the RETINA , optic disk, and tion please see the overview section “The Eyes.” macula. See also AGING, VISION AND EYE CHANGES THAT See also OPHTHALMIC EXAMINATION; OTOSCOPY; SLIT OCCUR WITH; CRANIAL NERVES; ENUCLEATION; OPHTHAL- LAMP EXAMINATION; TONOMETRY. MOSCOPY. optical coherence tomography (OCT) An imag- ing procedure that noninvasively and painlessly optic nerve atrophy Death of NERVE cells within permits the ophthalmologist to visualize the layers the OPTIC NERVE, affecting the optic nerve’s ability to convey nerve signals from the EYE to the BRAIN. of the RETINA. OCT can provide a “virtual biopsy” Optic nerve atrophy can be partial or complete; of retinal tissue, helping diagnose or monitor AGE- when complete there is total loss of vision. Condi- RELATED MACULAR DEGENERATION (ARMD), macular tions of the eye or systemic neurologic disorders holes, retinal tears, and OPTIC NERVE inflammation can cause optic nerve atrophy. Symptoms include or damage such as can result from GLAUCOMA. The diminished VISUAL ACUITY VISUAL FIELD ophthalmologist can perform OCT in the office; no and . preparation or recovery is necessary. CAUSES OF OPTIC NERVE ATROPHY See also ELECTRORETINOGRAPHY. Eye Conditions Neurologic or optic nerve The second cranial NERVE, which Systemic Conditions conveys nerve impulses from the EYE to the BRAIN. congenital OPTIC NERVE HYPOPLASIA MULTIPLE SCLEROSIS There are two optic nerves, one from each eye. ISCHEMIC OPTIC NEUROPATHY TRAUMATIC BRAIN INJURY (TBI) The fibers that become the optic nerve originate in congenital CATARACT STROKE the occipital lobes of the cerebrum, in an area RETINITIS PIGMENTOSA methanol poisoning called the visual cortex. Each extends along struc- GLAUCOMA untreated SYPHILIS tures called the optic tracts that pass through the temporal lobes and the center of the brain, con- The diagnostic path begins with OPHTHAL- verging in the optic chiasm. At this point the optic MOSCOPY, which allows the ophthalmologist to see tracts cross, such that the one originating in the the visual changes in the optic disk (end point of left visual cortex goes to the right eye and the one the optic nerve where it joins the RETINA) that originating in the right visual cortex goes to the denote its atrophy. Further assessment to deter- left eye. Each optic nerve enters the back of the mine the cause may include diagnostic imaging eye, terminating in the RETINA. procedures such as COMPUTED TOMOGRAPHY (CT) The ophthalmologist can see through the oph- SCAN or MAGNETIC RESONANCE IMAGING (MRI) and a thalmoscope the end of the optic nerve, called the comprehensive NEUROLOGIC EXAMINATION. Treat- optic disk. It appears as a pale circle, about the size ment targets the underlying cause, though it can- of a pencil eraser, against the dark background of not recover vision already lost. Treatment that can the retina. The retina’s network of nerves extends halt the causative condition can prevent further from the optic nerve, gathering nerve impulses loss of vision, though when the cause is a degen- from the rods, cones, and other nerve cells in the erative disorder such as MULTIPLE SCLEROSIS vision retina. loss is likely to continue. 106 The Eyes

People who smoke cigarettes or consume high Orbital cellulitis requires emergency quantities of ALCOHOL, particularly in combination, medical attention. Delayed treatment have a higher risk for developing idiopathic optic can result in permanent vision loss. nerve atrophy (in which the cause remains unde- termined. NUTRITIONAL SUPPLEMENTS containing vita- min A and the antioxidants LUTEIN and ZEAXANTHIN The most common causes are infections that may improve visual acuity. affect the eyelids such as HORDEOLUM and BLEPHARI- See also OPTIC NERVE HYPOPLASIA; RETROBULBAR TIS, DACRYOCYSTITIS (infected tear duct), and infec- OPTIC NEURITIS; TOXIC OPTIC NEUROPATHY. tions of adjacent structures such as SINUSITIS (sinus infection), PHARYNGITIS (throat infection), tooth optic nerve hypoplasia A congenital condition ABSCESS, and occasionally OTITIS media (middle ear in which the OPTIC NERVE fails to develop com- infection). Insect bites that become infected also pletely in the unborn child. Optic NERVE hypoplasia can cause orbital cellulitis. Orbital cellulitis may is the third leading cause of congenital vision loss affect one eye or both eyes, depending on the in the United States. The defect is random and underlying cause. The eyelids typically swell may affect one EYE or, more commonly, both eyes. closed and may appear bruised, with considerable Children who have optic nerve hypoplasia may PAIN as well as inability to see. Often there is a have barely noticeable to complete VISION IMPAIR- moderate FEVER (above 102ºF) and EXOPHTHALMOS MENT depending on the extent to which the optic (bulging of the eye). nerve develops. Diminished peripheral vision and The diagnostic path includes assessment of depth perception are common. Typically the pedi- VISUAL ACUITY and VISUAL FIELD, to the extent possi- atrician detects an abnormality of the optic nerve ble, as well as COMPUTED TOMOGRAPHY (CT) SCAN or shortly after birth, though mild optic nerve MAGNETIC RESONANCE IMAGING (MRI) to visualize the hypoplasia may escape notice until the child extent of the infection and determine its site of begins having vision difficulties. Optic nerve origin. Treatment is immediate intravenous ANTIBI- hypoplasia does not progress, so VISUAL ACUITY typi- OTIC MEDICATIONS with hospitalization until fever cally remains stable. CORRECTIVE LENSES may and swelling subside. Prompt and appropriate accommodate for vision impairments. Other treat- treatment improves the likelihood for full recov- ment focuses on teaching the child adaptive meth- ery and restored vision. Complications can include ods. There are no known preventive measures. increased INTRAOCULAR PRESSURE, which is damag- See also AMBLYOPIA; OPTIC NERVE ATROPHY. ing to the RETINA and OPTIC NERVE. Because the optic NERVE presents a direct channel to the BRAIN, optic neuritis See PAPILLITIS. INFECTION also may spread to cause MENINGITIS or orbital cellulitis INFLAMMATION and swelling of the ENCEPHALITIS. tissues surrounding the EYE, including the eyelids. See also CONJUNCTIVITIS; TRAUMA TO THE EYE. P papilledema Swelling of the optic disk, the point from, and may be an early diagnostic indicator of, at which the OPTIC NERVE enters the RETINA, that systemic inflammatory conditions such as MULTIPLE results from increased pressure within the skull. SCLEROSIS and temporal arteritis. The inflammation Papilledema typically signals serious neurologic also may follow viral or bacterial INFECTION such as damage such as STROKE or TRAUMATIC BRAIN INJURY SINUSITIS, especially in children, and occurs rarely (TBI) that causes bleeding (HEMORRHAGE), brain as a complication following stings from wasps and tumor, extreme HYPERTENSION, or inflammatory bees. Papillitis often affects only one EYE though INFECTION such as ENCEPHALITIS and MENINGITIS. can involve both eyes. Within hours of its onset Though papilledema is not a disorder of the EYE, the inflammation can cause complete loss of untreated it will result in complete loss of vision vision in the affected eye. Rapid treatment to because the swelling interrupts the flow of blood reduce the inflammation, or to treat the underly- to the optic NERVE. ing condition causing the inflammation, can sal- Doctors check for any signs of papilledema dur- vage vision. However, loss of vision is often the ing a routine OPHTHALMIC EXAMINATION, as often reason people seek medical attention, by which papilledema is an early sign of a neurologic prob- time there may already be permanent damage to lem. The need for intervention to relieve the the optic disk. Occasionally the inflammation intracranial pressure is urgent, not only to pre- develops over the course of several weeks, pro- serve vision but also often as a lifesaving measure. ducing progressive loss of vision as well as loss of The nature of the intervention depends on the color perception. underlying cause. Extremely elevated blood pres- See also BACTERIA; PAPILLEDEMA; RETROBULBAR sure points to hypertension as the cause; other OPTIC NEURITIS; TOXIC OPTIC NEUROPATHY; VIRUS. causes require NEUROLOGIC EXAMINATION for further evaluation and diagnosis. With prompt treatment photophobia Heightened sensitivity to bright to reduce the intracranial pressure, papilledema light, usually the result of INFLAMMATION or irrita- typically resolves in about six to eight weeks and tion to structures of the EYE or with MYDRIASIS vision, if affected, returns to its previous level. (extended dilation of the pupil). Photophobia Swelling around the optic disk may occur for causes discomfort in the eye ranging from a burn- various reasons that are not the result of increased ing sensation to outright PAIN. Often there is exces- intracranial pressure. These are usually ophthal- sive tearing and the eye becomes reddened in mologic in nature, such as GLAUCOMA and ISCHEMIC response to the irritation. In severe photophobia it OPTIC NEUROPATHY. The conditions threaten vision, may be impossible to keep the eye open. Photo- but they are not life-threatening. phobia is common in the HEALING period following See also OPTIC NERVE ATROPHY; RETROBULBAR OPTIC CATARACT EXTRACTION AND LENS REPLACEMENT and NEURITIS; TOXIC OPTIC NEUROPATHY. CORNEAL TRANSPLANTATION. Photophobia may be a symptom of numerous conditions affecting the papillitis INFLAMMATION of the optic disk, the por- eye, including tion of the OPTIC NERVE that enters the RETINA (also called the “blind spot”). Papillitis typically results • CORNEAL INJURY, such as ABRASIONS and burns 107 108 The Eyes

• INFECTION, such as BLEPHARITIS, CONJUNCTIVITIS, IRI- The risks and potential complications of PTK TIS, HORDEOLUM, KERATITIS, UVEITIS include • CHALAZION • INFECTION • ENTROPION • worsened visual acuity • Dirty contact lenses or contact lenses worn too long • RECURRENCE of the original problem

Photophobia that occurs with FEVER Most people experience improved visual acuity may indicate MENINGITIS and requires or relief from corneal PAIN following PTK. emergency medical attention. See also CORNEAL TRANSPLANTATION; SURGERY BENE- FIT AND RISK ASSESSMENT. The diagnostic path typically includes SLIT LAMP EXAMINATION with FLUORESCEIN STAINING to deter- pinguecula A thickened area of the conjunctival mine whether there is corneal injury and OPHTHAL- tissue on the EYE, usually forming on the inner MOSCOPY to evaluate the structures of the inner (NOSE) side of the eye. A pinguecula may be clear, eye. These examinations often require anesthetiz- yellow, or gray in color, and develops slowly. It ing drops in the eye to numb the discomfort the presents no threat to vision or the eye, and is lighted instruments cause. Treatment targets the more common in people over age 50. Many peo- underlying cause, which, when resolved, gener- ple do not notice that they have pingueculae or ally ends the photophobia. ANTIBIOTIC MEDICATIONS, consider them normal features of their eyes, usually ophthalmic solutions or ointment placed though some people experience irritation and a in the affected eye, are necessary to treat bacterial sensation of grittiness in the affected eye. People infections. Wearing sunglasses to restrict the who spend a lot of time in the sun or have other amount of light that can enter the eye helps long-term ultraviolet light exposure are more reduce the sensitivity response. Some people are likely to develop a pinguecula. Ophthalmologists naturally photophobic without underlying eye recommend wearing sunglasses or protective eye- conditions and should wear sunglasses for wear that filters ultraviolet light. There is no rea- improved comfort in bright-light settings. son to treat a pinguecula unless it puts pressure on See also BACTERIA; TRAUMA TO THE EYE. the CORNEA or otherwise interferes with vision. See also CONJUNCTIVITIS; PTERYGIUM; SCLERITIS. phototherapeutic keratectomy (PTK) Treatment with an excimer (cool) laser to smooth irregulari- presbyopia A progressive change in the eyes ties and dissipate cloudiness in the CORNEA. PTK is that occurs with aging, in which it becomes an AMBULATORY SURGERY procedure, with local anes- increasingly difficult to focus on near objects. thetic to numb the surface of the EYE and a mild Presbyopia occurs because the LENS loses sedative for comfort. The procedure takes 20 to 45 FLEXIBILITY, limiting its ability to adjust between minutes, depending on the extent of corneal near and far focus. The lens becomes unable to sculpting needed. The ophthalmologist may pre- contract to thicken in the center as near focus scribe ophthalmic ANTIBIOTIC MEDICATIONS and anti- requires, resulting in the inability to see objects inflammatory medications after the procedure. that are close, such as when reading. Most people Changes in VISUAL ACUITY are generally complete in begin to notice presbyopia when they reach their one to two months. mid-40s in age. People who have MYOPIA (near- sightedness) may also find that their distant vision CONDITIONS PTK CAN TREAT improves as presbyopia advances. The EYE changes ASTIGMATISM corneal clouding responsible for presbyopia reach their end point corneal degeneration corneal dystrophy by about the mid-50s, after which the stiffening of corneal scarring recurrent corneal erosion the lens stabilizes. Eyeglasses, contact lenses, and recurrent KERATITIS REFRACTIVE ERRORS surgery offer options for correcting presbyopia. prosthetic eye 109

Eyeglasses overnight hospital stay. In conductive kerato- The conventional treatment for presbyopia is read- plasty, the ophthalmologist uses radiofrequency ing glasses, which are magnifying lenses that energy applied in a concentric pattern around the enlarge near objects to allow the eyes to focus on base of the CORNEA to shrink corneal collagen. This them. Many retail and optical stores sell standard constricts the cornea’s base, causing the center of reading glasses that come in common magnifica- the cornea to thicken and rise, which improves tions typically ranging from +1.00 to +3.00 in gra- close focus. It may take several weeks to experi- dations of 0.25 power. This is often the least ence the full effect. In LASIK, the ophthalmologist expensive and most convenient option. An optom- uses an excimer laser to reshape the cornea. There etrist also can prescribe custom-strength lenses. is little recovery time with LASIK, and effects are People whose eyes otherwise do not require apparent almost immediately. refractive correction wear reading glasses as Each surgical method establishes a permanent needed for close vision. People who have other degree of monovision. Depending on the age of REFRACTIVE ERRORS, such as myopia or ASTIGMATISM, the person and the anticipated progression of the and wear eyeglasses require bifocal or trifocal COR- presbyopia, the ophthalmologist may leave a mar- RECTIVE LENSES that provide multiple levels of cor- gin of correction to allow for future changes. rection to accommodate both the refractive Many ophthalmologists recommend a trial of correction and the magnification for close vision. monovision with contact lenses before surgery to Eyeglass lenses may be progressive, in which there determine whether the approach produces accept- are no discernible lines on the lens to mark the able results. The risks of surgical correction for transition from one level to another. People who presbyopia include INFECTION, vision that still wear contact lenses to correct refractive errors requires corrective lenses even after surgery, and, often choose to wear reading glasses as needed rarely, worsened vision. Some people may have with the contacts for close vision, or may choose other eye conditions, vision problems, or general to switch to eyeglasses. health conditions that exclude them from surgery as an option to correct presbyopia. Contact Lenses See also HYPEROPIA; REFRACTIVE SURGERY; SURGERY Contact lenses may also have multiple levels of BENEFIT AND RISK ASSESSMENT. refractive correction (multifocal contact lenses). Another approach using contact lenses is monovi- prosthetic eye A cosmetic replacement, also sion, in which one eye, typically the dominant called an ocular prosthesis or artificial EYE, for a eye, wears a lens that fully corrects for refractive surgically removed (enucleated) eye. A specialist error and the other eye wears a lens that under- called an ocularist designs the prosthetic eye to be corrects. The BRAIN learns to distinguish which eye as close a match in appearance as possible for the to use for close and for distant focusing, automati- remaining natural eye. cally shifting as necessary. It may take a week or The most common type of prosthetic eye two for the brain to make the adjustment and for attaches to a spherical implant the same size and monovision to feel comfortable. However, some shape of the eye that the surgeon places in the people do not adjust to monovision at all. Mono- orbit (eye socket) after removing the eye. As the vision results in some loss of depth perception, HEALING process takes place, other tissues and which some people find barely noticeable and blood vessels grow into and around the implant, other people find intolerable. anchoring it firmly within the orbit. Once healing is complete, the surgeon drills into the front of the Surgery implant to attach a small post. The post then holds In the United States, the two most commonly the prosthetic eye, a “facing” that fits over the used surgical methods to correct presbyopia are front of the implant. The muscles of the orbit conductive keratoplasty and LASIK (an acronym move the implant in coordination with the move- for laser-assisted in situ keratomileusis), both done ments of the healthy eye, providing a natural as ambulatory procedures that require no appearance to the prosthetic eye. 110 The Eyes

Another type of ocular prosthesis is a scleral CORNEA, applying pressure or growing into the shell, which covers a dysfunctional and disfigured corneal region. When this occurs, surgery to eye that remains in place. The scleral shell is remove the pterygium is necessary to preserve somewhat like an oversize contact lens, fitted to vision. Pterygia tend to recur following surgery, rest on the eye as does a contact lens. The ocular- though it may take a number of years to reach a ist designs the front of the shell to match the size that interferes with vision. appearance of the other eye. Because the scleral See also CONJUNCTIVITIS; PINGUECULA; SCLERITIS. shell rests on the surface of the eye, it moves in synchronization with the other eye for a natural ptosis Drooping of the upper eyelid. Ptosis often appearance. is a consequence of MUSCLE weakness or neuro- Over time the orbital structures change and the logic damage, and is sometimes a symptom of a materials of the prosthetic eye experience some neurologic condition such as MYASTHENIA GRAVIS or natural deterioration. Most people need to replace MUSCULAR DYSTROPHY. Ptosis may be congenital the prosthetic eye every two years, though the (present at birth), the result of underdevelopment implant is permanent. Children may need more or absence of the levator muscle that raises the frequent replacements to keep pace with their eyelid. Ptosis also may develop with advanced age, growth. The prosthesis requires regular care and reflecting weakening of the muscles that control cleaning. the eyelid. See also ENUCLEATION. When the drooping obscures vision, surgery to raise the eyelid is necessary to prevent AMBLYOPIA. pterygium A growth arising from the conjuncti- Surgery may result in a slight asymmetry in the val tissue around the perimeter of the EYE, usually movements of the upper eyelids, particularly in on the side near the NOSE. A pterygium character- congenital ptosis, when the levator muscle is miss- istically grows in a triangular shape, and has its ing and the surgeon must configure eyelid move- own BLOOD supply to support its growth. Growth ment to make use of other muscles. Generally no generally is slow. Often a pterygium remains treatment is necessary when the ptosis does not innocuous, though some people experience irrita- interfere with vision, except as desired for cos- tion and a sensation of grittiness in the affected metic purposes. eye. Occasionally the growth encroaches on the See also BLEPHARITIS; BLEPHAROPLASTY; ECTROPION. R

refraction test A diagnostic procedure to meas- refractive surgery Operations to correct REFRAC- ure REFRACTIVE ERRORS of the EYE, such as MYOPIA, TIVE ERRORS of vision such as MYOPIA (nearsighted- HYPEROPIA, and ASTIGMATISM. An optometrist or ness), HYPEROPIA (farsightedness), and ASTIGMATISM ophthalmologist conducts the test using a device (irregularity of the CORNEA). Refractive surgery called a refractor. The refractor fits against the face became an option for permanent refractive correc- somewhat like a flattened pair of binoculars, with tion in the United States in the 1980s, following a chin rest and forehead pad to support the head its introduction and rapid growth in popularity in in proper position. After covering one eye, the eye Europe. Now, about 1.5 million Americans professional applies combinations of lenses to the undergo refractive surgery operations each year. eye piece. The person looks through the eye piece and lens at a rendition of the SNELLEN CHART. The Surgical Procedure eye professional examines first one eye with the There are numerous refractive surgery techniques other eye covered, switches eyes, and finally in use today. They fall into the general categories examines both eyes together to confirm the of those that use lasers, those that use microker- appropriate refractive correction. atomes (specialized blades), and those that use See also CORRECTIVE LENSES; OPHTHALMIC EXAMINA- implants to alter the eye’s natural structure. There TION. are five commonly performed refractive correction operations: refractive errors Vision disorders in which a defect of the EYE does not allow proper refraction • LASIK (laser-assisted in situ keratomileusis) has of light. When the eye is longer than normal from become the standard procedure for most refrac- front to rear, the lightwaves entering the eye focus tive corrections. The EYE surgeon makes a small short of the RETINA, resulting in MYOPIA (nearsight- flap to expose the inner portion of the cornea, edness). When the eye is shorter, the lightwaves uses an excimer (cool) laser to remove micro- that enter the eye focus behind the retina, result- scopically thin layers of corneal tissue, and ing in HYPEROPIA (farsightedness). An irregular sur- replaces the corneal flap. Because the surface of face or shape to the cornea may produce the cornea, which contains NERVE endings, distortions of refraction, resulting in ASTIGMATISM. remains intact, there is almost no postoperative The optometrist or ophthalmologist measures discomfort and results are immediately appar- refractive errors using a refraction test. Treatment ent. LASIK is most effective for hyperopia, is CORRECTIVE LENSES (eyeglasses or contact lenses) astigmatism, and moderate myopia. or REFRACTIVE SURGERY. Refractive errors may • Photorefractive keratectomy (PRK) was the change frequently during childhood, though usu- original refractive LASER SURGERY. The eye sur- ally stabilize by early adulthood. Severe refractive geon uses an excimer laser to reshape the sur- errors may be uncorrectable, notably myopia, face of the cornea. Results are not apparent resulting in functional or legal blindness. until the cornea heals, which takes several See also PRESBYOPIA; VISION IMPAIRMENT. weeks. There is some discomfort during the

111 112 The Eyes

HEALING phase. PRK is particularly effective for follow-up procedures intended to detect operative people who have large pupils or thin corneas, complications before they cause eye problems; it is because it does not create a corneal flap, which important to maintain the recommended follow- reduces the likelihood of postoperative glare up procedures. Other common complications and halos at night. include dry eyes and seeing halos around lights at • Automated lamellar keratoplasty (ALK) is simi- night. Procedures involving lens replacement lar in concept to LASIK, though the surgeon carry the additional risks of excessive bleeding and uses a microkeratome, a specialized surgical RETINAL DETACHMENT, which can compromise vision. blade. The eye surgeon makes a flap in the Complications particular to LASIK include irregu- cornea and removes minute segments of larity in the corneal surface after the corneal flap corneal tissue, then replaces the flap. As with heals and overgrowth of corneal tissue that LASIK, there is little discomfort during healing requires subsequent surgery to remove. and results are apparent immediately. ALK is Occasionally the outcome is not as desired or particularly successful for severe myopia. expected, perhaps as a consequence of complica- tions during the operation or during the healing •LENS replacement uses techniques perfected process. It is important for the eye surgeon to through 60 years of CATARACT EXTRACTION AND appropriately match the person with the proce- LENS REPLACEMENT surgery. The eye surgeon dure, which takes into consideration the nature removes the natural lens and replaces it with and severity of the refractive error, the person’s one curved to accommodate for severe hyper- age and general health status, and the person’s opia or myopia. Multifocal lens implants allow expectations. Despite the precision of computer- the eye to adjust between close and distant guided procedures, there remains an element of vision. unpredictability that influences outcome. Some • Phakic intraocular contact lens implantation people may find their vision undercorrected and places a permanent contact lens in front of or others overcorrected as a consequence of individ- behind the natural lens to supplement its focus- ual variation in eye structure, refractive error, and ing ability. This approach preserves the focusing healing process. ability of the natural lens. Though the changes of refractive surgery are permanent, the effects on vision are not. Everyone The eye surgeon may choose other methods, eventually acquires PRESBYOPIA, a decrease in the depending on an individual’s refractive situation, ability to focus on near objects that is a function of age, and general health status. Not everyone with change that occurs with aging. People who have refractive errors is a good candidate for refractive had refractive surgery to correct astigmatism, surgery. It is important to consult with a qualified hyperopia, or myopia will still need corrective and experienced eye surgeon and to understand measures for close vision as presbyopia develops. the potential risks and benefits of the different Nonsurgical solutions for presbyopia include con- operations. Refractive surgery permanently alters tact lenses or reading glasses. Surgical solutions for the eye’s structure, although subsequent opera- presbyopia currently employ an approach called tions can often refine the effects when they are monovision, in which the eye surgeon undercor- not as expected. Severe refractive errors may rects the vision in one eye for near focus. The require multiple procedures. refractive correction for the other eye is full, allowing for distant focus. The BRAIN does the Risks and Complications work of switching between the eyes according to As with any surgery, a potential complication of the vision needs. refractive surgery is postoperative INFECTION that can range from mild discomfort to significant Outlook and Lifestyle Modifications damage to the eye with resulting VISION Refractive surgery dramatically improves visual IMPAIRMENT. Prompt treatment prevents further acuity for nearly everyone who has a successful complications. Most eye surgeons have stringent surgical experience—that is, was properly retinal detachment 113 matched to the correct procedure, had the opera- fills the inner eye and holds pressure against the tion performed by a competent and experienced retina, keeping it smoothly and tightly adhered to eye surgeon, and had an uncomplicated course of the choroid. recovery. Some people are able to completely The ophthalmologist can examine the surface of eliminate the need for corrective lenses. Many the retina using OPHTHALMOSCOPY. Under illumina- people do still require corrective lenses, though at tion the retina appears reddish orange. The optic much improved refractive correction and perhaps nerve disk appears as a pale, pinkish circle. The only for specific applications such as near or macula, of similar size, appears as a darker and less midrange vision. distinct circular area with a depression, the fovea, Doctors do not know what, if any, long-term in its center. consequences may result from refractive surgery, as most of the laser techniques predominantly in CONDITIONS THAT CAN AFFECT THE RETINA use today have been available only since the AGE-RELATED MACULAR COLOR DEFICIENCY 1990s. Routine eye care and ophthalmic examina- DEGENERATION (ARMD) COLOR DEFICIENCY tions are especially important for people who have NIGHT BLINDNESS RETINAL DETACHMENT had surgery on their eyes, to detect complications RETINITIS PIGMENTOSA RETINOBLASTOMA from the surgery as well as eye conditions such as RETINOPATHY traumatic injury GLAUCOMA, AGE-RELATED MACULAR DEGENERATION (ARMD), and CATARACT. For further discussion of the retina within the See also AMBULATORY SURGERY; CORNEAL TRANS- context of eye structure and function please see PLANTATION; OPERATION; PHOTOTHERAPEUTIC KERATEC- the overview section “The Eyes.” TOMY (PTK); SURGERY BENEFIT AND RISK ASSESSMENT. See also ELECTRORETINOGRAPHY; FLASHES; LENS; VISION IMPAIRMENT; VITREOUS DETACHMENT. retina The innermost layer of the EYE. The retina receives light images and converts them to NERVE retinal detachment A separation of the RETINA impulses the OPTIC NERVE conveys to the BRAIN. The from the choroid, the layer of the EYE’s structure retina is two tissue-thin layers that together are that nourishes and attaches the retina. Retinal 1 less than ⁄2 millimeter in thickness. The outer pig- detachment may occur as a result of TRAUMA TO THE ment layer provides a completely light-absorbing, EYE, AGE-RELATED MACULAR DEGENERATION (ARMD), nonreflective lining. The inner sensory layer con- VITREOUS DETACHMENT, RETINOPATHY of DIABETES, or tains the photoreceptors (rods and cones) respon- surgery on the eye. Retinal detachment may also sible for vision. Rods detect only shades of gray occur spontaneously, a circumstance more com- though can register images of very low intensity. mon in people with moderate to severe MYOPIA Cones detect color and detail. (nearsightedness). Laid out flat, like a disk, the retina measures just under 2 inches in diameter. The primary work Prompt treatment to reattach the of vision takes place in an area about the size of a retina is necessary to save vision. postage stamp called the macula. Most of the retina’s 120 million rods and 6 million cones Symptoms and Diagnostic Path reside in the macula. A section of the central Retinal detachment does not cause PAIN or discom- retina no larger than a pencil eraser, the macula, fort. Detachment may be gradual, in which case contains almost no rods and an abundance of symptoms are progressive, or sudden, in which cones and handles detail vision. A pencil-point case loss of vision may be the only symptom. depression within the macula, the fovea, has the Symptoms of retinal detachment include highest concentration of cones. The optic nerve enters the retina somewhat to • seeing flashing lights or multiple FLOATERS the NOSE-side at the back of the eye, along with • the perception of a curtain or shadow dropping the ARTERY and VEIN that manage the retina’s BLOOD across the VISUAL FIELD, often from top to bot- supply. Vitreous humor, a gelatinous substance, tom though sometimes from the side 114 The Eyes

• blurred vision the ages of 10 and 30, with complete loss of vision • loss of VISUAL ACUITY by around age 40. When viewed through the ophthalmoscope, OPHTHALMOSCOPY to examine the interior of the the areas of degeneration appear darker than the eye provides the diagnosis. surrounding areas of retina. The diagnostic path may also include a DARK ADAPTATION TEST and ELEC- Treatment Options and Outlook TRORETINOGRAPHY. There is no known treatment for Most often, the preferred treatment for reattach- retinitis pigmentosa. Several INHERITANCE PATTERNS ing the retina is surgery. The surgeon may use are responsible for retinitis pigmentosa; doctors laser, photocoagulation (heat), or cryotherapy recommend GENETIC TESTING and GENETIC COUNSELING (freezing) techniques. Other approaches include for family members when there is a diagnosis of injecting sterile silicone oil into the inner eye or this condition. Retinitis pigmentosa also may injecting a sterile gas bubble (pneumotherapy) accompany a number of other hereditary syn- into the vitreous humor to hold the retina in place dromes. with pressure. A rapidly reattached retina often See also COLOR DEFICIENCY; NIGHT BLINDNESS; OPH- fully recovers without measurable loss of vision. THALMOSCOPY; RETINOPATHY; VISION IMPAIRMENT. Delay in reattaching the retina, or when the retina suddenly and completely detaches, often results in retinoblastoma A cancerous tumor of the RETINA less successful vision preservation. An untreated that most often occurs in children. Most retinal detachment results in permanent, complete retinoblastomas are hereditary and develop in loss of vision in the eye. early childhood, usually by age four. Some retinoblastomas are the result of new germline Risk Factors and Preventive Measures mutations though are not hereditary. About 70 People who have moderate to severe myopia percent of retinoblastomas involve only one EYE. (greater than – 8 diopters) are at increased risk for Treatment in such cases is surgery to remove the retinal detachment because of the eye’s shortened EYE (ENUCLEATION), with placement of a PROSTHETIC length. Retinal detachment is also a complication EYE for cosmetic reasons. When retinoblastoma is of LASIK surgery, CATARACT EXTRACTION AND LENS bilateral (involves both eyes), treatment attempts REPLACEMENT surgery, and serious inflammatory to save vision while eradicating the CANCER. Treat- conditions of the eye such as SCLERITIS. Retinopa- ment for bilateral retinoblastoma may include thy, in which extra blood vessels grow into the enucleation of one eye and cryotherapy or photo- retina, also increases the risk for retinal detach- coagulation to reduce as much as possible the ment. Protective eyewear to reduce the risk of tumor in the other eye, with follow-up trauma to the eye can prevent trauma-related reti- CHEMOTHERAPY or RADIATION THERAPY. Treatment is nal detachment. In other circumstances, early successful in about 90 percent of children when detection and reattachment are the most effective doctors detect the tumor before it metastasized measures to preserve vision. beyond the eye. However, about 70 percent will See also LASER SURGERY; OPERATION; REFRACTIVE experience second retinoblastomas by adulthood. SURGERY; SURGERY BENEFIT AND RISK ASSESSMENT. See also ADULT SURVIVORS OF CHILDHOOD CANCER; CANCER TREATMENT OPTIONS AND DECISIONS; GENE TEST- retinitis pigmentosa The collective term for a ING; GENETIC COUNSELING. group of hereditary disorders that result in pro- gressive loss of vision. Retinitis pigmentosa gener- retinopathy A dysfunction of the RETINA in ally begins with diminished night vision, as the which new BLOOD vessels grow across the retina’s degeneration affects primarily the rods (photore- surface. This growth causes the death of photore- ceptors responsible for vision in dim light and for ceptors, the specialized cells (rods and cones) in peripheral vision). Eventually the condition pro- the retina that receive lightwaves and convert gresses to rods, and then cones, throughout the them to NERVE impulses for transmission to the RETINA. In most people symptoms begin between BRAIN. The blood vessels are also delicate and retrobulbar optic neuritis 115 prone to bleeding, which further damages the sur- • FLASHES and FLOATERS face of the retina. The most common forms of • sudden loss of vision retinopathy are the following: OPHTHALMOSCOPY typically reveals discolored • Retinopathy of DIABETES results from chronically areas of the retina that indicate diminished blood elevated blood GLUCOSE levels. Retinopathy of supply (pale) or bleeding (dark). The ophthalmol- diabetes takes one of two forms: proliferative, ogist may also be able to see frank bleeding or in which the new blood vessels that grow irregularities in the surface of the retina that indi- across the retina are unstable and bleed, or cate accumulated fluid. When the cause of the nonproliferative, in which existing blood ves- retinopathy is hypertension, there may also be sels deteriorate and form aneurysms that rup- PAPILLEDEMA (swelling of the OPTIC NERVE). Ophthal- ture and bleed. Retinopathy of diabetes moscopy in combination with health history typically develops over decades, is more com- generally provides the information the ophthal- mon in people who require INSULIN THERAPY, and mologist needs to make the diagnosis. is the most common cause of blindness in peo- ple under age 60. Treatment Options and Outlook • Retinopathy of prematurity occurs in some Often retinopathy improves on its own, especially infants born earlier than 32 weeks of gesta- retinopathy of prematurity and central serous tional age in whom the retinal blood vessels, retinopathy. Retinopathy of diabetes or hyperten- which develop late in gestation, have not yet sion typically improves with tighter control of formed. In most infants, the blood vessels the underlying condition. When retinopathy resume growth and establish normal retinal improves, vision may return to its previous state vasculature with no damage to vision. In some or damage to vision may be minimal. Retinopathy premature infants who have retinopathy, inad- that progresses leads to vision impairment, includ- equate blood supply to the retina or abnormal ing total loss of vision. Central serous retinopathy vessel development can cause RETINAL DETACH- tends to recur. Proliferative and nonproliferative MENT with resulting VISION IMPAIRMENT. retinopathy often require laser treatment. • Hypertensive retinopathy develops as a conse- Risk Factors and Preventive Measures quence of untreated or poorly managed HYPER- The key risk factors for most retinopathy are the TENSION (high BLOOD PRESSURE). Blood vessels in the retina, like blood vessels throughout the underlying health conditions associated with the body, become stiff and inflexible as a result of retinopathy. Preventive measures emphasize con- the continuous pressure. This brittleness makes trol of the underlying condition—maintaining sta- them susceptible to rupture, which floods the ble blood glucose levels in retinopathy of diabetes, retina with blood. and healthy blood pressure in retinopathy of hypertension. Consistent PRENATAL CARE and atten- • Central serous retinopathy, in which fluid accu- tion to maternal health (notably SMOKING CESSA- mulates between the retina and the choroid, TION) help reduce the risk for PREMATURE BIRTH. causes the retina to swell and lift up from the Regular ophthalmic examinations can detect choroid. retinopathy in its early stages, allowing therapeu- tic interventions to minimize damage to the eye. Symptoms and Diagnostic Path See also ISCHEMIC OPTIC NEUROPATHY; RETINITIS PIG- Most often, retinopathy does not cause symptoms MENTOSA; TOXIC OPTIC NEUROPATHY. until eye damage becomes significant. When symptoms are present, they may include retrobulbar optic neuritis INFLAMMATION of the OPTIC NERVE outside the globe of the EYE, between • blurred or distorted vision the eye and the BRAIN. Retrobulbar optic neuritis • diminished near vision for reading and other can result from INFECTION such as MENINGITIS or close focus ENCEPHALITIS, as a consequence of toxic exposure, 116 The Eyes and as a manifestation of MULTIPLE SCLEROSIS. COMPUTED TOMOGRAPHY (CT) SCAN of the brain when Symptoms may include the doctor suspects multiple sclerosis or another neurologic cause. Most retrobulbar optic neuritis • PAIN with eye movement eventually goes away without treatment. The doc- • diminished VISUAL ACUITY (blurred or dim tor may prescribe CORTICOSTEROID MEDICATIONS vision) when the inflammation persists. Because retrobul- • eye is tender to touch or pressure bar optic neuritis is so often associated with multi- • blind spots (scotomas) ple sclerosis, the doctor may recommend more extensive NEUROLOGIC EXAMINATION to determine • dulled colors whether this condition is the underlying cause. The diagnostic path includes visual acuity and Recurrent or severe retrobulbar optic neuritis may VISUAL FIELD testing, OPHTHALMOSCOPY to examine result in permanent VISION IMPAIRMENT. the optic NERVE disk (which often becomes more See also OPTIC NERVE ATROPHY; OPTIC NERVE HYPOPLA- pale), and MAGNETIC RESONANCE IMAGING (MRI) or SIA; PAPILLITIS; SCOTOMA; TOXIC OPTIC NEUROPATHY. S

scleritis An INFLAMMATION of the sclera, the white therapeutic course of systemic corticosteroid med- fibrous outer layer of the EYE. The inflammation ication such as prednisone. Prompt diagnosis and develops gradually, involving the connective tissue treatment can preserve the eye and vision. How- structure of the sclera. The scleritis may involve a ever, permanent structural damage to the eye small portion of the sclera (sectoral scleritis) or the with resulting loss of vision is a significant risk entire globe of the eye (diffuse scleritis). Some even with treatment. Scleritis may recur when it people develop nodules that may become necrotic is a manifestation of an underlying connective tis- (cause tissue death). Necrotizing scleritis, with or sue or AUTOIMMUNE DISORDER. without nodules, results in severe damage to the See also CONJUNCTIVITIS; EPISCLERITIS; KERATITIS; eye (including perforation) and often loss of UVEITIS; VISION IMPAIRMENT. vision. More than half of the people who develop scleritis also have connective tissue disorders, the scotoma An area of the RETINA in which there most common associations being with RHEUMATOID are few or no cones or rods, the specialized NERVE ARTHRITIS and VASCULITIS. cells that convert light signals to nerve impulses, creating a blind spot in the VISUAL FIELD. Scotomas CONDITIONS OFTEN ASSOCIATED WITH SCLERITIS may represent healed injuries to the retina such as ANKYLOSING SPONDYLITIS RHEUMATOID ARTHRITIS retinal tears or degeneration of the retina such as SARCOIDOSIS SYSTEMIC LUPUS ERYTHEMATOSUS (SLE) may occur with AGE-RELATED MACULAR DEGENERATION VASCULITIS Wegener’s granulomatosis (ARMD) or GLAUCOMA. A simple test called the AMSLER GRID, a grid of equally spaced vertical and Deep, aching PAIN characterizes scleritis, often horizontal lines, detects scotomas. severe enough to disrupt sleep. Referred pain See also RETINOPATHY. sometimes affects the jaw or cranial bones around the eye. The affected area of the sclera is erythe- slit lamp examination The examination of the matous (“bloodshot”), and the eye typically tears outer EYE using a bright light focused into an elon- in response to light (PHOTOPHOBIA). The eye may gated slit in combination with a biomicroscope. protrude from the front of the orbit when scleritis The examination takes place in a darkened room, involves the back of the eye. The diagnostic path with the person sitting on one side of the slit lamp typically includes SLIT LAMP EXAMINATION and OPH- and the ophthalmologist on the other side. The THALMOSCOPY, and possibly ULTRASOUND to deter- ophthalmologist moves the light across the surface mine whether the inflammation involves the back of the eye to examine the inner eyelids, sclera, of the eye. CORNEA, iris, and LENS. The ophthalmologist may Treatment is topical CORTICOSTEROID MEDICATIONS also put drops in the eyes to dilate the pupils, then and oral NONSTEROIDAL ANTI-INFLAMMATORY DRUGS use the slit lamp to examine the structures at the (NSAIDS), which suppress inflammation as well as back of the eye, such as the RETINA and OPTIC NERVE, relieve pain. Eye drops to constrict the blood ves- as well. The bright light of the slit lamp is some- sels in the eye reduce swelling and redness. Dif- times uncomfortable as it passes across the eye, fuse or severe inflammation may require a especially with dilated pupils that allow the full 117 118 The Eyes intensity of the light to enter the inner eye. The prematurity and becomes apparent in the first few examination takes only a few minutes. months after birth. Most strabismus develops in See also OPHTHALMIC EXAMINATION; OPHTHAL- children between the ages of one and five. About MOSCOPY. half of the time the cause of strabismus in children is unknown (idiopathic) and not associated with Snellen chart The familiar eye chart, featuring any underlying condition. lines of letters and numbers that progressively In adults, strabismus may develop as a conse- decrease in size, to assess VISUAL ACUITY. Dutch quence of TRAUMA TO THE EYE, TRAUMATIC BRAIN ophthalmologist Herman Snellen (1834–1908) INJURY (TBI), or STROKE. Adults may experience developed the chart in the 1860s. The top letter is double vision (DIPLOPIA) or uncoordinated move- typically E. A person with normal vision can read ments of the eyes. Adults also may acquire strabis- a one-inch letter from 20 feet away, designated as mus as a consequence of vision loss in one eye, 20/20 vision. Each line on the chart represents a which results in lack of visual signals that cue the ratio of normal vision. A person who can see at 20 BRAIN for MUSCLE movements of the eye. Common feet what someone who has normal vision could causes of acquired strabismus in adults include see at 60 feet has 20/60 vision. A REFRACTION TEST stroke, trauma, GRAVES’S DISEASE, and other sur- then determines the precise correction necessary gery. to bring visual acuity as close to 20/20 as possible. The diagnostic path includes comprehensive To take a Snellen test, a person reads the smallest ophthalmic and NEUROLOGIC EXAMINATIONS. Timely line possible with each eye separately (one eye treatment in children is essential to prevent AMBLY- covered) and both eyes together. OPIA, in which the brain learns to perceive images See also AMSLER GRID; OPHTHALMIC EXAMINATION; from only one eye. This learning establishes the VISION IMPAIRMENT. brain’s vision pathways, and if untreated becomes a form of permanent vision loss. Strabismus treat- strabismus A condition, also called tropia, in ment may include exercises or surgery to which the eyes do not focus simultaneously on strengthen the eye muscles of the weak eye. the same object. One EYE may turn inward (“cross- See also GRAVES’S OPTHALMOPATHY; OPHTHALMIC eye” or esotropia), or one eye may turn outward EXAMINATION; VISION IMPAIRMENT. (“walleye” or exotropia). Congenital strabismus may occur with RETINOBLASTOMA or RETINOPATHY of stye See HORDEOLUM. T

tonometry A test that measures INTRAOCULAR a combination of these practices, causes various PRESSURE (the pressure within the EYE). The pri- disturbances of vision and ocular function. Severe mary reason for tonometry is to screen for GLAU- or chronic MALNUTRITION, notably vitamin B12 defi- COMA, a condition for which elevated intraocular ciency, also results in toxic optic neuropathy. As pressure is a characteristic symptom. Increased well, numerous medications cause temporary intraocular pressure is also common with ORBITAL visual disturbances, among them sildenafil (color CELLULITIS and GRAVES’S OPHTHALMOPATHY. Tonome- shifts) and antidepressants (distorted perception try is a standard component of the OPHTHALMIC and VISUAL ACUITY). EXAMINATION. There are several methods of tonometry. The POSSIBLE SOURCES OF TOXIC OPTIC NEUROPATHY most commonly used are amiodarone carbon monoxide chloroquine digoxin • applanation, in which the ophthalmologist puts ethambutol ethanol (drinking ALCOHOL) anesthetic drops in the eyes and then touches a ethylene glycol (antifreeze) industrial chemicals device called a tonometer to the surface of the isoniazid lead CORNEA to measure how much pressure it takes mercury methanol (wood ALCOHOL) to depress the cornea methotrexate NONSTEROIDAL ANTI- • noncontact, or air puff, in which the person pyridoxine INFLAMMATORY DRUGS (NSAIDS) stares at a focused light while a device blows a radiation exposure quinine quick puff of air at the cornea, then measures tamoxifen sulfonamide the change in reflected light from the cornea ultraviolet light tobacco use

Elevated intraocular pressure, or intraocular Symptoms and Diagnostic Path HYPERTENSION, requires further evaluation to detect and correct the cause. Intraocular pressure that Most often toxic optic neuropathy develops slowly remains elevated damages or destroys the OPTIC as the consequence of cumulative exposure. NERVE, resulting in total vision loss in the affected Symptoms may include eye. • dimness and diminished clarity See also OPHTHALMOSCOPY; SLIT LAMP EXAMINATION. • altered color perceptions (dyschromatopsia) toxic optic neuropathy Damage to the OPTIC • blind spots in the visual field (SCOTOMA) NERVE, RETINA, and other structures of the EYE as a SIDE EFFECT of medications or exposure to environ- • PHOTOPHOBIA (extreme sensitivity to light) mental or systemic toxins. Many substances can • DIPLOPIA (double vision) harm vision, and any substance that is a neuro- toxin (damaging to the NERVOUS SYSTEM) has the Symptoms progressively worsen with contin- potential to damage the optic nerve. Long-term ued exposure to the toxic substance. Symptoms cigarette smoking or ALCOHOL abuse, and especially may begin in one eye though nearly always 119 120 The Eyes involve both eyes as the effects of the toxic expo- uveitis INFLAMMATION of the uveal structures of sure continue to develop. the EYE, which include the iris, ciliary body, and Treatment Options and Outlook choroid. Uveitis most commonly affects the front Treatment is immediate cessation of exposure to of the eye (anterior uveitis) though may involve the causative agent, though it is unwise and specific segments of the eye or the uveal tract potentially harmful for individuals to stop taking throughout the eye (diffuse uveitis). Symptoms prescribed medications without consulting their can vary from mild to severe and may include physicians. In many circumstances the damage is blurred vision, PHOTOPHOBIA (extreme sensitivity to reversible and normal vision returns after expo- light), burning sensation, prominent blood vessels sure to the toxin ends, though it may take several (“bloodshot” appearance) radiating from the iris weeks to several months for the damage to heal. into the sclera, excessive tearing, and PAIN. GLAU- COMA is a serious potential complication of uveitis Risk Factors and Preventive Measures that can lead to VISION IMPAIRMENT. The primary risk for toxic optic neuropathy is The diagnostic path includes SLIT LAMP EXAMINA- exposure to ocular toxins. Because these are TION and OPHTHALMOSCOPY. Treatment includes numerous and may be prescription or over-the- cycloplegic drops to immobilize the iris, which counter medications, it is important to know the helps subdue the inflammation, and corticosteroid possible side effects of all medications individually drops. Some people need to use corticosteroid as well as in combination. Avoiding ocular toxins drops up to several months. With prompt treat- or stopping medications that cause vision distur- ment, most people recover fully and without dam- bances helps prevent permanent damage to the age to the eye or to vision. Chronic uveitis may eyes. occur with certain AUTOIMMUNE DISORDERS such as See also GRAVES’S OPHTHALMOPATHY; ISCHEMIC OPTIC INFLAMMATORY BOWEL DISEASE (IBD), RHEUMATOID NEUROPATHY; OTOTOXICITY. ARTHRITIS, and REITER’S SYNDROME. See also CONJUNCTIVITIS; CORTICOSTEROID MEDICA- tropia See STRABISMUS. TIONS; EPISCLERITIS; PAPILLITIS; SCLERITIS. V–X visual acuity The ability to see objects clearly which he or she can see the object. The eye care and sharply. Visual acuity assesses central vision specialist may repeat this procedure several times and represents the function of the CORNEA, iris for each eye, measuring peripheral vision from (pupil size), LENS, and RETINA. The SNELLEN CHART, each side, above, and below. Other methods may which presents lines of letters of diminishing size, use computerized flashing lights with the person is the standard measure of visual acuity. Environ- looking at a fixed point (target) within a con- mental factors that influence visual acuity include tained dome. The person presses a button for each lighting and contrast. The most common distur- light he or she sees, and the eye care specialist cre- bances of visual acuity are REFRACTIVE ERRORS such ates a map of each eye’s visual field that allows as MYOPIA (nearsightedness), HYPEROPIA (farsighted- calculation of visual field percentages. ness), and ASTIGMATISM (blurred vision). PRESBYOPIA, age-related changes in the cornea’s CONDITIONS THAT CAN AFFECT THE VISUAL FIELD FLEXIBILITY, affects near-vision visual acuity. AGE-RELATED MACULAR DIABETES See also NIGHT BLINDNESS; VISION IMPAIRMENT. DEGENERATION (ARMD) GRAVES’S OPHTHALMOPATHY GLAUCOMA MULTIPLE SCLEROSIS visual field The total area or scope of vision. EYE HYPERTENSION RETINITIS PIGMENTOSA care specialists map the visual field by measuring RETINAL DETACHMENT SCLERITIS the boundaries of peripheral vision in degrees from RETINOPATHY TRAUMA TO THE EYE the point of central vision. A normal field of vision STROKE tumors of the eye or BRAIN is 135 degrees vertically (60 degrees up and 75 degrees down) and 160 degrees horizontally (100 See also AMSLER GRID; REFRACTION TEST; SCOTOMA; degrees outward and 60 degrees inward). Everyone SNELLEN CHART; VISUAL ACUITY. has a blind spot of about 10 degrees in the direct center of vision, the point at which the OPTIC NERVE vision health Personal care for the eyes to pro- enters the RETINA (the optic disk). The optic disk tect the eyes and preserve vision. The two most contains no rods or cones. Binocular vision (the important elements of vision health are EYE pro- ability to see with both eyes) compensates for each tection and regular ophthalmic examinations. eye’s blind spot with overlapping visual fields for each eye. People who have monocular vision (the Protective Eyewear ability to see only through one eye) learn to accom- Most injuries to the eyes are preventable by wear- modate for the blind spot by frequently moving the ing appropriate protective eyewear, which ranges eye to scan the field of vision. from sunglasses to protect the eyes from sunburn There are several methods for measuring visual to specialized eyewear for specific needs. Such field. The simplest though least precise is for the needs might include eye care specialist to sit across from the person and, with the person looking at a fixed point the • ultraviolet exposure (sunlight, welding) eye care specialist slowly moves a hand or an • sports (protection from contact; protection object such as a pen. The person tells the point at when swimming or diving) 121 122 The Eyes

• eyeglasses (polycarbon lenses for optimal pro- impairments that prevent them from participating tection against shattering) in occupations and activities that have require- • working with power tools ments or legal standards for VISUAL ACUITY (the ability to see clearly) and VISUAL FIELD (the scope of • exposure to environment with high airborne peripheral vision). People who have functional pollutants (such as sawdust) vision, also called low vision, generally have visual acuity correctable to between 20/40 and 20/400. Though regular eyeglasses and sun- More than a million Americans are legally blind. glasses provide some protection against Vision impairment may be temporary or perma- injury, they do not provide adequate nent. protection when working with power tools, during recreational and athletic LEGAL BLINDNESS activities, and for specialized needs VISUAL ACUITY uncorrectable to 20/200 in the better eye, or (such as welding). VISUAL FIELD uncorrectable to greater than 20 degrees

Regular Ophthalmic Examinations Symptoms and Diagnostic Path In the United States, basic screening for eye prob- In children, the symptoms of vision impairment lems takes place shortly following birth (for may be difficult to detect. Those that are obvious infants born in hospitals and birthing centers), at include regular well-child check-ups, through public • STRABISMUS, which indicates AMBLYOPIA school vision screening programs, and as part of • squinting the ROUTINE MEDICAL EXAMINATION. People who have normal vision require only ophthalmic examina- • holding objects very close to the face tions, the need for which becomes more frequent • sitting very close to the television with advancing age as the likelihood of health • frequent headaches conditions that affect vision increases with age. People who have eye conditions, REFRACTIVE Routine screening for EYE and VISION HEALTH ERRORS, HYPERTENSION, DIABETES, and other chronic takes place at birth (for infants born in hospitals health conditions need regular ophthalmic exami- and birthing centers), during routine well-child nations as their physicians or eye care providers visits, and through school vision screening pro- recommend. grams. The diagnostic path for children in whom See also CORRECTIVE LENSES; OPHTHALMIC EXAMINA- screenings detect potential vision problems TION; VISION IMPAIRMENT. includes a complete OPHTHALMIC EXAMINATION with testing for visual acuity, REFRACTIVE ERRORS, and vision impairment The uncorrectable loss of visual field as the child’s needs require. Eye care vision. About 12 million Americans have vision specialists use assessment methods appropriate for

RECOMMENDED ROUTINE EYE EXAMS Age Eye Exam Frequency Birth to 2 years screening at well-child visits 3 to 5 years screening every one to two years at well-child visits 6 to 19 years screening at routine medical exam; ophthalmic exam as needed 20 to 29 years ophthalmic exam once during this time 30 to 39 years ophthalmic exam every five years 40 to 65 years ophthalmic exam every two years 65 years and older ophthalmic exam every year vitrectomy 123 the child’s age, comprehension, and communica- Treatment Options and Outlook tion abilities. Treatment depends on the cause of the VISION IMPAIRMENT. CORRECTIVE LENSES or REFRACTIVE SUR- Sudden loss of vision in one eye or both GERY typically improve vision in conditions such as eyes is an emergency that requires severe MYOPIA or ASTIGMATISM, even if these meas- immediate medical care. ures cannot fully restore normal vision. Surgery is often the solution for vision impairment due to Adults are generally able to perceive symptoms CATARACT, CORNEAL INJURY or deterioration, RETINAL of vision impairment, though when onset is grad- DETACHMENT, and some forms of GLAUCOMA. Med- ual the symptoms are less obvious (though may be ications can control other forms of glaucoma. more apparent to co-workers, friends, and family Vision impairment has a significant effect on members). Sometimes the first indication of a seri- QUALITY OF LIFE. There are numerous assistive ous vision impairment comes with a misfortune devices for people who have functional limitations such as a motor vehicle accident, especially among as a result of vision impairment. Most people who older adults who do not notice or do not acknowl- have vision impairments are able to participate, edge diminishing vision. Symptoms of vision with reasonable accommodations and sometimes impairment include creative effort, in work and recreational activities they enjoy. Continued advances in technology • dimness or changes in color perception generate new treatment approaches that may • need to hold objects closer or farther away offer improved vision. from eyes • frequent headaches or squinting Risk Factors and Preventive Measures Many health conditions can contribute to or cause • loss of sharpness or clarity of vision vision impairment. The most significant are dia- • difficulty reading betes, HYPERTENSION, and glaucoma. Early diagnosis • difficulty seeing at night or in low light and appropriate treatment can limit or prevent • the need for bright lighting damage to the eyes and to vision. Eye protection, such as sunglasses and safety eyewear for activities The diagnostic path includes a comprehensive with risk for impact or debris, is a key preventive ophthalmic examination to assess visual acuity, measure. More than 40,000 preventable eye visual field, and refractive error as symptoms indi- injuries occur every year. Routine ophthalmic cate. Further diagnostic procedures may be neces- examinations detect eye problems early, allowing sary when the underlying cause of vision for the most appropriate and effective interven- impairment appears to be a health condition other tions to preserve vision. than a problem with the eyes, such as MULTIPLE See also BRAILLE; COLOR DEFICIENCY; HEADACHE; SCLEROSIS or DIABETES. MOTOR VEHICLE ADDIDENTS; VISION HEALTH.

COMMON CAUSES OF VISION IMPAIRMENT vitrectomy An OPERATION to remove the vitreous AGE-RELATED MACULAR ALBINISM humor from within the EYE as treatment for RETI- DEGENERATION (ARMD) CATARACT NAL DETACHMENT, vitreous HEMORRHAGE (bleeding AMBLYOPIA congenital into the vitreous humor), RETINOPATHY, and foreign central serous RETINOPATHY CYTOMEGALOVIRUS (CMV) body penetration. In vitrectomy, the ophthalmolo- congenital disorders corneal deterioration gist makes three tiny incisions in the sclera (white GENETIC DISORDERS GLAUCOMA portion) of the eye for the insertion of a cutting INFECTION MULTIPLE SCLEROSIS instrument, a light, and an infusion tube. The cut- RETINAL DETACHMENT RETINOBLASTOMA ting instrument rotates to gently pull the vitreous retinopathy of DIABETES retinopathy of HYPERTENSION humor out of the eye, and the ophthalmologist retinopathy of prematurity STROKE replaces it with a saline-based solution at the same TRAUMA TO THE EYE uncorrectable MYOPIA rate to maintain pressure and stability within the 124 The Eyes eye. Recovery from uncomplicated vitrectomy ment with accompanying flashes of light or large takes about two to three weeks. Complex vitrec- numbers of floaters may indicate RETINAL DETACH- tomy, such as when there is retinal detachment or MENT, an ophthalmologic emergency that requires a macular tear, may require additional methods to immediate treatment. help the eye heal. Recovery from complex vitrec- See also VITRECTOMY. tomy may take several months, though usually preserves vision and the eye. xanthelasma Deposits of fatty plaque that form See also AGE-RELATED MACULAR DEGENERATION; blisterlike lesions on the eyelids, usually the upper CATARACT EXTRACTION AND LENS REPLACEMENT; CORNEA eyelids near the corner of the NOSE. The lesions are TRANSPLANTATION; SURGERY BENEFIT AND RISK ASSESS- yellowish in color and often indicate HYPERLIPI- MENT. DEMIA (elevated BLOOD levels of cholesterol and triglycerides). Though harmless, the lesions can vitreous detachment The separation of the vit- cause the eyelid to droop, obscuring vision when reous humor, the gelatinous substance within the an upper lid and interfering with lid closure when EYE, from the RETINA. Vitreous detachment com- a lower lid. A plastic surgeon can remove the monly occurs with advancing age as the vitreous lesions in a simple outpatient OPERATION, though humor thins and takes on more of a liquid consis- the lesions tend to recur, particularly when blood tency. By itself vitreous detachment is harmless lipid levels remain high. and has no effect on vision, though it typically See also BLEPHAROPLASTY; CHOLESTEROL BLOOD LEV- produces FLOATERS (fragments of tissue that float ELS; LESION; SURGERY BENEFIT AND RISK ASSESSMENT; through the vitreous humor). Vitreous detach- TRIGLYCERIDE BLOOD LEVEL. THE INTEGUMENTARY SYSTEM

The integumentary system encloses the body, protecting it from, as well as allowing its interactions with, the external environment. Physician specialists who treat conditions of the SKIN, HAIR, and NAILS are dermatologists. This section, “The Integumentary System,” presents an overview of the structures and functions of the integumentary system, a dis- cussion of dermatological health and disorders, and entries about the health conditions that can affect the skin, hair, and nails.

Structures of the Integumentary System What looks remarkably the same from day to day SKIN SEBACEOUS GLANDS is, in reality, always changing. epidermis sebaceous In the beginning Attesting to the skin’s impor- dermis ducts tance for survival and function, the skin and subcutaneous layer NAILS the BRAIN are the first two distinctive organs to SWEAT GLANDS cuticle emerge during embryonic development. The cells eccrine sweat glands nail of each arise from the primitive neural crest, also apocrine sweat glands nail bed called the neuroectoderm. By three weeks of ges- HAIR matrix tational age the neural crest differentiates. The follicle (nail root) cells that migrate inward become NERVE cells, shaft forming the brain and SPINAL CORD. The cells that migrate outward become the two major cell types Functions of the Integumentary System of cells that form the skin: keratinocytes and The integument, from the Latin word for “cloak,” melanocytes. covers the body. Its structures—the SKIN, HAIR, and By seven weeks gestational age the skin devel- NAILS—form the image the body presents to the ops hair follicles that, six weeks later, begin to outside world. Its functions—protective barrier, cover the head with hair. At 20 weeks gestational tactile perception, temperature regulation, IMMUNE age that hair coat, called lanugo, has spread to RESPONSE—enable the body to survive in that out- cover the entire body. Some babies, especially side world. those born prematurely, still sport this coat at The foundation of the integumentary system is birth, which is often disconcerting to anxious par- the skin, which, as the body’s largest organ, ents but quickly falls away. The formation and accounts for 15 percent of the body’s weight. It function of the sebaceous glands parallels that of sheaths the body in protective insulation from the hair follicles. As hair begins to sprout, the scalp to sole, coating every stretch and fold sebaceous glands secrete a thick, ointmentlike between. The skin’s three layers—epidermis, der- precursor to sebum, called vernix, that covers the mis, and subcutaneous layer—form the interface skin’s surface. Vernix establishes a waterproof bar- between the body’s internal and external environ- rier that protects the skin as the FETUS floats in ments. The endless exchange of information is so AMNIOTIC FLUID. Also by 20 weeks the skin contains wearing that the skin completely replaces its out- SWEAT GLANDS, eyelashes and eyebrows, fingernails ermost layer, the epidermis (about 36,000 square and toenails, and the unique surface ridges on the inches of surface area), every three to four weeks. fingertips that will become fingerprints.

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The Integumentary System 127

Renewal and protection: the epidermis The pri- RESPONSE mediator. After they mature in the stra- mary cells of the skin’s surface layer, the epidermis, tum germinativum, keratinocytes pick up melanin are melanocytes, which produce the pigment granules and begin their migration to the surface. melanin, and keratinocytes, which produce the The three and a half week journey to the stratus fibrous protein keratin. Both types of cells arise corneum is a final rite of passage that literally from the base level of the epidermis, the stratum squeezes the life from the keratinocytes. During germinativum (“birth”), also called the basal level this passage, the keratinocytes undergo denu- or the Malpighian level. As the Latin name implies, clearization, a process of nucleus deterioration this level germinates, or originates, cells. Melan- that gradually diminishes cell function. The ocytes remain in the stratum germinativum for all upswell of continuous movement that carries the of their existence. Keratinocytes migrate upward to keratinocytes along compresses their remaining the stratum corneum (“horny”), the cornified or cell structure. By the time the keratinocytes break hardened surface level of the epidermis. through to the surface, they are flat, brittle, and Melanocytes produce melanin, the pigment lifeless husks of keratin. They layer tightly against that gives color to the skin, hair, and eyes (iris). one another, forming the tough covering the skin This color has a purpose: melanin is the skin’s pri- presents to the outside world. The friction of inter- mary protection against the sun’s ultraviolet rays. acting with the external environment brushes It absorbs ultraviolet lightwaves, preventing them them loose and they fall away, a process called from causing damage to cell structure and func- exfoliation. Keratinocytes that funnel through the tion. Melanocytes store the enzyme tyrosinase, hair follicles become hair shafts. which other cells in the body produce, and acquire the amino acid tyrosine from the circulat- WHY A WOUND THAT FAILS TO HEAL ing blood. The tyrosinase catalyzes a series of MAY SUGGEST SKIN CANCER chemical actions that convert tyrosine to two The epidermis completes a total turnover of cells every tones of pigment: eumelanin (black-brown pig- 24 to 28 days, meaning that this outer layer of the SKIN ment) and pheomelanin (yellow-brown pigment). is fresh and new about once a month. Any skin wound The melanocytes package these pigments into that takes longer than three or four weeks to heal rep- granules collectively called melanin. resents an area of cells that is growing at its own pace, Melanocytes also pigment cells in other organs. distinct from the other skin cells—in short, a CANCER. When the neural crest differentiates early in embryonic development, some melanocytes Structure, sustenance, and sense: the dermis migrate with the cells that form the structures of The skin’s middle layer, the dermis, nurtures and the brain. A dense population of melanocytes set- supports the skin. Primarily fibrinogens create a tles in a structure in the midbrain, the substantia collagen matrix that supports an abundant and nigra (a name that means “black substance”). The effusive network of blood vessels, nerves, and melanocytes pigment specialized cells in the sub- glands (sweat and sebaceous). These structures are stantia nigra that produce DOPAMINE, a brain NEURO- elemental to the body’s heat regulation mecha- TRANSMITTER essential to neuromuscular function. nisms. The dermis also contains the Langerhans When melanocytes in the skin slow melanin pro- cells, the gatekeepers of the SKIN-ASSOCIATED LYM- duction, the result may be depigmentation disor- PHOID TISSUE (SALT) that are the front line of the ders such as VITILIGO or white hair. Though often body’s immune response. distressing, these consequences are not serious The tiny blood vessels—arterioles and threats to health and life. When melanocytes in the venules—that web through the dermis cause the substantia nigra stop producing melanin, however, skin to flush when the body is too warm. This the substantia nigra stops producing dopamine, and function of heat regulation uses the BLOOD vessels the body stops moving, a degenerative condition for conduction heat dispersal, dilating them to called PARKINSON’S DISEASE. bring a flood of blood to the cooler temperatures Keratinocytes produce two proteins: keratin, a near the surface. The vessels contract when body fibrous substance, and cytokine, an IMMUNE temperature returns to an acceptable range, send- 128 The Integumentary System ing the blood back within the body’s core. This responses. The structures that detect heavier pres- same mechanism also responds to strong emotions sure, the corpuscles of Ruffini and the Pacinian such as fear or embarrassment, similarly sending corpuscles, reside deeper in the dermis, near or blood rushing to the skin. The blood supply of the extending beyond the subcutaneous border. dermis also nourishes the epidermis, supporting Cushion and connection: the subcutaneous the perpetual production of new cells in the stra- layer The subcutaneous layer, also called the tum germinativum. hypodermis, contains mostly adipose tissue (body About 5 million sweat glands aid both tempera- fat) and some connective tissue. The adipose tissue ture and fluid regulation, dripping out about 500 warehouses the excess calories the body converts milliliters of somewhat salty water every hour. to fat, varying in thickness to accommodate this Most of this moisture evaporates without con- stored energy source. A rich network of blood ves- scious awareness of its presence. Sweating sels and nerves permeates the subcutaneous layer, becomes an obvious event only when it becomes supplying nourishment to all layers of the skin profuse, as with intense exercise or heat, or in and conducting nerve impulses from sensory conditions such as HYPERHIDROSIS. The eccrine receptors and other nerve structures. The subcuta- sweat glands secrete their fluid directly to the sur- neous layer gives shape and context to the skin, face of the skin through sweat pores. The apocrine softening the protrusions and angles of the under- sweat glands, found primarily in the axillae lying musculoskeletal structures. It also cushions (underarms) and groin areas, secrete their fluids those underlying structures from the multitude of into the hair follicles. Sweat from the eccrine minor traumas the body’s surface experiences glands is water and electrolytes (salts), while that every day. from the apocrine glands contains lipids and pro- The connective tissue of this deepest layer of teins to help it mix with the sebum in the hair fol- the skin binds the upper skin layers to the internal licles. These extra substances account for the structures of the body, overlaying the muscles. familiar odor of sweat as well as the yellowish Fibers of connective tissue lace from the subcuta- stains sweating leaves in the underarm areas of neous layer upward into the epidermis and down- clothing. ward to the musculoskeletal structures, holding the skin in place. These connections allow the skin THE SUNLIGHT VITAMIN to respond to the movement of muscles beneath Though the negative consequences of ultraviolet light it. In locations such as the knuckles, the connec- get the most press, sunlight is a valuable resource for tions are loose (appearing deeply creased) to strong bones and TEETH. The dermis contains ergosterol, accommodate substantial motion. In the face, by a chemical that ultraviolet light converts into vitamin contrast, the skin tethers tightly to the underlying D, which the body needs to use calcium to build BONE structures. When the facial muscles move the skin and tooth enamel. on the face moves, too, forming facial expressions. The hair Hair has different characteristics and Millions of specialized nerve endings reside functions, depending on its location on the body. within the dermis, gathering data about tempera- Though in many other mammals hair may serve ture, humidity, motion, and contact, which they for protection and heat regulation, in humans hair transmit to the NERVOUS SYSTEM. The skin is the has mostly lost these purposes. The exceptions are organ of tactile perception, the sense of touch. The the hair on the head and a man’s unshaven beard, highest concentrations of tactile receptors are in which help preserve heat and shelter the skin the fingertips, the lowest on the soles of the feet. from sunburn. Hair in other locations has specific The key structures that detect touch are the discs functions. Hair in the auditory canal and in the of Merckel (light touch) and the corpuscles of nasal passages helps move debris to the outside of Meissner (moderate touch), specialized nerve end- the EAR and NOSE, respectively. The eyebrows keep ings that transmit impulses to specially dedicated sweat from running into the eyes, and the eye- regions of the cerebral cortex that interpret the lashes help prevent environmental debris such as nerve messages and initiate the appropriate dust or pollen particles from entering the eyes. The Integumentary System 129

Deep at the base of the hair follicle within the The nails cover the top portion of the fingers and dermis (middle layer of the skin) is the hair root, toes. Though they may appear to have little more which forms the cells that will become the hair function than to serve as decorative platforms, the fiber. At their formation, hair cells are pliable, liv- nails give the fingers (and to more limited extent, ing, and colorless. The new cells that emerge from the toes) the ability to grip, pry, and scratch. The the root divide, pushing the cells that preceded nails also give firmness and STRENGTH to the ends of them upward into the hair follicle. As the cells the fingers, and help protect the sensitive fingertips. rise, they move beyond the range of the blood vessels that bring nourishment to the hair root Health and Disorders of the Integumentary System and so die. The skin performs its myriad functions with By the time hair cells rise above the surface of remarkable consistency. Because it replaces its the skin, they are hard and compressed into an outer layer every three to four weeks, the skin elongated, two-layer fiber. The inner layer, the remains relatively healthy for most of the lifespan. cortex, is about three or four cells thick, composed However, well over a thousand disorders, diseases, of melanocytes and keratinocytes. Melanocytes and conditions can affect the skin, hair, and nails. form the melanin (pigment) that gives hair its While a few can cause permanent tissue damage color and. Large, numerous melanocytes result in or even death, most are fairly benign. black or brown hair; small, scattered melanocytes result in red or blond hair. A reduction in the Traditions in Medical History number of melanocytes results in gray or white For millennia the internal structures of the body hair. The keratinocytes produce the keratin that mystified and confounded healers and physicians. gives hair its structure. A single layer of cells, the The skin, however, was right there on the outside cuticle, encases the cortex. The rounder the hair of the body for all to see and touch. The skin’s fiber, the straighter the hair. Curly or kinky hair accessibility gave it a perceived, and erroneous, fibers are flat. simplicity as nothing more than the body’s cover- A hair follicle on the scalp typically grows hair ing. Not until the electron microscope made it for three to five years, then enters a period of dor- possible to explore the molecular structures of the mancy that lasts a few months after which time it body did scientists begin to understand the true drops the hair and the growth cycle begins anew. complexity and intricate functions of the skin. Some people can grow hair for longer, up to seven Today doctors recognize that the skin is a com- or eight years, while others have a shorter growth plex and multifunctional organ. Its appearance period. The amount of time hair grows influences reveals much about the body’s internal functions though does not regulate the hair’s length; a per- and a person’s health status. Numerous systemic son with a short growth period can have hair that health conditions reveal or manifest themselves grows rapidly. through changes in the skin, hair, and nails. Dis- Between 10 and 20 percent of the body’s hair coloration of the skin, for example, may suggest follicles are dormant at any one time. Hair follicles SUNBURN (red), JAUNDICE and LIVER disease (yellow), elsewhere on the body have shorter growth cycles or cardiovascular or pulmonary disease (cyanotic than those on the head. The hairs of the eyebrows blue). Variations on discoloration accompany regenerate every 100 days or so, for example. An numerous rashes. The characteristics of skin erup- individual’s genetic composition determines the tions are often unique to specific diseases, such as shape, color, and length of hair fibers. The cells of the pustules of CHICKENPOX and the papules of the hair fibers within most of the hair follicle and MEASLES. Disturbances of the fingernails and toe- visible above the skin’s surface are dead and do nails may similarly portend underlying health not require nourishment or have sensory capabil- conditions such as iron-deficiency ANEMIA ity. Their keratin content and cuticle layer keeps (koilonychia or spooning) or EMPHYSEMA (yellow them attached to the body. nail syndrome). And hair loss, always emotionally Fingernails and toenails Keratin also gives the distressing, may be a harbinger of undiagnosed fingernails and toenails their shape and hardness. thyroid disease or toxic exposure. 130 The Integumentary System

CONDITIONS THAT CAN AFFECT THE INTEGUMENTARY SYSTEM

ACNE ACROCHORDON ACTINIC KERATOSIS ALBINISM ALOPECIA ANGIOMA BURNS CANDIDIASIS CARBUNCLE CELLULITIS CHLOASMA DISCOID LUPUS ERYTHEMATOSUS CORNS CRADLE CAP DANDRUFF DECUBITUS ULCER DERMATITIS DERMATOFIBROMA DIAPER RASH ECCHYMOSIS ERYSIPELAS erythema ERYTHRASMA FOLLICULITIS FROSTBITE FURUNCLE HYPERHIDROSIS IMPETIGO KAPOSI’S SARCOMA KERATOACANTHOMA KERATOSIS PILARIS LENTIGINES LICHEN PLANUS LICHEN SIMPLEX CHRONICUS LIPOMA malignant melanoma MILIARIA ONYCHOMYCOSIS PEDICULOSIS PEMPHIGUS PRURIGO PRURITIS PSORIASIS PSUEDOFOLLICULITIS BARBAE PURPURA RASH ringworm ROSACEA scleroderma SKIN CANCER SUNBURN TELANGIECTASIS TINEA TOXIC EPIDERMAL NECROLYSIS VITILIGO warts XANTHOMA

Breakthrough Research and Treatment Advances treatment. Dermatologists diagnose these cancers Among the most exciting advances in derma- in 1 million Americans each year. Health experts tology are new techniques in SKIN REPLACEMENT and attribute the success in reducing serious conse- new laser technologies, which vastly extend treat- quences and death from these cancers to nearly nil ment options for a wide spectrum of health condi- to the combination of effective sunscreens to pre- tions involving the skin. Skin replacement vent the sun damage that causes these skin cancers techniques such as synthetic skin and tissue and improved techniques for detecting and remov- expansion promise new hope for reconstruction ing cancerous and precancerous lesions. following severe BURNS, trauma, and CANCER sur- The rapid and continual regeneration of the gery. Refinements in laser technology allow der- epidermis intrigues researchers, who continue to matologists and surgeons to finely pinpoint explore the molecular foundations of this func- potentially damaging or deadly cancer cells to tion. Some scientists believe that there are correla- eradicate them without destroying adjacent tis- tions between KERATINOCYTE replication and stem sues. Lasers also offer potential relief from severe, cells that could hold important clues to under- disfiguring dermatologic conditions such as PSORIA- standing what determines how a cell becomes spe- SIS and ACNE. As well, knowledge emerging from cialized for certain functions. Stem cells have the HUMAN GENOME mapping is helping researchers unique ability to differentiate, or become various identify the causes of persistent or debilitating kinds of particular cells, depending on the stimu- conditions such as vitiligo and PEMPHIGUS. lation they receive. Researchers involved in this Among the greatest successes in modern medi- line of investigation are hoping to find ways to cine is the virtual elimination of skin cancer as a redirect keratinocytes to form other kinds of cells, threat to life. Basal cell carcinoma and squamous which has exciting implications for guiding the cell carcinoma, the most common skin cancers, are body to heal itself by growing healthy tissues to nearly 100 percent curable with early detection and repair or replace diseased organs and structures. A

acne INFLAMMATION of the SKIN’s sebaceous struc- hurt or itch. As the sebaceous structures become tures, also called acne vulgaris, that results in more inflamed, the bumps enlarge into closed eruptions on the skin surface commonly called (whiteheads) or open (blackheads) lesions. pimples, whiteheads, and blackheads. Acne occurs Lesions that form near the surface of the follicles when excessive sebum traps BACTERIA and skin are pimples; those that expand below the surface cells, clogging the follicles. The clogged follicles of the skin are nodules or cysts. The most serious provide an ideal incubator for the bacteria Propi- form of acne is nodulocystic acne, in which onibacterium acne, which is normally present on the numerous nodules and cysts form deep within the surface of the skin where continuous exposure to follicles though inflammation that extends above the air keeps it in check. Within the airless envi- the skin’s surface. Nodulocystic acne typically ronment of a clogged hair follicle, however, these leaves scars or pits after the lesions heal, and may anaerobic bacteria, which do not require oxygen, extensively damage the skin. thrive. Symptoms and Diagnostic Path Acne is most common in PUBERTY and is a conse- The symptoms of acne are its characteristic bumps quence, most doctors believe, of the natural surge and lesions, making diagnosis fairly straightfor- in sex HORMONE production, notably TESTOSTERONE, ward. Doctors diagnose acne on the basis of its that heralds the onset of puberty. Testosterone appearance and the hormonal stages the individ- stimulates the sebaceous glands surrounding the ual may be going through. Acne that does not fit HAIR follicles, increasing their production of sebum, the characteristic presentation may be a symptom a thick, oily substance that helps lubricate the skin. of an endocrine disorder that allows elevated Women experience hormonal changes during MEN- testosterone levels, such as POLYCYSTIC OVARY SYN- STRUATION, PREGNANCY, and MENOPAUSE that may DROME (PCOS) or CUSHING’S SYNDROME. Laboratory cause acne outbreaks, because estrogen suppresses tests to measure hormone levels can assess this sebum production. Newborn infants may develop possibility. Rarely, the doctor may choose to BIOPSY acne during the first few weeks of life, a reaction to several lesions to confirm the diagnosis. the surge of hormones the infant receives from his or her mother in the few days before birth. Treatment Options and Outlook Contrary to popular belief, foods high in fats or sug- Treatment for acne targets reducing inflammation, ars, such as french fries or donuts, have little if any sebum production and accumulation, and the influence on acne. However, cosmetics and oily presence of infective agents such as P. acne. Prod- products applied to the skin that block the seba- ucts may be topical (applied to the affected areas ceous structures can contribute to or aggravate of the skin for localized effect) or systemic (med- acne outbreaks. ications taken by mouth for generalized effect). P. Acne commonly erupts on the face, upper acne tends to develop resistance to antimicrobial back, and chest as these areas contain large num- products over time, making it necessary to switch bers of hair follicles. Acne seldom affects scalp fol- among medications for optimal effectiveness. licles. An outbreak begins as small, reddened Acne is self-limiting and will improve over time bumps, called comedones or papules, that may without treatment, though severe acne may leave 131 132 The Integumentary System scars. Products to treat mild to moderate acne are ends further acne outbreaks because the available without a doctor’s prescription. Prescrip- isotretinoin permanently alters the structure and tion-only medications, such as topical and oral function of the sebaceous structures. However, antibiotics, are necessary for moderate to severe oral isotretinoin has numerous, and potentially acne. Most people use several kinds of products serious, side effects that make it a treatment concurrently. option when other methods have failed to control Over-the-counter products and self-care Prod- the acne. All of the retinoids can cause BIRTH ucts available without a doctor’s prescription to DEFECTS; women who are or could become preg- treat acne generally contain astringents, exfoliants, nant should not use these medications. Oral con- and antimicrobials, sometimes in combination with traceptives (birth control pills) often improve acne one another. The common product Clearasil, for that follows the MENSTRUAL CYCLE. example, combines resorcinol, which slows the production of keratocytes, and sulfur, an antimi- COMMONLY PRESCRIBED MEDICATIONS FOR ACNE crobial. Such products cleanse excess oils, debris, Antibiotics and dead cells from the skin. Antiseptic or antimi- erythromycin (topical and oral) minocycline (oral) crobial substances help suppress P. acne and other tetracycline (topical and oral) doxycycline (oral) bacteria normally present on the skin, reducing the sulfacetamide (topical) potential for INFECTION and inflammation. Retinoids isotretinoin (topical and oral) tretinoin (topical) COMMON INGREDIENTS IN OVER- adapalene (topical) tazarotene (topical) THE-COUNTER ACNE PRODUCTS Product Actions Outlook Acne is self-limiting. Most acne ceases acetone astringent when the body’s hormone levels stabilize. For ALCOHOL antimicrobial adolescents, this occurs at the culmination of benzoyl peroxide antimicrobial, exfoliant puberty, generally by the late teens (females) or lactic acid exfoliant, mild antimicrobial early twenties (males). In women, acne outbreaks resorcinol exfoliant may occur regularly with the menstrual cycle. salicylic acid exfoliant, astringent Acne related to the hormonal changes of preg- sulfur antimicrobial nancy generally goes away within three months of childbirth. Acne is uncommon in post- Prescription medications The two general cate- menopausal women. gories of medications doctors prescribe for acne Risk Factors and Preventive Measures are antibiotics and retinoids, in topical and oral Because acne results from a convergence of fac- forms. ANTIBIOTIC MEDICATIONS target bacteria such tors, key among them hormonal shifts in the body, as P. acne. Oral antibiotic therapy may extend over there are no known measures for preventing its six months or longer, at doses lower than those occurrence. Many myths have prevailed through typically prescribed to treat acute infections. the years about the relationship between foods and acne. Though nutritious eating habits are Isotretinoin causes BIRTH DEFECTS. Cur- important for overall health and development as rent practice standards require two well as the skin’s general health, foods do not negative PREGNANCY tests and use of reli- influence the course or severity of acne. Similarly, able CONTRACEPTION (such as oral contra- though poor hygiene contributes to numerous ceptives) before dermatologists may problems with the skin and may exacerbate acne prescribe isotretinoin therapy for by encouraging the growth of bacteria, it does not women of childbearing age. in itself cause acne. Diligent daily hygiene, such as gentle cleansing In people who have severe or pitting acne, with an antibacterial soap, helps prevent acne treatment with oral isotretinoin nearly always lesions from becoming infected. Zealous washing actinic keratosis 133 and scrubbing can aggravate acne, causing which lesions will remain benign and which will increased inflammation and irritation. Harsh soaps turn cancerous. that dry the skin may temporarily reduce surface Symptoms and Diagnostic Path oils but can cause flaking and other problems. The lesions of actinic keratosis follow a typical and Using an astringent according to the doctor’s consistent progression of symptoms. Actinic ker- instructions can draw excess oils from the seba- atosis begins with a small, scaly patch of skin that ceous structures without so much irritation to the may itch. It often appears to heal or peel off, then surrounding skin. Dermatologists often recom- recurs. The LESION may be grayish, may reddened mend lubricating lotions and creams that do not (erythematous), or may be the same color as the block the pores to help maintain the skin’s mois- skin. Most people first feel rather than see the ture. lesion. As changes to the skin cells at the site con- See also DERMATITIS; FOLLICULITIS; KERATOCYTE; tinue, the lesion becomes more defined and LESION; MILIARIA; NODULE; PAPULE; ROSACEA; SEBA- apparent. The lesion may resemble a wart, or may CEOUS GLAND. become hardened and overgrown, developing a tough, thick texture (hyperkeratosis). acrochordon A polyp that commonly grows Because the progression of actinic keratosis is externally from SKIN folds, such as those around so characteristic, the dermatologist generally the eyelids and on the neck, underarms, and makes the diagnosis on the basis of appearance groin. Also called a skin tag or fibroepithelial and history of sun exposure. The dermatologist polyp, an acrochordon is noncancerous and harm- may choose to biopsy larger or suspicious lesions less (benign). Doctors do not know what causes to determine whether they have progressed to acrochordons to develop. Some acrochordons con- squamous cell skin cancer. Unless such suspicion tain one of the HUMAN PAPILLOMAVIRUS (HPV) strains, exists, there is no need for biopsy because the though others do not. Acrochordons become more standard treatment is to remove the lesion, which common with advanced age, and are most likely consequently eliminates the lesion’s risk for evolv- to appear in people who are between the ages ing into a cancer. of 50 and 75. Unlike intestinal polyps, acrochor- dons do not become cancerous. The dermatologist Treatment Options and Outlook may remove an acrochordon that is in a location Treatment for actinic keratosis is removal of exist- of frequent irritation or cosmetically unaccept- ing lesions coupled with regular (every 6 to 12 able. months) examinations of the skin to detect new See also INTESTINAL POLYP; PLASTIC SURGERY. lesions. Methods for removing the lesions include actinic keratosis Precancerous growths (lesions) • cryotherapy, such as liquid nitrogen, which on the SKIN, also called solar keratosis, that freezes the lesion, causing the cells to die and develop as a consequence of damage from overex- slough away posure to the sun. Actinic keratosis becomes more • electrocautery, which burns away the lesion common with advancing age. Lesions are most • curettage, in which the dermatologist scrapes common on the face, scalp, chest, hands, and off the lesion using a sharp surgical blade arms though can develop anywhere on the body that receive extensive sun exposure. In their early • topical application of a chemotherapy agent, stages, the lesions appear scaly and rough, and which causes the cells in the lesion to die and bleed easily. In later stages, the lesions acquire a slough away wartlike appearance. Most squamous cell SKIN • photodynamic therapy, in which the dermatol- CANCER arises from actinic keratosis. Removing the ogist applies a photosensitive chemical that lesions prevents them from developing into CAN- accumulates in the affected cells and then CER. Between 10 and 20 percent of untreated administers certain frequencies of light expo- actinic keratosis develops into squamous cell skin sure that cause the cells containing the photo- cancer, though it is not possible to determine sensitive chemical to die 134 The Integumentary System

Treatment may cause discomfort. Small lesions aging, integumentary changes that occur with typically heal in two to three weeks with minimal Though the premise of aging tends to conjure or no scarring. Larger or numerous lesions may images of WRINKLES and gray HAIR or baldness, the result in pitting and scarring that will require sub- SKIN, hair, and NAILS undergo numerous changes sequent cosmetic treatment. Though removal ends across the lifespan. the threat of squamous cell skin cancer from exist- ing lesions, the likelihood is high that new lesions Integumentary Changes in Youth will develop. Dermatologists recommend annual During infancy and early childhood, the integu- or semiannual skin examinations for people who mentary structures are soft and the hair may be have had actinic keratosis lesions removed. fine. By about age 10 or 11 years, the hormonal shifts of PUBERTY are under way. Isolated pimples Risk Factors and Preventive Measures may break out on the face, chest, and back. Hair Actinic keratosis develops only in people who patterns begin to change as the sex hormones have repeated or severe exposure to the sun or stimulate SECONDARY SEXUAL CHARACTERISTICS such other sources of ultraviolet radiation such as tan- as axillary (underarm) and pubic hair growth. ning booths. It reflects longstanding damage, typi- Within a few years the hair on the legs thickens cally that occurred in childhood or over decades of and darkens, and boys begin to sprout facial hair. sun exposure in adulthood. The lesions emerge The sebaceous structures kick up sebum produc- and progress over years and are most common in tion, and the dermis accelerates cell production to people age 50 and older. accommodate new skin to cover what can amount People who are likely to develop actinic kerato- to several inches of new height each year. ACNE, sis are those who: an inflammatory process involving the sebaceous structures, is the most common skin condition • experienced severe SUNBURN as children (blister- that occurs between the ages of 14 and 22. ing and peeling) The skin, hair, and nails outwardly remain rela- • are fair skinned and do not tan easily tively stable during young adulthood, the third • work outdoors and fourth decades of life, though are collecting the cumulative effects of factors such as sun expo- • engage in outdoor activities such as gardening sure, scarring, and other evidence of life experi- and sailing that result in prolonged sun expo- ence. People who work outdoors or participate in sure outdoor activities begin to show these effects ear- • live in areas where sun intensity is high, such lier than their counterparts who limit their expo- as the southern United States sure the natural elements. Repeated sun exposure may result in tanning, a look that may be fashion- Preventive measures include avoiding outdoor ably desirable though also causes LENTIGINES (freck- activities during the highest intensity of sunlight les and “age” spots), roughness, and wrinkles. The (typically 10 a.m. to 3 p.m. daily) whenever possi- hands may develop calluses and the feet CORNS. ble, and diligent SUN PROTECTION when outdoors during daylight hours. Dermatologists recommend Integumentary Changes in Midlife wearing a full-brimmed hat and long sleeves At about age 40 the connective tissues throughout when extended sun exposure is unavoidable and the body begin to gradually lose elasticity, allowing applying sunscreen to the face, backs of the hands, the skin to sag and form more wrinkles. and other skin surfaces that remain exposed. Sun- Dermatologists call this loss elastosis. As well, the screen should have a sun protection factor (SPF) epidermis (outer layer of the skin) and the adipose rating of 15 or higher and protect against both tissue (fat) beneath the skin both thin. The epider- ultraviolet A (UVA) and ultraviolet B (UVB). mis becomes more fragile and susceptible to punc- See also LENTIGINES; SKIN SELF-EXAMINATION. tures and tears. Though losing a little fat under the skin might sound like a benefit when other areas of age spots See LENTIGINES. the body are demonstrating an age-related propen- albinism 135 sity to accumulate fat, the diminished integumen- of the skin all through life, beginning in child- tary adipose tissue reduces the skin’s ability to reg- hood. Appropriate nutrition, protection from the ulate heat loss and retention. The older people get, sun and other elements of weather, and good the greater their tendency to feel cold even when hygiene are simple, yet effective, measures to keep the external environment is warm. The risk for the skin healthy throughout life. heat and cold injuries affecting the skin, such as See also CALLUS; FITZPATRICK SKIN TYPE; sunburn and frostbite, also increases. MELANOCYTE; SCAR. By midlife even the skin of those who are not the outdoors types usually has weathered signifi- albinism A genetic disorder in which the cant exposure to sun, wind, and chemicals that melanocytes do not produce, or produce reduced can cause trauma and damage. ACTINIC KERATOSIS,a amounts of, melanin, the chemical that deposits condition of precancerous growths on sun- pigment in cells of the SKIN, HAIR, and structures of exposed skin, and SKIN CANCER such as basal cell the EYE. Without melanin, the skin, eyes, and hair carcinoma or squamous cell carcinoma, may man- have little or no pigment and consequently lack ifest, arising from skin damage that occurred color. People who have albinism typically have decades earlier. Sunscreen, the mainstay of SUN light to white skin and hair, and light or no color PROTECTION for children today, had not yet been to the irises of the eyes (the pigmented rings developed during the childhoods of those who are around the center of the eyes). Albinism reduces today over age 30. or eliminates the skin’s ability to protect itself Age-related changes begin to affect the hair in from exposure to ultraviolet light, greatly increas- midlife, too. Melanocytes, skin cells that produce ing the risk for damage such as SUNBURN and SKIN melanin, thin from the hair follicles, diminishing CANCER. the amount of pigment that appears in new hair The lack of pigmentation characteristic of fibers. Reduced pigment produces hair that appears albinism extends to the interior of the eye as well, gray; complete absence of pigment produces white resulting in VISION IMPAIRMENT. In the normal eye hair. These changes occur regardless of the hair’s the RETINA, the inner lining of the back of the eye natural hair color. Men and women both experi- that receives light images and encodes them as ence patterned ALOPECIA (hair loss), though in men NERVE signals for the OPTIC NERVE to carry to the the loss of hair is generally more pronounced. BRAIN, is highly pigmented such that it appears black. The pigment suppresses extraneous light Integumentary Changes in Late Life and supports the functions of rods and cones, the By the seventh, eighth, and ninth decades of life, specialized cells of vision that line the retina. the epidermis becomes so thin as to reveal the col- Without the protection of pigment, unfocused oration of the tissues that lie beneath the skin. The lightwaves bombard the retina. The brain cannot skin drapes loosely over the body, tearing and sort the resulting nerve signals into images and bruising easily. Blood vessels ridge beneath the consequently fails to properly establish the neuro- skin like pipe cleaners under wet tissue paper, logic pathways that make vision (the interpreta- trailing along the backs of the hands and arms and tion of patterns of light as images) possible. on the lower legs and feet. Threadlike networks of There are a number of INHERITANCE PATTERNS for capillaries etch across the cheeks. Late in life, the albinism, nearly all of which are recessive (require skin continues to do a remarkable job protecting a defective pigmentation GENE from each parent). the body, yet is especially vulnerable to damage. Researchers have identified several types of gene mutations that cause most forms of albinism. Maintaining Healthy Skin Across the Lifespan Oculocutaneous albinism (OCA) The three Anti-aging remedies abound, and some—such as types of OCA involve the skin, hair, and eyes to those that add moisture and vitamins to the varying degrees. skin—help the skin remain supple and smooth longer in life than without their use. But the most • OCA type 1 results from a MUTATION of the gene effective anti-aging approach is to take good care that encodes tyrosinase, an enzyme necessary 136 The Integumentary System

to convert the essential amino acid tyrosine to light) are common and also manifest early in melanin. OCA type 1 features nearly complete infancy. absence of pigmentation and usually legal The characteristic absence of pigmentation is blindness (refractive correction can achieve fairly conclusive for diagnosis of albinism. A thor- vision no better than 20/200). ough OPHTHALMIC EXAMINATION with OPHTHAL- • OCA type 2 results from a mutation of the P MOSCOPY reveals the retina’s hypopigmentation. A gene, which encodes proteins that participate in VISUAL ACUITY test demonstrates the degree of pigmentation. OCA type 2 features moderate vision impairment. GENETIC TESTING can identify pigmentation and moderate vision impairment the causative gene mutation, which helps define (usually correctable to 20/60). the inheritance pattern.

• OCA type 3 results from a mutation of the TRP- Treatment Options and Outlook 1 gene, which encodes proteins that have There are no treatments for albinism itself. COR- incompletely understood roles in the formation RECTIVE LENSES and methods to correct strabismus of pigment. or nystagmus, if present, can improve vision to Ocular albinism (OA) Ocular albinism results the extent possible. Many people who have from an X-linked mutation of an as-yet unidenti- albinism have functional vision, even if they have fied gene. People who have OA have normal or legal blindness, and can participate in most activi- minimally affected skin and hair pigmentation but ties that require basic vision though may not be lack pigment in the structures of the eye, resulting able to drive. in vision impairment. Albinism, particularly OCA type 1, may limit Other forms of albinism Other forms of outdoor activities in areas that receive intense albinism are less common or may be part of a sunlight. The sun presents a risk for sunburn and larger complex of symptoms. Among them are related damage as well as harm to the eyes. Photo- phobia nearly always accompanies albinism and • Chédiak-Higashi syndrome (CHS), a variation can make it difficult to remain in bright light, even of OCA in which there are also immune and wearing sunglasses, for any substantial length of neurologic dysfunctions time. People who have albinism should wear pro- tective clothing, sunglasses, hats, and high-SPF • Hermansky-Pudlak syndrome (HPS), a multi- sunscreen whenever they are outdoors. system disorder that involves PLATELET dysfunc- tion resulting in excessive bleeding, vision Risk Factors and Preventive Measures impairment, and inappropriate fat storage in The sole risk factor for albinism is genetic muta- tissues throughout the body as well as absence tion. Doctors recommend genetic testing and of pigmentation in the skin and hair counseling for families in which members have • Waardenburg’s syndrome, a complex of symp- albinism. Though there is no treatment for toms involving HEARING LOSS and partial albinism, early diagnosis helps minimize the albinism (often a lock of white hair in the front extent of vision impairment that may result from of the head with the rest of the hair normal nystagmus or strabismus. People who have color); people with this disorder may also have albinism also should undergo frequent screening pale blue eyes or different color in each eye for skin cancer, beginning in childhood. See also AMBLYOPIA; MELANOCYTE. Symptoms and Diagnostic Path The most obvious symptom of albinism, pale col- alopecia The clinical term for HAIR loss. There oration of the skin and hair, is apparent at birth. are numerous forms and causes of alopecia, which Light-colored eyes and vision problems such as may be localized or widespread, temporary or per- STRABISMUS (inability of the eyes to focus in uni- manent. Though alopecia is emotionally traumatic son), NYSTAGMUS (involuntary rapid eye move- for many people, it does not affect health in any ments), and PHOTOPHOBIA (extreme sensitivity to way though may reflect underlying health condi- alopecia 137 tions. Common forms of alopecia include the fol- hair growth to resume. Medical treatments that lowing: stimulate follicle activity can accelerate the return of hair in many such situations. • Androgenic alopecia, or male pattern hair loss, in which a man’s hairline recedes from the CONDITIONS ASSOCIATED WITH ALOPECIA temples and forehead and thins on the crown radiation exposure CHEMOTHERAPY in a characteristic pattern that may culminate TRICHOTILLOMANIA tinea capitis with a fringe of hair remaining along the sides PREGNANCY MENOPAUSE and back of the head. Hair loss is permanent. HYPOTHYROIDISM high FEVER Androgenic alopecia is hereditary and com- INFECTION or serious illness scars from wounds or BURNS monly begins in midlife, though may begin as excessive hair care and styling SUNBURN and sun exposure early as a man’s mid-20s. Researchers believe AUTOIMMUNE DISORDERS DISCOID LUPUS ERYTHEMATOSUS androgenic alopecia results from a combination hormonal changes (DLE) of genetic predisposition and naturally declin- SYSTEMIC LUPUS MALNUTRITION ing TESTOSTERONE levels. ERYTHEMATOSUS (SLE) hair coloring and styling • Female pattern alopecia, in which a woman’s stress products hair gradually thins on the top and sometimes FOLLICULITIS back of her head. Hair loss is permanent. Symptoms and Diagnostic Path Researchers believe female pattern alopecia Hair loss is the primary symptom of alopecia. The results from hormonal changes (loss of ESTRO- pattern and rate of hair loss help determine the GENS and testosterone) that occur following nature of the underlying cause. When alopecia is MENOPAUSE. male pattern or female pattern hair loss, the doc- •ALOPECIA AREATA, an autoimmune disorder in tor can make the diagnosis on the basis of appear- which the body’s IMMUNE RESPONSE attacks clus- ance. When the cause of hair loss is uncertain, the ters of hair follicles, temporarily impairing their doctor may biopsy several sites on the scalp, both ability to produce new cells. Alopecia areata with and without hair, for microscopic examina- may affect any part of the body and occasion- tion. A comprehensive health history and medical ally the entire body. Hair loss is temporary, examination are important to identify any poten- though may be long term. tial systemic or general health causes for hair loss. Preliminary findings determine what, if any, fur- • Toxic alopecia, which results from exposure to ther testing is necessary. substances that impair the ability of the hair follicles to generate new cells. The most com- Treatment Options and Outlook mon sources of such exposure are radiation Treatment first targets any underlying condition therapy and chemotherapy treatments for can- that may be responsible for hair loss. In many sit- cer. Other causes include vitamin A toxicity uations of alopecia related to other health condi- and medication side effects, such as from tions, hair growth will resume without medical retinoid preparations to treat acne. The extent intervention. People who are sensitive about their of hair loss depends on the toxic agent, ranging appearance during the period of temporary alope- from localized (such as with radiation therapy cia may choose to wear hairpieces, hair weaves, to the head) to nearly complete (such as with wigs, scarves, or hats until their hair returns. Topi- chemotherapy). Hair growth returns when the cal products to stimulate hair growth, such as toxic exposure ceases. minoxidil (Rogaine) and finasteride (Propecia), sometimes hasten the return of hair follicle func- Scarring, such as occurs as a result of BURNS, tion. Such products are often the first choice of wounds, and certain AUTOIMMUNE DISORDERS, treatment for male or female pattern hair loss as destroys the hair follicles so hair loss in such areas well as many forms of nonscarring alopecia. How- is permanent. Conditions and circumstances that ever, hair growth typically continues only for as damage but do not destroy the follicles often allow long as treatment continues. 138 The Integumentary System

people of any age and is more common in people Minoxidil and finasteride can cause who have other AUTOIMMUNE DISORDERS. serious BIRTH DEFECTS when they enter Researchers suspect an interaction between the system of a woman who is preg- genetic and environmental factors is responsible nant. Women of childbearing age gener- for alopecia areata, though they do not yet under- ally should not use or handle these stand the precise mechanisms. Alopecia areata products. does not affect health in any way other than hair growth; however, the cosmetic result (particularly Hair replacement methods surgically relocate scalp involvement) often distresses people who scalp SKIN with abundant, productive hair follicles have the condition. Treatments to stimulate folli- to areas of the scalp where there is hair loss. cle activity sometimes can restore normal hair pat- Though these methods cannot restore hair growth terns when hair loss is mild to moderate. Cosmetic to its previous patterns and thickness, they can solutions such as wigs or hairpieces may produce provide satisfactory results for many people. The more satisfactory results than medical interven- color and consistency of the hair influences the tions when the affected areas are extensive. success of hair replacement. As well, the scalp must contain adequate areas of productive hair THERAPIES FOR ALOPECIA AREATA follicles to serve as donor sites. site-specific cortisone injections oral CORTICOSTEROID Risk Factors and Preventive Measures topical minoxidil MEDICATIONS Risk factors for alopecia include AUTOIMMUNE DISOR- topical IMMUNOTHERAPY topical anthralin DERS, toxic exposures, stress, heredity, and aging. wigs and hairpieces Efforts to maintain healthy skin help support pro- ductive hair growth though cannot prevent most See also PSORIASIS. forms of alopecia. Treating any underlying condi- tion that causes alopecia often results in the angioma A noncancerous tumor formed of BLOOD return of hair. vessels (hemangioma) or LYMPH VESSELS (lymphan- See also FOLICULITIS; HIRSUTISM; LICHEN PLANUS; gioma). Angiomas visible on the SKIN are common SCAR; STRESS AND STRESS MANAGEMENT; TINEA INFEC- and may appear as circular, red growths (cherry TIONS. angiomas) or weblike networks of blood vessels just beneath the surface of the skin (spider angiomas). alopecia areata A form of HAIR loss (ALOPECIA) Angiomas generally remain small and seldom pre- that results from an autoimmune disorder in sent health complications. Because it contains such which the IMMUNE SYSTEM attacks clusters of hair a rich blood supply an angioma may bleed pro- follicles, halting hair growth. The clusters typically fusely when cut or in a location that receives fre- appear as circular patches of hairless SKIN, which quent irritation such as from clothing that rubs or are most noticeable when they occur on the scalp constricts it. The dermatologist may remove an though can occur anywhere on the body. Hair angioma that often bleeds or that the person finds growth within the affected follicles may remain cosmetically unacceptable. Common methods of interrupted for months to years; the timing and removal include electrical desiccation (applying a pattern of attacks seem to be random. Hair growth slight electrical current to the angioma) and liquid will eventually resume without treatment, though nitrogen (which freezes the angioma). Angiomas sometimes years after symptoms first begin. The occur more frequently in older adults (beyond age extent of hair loss varies widely among individu- 50), though can develop at any age. als, ranging from a few isolated patches to the See also ARTERIOVENOUS MALFORMATION (AVM); entire scalp or total body. Some people also expe- TELANGIECTASIS; VARICOSE VEINS. rience small pits, called stippling, in their finger- nails and toenails. Alopecia areata can affect athlete’s foot See TINEA INFECTIONS. B

baldness See ALOPECIA. tion. Multiple café au lait spots (six or more) can suggest NEUROFIBROMATOSIS, a genetic disorder, and bedsore See DECUBITUS ULCER. require further evaluation. Congenital dermal melanocytosis (Mongolian spot) often has the birthmark A discoloration on a newborn’s SKIN appearance of a large bruise (ECCHYMOSIS), some- present at, or that emerges within a few weeks of, times raising concerns about CHILD ABUSE among birth. Birthmarks are either vascular (composed of those who are not familiar with this birthmark. A BLOOD vessels and red in color) or pigment (patches health-care provider can quickly distinguish the of skin that differ in color from the surrounding mark and determine that it is not a bruise. skin). Though some birthmarks, especially large ones, may be permanent, many fade to become Any change in the size, color, or charac- faint or unnoticeable by about age 10 years. Most teristics of a birthmark, especially a birthmarks do not present any health problems, NEVUS (mole), requires prompt medical though large or obvious birthmarks often arouse evaluation to check for malignant concern for cosmetic reasons. Occasionally vascular melanoma or other SKIN CANCER. birthmarks arise in sites where they can interfere with vision (when near the EYE or on the eyelid), Treatment Options and Outlook BREATHING (when near the entrance to the NOSE), or Most birthmarks fade by ADOLESCENCE, making feeding (when on the lips). treatment unnecessary. The doctor may choose to surgically remove nevi (moles) that are large or in Symptoms and Diagnostic Path locations where they are subject to irritation from Most birthmarks are present at, or appear shortly clothing or movement, to prevent them from following, birth. Some vascular birthmarks may evolving to SKIN CANCER. Port wine stains (flat not appear for several months after birth. When hemangiomas) are often emotionally distressing this is the case, the birthmark appears suddenly when they occur on the face. The dermatologist and grows rapidly, then remains at a steady size. may use laser therapy to shrink and seal off the Many vascular birthmarks then disappear as the blood vessels causing the port wine stain, dimin- child grows older. The doctor can identify most ishing its prominence. Cover-up cosmetics are also birthmarks based on physical appearance. The an option. Children are particularly sensitive doctor may choose to conduct MAGNETIC RESONANCE about having obvious birthmarks and may need IMAGING (MRI) or COMPUTED TOMOGRAPHY (CT) SCAN emotional support. Birthmarks are very common, when there is a cavernous hemangioma because with some experts estimating that about a third of this kind of blood vessel tumor (noncancerous) infants are born with them. can occur within internal organs such as the LIVER or BRAIN and creates a risk for HEMORRHAGE (uncon- Risk Factors and Preventive Measures trolled bleeding), or the doctor may perform a Birthmarks appear to be random and common, biopsy (take a tissue sample to examine under a with as many as a third of newborns having at microscope) of lesions of questionable composi- least one. Because researchers do not know what 139 140 The Integumentary System

BIRTHMARKS Clinical Name Type Common Names Characteristics capillary hemangioma vascular strawberry red discolorations that resemble strawberries hemangioma most common on the face, back, chest, and back of the neck may be nonexistent at birth, then within a few weeks appear and rapidly grow generally fade by age 9 cavernous hemangioma vascular none purple or reddish blue cluster of blood vessels beneath, rather than on the surface of, the SKIN may be quite large, with a spongy consistency may exist within internal organs such as the LIVER, BRAIN, and BONE present at birth or appears within a few days of birth susceptible to possibly profuse bleeding with trauma may require surgical removal congenital dermal pigment Mongolian spot, common among infants with dark skin melanocytosis Mongolian blue spot dusky blue coloration, can cover a large area most often appears on the lower back or buttocks present at birth or appears within a few days of birth generally fades by age 12 congenital NEVUS; giant pigment mole cluster of pigmented cells congenital nevus may be flat or raised may have HAIR growing from it (called hairy nevus) increased risk for malignant melanoma when > 20 centimeters (giant congenital nevus) nevus flammeus vascular stork bite, salmon patch small, pink, irregular discolorations of the skin most common on the face and back of the neck may be nonexistent at birth, then within a few weeks appear and rapidly grow generally fade by age 4 nevus flammeus vascular port wine stain most often appears on the face persists into adulthood hyperpigmented MACULE pigment café au lait spot coloration similar to coffee with milk faint appearance at birth, becomes more prominent by age 3 More than five or six spots may suggest neurofibromatosis bulla 141 causes them to occur, there are no known meas- and purified solution of botulinum neurotoxin A ures for preventing them. Any changes in a birth- (Botox) or botulinum neurotoxin B (Myobloc). mark that has been stable in size and appearance Botulinum therapy became therapeutically warrant a doctor’s evaluation to determine acceptable in the United States in 1990 when the whether the changes signal skin CANCER. Early US National Institutes of Health (NIH) issued a detection and treatment are especially crucial for consensus statement outlining the clinical applica- malignant melanoma, in which a NEVUS becomes tions for its use (Clinical Use of Botulinum Toxin cancerous, as this cancer can be aggressive and [NIH Consensus Statement]. 1990. November lethal when untreated. Birthmarks themselves do 12–14; 8[8]:1–20). These uses include treatment not present any risk to overall health. for neuromuscular disorders such as DYSTONIA, BLE- See also ANGIOMA; GENETIC DISORDERS; LESION. PHAROSPASM, CEREBRAL PALSY, STRABISMUS, TORTICOL- LIS, MULTIPLE SCLEROSIS, and PARKINSON’S DISEASE, as blister A fluid-filled pocket that develops well as spasms that result from TRAUMATIC BRAIN between the layers of SKIN in response to friction INJURY (TBI) OR SPINAL CORD INJURY. or pressure. Blisters are most common on the feet An outgrowth of these applications was the dis- and hands though can develop nearly anywhere covery that botulinum therapy causes SKIN WRIN- on the body. Blisters often hurt. Their outer layer KLES to lessen or disappear. In 2002 the US Food of skin is vulnerable to tearing, which allows the and Drug Administration (FDA) approved botu- fluid to leak out. Though the blister may then feel linum therapy as a cosmetic treatment for fore- better because there is less pressure, the break in head wrinkles (frown lines). Cosmetic applications the skin’s surface gives BACTERIA access to the inner are becoming increasingly common, with many layers of tissue and establishes a risk of INFECTION. dermatologists using botulinum therapy to reduce An intact blister usually will heal within three wrinkles around the eyes and other areas of the to five days as the body reabsorbs the fluid and face and body. In 2004 the FDA approved botu- repairs the damaged skin. A ruptured blister is an linum therapy for HYPERHIDROSIS, a disorder of the open wound that requires appropriate WOUND SWEAT GLANDS that results in profuse sweating. The CARE, such as cleansing with mild soap and water effects of botulinum therapy last about four to six and possibly antibiotic ointment and a bandage. months. Risks are slight and may include localized The most effective treatment for blisters is preven- INFECTION and temporary weakness of the injected tion such as wearing gloves or thick socks and muscles. properly fitting shoes or boots. An area of the skin See also BACTERIA; BLEPHAROPLASTY; CHEMICAL that repeatedly forms a blister often develops a PEEL; RHYTIDOPLASTY. CALLUS, an accumulations of keratocytes, which increases the skin’s thickness and improves its bruise See ECCHYMOSIS. ability to withstand friction or pressure. See also BULLA; CORNS; DECUBITUS ULCER; KERATO- bulla A large (5 millimeters or greater) blister- CYTE. like formation, raised and fluid filled, that may hurt or itch. INFECTION, contact irritants, IMMUNE botulinum therapy Injections of botulinum neu- RESPONSE, and systemic health conditions may rotoxin to selectively paralyze MUSCLE fibers. The cause bullae. Bullous DERMATITIS may result from bacterial strain Clostridium botulinum produces sev- contact with plants such as poison ivy, oak, or eral forms of paralytic toxin, some of which can sumac. To determine the cause of bullous erup- cause serious or fatal poisoning (BOTULISM) when tions, the doctor may biopsy a bulla (remove a ingested. The toxin works by blocking the release small section for examination under the micro- of acetylcholine, a NEUROTRANSMITTER that facili- scope) or perform tests to look for immune pro- tates NERVE signals between muscle cells and the teins. Tense bullae form in the deeper layers and BRAIN. The blockade prevents the muscle cells from are less likely to rupture. Flaccid or loose bullae contracting. Botulinum therapy products currently form in the superficial layers of the skin and are available in the United States contain a weakened fragile, making them more likely to tear. 142 The Integumentary System

Treatment generally is twofold, targeting the bullous pemphigoid An autoimmune disorder underlying cause as well as aiming to relieve in which itchy bullae (blisterlike formations) symptoms such as itching and the bullous develop on the SKIN. Bullous pemphigoid is more swellings. Topical CORTICOSTEROID MEDICATIONS often common in people age 50 and older, and typically help the symptoms and sometimes the underlying occurs in those who are 70 or older. The bullae cause when it is an immune response or autoim- tend to concentrate in areas where there are skin mune disorder. ANTIBIOTIC MEDICATIONS, often both folds, such as the groin and the creases of the topical and oral, are necessary to treat bullae that elbows and knees. The skin around the bullae arise from bacterial infection or that become may be red and tender. The condition is self-limit- infected. Healed bullae may leave indentations or ing, which means it will improve on its own. scars, especially if they were infected. However, the bullae are very uncomfortable; med- ical intervention targets relieving their discomfort and hastening the condition’s regression and reso- HEALTH CONDITIONS ASSOCIATED WITH SKIN BULLAE lution. The doctor will likely biopsy several of the adverse DRUG reaction BULLOUS PEMPHIGOID bullae to obtain a definitive diagnosis. Treatment contact dermatitis DERMATITIS herpetiformis with topical and oral CORTICOSTEROID MEDICATIONS DIABETES EMPHYSEMA reduces the IMMUNE RESPONSE and improves symp- hereditary AUTOIMMUNE IMPETIGO toms. The B vitamin niacinamide also provides DISORDERS STAPHYLOCOCCAL SCALDED SKIN additional relief for some people. The bullae usu- PEMPHIGUS SYNDROME ally heal without scarring. In most people the bul- TOXIC EPIDERMAL NECROLYSIS warfarin reaction lae heal within a few months, though occasionally the course of disease may run several years. See also BLISTER; CALLUS; CELLULITIS; ICHTHYOSIS; See also AUTOIMMUNE DISORDERS; BULLA; PEMPHI- PAPULE; URTICARIA; VESICLE. GUS. C callus An accumulation of keratocytes that form the skin. Carbuncles tend to recur. People who a thickened area of SKIN in response to repeated have DIABETES are more likely to develop carbun- friction or pressure, typically at the site of cles because the diabetes damages the delicate repeated blistering. A callus may be a different blood vessels responsible for peripheral circula- color than the surrounding skin, often grayish or tion, preventing the bloodstream from carrying yellowish. Calluses are most likely to develop on bacteria-fighting blood cells to the site of the the palms, fingers, fingertips, heels, and balls of infection. People who have impaired immune the feet. Most calluses are not painful and help function are also at increased risk. Untreated car- protect the skin from blisters and other friction- buncles can result in scars after healing or can related injuries. Calluses do not require medical progress to systemic infection (SEPTICEMIA). intervention unless they cause PAIN. Applying aloe See also CELLULITIS; FURUNCLE; SCAR. or a moisturizing skin lotion and gently rubbing the callus with a pumice stone while in the cellulitis INFLAMMATION of the inner layers of the shower or bath are measures that can contain the SKIN and the underlying connective tissues, usually size and thickness of calluses. Wearing gloves to the result of a bacterial INFECTION. People who protect the hands and well-fitting socks to protect have PERIPHERAL VASCULAR DISEASE (PVD), DIABETES, the feet can help prevent a BLISTER and resulting or other health conditions that impair BLOOD circu- callus from forming. lation have increased risk for cellulitis. Cellulitis See also CORNS; KERATOCYTE. develops when a break in the skin, such as a cut or an insect bite or sting, allows BACTERIA normally carbuncle Clusters of infected HAIR follicles present on the surface of the skin to enter and (furuncles) that often form an ABSCESS. Carbuncles establish infection. The offending breach often are most common on the back of the neck and comes from something so small as to appear shoulders, though may form at other locations insignificant until infection sets in. Staphylococcus is where furuncles tend to occur. Carbuncles are the most common type of bacteria responsible for painful and often result in FEVER and general cellulitis; Streptococcus is sometimes responsible. malaise (not feeling well). The INFECTION is deep Bacteria also may enter via contamination of a within the layers of SKIN and generally requires penetrating object such as a splinter. Cellulitis treatment with an oral ANTIBIOTIC MEDICATION. The requires prompt treatment with ANTIBIOTIC MEDICA- doctor may choose to lance (open with a sterile TIONS to minimize tissue damage and prevent the incision) the carbuncle to allow the collected pus spread of infection. to drain. Applying warm, moist compresses four to six times a day helps open the follicles and allow Symptoms and Diagnostic Path continued drainage as HEALING takes place. Swelling, redness, and PAIN or itching are the key Though poor PERSONAL HYGIENE can contribute to symptoms of cellulitis. The edges of the infection the development of furuncles and carbuncles, the are diffuse, often making it difficult to establish a primary cause of these painful sores is BACTERIA, border between healthy and infected tissue. The typically Staphylococcus, that normally resides on doctor diagnoses cellulitis primarily on its appear- 143 144 The Integumentary System ance and symptoms. Usually no blood or other the face, to improve the appearance of WRINKLES, laboratory tests are necessary, unless the doctor scars, ACNE, widespread ACTINIC KERATOSIS, LENTIG- suspects systemic infection (SEPTICEMIA) or ques- INES (brown spots or liver spots), dyschromia (pig- tions the causative strain of bacteria. mentary irregularities), and other blemishes. The dermatologist applies a chemical solution, either Treatment Options and Outlook an acid or phenol, to the selected areas of skin. For moderate, localized cellulitis the typical treat- The solution BURNS the skin, causing one layer or ment is a course of oral antibiotics with close fol- more of skin to slough off as HEALING takes place. low-up to make sure the selected antibiotic is The new skin that replaces the old skin is effective against the infection and the cellulitis is smoother, tighter, and lighter in color. improving. Warm, moist compresses over the infected area help draw blood the area, improving Light Peel: AHA Solutions the body’s ability to fight the infection. When cel- The lightest chemical peel is an alphahydroxyl lulitis affects a large area or multiple areas or acid (AHA) solution such as lactic acid or glycolic worsens after antibiotic therapy begins, the doctor acid. It removes the top layer of skin (epidermis) may place the person in the hospital for intra- and is appropriate for treating minor skin irregu- venous (IV) antibiotic therapy and continuous larities. The dermatologist puts the mild acid on observation. Cellulitis in a person who is IMMUNO- selected skin sites in a series of applications or may COMPROMISED or otherwise debilitated requires mix the solution into a cream or wash for weekly especially aggressive treatment. Untreated or home use until the peel produces the desired undertreated cellulitis can have serious conse- results. An AHA chemical peel causes mild irrita- quences such as septicemia or GANGRENE (death of tion and discomfort that resolves as the skin heals. the tissue). Cellulitis also presents particular risk It generally takes six to eight weeks to see results to people who have impaired circulation for any with an AHA peel. An AHA peel requires frequent reason. With timely and appropriate treatment, retreatment to maintain the effect. most people recover fully. Moderate Peel: TCA Solution Risk Factors and Preventive Measures A moderate chemical peel uses a stronger acid Wounds that break the skin breach the body’s first solution, trichloroacetic acid (TCA), to remove the line of defense against infection. Prompt cleansing top and underlying layers of skin (epidermis and of the entry site with antibacterial soap and warm upper dermis). The dermatologist applies the TCA water, followed with topical antibiotic ointment solution in one to three sessions spread over sev- and a bandage, helps reduce the amount of bacte- eral months. A TCA chemical peel is appropriate ria that enter the skin and limit their ability to for treating fine facial wrinkles and pigmentary cause infection. Early signs of infection, such as irregularities. The treated area first forms a frothy swelling, redness, or drainage, require prompt coating and then scabs or crusts. The treated area medical intervention that may include oral antibi- also becomes swollen and may be uncomfortable otic medications. People who have diabetes, PVD, enough to require mild PAIN relief medication for and other conditions that restrict peripheral circu- several days. Full healing takes about two weeks. lation should develop the practice of regularly The effects of a TCA peel generally last a year or examining the feet, lower legs, fingers, hands, and longer, though many people need more than one lower arms for minor wounds that could become treatment to achieve the desired results. problematic as a measure for early identification and intervention to prevent cellulitis. Deep Peel: Phenol Solution See also DECUBITUS ULCER; INSECT BITES AND STINGS; A deep chemical peel extends through the dermis, NECROTIZING FASCIITIS. the middle layer of the skin, to the hypodermis (innermost layer of the skin). It produces some- chemical peel A cosmetic procedure to smooth what of a burn effect that causes complete loss and tighten the surface of the SKIN, typically on and replacement of the skin. The dermatologist corns 145 uses a phenol solution to achieve this result, See also AGING, INTEGUMENTARY CHANGES THAT which is appropriate for treating moderate facial OCCUR WITH; BLEPHAROPLASTY; BOTULINUM THERAPY; blemishes, acne scars, sun damage, actinic kerato- COLD SORE; DERMABRASION; LASER SKIN RESURFACING; sis, and most wrinkles. The application procedure PLASTIC SURGERY; RHINOPLASTY; RHYTIDOPLASTY; SCAR; takes about an hour, before which the dermatolo- VITILIGO. gist generally administers a sedating medication. Following the phenol application the dermatolo- chloasma A pattern of hyperpigmentation, often gist coats the treated area with petroleum jelly or temporary, that typically affects the face. other protective covering to reduce discomfort. Chloasma, also called melasma, develops with ele- The treated area is immediately raw and exposed, vated blood levels of ESTROGENS, such as occurs with scab formation in about 48 hours. during PREGNANCY, with some oral contraceptive Swelling and discomfort are significant for a (birth control pill) formulations, and in chronic week or two after a phenol peel, and most people LIVER disease. When the cause is hormonal, the cannot participate in any regular activities during hyperpigmentation fades when HORMONE levels this time and may require assistance if the return to normal. Chloasma may also develop in swelling causes their eyes to close. Proper care men or women who have liver conditions such as during healing is essential, and typically requires a CIRRHOSIS or HEPATITIS. The melanocytes (melanin- regimen of ANTIBIOTIC MEDICATIONS and ointments producing cells) in the affected areas of skin over- to help keep the healing tissue moist and supple. produce melanin, the pigment that gives SKIN its The treated skin remains red and shiny for up to color. The hyperpigmented areas have clearly three months. Full healing takes four to six defined borders and often appear in symmetry, months, though most people can return to most resulting in a masklike appearance. normal activities in about three weeks. The doctor diagnoses chloasma on the basis of The effects of a phenol peel typically last sev- its appearance and correlation with factors such as eral years. The skin commonly loses its ability to pregnancy or liver disease. Topical solutions such produce melanin, however, making sunscreen and as hydroquinone and tretinoin (Retin-A) help fade protective clothing such as a broad-brimmed hat the chloasma in some people, though pregnant essential to prevent sun damage and SUNBURN women should not use these treatments. Both when outdoors. Most dermatologists recommend medications have potentially serious side effects applying sunscreen daily, after healing, as a rou- and are for short-term use only (eight weeks or tine preventive measure. The loss of melanin also less). As sun exposure intensifies melanin produc- results in a permanently lighter pigmentation of tion, dermatologists recommend wearing sun- the treated area. Because of this, people who have screen (sun protection factor [SPF] 30 or greater) dark skin should not undergo phenol peels. and shading exposed areas of skin from the sun as much as possible. Chloasma is primarily cosmetic Risks and Complications and does not present a threat to health other than Though chemical peels can produce smoother, that of any underlying condition. Most chloasma more youthful looking skin, they do so by first resolves on its own when the underlying cause damaging the skin so it must repair itself. The risks health condition changes. of chemical peels include infection, scarring, and See also MELANOCYTE; ROSACEA; SUN PROTECTION. irregularities in pigmentation after healing. Some people have adverse reactions to the chemical corns Growths of thickened SKIN on the tops and solutions. People who are prone to cold sores or sides of the toes. Corns result from accumulations FEVER blisters are likely to develop them during the of keratocytes that develop in response to healing phase; many dermatologists prescribe repeated pressure, typically from shoes that are ANTIVIRAL MEDICATIONS to prevent these viral out- too tight, and are the body’s effort to protect the breaks from occurring. Phenol may exacerbate skin and underlying tissues. A corn has a hard ARRHYTHMIA (irregularity of the heartbeat) in peo- inner core with a surrounding ring of thickened ple who have arrhythmia disorders. though soft skin. Corns often hurt because they 146 The Integumentary System compress and irritate the nerves in the underlying treatment from a podiatrist (foot care specialist), tissues, and continue to grow as long as the pres- who may anesthetize the corn and use a scalpel to sure against the toes continues. shave away some of the overgrown skin. The most effective treatment for corns is pre- See also BLISTER; CALLUS; KERATOCYTE. vention by wearing low-heeled shoes that fit properly. A shoe with a heel more than half an cradle cap A form of DERMATITIS, also called inch higher than the rest of the shoe’s sole causes infantile seborrheic dermatitis, in which the seba- the foot to slide forward in the shoe, squeezing ceous structures of the SKIN oversecrete oils. The the toes and subjecting them to pressure from the excessive sebaceous secretions trap loose, dead sides and top. Once a corn develops, treatment skin cells, forming crusts or scales. Cradle cap, as focuses on softening the skin and relieving pres- the name implies, affects young infants. Doctors sure against the area. Self-care measures include believe the condition results from the surge of maternal hormones that infuse the infant’s blood- • wearing flat-soled, wide-toe-box shoes stream shortly before birth, stimulating the seba- • using corn pads, donut-shaped felt or foam ceous glands. Because the primary location of rings, to relieve pressure against the sensitive body hair on the infant is on the head, the crusts inner core of the corn while wearing shoes are most common on the scalp. They also may • gently rubbing the corn with a pumice stone form around the eyebrows. Gentle shampooing while in the bath or shower helps keep the scalp clean. The caregiver can rub • applying aloe vera gel or moisturizing lotion to baby oil into crusted areas to soften crusts before the area shampooing to help remove them. Cradle cap generally clears up within a few months and does Large corns or corns that fail to respond to self- not occur after about age 12 months. care measures require evaluation and possible See also DANDRUFF; HORMONE; SEBACEOUS GLAND. D dandruff A common symptom in which the are the key symptoms of dandruff. The scalp sebaceous glands on the scalp increase their activ- sometimes itches. The diagnostic path includes ity, accelerating the SKIN’s normal, continuous examination of the skin over all of the body to dis- process of replacing itself. Consequently the skin tinguish simple dry skin, which can cause flaking, on the scalp sheds cells at an accelerated rate, from dandruff, as well as to rule out other derma- causing visible patches of collected cells that accu- tologic conditions. The dermatologist may conduct mulate on the scalp’s surface (most commonly on further testing, such as skin scraping or biopsy, the top of the head) or flaking that may appear in when there is reason to suspect a condition other the HAIR and on the clothing. BACTERIA and yeast than one that commonly causes dandruff. (FUNGUS) normally present on the skin can irritate and inflame the sebaceous structures of the scalp, Treatment Options and Outlook a condition doctors call seborrheic DERMATITIS. Der- Mild dandruff—light, barely noticeable flaking matologists often diagnose seborrheic dermatitis as that remains along the scalp or in the hair—often the underlying cause of dandruff. PSORIASIS and clears with daily shampooing and thorough rins- tinea capitis are also common causes. ing. Moderate dandruff—obvious flakes in the hair and on the shoulders—may require sham- Flaky, patchy SKIN on the eyebrows, pooing with products that contain ingredients to around the eyelashes, and other sites on curtail the growth of keratinocytes, the cells that the body beyond the scalp may signal a make up most of the skin’s outer layer (epider- dermatologic condition other than dan- mis). Such shampoos typically contain selenium druff and requires a doctor’s evaluation. sulfide, zinc pyrithione, or coal-tar extracts. Which products are more effective seems a matter Though numerous factors may contribute to of personal preference. dandruff, dermatologists believe a convergence of Severe dandruff—flakes are always present in genetics, age, hormones, and environmental con- the hair and on the clothing—may require pre- ditions accounts for most cases, as these are the scription shampoos or lotions that often contain factors that generally influence sebaceous activity. stronger concentrations of the active ingredients Dandruff flare-ups are common during PUBERTY, that over-the-counter products contain. For very PREGNANCY, and MENOPAUSE, periods of life charac- severe dandruff with INFLAMMATION of the skin and terized by hormonal surges. Dandruff also sebaceous structures, the doctor may prescribe becomes more common during times of physical corticosteroid drops or lotion in combination with or emotional stress, and when external environ- other remedies. Stubborn dandruff may require a mental conditions are cold and dry such as is typi- regimen of products to bring it under control, cal in the winter. though most people can then keep dandruff in check with a few core products. Symptoms and Diagnostic Path Recent research suggests that many people who Light-colored patches on the scalp that flake when have seborrheic dermatitis, the most common scratched or flakes in the hair and on the clothing cause of persistent dandruff, may have a skin 147 148 The Integumentary System environment that encourages a normally present See also CORTICOSTEROID MEDICATIONS; CRADLE CAP; fungus, Malassezia (also called Pityrosporum), to HORMONE; KERATINOCYTE; KERATOSIS PILARIS; SEBA- flourish in abundance. Malassezia subsists on CEOUS GLAND; STRESS AND STRESS MANAGEMENT. sebum, an oil substance the sebaceous glands secrete. An overgrowth of Malassezia depletes the decubitus ulcer An erosion in the SKIN that sebum supply, causing the sebaceous glands to results from the pressure of remaining in one posi- increase sebum production. This in turn acceler- tion for an extended period of time, commonly ates cell growth, generating dandruff. Shampoos called a bedsore or pressure sore. The extended and lotions containing an antifungal medication pressure deprives the tissue of blood circulation, such as ketoconazole reduces the scalp’s Malassezia allowing cells to die and the tissue to break down. population, returning cell turnover to normal. Tissues over areas where the bones are near the skin are most vulnerable, such as the hips, ankles, PRODUCTS TO CONTROL DANDRUFF heels, elbows, shoulders, base of the spine, and coal-tar extracts glycolic acid back of the head. Decubitus ulcers are a specific ketoconazole and other salicylic acid risk for people who have debilitating conditions or antifungal shampoos tea tree oil injuries that limit their mobility, particularly elder- selenium sulfide topical corticosteroids ly individuals in extended-care facilities. MALNU- zinc pyrithione TRITION and age-related changes to the skin result in fragility that makes the skin more susceptible to Risk Factors and Preventive Measures damage. Frequent or heavy use of hair products such as Often, measures such as frequent changes of hairsprays and styling gels can further clog the position and soft surfaces to shelter the skin at sebaceous structures. Stress, hormones, and the contact points can prevent decubitus ulcers. environment can precipitate or exacerbate dan- Within contemporary quality of care standards druff. Dandruff, or the skin conditions that estab- and guidelines in health care, decubitus ulcers lish dandruff such as seborrheic dermatitis, are raise questions as to whether providers and facili- more common in people who have PARKINSON’S ties are delivering appropriate care. Undetected or DISEASE, though the reason for this remains untreated decubitus ulcers can result in significant unknown. People who are prone to dandruff that tissue loss and threaten overall health. Once worsens seasonally often can minimize the sever- established, a decubitus ulcer requires aggressive ity of their symptoms by beginning therapeutic medical intervention to limit permanent tissue efforts before flaking becomes a problem. damage and restore healthy skin.

CLINICAL STAGING OF DECUBITUS ULCERS Clinical Stage Presentation Tissue Penetration stage 1 nonblanching red area superficial layers of skin (epidermis, first layer of dermis) stage 2 BLISTER or open sore full skin (epidermis and full thickness of dermis) to the underlying FASCIA stage 3 craterlike sore that oozes or bleeds; through the skin and fascia, into the supportive connective and damaged or necrotic (dead) SKIN; fatty tissue damage to underlying tissues stage 4 deep ulcer that bleeds; extensive skin through the skin, fascia, and underlying structures into adjacent and tissue destruction and necrosis MUSCLE, TENDON, and LIGAMENT, and JOINT dermatitis 149

Symptoms and Diagnostic Path • active movement at least four times a day The symptoms of decubitus ulcer depend on its when possible and passive range of motion stage of development. Health-care providers clas- exercises when active movement is not possible sify decubitus ulcers on a scale of 1 to 4, with • frequent (at least daily) inspection of areas vul- stage 1 being the slightest level of damage and nerable to pressure stage 4, the most significant. PAIN is not an effec- tive measure of a decubitus ulcer’s severity as the • diligent skin hygiene, including daily cleansing damage to the skin and underlying tissues may and complete drying destroy NERVE endings. Doctors diagnose a decubi- tus ulcer on the basis of its appearance. Prompt intervention at the earliest signs of a decubitus ulcer can prevent extensive or perma- Treatment Options and Outlook nent tissue damage. The first and most urgent action in treating decu- See also AGING, INTEGUMENTARY CHANGES THAT bitus ulcers is to relieve all pressure on the area. OCCUR WITH; CELLULITIS; EPIDERMOLYSIS BULLOSA; GAN- This may include using pillows, cushions, pads, GRENE; SCAR; SPINAL CORD INJURY; TRAUMATIC BRAIN and other items to support the body in positions INJURY (TBI). that do not put pressure on or near the ulcer. Additional treatment may include regularly dermabrasion A mechanical method for cleansing the ulcer to prevent INFECTION, or ANTIBI- smoothing roughened or scarred SKIN. The der- OTIC MEDICATIONS to treat infection that already mabrader is a motorized burrlike device that exists. Deep ulcers (stage 3 and especially stage 4) “sands” away the layers of skin to achieve the often require surgical débridement (removing desired result. Dermabrasion is appropriate for dead and damaged tissue under anesthetic). treating skin blemishes such as ACNE scarring or Recovery depends on the stage of the ulcer and sun damage. The dermatologist administers a the general health condition of the person. With sedative and a local anesthetic before the proce- early and aggressive intervention, recovery can be dure. After the procedure the skin is raw and ten- complete with minimal permanent tissue damage. der. There is usually significant swelling and Stage 2 and stage 3 ulcers generally heal with moderate discomfort that requires PAIN relief med- some loss of tissue and scarring. Stage 4 ulcers are ication. The skin scabs in about 24 to 36 hours. As extensive wounds that may require multiple HEALING progresses, the scabs fall off, with the new débridements and long-term treatment by a skin pink and shiny beneath. Total healing is com- WOUND CARE specialist. When debilitation is long- plete in five to six months, though most people term or permanent, the risk for recurring decubi- can return to their regular activities in about three tus ulcers is high. weeks. Risks and complications of dermabrasion include bleeding, INFECTION, scarring, and occasion- Risk Factors and Preventive Measures ally KELOID (overgrown SCAR) formation. Proper People whose health conditions limit their ability postprocedure care is important to encourage to move parts of their bodies or confine them to appropriate healing. wheelchairs or bed have very high risk for decubi- See also BOTULINUM THERAPY; CHEMICAL PEEL; LASER tus ulcers. Preventive measures include SKIN RESURFACING; PLASTIC SURGERY. • position changes every two hours when in bed and every 15 minutes when sitting in a chair or dermatitis INFLAMMATION, redness (erythema), wheelchair and itching of the SKIN. Dermatitis has many causes and manifests in numerous and varied pre- • air mattress with alternating compartments or sentations, some of which may reflect conditions air flotation mattress such as viral INFECTION, AUTOIMMUNE DISORDERS, and • eggshell mattress or seat cushion certain kinds of CANCER. Dermatitis may be acute • sheepskin pads over bony protuberances such (come on suddenly) or chronic (persist or recur as the heels and elbows over an extended period of time). 150 The Integumentary System

Atopic dermatitis A chronic condition also Contact dermatitis Numerous environmental called eczema, atopic dermatitis typically first substances, from plant resins (poison ivy) to met- appears in infancy or early childhood and often als (nickel, stainless steel) to bath soaps and laun- persists, in periods of exacerbation and REMISSION, dry detergents, can irritate and inflame the skin. throughout life. Symptoms include areas of red, Contact dermatitis may represent an allergic cracked, weepy (oozing) sorelike eruptions that response in which the IMMUNE SYSTEM, particularly eventually crust, scale, and thicken. Itching is the Langerhans cells located in the dermis, overre- intense. The most frequent areas of involvement acts to a substance. Allergic contact dermatitis are the surfaces on the inner (antecubital) surface generally appears within 24 hours of contact, of the elbows and the back (popliteal) surface of while weeks or even months of exposure to irri- the knees, though atopic dermatitis can affect any tants may take place before causing contact der- part of the body. Atopic dermatitis seems to have a matitis. The location of the first point of outbreak hereditary component, as it runs in families, and is often helps narrow the field for identifying the more common in people who have hypersensitiv- cause. ity conditions such as ALLERGIC RHINITIS. Treatment is twofold: removing the offending irritant or ALLERGEN, and treating the symptoms. People who have, or who have ever Oral antihistamine medications and topical corti- had, atopic dermatitis should not costeroids typically reduce itching and inflamma- receive vaccination against SMALLPOX tion. It may take up to three months for all that uses the vaccinia virus (the vaccine symptoms of contact dermatitis to resolve. Contact administered by health-care providers dermatitis can be a matter of OCCUPATIONAL HEALTH in the United States). This vaccine can AND SAFETY when the offending substance is neces- cause a particularly serious eruption of sary in the workplace. People who work with atopic dermatitis. glues, paints, metals, plastics, latex rubber, and numerous industrial chemicals commonly develop Treatments for atopic dermatitis outbreaks contact dermatitis. include topical skin lubricants, such as ointments Exfoliative dermatitis An uncommon but seri- and lotions that help the skin retain moisture, and ous form of dermatitis in which the epidermis topical CORTICOSTEROID MEDICATIONS. The dermatolo- (outer layer of the skin) becomes inflamed and gist may prescribe a course of oral corticosteroid forms scales that peel away, exfoliative dermatitis medication (such as prednisone) for severe or nearly always indicates systemic disease, frequently resistant symptoms. Oral ANTIHISTAMINE MEDICATIONS a cancer such as LEUKEMIA, cutaneous T-cell lym- may help control itching. Scratching excoriates phoma (CTCC), or LYMPHOMA. Exfoliative dermatitis the lesions, setting the stage for bacterial infection, may be the earliest sign of PROSTATE CANCER, THYROID which then requires ANTIBIOTIC MEDICATIONS. CANCER, and COLORECTAL CANCER. It also develops in Atopic dermatitis outbreaks vary in severity and people who have AIDS, and may occur as an length. Atopic dermatitis abates in some children as ADVERSE REACTION to numerous medications. they reach ADOLESCENCE or early adulthood, though Exfoliative dermatitis begins with patches of dermatologists believe the condition goes into an skin (lesions) that turn red and itch. Within two extended state of remission rather than disappears. weeks the lesions spread to cover nearly the entire In some adults, the only indications that atopic der- surface of the skin except the soles of the feet, matitis persists are fissures and cracks in the skin on palms of the hands, and face (though usually the palms of the hands and the soles of the feet, spare the mucous membranes). The scaling and which may appear to be exceedingly dry skin rather dilation of blood vessels that follow significantly than dermatitis. Coating the palms and soles with impairs all dermal functions from IMMUNE RESPONSE petroleum jelly at bedtime, protecting the coating to thermal regulation (heat loss). Fluid oozes con- with mittens and socks, often helps heal the fis- tinually from the exposed dermis and the BLOOD sures. About 10 percent of the American popula- vessels are dilated, causing excessive cooling that tion has atopic dermatitis. easily becomes HYPOTHERMIA. Damage to the pro- dermatitis 151 tective epidermis exposes the inner layers of skin not fully understand this correlation. Treatments and tissues to infection. for dandruff are often effective for seborrheic der- Treatment aims to restore skin integrity and matitis, and emphasize reducing sebum produc- function as well as to remedy any underlying dis- tion and accumulation. order. Symptomatic treatment typically includes Stasis dermatitis Restricted or damaged periph- oral antihistamines to control itching, topical cor- eral blood circulation allows fluid to collect ticosteroids to reduce inflammation, and warm between the layers of the skin, causing inflamma- baths. Prolonged or chronic exfoliative dermatitis tion and itching characteristic of dermatitis. The may require IMMUNOSUPPRESSIVE THERAPY such as skin typically becomes discolored, turning reddish psoralen plus ultraviolet-A (PUVA) therapy or brown, and scaly as the condition persists. People methotrexate. The success of treatment depends who have DIABETES, VARICOSE VEINS, PERIPHERAL VAS- on identifying and treating the underlying cause. CULAR DISEASE (PVD), or INTERMITTENT CLAUDICATION Idiopathic exfoliative dermatitis tends to recur, have increased risk for stasis dermatitis, as do peo- with periods of exacerbation alternating with peri- ple who have restricted mobility or are bedridden. ods of remission. The impaired circulation limits the skin’s ability to Nummular dermatitis Circular lesions about the resist or fight infection, and can allow the skin to size of coins that crust and weep are the distinctive break down into ulcerations that require aggres- hallmark of nummular dermatitis. Researchers do sive medical intervention. Wearing support hose, not know what causes the lesions to take such a elevating the legs when sitting or lying down, and precise form. Sometimes mistaken for tinea cor- walking are measures that help reduce fluid accu- poris (ringworm) at the onset of an outbreak, the mulations (edema). lesions begin as red, raised circles that quickly progress. Usually the lesions remain confined to Symptoms and Diagnostic Path small areas, and typically recur in the same loca- Though each type of dermatitis has unique symp- tions. Outbreaks can cause significant itching. As toms, all types share certain symptoms in com- with other forms of dermatitis, antihistamines and mon. These include lesions that: topical corticosteroids help control symptoms. Severe or persistent symptoms may require a • are erythematous and edematous (reddened course of oral or intramuscular corticosteroids. and swollen) Seborrheic dermatitis A common cause of DAN- • crust, weep, scale, and SCAR DRUFF, seborrheic dermatitis affects the sebaceous • itch intensely structures primarily of the head and face, notably • recur on the scalp, behind the ears, around the eyebrows, and in the beard area on men’s faces. Seborrheic The dermatologist often can make the diagnosis dermatitis may also develop on other parts of the based on the appearance, characteristics, and loca- body that have numerous sebaceous structures, tion of the lesions as well as the individual’s age such as the chest and axilla (underarms), and typi- and family health history. When the diagnosis is cally occurs in a symmetrical pattern. Inflammation questionable, the dermatologist may biopsy sev- stimulates the sebaceous glands to increase sebum eral lesions for further examination under the production, which in turn accelerates the turnover microscope. Tests for immune response also may rate of dermal and epidermal cells that plug the be helpful for confirming a diagnosis. sebaceous ducts and HAIR follicles. Key symptoms of seborrheic dermatitis include oily patches of skin Treatment Options and Outlook that crust, scale, and flake. Antihistamine and corticosteroid medications are Most seborrheic dermatitis is idiopathic (occurs the mainstay of pharmacological therapy for without identifiable cause) and is more common nearly all forms of dermatitis. Secondary bacterial in people between the ages of 20 and 40. Sebor- infections require treatment with antibiotic med- rheic dermatitis that occurs later in life may be a ications. Most dermatitis is, or becomes, chronic. sign of PARKINSON’S DISEASE, though researchers do Treatment approaches strive to minimize the fre- 152 The Integumentary System quency and severity of outbreaks. Though der- contact with the SKIN. The skin typically appears matitis is seldom life-threatening, it can signifi- chapped and raw. The involved area is painful and cantly interfere with QUALITY OF LIFE. Researchers may crack and bleed. Diaper rash that lasts longer continue to explore the causes of dermatitis, look- than three days often reflects an INFECTION of the ing for ways to suppress symptoms. skin, commonly FUNGUS (CANDIDIASIS). Untreated, persistent diaper rash may develop macerations Risk Factors and Preventive Measures that can result in deep ulcerations and CELLULITIS, The key risk factors for dermatitis are family his- requiring medical treatment. Mild to moderate tory and existing allergies. Preventive measures diaper rash is very common in children who are focus on minimizing outbreaks and symptoms. not yet toilet trained, with nearly all children Self-care approaches include experiencing at least one episode. Diaper rash often accompanies DIARRHEA. Diaper rash occurs • short, warm (not hot) baths or showers equally among infants who wear cloth diapers and • mild, detergent-free soaps who wear disposable diapers. • lubricating skin lotions, creams, and oils Home treatment successfully eliminates most diaper rash. Methods include • nonrestrictive clothing that allows moisture to evaporate • frequent diaper changes • restricted sun exposure • cleansing the skin with gentle soap and warm • resisting scratching water with each diaper change

See also ICHTHYOSIS; IMPETIGO; KERATOSIS PILARIS; • application of a moisture barrier cream or dia- LESION; LICHEN PLANUS; LICHEN SIMPLEX CHRONICUS; per rash product with each diaper change PSORIASIS; RASH; STAPHYLOCOCCAL SCALDED SKIN SYN- DROME; TINEA INFECTIONS; TOXIC EPIDERMAL NECROLYSIS; A doctor should evaluate diaper rash that per- URTICARIA. sists longer than a few days without improvement after home treatment measures. dermatofibroma A noncancerous (benign) See also DERMATITIS; FECAL INCONTINENCE; URINARY tumor that develops in the connective tissue INCONTINENCE. beneath the SKIN, most commonly on the legs and occasionally on the arms. Dermatofibromas are discoid lupus erythematosus (DLE) A chronic firm, round, and may differ in color from the sur- autoimmune disorder, also called cutaneous lupus rounding skin. Most dermatofibromas cause no erythematosus, in which roughly circular, red- symptoms (other than cosmetic) and require no dened patches (erythematous lesions) form on the medical intervention unless they become tender SKIN. The lesions are most common on the face, or irritated. The dermatologist may opt to remove back of the neck, scalp, inner lips and mouth, and or scrape down a dermatofibroma in a location outer portions of the auditory (EAR) canals. The where it receives repeated trauma such as from INFLAMMATION involves the epidermis, dermis, and shaving or rubbing against clothing. Dermatofi- HAIR follicles. When the lesions heal they leave bromas are common in adults. permanent scarring, lightened pigmentation, and See also LIPOMA. loss of hair (ALOPECIA) in their wake. Outbreaks may range from localized and sporadic to general- diaper rash An irritation of the genitals and but- ized and persistent. Cigarette smoking, heat, tocks in an infant or young child who wears dia- and exposure to sunlight precipitate or exacer- pers. Diaper RASH may also affect adults who wear bate outbreaks in many people who have DLE. adult diapers or other incontinence products. Most About 5 percent of people who have DLE subse- diaper rash begins as a reaction to the chemicals in quently develop SYSTEMIC LUPUS ERYTHEMATOSUS urine or feces, notably ammonia, that comes into (SLE), a generalized autoimmune disorder in dry skin 153 which lesions can attack internal structures as well MEDICATIONS TO TREAT DLE as the skin. Anti-Acne (Retinoids) isotretinoin acitretin Symptoms and Diagnostic Path etretinate tazarotene The characteristic appearance of the skin lesions is Antimalarials a clear diagnostic marker for DLE. Because the hydroxychloroquine chloroquine same skin lesions can be an early indication of Corticosteroids SLE, the diagnostic path includes biopsy of repre- triamcinolone hydrocortisone sentative lesions as well as BLOOD tests to assess betamethasone diflorasone ANTIBODY status. People whose DLE lesions are pri- marily above the neck usually have isolated DLE. flumethasone mometasone People who have DLE lesions both above and desoximetasone halcinonide below the neck have increased risk for SLE. fluocinonide amcinonide Immunomodulators Treatment Options and Outlook Interferon thalidomide The primary treatment approach for DLE is topical azathioprine mycophenolate or injected CORTICOSTEROID MEDICATIONS. In the early methotrexate dapsone stages of the condition, topical corticosteroids often limit the lesion’s progression. As the condi- Risk Factors and Preventive Measures tion becomes established, the lesions may not Researchers do not know for certain what autoim- respond as well and the dermatologist may inject a mune mechanisms cause the lupus disorders, or corticosteroid medication directly into the lesion. what triggers them. Because DLE and SLE seem to Some people experience relief with medications run in families, a genetic component is likely. At otherwise prescribed to treat MALARIA, RHEUMATOID present there are no known preventive measures. ARTHRITIS, and severe ACNE, as well as medications Though women are more likely than men to that act on the IMMUNE SYSTEM such as the corticos- develop DLE, there are no clear risk factors for the teroids and immunomodulators. These medica- condition other than family history. Early treat- tions have potentially serious side effects and ment minimizes the residual scarring, atrophy, interact with numerous other medications. alopecia (hair loss), and other permanent conse- Women who are pregnant or who could become quences the lesions can cause. pregnant cannot take many of them, as they cause Cigarette smoking worsens the lesions, so doc- damage to the developing fetus. tors strongly advise people who have DLE and The use of some of these medications is OFF LABEL smoke to stop. Sun exposure also increases the USE—that is, not a use the US Food and Drug frequency and number of lesions; liberal applica- Administration (FDA) has approved though the tion of high-SPF sunscreen and sun-blocking DRUG itself has FDA approval for other uses. clothing can mitigate this effect. It is important for people who have DLE to See also AUTOIMMUNE DISORDERS; LEUKOPLAKIA; discuss with their doctors, and to fully under-stand, LESION; LICHEN PLANUS; SARCOIDOSIS; SJÖGREN’S SYN- the potential benefits and risks of all treatment DROME; SMOKING CESSATION; SUN PROTECTION. options. Treatment approaches for DLE target symptoms though do not cure the condition itself. dry skin See ICHTHYOSIS. E

eczema See DERMATITIS. protein structures which connect the epidermis and dermis through the basement membrane. ecchymosis The clinical term for a bruise. • Dystrophic epidermolysis bullosa involves the Ecchymosis occurs when there is bleeding into the basement membrane as well, occurring in layers of the SKIN, causing discoloration and some- either an autosomal dominance or a recessive times swelling and discomfort. The injured area inheritance pattern for the gene that encodes typically undergoes several, and sometimes vivid, collagen formation. color changes during the stages of HEALING. Ecchy- mosis usually results from trauma to the tissue, In all types, bullae form with friction or irrita- such as a blow. Ecchymosis may also occur as a tion to the skin. In the junctional and dystrophic symptom of bleeding disorders, LEUKEMIA, LIVER types, this includes the mucous membranes of the disease, and other health conditions. Ecchymosis gastrointestinal and genitourinary tracts. Healed that develops without known trauma warrants a bullae typically leave scars. The severity of symp- doctor’s evaluation to determine the underlying toms and disease vary according to the type and, cause. with dystrophic epidermolysis bullosa, the inheri- See also BLACK EYE; PETECHIAE; PURPURA. tance pattern (dominant or recessive). At present there is no cure for any type of epidermolysis bul- epidermolysis bullosa The collective term for a losa. group of inherited SKIN disorders that result in blis- terlike formations (bullae) on the skin. Severity Symptoms and Diagnostic Path can range from mild (a few bullae) to debilitating The bullae of epidermolysis bullosa are uniquely (bullae covering large areas of the body). Derma- characteristic and typically begin in infancy. The tologists classify epidermolysis bullosa according to skin is frail and may BLISTER or tear upon touch or the layer of the skin where the bullae originate. contact with clothing and bedding. The bullae of There are three general types of epidermolysis epidermolysis bullosa simplex generally affect only bullosa: the palms of the hands and soles of the feet. The bullae of other types may affect mucous mem- • Epidermolysis bullosa simplex involves the epi- branes throughout the body. The repeated blister- dermis, the skin’s outermost layer, and usually ing and HEALING of junctional and dystrophic types results from an autosomal dominance inheri- causes scarring and tissue damage that often tance pattern for the gene that encodes keratin results in deformities. People who have junctional production. or dystrophic epidermolysis bullosa may also have • Junctional epidermolysis bullosa involves the defects of the tooth enamel and the NAILS, or be basement membrane, a thin layer of cells that missing fingernails or toenails. separates the epidermis and the dermis, and The diagnostic path includes examination of usually results from an autosomal recessive the entire skin surface and mucous tissues with inheritance pattern for the gene that encodes biopsy to determine the level of tissue separation

154 erysipelas 155 in representative bullae, which distinguishes the See also BULLA; FAMILY MEDICAL PEDIGREE; GENETIC general type of epidermolysis bullosa. Molecular DISORDERS; HYPERHIDROSIS; MUSCULAR DYSTROPHY; examination, including DNA mutation analysis SCAR; SKIN SELF-EXAMINATION; TEETH. identifies the precise type. CHORIONIC VILLI SAMPLING (CVS) during PREGNANCY (removing a small tissue erysipelas A streptococcal INFECTION of the der- sample from the edge of the PLACENTA) can identify mis, the middle layer of the SKIN. Infection com- whether the FETUS has the disorder. monly follows STREP THROAT, with the BACTERIA likely carried on the hands to the skin where a Treatment Options and Outlook scratch or other breach allows the bacteria to colo- Treatment attempts to minimize or prevent bullae nize into an infection. The infection presents char- formation, heal bullae that do form, and provide acteristic symptoms that allow prompt clinical necessary supportive care such as PARENTERAL diagnosis. These symptoms include NUTRITION. Healing mechanisms are often impaired, and ruptured bullae and related tissue damage can • redness (erythema), swelling (edema), and PAIN leave tissues exposed. Burn therapies such as arti- at the site of the infection ficial skin can provide a temporary covering to • clearly defined and usually raised border improve healing. Support groups offer forums for between the infection and healthy skin sharing experiences and coping methods. • swelling of adjacent LYMPH NODES People who have mild forms of disease may experience few bullae or complications and be • FEVER, generalized discomfort, and aching in the able to enjoy fully active lives. More severe forms muscles and joints are debilitating or fatal. It is important though dif- ficult to prevent ruptured bullae from becoming Treatment is a course of ANTIBIOTIC MEDICATIONS, infected. Nutritional deficiencies are common preferably penicillin unless the person is allergic, when bullae form along the gastrointestinal and medications to relieve pain and fever. Warm mucosa, which may interfere with swallowing compresses help bring blood to the area, improv- (bullae that form in the ESOPHAGUS) or absorption ing the effectiveness of the body’s IMMUNE RESPONSE (bullae that form in the SMALL INTESTINE). The risk to attack the infection and increasing circulation for squamous cell SKIN CANCER is very high among of the antibiotic. people who have junctional epidermolysis bullosa, with first appearance often in late ADOLESCENCE. It is important for people to take ANTIBI- Dermatologists advise frequent skin self-examina- OTIC MEDICATIONS prescribed to treat tions and regular skin examinations by a derma- erysipelas as the doctor directs, and to tologist who has clinical experience with use them until all the antibiotic is gone, epidermolysis bullosa. to completely eradicate the streptococ- cal BACTERIA. Risk Factors and Preventive Measures Epidermolysis bullosa is a genetic disorder, so the Prompt medical attention is essential as primary risk factor is a family history of the condi- erysipelas can rapidly invade deeper tissues, caus- tion. In autosomal recessive INHERITANCE PATTERNS, ing CELLULITIS and perhaps SEPTICEMIA (bodywide it is possible for each parent to carry the gene infection). Untreated or undertreated streptococ- defect yet show no indications of disease or to cal infections also present the risk for INFLAMMA- have a mild form and not realize it. GENETIC TEST- TION of the HEART valves (RHEUMATIC HEART DISEASE). ING can help families detect the presence of the With treatment, symptoms improve within 72 gene MUTATION, and GENETIC COUNSELING can help hours and the erysipelas resolves completely in 10 couples in making family-planning decisions. to 14 days. People who have DIABETES, impaired Researchers continue to explore GENE THERAPY peripheral circulation, and IMMUNE DISORDERS are solutions. at increased risk for erysipelas. Preventive meas- 156 The Integumentary System ures include HAND WASHING after coughing or Nearly always the lesions heal without scarring or sneezing. other complications. Prevention of future out- See also SCARLET FEVER. breaks is difficult as there are so many potential causes. erythema multiforme A HYPERSENSITIVITY REAC- See also TOXIC EPIDERMAL NECROLYSIS; URTICARIA. TION, commonly to medications and sometimes to viral INFECTION, in which circular, weltlike lesions erythema nodosum The eruption of red nodules resembling targets form on the arms, hands, legs, along the top surfaces of the lower legs (shins). and feet. Lesions also often form on and around Erythema nodosum is nearly always a symptom of the lips and inside the MOUTH. The center of the an underlying condition, often a streptococcal LESION is typically pale and blistered, surrounded INFECTION, and represents INFLAMMATION of the fatty with a reddened (erythematous) middle ring. The tissue at the foundation of the SKIN. Other symp- outer ring often has a purplish tint, giving it a toms include FEVER, PAIN and swelling in the joints, bruiselike appearance. Lesions typically begin and generalized discomfort and malaise. Erythema erupting within three days of the causative expo- nodosum occurs most commonly in young adults sure, rising suddenly. Some people experience tin- between the ages of 18 and 30. gling, itching, or a burning sensation at the site of The initial eruption of nodules may clear in six the lesion. to eight weeks, though outbreaks tend to recur Common causes of erythema multiforme over months to years. Over the course of HEALING include the nodules change color from their original bright red to bluish red and ultimately yellow, resem- • infection with the HERPES SIMPLEX VIRUS bling bruises, before fading completely. The doctor • ANTIBIOTIC MEDICATIONS diagnoses erythema nodosum primarily on the basis of its appearance, though may run BLOOD • ANTISEIZURE MEDICATIONS tests to look for evidence of AUTOIMMUNE DISORDERS • aspirin and NONSTEROIDAL ANTI-INFLAMMATORY or infection that may underlie the outbreak. Treat- DRUGS (NSAIDS) ment targets the underlying cause and may • numerous other medications include ANTIBIOTIC MEDICATIONS when there is infec- tion or anti-inflammatory agents such as NON- The uniquely characteristic lesions in provide STEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS) to fairly conclusive diagnosis. The causative agent relieve swelling, pain, and fever. may be clear, such as a recently taken medication, See also JOINT; NODULE; TUBERCULOSIS. or remain unknown (idiopathic). Most erythema multiforme outbreaks are self-limiting and clear erythrasma A chronic bacterial INFECTION of the up two to three weeks after exposure to the epidermis (outer layer of the SKIN) that produces causative agent ends. Treatment to provide relief scaly, brownish red patches that often itch. The from discomfort may include ANTIHISTAMINE MED- patches may occur anywhere on the body though ICATIONS for itching, ANALGESIC MEDICATIONS for PAIN are most common in skin folds and moist areas relief, and topical corticosteroids for INFLAMMATION. such as the underarm (axilla) and groin. When

CONDITIONS ASSOCIATED WITH ERYTHEMA NODOSUM STREP THROAT rheumatic FEVER SCARLET FEVER Hodgkin’s LYMPHOMA Hansen’s disease bacterial infection fungal INFECTION adverse reaction to sulfonamides PREGNANCY ADVERSE REACTION to sulfonylureas oral contraceptives HISTOPLASMOSIS INFLAMMATORY BOWEL DISEASE (IBD) non-Hodgkin’s lymphoma SARCOIDOSIS erythrasma 157 viewed under ultraviolet light, the areas of infec- with all antibiotics, it is important to take the tion appear a deep coral color. Corynebacteria, BAC- erythromycin (or other prescribed antibiotic) as TERIA normally present on the skin, are responsible the doctor directs and until the medication is for the infection. People who have DIABETES or gone. Erythrasma may recur (come back) if the OBESITY are especially susceptible to erythrasma. environment of the skin continues to support the Treatment is topical and sometimes oral erythro- growth of Corynebacteria. mycin, an antibiotic medication, which completely See also ANTIBIOTIC MEDICATIONS; CELLULITIS; eliminates the infection within 10 to 14 days. As ERYSIPELAS. F–G

facelift See RHYTIDOPLASTY. risk factors can precipitate its occurrence. Among them are Fitzpatrick skin type A commonly used classifi- OBESITY cation system for identifying a person’s SKIN char- • acteristics, particularly the likelihood for SUNBURN • HYPERHIDROSIS and developing ACTINIC KERATOSIS and SKIN CANCER. • DIABETES Dermatologists also use Fitzpatrick skin type as a • DERMATITIS and SKIN irritations factor in determining appropriate cosmetic proce- dures to treat skin blemishes and WRINKLES. • long-term topical corticosteroid use See also SKIN SELF-EXAMINATION. • ABRASIONS • immunosuppressive disorders such as HIV/AIDS folliculitis An infected and inflamed HAIR follicle. Folliculitis may involve a single follicle or a num- Warm compresses applied to the site several ber of follicles in proximity, and begins with a red- times a day may resolve isolated folliculitis. Folli- dened bump at the site of the follicle that soon culitis that persists or involves multiple hair folli- progresses to a PUSTULE containing a collection of cles requires treatment with topical and oral fluid and cells (pus). The site often hurts or itches. ANTIBIOTIC MEDICATIONS. Most folliculitis improves Most folliculitis is idiopathic—that is, it develops within a few days of antibiotic therapy, though it without identifiable cause. However, a number of is important to take the full amount of medication

FITZPATRICK SKIN TYPE CLASSIFICATIONS Type Skin characteristics Sun exposure type I very pale or ruddy; numerous freckles always BURNS, never tans; severe SUNBURN (blisters) with unprotected exposure; high risk for SKIN CANCER type II pale or light-toned; some freckles mostly on usually burns, lightly tans; moderate sunburn (redness) face, shoulders, arms, hands with unprotected exposure; increased risk for skin cancer type III olive sometimes burns, moderately tans; mild sunburn (pinkness) with unprotected exposure; moderate risk for skin cancer type IV light brown seldom burns, easily tans; low risk for skin cancer type V brown rarely burns, darkly tans; seldom develops skin cancer type VI dark brown to brownish black never burns; rarely develops skin cancer

158 frostbite 159 as the doctor directs. In people who frequently frostbite Damage to the SKIN that results from have folliculitis or who are on long-term antibiotic prolonged exposure to extremely cold tempera- therapy such as for ACNE, the INFECTION may resist tures. Frostbite occurs when the fluid in cells crys- the common first-line antibiotics, requiring fur- tallizes into ice, causing the skin and often the ther therapy with a different antibiotic. Folliculitis underlying tissues to freeze. The fingers, hands, usually heals without scarring or residual compli- toes, feet, NOSE, and ears are most vulnerable to cations. frostbite. People who have impaired peripheral circulation are at increased risk. Frostbite also can HOT TUB FOLLICULITIS damage blood vessels, interrupting the blood sup- The hot, moist environment of a hot tub is the ply. When this occurs, GANGRENE (tissue death) and ideal incubator for various BACTERIA, notably the subsequent loss of the body part are significant Pseudomonas aeruginosa. The warm water of the threats. hot tub opens the pores, giving the bacteria access to the HAIR follicles. When the pores close Symptoms and Diagnostic Path after leaving the hot tub, they trap P. aeruginosa, Any loss of feeling following extended exposure to which thrives in the moist setting. Folliculitis the cold raises suspicion of frostbite and is the first results, often appearing on the SKIN the same pat- factor to consider when evaluating potential frost- tern of the clothing worn in the tub. bite. The ice crystals that form cause the skin to become hard, pallid, and cold to the touch. There See also CARBUNCLE; FURUNCLE; PSEUDOFOLLICULITIS is loss of feeling and function, and the skin may BARBAE. BLISTER. Skin that has remained frostbitten for a long time may already be gangrenous or necrotic freckles See LENTIGINES. (blackened and dead). As it warms, frostbitten

FROSTBITE SEVERITY Degree of Damage Characteristics Recovery Implications first degree spots of whitened, hardened SKIN involving primarily the recovery with no residual complications epidermis erythema (redness) of adjacent skin; localized edema (swelling) distorted or absent sense of touch or clumsy movements second degree areas of whitened, hardened skin involving the epidermis recovery with some residual and dermis complications (scarring) erythema of adjacent skin; regional edema loss of feeling and movement fluid-filled blisters third degree white, hard skin with frostbite extending through the layers recovery with moderate residual of the skin and into the subcutaneous tissue complications (tissue loss and scarring) regional edema loss of feeling and movement blood-filled blisters fourth degree white, hard skin with frostbite extending through the skin significant loss of tissue, with AMPUTATION and into supporting tissues and structures likely GANGRENE or necrosis; regional edema 160 The Integumentary System skin turns red and BURNS or hurts, sometimes People who are very young or very old or who have severely. DIABETES, PERIPHERAL VASCULAR DISEASE (PVD), RAYNAUD’S SYNDROME, untreated or undertreated Treatment Options and Outlook HYPOTHYROIDISM, OR MALNUTRITION may develop frost- Prompt treatment is essential to save the affected bite far more rapidly and severely. Preventive tissue and body parts. When possible, a doctor measures include protective clothing appropriate should evaluate the situation and implement for the weather conditions and limiting exposure warming procedures for maximum recovery. To when temperatures are extremely cold. protect body parts until the person receives med- See also HYPOTHERMIA. ical treatment, wrap them in sterile bandages (sep- arating the fingers and toes, if affected). When furuncle An infected HAIR follicle, commonly immediate medical attention is not possible, called a boil. A furuncle develops when BACTERIA warming the frostbitten areas should only be normally present on the surface of the SKIN (typi- undertaken when they cannot refreeze. cally staphylococcus) causes a collection of dead cells and fluid (pus) to block the follicle. The Refreezing does more damage than blocked follicle becomes reddened, inflamed, allowing the area to remain frozen. Do enlarged, and usually quite painful. Furuncles are not thaw frostbite unless the area can most likely to develop in the underarm area, remain warm. groin, hairline at the back of the neck, and, in men, the beard area of the face. To warm frostbite, place the affected parts Most furuncles improve with frequent applica- under gently running warm water for 20 to 30 tions of moist heat, which helps open the follicle minutes. The water temperature should be 8º to and drain the collected pus. A typical furuncle 10ºF above normal body temperature or about heals on its own in 7 to 10 days, though a large 108ºF, which feels warm but not hot to someone furuncle may take longer. A furuncle that does whose skin temperature is normal. For frostbitten not improve within 10 days warrants a doctor’s ears, cheeks, or nose, apply cloths dipped in warm evaluation and may require lancing (a small inci- water. Do not use dry heat, as it will further dam- sion to drain the INFECTION) or ANTIBIOTIC MEDICA- age the skin and tissues. Severe frostbite is likely TIONS. People who have DIABETES or who are better left for emergency care providers to treat IMMUNOCOMPROMISED are more likely to develop because tissue damage is likely to be extensive. furuncles. The thawing process can be extremely painful, Furuncles tend to recur. Preventive measures and may require PAIN relief medications. Superfi- include reducing irritation from clothing and regu- cial frostbite (first and second degree) usually lar cleansing with an antibacterial soap. Prompt heals with few or no residual consequences. Frost- treatment at the earliest indication of a furuncle bite that extends deeper than the layers of the can minimize or head off the infection’s develop- skin (third and fourth degree) can destroy MUSCLE, ment. A large furuncle may leave a SCAR after it connective tissue, joints, and BONE, and may heals, though most furuncles heal without scarring. necessitate AMPUTATION or surgery to clean away See also CARBUNCLE; FOLLICULITIS; INGROWN HAIR; necrotic tissue. A full damage assessment may not PSEUDOFOLLICULITIS BARBAE. be possible for six to eight weeks, as it may take that long for tissue to demonstrate whether it will goose bumps A bumpy texture to the SKIN, also recover or die. called gooseflesh, that results when the erector muscles in the HAIR follicles contract, causing the Risk Factors and Preventive Measures hair to “stand up.” Goose bumps occur when a People who spend extended time outdoors in cold person becomes chilled or fearful, a vestigial weather, such as for employment or recreation, risk response no longer physiologically useful in frostbite when exposure time extends beyond what humans. The physiologic mechanism that causes clothing can protect. Wetness increases the risk. goose bumps, called the pilomotor REFLEX or pilo- granuloma telangiectaticum 161 erection, is involuntary. Researchers believe it is in hemangioma or GRANULOMA pyogenicum, made up part the consequence of the release of stress hor- of entangled capillaries. A granuloma telang- mones, primarily EPINEPHRINE (also called adrena- iectaticum appears suddenly as a shiny red NODULE line), which stimulates the HYPOTHALAMUS. In other that bleeds easily with bumping or irritation and mammals the pilomotor reflex raises the hair or may itch or hurt. Doctors typically remove these fur for warmth by trapping air near the skin’s sur- growths because of their tendency to bleed and to face or to present an intimidating appearance by confirm the diagnosis through biopsy (examina- making the animal appear larger than it is. Goose tion of a tissue sample under the microscope). The bumps often accompany shivering, rapid and cause of granuloma telangiectaticum remains involuntary muscle contraction to generate heat. uncertain; in some people the growth arises fol- See also HORMONE; METABOLISM; MUSCLE; THYROID lowing trauma to the site, though the nodules GLAND. most often occur without a known precipitating event. The growths may recur. granuloma telangiectaticum A noncancerous See also ANGIOMA; SKIN SELF-EXAMINATION; vascular tumor, also called a lobular capillary TELANGIECTASIS. H hair The fibers that grow from the hair follicles. melanocytes that give it color. Sebum (the natural Not far above the root of the hair follicle the cells oil that lubricates the hair follicle) production that form the hair fiber are dead, hardened into slows, allowing the hair to become dry. Sun expo- their shape through compression within the folli- sure also can alter the hair, lightening its color or cle as new cells emerging from the hair’s root push extracting moisture to make it brittle. Hair-care them upward. A hair fiber is five or six cells in products can help restore moisture to the hair on thickness and varies in length, depending on its the head as well as to the skin of the scalp. location. Hair on the head can grow to several feet in length, whereas the hair of the eyelashes is HEALTH CONDITIONS THAT MAY INVOLVE THE HAIR generally no longer than about a quarter of an ADVERSE REACTION to a DRUG ALOPECIA inch long. The hair does not require nourishment ALOPECIA AREATA ERYTHEMATOSUS (SLE) from the body, though the secretions of the seba- DANDRUFF DISCOID LUPUS ERYTHEMATOSUS ceous glands help moisturize the hair fibers to FILLICULTIS (DLE) keep them supple. FURUNCLE HIRSUTISM Genetic encoding determines the characteristics HYPOTHYROIDISM INGROWN HAIR of the hair, from how rapidly it grows to whether it KERATOSIS PILARIS LICHEN PLANUS is curly or straight. Hair covers all SKIN surfaces MENOPAUSE nutritional deficiencies except the palms of the hands and the soles of the PREGNANCY PUBERTY feet, though is most prominent on the head and, ringworm stress after PUBERTY, in the pubic region, on the legs, and SYSTEMIC LUPUS ERYTHEMATOSUS toxic exposure under the arms. Men typically have darker, coarser (SLE) TRICHOTILLOMANIA body hair than women. Specialized hairs line the auditory canals and the inside of the NOSE, func- For further discussion of the hair within the tioning to remove debris from these structures. context of integumentary structure and function Like the skin, the hair provides clues to the please see the overview section, “The Integumen- health of the body. Numerous conditions can tary System.” change the characteristics of the hair. Such See also AGING, INTEGUMENTARY CHANGES THAT changes reflect circumstances that affect the hair OCCUR WITH; BEZOAR; MELANOCYTE; NAILS; SEBACEOUS follicles in some way, from physical damage, such GLAND; SWEAT GLANDS. as BURNS or scars that can destroy follicles, to immune or disease processes that attack the folli- hair replacement A surgical procedure, also cles and disrupt hair growth. Physical stress such called hair transplantation, to relocate viable HAIR as the body experiences with major injury, illness, follicles from sites on the scalp where they are or surgery can cause various changes in the hair, abundant to sites where there has been perma- from altered color and consistency to hair loss. nent hair loss. The most common reason for hair The hair’s characteristics also change with aging. replacement is androgenic ALOPECIA (male pattern By midlife the hair typically starts to lose the hair loss). Hair replacement is nearly always a cos-

162 hair replacement 163 metic procedure, though may be restorative to common variation of tissue flap hair replacement correct damage resulting from injuries or BIRTH is scalp reduction, in which the surgeon removes DEFECTS. more hairless scalp than the replacement flap cov- ers, drawing the edges tight to pull additional hair Surgical Procedure from the sides of the head higher onto the crown Hair replacement procedures may involve tissue of the head. Tissue flaps generally heal with less grafts, flaps, expansion, or combinations of these chance of rejection than grafts because they methods. The surgeon will plan the appropriate remain anchored to their original blood supply. approach for each individual’s situation and hair Tissue expansion Plastic surgeons developed loss circumstances. The OPERATION is an AMBULA- TISSUE EXPANSION techniques to reconstruct major TORY SURGERY, performed with local ANESTHESIA and skin damage following trauma such as BURNS or a sedative for comfort. Most people require several major surgery, then discovered tissue expansion operations to establish satisfactory results. Mild to allows natural expansion of hair-bearing scalp for moderate PAIN is common for several days follow- hair replacement. The surgeon loosens a segment ing a hair replacement procedure. of hair-bearing skin adjacent to an area of hairless Tissue grafts SKIN grafts were the original hair skin to create a pouch, and inserts a special sili- transplantation method. The surgeon removes a cone balloon called a tissue expander. plug or slice of skin from the back or side of the Over a period of months the surgeon injects head and transplants it to a hair loss site. The graft saline (sterile saltwater) into the expander, gradu- may contain from one or two to several hundred ally increasing its size. As the expander stretches, hair follicles, depending on the technique and the skin grows to accommodate it. When the area size. With the first replacement procedure the sur- produces the desired amount of growth, the sur- geon places the grafts fairly widely apart (about geon removes the expander, surgically removes a one eighth inch) to allow generous BLOOD circula- similarly sized and shaped segment of hairless tion. Subsequent grafts fill in the spaces. Gener- scalp, and pulls the new skin over the area. Tissue ally, a pressure bandage holds the grafts in place expansion can relocate the greatest surface area of for 24 to 48 hours following surgery to help the hair-bearing skin in a single procedure and pro- transplanted skin attach to the new site, and fine duces the most natural-appearing frontal hairline. sutures (stitches) close the donor sites. Risks and Complications HAIR REPLACEMENT GRAFT TECHNIQUES Risks and complications are slight for hair replace- Type of Graft Follicles Contained Grafts per Session ment methods, and include excessive bleeding, punch graft 10 to 15 50 INFECTION, and reaction to the anesthetic. The micrograft 1 to 2 500 to 700 recipient site on the scalp also may reject the minigraft 2 to 4 500 to 700 replacement tissue. Because relocation trauma- slit graft 4 to 10 500 to 700 tizes hair follicles, they immediately enter a rest- strip graft 20 to 40 500 to 700 ing phase and shed their hair about five to six weeks following relocation. Though this is normal, Tissue flaps A tissue flap relocates a substantial many people find it alarming and worry that it amount of hair-bearing skin to a single recipient signals rejection of the new hair. However, with site. The surgeon loosens a flap of skin near the rejection the entire segment of relocated skin fails area of hair loss, and removes a similarly sized and to grow and eventually sloughs off. The surgeon shaped segment of skin from the hairless scalp. can generally replace the rejected replacement tis- The surgeon leaves one end of the flap attached sue during the next session of surgery. When they and pulls the remainder of the flap over the recipi- reestablish themselves in their new sites, the folli- ent site, suturing it in place. The surgeon also cles return to a growth phase and produce about sutures the edges of the donor location, which an inch of new hair within six to eight weeks after heals beneath the hair with no visible SCAR. A the old hair falls out. 164 The Integumentary System

Outlook and Lifestyle Modifications not know what causes hidradenitis suppurativa to For the first few weeks following surgery the scalp develop, though it is more common in people who is swollen and tender, and the replacement sites have OBESITY. may bleed with strenuous physical activity. Sur- See also ABSCESS; CELLULITIS; FOLLICULITIS. geons recommend refraining from intense exercise or activity and contact sports for two or three hives See URTICARIA. weeks after the procedure. The scalp remains ten- der (though the swelling subsides within a few hyperhidrosis Excessive sweating that results weeks) for up to three or four months, depending from abnormal functioning of the nerves or BLOOD on the replacement method. Transplanted hair vessels that supply the eccrine SWEAT GLANDS. growth does not look exactly the same as the hair Hyperhidrosis characteristically involves the hands that previously grew from the transplant site, (palms), feet (soles), and axillae (underarms), though most people experience satisfactory results though can affect eccrine sweat glands anywhere when a qualified and experienced cosmetic sur- in the body. The eccrine sweat glands produce geon performs the surgery. It generally takes a most of the body’s sweat and play a key role in year or two from the final hair replacement proce- thermoregulation (regulating body heat). They dure to see the full effects. empty their fluids (perspiration) directly to the There must be abundant healthy hair on the SKIN’s surface for rapid evaporation and cooling. back and sides of the head to serve as donor hair. Stress and physical activity tend to exacerbate Men in whom male pattern hair loss begins early hyperhidrosis, particularly when it affects primar- in life are more likely to experience severe or total ily the hands and feet. The portion of the BRAIN hair loss as they age. Satisfactory results from hair that regulates sweating in these areas, the cerebral replacement surgery are less certain when this is cortex, is not part of the body’s thermoregulation the case, as the transplanted follicles may also system but rather responds to emotional signals experience hair loss. Hair loss from follicles native such as anxiety and fear. Hyperhidrosis may also to the site generally continues, particularly in occur as an undesired SIDE EFFECT of medications male pattern hair loss, which can result in irregu- or a symptom of metabolic disorders such as lar growth patterns and the need for further hair HYPERTHYROIDISM and DIABETES, or health conditions replacement. such as TUBERCULOSIS and Hodgkin’s LYMPHOMA. See also ANALGESIC MEDICATIONS; PLASTIC SURGERY; Most hyperhidrosis that arises from structural or SURGERY BENEFIT AND RISK ASSESSMENT. functional anomalies of the nerves or blood ves- sels first appears in ADOLESCENCE, when the hor- hidradenitis suppurativa A condition of chronic monal changes of PUBERTY stimulate sweat gland INFLAMMATION resulting from blockage of the HAIR function. Hyperhidrosis that begins later in life follicles (follicular occlusion). The inflammation generally arises from underlying health condi- may involve the apocrine glands, SWEAT GLANDS tions. that secrete fluid into the hair follicles. The hair follicles then channel the sweat to the surface of Symptoms and Diagnostic Path the SKIN. When sebum or cellular debris plugs the The primary symptom of hyperhidrosis is pro- apocrine gland’s opening, fluid backs up into the fusely excessive sweating. The hands and feet, gland. The situation results in an INFECTION that when involved, may be continually wet. Sweating produces a hard, painful, reddened NODULE below from the underarms and other areas of the body the skin’s surface. Though the nodules will heal in typically drenches clothing, requiring frequent three or four weeks without treatment, they often clothing changes. The diagnostic path typically SCAR and recur. Treatment with oral ANTIBIOTIC includes a comprehensive NEUROLOGIC EXAMINATION MEDICATIONS may help control the condition and blood tests to measure HORMONE levels. The though does not always clear it up. Occasionally doctor may conduct further diagnostic procedures, the dermatologist needs to lance (surgically open) depending on the individual’s health circum- the nodule to allow it to drain. Dermatologists do stances. hyperhidrosis 165

Treatment Options and Outlook • Botulinum therapy (localized injection of puri- Treatment options currently available in the fied botulinum toxin) blocks acetylcholine, United States include topical products, oral med- interrupting the flow of NERVE signals to the ications, BOTULINUM THERAPY, iontophoresis, and, muscles that contract to push fluid from the when other treatments are unsuccessful, surgery. sweat glands. The effect can last for six months or longer. • Topical products block the pores of the sweat • Surgery to sever some of the nerves supplying glands. Those commonly used include alu- the sweat glands, or to remove clusters of sweat minum chloride preparations, boric or tannic glands such as in the axillae, is a treatment of acid solutions, glutaraldehyde, and potassium last resort for severe hyperhidrosis that does permanganate. These products may stain the not respond to other treatments. The effects are skin and clothing. Most people apply them at permanent. night and wash them off in the morning. • Oral medications interrupt the action of the Many people who have hyperhidrosis use com- nerves that regulate sweat gland activity. Those binations of these approaches to control their commonly used are anticholinergics such as symptoms. Hyperhidrosis is often deeply embar- propantheline and benztropine, which block rassing to those who have it, particularly adoles- the action of the NEUROTRANSMITTER acetyl- cents. Because stress plays a key role in choline. Dermatologists sometimes prescribe hyperhidrosis, stress management techniques are other medications such as beta-blockers and often helpful for coping with the condition as well calcium channel blockers. These medications as reducing the stimuli that exacerbate symptoms. may have unacceptable side effects, however, and they are not approved for this use in the Risk Factors and Preventive Measures United States. When an underlying health condition is the cause • Iontophoresis uses mild electrical current in a of the hyperhidrosis, treating the condition elimi- water-based solution to shrink the sweat gland nates the hyperhidrosis. Primary hyperhidrosis is a pores and is a treatment option for hyperhidro- lifelong condition for which there are no known sis of the hands and feet. Relief generally risk factors or preventive measures. requires daily treatments over a period of sev- See also OFF-LABEL USE; STRESS AND STRESS MAN- eral weeks. AGEMENT; TINEA INFECTIONS. I–J

ichthyosis A genetic disorder of keratinization in impetigo A contagious bacterial INFECTION of the which the cells the SKIN sheds as part of its contin- SKIN that most commonly affects young children. ual renewal cluster on the skin’s surface in scale- Staphylococcal or streptococcal BACTERIA are the like formations. The lesions itch and flake, and the usual culprits, typically taking advantage of involved surfaces of the skin become very dry, breeches in the skin’s integrity that result from reddened, and inflamed. Ichthyosis may affect rashes, insect bites, and other minor wounds. The limited areas of the skin or most of the skin’s sur- infection begins as small blisters, often around the face, depending on which of several GENE muta- MOUTH, that itch and burn. Scratching or touching tions is responsible for the condition. Ichthyosis is the blisters and then touching other parts of the chronic and lifelong, with symptoms first appear- body spreads the infection. Contact also spreads ing in early childhood. Ichthyosis may be heredi- the infection to other people. After two or three tary or acquired. Symptoms of hereditary days the blisters rupture, ooze, and crust. The ichthyosis are present at birth and can be severe, crust is characteristically honeylike in color and often affecting the eyes and eyelids. appearance. The blisters remain contagious as long The dermatologist can usually diagnose as they are present. ichthyosis on the basis of its appearance, though Treatment is a topical antibiotic applied to the may biopsy several lesions to confirm the diagno- blistered areas. The doctor may also prescribe an sis. Treatment attempts to restore moisture to the oral antibiotic medication when the infection skin as well as to accelerate exfoliation (remove extends to multiple areas of the body. The blisters dead cells from the skin’s surface). Lotions, begin to recede within 24 to 48 hours of initiating creams, and ointments containing lanolin or other treatment, which eases the itching and discomfort. emollients help the skin retain moisture, which The blisters are no longer contagious at this stage, eases the itching and INFLAMMATION. Topical prod- and generally heal completely within five to seven ucts that contain fruit acids such as alphahydroxy days. Frequent HAND WASHING with antibacterial acid or lactic acid help remove dead cells. soap and warm water helps stop the spread of Severe ichthyosis may require topical or oral impetigo among children, family members, and treatment with a retinoid medication such as caregivers. Prompt cleansing and treatment of isotretinoin. The scaly lesions tend to overlap one minor skin irritations reduces the opportunity for another and can trap BACTERIA and other microor- impetigo to develop. ganisms normally present on the skin’s surface, See also ANTIBIOTIC MEDICATIONS; BLISTER; RASH; causing INFECTION that requires treatment with TINEA INFECTIONS. topical or oral ANTIBIOTIC MEDICATIONS. An ophthal- mologist should provide monitoring and care to ingrown hair A new HAIR that curls as it grows, detect and promptly treat EYE symptoms to pre- slicing into the side of the hair follicle instead of vent permanent damage to the CORNEA and to pre- arising from it to extend above the surface of the serve vision. SKIN. An ingrown hair forms a painful red bump. See also DERMATITIS; KERATITIS; LESION; MUTATION; The hair may grow its way through the wall of the PRURIGO; PSORIASIS. follicle and above the skin, or may block the folli- 166 jock itch 167 cle, causing INFLAMMATION and INFECTION (FOLLICULI- Tight-fitting shoes are a common cause of TIS). People who have curly or kinky hair are more ingrown toenails. The shape of the toes also is a likely to develop ingrown hairs. Men may develop factor, with nails that have a pronounced curve ingrown hairs in the beard area as a consequence being more likely to grow into the side of the toe. of shaving, sometimes called shaving bumps or A common but ineffective home remedy for shaving rash. ACNE and other inflammatory condi- ingrown toenails is to cut a “V” into the top edge tions of the skin that block the follicles can cause of the nail with the presumption that doing so will ingrown hairs. Moisturizing the skin helps open draw the edges of the nail away from the skin as the follicles, allowing the hair to grow outward. the nail grows. The shape of the nail bed deter- Warm compresses can help release cells and mines the growth pattern of the nail, however. sebum clogging the follicles, releasing the hair. The jagged edges that result at the top of the nail Regular skin cleansing and mild exfoliants also from this method present the potential for tears help keep the follicles clear. and snags that can separate the nail from the toe, See also CARBUNCLE; DANDRUFF; FURUNCLE; another painful problem. PILONIDAL DISEASE; PSEUDOFOLLICULITIS BARBAE. In some people ingrown nails tend to recur and may require more aggressive treatment such as ingrown nail A toenail, or less commonly a fin- removal of additional nail or the entire nail. Most gernail, that grows beneath the surrounding SKIN. people experience permanent relief after a single An ingrown nail, also called onychocryptosis, is treatment to remove the edges of the nail. Podia- painful and easily become infected. Often the tissue trists recommend trimming the nails straight around the nail swells and grows over the nail across, with a slight margin over the edge of (hypertrophy), further aggravating the site. the toe. People who have DIABETES, PERIPHERAL VAS- Ingrown NAILS require medical attention and often CULAR DISEASE (PVD), or other conditions that minor surgery done in the provider’s office. The impair blood circulation to the feet should inspect provider injects the involved finger or toe with an their feet daily and see a doctor or podiatrist anesthetic to numb it, then clips the corners of the regularly as well as at the first indication of irrita- ingrown nail to release it from the skin and trims tion. away the excess tissue. Typically the doctor then See also CORNS; PARONYCHIA. applies a caustic solution, usually an acid prepara- tion, to prevent the portion of nail from regrowing. jock itch See TINEA INFECTIONS. K

Kaposi’s sarcoma A CANCER that develops in the Transplant-related Kaposi’s sarcoma People connective tissues that support the SKIN, with who undergo organ transplantation typically characteristic lesions on the skin and mucous receive immunosuppressive therapy, to prevent membranes. There are several types of Kaposi’s organ rejection, for the rest of their lives. The sarcoma. The two that are most common in the development of Kaposi’s sarcoma arises from the United States are AIDS-related Kaposi’s sarcoma immunosuppression, not the organ transplantation. and transplant-related Kaposi’s sarcoma. The American Cancer Society estimates that about In 1994 researchers discovered that human 1 in 200 transplant recipients taking immunosup- herpesvirus 8 (HHV-8), sometimes called Kaposi’s pressive therapy to prevent organ rejection sarcoma–associated herpesvirus (KSHV), causes develop Kaposi’s sarcoma. People who take long- Kaposi’s sarcoma. However, the path of transmis- term immunosuppressive therapy for other health sion remains uncertain. Like other herpesvirus conditions are also at risk for Kaposi’s sarcoma. strains, HHV-8 can remain dormant in the body for years without manifesting symptoms. A Symptoms and Diagnostic Path healthy IMMUNE SYSTEM seems to hold HHV-8 in The key symptom of Kaposi’s sarcoma is the pres- check, preventing it from causing disease. Pro- ence of its characteristic lesions, which are nodu- longed compromise of immune function, through lar and raised, in people with long-term conditions such as HIV/AIDS or through IMMUNOSUP- immunosuppression or who are HIV-positive. The PRESSIVE THERAPY such as occurs following ORGAN lesions start as small, raised areas and are most TRANSPLANTATION, allows HHV-8 to replicate (repro- common on the face, lower legs and feet, and gen- duce itself by taking over healthy cells) and cause itals, though can develop anywhere on the body. Kaposi’s sarcoma. They are usually darkly pigmented, often brown- AIDS-related Kaposi’s sarcoma Nearly all ish red or purple, and sometimes itch. As they Kaposi’s sarcoma in the United States occurs in grow, the lesions may block the flow of blood or people, predominantly men, who have AIDS. lymph, causing painful swelling. Lesions some- Doctors consider the appearance of Kaposi’s sar- times develop within the connective tissues of coma a defining sign that INFECTION with HIV internal organs such as the LUNGS, where they can (human immunodeficiency virus) has progressed cause difficulty BREATHING, or the intestines, where to the disease state of AIDS. The activation of both they can cause GASTROINTESTINAL BLEEDING and ILEUS HIV and HHV-8 may occur simultaneously, when (intestinal obstruction). both are present. Advances in treatment options The doctor can usually make a definitive diag- for HIV/AIDS, notably highly active antiretroviral nosis of Kaposi’s sarcoma on the basis of visible therapy (HAART), delay the progression of HIV to lesions and immune or HIV status, with biopsy of AIDS and consequently the appearance of Kaposi’s a representative lesion to confirm the diagnosis if sarcoma. About 6 percent of men with HIV/AIDS necessary. A chest X-ray can determine the pres- who receive HAART develop Kaposi’s sarcoma, ence of lesions in the LUNGS. Other imaging studies compared to 20 percent among those who do not. such as COMPUTED TOMOGRAPHY (CT) SCAN and

168 Kaposi’s sarcoma 169

ENDOSCOPY can determine whether there are nearly always in circumstances of depressed or lesions elsewhere in the body, such as in the gas- suppressed immune system function, skewing the trointestinal tract, when symptoms suggest or the conventional cancer-staging algorithms. The AIDS doctor suspects this is the case. Clinical Trials Group (ACTG) system is the most commonly used staging algorithm for Kaposi’s sar- Treatment Options and Outlook coma associated with AIDS or transplant-related Treatment depends to some extent on whether immunosuppression. The ACTG system assesses the Kaposi’s sarcoma is AIDS related or transplant three factors: related. In either form, methods to remove or reduce the lesions for improved comfort and • number of lesions appearance. Such methods may include • CD4 cell count, which represents immune sys- tem function • localized CHEMOTHERAPY (injecting a cytotoxic • systemic conditions that indicate compromised agent directly into the lesion) immune function • external-beam RADIATION THERAPY that narrowly targets the lesion Each factor receives a rating of zero (good) or one (poor), reflecting the likelihood for five-year • the topical retinoid preparation alitretinoin survival, a standard prognosis marker for cancer. (Panretin) applied to the lesion Kaposi’s sarcoma of the skin is seldom itself fatal, • surgery to reduce or excise (cut out) the lesion though the extent of its presence indicates the • liquid nitrogen or cryotherapy, which freezes immune system cannot protect the body from the lesion infection. Kaposi’s sarcoma of internal organs can be fatal. This cancer is not curable in AIDS or Systemic chemotherapy reduces lesions in active immunosuppressive therapy, so treatment recurrent, widespread, or systemic (involving aims to relieve symptoms. internal organs as well as the skin) disease in AIDS-related Kaposi’s sarcoma, though it is not Risk Factors and Preventive Measures usually an option for transplant-related Kaposi’s In the United States, HIV infection is the leading sarcoma because the immune system cannot with- risk factor for Kaposi’s sarcoma. Methods to stand the assault. Treatment for Kaposi’s sarcoma reduce exposure to HIV/AIDS also reduce the risk in people who have received organ transplants is for Kaposi’s sarcoma. Most AIDS-related Kaposi’s often a delicate balance between suppressing sarcoma occurs in men who have sex with men, enough immune function to stave off organ rejec- leading researchers to postulate that there is a tion and preserving enough immune response to route of sexual transmission for HHV-8. Safer sex fight INFECTION. Sometimes changing the immuno- practices are crucial. suppressive agent gives the immune system As a result of the growing availability and accept- enough of a boost to fight the lesions, causing ance of organ transplantation, the number of cases them to retreat or disappear. of Kaposi’s sarcoma among transplant recipients is steadily rising. The risk increases the longer the per- SYSTEMIC CHEMOTHERAPY AGENTS TO TREAT AIDS- son receives immunosuppressive therapy. Newer RELATED KAPOSI’S SARCOMA immunosuppressive agents more selectively target daunorubicin doxorubicin paclitaxel the immune functions responsible for organ rejec- (DaunoXome) (Doxil) (Taxol) tion, leaving other immune functions undisturbed. See also CANCER TREATMENT OPTIONS AND DECISIONS; For most cancers, doctors apply an algorithm of HIV/AIDS PREVENTION; SEXUAL HEALTH; SEXUALLY TRANS- symptoms and progression that helps determine MITTED DISEASE (STD) PREVENTION; SEXUALLY TRANSMIT- effective treatment options and prognosis (poten- TED DISEASES (STDS); STAGING AND GRADING OF CANCER; tial for improvement). Kaposi’s sarcoma occurs VIRUS. 170 The Integumentary System keloid An overgrowth of collagen after a wound structures, causing numerous hyperkeratosis- has finished HEALING. A keloid typically forms as related conditions from ACNE and atopic DERMATITIS folds or bunches of tissue. Keloids are fibrous, to PSORIASIS and SEBORRHEIC KERATOSIS. Squamous spongy in consistency, and often dark red. They cell carcinoma, a common type of SKIN CANCER, form most often on the earlobes, upper chest, and arises from keratinocytes. shoulders though can develop anywhere on the For further discussion of keratinocytes within body. Keloids are more common in people who the context of integumentary structure and func- have dark skin, and in people under age 50. tion please see the overview section “The Integu- Though keloids do not present any health prob- mentary System.” lems, they can become irritated from rubbing on See also ICHTYOSIS; MELANOCYTE; NAILS. clothing. A corticosteroid medication injected into the keloid often halts its growth and causes the keratoacanthoma A form of squamous cell car- existing excess tissue to recede. The dermatologist cinoma (SKIN CANCER) that appears suddenly and can surgically remove large keloids or keloids that grows rapidly, though has a low rate of METASTASIS recur. (spreading). Like other forms of skin CANCER, kera- See also ACROCHORDON; CORTICOSTEROID MEDICA- toacanthoma is the consequence of extensive sun TIONS; SCAR. exposure that manifests decades later. Researchers have identified a number of chromosomal abnor- keratinocyte The cell type that makes up most of malities that appear connected with keratoacan- the epidermis, also called a squamous cell. thoma, suggesting a strong genetic component or Keratinocytes originate in the first of the four layers familial predisposition (tendency of the cancer to of the epidermis, the stratum basale. Here they run in families). either replicate to generate new keratinocytes or Most keratoacanthomas develop in people over migrate upward. Migratory keratinocytes acquire age 50, though may occur at younger ages in peo- melanin from melanocytes. The keratinocytes carry ple who are taking IMMUNOSUPPRESSIVE THERAPY this pigment to the outer layers of the SKIN, where it (such as following ORGAN TRANSPLANTATION) or who appears as the skin’s normal color or causes the skin are IMMUNOCOMPROMISED. A keratoacanthoma to darken (as in a tan). At each of the epidermis’s lesion typically develops on skin surfaces that layers the keratinocytes become more compressed. receive or have received significant sun exposure Their internal structures break down, and the ker- and may initially appear to be a FURUNCLE (boil) or atin they contain causes them to harden. a cyst. The lesion often appears to heal, though At the stratum corneum, the outer layer of the seems to take a long time to do so (up to a year). epidermis, the keratinocytes overlap tightly, look- Though it appears that keratoacanthoma even- ing somewhat like irregular shingles when viewed tually resolves (heals) on its own, the risk that the under the microscope. At the culmination of this lesion could instead be squamous cell carcinoma journey, which takes about four weeks, the ker- or that the keratoacanthoma could metastasize atinocytes die and slough from the skin’s surface. causes dermatologists to recommend immediate The fingernails and toenails are much more tightly removal with microscopic examination to confirm compressed and hardened keratinocytes. They do the diagnosis. Keratoacanthomas tend to recur. not shed as does the stratum corneum but instead The dermatologist may recommend surgical grow forward over the front of the fingers and removal of the lesion or inject it with a toes at the rate of about one eighth inch every chemotherapeutic agent, either of which generally four to five weeks. is adequate treatment. Hyperkeratosis is a state in which the ker- See also ACTINIC KERATOSIS; CANCER TREATMENT atinocytes migrate through the epidermis far more OPTIONS AND DECISIONS; SKIN SELF-EXAMINATION. rapidly than normal, sometimes cutting the jour- ney to 10 days. This accelerated journey causes keratosis pilaris A very common condition in more keratinocytes than the body can shed to which the keratocytes produce excessive keratin, accumulate in the HAIR follicles and sebaceous clogging the HAIR follicles and forming small keratosis pilaris 171 bumps on the SKIN that resemble GOOSE BUMPS. The confirm any questionable presentations. Treat- bumps may be the same color as the skin or ment typically consists of measures to increase slightly reddened and create a texture like rough exfoliation, which clears accumulated cells from sandpaper on the skin’s surface. Occasionally the the hair follicles. Topical products containing bumps itch. Keratosis pilaris most often affects the alphahydroxy acids such as lactic acid are often lower arms and inner thighs, though can occur helpful. The dermatologist may prescribe a topical anywhere on the body, and is most common retinoid medication to treat resistant symptoms. among adolescents. Researchers have implicated Keratosis pilaris becomes increasingly uncommon number of gene mutations for keratosis pilaris. with age and generally resolves by the early 20s. The eruption and pattern of bumps present a See also ACNE; DERMATITIS; ICHTHYOSIS; KERATO- fairly conclusive diagnostic picture. A biopsy can CYTE; MUTATION; PITYRIASIS ROSACEA. L laser skin resurfacing A method for smoothing tation changes. As with all cosmetic procedures, it scars, ACNE pitting, WRINKLES, and other blemishes is important to fully understand what laser skin from the SKIN, primarily on the face, using a heat resurfacing can and cannot accomplish. Most peo- (usually carbon dioxide) laser. The laser focuses a ple who receive treatment from a qualified derma- high-intensity beam of light that the dermatologist tologist or plastic surgeon are satisfied with the moves across the surface of the skin, precisely tar- results. Some people may find that the new skin is geting the depth and skin areas for resurfacing. sensitive to soaps, cleansers, and makeup used This precision control allows the dermatologist to before the procedure. target some areas more deeply than others, The new skin is very vulnerable to damage accommodating such variations in the skin as fine from the sun during as well as after healing, wrinkles to moderate scars. Like CHEMICAL PEEL and requiring protective clothing, such as a wide- DERMABRASION, laser skin resurfacing achieves skin brimmed hat or scarf, and high sun protection fac- smoothing by destroying layers of cells. The new tor (SPF) sunscreen whenever sun exposure is skin that grows to replace the destroyed skin is necessary. The effects of laser skin resurfacing typ- tight and smooth. ically last several years, with wrinkles gradually The dermatologist performs laser skin resurfac- returning as a normal function of the aging ing as an AMBULATORY SURGERY procedure in a clinic, process. Alterations such as SCAR revision or office facility, or an ambulatory surgery facility, typ- removal are permanent. ically using local anesthetic to numb the skin and a See also AGING, INTEGUMENTARY CHANGES THAT sedative medication for relaxation and improved OCCUR WITH; BOTULINUM THERAPY; LASER SURGERY; SUN comfort. The length of time the procedure requires PROTECTION; SURGERY BENEFIT AND RISK ASSESSMENT. depends on what kinds of blemishes the dermatol- ogist is treating. The dermatologist may cover the lentigines Dark spots of varying size on the SKIN, treated surfaces with an ointment and bandages, also called freckles, liver spots, or age spots. which remain in place for one or two days. Lentigines develop as a result of continued sun After the procedure the treated skin surfaces exposure and indicate damage to the skin. A sin- are red, swollen, and tender or painful. After a gle spot is a lentigo. Lentigines are often wide- day or two the skin scabs or crusts, a normal stage spread on areas of skin that receive high sun in the HEALING process. The dermatologist removes exposure, such as the face and arms, sometimes any bandages at this time. As the skin heals the covering the entire surface of exposed skin. It is scabs fall away, typically in 10 to 14 days. The new important to examine the skin in areas of heavy skin is red and shiny, transitioning to normal pig- sun damage, such as those with many lentigines, mentation and texture over the following six to for signs of SKIN CANCER as most skin cancer arises eight weeks (though most of the redness subsides from such damage. in about three weeks). Full HEALING and noticeable Cosmetic products such as creams and lotions improvement take about six months. containing alphahydroxy acid, lactic acid, or other The risks of laser skin resurfacing are slight and mild fruit acids can lighten lentigines, functioning include excessive bleeding, INFECTION, and pigmen- as a mild CHEMICAL PEEL. These products have a 172 lichen simplex chronicus 173 mild bleaching action that reduces pigmentation planus is light in color and the scaling more dif- in the areas of application. Cosmetic procedures fuse, creating a lacelike pattern lighter in color such as dermatologist-performed chemical peel, than the surrounding mucosa. The distinctive hydroquinone application (a bleaching agent), or color and pattern of the RASH allow the dermatolo- LASER SURGERY can diminish or eliminate lentigines gist to make a quick diagnosis. The doctor may and other blemishes on the face. biopsy lichen planus lesions that appear in the See also SKIN SELF-EXAMINATION; SUNBURN; SUN mouth, as they resemble other conditions (such as PROTECTION. CANDIDIASIS and precancerous lesions) that require different treatment. lesion A generalized term for any abnormal growth. Lesions can result from injury, disease, or Treatment Options and Outlook surgery. Some lesions are malignant (cancerous) Outbreaks of lichen planus typically retreat without though most lesions are benign (noncancerous). medical intervention, though ANTIHISTAMINE MEDICA- Numerous types of lesions affect the SKIN. Their TIONS and topical CORTICOSTEROID MEDICATIONS can characteristics help define and diagnose disorders help relieve the itching. In severe cases, the derma- and conditions of the skin as well as systemic dis- tologist may prescribe oral corticosteroids such as orders that manifest dermatologic symptoms. prednisone to suppress the IMMUNE RESPONSE.An outbreak may last several weeks to several months COMMON TYPES OF SKIN LESIONS and typically flares in irregular recurrences over a ACHROCHORDON ANGIOMA basal cell period of years. Gentle, regular skin cleansing and BIRTHMARK BLISTER carcinoma moisturizing can help to manage and reduce symp- BULLA DERMATOFIBROSIS KELOID toms. LENTIGINES MACULE malignant NEVUS NODULE melanoma Risk Factors and Preventive Measures PAPILLOMA PAPULE plaque Dermatologists do not know what causes lichen PUSTULE SCALE SCAR planus, though believe it is an immune response squamous cell TELANGIECTASIS ulcer of some sort, either an autoimmune condition or carcinoma VESICLE WHEAL an immune response to a VIRUS, likely with a genetic predisposition. Lichen planus also occurs See also DERMATITIS; PLAQUE, SKIN; PSORIASIS; RASH; in HEPATITIS C INFECTION, is an early sign of trans- SKIN CANCER. plant organ rejection, and is a rare SIDE EFFECT of some medications such as long-term therapy with lice See PEDICULOSIS. the antimalarial medication quinidine and some NONSTEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS) lichen planus A common condition affecting the used for OSTEOARTHRITIS. Avoiding exposure to sub- SKIN that appears as small, shiny, reddish purple stances that can cause lichen planus, when identi- (violaceous) bumps that itch, sometimes intensely. fied, usually prevents future outbreaks though The bumps grow together in a scalelike pattern some people continue to experience cycles of the that resembles tree lichen. Lichen planus nearly condition for several years. always occurs in adults. See also AUTOIMMUNE DISORDERS; DERMATITIS; ICHTHYOSIS; LESION; LEUKOPLAKIA; LICHEN SIMPLEX Symptoms and Diagnostic Path CHRONICUS; PRURITUS; PSORIASIS. Lichen planus typically erupts on the inner sur- faces of the lower arms and wrists, along the shins lichen simplex chronicus A SKIN condition, and inner ankles, and along the lower back. Occa- sometimes called neurodermatitis, in which an sionally lichen planus appears on the scalp, where itchy RASH erupts in response to continued it can cause temporary or permanent ALOPECIA scratching of the skin. Over time, the involved (hair loss), or affects the fingernails and toenails, areas develop hyperkeratosis, an overgrowth of causing ridges and grooves. In the MOUTH, lichen keratinocytes that gives the areas a scaly, lichen- 174 The Integumentary System like appearance (plaques). Lichen simplex chroni- COSTEROID MEDICATIONS, which work together to cus sometimes develops in areas of the skin that mitigate the IMMUNE SYSTEM’s response to the per- have previously had irritation, such as from DER- sistent irritation scratching causes. Antihistamine MATITIS or abrasive injury, or frequently irritated, medications are especially helpful at bedtime, such as from clothing that rubs or constricts. Stress when many people find the itching most intense, and strong emotional responses exacerbate the as they tend to cause drowsiness. Some people rash and the itching. The condition appears more benefit from ANTIANXIETY MEDICATIONS. Methods common in people who have DEPRESSION or anxi- such as VISUALIZATION, BIOFEEDBACK, and ACUPUNC- ety, hence the former term, neurodermatitis, for TURE may help. Mild to moderate lichen simplex the condition. Most often, however, there is no chronicus generally heals without residual effects, clear cause for the condition. though more severe manifestations may leave scarring and altered pigmentation (either lighter Symptoms and Diagnostic Path or darker patches of skin in the sites of the healed The rash of lichen simplex chronicus begins with plaques). small reddened areas (macules) that itch, com- monly forming on the neck and the inner surfaces Risk Factors and Preventive Measures of the arms and legs. Most people who have The causes of lichen simplex chronicus remain lichen simplex chronicus describe the itching as elusive. Dermatologists disagree on whether the intense, such that they are unable to stop scratch- rash or the itching appears first, though the end ing. With scratching, the rash becomes more result is that the rash itches and continued extensive. Many people find the itching more pro- scratching perpetuates the rash. The most impor- nounced at night before sleep, creating difficulty tant factor is to avoid scratching, as persistent falling asleep or staying asleep. The dermatologist scratching causes other damage to the skin that typically diagnoses lichen simplex chronicus on increases the risk for INFECTION and scarring. In the presentation of these symptoms, though may many people, episodes follow stressful experi- choose to biopsy questionable lesions to confirm ences. Stress management techniques and relax- the diagnosis. ation methods provide other means for diffusing the physiologic effects of stress. Treatment Options and Outlook See also GENERALIZED ANXIETY DISORDER (GAD); Treatment targets relieving the symptoms, prima- ICHTHYOSIS; KERATINOCYTE; LESION; LICHEN PLANUS; rily the itching. The dermatologist may prescribe MACULE; PLAQUE, SKIN; PRURITUS; PSORIASIS; SCAR; oral ANTIHISTAMINE MEDICATIONS and topical CORTI- STRESS AND STRESS MANAGEMENT. M

macule A small SKIN LESION that is flat, smooth, synthesizes from dietary proteins such as meats and discolored. Macules are common and may and which the melanocytes store, into dopa- appear as the presenting symptom for numerous quinone. The dopaquinone forms the pigments dermatologic and other health conditions. Often eumelanin and pheomelanin, which collectively the only symptom they present themselves is dis- comprise mel-anin. coloration, though some macules itch or hurt. The Exposure to ultraviolet light, notably sunlight, discoloration may be hyperpigmentation (darker initiates a sequence of hormonal and chemical than the surrounding skin) or hypopigmentation events that stimulate melanocytes to produce (lighter than the surrounding skin). A macule is melanin (melanogenesis): the same texture and thickness as the adjacent skin and generally no larger than two inches in 1. Sunlight (or other ultraviolet light exposure) length, width, or diameter. The most common damages the cells of the skin. The damage acti- macule is a lentigo, or freckle. vates the natural repair mechanisms within the See also BIRTHMARK; LENTIGINES; NODULE; PAPULE; cells, which releases chemicals into the blood- PUSTULE; VITILIGO. stream that travel to the PITUITARY GLAND. 2. In response the pituitary gland releases malignant melanoma See SKIN CANCER. melanocyte-stimulating hormone (MSH), to bind with melanocytes. melanocyte A type of cell prominent in the der- 3. Melanocytes pass packets of melanin molecules mis (middle layer of the SKIN) that produces to the keratocytes, which carry them to the melanin, the pigment that gives color to the skin outer layer of the epidermis as they migrate as well as protects the skin from ultraviolet light upward. damage. There are two types of melanin: the dark brown pigment eumelanin and the red/yellow The resulting skin color depends on the mix of pigment pheomelanin. The skin contains the same eumelanin and pheomelanin the melanin con- number of melanocytes no matter what the indi- tains. The melanin in light skin contains more vidual’s natural skin color. The melanocytes in pheomelanin than eumelanin. In darker skin the darker skin are more active than those in lighter balance tips the other way with the melanin in skin. The eyes and HAIR also contain melanocytes. dark skin containing more eumelanin than pheomelanin. In the epidermis, melanin protects Melanogenesis the skin from damage by absorbing ultraviolet The exclusive role of melanocytes is to produce light. The darker the skin, the less ultraviolet light melanin (melanogenesis), a somewhat sequential penetrates the epidermis. In general, it takes about process. To prepare for melanogenesis, the body a week of regular sun exposure to generate a tan produces the enzyme tyrosinase. Genetic encoding adequate to begin protecting the skin from further regulates this process. Tyrosinase initiates conver- sun damage, though the tan itself signals sun sion of the amino acid tyrosine, which the body damage.

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Dysfunctions of Melanocytes Mohs’ micrographic surgery A specialized tech- There are three significant dysfunctions of mela- nique for removing certain skin cancers such as nocytes: basal cell carcinomas and squamous cell carcino- mas. In an outpatient OPERATION (AMBULATORY SUR- •ALBINISM is a deficit or absence of pigmentation GERY) with local anesthetic and a sedative for (hypopigmentation) caused by a MUTATION in relaxation if necessary, the dermatologist removes the genetic encoding for tyrosinase. The body one thin layer of the tumor at a time and exam- may produce little or none of this enzyme, ines each specially stained layer under the micro- reducing or completely blocking melanogene- scope. The surgery continues until the tissue sis. The dermatologic consequence is extremely sample shows a one- to two-millimeter margin of light-colored skin that cannot protect itself healthy tissue on all borders, ensuring that the from ultraviolet light damage. dermatologist removes all of the malignancy. •VITILIGO is a hypopigmentation disorder of Because Mohs’ micrographic surgery is so precise autoimmune origin in which the melanocytes it removes only the malignancy, sparing as much in areas of the skin die, leaving the skin with- surrounding tissue as possible. out pigmentation. By comparison, conventional excision removes the tumor and what the surgeon believes is a rea- • Malignant melanoma is a serious type of SKIN sonable amount of surrounding tissue to provide CANCER that arises from melanocytes. clean margins, which can result in removing con- siderably more tissue than just the malignancy. A For further discussion of melanocytes within pathologist later examines frozen sections of the the context of integumentary structure and func- tissue to confirm the margins. With conventional tion, please see the overview section, “The Integu- excision there is a change that the margins could mentary System”. be positive (contain cancer cells) and the surgeon See also AMINO ACIDS; KERATINOCYTE; PHENYLKE- would have to do another operation to remove TONURIA (PKU). more tissue. Dermatologists use Mohs’ micrographic surgery melasma See CHLOASMA. when the SKIN CANCER is on the face, nose, eyelids, or around the mouth, or if it is a larger, more miliaria Small bumps that form on the SKIN in aggressive cancer on the body. The procedure may environmental conditions of high heat and take several hours altogether to complete, humidity, when the body produces much sweat depending on how many layers of tissue the der- that cannot evaporate and instead pools on the matologist must remove to get clean margins. surface of the skin. The bumps may be red (mil- Many cancers removed using Mohs’ micrographic iaria rubra) or clear and filled with fluid (miliaria surgery heal with minimal scarring. The dermatol- crystallina). Clothing may further inhibit sweat ogist performing the surgery usually repairs any evaporation. The pooling creates irritation and residual defect as dermatologists also perform INFLAMMATION that obstructs the sweat glands. reconstructive surgery. Mohs’ micrographic sur- Most miliaria, commonly called heat RASH, gery has an overall cure rate of 95 percent and up improves with self-care to cool the body, which to 99 percent for certain kinds of malignant causes the SWEAT GLANDS to decrease production. lesions, the highest for all current forms of treat- The skin bumps generally go away in three to five ment for these two types of skin cancer. Frederic days. Newborns are particularly susceptible to E. Mohs, M.D. (1910–2002), discovered the tech- miliaria in the first week or two of life. Miliaria nique while a medical student in the 1930s. also sometimes occurs in people who have high See also CANCER TREATMENT OPTIONS AND DECI- fevers. SIONS; LESION; SURGERY BENEFIT AND RISK ASSESSMENT. See also HEAT EXHAUSTION; HEAT STROKE; HYPER- THERMIA. mole See NEVUS. N–O nails The hardened epidermal layer covering the a week. The cells the matrix produces today will top surfaces of the tips of the fingers and toes. Nails reach the end of the finger in about six months. are made of cornified, compacted SKIN cells (ker- Like the skin, the nails provide insights into the atinocytes) that grow from the base of the nail overall health situation of an individual. Certain (matrix or nail-bed root). Though the cells of the changes in the nails signal specific health condi- matrix are alive, the cells that make up the nails are tions. Such characteristics include dead. New cell growth from the matrix pushes the nail outward across the tip of the finger or toe. In • banding: stripes of dark or light across the adults the fingernails grow about two tenths inch in width of the nail bed, visible through the nail

HEALTH IMPLICATIONS OF NAIL CHARACTERISTICS Nail Characteristic Possible Health Implications Beau’s lines serious injury or illness that disrupts nail growth clubbing chronic pulmonary conditions, HEART FAILURE, low blood oxygen levels dark band at tops of nails, bottoms of nails normal color age, CANCER, congestive heart failure, DIABETES, CIRRHOSIS, (Terry’s nails) HYPERTHYROIDISM koilonychia iron-deficiency ANEMIA leukonychia arsenic poisoning, mineral deficiency, trauma to the nail matrix onycholysis thyroid disease, fungal INFECTION, PSORIASIS, adverse DRUG reaction

PETECHIAE (pinpoint hemorrhages) ENDOCARDITIS, THROMBOCYTOPENIA, SYSTEMIC LUPUS ERYTHEMATOSUS (SLE) stippling psoriasis, ALOPECIA AREATA, injury to the nail white band at the bottoms of nails, tops of nails normal UREMIA, KIDNEY failure color (half-and-half nails) yellow nail syndrome (yellow-green discoloration consistent chronic pulmonary disorders such as BRONCHITIS and EMPHYSEMA, through all nails) NICOTINE staining

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• Beau’s lines: indentations in the nail surface populate the substantia nigra, for example, a that extend across the width of all the nails at structure of the midbrain. The pigmented cells of about the same position on each substantia nigra produce dopamine, a NEUROTRANS- • clubbing: end of the finger or toe becomes MITTER essential for the brain’s coordination of enlarged and the angle between the nail fold MUSCLE function throughout the body. However, and the nail plate exceeds 180 degrees melanocytes in other parts of the nervous system can generate overgrowths—nevi—just as they do • discoloration: may be widespread throughout on the skin. Such nevi cause pressure as they the nail or occur in spots or streaks grow, resulting in neurologic symptoms. • koilonychia: nails soften and the edges rise, Acquired nevi begin to appear during child- leaving a large spoonlike indentation in the hood in most people, with the most intense activ- center of the nail ity occurring in middle adulthood (ages 30 to 50). • leukonychia: white spots or streaks in the nail Though sun exposure plays a role in their devel- • onycholysis: separation of the nail from the nail opment, genetic encoding seems to regulate char- bed acteristics such as size, color, shape, and numbers. In the typical structure of the dermis, the layer of • PETECHIAE: red or dark spots beneath the nail skin where melanocytes reside in greatest concen- • stippling: the formation of small pits in the sur- tration, melanocytes are frequent but are not in face of the nail contact with each other. Researchers believe this distribution pattern results from “contact inhibi- For further discussion of the nails within the tion” genetic encoding. A nevus can form when context of integumentary structure and function the contact inhibition lapses, allowing the please see the overview section “The Integumen- melanocytes to drift into contact with one tary System.” another. Sometimes nevi appear after extensive See also INGROWN NAIL; KERATINOCYTE; ONYCHOMY- injury to the skin, such as occurs with conditions COSIS. that cause widespread blistering. This suggests that such injuries disrupt contact inhibition in some neurodermatitis See LICHEN SIMPLEX CHRONICUS. way, though the mechanisms through which this occurs remain unknown. nevus A discolored LESION on the SKIN. Nevi are very common and may take various shapes and A nevus should have regular borders, colors. Most nevi contain primarily melanocytes consistent coloration, and a symmetri- and may differ in texture from the surrounding cal (balanced) appearance. A doctor skin. A nevus may be smooth, distinguishable should evaluate a nevus that has or only by its color, or rough and segmented. Some develops irregular borders, variable col- nevi contain coarse HAIR. The most common form oration, or an asymmetrical appearance of nevus is a mole, a small lesion that can be as these characteristics may indicate a smooth or raised and is usually darker in color nevus that is becoming cancerous. than the surrounding skin. A nevus may be con- genital (present at birth) or acquired (develops at Though nevi are themselves benign (non- any point in the lifespan after birth). Nearly cancerous), they can become cancerous over time everyone has some nevi by early adulthood. and particularly with repeated, unprotected sun Giant congenital nevus, a rare presentation of exposure. Congenital nevi in particular carry an congenital nevus, may cover a large area of the increased risk for malignant melanoma, a serious skin’s surface. In another uncommon genetic dis- type of SKIN CANCER. Most often, the only health order, neurocutaneous melanosis, nevi develop concerns with nevi are the increased risk for within the structures of the BRAIN and SPINAL CORD. malignancy and cosmetic appearance. The derma- The presence of melanocytes in some NERVOUS SYS- tologist may choose to remove nevi that receive TEM tissue is normal and functional. Melanocytes frequent irritation, such as those that form in onychomycosis 179 areas where clothing rubs them. The resulting discolor, fragment, and peel or crack. Though SCAR may require PLASTIC SURGERY for the desired some people experience itching, PAIN, or other dis- cosmetic appearance, depending on the size, comfort with onychomycosis, most people seek nature, and location of the nevus. Small nevi heal medical care because of the nail’s appearance. without noticeable scarring. Nevi do tend to recur Onychomycosis affects the structure and function after removal. of the nail, however. Onychomycosis affecting See also GENETIC DISORDERS; MELANOCYTE; PARKIN- multiple toenails can interfere with proper walk- SON’S DISEASE; SKIN SELF-EXAMINATION; VITILIGO. ing, and onychomycosis of the fingernails may reduce gripping ability and the ability to perform nodule A small cluster of cells that arises from tasks such as typing or keyboarding. The doctor the subcutaneous or dermis layer of the SKIN and often can make the diagnosis based on the appear- forms a swelling. Nodules are solid and distinct ance of the NAILS, though may choose to examine from the surrounding tissue. Most skin nodules tissue samples under the microscope to confirm arise from causes other than dermatologic, such as the presence of the infective FUNGUS. neurofibroma and LIPOMA. Nodules may exist in Eradication of the fungus often requires oral other parts of the body, typically as symptoms of antifungal medication in combination with topical systemic disease. antifungal medication. Onychomycosis can be a See also MACULE; PAPULE; PUSTULE. stubborn infection, making several courses of treatment necessary. Early diagnosis and treat- onychomycosis A common fungal INFECTION, ment affords the most successful results. typically CANDIDIASIS or TINEA, of the fingernail or See also ANTIFUNGAL MEDICATIONS; INGROWN NAIL; toenail. The infection causes the nail to thicken, PARONYCHIA; PSORIASIS. P papilloma A general classification of tumors toes can fester, allowing infection to creep under arising from the epidermis (outer layer of the SKIN) the nail. as well as the epithelial layer of the mucous mem- Paronychia can be acute (come on suddenly) or branes. Warts, HUMAN PAPILLOMAVIRUS (HPV) lesions chronic (persist or recur over a period of time). (also called condylomata or genital warts), and Acute paronychia is generally painful and pustular POLYPS are papillomas. Though papillomas are non- (produces pus). Staphylococcus aureus, a strain of cancerous (benign), some types of papillomas, BACTERIA that normally lives on the skin, is the notably intestinal polyps, are the foundation for usual cause of the infection. Less commonly, a certain cancers. Doctors generally remove polyps strain of Streptococcus or Pseudomonas (bacteria), or and treat HPV infections and lesions because these the FUNGUS (yeast) Candida albicans, may be the are among the papillomas that can become can- culprit. cerous. Many people prefer to have common Symptoms of paronychia include redness, warts removed for cosmetic purposes. Irritation swelling, PAIN, and occasionally bleeding or pus dis- such as from clothing that rubs or frequent charge. The doctor can diagnosis paronychia based trauma can cause papillomas to bleed. on the symptoms and the history of their develop- See also ACROCHORDON; ADENOCARCINOMA; ADE- ment and occurrence. Treatment may include NOMA-TO-CARCINOMA TRANSITION; COLORECTAL CANCER; INFECTION; LESION; WART. • warm soaks three to four times a day, keeping the affected finger or toe dry at all other times A small, raised bump arising from the papule • topical antibiotic or ANTIFUNGAL MEDICATION epidermis that is distinctive and firm to the touch. Papules may be discolored or the same color as the • oral antibiotic or antifungal medication surrounding SKIN. The presence of papules is a symptom of many dermatologic and other health Occasionally the doctor may need to lance conditions. Papules that cluster together form a (make a sterile incision) the infected area to skin plaque, usually taking on a hardened, flaky release the pus collected within. The paronychia appearance. generally heals within 7 to 10 days, though may See also MACULE; NODULE; PLAQUE, SKIN; PUSTULE. recur if related to behaviors or exposures that con- tinue. Untreated paronychia becomes very painful paronychia INFLAMMATION and INFECTION of the and may cause infection to spread into deeper tis- SKIN that surrounds the NAILS. Paronychia com- sues, with the potential for permanent damage to monly occurs in people who bite their fingernails the nail as well as to tendons, ligaments, MUSCLE, or the skin around them or who have frequent and BONE. cuts around their fingernails. Paronychia is com- See also CELLULITIS; INGROWN NAIL; OSTEOMYELITIS; mon in children who suck their thumbs or fingers. WHITLOW. Paronychia of a toenail may accompany an ingrown toenail. Splinters, INSECT BITES AND STINGS, pediculosis Infestation with lice, parasites that and other injuries around the tips of the fingers or live on the SKIN and feed by sucking BLOOD through 180 pediculosis 181

CHARACTERISTICS OF PARONYCHIA Acute Chronic symptoms PAIN, redness, and swelling tenderness and swelling of the skin around the nail SKIN around the nail appears tight and bright redness and increased discomfort with prolonged red exposure to water (such as washing dishes) may have pus ongoing for longer than four to six weeks precipitating trauma (sliver, pulled hangnail, repeated exposure to water, chemicals, other irritants biting the nail or skin) discolored or thick nail on the affected finger or toe sudden onset separation of the cuticle from the nail bed infective agent Staphylococcus aureus Candida albicans Streptococcus Pseudomonas medication oral ANTIBIOTIC MEDICATIONS such as topical antifungal medication such as miconazole clindamycin, cephalexin, or amoxicillin and oral antifungal medication such as ketoconazole or clavulanic acid fluconazole

small punctures they make through the skin. Lice are often a factor with body lice infestation. Poor attach their eggs, called nits, to HAIR shafts. Of the PERSONAL HYGIENE such as infrequent bathing can numerous species of lice, three afflict humans: allow secondary problems such as INFECTION to develop. • Pediculus humanus capitis, which infests the scalp Symptoms and Diagnostic Path • Pediculus humanus corporis, which infests the The most common symptom of pediculosis is itch- body ing, which is often particularly intense at night • Pediculus pubis, which infests the pubic region when the lice feed. The saliva of the lice contains enzymes to delay coagulation (blood clotting) which irritate the skin. The bites leave reddened Each species has unique claw and MOUTH struc- tures that allow survival in the particular region of papules (raised bumps) that continue to itch. the body, and each species can infest only the Finding nits (eggs attached to hair shafts) is the body region for which it is adapted. However, conclusive diagnostic marker. Nits are difficult to infestation with two or more species is common. remove, which helps distinguish them from other Pediculosis refers collectively to infestation with matter that might collect on the skin or hair, as any species of lice, and affects around 12 million well as from conditions such as seborrheic DER- Americans each year. MATITIS and common DANDRUFF. Examination with Pediculosis spreads easily through direct and fluorescence (Woods lamp) causes the lice and nits indirect contact, and is so common among school- to glow yellow or green. age children that schools routinely screen for its Treatment Options and Outlook presence. Crowded environments, such as schools Treatment for head or pubic infestation combines and dormitories, allow close contact between peo- removing the nits with a fine-tooth comb (nit ple, permitting the lice to spread from one person comb) and shampooing or washing with an insec- to another. Pediculosis may be present for as long ticide-based product such as permethrin (Nix) or as two months before causing appreciable symp- malathion (Ovid). Multiple treatments about a toms, increasing the potential for extending infes- week apart for a month, or until no nits are pres- tation. Head and pubic lice and nits resist the most ent, are necessary to cover the lifespan of the scrupulous cleansing. Infrequent clothing changes louse, which is about 35 days. It is important to 182 The Integumentary System carefully follow the label directions for the prod- and face though sometimes involve the back uct and to leave the product on the hair or skin and chest for the instructed length of time. Most treatment • paraneoplastic pemphigus, which occurs only regimens include combing the hair with a nit secondarily to CANCER and can involve the comb after shampooing. All individuals in the mucous membrane lining the ESOPHAGUS and household should receive treatment. airways (TRACHEA and bronchi) It is also necessary to wash clothing and bed linens in hot water (130ºF or more) for at least five minutes, and placing stuffed toys in sealed Pemphigus occurs when antibodies the IMMUNE plastic bags for two weeks. The hot water wash SYSTEM produces attack and destroy certain pro- kills any lice or nits, and the plastic bag method teins on the surface of epidermal keratinocytes, deprives any lice or nits that hatch of nourish- the skin cells that make up the epidermis, causing ment. Because body lice live on the clothing them to separate from one another. The proteins rather than the skin, washing the clothing in hot are like glues that hold the keratinocytes together. water is usually adequate. Dermatologists do not know what causes pemphi- gus to develop as an autoimmune process, though Risk Factors and Preventive Measures occasionally it occurs as an ADVERSE REACTION to Most pediculosis leaves no residual health conse- certain medications, notably penicillamine (taken quences, although secondary infections may to treat severe RHEUMATOID ARTHRITIS) and car- develop with excessive scratching. However, sex- bidopa/levodopa (taken to treat PARKINSON’S DIS- ual contact generally transmits pubic pediculosis, EASE). which raises concern for SEXUALLY TRANSMITTED DIS- EASES (STDS). Body lice (P. humanus corporis) can Symptoms and Diagnostic Path carry serious bacterial diseases including typhus. The primary symptom of pemphigus is the appear- See also PAPULE; PARASITE; PUBLIC HEALTH CONCERNS ance of bullae that start as small blisters. In early OF INFECTIOUS DISEASES; SCABIES; SEXUALLY TRANSMIT- outbreaks the blisters may rupture and heal with- TED DISEASE (STD) PREVENTION. out taking the characteristic bulla form. As out- breaks become more frequent and progressive, pemphigus An autoimmune disorder in which however, the blisters enlarge over several days to large, painful bullae (blisters) form on the SKIN and a week. In the early stages of the disorder’s mani- mucous membranes. The bullae develop within festation, the pattern and appearance of bullae the epidermis, the skin’s uppermost layer, giving may be similar to other autoimmune symptoms, them a very thin surface. They rupture and tear notably the sores that can appear with HIV/AIDS. easily, exposing the skin to INFECTION and interfer- Biopsy of the lesions can help to rule out other ing with the skin’s ability to carry out its numer- causes. ous functions. The ruptured bullae form crusts The location and extent of the bullae character- while they heal, though typically heal without izes the form of pemphigus. Pemphigus vulgaris scarring. Some forms of pemphigus can cover typically begins with blisters in the mouth, with large portions of the skin’s surface are potentially outbreaks quickly following on other skin surfaces fatal. There are three main forms of pemphigus: as well as the mucous membranes lining the NOSE and the URETHRA. The bullae of paraneoplastic • pemphigus vulgaris, the most common form in pemphigus, which only occurs in conjunction which bullae develop in the MOUTH and under with cancer, also originate in the mouth though the eyelids as well as on the skin surfaces of the quickly involve the esophagus as well as the skin. face, neck, chest, axillae (underarms), and Pemphigus foliaceus bullae are smaller and remain groin confined primarily to the head (scalp and face), • pemphigus foliaceus, the mildest form in which and do not involve the mouth or other mucous bullae develop mostly on the skin of the scalp membranes. photosensitivity 183

Treatment Options and Outlook See also ANTIBODY; BLISTER; BULLA; BULLOUS PEM- Treatment targets relief of symptoms during out- PHIGOID; KERATINOCYTE; LESION; MUTATION. breaks and mitigation of future outbreaks to the extent possible. Treatment varies with the form petechiae Smooth, reddened, pinpoint lesions and severity of pemphigus, though typically that result from microscopic bleeding under the includes oral or injected CORTICOSTEROID MEDICA- surface of the SKIN. Petechiae most commonly TIONS along with oral ANALGESIC MEDICATIONS for appear on the lower legs though can appear any- PAIN relief and ANTIBIOTIC MEDICATIONS to treat infec- where on the body. The presence of petechiae is a tion when necessary. Severe outbreaks may symptom that signals an underlying health condi- require IMMUNOSUPPRESSIVE MEDICATIONS to subdue tion that causes a low platelet count such as the IMMUNE RESPONSE, or PLASMAPHERESIS, a therapy THROMBOCYTOPENIA, LEUKEMIA, MONONUCLEOSIS, or that cleanses the blood’s serum of antibodies. SYSTEMIC LUPUS ERYTHEMATOSUS (SLE). Platelets are Cytotoxic drugs such as those used in CHEMOTHER- the body’s first-line response in the COAGULATION APY also improve symptoms in some people with process, clumping together (aggregating) to slow severe outbreaks. bleeding. Antiplatelet therapy such as ASPIRIN THER- The most serious complication of pemphigus APY, often prescribed for people at risk for HEART itself is loss of the skin’s ability to protect the body ATTACK or STROKE, intentionally blocks the actions from bacterial invasion, resulting in widespread of platelets and may also result in petechiae. The skin or systemic infection. However, pemphigus is appearance of petechiae, which often is sudden, a chronic condition that requires ongoing medica- requires prompt evaluation from a doctor. tion therapy. For many people who have pemphi- See also ECCHYMOSIS; LESION; MONONUCLEOSIS, gus vulgaris, the more common and more severe INFECTIOUS; PLATELET; PURPURA. form, the most significant complications arise from the long-term use of the medications necessary to photosensitivity A heightened reaction to sun- control outbreaks. These medications all have seri- light or other ultraviolet light that results in a RASH ous side effects and adverse consequences for or SUNBURN at much lower or shorter exposure other body structures and functions. Pemphigus than would ordinarily cause sunburn. Photosensi- that appears as an adverse DRUG reaction typically tivity may develop as a reaction to a medication, ends when the person stops taking the medica- such as the antibiotic medication tetracycline or tion. Paraneoplastic pemphigus improves with the herbal antidepressant remedy ST. JOHN’S WORT treatment for the underlying cancer, though may (hypericum), or as a symptom of an underlying cause life-threatening pulmonary complications health condition such as SYSTEMIC LUPUS ERYTHE- when it affects the airways. MATOSUS (SLE) or ALBINISM. Photosensitivity may manifest as a red, splotchy rash on areas of SKIN Risk Factors and Preventive Measures exposed to the sun or as a full-fledged sunburn. Because doctors do not know the mechanisms Rarely, an individual may have an allergic reac- that set pemphigus in motion, there are no identi- tion to ultraviolet light that causes the fairly fied risk factors. The condition tends to first mani- immediate eruption of URTICARIA (hives) with sun fest in people who are age 40 or older, though can exposure. occur at any age. Researchers suspect GENE muta- The dermatologist can diagnose photosensitiv- tions underlie pemphigus as they do other AUTOIM- ity based on its presentation and a history of MUNE DISORDERS, though have not yet been able to recent sun exposure. Treatment may include topi- identify them. Early diagnosis and aggressive cal or oral ANTIHISTAMINE MEDICATIONS if the rash treatment are key to mitigating symptoms and itches (although topical antihistamines can them- outbreaks, improving QUALITY OF LIFE as well as selves increase sun sensitivity). Topical CORTICOSTE- helping preserve other structures and functions. ROID MEDICATIONS often help reduce INFLAMMATION People who have milder forms of pemphigus may from widespread sunburn. However, the most go extended periods without symptoms. effective treatment for photosensitivity is preven- 184 The Integumentary System tion. Dermatologists recommend people who are phototherapy, and narrowband, which employs a photosensitive: narrower width of ultraviolet light. Narrowband UVB phototherapy is often more effective for • wear clothing that covers the arms, legs, head, treating psoriasis, though has a higher risk of sun- face, and neck when going outdoors, even burn than broadband UVB phototherapy. For UVB when the day is cloudy phototherapy treatments, the person stands inside • liberally apply sunscreen at least 30 minutes a small room called a light box with the areas of before going outdoors (many dermatologists skin exposed that are to receive treatment. Other recommend applying sunscreen after getting skin surfaces remain clothed or covered, though out of the shower in the morning so the skin treatment may be appropriate for nearly the entire can absorb it) and frequently while outdoors body. • avoid exposure during the sun’s most intense PUVA phototherapy PUVA lightwaves provides periods, typically between 10 a.m. and 4 p.m. a stronger, more focused therapeutic effect. UVA in most regions of the United States lightwaves are more intense than UVB lightwaves. Psoralen is a photosensitive substance taken orally See also ANTIBIOTIC MEDICATIONS; PHOTOPHOBIA; as a pill or applied as a lotion to lesions and PORPHYRIA. desired skin surfaces. Short exposures to UVA lightwaves activate the psoralen, which intensifies phototherapy Treatment with ultraviolet light, the effect. This combination reduces the risk for which suppresses the action of immune cells in complications such as sunburn during treatment. the SKIN (T-CELLS). Ultraviolet light also slows the However, the skin remains photosensitive for up growth rate of keratinocytes, the cells that make to 36 hours after treatment, requiring the person up much of the dermis and nearly all of the epi- to avoid all sun exposure for 12 to 36 hours fol- dermis, helping reduce symptoms such as plaque lowing a PUVA phototherapy session. The individ- formation and scaling. Phototherapy is effective ual must also wear sunglasses after taking oral for numerous chronic dermatologic conditions, psoralen because the psoralen tends to accumulate notably PSORIASIS, VITILIGO, and atopic DERMATITIS. in the retinal tissues of the eyes. Some people Many people require therapeutic phototherapy to have an ADVERSE REACTION to psoralen including bring symptoms under control, with ongoing NAUSEA, vomiting, itching (PRURITUS), and height- maintenance treatments to help prevent recurrent ened sensitivity to sun exposure even after PUVA outbreaks or to continue subduing the IMMUNE phototherapy ends. RESPONSE. With appropriate protection to prevent Excimer laser phototherapy Another type of ultraviolet damage to the eyes and skin, pho- phototherapy is the excimer laser, which emits totherapy has few short-term side effects. Ques- high-intensity UVB lightwaves that the dermatol- tions remain, however, about long-term ogist focuses on specific lesions or defined areas of consequences such as the same problems that the skin’s surface. Such laser phototherapy allows accompany extended sun exposure (notably SKIN targeted treatment and limits the risk for sunburn, CANCER). Dermatologists use three types of pho- though targeted lesions often acquire deeper pig- totherapy: ultraviolet B (UVB) phototherapy, pso- mentation than the surrounding skin and may ralen plus ultraviolet A (PUVA) phototherapy, and SCAR after HEALING. Often the hyperpigmentation excimer laser phototherapy. fades over time. Dermatologists generally reserve UVB phototherapy UVB lightwaves are less excimer laser phototherapy for conditions that do intense than ultraviolet A (UVA) lightwaves, not respond to other treatments. achieving a therapeutic benefit with low risk of See also KERATINOCYTE; LESION; NEONATAL JAUNDICE. sunburn and other complications. UVB photother- apy was the first therapeutic application of ultravi- piercings Skin piercings for cosmetic purposes olet light and remains the most common one in have become popular in the United States, espe- use today. Dermatologists use two forms of UVB cially among young people. Most people who phototherapy: broadband, the conventional UVB have piercings experience minor complications at pilonidal disease 185 some point. Wearing jewelry in the piercing, because the mouth has a rich blood supply as well which is necessary to maintain the piercing, also as an abundance of bacteria. establishes circumstances for HYPERSENSITIVITY REAC- TION and INFECTION. Long-term complications of Deformity piercings can include deformity of the tissues at Small piercings (16 gauge and smaller) will heal the piercing site and the risk for systemic infection closed without scarring when the person no such as HEPATITIS. longer wears jewelry in the piercing to keep it open. Larger piercings (12 gauge and larger) may Hypersensitivity Response not heal closed, or may close with puckering of Contact DERMATITIS, often as a hypersensitivity the tissue. Large-gauge piercings may stretch the reaction to the nickel in stainless steel, is the most tissues, such as the earlobes or lips, causing per- common dermatologic complication of piercings. manent enlargement. Infections, particularly of In contact dermatitis, the skin at the piercing loca- the ear cartilage, can destroy tissue, requiring tion becomes red (erythema) and inflamed. It may PLASTIC SURGERY to restore the appearance and itch or hurt. The piercing may swell, causing the sometimes the function of the tissue. Piercings of tissue to close around the jewelry. Removing the the PENIS can damage or destroy erectile tissue, jewelry and cleansing the site with an antiseptic nerves, or the URETHRA. Clitoral piercing can dam- solution made for this purpose helps soothe the age nerves and cause structural damage to the CLI- irritated tissues and reduce INFLAMMATION. TORIS and surrounding labia, particularly as a consequence of infection. Infection Infection is a common problem that may develop Preventing Piercing Complications as a complication of contact dermatitis, as a result Basic hygienic methods can prevent most piercing of contaminated piercing needles and devices, or complications. These methods include as a consequence of improper cleansing after piercing. Contamination is a significant risk with • having piercings done by reputable, experi- self-piercing. Early detection and treatment is enced professionals who use only disposable important to prevent the infection from invading needles and equipment deeper tissues. EAR CARTILAGE piercings are particu- • daily cleansing of piercing sites, such as wash- larly vulnerable to infection as well as resistant to ing with gentle soap and water during regular treatment for infection, as the BLOOD supply to the showering or bathing, or using a commercially area is sparse. Navel and genital piercings also are available antiseptic cleansing solution for pierc- vulnerable to infection as a result of irritation ing sites from clothing and moisture. • frequently changing and cleaning piercing jew- Piercing jewelry made of plastic, wood, BONE, elry and other permeable materials can harbor BACTE- RIA. Minor infections generally improve with topi- • not sharing piercing jewelry cal ANTIBIOTIC MEDICATIONS. More extensive • wearing piercing jewelry made of impermeable infections require a doctor’s evaluation and often materials such as metals require more involved treatment such as oral antibiotic medications and antiseptic cleansing of See also TATTOOS; VALVULAR HEART DISEASE. the piercing site. Systemic infection such as hepatitis, and less pilonidal disease A chronic condition in which commonly HIV/AIDS, is a significant risk when HAIR-filled cysts form at the base of the spine. The reusing or sharing piercing jewelry and needles. cysts typically originate when the SKIN closes to The hepatitis VIRUS can live outside the human form saclike structures with hair trapped inside. body for extended periods of time. Piercings in The sac fills with fluid, cells, and other debris. and around the MOUTH carry the risk for bacterial Often there are indentations or pits over the tops infection that can involve the HEART valves of the cysts, and sometimes the hair within the 186 The Integumentary System cyst protrudes out. Pilonidal cysts often remain Pityriasis rosea is very similar in symptomless, though many become apparent appearance to the rash that occurs with because they are subject to persistent irritation secondary SYPHILIS. As untreated from clothing, movement, and pressure. Extended syphilis has serious health conse- sitting, clothes that fit tightly across the buttocks, quences, the diagnostic path should and activities such as bicycling often create aware- include a blood test to rule out syphilis. ness of pilonidal cysts. The key symptoms of pilonidal disease are PAIN, swelling, erythema (redness), and drainage (pus) Treatment Options and Outlook over the sacrum (tailbone). Often a FEVER accom- Treatment aims to relieve symptoms. Cool baths panies these symptoms, and the person is unable and skin moisturizers often are enough to relieve to sit or walk without great discomfort. The doctor mild pityriasis rosea. Topical and oral ANTIHISTAMINE often can diagnose pilonidal disease based on the MEDICATIONS, and sometimes mild CORTICOSTEROID appearance of the cysts and the history of the MEDICATIONS, are necessary to control itching. The symptoms. The doctor typically lances (cuts open lesions clear up on their own after about 8 weeks, with a sterile instrument) the cysts to allow them though in some people the rash and itching may to drain. Large, purulent, or recurrent cysts may persist for up to 12 weeks. require surgery to remove them. Pilonidal disease tends to be recurrent and per- Risk Factors and Preventive Measures sistent, often continuing throughout life. Surgi- Doctors do not know what causes pityriasis cally removed cysts seldom return, though new though strongly suspect a virus. Outbreaks tend to cysts frequently form in the same proximity. occur among people who are in close proximity, Keeping the area clean and wearing loose-fitting commonly during the winter months. Complica- clothing can help prevent pilonidal cysts from tions are very uncommon though scratching can becoming irritated. Frequent position changes open the lesions and allow secondary infection to when sitting and sitz baths (sitting in warm water) develop. Pityriasis rosea is a self-limiting condition help reduce discomfort when cysts are present. so recovery is without residual effects. See also ABSCESS; ANAL FISSURE. See also MACULE; PAPULE; PLAQUE, SKIN; PRURITUS; PSORIASIS; TINEA INFECTIONS. pityriasis rosea A common SKIN RASH in which an outbreak of lesions occurs and resolves over a plaque, skin Raised, hardened, scaly lesions that period of 3 to 12 weeks, generally without treat- form on the SKIN. Plaques characterize numerous ment or complications. The lesions are characteris- dermatologic conditions. They may itch, hurt, or tically oval with distinct borders and may be flake and may occur in small clusters or cover smooth (macules), raised (papules), or scaly large areas of skin. Treatment for skin plaques tar- (plaques). Often the lesions itch and sometimes gets the underlying conditions and includes meas- they cause the skin to be hypersensitive to touch. ures to moisturize or soften the skin to help Doctors believe a VIRUS causes pityriasis rosea. reduce the plaques. Topical CORTICOSTEROID MEDICA- TIONS or injections of corticosteroids into large Symptoms and Diagnostic Path plaques may help reduce them more quickly. The primary symptom of pityriasis rosea is an See also DERMATITIS; LESION; MACULE; NODULE; itchy (pruritic) rash that appears on the back, PAPULE; PSORIASIS; SCALE. chest, arms, and legs. There is usually an initial outbreak, called a herald LESION, with subsequent pressure sore See DECUBITUS ULCER. eruptions of lesions in other locations. Often the dermatologist will biopsy a lesion to confirm the prurigo A chronic condition in which lesions, diagnosis, as well as conduct BLOOD tests to rule typically papules or nodules, that itch intensely out secondary SYPHILIS, which has a rash very simi- erupt on the SKIN. The lesions may occur any- lar to that of pityriasis rosea. where on the body, though typically form in loca- pruritus 187 tions that allow scratching. Because the cause of pruritus The clinical term for itching, especially prurigo, also called prurigo nodularis, remains itching that engenders the uncontrollable urge to unknown, dermatologists do not know whether scratch. Pruritus is a symptom of innumerable the lesions develop in response to scratching or health conditions and may be localized (confined whether the itching of the lesions establishes the to a specific area or to lesions) or generalized need to scratch. Whichever is the case, one per- (widespread, involving much of the SKIN’s sur- petuates the other. The lesions eventually develop face). The skin may appear reddened (erythema), coarse, scaly surfaces. The intense itching drives swollen (edema) or otherwise irritated, or may many people to scratch the lesions until they show no reason for the itching. bleed, which causes scabs to develop. Lesions that The physiologic mechanism of itching is similar heal often leave white scars. An outbreak of to, though distinctive from, that of PAIN. The NERVE lesions may extend over months or even years. cells, called nociceptors, that send itch signals to Prurigo is sometimes associated with LIVER dis- the BRAIN are scattered throughout the epidermis ease, KIDNEY disease, HIV/AIDS, atopic DERMATITIS, and upper layer of the dermis. Irritants that con- GENERALIZED ANXIETY DISORDER (GAD), and also tact the epidermal and dermal layers of skin can DEPRESSION. Most people who develop prurigo are arouse the nociceptors, coming from the external middle-age or older, though occasionally the con- surface of the skin (such as from lesions that form dition occurs in young people. The diagnostic on the skin) or from within (such as the accumu- pathway may include biopsy to rule out other lation of BILIRUBIN, which accounts for the itching causes for the lesions. Treatment generally incor- that accompanies JAUNDICE). HISTAMINE, which the porates topical CORTICOSTEROID MEDICATIONS and IMMUNE SYSTEM releases during a HYPERSENSITIVITY topical or oral ANTIHISTAMINE MEDICATIONS to sub- REACTION (allergy or ASTHMA), is among the internal due the itching. The dermatologist may choose stimuli that activate these nociceptors. to inject large or recurrent lesions with a corti- The response of scratching is a REFLEX that the costeroid medication. Some people who have autonomic NERVOUS SYSTEM generates in response prurigo benefit from psoralen plus ultraviolet A to itch signals. Researchers theorize that scratch- (PUVA) PHOTOTHERAPY or cryotherapy (freezing), ing activates a mild pain response that overrides which destroys the lesions and allows the skin to the itch response. Pain and itch appear to use heal. many of the same nociceptors, and pain seems to See also LESION; LICHEN SIMPLEX CHRONICUS; NOD- be the more dominant stimulus. However, many ULE; PAPULE; PRURITUS; SCAR. factors contribute to the experience of itching as

HEALTH CONDITIONS ASSOCIATED WITH PRURITUS adverse DRUG reaction ANEMIA BULLOUS PEMPHIGOID CANDIDIASIS CHICKENPOX CHLAMYDIA CIRRHOSIS CONJUNCTIVITIS DERMATITIS DIABETES dry SKIN FOLLICULITIS GENITAL HERPES HEPATITIS HERPES SIMPLEX HYPERTHROIDISM ICHTHYOSIS IMPETIGO JAUNDICE LEUKEMIA LICHEN PLANUS LICHEN SIMPLEX CHRONICUS LYMPHOMA MEASLES MILIARIA parasitic infections PEDICULOSIS PEMPHIGUS PILONIDAL DISEASE PITYRIASIS POLYCYTHEMIA VERA PRIMARY BILIARY CIRRHOSIS PRIMARY SCLEROSING CHOLANGITIS PRURIGO PSORIASIS RENAL FAILURE RUBELLA SCABIES TINEA INFECTIONS URTICARIA VAGINITIS VULVODYNIA 188 The Integumentary System well as to its relief. Scratching is also a conscious See also FOLLICULITIS; INGROWN HAIR; PAPULE; TINEA action, and can itself be an irritant that causes INFECTIONS. itching. Dermatologic conditions in which the itch/scratch relationship becomes circular include psoriasis A common, chronic SKIN condition in LICHEN SIMPLEX CHRONICUS and PRURIGO. which the dermis produces keratinocytes at an Pruritus is often an early indication of systemic accelerated rate. This causes immature ker- health conditions such as jaundice or kidney dys- atinocytes, which are still soft, to reach the epider- function, and is a hallmark symptom of dermato- mis (the outer layer of the skin). The excess logic conditions such as PSORIASIS and DERMATITIS. keratinocytes form lesions, typically scaly plaques, The diagnostic path depends on the complex of that itch (PRURITUS) or hurt. The accelerated symptoms. Treatment may include topical or sys- turnover of keratinocytes creates an IMMUNE temic ANTIHISTAMINE MEDICATIONS or CORTICOSTEROID RESPONSE in the skin that dermatologists refer to as MEDICATIONS and other therapies to resolve the T-CELL activation. The immune response produces underlying condition. It is important to resist INFLAMMATION, the body’s attempt to heal the the urge to scratch, as scratching further irritates plaques. But like the other components of psoria- the skin and may open the pathway for INFECTION. sis, the T-cell response is out of control and results See also ALLERGY TESTING; AUTOIMMUNE DISORDERS; in exacerbating, rather than relieving, the lesions. LESION; RASH. Dermatologists believe GENE mutations establish a predisposition for the accelerations that charac- pseudofolliculitis barbae A condition in which terize psoriasis. External or environmental cir- large numbers of the hairs in the beard region on cumstances such as injury, INFECTION, and stress a man’s face grow inward after shaving, causing then trigger the dysfunctions in the skin that irritation and INFLAMMATION. Pseudofolliculitis bar- result in the psoriasis. Psoriasis appears to run in bae, sometimes called razor RASH or razor bumps, families, suggesting that the mutated genes are occurs most frequently in men whose facial HAIR is inherited. Researchers continue to explore the tightly curled, and is particularly common among genetic foundations of psoriasis. Once psoriasis African American men. The process of shaving manifests, it remains in a lifelong pattern of out- pulls the hairs before cutting them, allowing the break and REMISSION. cut tips to retreat within the hair follicle. When Generally, dermatologists classify five types of the facial hair is tightly curled the shaved tips of psoriasis. Psoriasis in any of these types can also the hairs, which are pointed and sharp, turn into cause inflammation of the joints, a form of arthri- the sides of the follicle. As they grow they punc- tis called psoriasic arthritis. Dermatologists may ture the follicle rather than growing out of the fol- also refer to psoriasis according to the parts of the licle’s opening, creating blocked follicles. The body affected, such as palmar-plantar which entire beard area often becomes involved, causing affects the palms of the hands and soles of the considerable discomfort and difficulty shaving. feet. About 7 million Americans have psoriasis. The dermatologist can usually diagnose pseudo- Erythrodermic psoriasis In erythrodermic pso- folliculitis barbae on the basis of its appearance, riasis, widespread areas of the skin become red though may choose to scrape several of the and scaly, and often swollen. This is the least com- inflamed papules (bumps) to rule out INFECTION. mon but most severe type of psoriasis. It can Shaving with an electric razor, which does not develop from any of the other types of psoriasis. pull and cut the hair as much as a blade razor, Flexural psoriasis Also called inverse psoriasis, may reduce symptoms for some men, though flexural psoriasis forms smooth though itchy many men experience irritation and inflammation lesions in areas such as the axillae (underarms), regardless of shaving method. When that is the creases of the leg in the groin, under the breasts, case, the optimal solution is to stop shaving. Topi- and other skinfold areas. Irritation from rubbing cal preparations such as benzoyl peroxide lotion or and sweating exacerbates the lesions. tretinoin cream are also sometimes helpful, Guttate psoriasis In guttate psoriasis, the sec- though may themselves cause SKIN irritation. ond-most common type of psoriasis, the lesions psoriasis 189 are small and look as though they were dropped with white blood cells, dead skin cells, and other onto the skin. The lesions have raised edges with matter that has the appearance of pus. Adverse centers that are somewhat depressed and appear DRUG reactions and topical irritants often trigger crumpled. Guttate psoriasis is most common on pustular psoriasis. the trunk, arms, legs, and scalp. The lesions itch, and may crack and then crust over before HEALING. Symptoms and Diagnostic Path Upper respiratory infections such as COLDS or The dermatologist diagnoses psoriasis primarily on PHARYNGITIS (notably STREP THROAT) often trigger the basis of its symptoms and history, and may outbreaks of guttate psoriasis. choose to biopsy representative lesions to confirm. In its early stages, psoriasis may be difficult to dis- PSORIASIS AND BLOOD DONATION tinguish from DERMATITIS and other skin disorders. Some oral medications for psoriasis stay in the The diagnosis becomes more conclusive when BLOOD for an extended time and have the poten- other family members have psoriasis. tial to cause serious BIRTH DEFECTS. Blood banks defer people who take or who have taken these Treatment Options and Outlook medications from donating blood for periods of The extent to which medical treatments can miti- time, depending on the medication. People who gate the symptoms of psoriasis depends on the have taken etretinate at any time, which is no type and severity of the psoriasis. Unfortunately, longer available, are permanently deferred psoriasis responds unpredictably to treatment because it remains in the blood indefinitely. methods, with great individual variation. As well, the lesions may become resistant to specific treat- Plaque psoriasis The most common form of ments or medications over time, requiring a shift psoriasis, plaque psoriasis features erythematous in therapeutic approach. This results in a trial- (reddened) plaques that typically develop on the and-error approach that often frustrates those knees, elbows, scalp, and trunk. The plaques itch who have psoriasis. Dermatologists generally fol- and sometimes hurt and often crack, bleed, and low a sequential approach of progressively more crust. Plaque psoriasis also can affect the finger- intense therapy. Many people with moderate to nails and toenails, causing pitting, deformation, severe psoriasis use a combination of therapies to discoloration, and separation from the nail bed. help control their symptoms. ANTIBIOTIC MEDICA- Emotional and physical stress (such as illness or TIONS may be necessary to treat secondary infec- injury) may initiate outbreaks of plaque psoriasis. tions that affect psoriasis lesions. Some people have few outbreaks and other people have lesions nearly continuously. Risk Factors and Preventive Measures Pustular psoriasis The lesions in pustular pso- Because psoriasis has genetic predisposition, it is riasis look infected but simply contain fluid mixed not possible to prevent its development. Once pso-

PSORIASIS SYMPTOMS Type of Psoriasis Characteristic Symptoms erythrodermic extensive scaly plaques; erythema (redness); INFLAMMATION; intense PRURITUS (itching) widespread SKIN involvement flexural (inverse) smooth, erythematous lesions skinfold areas, underarms, groin; pruritus with irritation such as sweating or rubbing guttate small, droplike lesions; cracks and crusting; mild to moderate pruritus trunk, arms, legs, scalp plaque erythematous, scaly lesions; cracks, bleeding, crusting; mild to moderate pruritus knees, elbows, scalp, trunk, fingernails, toenails pustular lesions that appear to contain pus; crusting while HEALING; mild to moderate pruritus trunk, arms, legs 190 The Integumentary System

TREATMENTS FOR PSORIASIS Topical Medications alclomestasone amcinonide anthralin betamethasone calcipotriene clobetasol coal tar desonide desoximetasone diflorasone flumethasone fluocinonide flurandrenolide halcinonide halobetasol hydrocortisone methlprednisolone mometasone prednisolone salicylic acid triamconolone

Phototherapy PUVA phototherapy excimer laser ultraviolet B (UVB) phototherapy

Systemic Medications acitretin alefacept cyclosporine efalizumab etanercept hydroxyurea infliximab methotrexate mycophenolate mofetil 6-thioguanine sulfasalazine tretinoin

riasis manifests, it is important to receive prompt CONDITIONS ASSOCIATED WITH PURPURA and appropriate medical treatment as well as iden- adverse DRUG reaction aging tify and avoid triggers. Limited sun exposure, with ANAPHYLAXIS congenital precautions to prevent SUNBURN, may mitigate congenital RUBELLA syndrome CYTOMEGALOVIRUS (CMV) attacks and help the skin remain healthy. immune thrombocytopenic meningococcal See also BLOOD DONATION; BULLOUS PEMPHIGOID; purpura (ITP) SEPTICEMIA JOINT; KERATINOCYTE; LESION; NAILS; PEMPHIGUS; STRESS ROCKY MOUNTAIN SPOTTED thrombotic thrombocytopenic AND STRESS MANAGEMENT. FEVER purpura (TTP) VASCULITIS purpura Smooth, moderately sized lesions, typi- cally dark red to reddish purple, that result from See also ECCHYMOSIS; LESION; PETECHIAE. bleeding under the surface of the SKIN. Purpura often look like small bruises and may occur any- pustule A blisterlike formation that contains a where on the body, including mucous mem- pus, thick fluid of white blood cells, cellular branes. The presence of purpura signals an debris, and sometimes BACTERIA. Pustules tend to underlying health condition resulting either from hurt and sometimes itch. They commonly develop PLATELET deficiency, which delays COAGULATION (the in numerous dermatologic conditions ranging clotting process), or bleeding due to systemic from ACNE to FOLLICULITIS to PSORIASIS. Often pus- INFLAMMATION or INFECTION. As some of these tules resolve without medical intervention, going underlying conditions are serious and potentially away when the underlying condition causing life-threatening, the appearance of purpura them is under control. Warm, moist compresses or (except senile purpura and actinic purpura, which soaking and sometimes medications to reduce are common in aging skin) requires immediate INFLAMMATION or fight INFECTION can speed HEALING. medical evaluation. The doctor can distinguish Topical or oral ANTIBIOTIC MEDICATIONS may be nec- purpura from other discolorations by applying essary when there is infection. gentle pressure to them. Purpura remain discol- See also MACULE; NODULE; PAPULE. ored, while other kinds of lesions often blanch (turn lighter). PUVA therapy See PHOTOTHERAPY. R

rash A general term for a broad range of SKIN three to six hours, though can take longer for a eruptions. A rash is a symptom rather than itself a complex, total rhytidoplasty. Occasionally the sur- health condition and may accompany numerous geon may prefer to keep the person overnight in dermatologic or systemic conditions. Viral and the hospital. bacterial infections, immune and autoimmune Before the operation the surgeon carefully responses, toxic contacts, systemic illnesses, marks the incision lines on the face with a surgical chronic health conditions, and PARASITIC INFESTA- marking pen or permanent marker. Rhytidoplasty TIONS often cause rashes. Many rashes are so gen- involves separating the skin from the underlying eralized that they are difficult to diagnose in the tissues, trimming away excess fat as well as skin, absence of other symptoms. Some rashes are so and reattaching the skin so it is tighter across the distinctive that their diagnosis requires no further supporting tissues. Depending on the type of oper- symptoms. Nearly all rashes go away when the ation, the surgeon may also bolster the supporting underlying health condition is resolved. Treatment tissues with suspension sutures to help them “lift” for the rash may consist of approaches to mitigate the face. symptoms, typically itching, and may include topi- Swelling, discoloration, and PAIN are common cal and oral ANTIHISTAMINE MEDICATIONS. following surgery, though ANALGESIC MEDICATIONS (pain relievers) can mitigate the pain. Many peo- HEALTH CONDITIONS ASSOCIATED WITH RASH ple experience pulling and stretching sensations adverse DRUG CHICKENPOX DERMATITIS during HEALING. Skin closures, usually sutures or reaction DIAPER RASH FOOD ALLERGIES staples, remain for 7 to 10 days. Bruising and HYPERSENSITIVITY LYME DISEASE MEASLES swelling may remain for several weeks, as does REACTION MILIARIA parasitic numbness of the skin. Full recovery takes several rheumatic FEVER RHEUMATOID ARTHRITIS infestation months. RUBELLA SCARLET FEVER STREP THROAT The risks of rhytidoplasty include excessive bleeding during as well as after surgery, INFECTION, See also BACTERIA; IMMUNE RESPONSE; INFECTION; permanent loss of sensation or NERVE damage, PRURITUS; PSORIASIS; VIRUS. excessive scarring, separation of the tissues, and tissue death (NECROSIS). It is important to have rhytidoplasty The clinical term for facelift, an realistic expectations around what the surgery can OPERATION to smooth and tighten the SKIN on the and cannot achieve and to understand the range face. Rhytidoplasty, also called rhytidectomy, is a of variation that is possible with regard to the final cosmetic surgery appropriate for treating moderate outcome. Though many people are satisfied with to significant WRINKLES and sags on the face. There their appearance when healing is complete, there are numerous variations of rhytidoplasty that tar- is an element of unpredictability as to the final get only certain regions of the face or the whole result. Rhytidoplasty does not prevent further face. Rhytidoplasty is generally an outpatient sur- changes, such as those resulting from the natural gery (AMBULATORY SURGERY) with the person going aging process, from occurring. People who wish to home the same day. The operation generally takes maintain a specific appearance through cosmetic 191 192 The Integumentary System surgery are likely to require multiple procedures • rhinophyma (enlarged and bulbous nose) in over time. It is important to discuss these factors advanced or severe rosacea with the plastic surgeon. See also AGING, INTEGUMENTARY CHANGES THAT The dermatologist generally can make the diag- OCCUR WITH; BLEPHAROPLASTY; RHINOPLASTY; SURGERY nosis on the basis of the appearance and history of BENEFIT AND RISK ASSESSMENT. the symptoms and the person’s age. Other factors that support a rosacea diagnosis include a personal ringworm See TINEA INFECTIONS. or family health history of AUTOIMMUNE DISORDERS or rosacea symptoms. rosacea An inflammatory condition that pro- duces acnelike outbreaks and erythema (redness) Treatment Options and Outlook on the face. Rosacea, sometimes incorrectly called Effective treatment for rosacea varies widely; what adult ACNE, occurs primarily in people over age 40 works for some people may have no effect for oth- and becomes more common with advancing age. ers. Dermatologists generally offer a combination Dermatologists do not know what causes rosacea, approach of topical products and oral ANTIBIOTIC though believe it is an interaction between genetic MEDICATIONS that are effective in controlling skin and environmental factors. About 14 million conditions. Most people who have rosacea try a Americans have rosacea. Though more women number of treatments to find those that are the than men have rosacea, men tend to have more most effective. severe symptoms. COMMON TREATMENTS FOR ROSACEA Symptoms and Diagnostic Path Topical The symptoms of rosacea are mild and general at azelaic acid benzoyl peroxide first, often starting with increasingly frequent clindamycin topical erythromycin topical blushing. Dermatologists believe this early stage of glycolic acid metronidazole rosacea may persist for years, though not many sulfacetamide sulfuric solutions people seek medical care for it alone. Eventually Oral the condition progresses to outbreaks of pimple- doxycycline erythromycin like pustules and other lesions that appear to be minocycline tetracycline acne but resist conventional acne treatments. Most people seek a doctor’s evaluation at this Laser therapy becomes a treatment option for stage. rhinophyma and can reduce the size and shape of The typical symptoms that bring people to the the nose to normal. Laser therapy is also useful for dermatologist include controlling telangiectasis. Treatment for EYE symp- toms may include ophthalmic moisturizing solu- • extended flushing of the face and neck that tions and CORTICOSTEROID MEDICATIONS to reduce may persist for hours after onset INFLAMMATION and irritation. As rosacea is a chronic • papules that erupt in clusters across the cheeks, condition with no known cure, treatment is ongo- on the chin and forehead, around the base of ing. the NOSE, and sometimes around the eyelids Risk Factors and Preventive Measures • itching and burning of the face, particularly in People who are fair-skinned, blond, and blue-eyed areas where papules have erupted seem most likely to develop rosacea. Because der- • patches of dry flaky skin when the papules matologists do not know the precise mechanisms retreat of rosacea, there are no known preventive meas- ures. Factors that can sometimes trigger outbreaks • TELANGIECTASIS (fine BLOOD vessels that appear as red lines beneath the surface of the skin) of rosacea, though do not cause rosacea, include

• CONJUNCTIVITIS and itchy, dry eyes • spicy foods rosacea 193

• CAFFEINE and ALCOHOL Actions such as avoiding circumstances that • heat and strenuous physical exercise trigger rosacea outbreaks, using sunscreen with a high sun-protection factor (SPF) when outdoors, • unprotected sun exposure and maintaining diligent therapeutic approaches • strong emotional reactions such as anger, fear, can keep rosacea in check for many people who or embarrassment have the condition. • hot showers or baths, hot tubs, saunas See also DERMATITIS; HORMONE; LESION; PERSONAL • hormones (MENSTRUATION, PREGNANCY, MENO- HEALTH HISTORY; PHOTOSENSITIVITY; PUSTULE; SUN PRO- PAUSE) TECTION. S scabies A contagious parasitic infestation with drop from the skin, often as visible flakes such as the SKIN mite Sarcoptes scabei that typically causes characterize DANDRUFF. intense itching (PRURITUS) and visible bites or irri- See also DERMATITIS; ICHTYOSIS; KERATINOCYTE; tation to the skin. The bites create small, reddened PLAQUE, SKIN; PSORIASIS; SEBORRHEIC KERATOSIS. papules (bumps) and often a RASH on the sur- rounding skin that is the burrows the mites make scar A formation of fibrous tissue that remains to lay their eggs. The most common sites for sca- at the site of a healed wound. Though a scar will bies are skinfold areas such as in the groin, under not entirely match the surrounding tissue, most the breasts and armpits, between the shoulders, scars heal to be barely noticeable. behind the knees, at the creases in the elbows, Some scars become overgrown. A hypertrophic and on the inner wrists. Itching typically becomes scar is enlarged though does not extend beyond intense at night. Aggressive scratching can cause the original wound site. Over time, most hyper- secondary bacterial infections of the skin to trophic scars retreat to become less noticeable. The develop. Scabies spreads through close physical dermatologist may reduce a hypertrophic scar by contact. injecting it with an intralesional corticosteriod The doctor diagnoses scabies with skin scrap- medication or with pulsed dye laser treatments. ings of the papules or rash. Microscopic examina- The success of such procedures depends on the tion of the scrapings often reveals eggs or fecal location and nature of the hypertrophic scar. matter from the mites. Applying a lotion that con- KELOID scars occur when the scar formation tains a pesticide such as permethrin, lindane, or process continues after the wound heals. The crotamiton will kill the mites, though the itching keloid continues to grow, becoming a spongy may persist for a few days. All members of the LESION that no longer has anything to do with household should receive treatment. It is also wound HEALING. Keloids can become quite large. important to wash clothing, towels, and bed linens The dermatologist may remove keloids that are in very hot (130ºF) water for at least 10 minutes continually irritated, such as by clothing, or that as a precaution to kill any mites these items might are cosmetically undesirable. However, keloids be harboring, as mites can live outside the body tend to recur. for up to 36 hours. Reinfestation may occur with See also PLASTIC SURGERY. reexposure. See also BACTERIA; INFECTION; PAPULE; PARASITES; sebaceous glands The small glands that produce PEDICULOSIS. sebum, a lipid-based, oily fluid that lubricates the surface of the SKIN. Sebum is mostly the metabolic scale A SKIN LESION in which keratinocytes clump waste that remains after fat cells break down. together instead of falling away from the skin, Most sebaceous glands empty into HAIR follicles, adhering to the skin. Keratinocytes separated from secreting sebum along the emerging hair shaft. the epidermis are nearly translucent, often giving Some sebaceous glands exist independent of hair scales a silver or white cast. When enough scales follicles and secrete sebum directly to the skin’s accumulate, their weight causes them to finally surface, such as those on the glans of the PENIS. 194 skin 195

The palms of the hands and the soles of the feet Though removed lesions do not recur, others may are the only skin surfaces that do not have seba- grow nearby. ceous glands. See also ACROCHORDON; LESION; NEVUS; SKIN SELF- The oily consistency of sebum gives the skin a EXAMINATION; WART. highly water-resistant coating. The lubricating qualities of sebum keep the keratinocytes, the cells skin The body’s largest organ, making up the that make up the epidermis, supple and flexible. body’s covering and about 15 percent of the total Without adequate lubrication the skin becomes body weight The skin’s three layers—epidermis, dry and the keratinocytes scale and flake, present- dermis, and subcutaneous layer—help the body ing not only an undesirable cosmetic appearance maintain its structure; protect against INFECTION; but also compromising the skin’s resistance against and regulate fluids, electrolytes, and temperature. pathogenic (disease-causing) microorganisms. Numerous health conditions, localized and sys- Sebum also helps regulate the skin’s natural flora, temic, can affect the skin and its functions. the collective of BACTERIA, yeasts, and other micro- The subcutaneous layer, innermost to the body, scopic organisms that inhabit the epidermis. These contains primarily adipose tissue more familiarly microorganisms draw nutrients from the lipids in called body fat. The dermis, the middle layer, pro- the sebum. vides the structure of the skin. It contains connec- For further discussion of the sebaceous glands tive tissue, the SEBACEOUS GLANDS, and an abundant within the context of integumentary structure and supply of nerves and blood vessels. The dermis function, please see the overview section, “The nourishes the epidermis above it and attaches to Integumentary System.” the subcutaneous layer beneath it, holding the See also ACNE; DANDRUFF; KERATINOCYTE; SWEAT skin in place. HAIR follicles and SWEAT GLANDS GLANDS. extend from the epidermis into the dermis and a bit into the subcutaneous layer. seborrheic keratosis A condition in which non- The primary cells of the skin, melanocytes and cancerous (benign) growths arise on the SKIN. The keratinocytes, originate in the base, or basal, level lesions resemble warts though appear pasted on of the epidermis. Keratinocytes migrate outward rather than attached to the skin. The lesions are to form the upper epidermis, gradually flattening most commonly brown or black, though may be and hardening. The epidermis varies in thickness yellow, gray, tan, or other colors. Seborrheic ker- and other characteristics, accommodating the atosis becomes increasingly common in people age needs of different body surfaces. The epidermis of 40 and older. Most people develop multiple the palms of the hands and the soles of the feet is lesions. The lesions cause no symptoms beyond thick and tough, for example, while that of the their presence, unless frequent irritation causes eyelids is soft and only two or three cells in depth. them to itch, hurt, or bleed. The skin is also the body’s organ of tactile sen- Seborrheic keratosis requires medical assess- sory perception, or touch. Millions of NERVE end- ment only to ascertain that the lesions are not ings in the skin continually sense environmental cancerous, which typically is apparent on the basis factors such as pressure, temperature, moisture. of their appearance and history. The doctor should Other specialized nerve cells, called nociceptors, biopsy any lesions that are questionable. There is perceive itching and PAIN. Sweat evaporation on no medical reason to remove the lesions once the skin’s surface is the body’s primary cooling diagnosed, however, as they do not turn malig- mechanism, as well as a secondary mechanism for nant. People sometimes want lesions removed electrolyte regulation and balance. that are cosmetically undesirable or in locations For further discussion of the skin within the where they receive frequent irritation such as context of integumentary structure and function, from clothing. Cryotherapy (freezing), curettage please see the overview section “The Integumen- and electrodesiccation (scraping and burning), and tary System.” shave excision (cutting out; requires no sutures) See also KERATINOCYTE; MELANOCYTE; NAILS; SEBA- are the most common methods of removal. CEOUS GLAND. 196 The Integumentary System

HEALTH CONDITIONS THAT MAY AFFECT THE SKIN

ACNE ACROCHORDON ACTINIC KERATOSIS ALBINISM BIRTHMARK BLISTER BULLA BULLOUS PEMPHIGOID CALLUS CARBUNCLE CELLULITIS CORNS CRADLE CAP DECUBITUS ULCER DERMATITIS DISCOID LUPUS ERYTHEMATOSUS (DLE) EPIDERMOLYSIS BULLOSA ERYSIPELAS ERYTHEMA MULTIFORME ERYTHEMA NODOSUM FOLLICULITIS FROSTBITE FURUNCLE HYPERHIDROSIS ICHTHYOSIS IMPETIGO KAPOSI’S SARCOMA KELOID LICHEN PLANUS LICHEN SIMPLEX CHRONICUS MILIARIA NEVUS PAPILLOMA PEDICULOSIS PEMPHIGUS PILONIDAL DISEASE PITYRIASIS PRURIGO PSORIASIS ROSACEA SCABIES SEBORRHEIC KERATOSIS SKIN CANCER SUNBURN TINEA TOXIC EPIDERMAL NECROLYSIS URTICARIA VITILIGO WART WHITLOW XANTHOMA

skin cancer Malignant growth that arises from skin against sun exposure, as sun exposure stimu- the epidermis or dermis. There are many types of lates melanocytes to produce melanin. CANCER that occur in the SKIN. The three most common types of skin cancer are basal cell carci- The ultraviolet light used in tanning noma, squamous cell carcinoma, and malignant booths affects the SKIN in the same way melanoma. Skin cancer is the most widely diag- as the ultraviolet lightwaves of the sun, nosed type of cancer in the United States, with and carries the same exposure risk for about 1 million new cases each year. The vast skin cancer. majority of skin cancers—basal cell carcinoma and squamous cell carcinoma—are nearly 100 percent The correlation between sun exposure and skin curable with early detection and treatment. Malig- cancer also means that nearly all skin cancers are nant melanoma, the least common form of skin highly preventable. Cancer experts recommend cancer, is more dangerous because it tends to diligent SUN PROTECTION measures beginning in metastasize (spread) early in its development, early childhood in combination with regular skin though it also has a high cure rate when detected examinations to detect suspicious growths or and treated before it metastasizes. changes in existing lesions. Other types of cancer Cancer experts believe nearly all skin cancer that can affect the skin, but are not primary skin results from sun damage to the cells of the skin. cancers or related to sun exposure, include The ultraviolet lightwaves the sun emits cause KAPOSI’S SARCOMA, primarily a manifestation of subtle changes in the ways skin cells function. HIV/AIDS in the United States, and cutaneous T-cell Over time these changes can result in aberrant LYMPHOMA. growth, causing skin cells to form into cancerous lesions. People with fair skin are most vulnerable Basal Cell Carcinoma to this damage, as their skin produces less Basal cell carcinoma is a cancer of the ker- melanin. In addition to giving the skin its color, atinocytes that form the bottom, or base, of the melanin protects the skin from the sun by absorb- epidermis, also called basal cells. Most basal cell ing the ultraviolet lightwaves that cause damage. carcinomas erupt around HAIR follicles, leading A tan paradoxically results from and protects the researchers to suspect they originate in the follicle skin cancer 197 structure or the SEBACEOUS GLAND (sometimes col- • ulceration on the lips that resembles a COLD lectively called the pilosebaceous unit). Basal cell SORE but does not heal carcinomas nearly always arise on sun-exposed skin surfaces, though may also occur on skin Though most commonly a cancer of the surface exposed to radiation such as for RADIATION THERAPY. skin (particularly sun-exposed), squamous cell The characteristic symptoms of basal cell carci- carcinoma also can develop in the mucous mem- noma are branes. Untreated squamous cell carcinoma will eventually grow downward to penetrate the der- • open sore that does not heal mis and subcutaneous layer, and may spread to • reddened or flaky patch that itches or hurts LYMPH structures that enable widespread metasta- • shiny, discolored NODULE (bump) that develops sis. Doctors diagnose about 200,000 Americans on the skin with squamous cell carcinoma each year. Though • pinkish, craterlike structure with raised edges squamous cell carcinoma is less common in dark- skinned than in light-skinned people, among skin and tiny BLOOD vessels visible in the center cancers in dark-skinned people squamous cell car- • yellowish, waxy area that resembles a scar cinoma is the most common. though gradually enlarges and may itch

Though basal cell carcinomas rarely metasta- Malignant Melanoma size, they do spread within the epidermis and can Malignant melanoma arises from melanocytes, the cause considerable damage to the skin. Doctors cells that produce melanin. Benign skin lesions diagnose about 800,000 Americans with basal cell such as nevi (moles) composed of melanocytes are carcinoma each year, making it the most common often the staging sites for malignant melanoma. cancer of any type. A person who has one basal Malignant melanoma can develop and metastasize cell carcinoma is likely to develop others, though quickly. Diligent monitoring for changes in exist- removed tumors seldom recur. Basal cell carci- ing lesions such as moles is the most effective noma is uncommon in dark-skinned people. method for early detection and diagnosis. Doctors classify malignant melanoma by growth pattern Squamous Cell Carcinoma (such as nodular, superficial, or spreading) or by Squamous cell carcinoma is a cancer of the ker- depth of invasion, metastasis, and nodal involve- atinocytes in the upper layer of the epidermis, for- ment. Small, localized malignant melanomas are merly called squamous cells because of their about 90 percent curable with early diagnosis and squamous, or squashed, appearance. Nearly all treatment. Widely metastasized malignant mela- squamous cell carcinoma evolves from ACTINIC noma is usually fatal. KERATOSIS (though not all actinic keratosis lesions The characteristic symptoms of malignant become cancer). Because of this, doctors consider melanoma are actinic lesions precancerous and remove them to end their progression, effectively thwarting the • change in the size, symmetry, color, or texture cancer’s development. Squamous cell carcinoma of an existing NEVUS (mole) can but does not often metastasize. Sun damage • bleeding or oozing from an existing nevus causes most squamous cell carcinoma, though • a new nevus that emerges and grows rapidly, tumors can form in sites of continual irritation. especially one that has asymmetrical shape, The characteristic symptoms of squamous cell irregular borders, multiple colors, or exceeds carcinoma are one quarter inch in diameter (the ABCD crite- ria) • crusted, raised growth resembling a WART that easily or frequently bleeds Doctors diagnose about 50,000 Americans with • patch of red, flaky skin that oozes or bleeds malignant melanoma each year, many of whom • sore that bleeds and crusts but does not go have moderate to advanced cancer by the time of away diagnosis. 198 The Integumentary System

ABCD CRITERIA FOR MALIGNANT MELANOMA NODES, and may require follow-up CHEMOTHERAPY if A = asymmetry; halves do not match the cancer has metastasized. Dermatologists may B = borders; edges are irregular or vague use cryotherapy (liquid nitrogen) to remove pre- C = color; two or more colors are present cancerous lesions, such as those of actinic kerato- D = diameter; larger than one quarter inch sis, and very small lesions that appear suspicious. Other treatment options may include topical Symptoms and Diagnostic Path imiquimod (Aldara) cream and RADIATION THERAPY. Symptoms vary among the types of skin cancer, Risk Factors and Preventive Measures though generally any wound or sore that does not The single-most important risk factor for skin can- heal or mole that changes appearance is suspect. cer is excessive sun exposure. People born before The diagnostic path typically includes biopsy of the 1980s have the highest risk for skin cancers suspicious lesions. The dermatologist may remove because they grew up before sunscreen products very small lesions without biopsy, as doing so became available. Skin cancers tend to manifest effectively removes any cancer that is present. several decades after the exposures that damaged Biopsy identifies the type of cancer present, which the skin, making it important for people age 40 determines the appropriate course of treatment. and older to have yearly skin examinations from a CHARACTERISTIC SKIN CANCER SYMPTOMS physician and to perform monthly SKIN SELF-EXAMI- NATION. People who have had skin cancers Type of Skin Cancer Characteristic Symptoms removed may need more frequent physician eval- basal cell carcinoma sore that does not heal uation. The most effective preventive measures persistent red or flaky patch are those that safeguard the skin from sun dam- that itches age. These measures include shiny, discolored NODULE vascular crater • limit sun exposure during peak ultraviolet yellowish, waxy, itchy plaque intensity (10 a.m. to 2 p.m. in most of the squamous cell carcinoma wartlike lesion that bleeds United States) flaky patch that bleeds • wear protective clothing to cover the skin sore that repeatedly bleeds • apply sunscreen liberally and frequently before and crusts and during sun exposure lip ulceration that does not heal See also CANCER RISK FACTORS; CANCER TREATMENT malignant melanoma ABCD criteria: OPTIONS AND DECISIONS; KERATINOCYTE; MELANOCYTE. • asymmetrical appearance • irregular borders skin replacement A procedure for restoring SKIN • multiple colors to areas of the body where there has been exten- • diameter greater than one sive damage and loss of skin. BURNS, major quarter inch trauma, surgery, varicose ulcers, and decubitus ulcers are among the conditions that require skin Treatment Options and Outlook replacement. Skin-replacement techniques may The preferred treatment for nearly all skin cancer use skin grafts or synthetic skin products for tem- is surgical removal, which may include various porary or permanent reconstruction. methods such as curettage and electrodesiccation (scraping and cauterization), excision (cutting Skin Grafts out), and MOHS’ MICROGRAPHIC SURGERY. Micro- There are three main sources for skin grafts: scopic examination of the removed LESION con- firms the diagnosis and type of cancer. Malignant • autograft, which harvests skin from one loca- melanoma requires extensive excision, with wide tion on the person’s body and transplants to margins and possible removal of nearby LYMPH another for permanent skin replacement skin self-examination 199

• allograft, which uses donor skin harvested from to trim them to the appropriate size. Synthetic a cadaver to create temporary protection while grafts do not require meshing and are also ready the wound heals enough to accept a permanent to place. TISSUE EXPANSION is a method that allows graft the surgeon to literally stretch the growth pattern • xenograft, which uses specially prepared skin of existing skin to grow extra skin the surgeon can from an animal, usually a pig (porcine then harvest and place where needed. It takes sev- xenograft), to create temporary protection eral months to grow enough skin to use for a while the wound heals enough to accept a per- graft. manent graft Risks and Complications An autograft has the highest rate of success The main risk of skin replacement is graft failure, because it is the person’s own tissue. A skin graft which can occur regardless of the graft source. may be full thickness, which includes the com- Numerous factors contribute to graft success or plete epidermal and dermal layers, or split thick- failure. The graft may fail to develop an adequate ness, which includes the epidermal and upper blood supply or the match between the donor dermal layer. A full-thickness graft generally pro- graft and the recipient site may be not quite right. duces a better cosmetic result though carries a The underlying tissue foundation may not be ade- higher risk of failure. A split-thickness graft gener- quate to support new skin growth. Other potential ally adheres, or “takes,” better though may heal complications include excessive bleeding during or somewhat irregularly. after surgery and INFECTION.

Synthetic Skin Outlook and Lifestyle Modifications Synthetic skin uses materials crafted in the labora- Small grafts that heal without complications may tory to create a substitute skin that may serve as a require few lifestyle changes. Large wounds may temporary covering or a matrix to support perma- require extended rehabilitation and significant nent new skin growth. Typically the matrix con- lifestyle modifications. With more extensive skin sists of two layers: one that the new cells grow replacement, there may be continued care needs. into and that remains a permanent part of the The overall outlook depends more on the reason skin and the other one, usually made of silicone or for the skin replacement than the replacement a similarly inert material, the surgeon removes itself. The recipient site remains more vulnerable when HEALING is well established. The new skin than native skin to damage from sun exposure grows through the synthetic matrix, absorbing it and trauma. into its structure. See also DECUBITUS ULCER; HAIR TRANSPLANTATION; SUN PROTECTION. Surgical Procedure Skin replacement may be an outpatient or inpa- skin self-examination A method for early detec- tient OPERATION, depending on the nature of the tion of suspicious and possibly cancerous lesions wound. If using an autograft, the surgeon first on the SKIN. Health experts recommend skin self- harvests the graft from the donor site. With an examination monthly for adults. Doing skin self- autograft or allograft, the surgeon typically uses a examination takes 5 to 10 minutes and requires device called a mesher to put tiny holes evenly privacy to fully undress, a full-length mirror, and a throughout the graft. This meshing allows the handheld mirror. Many people find it convenient graft to stretch to cover a larger area. The holes to do a skin self-examination before or after also allow fluid to drain from the site, improving bathing or showering. Use the mirrors to visualize healing. After about 36 hours, the graft begins to and examine the entire skin surface including the develop new BLOOD vessels that tether it to the bottoms of the feet and the genitals. A handheld underlying tissue and provide a source of nourish- hair dryer may help to examine the scalp. Look ment. Xenografts typically arrive already meshed for skin blemishes and moles, and compare them and ready to place, needing only for the surgeon to the ABCD SKIN CANCER screening characteristics 200 The Integumentary System

ABCD SKIN EXAMINATION Characteristic Normal Suspicious A asymmetry matching halves (symmetrical) unequal or nonmatching halves (asymmetrical) B border smooth, even edges ragged, notched, or otherwise uneven edges C color single shade of brown varied shades of brown; multiple colors D diameter less than one quarter inch larger than one quarter inch

for malignant melanoma. After doing several skin name suggests, changes in the tissue structure and self-examinations, most people are familiar with appearance that result from the skin stretching their usual lesions and blemishes and can quickly and separating from the underlying supportive tis- identify any changes that have taken place since sues. Such stretching most commonly occurs with the previous self-exam. A dermatologist should PREGNANCY, BREAST augmentation surgery, and evaluate any suspicious findings. weight gain and loss, and affects the abdomen, See also ACTINIC KERATOSIS; LESION; SEBORRHEIC upper arms, thighs, and breasts. Early stretch KERATOSIS. marks appear pink; mature stretch marks are gen- erally pale. In addition to the altered pigmenta- skin tag See ACROCHORDON. tion, stretch marks may have a different texture than the surrounding skin. Stretch marks are cos- staphylococcal scalded skin syndrome A poten- metic and do not affect health or reflect health tially life-threatening bacterial INFECTION of the conditions. Cosmetic treatments to minimize the skin that most commonly affects infants and appearance of stretch marks include laser therapy young children. Staphylococcus aureus is the infec- and topical products such as glycolic lotions and tive agent. The infection is systemic, causing erup- tretinoin cream. tions on the skin that give the appearance of See also PLASTIC SURGERY. scalding. A single LESION heralds the onset of the infection, with multiple lesions rapidly emerging. sunburn Damage to the epidermis and some- The lesions are scarlet red and quickly BLISTER. The times the dermis, the top and middle layers of the blisters (bullae) are very fragile and peel away SKIN, as a consequence of extended, unprotected from the skin with touch. The lesions spread to be sun exposure. The sun emits several wavelengths contiguous with one another, covering large por- of ultraviolet light. Those that reach the earth’s tions of the body. The loss of skin exposes the surface are ultraviolet A (UVA) and ultraviolet B body to other pathogens that can cause complicat- (UVB). Each affects the skin in different ways. ing infections and means the body cannot main- UVA activates melanocytes, the cells that produce tain proper thermal or fluid regulation. Prompt melanin (pigment) and may produce a thermal diagnosis and treatment with ANTIBIOTIC MEDICA- (heat) response that causes the skin to turn red. TIONS is essential. Most children fully recover with Though the skin may feel hot, this is not actually appropriate treatment. The infection is highly con- sunburn but rather a thermal (heat) response. tagious. Diligent HAND WASHING is crucial for care- Sunburn is a delayed response to UVB expo- givers and family members. sure. UVB lightwaves do not activate the See also BACTERIA; BULLA; PATHOGEN; TOXIC EPIDER- melanocytes but instead affect keratinocytes. MAL NECROLYSIS; TOXIC SHOCK SYNDROME. When the epidermis (skin’s outer layer) contains deeply pigmented keratinocytes, such as in a per- Stevens-Johnson syndrome See TOXIC EPIDERMAL son who has dark skin or a tan from previous sun NECROLYSIS. exposure, the pigment (melanin) absorbs the UVB and the keratinocytes escape damage. When the stretch marks Irregular, discolored streaks or skin is light, melanin distribution is also light and lines in the SKIN. Stretch marks represent, as the there is little absorption of UVB. sun protection 201

The keratinocytes bear the brunt of the expo- Protective Clothing sure, and about 8 to 12 hours later show the con- Clothing that covers or shades the skin surfaces is sequences. The damaged cells release toxins and the most effective protection from sun exposure other substances that draw increased BLOOD flow and can block more than 90 percent of the sun’s to the dermis. The additional blood flow causes ultraviolet light, though it is still possible to the skin to become red (erythema). These toxins acquire a sunburn through clothing. Fabric with a irritate the nerve endings in the epidermis and tight weave is more effective than fabric with a dermis, causing PAIN. Fluid may accumulate loose weave. Many items currently manufactured between the cells (edema), causing swelling. With specifically for outdoor activities now use yarns more severe damage, fluid-filled blisters form on and weaving techniques that substantially block the skin. Discomfort peaks about 48 hours after ultraviolet light. Manufacturers use ultraviolet- exposure. At about this same time, the melano- protection factor (UPF) ratings to designate the cytes have infused keratinocytes migrating from extent of the fabric’s ability to prevent ultraviolet the dermis to the epidermis with melanin, giving light penetration. The higher the UPF rating, the them a darker pigment that will offer better pro- more effective the protection. Solid-weave, broad- tection than their predecessors had. brimmed hats help protect the scalp and shelter The most effective treatment for sunburn is a the ears, NOSE, and back of the neck. Technical combination of moisturizing lotion or gel such as gear for many outdoor sports, such as bicycling aloe vera to soothe the irritated skin and a nons- and kayaking, includes gloves that protect the teroidal anti-inflammatory drug (NSAID) such as hands from friction and pressure as well as sun ibuprofen to relieve INFLAMMATION and pain. Most exposure. Sunglasses that block UVA and UVB sunburn discomfort resolves in three to five days. light are necessary to shelter the eyes. Badly sunburned skin that has blistered is likely to peel at this point and requires gentle cleansing to A sunscreen product’s SPF rating minimize the risk for bacterial INFECTION until the applies only to UVB blocking, so it is new skin completely heals. Researchers now important to read the product label to believe one significant sunburn is sufficient to lay determine what protection the product the groundwork for skin cancer decades later. can provide. Repeated mild to moderate sunburns appear to have similar effect. Sunscreens and protective clothing worn during sun exposure can protect Sunscreen against sunburn. Sunscreens that chemically block ultraviolet light See also BLISTER; BURNS; KERATINOCYTE; MELANOCYTE; from penetrating the skin’s surface became avail- NONSTEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS); able in the 1980s. These chemicals work by SKIN CANCER; SKIN SELF-EXAMINATION; SUN PROTECTION. absorbing the light so it does not reach the cells. Most sunscreens block UVB; some also block UVA. sun protection Methods to safeguard the SKIN A sunscreen’s sun-protection factor (SPF) rating, from SUNBURN and sun damage. Though the body provides a general idea of how long the product requires a certain amount of sun exposure to pro- can provide protection based on a time-related duce certain vitamins (such as vitamin D) and help formula. In general, a fair-skinned person will get eliminate chemical wastes from the body, ultravio- a sunburn after about 10 minutes of unprotected let light is a potential hazard for the cells. Melanin exposure to the sun. A sunscreen’s SPF rating is a production, which results in darkening the skin, is multiplier of that marker. A sunscreen with an the body’s primary method for protecting itself. The SPF rating of 15, for example, theoretically per- lighter a person’s natural skin color, however, the mits 15 times as long in the sun before burning, or less effective this method. Many health conditions 150 minutes. A sunscreen with an SPF of 30 that affect the skin, most notably SKIN CANCER, result would allow 300 minutes. These are general from overexposure to the sun and in particular to guidelines, however, and dermatologists recom- ultraviolet B (UVB) light. mend applying more sunscreen about every two 202 The Integumentary System hours during exposure (as well as SPF lip balms to Eccrine sweat glands are functional from protect the lips). Dermatologists recommend sun- shortly after birth and are present in all skin. An screens that block both UVA and UVB lightwaves. individual has between two and three million Because both sunscreen use and skin cancer are eccrine sweat glands that produce about 20 liters on the rise, some researchers have questioned of sweat in 24 hours and can double or triple their whether sunscreens cause, rather than prevent, production rate during strenuous exercise or heat skin cancer. Though there are few clinical studies conditions. Eccrine sweat glands open through of such a correlation, so far there is no evidence to pores directly onto the surface of the skin (pores), support this concern. Nor is there evidence to sup- releasing sweat for rapid evaporation to cool the port claims that sunscreens promote estrogenic skin and lower body temperature. activity in the body, another concern that some Apocrine sweat glands are present only under people have raised. Health experts agree that the arms and in the pubic region, though are proper application of sunscreen is the most effec- abundant in these regions. Although present from tive defense to protect the skin from damage. birth, they are nonfunctional until PUBERTY acti- vates them. The apocrine sweat glands empty into Time of Exposure HAIR follicles rather than directly onto the skin’s The sun’s ultraviolet light is most intense from 10 surface. The sweat the apocrine glands produce a.m. to 2 p.m. in the United States. Health experts contains lipids and proteins, which helps the recommend staying out of the sun as much as sweat mix with the sebaceous fluids in the hair possible during that period of time, especially dur- follicles to reach the skin’s surface. BACTERIA on ing summer months. When this is not practical, the surface of the skin consume the lipids and dermatologists recommend combining protective proteins, creating waste byproducts that pro- clothing and sunscreen for maximum protection. duce the characteristic odor associated with sweat- See also CANCER RISK FACTORS. ing. For further discussion of the sweat glands sweat glands Structures within the dermis layer within the context of integumentary structure and of the SKIN that produce sweat as part of the body’s function please see the overview section “The temperature-regulation mechanisms. There are Integumentary System.” two kinds of sweat glands—eccrine and apocrine, See also HEAT EXHAUSTION; HEAT STROKE; HYPER- both of which arise from the dermis. HIDROSIS; MILIARIA. T–U tattoos A form of body art in which decorative ments as cellular debris. However, this process is inks injected into the dermis permanently stain most effective with black and blue inks, and least the SKIN. Though the needles are solid, they create effective with yellow, red, and orange. Different puncture wounds that then fill with ink. The cells wavelengths of laser are necessary for the various and intracellular spaces of the dermis absorb the colors, so tattoo removal may involve several ses- ink. The health implications of tattoos are twofold: sions. Seldom can the laser remove all color, potential complications at the time of tattooing though it often can remove enough color for the and the challenges of tattoo removal. tattoo to appear only as a slight discoloration of Commercial tattoo artists use mechanical nee- the skin. It is possible for the pigment to darken in dles that rapidly inject inks. The needles and the the skin surface surrounding the tattoo, in ink packets are sterile and for one-time use. response to the laser. Scarring and infection also Though inks are generally of natural origins, some remain slight risks. Other methods of tattoo people have adverse reactions to them that can removal, such as DERMABRASION and excision, may cause swelling, INFLAMMATION, and scarring. more successfully remove the full tattoo though Though many tattoo artists follow appropriate leave considerable scarring. With these methods, antiseptic procedures, many others do not. Most skin grafts are sometimes necessary. US states do not have regulations or procedures to See also BACTERIA; PIERCINGS; PLASTIC SURGERY; establish health standards or confirm their prac- SCAR. tice. The most common risk arising from improper telangiectasis A weblike network of BLOOD ves- skin and equipment cleansing is bacterial INFECTION sels that becomes visible just below the surface of of the tattooed site, which may require treatment the SKIN, commonly called spider veins. Some- with ANTIBIOTIC MEDICATIONS. A less common times telangiectasis is present from birth or early though far more serious infection risk is that of childhood as a BIRTHMARK, though more commonly HEPATITIS and HIV/AIDS, both of which are blood- develops later in life as a manifestation of chronic borne viral infections. Reusing needles and inks sun exposure. Telangiectasis generally has no passes any VIRUS present to subsequent clients. adverse health effects, though many people find Improperly cleaning the tattooing equipment also the lesions cosmetically unacceptable. For telangi- allows viruses to linger, with the potential of pass- ectasis on the face, dermatologists use laser ther- ing them on. apy or fine cautery. For spider veins on the legs, Tattoo removal is far less certain than tattooing. the most common treatment is sclerotherapy in Most methods cause significant scarring. A form of which the dermatologist injects the telangiectasis laser therapy called Q-switched laser offers the with a chemical that irritates the blood vessels, least destructive means for removing tattoos. causing them to SCAR. Over time the discoloration Lasers can destroy the structure of some inks fades. Laser therapy may be a therapeutic option without damaging the surrounding cells. The for some telangiectasis lesions. body’s normal processes then remove the ink frag- See also LESION; VARICOSE VEINS; VEIN.

203 204 The Integumentary System tinea A common fungal INFECTION of the SKIN, affected tissue to examine under a microscope. involving the layers (including the hair and nails) Such examination reveals the dermatophytes or that are cornified (composed of dead ker- evidence of their presence, which is conclusive for atinocytes). Several species of fungi, known col- diagnosis. Inability to identify evidence of der- lectively as dermatophytes, cause tinea infection matophytes points to other causes for the symp- (also called dermatophytosis). People commonly toms. refer to some forms of tinea as ringworm because the lesions have the appearance of worms ringed Treatment Options and Outlook beneath the surface of the skin. Though descrip- Topical ANTIFUNGAL MEDICATIONS often effectively tive this is a misnomer as tinea has nothing to do treat all forms of tinea except those involving the with worms. There are numerous designations of hair or NAILS. Prescription antifungal medications tinea based on where it appears on the body, produce the most reliable results; over-the- though the same group of dermatophytes can counter products may require multiple applica- cause any of tinea’s presentations. tions. Because many people who acquire tinea continue the activities that resulted in exposure, Tinea Common Body Region reinfection is common. Pervasive or resistant tinea Infection Name Affected may require oral antifungal medications to attack tinea barbae ringworm beard area of the face the infection systemically. Oral antifungal therapy tinea capitis ringworm scalp is necessary to eradicate tinea that involves the tinea cruris jock itch genitals hair or the nails. Treatment may require up to tinea corporis ringworm central trunk, arms, eight weeks for some infections, particularly those and legs involving the nails and the feet (tinea pedis). tinea pedis athlete’s foot bottom of the foot and between the toes COMMON ANTIFUNGAL MEDICATIONS FOR TREATING TINEA Tinea is fairly contagious and spreads from per- econazole (topical) fluconazole (oral) son to person as well as through contact with sur- griseofulvin (oral) itraconazole (oral) faces, such as shower floors or soil, that can ketoconazole (topical and oral) miconazole (topical) harbor the fungi. Dermatophytes can exist outside naftifine (topical) oxiconazole (topical) the body for a considerable length of time and sertaconazole (topical) terbinafine (topical and oral) thrive in environments that are warm and moist. Risk Factors and Preventive Measures Symptoms and Diagnostic Path Common environmental settings in which der- The symptoms of tinea vary somewhat according matophytes thrive include communal showers, to the part of the body affected, though generally spas, and swimming pools. Wearing water socks or include sandals when walking on wet surfaces helps pro- tect the feet from contact with the fungi. Tinea • itching (PRURITUS), which may be intense, or can be an opportunistic infection in people who PAIN are IMMUNOCOMPROMISED, such as those taking • redness (erythema) IMMUNOSUPPRESSIVE THERAPY following ORGAN TRANS- PLANTATION or who have HIV/AIDS. • lesions that may appear as papules, vesicles, or See also ALOPECIA AREATA; CANDIDIASIS; DERMATI- plaques TIS; ERYSIPELAS; FUNGUS; IMPETIGO; KERATINOCYTE; • cracking or scaling of the lesions LESION; ONYCHOMYCOSIS; PAPULE; PSEUDOFOLLICULITIS • irregular HAIR loss (ALOPECIA) when the site of BARBAE; PSORIASIS; TINEA VERSICOLOR; VESICLE. the infection is the scalp tinea versicolor A fungal INFECTION of the SKIN The diagnostic path is generally straightfor- that causes areas of altered pigmentation, usually ward. The doctor may take small scrapings of darkened patches. Unlike other forms of TINEA, urticaria 205 tinea versicolor is not contagious. The FUNGUS See also PLASTIC SURGERY. responsible, Malassezia furfur, is normally present on the skin (NORMAL FLORA). Dermatologists do not toxic epidermal necrolysis A life-threatening know why the fungus causes infection in some inflammatory condition affecting the SKIN and people and not in others, though they suspect the underlying connective tissues, also called Stevens- infection is opportunistic in being able to gain a Johnson syndrome. Toxic epidermal necrolysis foothold when other challenges are occupying the usually results as an adverse DRUG reaction though IMMUNE SYSTEM. Treatment is typically a combina- may occur as a complication of INFECTION or tion of topical and oral ANTIFUNGAL MEDICATIONS. As CANCER. Doctors believe toxic epidermal necrolysis M. furfur is normal flora, tinea versicolor tends to develops when an external event triggers the recur in people who are susceptible to it. When mechanism for programmed cell death (apopto- recurrences are frequent, the dermatologist may sis), causing massive numbers of keratinocytes prescribe prophylactic antifungal therapy. (the cells that primarily comprise the skin) to die. See also VITILIGO. This in turn activates the body’s IMMUNE RESPONSE, which attacks the dying cells. The massive death tissue expansion A method for growing addi- of keratinocytes results in large segments of skin tional SKIN to use for autologous (self) skin grafts. sloughing off, leaving the underlying tissue Autologous grafts have the best rate of success exposed. Toxic epidermal necrolysis typically when transplanted because they are native to the evolves over a period of 10 to 14 days, though body and present no risk for graft rejection. Tissue once the skin eruptions begin deterioration is expansion is a common method for many recon- rapid. structive surgery procedures, though requires ade- Diagnosis is by skin biopsy, which shows the quate areas of healthy skin. characteristic pattern of cell destruction and abun- For tissue expansion, the surgeon makes a dance of killer T-cells. In most situations the first small incision to create a pouch or pocket in line of treatment is plasmapheresis, a process healthy skin and inserts a balloonlike pouch called somewhat similar to dialysis in which a mechani- a tissue expander. The surgeon then adds a small cal BLOOD separator removes the serum and amount of saline, through a special valve, every replaces it with donor serum. Plasmapheresis few days or so over a period of several months. helps clear antibodies from the serum, reducing The expander encourages the skin to grow to the immune response. Other treatments include cover it, slightly accelerating the rate of growth frequent surgical débridement of skin surfaces, over that which would normally occur. When the skin grafts to cover denuded surfaces, and precise new growth of skin reaches the desired surface fluid and electrolyte replacement. area, the surgeon removes the expander and can Toxic epidermal necrolysis has a survival rate harvest the skin to transplant elsewhere on the of about 60 percent. Those who survive often body. Tissue expansion grafts are highly successful have long-term complications and face a challeng- for repairing skin surfaces damaged or lost to ing road to rehabilitation and recovery. The mas- severe BURNS or injuries. Some HAIR TRANSPLANTA- sive loss of skin causes extensive scarring similar TION methods also use tissue expansion to grow to that of serious BURNS. The eyes also experience additional skin that contains healthy hair follicles. damage as the sloughing affects the conjunctiva As with any surgery, the primary risks associ- and sclera (EYE tissues). ated with tissue expansion are INFECTION and See also ADVERSE REACTION; ANTIBODY; HEMAPHERE- excessive bleeding. The tissue expander generally SIS; KERATINOCYTE; STAPHYLOCOCCAL SCALDED SKIN SYN- creates a conspicuous bulge in the surface of the DROME. skin, though the skin profile at the growth site returns to normal when the surgeon removes the urticaria The clinical term for hives, an outbreak expander. The surgeon uses appropriate tech- of wheals on the SKIN’s surface. Acute urticaria, niques to minimize scarring at the harvesting site which comes on suddenly, typically signals a as well as during placement of the new skin. HYPERSENSITIVITY REACTION. The wheals contain fluid 206 The Integumentary System the IMMUNE RESPONSE draws from the cells of the progressive form of urticaria. Angioedema can skin. They itch, often intensely (PRURITUS), and affect internal structures, causing pressure and may appear and recede in various locations on the swelling that affects the ability of vital organs to body (migration). function. When angioedema affects the airways it can cause BREATHING difficulties and ANAPHYLAXIS, BREATHING difficulties with urticaria the most serious hypersensitivity reaction. These may indicate ANAPHYLAXIS, a life-threat- complications occur only with repeat exposure to ening hypersensitivity reaction causing the substance causing the reaction. swelling of the airways that requires Urticaria represents an IMMUNE RESPONSE in emergency medical care. which the immune system releases IMMUNOGLOBU- LIN E (IgE), which causes mast cells to release HIS- When urticaria manifests, the first focus is on TAMINE. The histamine draws fluid into the tissues. subduing the response to relieve the symptoms Numerous drugs, foods, environmental factors and prevent complications. The doctor may such as pollen and animal dander, and health con- administer an EPINEPHRINE injection to thwart a ditions may cause urticaria. It is important to hypersensitivity response that appears to be inten- attempt to identify the causative factor to prevent sifying or if the urticaria progresses. Most urticaria recurrences. Hypersensitivity responses, which responds fairly quickly to ANTIHISTAMINE MEDICA- people also call allergic reactions, tend to intensify TIONS such as diphenhydramine (Benadryl) or with repeated exposure to the substance. hydroxyzine (Vistaril), which the doctor can A similar release of IgE occurs with chronic administer by injection for severe urticaria. The urticaria, as an immune-mediated response wheals generally retreat within 6 to 8 hours and related to serious illnesses that challenge the are entirely gone in about 36 hours with antihista- immune system such as cancer. AUTOIMMUNE DIS- mine therapy. Most people recover fully and can ORDERS that affect the connective tissue, such as avoid future episodes by avoiding exposure to the SYSTEMIC LUPUS ERYTHEMATOSUS (SLE), AMYLOIDOSIS, substance that caused the reaction. and RHEUMATOID ARTHRITIS, can also cause chronic Potential complications associated with urticaria urticaria, as can exposure to extreme heat or cold. are uncommon though can be life-threatening. As with acute urticaria, treatment for chronic ANGIOEDEMA occurs when fluid accumulates in tis- urticaria first targets symptom relief. sues other than the skin; most doctors consider it a See also DERMATITIS; MAST CELL; WHEAL. V

vesicle A small, blisterlike LESION on the SKIN that associated with ADDISON’S DISEASE (a disorder of contains serous fluid. Vesicles typically occur in the ADRENAL GLANDS), HYPERTHYROIDISM, DIABETES, clusters and indicate INFECTION, such as with HERPES and pernicious ANEMIA. SIMPLEX VIRUS (HSV), or irritation, such as results from contact with poison ivy. Skin vesicles often Symptoms and Diagnostic Path hurt or itch. Treatment may include topical med- In most people who develop vitiligo, the areas of ications to relieve discomfort, with oral ANALGESIC depigmentation generally appear slowly and start MEDICATIONS (PAIN relievers) or ANTIHISTAMINE MED- with small patches of skin. Some people do not ICATIONS (to relieve itching) as necessary. Vesicles develop more than a few such patches, while begin to recede and heal when the underlying cir- other people eventually develop large and numer- cumstance causing them begins to resolve. Vesicles ous patches of depigmentation. In most people, usually do not rupture or tear. During HEALING the the depigmentation is roughly symmetrical on body reabsorbs the serous fluid they contain, giv- both sides of the body, though in some people it ing the appearance that the vesicles wither away affects only one side. The appearance of the depig- until all that remains is a thin crust that eventu- mented areas is generally diagnostic as this is a ally falls off. unique symptom of vitiligo. The most common In other contexts within the human body, a sites for depigmentation are the face, hands, arms, vesicle is a small saclike or pocketlike structure in legs, and genitals. an organ, such as the seminal vesicles in the male Often there was a precipitating factor, such as a reproductive system. severe SUNBURN or other trauma to the skin, within See also BLISTER; BULLA. several months of the start of symptoms. Serious physical injury or illness may also precipitate vitiligo A condition of hypopigmentation in symptoms. The dermatologist may biopsy a repre- which melanocytes die in patches of SKIN, leaving sentative LESION to rule out other causes. Some- macules that are pale and depigmented. Dermatol- times blood tests will show the presence of ogists believe vitiligo is an autoimmune disorder antibodies, which strongly supports the diagnosis in which the IMMUNE SYSTEM produces antibodies of an autoimmune disorder. that attack melanocytes, the skin cells responsible for producing pigment. Vitiligo affects people of all Treatment Options and Outlook races and ethic backgrounds, though is more con- The cosmetic aspects of vitiligo are often the most spicuous in people who have darker skin. disturbing feature of vitiligo for people who have There appears to be no pattern to the presenta- the disorder, and most treatments target cosmetic tion of vitiligo, which may affect small areas or improvement. Most aim to slow the progression of nearly the entire skin surface. The depigmented the depigmentation or to darken the appearance areas have no other symptoms—that is, they do of depigmented areas and include topical CORTICO- not cause itching or PAIN. Vitiligo occurs more fre- STEROID MEDICATIONS, micropigmentation (thera- quently in people who have other AUTOIMMUNE peutic tattooing), and psoralen plus ultraviolet A DISORDERS such as ALOPECIA AREATA. Vitiligo is also (PUVA) PHOTOTHERAPY. Skin grafts are sometimes 207 208 The Integumentary System an option for small areas of depigmentation, tions that have similarly conspicuous symptoms, is though are expensive and entail numerous risks. the sense of social isolation and embarrassment Cosmetics to cover depigmented areas work well many people who have the condition feel. Vitiligo for some people. is especially difficult for adolescents and young Another therapeutic approach is to create adults to manage. Support groups are often help- hypopigmentation consistently, lightening all of ful for coping. the skin using topical bleaching agents such as monobenzone to make the depigmented areas less Risk Factors and Preventive Measures conspicuous. Such lightening is permanent, and Because dermatologists do not know what causes establishes heightened sensitivity to sun exposure vitiligo to start, there are few known preventive with the risk for severe sunburn. The functional measures. It does appear that significant trauma to disturbances to the skin also have significant the skin, such as a sunburn that blisters and peels, implications for health, as the depigmented areas can trigger vitiligo. Most dermatologists believe cannot protect from sun damage. Protective, full- GENE MUTATION is the underlying cause, as is the cover clothing and high sun-protection factor case with many autoimmune disorders, though (SPF) sunscreens are necessary to provide this researchers have yet to verify this. Limiting sun protection. exposure by wearing protective clothing and sun- In most people, vitiligo progresses despite screen may slow the progression of vitiligo. treatment. One of the most challenging dimen- See also ALBINISM; ANTIBODY; MACULE; MELANO- sions to vitiligo, as with other dermatologic condi- CYTE; TATTOOS. W–X wart A growth, typically rough and raised, that • electrodesiccation, which cauterizes or burns appears on the SKIN. The HUMAN PAPILLOMAVIRUS off the wart (HPV), which has numerous strains, causes com- • cantharidin, a topical chemical solution that mon warts as well as variations including genital forms a BLISTER which raises the wart from the warts (a common sexually transmitted disease) skin and plantar warts which appear on the soles • topical salicylic acid, which chemically destroys (plantar surfaces) of the feet. Because common the wart warts are viral, physical contact can spread them to other locations on the affected person’s body. Surgical remedies such as excision or laser ther- However, common warts rarely spread to other apy are effective and may be necessary for warts people. that resist other efforts, though they have substan- tially greater risks, including INFECTION and scar- Symptoms and Diagnostic Path ring. Oddly enough, an application of duct tape Most common warts begin with a small, rough, over the wart appears as successful as any other raised bumps that can be the same color as the therapy for causing common warts to resolve. surrounding skin or discolored (typically pale). As Most over-the-counter products for wart removal they grow they take on the characteristic appear- require multiple applications though are ulti- ance of warts. Small dark dots sometimes appear mately successful for those who are patient. inside the wart, which are clotted blood vessels Because they are viral, common warts tend to though people commonly call them wart seeds. recur for as long as the HPV remains in the body, The “seed” of the wart is the HPV, and it is not vis- and HPV is extraordinarily difficult to eradicate. ible. Warts seldom hurt or itch, though may do either as well as bleed when they are in locations Risk Factors and Preventive Measures that expose them to frequent irritation. The risk factor for common warts is exposure to HPV, which is pervasive. Preventive measures Treatment Options and Outlook include frequent and regular HAND WASHING and From a medical perspective, warts are harmless refraining from picking at or scratching existing and do not require treatment. Because common warts. Prompt treatment to remove warts while warts continue to spread, however, it is prudent to they are small and restricted to a fairly contained remove them when they are small and few. area helps to limit their spread. Though the health consequence of warts is prima- See also SCAR; SEBORRHEIC KERATOSIS; SEXUALLY rily cosmetic, warts that cluster in areas such as TRANSMITTED DISEASE (STD) PREVENTION; VIRUS. around the fingertips can create functional inter- ference. Common therapies the dermatologist may wheal A raised, blisterlike LESION on the SKIN that use for removing warts include usually results from an intradermal injection such as for allergy skin testing or the tuberculin skin • cryotherapy, such as treatment with liquid test. Wheals also may occur in response to insect nitrogen, which freezes the wart stings and topical allergic reactions (URTICARIA or 209 210 The Integumentary System hives). Wheals associated with urticaria typically melanin to shield the skin from ultraviolet radia- itch, sometimes intensely. Wheals usually do not tion. rupture or tear, and gradually fade to smooth, red For many people, wrinkles are cosmetically areas (macules) before disappearing entirely as the undesirable. Dermatologists offer a number of body absorbs the fluid they contain. solutions to reduce the appearance of wrinkles. See also BULLA; MACULE; PRURITUS. These include whitlow An INFECTION at the end of the finger, or • For a CHEMICAL PEEL, the dermatologist applies a less commonly the end of a toe, that contains pus caustic solution to the skin, causing the epider- and is very painful. The area is inflamed, enlarged, mis, and in a deep chemical peel the dermis, to erythematous (reddened), and often oozing. A slough away. The new skin that forms beneath common cause of whitlow is infection with the is tighter, pulling the surface of the skin HERPES SIMPLEX VIRUS (HSV), conveyed to the finger smooth. via contact with infectious secretions from oral • For DERMABRASION, the dermatologist mechani- herpes infections or genital herpes lesions. Some cally removes the top layers of skin (with local doctors use the terms whitlow and paronychia inter- Anesthesia), using a device similar to a small changeably, whereas others use whitlow to refer grinder or sander to strip away the epidermis. to HSV infection and paronychia to refer to bacte- rial infection. It is important to distinguish • For LASER SKIN RESURFACING, the dermatologist between the causes of the infection as the treat- uses a heat laser to “burn” away the top layers ment approach is different. Herpetic whitlow fea- of the skin. This technique allows the dermatol- tures the vesicles characteristic of HSV infection, ogist to precisely control the depth and extent and treatment is primarily to relieve symptoms. of skin removal as well as to target some areas Bacterial whitlow lacks vesicles and treatment for deeper penetration and others for lighter requires ANTIBIOTIC MEDICATIONS. penetration. See also ABSCESS; BACTERIA. • For BOTULINUM THERAPY, the dermatologist injects purified botulinum toxin into the muscles wrinkles Furrows or channels in the SKIN, typi- beneath the skin. This paralyzes them and cally resulting from repeated movements, such as keeps them from contracting. The paralysis facial expressions (for example, crow’s feet and keeps the person from forming wrinkles. Botu- laugh lines), or from long-term exposure to sun linum therapy lasts three to four months on and wind. Aging is the single-most significant fac- average, depending on the location and the tor that causes wrinkles. Wrinkles increase with person’s natural skin-aging tendencies. age as the skin loses collagen and subsequently resiliency. As well, the skin and the cutaneous tis- • For BLEPHAROPLASTY and RHYTIDOPLASTY, a sur- sue layer that supports it both thin, providing less geon performs cosmetic surgery operations to support. remove wrinkles and tighten the skin around People who have light-colored skin tend to the eyes (blepharoplasty) and the overall face have more wrinkles than people who have darker (rhytidoplasty). skin. Smoking ages the skin considerably, increas- ing the depth and number of wrinkles. Extensive Though it is not possible to totally prevent wrinkles may signal substantial sun damage that is wrinkles because they develop as a function of aging, it is possible to reduce their numbers and an alert for SKIN CANCER. Rapid or major weight loss also causes wrinkles, as the skin that stretched effects. Preventive measures include to accommodate the extra weight suddenly has no • drink plenty of water to keep the skin well underlying support so it sags, bags, and wrinkles. hydrated Prematurely wrinkled skin has less ability to pro- tect itself from the sun because its layers are thin- • use topical moisturizers and emollients to hold ner and contain fewer cells, which means less moisture in the skin xanthoma 211

• limit sun exposure, and wear protective cloth- ring on the shoulders and inner surfaces of the ing and sunscreen when outdoors arms, and often itch. The most significant feature of xanthoma is the • stop smoking and avoid exposure to environ- underlying lipid disorder, which signals increased mental cigarette smoke risk for CORONARY ARTERY DISEASE (CAD) and HEART • eat nutritiously, especially fruits and vegetables ATTACK. Many people who develop xanthomas that supply B vitamins and vitamin C, antioxi- have familial lipid disorders that result in unusu- dants that may help prevent skin damage due ally elevated levels of triglycerides and very low to sun exposure density lipoprotein cholesterol (VLDL-C) or low density lipoprotein cholesterol (LDL-C). These ele- Numerous over-the-counter products and vations are markers for serious CARDIOVASCULAR preparations purport to “cure” wrinkles. At best DISEASE (CVD) and require prompt medical treat- this is false advertising, as wrinkles are as ment. Lowering the blood lipid levels helps pre- inevitable as aging. However, products that add vent further xanthomas from developing, though moisture and vitamins to the skin may be has no effect on existing xanthomas. nonetheless beneficial for the skin. A xanthoma may create functional interference See also AGING, INTEGUMENTARY CHANGES THAT depending on its location. Xanthelasmas on or OCCUR WITH; ANTIOXIDANT; LENTIGINES; SMOKING CESSA- near the eyelids can interfere with proper vision, TION; SURGERY BENEFIT AND RISK ASSESSMENT. for example, and xanthomas on the hands may cause irritation and PAIN during tasks that require xanthoma A fatty deposit that forms a benign manual dexterity. Many people choose to have (noncancerous) LESION beneath the SKIN, though xanthomas removed for cosmetic purposes. Sev- also may occur in other tissues. Xanthomas eral options are available for removing xan- develop in people who have chronic, untreated thomas, including cryotherapy (freezing), HYPERLIPIDEMIA (elevated BLOOD cholesterol and electrodesiccation (cauterizing), excision (cutting triglycerides levels). In their most common form, out), and LASER SURGERY. The site usually heals xanthomas appear as yellowish blebs beneath the without scarring, although xanthomas tend to skin, typically rounded or oblong, that protrude as recur. nodules or papules. Xanthomas that form on the See also CHOLESTEROL BLOOD LEVELS; DIABETES; eyelids, a common presentation, are xanthelas- MEDICATIONS TO TREAT CARDIOVASCULAR DISEASE; NOD- mas. Most xanthomas do not cause symptoms ULE; PANCREATITIS; PAPULE; PRURITUS; RISK FACTORS FOR though may be cosmetically undesirable. Eruptive CARDIOVASCULAR DISEASE; TRIGLYCERIDE BLOOD LEVELS; xanthomas may occur in clusters, typically occur- XANTHELASMA. THE NERVOUS SYSTEM

The NERVOUS SYSTEM directs the functions, voluntary and involuntary, of the body through an intricate network of spe- cialized cells (neurons) that convey information in the form of electrochemical messages. Practitioners who diagnose and treat conditions of the nervous system are neurologists, neurosurgeons, and neuropsychiatrists. This section, “The Nervous System,” presents a discussion of the structure of the BRAIN and nerves, an overview of neurologic functions in health and the disorders that occur as a result of physiologic (organic) dysfunction of the brain and nerves, and entries about the health conditions that can affect neurologic function.

Conditions involving the nervous system often eleventh cranial nerve pair: iliohypogastric directly involve other body systems as well. Entries accessory ilioinguinal for neuromuscular disorders and neuropsychiatric twelfth cranial nerve pair: arm disorders in which the origins or symptoms are hypoglossal brachial primarily neurologic appear in this section, “The SPINAL CORD radial Nervous System.” Entries for neuromuscular dis- SPINAL NERVES musculocutaneous orders in which the origins or symptoms are pri- cervical (8 pairs, C1–C8) medial marily muscular appear in the section “The thoracic (12 pairs, T1–T12) ulnar Musculoskeletal System.” The section “Psychiatric lumbar (5 pairs, L1–L5) leg Conditions and Psychological Issues” contains sacral (5 pairs, S1–S5) femoral entries about disturbances of mood, emotion, per- coccygeal (1 pair, CO1) sciatic sonality, and mental health and illness. PERIPHERAL NERVES common peroneal trunk superficial peroneal Structures of the Nervous System phrenic deep peroneal MENINGES second cranial nerve pair: intercostal tibial dura mater optic arachnoid mater second cranial nerve pair: Functions of the Nervous System pia mater oculomoter The nervous system regulates and directs the BRAIN fourth cranial nerve pair: functions of the body, processing billions of bio- cerebral cortex (cerebrum) trochlear chemical messages—bits of information traveling ventricles fifth cranial nerve pair: between the brain and the body—every minute. It amygdala trigeminal is the earliest system to develop in the EMBRYO. hippocampus sixth cranial nerve pair: The cells that will become the nervous system thalamus abducens begin to separate and distinguish themselves HYPOTHALAMUS seventh cranial nerve pair: about 14 days after CONCEPTION. During the follow- corpus callosum facial ing 7 days, the neural tube, the rudiment of the cerebellum eighth cranial nerve pair: central nervous system, takes shape. By seven brainstem vestibulocochlear weeks of gestation, the neural tube has evolved pons ninth cranial nerve pair: into the SPINAL CORD and the brain. And by birth, medulla oblongata glossopharyngeal the nervous system is anatomically complete. CRANIAL NERVES tenth cranial nerve pair: The nervous system: organization and structure first cranial NERVE pair: olfactory vagus Organized into a number of structural and func- 212

The Nervous System 215 tional divisions, the nervous system operates so those operations. Right hemisphere lobe opera- efficiently that most of the time its myriad activi- tions tend to be spatial and conceptual, whereas ties take place virtually unnoticed. The nervous left hemisphere lobe operations tend to be linear system contains two major divisions: the CENTRAL and logical. Regions of the frontal lobes work NERVOUS SYSTEM and the PERIPHERAL NERVOUS SYSTEM. together to collect, assimilate, and integrate the The brain and spinal cord make up the central results. nervous system. The brain’s main divisions are the The cerebellum, a small structure at the back of cerebral cortex (cerebrum), cerebellum, and the brain, coordinates motor function (move- brainstem. The cerebral cortex is the largest and ment). It receives a constant flow information most complex part of the brain, accounting for 85 from the cerebral cortex, the basal ganglia (a col- percent of the brain’s mass and conducting all lection of nerve fibers on the basal, or bottom, functions of consciousness and voluntary action. surface of the cerebral cortex, where the planning The cerebral cortex filters, sorts, and manages and initiation of motor function takes place), the information about the body’s experiences in its brainstem, and the body about the body’s relation- external environment. It is the center of thought, ship to its external environment and sends in reason, intellect, emotion, judgment, personality, return a constant flow of instructions to seam- mood, behavior, and movement. The cerebral cor- lessly carry out tasks ranging from threading a tex also integrates many of the functions of other needle to running a marathon. Like the cerebral divisions of the nervous system and initiates vol- cortex, the cerebellum has two hemispheres but untary movement. operates ipsilaterally. The cerebellum manages balance, coordination, speed, direction, and the CEREBRAL DOMINANCE smoothness of movements. One or the other cerebral hemisphere is con- The brainstem, an elongated, bulbous structure tralaterally dominant in nearly everyone. The between the cerebral cortex and the spinal cord, most prominent feature of cerebral dominance is maintains the functions of survival and connects handedness. In about 85 percent of people, the the brain with the spinal cord. The primary struc- left hemisphere of the cerebral cortex is domi- tures of the brainstem are the pons, and midbrain, nant: they are right-handed (and usually right- medulla oblongata. The pons functions as a bridge footed and right-eyed). About 10 percent of connecting the cerebellum, the cerebral cortex, and people are right-hemisphere dominant: they are the spinal cord. The medulla oblongata is the segue left-handed (and usually left-footed and left- from the brain to the spinal cord. It is responsible eyed). About 5 percent of people appear to use for the beating of the HEART, BREATHING, BLOOD PRES- either side of the body with equal ease: they are SURE, BLOOD flow, and many reflexes (automatic, ambidextrous. survival-oriented reactions to environmental stim- uli). The 2nd through the 12th pairs of CRANIAL Structurally the cerebral cortex consists of two NERVES originate in the brainstem. Injuries to the matched halves: the right hemisphere and the left brainstem can be debilitating or fatal. hemisphere. A band of NERVE fibers, the corpus callosum, connects the two hemispheres at the BILLIONS AND BILLIONS OF BRAIN CELLS bottom of the deep fissure that separates them. At the completion of its structural development The functions of the hemispheres are contralateral just before birth, the BRAIN contains more than to the body—that is, the right hemisphere controls 100 billion neurons (NERVE cells) and about 50 the left side of the body and the left hemisphere times as many glial cells (cells that support the controls the right side of the body. Matching pairs neurons). The longest neuronal axons, the of lobes—frontal, temporal, parietal, and occipi- threadlike fibers that carry nerve impulses away tal—form the structure of each hemisphere, with from the NEURON, reach from the brain to the each lobe specializing in certain functions. Though base of the SPINAL CORD and extend nearly five each pair of lobes handles similar operations, the feet in an adult. right and left lobes conduct different aspects of 216 The Nervous System

The spinal cord, the body’s largest nerve, is the filaments that extend from its cell body. A single thoroughfare of communication between the such filament, the axon, extends from the cell brain and the body. It extends from the second body to carry nerve impulses from the neuron. cervical vertebra to the second lumbar vertebra, a From one to numerous other filamental processes, distance of about 20 inches in an adult. The bones the dendrites, branch from other sites on the cell of the spinal column, the vertebrae, enclose and membrane to capture nerve impulses coming to protect the spinal cord. The spinal cord controls the neuron. Like electrical wires, neurons would the reflexes of URINATION and defecation as well as “short” if they came into contact with each other. of MUSCLE stretch (the automatic responses of mus- Microscopic channels—synapses—help neurons cle cells that allow movement). keep safe distance from each other. Axons and All nervous system structures and functions dendrites reach toward, but do not touch, each outside the central nervous system belong to the other in the synapses. peripheral nervous system: the cranial nerves, the spinal nerves, and their numerous branches. The WHITE MATTER AND GRAY MATTER 12 paired cranial nerves arise from the base of the A fatty substance, myelin, coats most axons to brain and the brainstem. They convey sensory and insulate and protect them. The myelin gives the motor signals to and from the structures of the axons a whitish color. NERVE tissue in the BRAIN head and face, one of each pair going to each side. and SPINAL CORD, which is primarily a collection The 31 paired spinal nerves branch from the of axons, is white matter. The cell bodies of neu- spinal cord at each vertebra, carrying sensory and rons are dark and grayish in color. Nerve tissue motor signals to and from the rest of the body. in the brain and spinal cord that is primarily a Within the peripheral nervous system are two collection of NEURON cell bodies is gray matter. main subdivisions: the somatic nervous system, which handles voluntary functions such as move- Electrically charged chemical molecules— ment, and the autonomic nervous system, which ions—are within and surround a neuron. Among handles involuntary functions such as digestion. the significant ions, sodium, potassium, and cal- The autonomic nervous system has two further cium are positive ions and chloride is a negative subdivisions. The sympathetic nervous system is ion. Microscopic channels in the neuron’s cell made up of the nerves that serve the structures of membrane, called ion channels, selectively allow the main trunk (thoracic and lumbar regions). The ions to enter and leave the neuron. Each ion parasympathetic nervous system is made up of the channel is specific for an ion—that is, calcium ion nerves that serve the neck and head and the sacral channels allow passage only of calcium ions and region of the trunk. sodium ion channels allow passage only of sodium ions. When a neuron is at rest, the total charge of DIVISIONS OF THE NERVOUS SYSTEM the ions within its membrane is negative relative CENTRAL NERVOUS SYSTEM: BRAIN and SPINAL CORD to the ions outside its membrane. As well, there PERIPHERAL NERVOUS SYSTEM: cranial nerves, SPINAL NERVES, and are more potassium ions within the cell body and their branches more sodium ions outside the cell. • somatic NERVOUS SYSTEM: voluntary functions When a stimulus triggers an electrical impulse, • autonomic nervous system: involuntary functions the first stage of neuronal communication, the † sympathetic nervous system: main trunk impulse causes sodium ion channels to open. † parasympathetic nervous system: head and sacral region Sodium ions rush into the neuron cell body, changing the neuron’s polarity to become positive Nervous system communication: neurons, ions, relative to the surrounding environment. The and neurotransmitters The basic structure of electrical impulse rides the wave of polarity down function in the nervous system is the neuron, a the axon of the sending neuron. About the time specialized cell capable of sending and receiving the impulse reaches the presynaptic terminals at electrochemical impulses that initiate or inhibit the end of the axon, potassium ion channels open actions. What makes the neuron special are the and potassium enters the cell body. In exchange, The Nervous System 217 because only so many ions can be inside the cell tates neuron communication in areas of the brain body, sodium ions leave. To restore itself to nega- related to mood. The acetylcholinesterase tive polarity the cell body activates a burst of inhibitors, medications to treat ALZHEIMER’S DIS- energy to “pump” more sodium ions out, at an EASE, work by blocking the enzyme that breaks exchange rate of three sodium ions out for every down the neurotransmitter acetylcholine. This two potassium ions in. action extends the presence of acetylcholine in the Meanwhile, back at the synaptic terminals synapses, increasing neuroreceptor binding. another conversion is taking place. The synaptic Acetylcholine facilitates neuron communication in terminals contain tiny storage pockets called vesi- areas of the brain that process cognitive functions cles that hold NEUROTRANSMITTER molecules. The and memory. Medications may also masquerade electrical impulse causes the synaptic vesicle to as neurotransmitters to bind with neuroreceptors. release a neurotransmitter molecule. The neuro- Therapies for PARKINSON’S DISEASE, a degenerative transmitter molecule crosses the synapse and condition that results from depletion of the neuro- binds with a NEURORECEPTOR on a dendrite of the transmitter DOPAMINE in the brain, are among the receiving neuron. The binding either causes or most effective applications of this approach. blocks an action. The longer the neurotransmitter molecules Health and Disorders of the Nervous System remain in the synapse the more neuroreceptors The most significant health risks the nervous sys- they can bind. As a safety mechanism, the neuro- tem faces occur before birth. The most vulnerable transmitter’s presence in the synapse stimulates period in nervous system development takes place the synaptic vesicles to reuptake (recycle) the before most women have missed a menstrual remaining neurotransmitter, containing the period or suspect they are pregnant. Within the potential for binding. Further stimuli are then first three weeks after conception, the rudimen- necessary to continue. The neuron sending a mes- tary nervous system, the neural tube, forms and sage is the presynaptic neuron; the neuron receiv- rapidly differentiates into the brain and spinal ing a message is the postsynaptic neuron. Some cord. Numerous factors, environmental and neurologic conditions affect the functioning of genetic, can disrupt this process to cause cephalic presynaptic neurons and others affect the func- disorders (structural defects of the brain) or SPINA tioning of postsynaptic neurons. BIFIDA (structural defects of the spinal cord). CERE- BRAL PALSY is the most common developmental dis- NEURONAL PATHWAYS: turbance of the nervous system. THE BRAIN’S ENDLESS CAPACITY TO LEARN The adult BRAIN contains 60 to 200 trillion FOLIC ACID AND NEURAL DEVELOPMENT synapses. Synapses represent the networks of Folic acid is crucial for proper development of axons that neurons develop to form neuronal the NERVOUS SYSTEM early in PREGNANCY, especially pathways, the routes by which neurons commu- at the time of CONCEPTION through the first nicate with one another in expedited fashion. trimester. Numerous studies show that taking Even though all the neurons the brain will ever folic acid supplements before and during preg- have are present at birth, the brain has an end- nancy can prevent 70 percent of NEURAL TUBE less capacity to create new neuronal pathways DEFECTS. Health experts recommend that all and thus “grow” its ability to learn. women of childbearing age take 400 micrograms of folic acid supplement daily regardless of Many medications work by inhibiting (block- whether they are trying actively to become preg- ing) or expediting the reuptake process to extend nant. or shorten, respectively, the time the neurotrans- mitter is active. Selective serotonin reuptake From birth through midlife, injury becomes the inhibitors (SSRIs), for example, are ANTIDEPRESSANT most worrisome threat to the nervous system. MEDICATIONS that work by blocking serotonin reup- Young people are especially vulnerable to TRAU- take. Serotonin is a neurotransmitter that facili- MATIC BRAIN INJURY (TBI) and SPINAL CORD INJURY; 80 218 The Nervous System percent of spinal cord injuries occur in people who extent of creating brain dysfunction (ENCEPHALOPA- are between the ages of 15 and 30. Many of these THY). Health conditions that directly affect the ACCIDENTAL INJURIES are preventable. Many of the nervous system also become more frequent with illnesses that threatened not only nervous system increasing age. The most common—and dis- function but often life itself—POLIOMYELITIS, abling—such conditions are Alzheimer’s disease, ENCEPHALITIS, MENINGITIS—in previous generations Parkinson’s disease, and DEMENTIA. Alzheimer’s dis- are now either preventable or treatable. ease alone affects as many as 50 percent of people age 85 and older. HEALTH CONDITIONS Traditions in Medical History INVOLVING THE NERVOUS SYSTEM The earliest medical writings of Eastern and West- ALZHEIMER’S DISEASE AMYOTROPHIC LATERAL SCLEROSIS ern physicians document nervous system condi- APHASIA (ALS) tions such as epilepsy (SEIZURE DISORDERS) and APRAXIA ATAXIA surgical treatments that involved boring through ATHETOSIS AUTISM the skull, probably to relieve pressure resulting BELL’S PALSY BRAIN TUMOR from head trauma. Healed wounds in skulls, BRAIN HEMORRHAGE CEREBRAL PALSY clearly made by intent, remain as archaeological CHOREA cognitive dysfunction evidence that physicians of antiquity were some- CONCUSSION DELIRIUM what sophisticated, as well as successful, in their DEMENTIA developmental disabilities methods. Mummified remains reveal that DYSKINESIA ENCEPHALITIS poliomyelitis—which approached worldwide erad- ENCEPHALOPATHY GUILLAIN-BARRÉ SYNDROM ication in 2005 through vaccination efforts, with HEADACHE HERNIATED NUCLEUS PULPOSUS the exception of a few pockets where the disease HUNTINGTON’S DISEASE HYDROCEPHALY remained endemic—was fairly common among LEARNING DISORDERS memory impairment ancient Mesopotamians and Egyptians. MENINGITIS MULTIPLE SCLEROSIS The Greek physician and philosopher Hip- MYASTHENIA GRAVIS MYOCLONUS pocrates, the father of modern medicine, was the MYOTONIA NARCOLEPSY first to determine the brain’s responsibility for NEURALGIA NEURAL TUBE DEFECTS consciousness and control of the body. The inabil- NEURITIS NEUROFIBROMATOSIS ity to directly explore the structure and function NEUROPATHY ORGANIC BRAIN SYNDROME of the brain resulted in centuries of misunder- PARALYSIS PARESTHESIA standings, however. The first accurate representa- PARKINSON’S DISEASE POLIOMYELITIS tions emerged when in 1543 Andreas Vesalius RESTLESS LEGS SYNDROME SEIZURE DISORDERS (1514–1564) published the landmark manuscript SPINA BIFIDA SPINAL CORD INJURY De humani corporis fabrica libri septum, more famil- TIC TOURETTE’S SYNDROME iarly known today as The Fabric of the Human Body. TRAUMATIC BRAIN INJURY (TBI) TREMOR DISORDERS The manuscript presented the first drawings of the human brain based on dissection and physical Systemic health conditions shift to the forefront examination. of concern with the approach of late age. CARDIO- VASCULAR DISEASE (CVD), endocrine disorders, pul- Breakthrough Research and Treatment Advances monary disease, and disorders of METABOLISM Today some of the greatest advances in under- arising from LIVER and kidney disease become standing of brain and nervous system structure more prevalent with advancing age. All of these and function come from research in genetics and conditions have the potential to affect nervous molecular medicine. HUNTINGTON’S DISEASE was one system function. STROKE, a consequence of cardio- of the first neurologic disorders for which vascular disease, is the leading cause of disability researchers established a conclusive genetic foun- resulting from damage to the brain. Metabolic dis- dation. In the 1990s researchers uncovered muta- orders such as chronic CIRRHOSIS and DIABETES may tions in genes responsible for Parkinson’s disease, disrupt the body’s biochemical balances to the Alzheimer’s disease, and Lewy body dementia. The Nervous System 219

There is great hope that such discoveries will lead insights into the processes of memory and cogni- to effective treatments for these and other degen- tive function and offer an objective means for erative neurologic conditions. assessing the effectiveness of therapeutic Other research focuses on replacing lost or approaches for neurologic disorders such as damaged nervous system tissue. STEM CELL trans- Alzheimer’s disease, Parkinson’s disease, and plantation, still experimental, shows promise for seizure disorders. treating conditions such as Parkinson’s disease, In the 1980s scientists discovered the brain has Alzheimer’s disease, MULTIPLE SCLEROSIS, AMY- the ability to reorganize the way it functions to OTROPHIC LATERAL SCLEROSIS (ALS), and spinal cord some degree, allowing different areas of the brain injury. Researchers are also combining GENE and to take over for certain areas that become dam- molecular technologies to cultivate neurons in the aged. Whether this process permits the brain to laboratory with the hope of providing additional default to abandoned pathways or to create new sources of transplantable cells. pathways remains unknown. Researchers con- Other breakthroughs involve new understand- tinue to explore the mechanisms of this reorgani- ing about how the brain functions. Highly sophis- zation, hopeful that further discoveries will lead to ticated imaging technologies such as POSITRON therapies to retrain the brain after stroke or trau- EMISSION TOMOGRAPHY (PET) SCAN and SINGLE PHOTON matic brain injury and perhaps to compensate for EMISSION COMPUTED TOMOGRAPHY (SPECT) SCAN allow functional losses due to disease processes such as researchers to observe changes in the brain during those that occur with multiple sclerosis and brain activity. Such observations have provided Alzheimer’s disease. A aging, neurologic changes that occur with A nerve impulses to and from the body throughout rudimentary NERVOUS SYSTEM is among the first life. structures to form as a new life begins. The CEN- TRAL NERVOUS SYSTEM begins to form about two The Early Childhood Nervous System weeks after CONCEPTION, arising from a cluster of The brain continues to add new cells at an aston- specialized cells called the ectoderm. Its physical ishing rate, doubling in size from birth by the time and functional development is about 60 percent a child reaches 18 months of age. Intense learning complete by birth, 80 percent complete by age takes place during this period, during which the three, and finally reaches completion at the end of brain acquires the foundations of language, sen- ADOLESCENCE. Though the full complement of neu- sory interpretation, and motor skills. Interruptions rons is in place by early childhood, the BRAIN con- of these processes can have serious and lifelong tinues to establish new pathways for NEURON consequences. Studies with animals show, for communication for most of life. example, that depriving the brain of visual input during the time the brain is establishing the path- The Prenatal Nervous System ways for interpreting visual signals results in per- The first recognizable neurologic structure is manent blindness even though the structural apparent 21 days after conception when the cells components of vision—the EYE, OPTIC NERVE, and of the ectoderm grow and divide to form the neu- brain regions—are intact. ral tube, a primitive structure of NERVE tissue. Over Throughout childhood brain neurons continue the following four weeks the neural tube elon- to expand the connections they make with each gates and closes at each end to form the SPINAL other, laying down the hundreds of thousands of CORD and the brain, a process called neuronal pathways necessary for learning and remember- migration. This is one of the most sensitive times ing. These neuronal networks provide shortcuts in embryonic development. NEURAL TUBE DEFECTS— that allow the brain to carry out familiar functions such as SPINA BIFIDA and anencephaly, which result with great speed and efficiency. The foundations when one or the other end of the neural tube fails of language and motor movement develop and to close—are among the most common BIRTH evolve during this period of expansion. Though DEFECTS involving the nervous system. researchers agree it is never to late for the brain to The brain grows by 50,000 neurons a second learn, it is during the years of childhood that the during most of this migration period, forming the brain is most receptive. brain’s three major divisions—prosencephalon (forebrain), mesencephalon (midbrain), and The Adolescent Nervous System rhombencephalon (hindbrain)—which themselves During adolescence (between the ages of 12 and grow and divide to form the core structures of the 20) axons continue to grow and branch, most brain. From the spinal cord, the SPINAL NERVES and notably from the neurons of the frontal lobes, PERIPHERAL NERVES begin to tendril out to the which are responsible for many of the functions of organs and structures of the body, establishing cognition and behavior, and to lesser extent from motor and sensory innervations that will carry neurons in other areas of the brain. This is the 220 Alzheimer’s disease 221

final stage of functional organization of the brain’s culling that helps the brain maintain its efficiency. processes and mechanisms. The numbers of neu- By old age the cumulative effect of this cell death roreceptors on the surfaces of neurons also results in decreased brain tissue. Imaging proce- increase dramatically, particularly those for dures such as MAGNETIC RESONANCE IMAGING (MRI) DOPAMINE which is the primary brain NEUROTRANS- show the ventricles (spaces) are larger in the brain MITTER for functions of cognition and behavior. of a 70-year-old person than a 30-year-old person. This axonal growth makes the adolescent brain The numbers of sensory nerve receptors in the especially vulnerable to the neurotoxic effects of body (peripheral nerve structures) also begin to ALCOHOL and drugs. Damage that disrupts axonal decline, reducing to some extent the sensory input growth during adolescence often has complex and that reaches the brain. permanent, consequences for brain function dur- But these changes are not sufficient, in them- ing the rest of life. selves, to significantly diminish the brain’s func- tions. Indeed, recent research suggests the brain The Elderly Nervous System gets “smarter” with age, developing shortcuts and The brain remains capable of carrying out its func- efficiencies in the ways that it processes informa- tions across the lifespan unless injury or disease tion. Many people reach age 80 and beyond with interrupts. But by old age the likelihood of injury, relative good memory, cognition, and independ- disease, and general health problems is higher ence. Though physical changes do take place in than any other stage of life. Many diseases com- the brain with aging, researchers believe neuro- mon in old age affect the brain and nervous sys- logic deficiency is not inherently a normal dimen- tem even when they primarily involve other body sion of aging. systems. CARDIOVASCULAR DISEASE (CVD), for exam- See also CEREBRAL PALSY; COGNITIVE FUNCTION AND ple, may change the BLOOD flow to the brain. DYSFUNCTION; FETAL ALCOHOL SYNDROME; MEMORY AND HYPERTENSION (high BLOOD PRESSURE), one of the MEMORY IMPAIRMENT. most common forms of cardiovascular disease, is the leading cause of STROKE; and stroke is the lead- Alzheimer’s disease A progressive, degenerative ing cause of disabling brain injury. DIABETES dam- condition that causes irreversible loss of cognitive ages the delicate blood vessels that nourish the and memory functions. The hallmarks of the dis- peripheral nerves, most notably damaging sensory ease are the diminished production of acetyl- perception—the ability of distant body parts such choline, a NEUROTRANSMITTER essential for cognitive as the feet to send PAIN signals to the brain function, and the formation of amyloid plaques (peripheral NEUROPATHY). Chronic CIRRHOSIS creates (abnormal protein deposits) and neurofibrillary widespread metabolic imbalances in the body that tangles (resulting from another protein, tau), alter brain functions from cognition to motor within the BRAIN. These formations interfere with movement (hepatic ENCEPHALOPATHY). normal NEURON communication and literally The likelihood of neurologic disease also “scramble” NERVE signals. Alzheimer’s disease is increases with age. Conditions such as ALZHEIMER’S typically a condition of aging, primarily affecting DISEASE, PARKINSON’S DISEASE, HUNTINGTON’S DISEASE, people age 70 and older, though an early-onset DEMENTIA, CREUTZFELDT-JAKOB DISEASE (CJD), TREMOR form of the disease may strike people who are in DISORDERS, and ORGANIC BRAIN SYNDROME seldom their 40s or 50s. Early-onset Alzheimer’s disease develop in people under the age of 50. As many as tends to progress more rapidly. More than 4 mil- half those age 85 and older have Alzheimer’s dis- lion Americans have Alzheimer’s disease. ease, however. Progressive neurologic conditions The causes of Alzheimer’s disease remain that begin earlier in life, such as MULTIPLE SCLEROSIS, unclear, though GENE MUTATION is emerging as a tend to exhibit the most severe of their symptoms leading candidate. In the 1990s researchers corre- as age advances. Such changes are generally irre- lated mutations in the apolipoprotein E (apoE) versible. gene on CHROMOSOME 19 with the tendency, Neurons, like other cells, die throughout life. depending on the ALLELE (form of the gene) inher- Researchers believe such cell death is a form of ited, to develop Alzheimer’s disease in old age. 222 The Nervous System

People with one allele pairing appear less likely to • stops speaking in the middle of sentences or develop the disease, and those with other allele conversations pairings seem more likely. Researchers believe there are other genes that may affect a person’s Later symptoms become more pronounced and GENETIC PREDISPOSITION for Alzheimer’s disease, limit independent functioning. Later symptoms of though developing the disease is an interaction Alzheimer’s disease include among environmental factors, such as the individ- ual’s overall health status and lifestyle habits, and • DEMENTIA genetic factors. • forgetting to eat or drink Early-onset Alzheimer’s disease, in which • engaging in socially inappropriate behavior symptoms appear before the age of 60 (often in such as public MASTURBATION the 40s and 50s), is the only form of Alzheimer’s disease researchers know for certain is hereditary. • disorientation It occurs as a result of mutated genes on chromo- • inability to recognize people and places and somes 1, 14, and 21 that cause alterations in pro- sometimes self teins that have key functions in the brain in regard to regulating amyloid. The mutations occur The diagnostic path includes a comprehensive in an autosomal dominant INHERITANCE PATTERN, medical examination, thorough NEUROLOGIC EXAMI- which means each child of a person who has the NATION, ELECTROENCEPHALOGRAM (EEG), and usually gene mutation has a 50 percent chance of inherit- imaging procedures such as COMPUTED TOMOGRAPHY ing the gene. In this form of Alzheimer’s disease, (CT) SCAN to rule out other possible causes (such as also called familial Alzheimer’s disease, it appears BRAIN TUMOR or STROKE) that could cause the symp- that inheriting any one of the mutated genes toms. establishes the certainty of developing the disease. Diagnosis of Alzheimer’s disease is primarily Researchers are sure that variables of personal clinical, as only examination of brain tissue at health play a significant role in whether any given autopsy following death can provide definitive evi- individual develops the disease, though they do dence of the hallmark amyloid plaques and neu- not yet know what those variables are. rofibrillary tangles. The person’s age, the gradual progression of symptoms, and ruling out other pos- Symptoms and Diagnostic Path sible causes of the symptoms lead the neurologist to Early symptoms of Alzheimer’s disease tend to be the diagnosis of Alzheimer’s disease. POSITRON EMIS- vague and inconsistent deviations from the SION TOMOGRAPHY (PET) SCAN and SINGLE-PHOTON EMIS- known and familiar. Though memory loss is the SION TOMOGRAPHY (SPECT) SCAN often can show the most familiar symptom, it is more than simply progression of damage within the brain as misplacing one’s car keys or forgetting an appoint- Alzheimer’s disease advances. This can help con- ment. A person may travel the same route to and firm the diagnosis and monitor the effectiveness of from the store, for example, and then become medications in slowing the deterioration. completely lost. Early symptoms that can suggest Alzheimer’s disease include Treatment Options and Outlook In the 1990s the US Food and Drug Administra- • confusion when following directions tion (FDA) approved a new class of drugs, acetyl- • forgetting familiar people and places cholinesterase inhibitors, to treat Alzheimer’s disease. These drugs, such as donepezil (Aricept) • inability to write a check or count out money and rivastigmine (Exelon), prevent the enzyme to pay for purchases acetylcholinesterase from metabolizing (breaking • repeatedly asking the same questions or telling down) acetylcholine. This action extends the the same information length of time acetylcholine remains available to • inability to prepare meals or perform common neurons, compensating to a certain degree for the household tasks diminishing amounts of acetylcholine the brain amyotrophic lateral sclerosis (ALS) 223 produces as Alzheimer’s disease progresses. Even- Risk Factors and Preventive Measures tually acetylcholine production drops below the Age is the primary risk factor for Alzheimer’s dis- level at which extending its presence is useful, ease. Though researchers have investigated however, making these medications most effective numerous apparent correlations between environ- in the early to middle stages of the disease. mental exposures (such as to aluminum) and There is some evidence that GINKGO BILOBA, a Alzheimer’s disease, they have not been able to botanical supplement, improves the cognitive and substantiate them. Genetic factors are likely signif- memory symptoms of early to middle Alzheimer’s icant contributors. Except for early-onset disease in some people. Ginkgo biloba has no Alzheimer’s disease, however, the role of the known effect on neurotransmitters directly; its genetic component of Alzheimer’s disease remains action appears to be that it improves the circula- uncertain. Researchers discovered in the early tion of BLOOD throughout the brain. This possibly 2000s that people taking statin medications (such broadens the areas of the brain that participate in as lovastatin) to lower blood cholesterol levels cognitive functions. However, ginkgo biloba also have a much lower rate of Alzheimer’s disease affects COAGULATION (the processes of clotting). than people who do not take these medications, People who take anticoagulant medications, and they continue to investigate what correlations including daily ASPIRIN THERAPY, should not take may exist. ginkgo biloba unless their doctors approve and At present, however, there are no measures determine there are no interactions likely with known to prevent Alzheimer’s disease. Because prescribed medications. environmental factors such as overall personal Other treatments for Alzheimer’s disease are health, nutrition, and lifestyle likely contribute in primarily supportive and may include OCCUPA- some fashion to conditions that allow Alzheimer’s TIONAL THERAPY to provide methods for maintaining disease to develop, health experts encourage cognitive function and memory for as long as pos- nutritious EATING HABITS, daily physical activity, and sible. Activities that use these functions, such as other lifestyle measures to maintain optimal crossword puzzles and reading, seem helpful. health. Some studies show that daily physical exercise, See also AGING, NEUROLOGIC CHANGES THAT OCCUR such as walking, slows the progression of WITH; COGNITIVE FUNCTION AND DYSFUNCTION; LIFESTYLE Alzheimer’s disease, though the mechanisms AND HEALTH; MEMORY AND MEMORY IMPAIRMENT. through which it may do so remain unknown. Alzheimer’s disease is challenging and emotion- amnesia See MEMORY AND MEMORY IMPAIRMENT. ally draining for family members and friends who participate in caregiving. Most people want to amyotrophic lateral sclerosis (ALS) A progres- maintain their loved ones at home for as long as sive, degenerative disorder in which motor neu- possible, such that it often takes a traumatic event rons (NERVE cells in the SPINAL CORD that are to force the recognition that the person requires responsible for movement) die, resulting in loss of more extensive care. Specialized Alzheimer’s care voluntary MUSCLE function. ALS does not affect facilities provide the staffing and environment to involuntary muscle function or other neurologic keep the person with Alzheimer’s disease safe. structures. Other names for ALS include Lou SUPPORT GROUPS for family members and caregivers Gehrig’s disease, Charcot’s disease, and motor NEU- provide forums for sharing information and RON disease. ALS affects half again as many men as understanding. Because Alzheimer’s disease is women and typically appears in people who are progressive and incurable, it is important for fami- between the ages of 40 and 60. lies to discuss key END OF LIFE CONCERNS with the Though ALS ultimately affects all voluntary person before impairment becomes significant. muscle function, it typically begins in one of the Most people prefer to make decisions about their three types of motor neurons: own care and are more comfortable when they can feel confident their desires will shape the care • upper motor neurons, which regulate volun- they receive. tary muscle function in the upper extremities 224 The Nervous System

• lower motor neurons, which regulate voluntary other causes of the symptoms. There are no defin- muscle function in the lower extremities itive diagnostic tests for ALS. • bulbar motor neurons, which affect the func- LOU GEHRIG’S DISEASE tions of structures in the BRAIN that regulate coordination of movement throughout the Amyotrophic lateral sclerosis (ALS) struck Ameri- body can baseball legend Lou Gehrig (1903–1941) at the height of his record-setting career. After As motor neurons die the muscles they control Gehrig struggled for more than a year with the can no longer function. As ALS progresses and progressive loss of neuromuscular function char- muscle cells become inactive, the muscles atrophy acteristic of ALS, doctors made the diagnosis. (waste away). These events in combination result Gehrig remained a public figure even as his in the debilitating loss of mobility. Regardless of the health deteriorated, drawing attention to the dis- disease’s point of origin, it eventually affects all vol- ease that finally claimed his life at the age of 38. untary muscles in the body. Because the bulbar Americans more familiarly know ALS as Lou structures in the brain additionally have functions Gehrig’s disease. However, French neurologist related to emotion, loss of emotional control is also Jean-Martin Charcot (1825–1893) first described common particularly in the disease’s later stages. the symptoms of this rare condition in 1869. Researchers do not know what causes motor neu- Doctors in France and much of Europe refer to rons to die, nor do they know the precise mecha- ALS as Charcot disease. nisms by which cell death occurs. Treatment Options and Outlook Symptoms and Diagnostic Path At present treatment for ALS is primarily support- The development of symptoms varies with the ive; there is no cure. The medication riluzole, first location of motor neuron loss. Early symp- which blocks release of the NEUROTRANSMITTER glu- toms of ALS are generally vague, sporadic, and tamate, often can slow the progression of symp- asymmetrical (one-sided). Among them are toms. Glutamate stimulates activity in the brain, which correspondingly increases nerve signals to • muscle cramps parts of the body such as the muscles. People who • emotional inappropriateness and lability (mood have ALS tend to have elevated blood levels of swings) glutamate, and some research suggests glutamate overstimulation may damage motor neurons. • difficulty speaking, notably slurred speech Researchers do not know what causes the eleva- • excessive salivation (SIALORRHEA) and difficulty tion, however, or whether it contributes to or swallowing results from the ALS. The neurologist may prescribe other medications such as baclofen Symptoms gradually progress, often over the and tizanidine to treat muscle spasms and anti- course of several years, to a level at which they cholinergic medications to control excessive sali- interfere with normal activities. The diagnostic vation. path generally starts with BLOOD tests to assess thy- The progressive loss of muscle control eventu- roid and parathyroid function and to detect any ally affects vital functions such as swallowing, presence of heavy metals, notably lead. HYPERTHY- which affects the ability to eat, and BREATHING. ROIDISM, HYPERPARATHYROIDISM, and lead poisoning Important treatment decisions as ALS progresses can cause symptoms similar to those of ALS. The include choices around the insertion of a perma- diagnostic path also includes electromyography nent feeding tube, called a percutaneous endo- (EMG) to assess muscle function in affected as scopic gastrotomy (PEG) tube, to provide adequate well as unaffected limbs. The neurologist may fur- nutrition and assistive breathing devices, including ther conduct diagnostic imaging procedures of the MECHANICAL VENTILATION. Some people who have brain and spinal cord, such as MAGNETIC RESONANCE ALS choose full support to extend life as long as IMAGING (MRI) of the cervical spine, to rule out possible and others opt for only those supportive apraxia 225 measures that provide the QUALITY OF LIFE that is ities to speak, read, write, and understand lan- acceptable to them. Treatment decisions are guage. uniquely individual. In most people the left brain contains the func- About 40 percent of people who have ALS live tional centers responsible for speech and language, 5 to 10 years after diagnosis, and 10 percent sur- so stroke or other injury affecting the left brain vive longer than 10 years. Pulmonary failure and may produce aphasia, ranging from limited (cer- its complications are usually the cause of death. tain kinds of words or expressions) to global (com- Because ALS is a fatal disease, those who have it plete inability to communicate through language). should discuss their treatment preferences and END These functional centers conduct all brain activity OF LIFE CONCERNS with their physicians and family related to language concepts, including expression members, and establish their desires in writing such as through SIGN LANGUAGE, not only through through advance directives such as medical power speech. Severe damage to these centers appears to of attorney and living will. prevent the person also from engaging in pan- tomime and other methods of communication, Risk Factors and Preventive Measures creating significant disability. ALS appears to be familial (hereditary) in about People with mild to moderate aphasia typically 20 percent of people who develop it, occurring in have difficulty articulating and understanding the an autosomal dominant INHERITANCE PATTERN. Neu- correct words for objects and activities as well as rologists classify the remaining 80 percent as spo- in structuring words they do understand into sen- radic. Family history is the strongest individual tences. Speech and language therapy can help risk factor for developing ALS. Epidemiologists can people with mild to moderate aphasia use their identify trends in which pockets of ALS occur, remaining language functions to their best ability suggesting there are common risk factors for spo- and learn alternate means of expression. Family radic ALS. As yet no clear evidence has emerged and friends can assist by developing mechanisms that identifies these risk factors or that establishes for interpreting and understanding the person’s any explanation for why only a small percentage expressions. of people exposed to the same circumstances See also APRAXIA; ATAXIA; SPEECH DISORDERS. develop ALS. Some research suggests ALS may have components of autoimmune and mitochon- apraxia The inability to engage in learned pat- drial dysfunction, though the causes and mecha- terns of voluntary MUSCLE activity though the nisms of ALS remain unknown. There are no capability (muscle function) is present. Apraxia, known measures to prevent ALS. also called dyspraxia, may affect various functions See also APOPTOSIS; AUTOIMMUNE DISORDERS; and tasks that require voluntary muscle activity. CRAMP; GUILLAIN-BARRÉ SYNDROME; HEAVY-METAL POI- Among them speaking (verbal apraxia, sometimes SONING; MITOCHONDRIAL DISORDERS; MULTIPLE SCLERO- called apraxia of speech), clapping hands or brush- SIS; MYASTHENIA GRAVIS; SPASM; STROKE. ing the TEETH (limb apraxia), swallowing or whistling (buccofacial apraxia), using implements aphasia Loss of the ability to use language. such as eating utensils or hand tools (motor Aphasia results from damage to the areas of the apraxia), and moving the eyes to follow an object BRAIN responsible for language, often due to (occulomotor apraxia). Verbal apraxia is the most STROKE. Because these areas of the brain are func- common form of this neurologic disorder. tional rather than structural, doctors cannot pre- dict the extent to which injury will affect Verbal Apraxia in Children language. Other causes of aphasia include BRAIN Developmental verbal apraxia in children results TUMOR and TRAUMATIC BRAIN INJURY (TBI). Aphasia from injury, often unidentified as to its nature and sometimes occurs in the later stages of neurode- cause, to the BRAIN regions and neural pathways generative disorders such as ALZHEIMER’S DISEASE that produce speech. Verbal apraxia begins to and PARKINSON’S DISEASE. It may involve any indi- show symptoms between the ages of 18 and 30 vidual aspect or combination of aspects of the abil- months, the age in normal development at which 226 The Nervous System a child has acquired a vocabulary of several dozen SCAN to identify the area of injury as well as to to several hundred words and can speak in simple determine, when unknown, the cause of the sentences. Symptoms of verbal apraxia include injury. Aggressive speech therapy may improve speech over time. However, severe apraxia, espe- • unable to shape the lips and MOUTH to form cially when coupled with muscle weakness, may words not respond to treatment. In such circumstances • appears to hear and understand but does not the emphasis shifts to teaching the person to com- verbalize in response municate through other means such as writing or • verbalizes only certain sounds or words pictures. Some people experience spontaneous • makes inconsistent mistakes in speech recovery from acquired verbal apraxia, though neurologists do not know what causes this to hap- These characteristic symptoms distinguish ver- pen or how it happens. bal apraxia from developmental delays in speech, See also AGING, NEUROLOGIC CHANGES THAT OCCUR in which the child’s language skills evolve more WITH; SPEECH DISORDERS; SWALLOWING DISORDERS; slowly than normal but are otherwise typical and VELOPHARYNGEAL INSUFFICIENCY. complete. The diagnostic path includes a compre- hensive speech and language evaluation as well as ataxia The inability to coordinate voluntary an assessment for HEARING LOSS. Early recognition fine-motor movement. Ataxia may be acquired or and diagnosis allow appropriate early intervention, inherited and has varied presentations. Gait and which focuses on training the brain to use different balance disturbances (difficulty with walking) are language pathways. Treatment is more likely to the most common symptoms. Depending on the succeed when the brain is still learning these path- form of ataxia, other symptoms may include dis- ways. Rerouted language pathways appear to turbances of EYE movements, sensory perception, remain as redirected, becoming the “normal” lan- and cognition. The diagnostic path includes diag- guage pathways for the individual, and the person nostic imaging procedures such as MAGNETIC RESO- speaks and otherwise manages language skills in an NANCE IMAGING (MRI) and COMPUTED TOMOGRAPHY age-appropriate manner. However, the ultimate (CT) SCAN to rule out other causes of the symp- success of treatment depends on the nature, loca- toms. Personal health history and family medical tion, and extent of the injury to the brain, factors history are important. the neurologist often does not know. Acquired ataxia most commonly occurs as a result of injury to the cerebellum (the division of Verbal Apraxia in Adults the BRAIN responsible for fine motor movement), Acquired verbal apraxia in adults most commonly SPINAL CORD, or SPINAL NERVES. It may also develop results as a consequence of STROKE or TRAUMATIC as a consequence of long-term ALCOHOLISM and BRAIN INJURY (TBI). The person knows what he or MULTIPLE SCLEROSIS. These forms of ataxia tend to be she wants to say but cannot formulate the words, persistent or slowly progressive, depending on the says the wrong words, or articulates sounds that underlying cause. Acute (sudden onset) acquired are not words (gibberish). The person knows the ataxia may develop following a viral INFECTION right words and is aware his or her words are such as CHICKENPOX and EPSTEIN-BARR VIRUS. No wrong but cannot correct them. Often the mis- treatment is necessary for acute acquired ataxia, as takes in speech are inconsistent; the person may normal movement and coordination generally one time speak flawlessly and the next be unable return within several months. to articulate recognizable words. The person may Hereditary ataxia may occur in various inheri- also speak with incorrect inflection and intona- tance patterns and tends to be slowly progressive. tion, such that the rhythm of speech does not There are several forms of hereditary ataxia, the match the words. Verbal apraxia is extremely frus- most common of which are ataxia telangiectasia trating for the person who has it. and Friedreich ataxia. Hereditary ataxia typically The diagnostic path typically includes imaging begins to show symptoms in early childhood procedures such as COMPUTED TOMOGRAPHY (CT) when the child begins to walk. Most people retain athetosis 227 the ability to walk for 10 to 15 years after symp- procedures such as MAGNETIC RESONANCE IMAGING toms begin and maintain limited independence (MRI) and SINGLE-PHOTON EMISSION COMPUTED TOMOG- with assisted mobility (such as a wheelchair) for RAPHY (SPECT) sometimes show the lesion (dam- another 10 years or longer. aged tissue) within the brain. Treatment for See also AMYOTROPHIC LATERAL SCLEROSIS (ALS); athetosis depends on the underlying cause and CEREBRAL PALSY; COGNITIVE FUNCTION AND DYSFUNC- may include TION; GENETIC COUNSELING; INHERITANCE PATTERN; NYS- • MUSCLE RELAXANT MEDICATIONS such as diazepam TAGMUS; PARKINSON’S DISEASE; VIRUS. (Valium) and clonazepam (Klonopin) athetosis Slow, writhing, involuntary, often con- • OCCUPATIONAL THERAPY to teach adaptive skills tinuous movements of the hands and fingers and and improve MUSCLE control occasionally the upper extremities. Athetosis • DEEP BRAIN STIMULATION, which alters the electri- occurs as a result of damage to the basal ganglia, cal output of the basal ganglia and related NERVE structures deep in the BRAIN that regulate structures voluntary movement. Athetosis occurs in about • RHIZOTOMY, a surgical OPERATION in which the 5 percent of people who have CEREBRAL PALSY neurosurgeon selectively severs root fibers of ENCEPHALOPA and also as a consequence of hepatic - the SPINAL NERVES that serve the affected areas of THY (damage to the structures of the brain result- the body ing from LIVER FAILURE) or encephalopathy due to drug toxicity (including ANTIPSYCHOTIC MEDICA- Outcome also depends on the underlying TIONS and medications to treat PARKINSON’S DIS- cause. Surgery is often effective at eliminating EASE), ENCEPHALITIS (INFLAMMATION of the brain), athetosis when the cause is cerebral palsy. A com- and HUNTINGTON’S DISEASE. Athetosis often occurs bination of methods often achieves relief when in combination with CHOREA (choreoathetosis). other causes are responsible. The diagnostic path relies on physician observa- See also DYSTONIA; TIC; TOURETTE’S SYNDROME; tion in combination with health history. Imaging TREMOR DISORDERS. B

Bell’s palsy Damage to the seventh cranial nerve may involve both sides of the face. Symptoms (facial NERVE) that results in partial to complete include PARALYSIS of the facial structures on the affected • drooping of the eyelid and corner of the MOUTH side. Palsy is an antiquated term for paralysis. The paralysis is usually temporary, though it may take • loss of control of the facial muscles up to six months (and occasionally longer) for • numbness nerve function to return to normal. Bell’s palsy is • excessive tearing of the EYE the most common form of facial paralysis, affect- • drooling (SIALORRHEA) ing more than 40,000 Americans each year. The facial nerve has both motor and sensory • HEARING LOSS or ear PAIN functions. It controls all of the muscles in the face, • disturbances of taste the tiny MUSCLE that moves the stapes BONE in the middle EAR, the muscles that regulate the flow of The PARALYSIS and other symptoms of tears from the tear glands (lacrimal glands), and Bell’s palsy strike suddenly, often mim- the muscles that regulate the flow of saliva from icking those of STROKE. For this reason, the SALIVARY GLANDS. The facial nerve also conveys immediate medical assessment is cru- sensory signals for taste from the tongue to the cial. Stroke is life-threatening and BRAIN. One facial nerve serves each side of the urgent treatment can make the differ- face. The facial nerve runs from the base of the ence for optimal recovery. brain through a channel (the fallopian canal) in the cranial (skull) bones to its emergence at the The diagnostic path includes a NEUROLOGIC base of the earlobe, where it divides into numer- EXAMINATION and assessment of personal health ous branches that extend across the face. history, particularly for any recent viral infections The damage that results in Bell’s palsy typically or circumstances that cause compression or occurs within the fallopian canal. Researchers sus- inflammation of the facial nerve. The doctor may pect viral INFECTION is the primary culprit, as Bell’s conduct imaging procedures such as COMPUTED palsy often follows a viral infection such as TOMOGRAPHY (CT) SCAN, or MAGNETIC RESONANCE INFLUENZA, MENINGITIS, and HERPES SIMPLEX. Trauma IMAGING (MRI) to rule out stroke, tumor, BRAIN HEM- to the head that compresses the facial nerve ORRHAGE, and other possible causes of the symp- within the fallopian canal and extended irritation toms. An electromyogram (EMG) may show the such as may occur with prolonged exposure to extent to which the nerve damage affects the intense wind are also circumstances that can cause facial muscles. The doctor makes the diagnosis of Bell’s palsy. Bell’s palsy after ruling out other possible condi- tions. Symptoms and Diagnostic Path The most prominent feature of Bell’s palsy is facial Treatment Options and Outlook distortion resulting from paralysis of the muscles Treatment for Bell’s palsy targets the cause of the on the affected side of the face. Rarely, symptoms nerve damage when the cause persists, which may 228 blood-brain barrier 229 include anti-inflammatory medications to relieve From these spaces the substances can enter the swelling or ANTIVIRAL MEDICATIONS when a VIRUS cells that need them. appears to be the culprit. It is important to protect In the brain the capillary endothelium is com- the eye when the paralysis affects the muscles pact, its cells forming a tight net to restrict sub- controlling the eyelid, as the eyelid may not blink stances from crossing into the intracellular spaces. or close. The doctor may prescribe topical oph- Glial cells, cells within the brain that support neu- thalmic medications and protection for the eye rons, also participate in the blood–brain barrier, such as an eye shield. Other therapies are prima- although researchers do not fully understand the rily supportive, such as speech and swallowing mechanisms through which they do so. In some therapy. Some people benefit from MASSAGE THER- areas of the brain the blood–brain barrier is looser, APY of the face, PHYSICAL THERAPY, and ACUPUNCTURE allowing substances to more easily cross (though to relieve symptoms and maintain muscle tone not as easily as in the body). Among these areas and health while the damage to the facial nerve are the: heals. About 85 percent of people recover with mini- • area postrema, commonly called the NAUSEA mal or no residual effects. The remainder experi- center, which allows toxins in the bloodstream ence improvement though may have persistent to rapidly trigger the vomiting REFLEX paralysis and loss of function, including hearing • pineal region, the area surrounding the PINEAL impairment. Rarely, Bell’s palsy results in signifi- GLAND cant, permanent loss of function and feeling. In • pituitary region, the area surrounding the PITU- such circumstances doctors may recommend cor- ITARY GLAND rective surgery to restore the protective capability of the eyelid as well as function and appearance The blood–brain barrier permits the brain to of the mouth. The symptoms of Bell’s palsy may maintain balances of neurotransmitters, GLUCOSE, take two weeks to six months or longer to fully electrolytes, fluid, and other substances that differ resolve. from those of the body and are essential for proper brain function. The blood–brain barrier Risk Factors and Preventive Measures also prevents many PATHOGENS (notably BACTERIA People who have DIABETES and women who are in and viruses) from entering the brain, helping the third trimester of PREGNANCY are significantly reduce the likelihood of INFECTION. Many drugs more likely to develop Bell’s palsy. Bell’s palsy is are unable to cross the blood–brain barrier, more common as well in people who have MULTI- though those that can include barbiturates. PLE SCLEROSIS or who are IMMUNOCOMPROMISED. The body must metabolize drugs that cannot Researchers do not know why these circum- cross the blood–brain barrier, such as ANTIBIOTIC stances increase vulnerability to Bell’s palsy. There MEDICATIONS to treat infection and levodopa (a are no known preventive measures for Bell’s palsy. precursor of DOPAMINE taken to treat PARKINSON’S See also CONJUNCTIVITIS; CRANIAL NERVES; LYME DISEASE), into substances small enough to cross the DISEASE; SKELETON; SMELL AND TASTE DISORDERS. capillary endothelium to enter the brain. Thus, though it is primarily protective, the blood–brain blood–brain barrier A protective mechanism barrier sometimes impedes therapeutic efforts. that regulates the size of molecules that may pass Conditions such as HYPERTENSION (high BLOOD PRES- from the bloodstream to the BRAIN. A layer of cells SURE, which can cause microscopic ruptures in the called the endothelium lines the inner channel of capillaries), STROKE, and penetrating trauma to the the body’s tiniest BLOOD vessels, the capillaries. The brain can disrupt the blood–brain barrier by allow- endothelium functions somewhat like a net. In ing blood to come in direct contact with brain parts of the body other than the brain, the cells of tissues. the endothelium are wider apart, forming a looser See also BARBITURATES; CEREBROSPINAL FLUID; net that allows NUTRIENTS, chemicals, and other CREUTZFELDT-JAKOB DISEASE(CJD); NEURON; NEURO- substances to pass into the spaces between cells. TRANSMITTER; PATHOGEN; VIRUS. 230 The Nervous System brain The structural and functional hub of the axons, the pathways by which neurons communi- NERVOUS SYSTEM. The brain regulates the body’s cate, are the white matter. Myelin, which encases functions, voluntary and involuntary. The adult and insulates the axons to contain the electrical brain is a mass of soft, spongy tissue that weighs impulses they transmit, gives the axons their about three pounds. It receives 20 percent of the white appearance. The fully developed adult brain body’s BLOOD flow and consumes 20 percent of the contains about 100 billion neurons and up to 50 body’s oxygen supply. The brain and the SPINAL times as many glial cells. CORD collectively make up the CENTRAL NERVOUS The brain’s three main structural components SYSTEM. are the forebrain (prosencephalon), midbrain The brain resides within the enclosure of the (mesencephalon), and hindbrain (rhomben- cranium (skull). The cranium’s fused bones limit cephalon). Each of these divisions has further the portals of direct access to the brain. The largest structural as well as functional subdivisions, mak- such portal is the foramen magnum, the opening ing the brain the most complex organ of the body. in the occipital bones through which the spinal For the most part the brain is a paired organ, with cord passes. Other smaller passages provide path- its two halves, the right hemisphere and the left ways for the CRANIAL NERVES, which terminate in hemisphere, roughly symmetrical in physical the structures of the brainstem and the underside structure though not in function. A connecting of the brain. Three layers of membranes, the bridge of neuronal tissue, the corpus callosum, MENINGES, wrap around the brain for further physi- allows the hemispheres to communicate with each cal protection. CEREBROSPINAL FLUID circulates other. between the meninges, cushioning the brain as Within the structure of the brain are four con- well as maintaining its biochemical balance. The nected spaces, called ventricles, that produce and BLOOD–BRAIN BARRIER, a specialized layer of cells contain cerebrospinal fluid. The lateral ventricles, lining the blood vessels that serve the brain, also called the first and second ventricles, are the adds a final level of security by limiting the sub- largest and contact the frontal, temporal, and occip- stances that can pass between the blood and the ital lobes. The third ventricle is a small space that brain. joins with the lateral ventricles along the midline of the brain and the fourth ventricle, also small, is at The Brain’s Structure the back of the brainstem and joins with the sub- Neurons (NERVE cells) and glial cells (support cells) arachnoid mater (the middle of the meninges). form the tissue of the brain. Neurons transmit electrical impulses (nerve signals). Glial cells (also The Forebrain called neuroglia) make myelin, a fatty protein The forebrain is the largest of the brain’s structural coating that nourishes and insulates neurons. divisions, making up about 85 percent of the Though the brain contains its full complement of brain’s mass and weight. Its composition is prima- neurons by about age three, glial cells grow and rily gray matter—neuron bodies. The forebrain’s divide throughout life. Though neurons do not subdivisions are the telencephalon and the dien- grow or divide, they do continue to form new cephalon. The first cranial nerve, the olfactory connections (synapses or synaptic circuits) nerve, arises from the telencephalon. The second throughout life by extending and branching their cranial nerve, the OPTIC NERVE, originates in the axons, the fibers that carry nerve impulses from diencephalon. The forebrain also contains the lat- the NEURON to a synapse (a microscopic channel eral ventricles and the third ventricle. that separates one neuron from another). The telencephalon, which makes up the bulk of Areas of the brain that contain high concentra- the forebrain, contains the: tions of neuron bodies, such as the cerebral cortex and the basal ganglia, are the gray matter, so- • cerebral cortex, also called the cerebrum, which named because these areas are dark in color. handles all of the body’s functions related to Areas of the brain such as the inner cerebrum and conscious activity, from thought and behavior the brainstem that are primarily concentrations of to movement and balance brain 231

• basal ganglia, collections of nerve fibers that parietal, temporal, and occipital—that conduct the direct motor functions related to complex brain’s cognitive, emotional, behavioral, analyti- movement, including the coordination of mus- cal, interpretive, sensory, and motor activities. cles and speed with which movements take Though there is some overlap among the lobes in place; among the basal ganglia are the caudate the kinds of information they process and the nucleus, putamen (corpus striatum), globus ways they process it, each lobe has specific func- pallidus, and subthalamic nucleus tions. As well, the corresponding lobes of each • amygdala, a pair of almond-shaped collections hemisphere have complementary functions. The of neurons (nuclei) in the temporal lobes with lobes of the left hemisphere handle more of the functions related to emotion and the storage of tasks and activities of logic, sequence, order, new memories analysis, and verbal communication. The lobes of the right hemisphere handle more of the tasks and • hippocampus, a collection of neurons in each activities of emotion, imagination, intuition, and temporal lobe with functions related to mem- nonverbal communication. ory (especially storage and retrieval of long- The primary structures of the diencephalon are term memories) and learning the: The cerebral cortex features a complex struc- ture of folds (gyri) and fissures (sulci). Each cere- • HYPOTHALAMUS, a mix of endocrine and nerve bral hemisphere contains four lobes—frontal, tissues that integrates many of the neurologic

LOBES OF THE CEREBRAL CORTEX Lobe Location Key Functions frontal forward part of the forebrain, in front of the parietal fine motor movement lobes and above the temporal lobes mood central sulcus separates frontal from parietal lobes personality lateral sulcus separates frontal from temporal lobes planning judgment problem solving verbal expression (Broca’s area) parietal behind the frontal lobes and above the occipital lobes sensory input (taste, touch, PROPRIOCEPTION) central sulcus separates parietal from frontal lobes spatial relationships parieto-occipital sulcus separates parietal and sensory integration occipital lobes reading written expression calculation temporal beneath and behind the frontal lobes sensory input (hearing) lateral sulcus separates temporal from frontal lobes listening (auditory portion of speech) memory processing of complex images such as faces integration with hippocampus language processing (Wernicke’s area) occipital behind the temporal lobes and below the parietal sensory input (vision) lobes visual processing (primary visual cortex) parieto-occipital sulcus separates occipital from parietal lobes 232 The Nervous System

and HORMONE functions of basic survival (such ment of the eighth (vestibulocochlear) cranial as body temperature regulation) nerves originate • thalamus, a small structure that filters and sorts The myelencephalon contains the medulla (modulates) sensory impulses that enter and oblongata, which connects the brainstem and the the motor impulses that leave the brain spinal cord. The ninth (glossopharyngeal), tenth (vagus), eleventh (spinal accessory), and twelfth The diencephalon incorporates the olfactory (hypoglossal) cranial nerves arise from the and optic tracts (origins and pathways of the first medulla oblongata. The fourth ventricle is within and second cranial nerves, respectively). Also the medulla oblongata. The medulla oblongata within the diencephalon are the PITUITARY GLAND regulates BLOOD PRESSURE, HEART RATE, RESPIRATORY and PINEAL GLAND. RATE, digestion, and elimination (URINATION and The Midbrain defecation), as well as reflexive actions such as sneezing and coughing. The midbrain, also called the brainstem, is the point of origin for the third cranial nerve (oculo- Neuron Communication in the Brain motor nerve) and the fourth cranial nerve Brain neurons communicate with one another (trochlear nerve). It is the neuronal bridge that through electrical impulses and biochemical facili- joins the forebrain, hindbrain, and spinal cord. tators called neurotransmitters. Neurotransmitters The midbrain controls primitive survival functions conduct or block the impulse’s travel across a such as BREATHING and heartbeat. It also contains a synapse. Each brain neuron has up to 10,000 cluster of cells called the substantia nigra which synapses, which make up its neuronal pathways; secrete DOPAMINE, a NEUROTRANSMITTER essential for the brain overall has 50 to 200 trillion synapses. movement. The death of cells in the substantia The brain sends and receives nerve impulses con- nigra causes PARKINSON’S DISEASE. tralaterally—that is, the brain’s right hemisphere handles functions dealing with the left side of the The Hindbrain body and its left hemisphere handles functions The hindbrain is beneath and to the back of the dealing with the right side of the body. The brain forebrain. Its two substructures are the meten- receives sensory nerve signals from the body, cephalon and the myelencephalon, which control which its various regions and areas process and numerous bodily functions essential for survival. assimilate. The brain sends motor nerve signals to The fourth ventricles are also located within the the body in response. hindbrain. Recent research suggests the brain appears to The metencephalon is the point of origin for continually adapt and adjust its neuronal, or the fifth (trigeminal), sixth (abducens), seventh synaptic, pathways by extending and branching (facial), and eighth (vestibulocochlear) cranial existing axons and shutting down axon branches nerves. The metencephalon contains the: it no longer uses. This process of continual prun- ing seems aimed at keeping the brain’s neuronal • cerebellum, which directs and coordinated vol- communications streamlined and efficient and untary MUSCLE function; it receives sensory perhaps also at compensating for diminishment input from the vestibular structures of the that may occur through aging. Though the brain is inner EAR (balance) and from peripheral propri- most receptive to learning during the childhood oceptors (specialized sensory nerve endings in years when the establishment of synaptic path- the limbs) that report the body’s spatial orienta- ways is at its peak, the brain remains capable of tion within its environment learning for the duration of the lifespan. • pons, which connects the medulla oblongata and the cerebellum with the cerebrum and Health Conditions and the Brain from which the fifth (trigeminal), sixth The brain is vulnerable to the effects of health (abducens), seventh (facial), and cochlear seg- conditions that affect other body systems as well brain hemorrhage 233 as to disease and injury that affects it directly. CAR- United States apply. However, the criteria vary DIOVASCULAR DISEASE (CVD) is perhaps the most sig- among states in the United States as well as nificant general health risk for the brain. among countries. In general doctors make a decla- Conditions such as ATHEROSCLEROSIS, CORONARY ration of brain death only when there is clear and ARTERY DISEASE (CAD), and HEART FAILURE can dimin- unquestionable cause for and evidence of irre- ish the flow of blood to the brain. HYPERTENSION versible loss of brain function, and a series of pro- (high blood pressure) is the leading cause of cedures consistently support the determination STROKE; stroke, in turn, is the leading cause of irre- that all brain function is absent and has no possi- versible brain injury. Conditions that affect the bility of returning. The concept and establishment body’s metabolic state and balance, such as of brain death has medical, legal, ethical, moral, chronic CIRRHOSIS and DIABETES, may alter the and for many people religious components. brain’s biochemical balance to the extent of dis- The need to establish brain death arises when a rupting brain function (ENCEPHALOPATHY). Direct person has suffered catastrophic injuries, such as injury to the brain may result from INFECTION in a motor vehicle accident, or a catastrophic (ENCEPHALITIS), BRAIN TUMOR (including metastatic health crisis, such as HEART ATTACK or STROKE, that cancer), traumatic injury, and neurodegenerative deprives the brain of oxygen for an extended diseases such as ALZHEIMER’S DISEASE and Parkin- period. Emergency treatment may place the per- son’s disease. son on life support, with MECHANICAL VENTILATION to maintain BREATHING. Removing life support gener- HEALTH CONDITIONS THAT AFFECT THE BRAIN ally requires medical consensus that brain death ALZHEIMER’S DISEASE BRAIN HEMORRHAGE has occurred. The declaration of brain death is also BRAIN TUMOR CEREBRAL PALSY necessary to harvest organs such as the HEART for COMA CONCUSSION ORGAN TRANSPLANTATION. In most circumstances a CREUTZFELDT-JAKOB DISEASE (CJD) DEMENTIA person’s next of kin, family members, or person DOWN SYNDROME EDWARDS SYNDROME designated with medical power of attorney must ENCEPHALITIS ENCEPHALOPATHY authorize cessation of life support even with a HUNTINGTON’S DISEASE MENINGITIS declaration of brain death. MULTIPLE SCLEROSIS NEURAL TUBE DEFECTS ORGANIC BRAIN SYNDROME PARKINSON’S DISEASE CARDINAL EVIDENCE OF BRAIN DEATH PATAU SYNDROME PERSISTENT VEGETATIVE STATE clear cause for irreversible BRAIN death SEIZURE DISORDERS TOURETTE’S SYNDROME no evidence of drugs or conditions that could suppress brain TRAUMATIC BRAIN INJURY (TBI) TREMOR DISORDERS function COMA For further discussion of the brain within the no REFLEX response to PAIN context of the structures and functions of the no brainstem reflexes nervous system, please see the overview section no electrical activity on ELECTROENCEPHALOGRAM (EEG) “The Nervous System.” See also ARTERIOVENOUS MALFORMATION (AVM); See also END OF LIFE CONCERNS; QUALITY OF LIFE. BRAIN DEATH; CIRCLE OF WILLIS; COUGH; SCOTOMA; SNEEZE. brain hemorrhage Significant loss of BLOOD within the cranium or the tissues of the BRAIN. brain cancer See BRAIN TUMOR. Most brain hemorrhages occur suddenly and unexpectedly. Occasionally brain hemorrhage may brain death The permanent cessation of BRAIN be chronic, such as when slow bleeding takes function commonly accepted as the indication that place through a small rupture in an ANEURYSM. life has ended. The American Academy of Neurol- Brain hemorrhage has two major conse- ogy has established guidelines for determining quences, each of which can be life-threatening: It whether brain death has occurred that form the deprives the brain of vital oxygen and it causes basis for the criteria health-care providers in the increased pressure within the skull. Brain hemor- 234 The Nervous System rhage may result from trauma to the brain or from • irritability the rupturing of a blood vessel (hemorrhagic • seizures STROKE), and may occur within the tissues of the brain, between the inside of the cranium (skull) • fluctuations in consciousness and cognitive and the MENINGES (membranes that enclose and function protect the brain), or between the layers of the meninges. Doctors designate the kind of bleeding The diagnostic path typically begins with a NEU- by its location, which also provides clues as to the ROLOGIC EXAMINATION and COMPUTED TOMOGRAPHY cause of the bleeding. A brain hematoma is a col- (CT) SCAN or MAGNETIC RESONANCE IMAGING (MRI)of lection of blood, though many people use the the head. These procedures can nearly always terms hemorrhage and hematoma interchangeably confirm the diagnosis of brain hemorrhage as well in referring to bleeding in the brain. as pinpoint its location and provide information for the neurologist to assess the severity of the Suspected brain hemorrhage is a poten- bleeding and potential extent of damage. Because tially life-threatening emergency that the standard of treatment for stroke that results requires immediate medical evaluation from a blood clot in a blood vessel is thrombolytic and treatment. medications to dissolve the clot, doctors conduct these procedures with urgency so they can initiate Symptoms and Diagnostic Path the appropriate treatment. Symptoms of brain hemorrhage are very much the same regardless of the location of the bleeding. Treatment Options and Outlook They include Rapid treatment is essential to stop the bleeding and relieve pressure within the brain. In many sit- • severe HEADACHE that may come on suddenly or uations such treatment is emergency surgery to come and go repair the bleeding blood vessels and drain the • weakness or numbness (especially if only on collected blood. The risk of dying from intracere- one side of the body) bral hemorrhage (hemorrhagic stroke) is particu- larly high because the bleeding is often extensive • difficulty forming words, using the right words, and directly damages vital areas of the brain. The or understanding what others are saying extent of residual damage after successful treat- • NAUSEA and VOMITING ment depends on many factors and may not be

KINDS OF BRAIN HEMORRHAGE Brain Hemorrhage Location Likely Causes or Contributing Factors epidural between the cranium and the dura mater (above the blunt trauma to the head MENINGES) bleeding disorders subdural between the dura mater and the arachnoid mater blunt trauma to the head (the outermost and middle meninges) subarachnoid between the arachnoid mater and the pia mater ruptured ANEURYSM (the middle and innermost meninges) blunt trauma to the head intracerebral within the tissues of the BRAIN HYPERTENSION ATHEROSCLEROSIS ruptured aneurysm ruptured vascular malformation brain tumor 235 apparent for weeks to months after the bleeding. However, the tumor’s size and location are Some people have significant permanent conse- often the more relevant factors in determining quences such as PARALYSIS, SEIZURE DISORDERS, and treatment options and prognosis (prospects for cognitive dysfunction. Many people who recover recovery). Because the cranium, which houses the have minimal permanent consequences, particu- brain, is a closed space, any extra mass within it larly when diagnosis and treatment are immedi- puts pressure on the tissues of the brain that can ate. PHYSICAL THERAPY, OCCUPATIONAL THERAPY, and cause serious damage or death. Though all of the speech therapy help restore maximum function. brain is important, some areas are vital to sustain the functions of life. A tumor growing in such an Risk Factors and Preventive Measures area, such as the brainstem, may become life- Trauma to the head, such as may occur in MOTOR threatening more quickly than a tumor growing VEHICLE ACCIDENTS or falls, is the most common elsewhere in the brain. As well, some areas of the cause of brain hemorrhage. Proper restraints (seat brain, again such as the brainstem, are inopera- belts and car seats) and helmets worn during ble—that is, a neurosurgeon cannot get to the activities such as bicycle riding and downhill ski- tumor to remove it. Neurologists grade (classify) ing, help reduce the risk for head injury. Young brain tumors according to their cells of origin, size, children and elderly adults are at highest risk for likelihood to grow in size, and likelihood to infil- head injury due to falls. HYPERTENSION (high BLOOD trate (spread into) the tissues and supportive PRESSURE) is the most significant preventable risk structures of the brain. Many brain tumors con- factor for intracerebral hemorrhage (bleeding tain a combination of cell types. within the tissues of the brain). Lifestyle factors such as cigarette smoking, which causes changes TYPES OF BRAIN TUMORS in the structure of the walls of the arteries, and astrocytoma chordoma lack of regular physical activity can exacerbate the craniopharyngioma dermoid cyst effects of hypertension. People who take anticoag- ependymoma epidermoid cyst ulant medications (“blood thinners”) or who con- ganglioglioma ganglioneuroma sume excessive amounts of ALCOHOL have glioblastoma glioblastoma multiforme (GBM) increased risk for brain hemorrhage because these glioma hemangioblastoma substances slow the blood’s ability to clot. People medulloblastoma (MDL) meningioma who have MARFAN SYNDROME also have increased neuroglioma oligodendroglioma risk for brain hemorrhage as this congenital disor- pineal germinoma pituitary ADENOMA der causes abnormalities in the blood vessel struc- primary malignant primitive neuroectodermal tumor tures. lymphoma (PNET) See also COGNITIVE FUNCTION AND DYSFUNCTION; CONCUSSION; TRAUMATIC BRAIN INJURY (TBI). Symptoms and Diagnostic Path The symptoms of a brain tumor depend on the brain tumor An abnormal growth that arises tumor’s location and the parts of the brain the within the tissues of the BRAIN. Brain tumors may tumor’s presence affects. Though HEADACHE can be be noncancerous or cancerous, and cancerous among the symptoms of brain tumor, most brain tumors may be primary (originate in the headaches, even those that are severe, do not indi- brain) or metastatic (spread to the brain from can- cate a brain tumor. Disturbances of balance, motor cer that originates elsewhere in the body). About control (movement and coordination), special 75 percent of cancerous brain tumors are metasta- senses (sight, smell, taste, and hearing), cognitive tic. Primary brain cancer very seldom spreads function, memory, and emotions are common beyond the CENTRAL NERVOUS SYSTEM (brain and general symptoms of brain tumors. Brain tumors SPINAL CORD). In general noncancerous brain may also cause seizures, NAUSEA and VOMITING, and tumors are easier to treat than primary cancerous weakness or PARALYSIS on one side of the body. brain tumors because they tend to remain con- The diagnostic path begins with a PERSONAL tained. HEALTH HISTORY and NEUROLOGIC EXAMINATION, with 236 The Nervous System

BRAIN TUMOR SYMPTOMS AND SIGNS Tumor Location Common Symptoms and Signs cerebrum—frontal lobe erratic behavior emotional outbursts cognitive dysfunction memory dysfunction altered sense of smell vision impairment hemiplegia or hemiparesis (PARALYSIS or weakness on one side of the body) awkward, uncoordinated movement seizures cerebrum—occipital lobe loss of vision in the upper half or the lower half of the field of vision seizures cerebrum—parietal lobe difficulty with language and speech loss of the ability to write seizures loss of PROPRIOCEPTION (spatial orientation) cerebrum—temporal lobe seizures disturbances of language processing and articulation eighth cranial NERVE (vestibulocochlear nerve) tinnitus (ringing in the ears) HEARING LOSS midline (center of the ventral surface of the BRAIN) persistent HEADACHE NAUSEA NYSTAGMUS vision disturbances erratic behavior or personality changes cerebellum awkward, staggering gait swaying when standing lack of coordination brainstem irritability inability to concentrate headache that is especially severe upon waking disturbances of vision and EYE function nausea and vomiting MUSCLE weakness

imaging procedures such as MAGNETIC RESONANCE cells (biopsy) to determine the type of tumor and IMAGING (MRI) and COMPUTED TOMOGRAPHY (CT) SCAN whether it is cancerous or noncancerous. When to examine the brain’s structure. Most tumors are the tumor is near the surface of the brain, the detectable with these procedures. However, the neurosurgeon can usually reach it via craniotomy neurosurgeon must take a sample of the tumor’s (drilling or cutting a small hole through the cra- brain tumor 237 nium). Deeper tumors may require guided stereo- ing to participate in a clinical trial. Among the tactic techniques in which the neurosurgeon uses most promising investigational treatments are an imaging procedure such as MRI to guide the medications that specifically target certain kinds of insertion of a biopsy instrument to the tumor with cells such as cancer cells. minimal disturbance of other brain tissue. Labora- Metastatic brain cancer is very difficult to treat tory examination of the tumor’s cells combined because the cancer is generally widespread with the visual images of the CT scan or MRI help throughout the body by the time it appears in the the neurosurgeon identify and grade the tumor. brain. Treatment must target the original cancer as well as the metastatic brain tumor. Chemotherapy Treatment Options and Outlook and radiation therapy are sometimes effective in The tumor’s type, grade, and location determine achieving REMISSION of cancers that have metasta- the appropriate treatment options. Whenever pos- sized to the brain, though in general the outlook is sible, surgery to remove a primary tumor (or as not favorable for metastatic brain cancer. much of it as possible) is the preferred treatment. However, tumors that deeply infiltrate brain tis- Risk Factors and Preventive Measures sue, are very large, intertwine with BLOOD vessels, Neurologists do not know what causes primary or are located in vital areas may be inoperable. As brain tumors to develop. There is evidence that well, surgery is generally not a viable option for exposure to certain toxic chemicals, notably vinyl metastatic brain tumors. RADIATION THERAPY can kill chloride, increases the risk for primary brain can- tumor cells to shrink or eradicate the tumor. Most cer. However, the correlations are not as yet con- often, treatment combines surgery and radiation clusive. Primary brain tumors, cancerous and therapy. Outcomes are most promising when noncancerous, occur in people of all ages and treatment can remove 90 percent or more of the about equally in men and women. Early diagnosis tumor. allows the widest range of treatment options, and CHEMOTHERAPY is not generally an effective early treatment offers the best opportunity for a treatment for primary brain tumors because it has positive outcome. There are no known measures no effect on noncancerous tumors and because to prevent brain tumors. However, lifestyle meas- primary brain cancer typically remains contained ures such as nutritious EATING HABITS, daily physical within the brain, making it unnecessary to expose exercise, maintaining healthy weight, and not the entire body to the effects of chemotherapy. smoking all help support the body’s natural Chemotherapy may be the treatment of choice for IMMUNE SYSTEM efforts to resist disease and main- metastatic brain cancer, however, and for certain tain the body in optimal health. brain cancers in very young children. For people See also ACOUSTIC NEUROMA; BRAIN HEMORRHAGE; who have brain tumors beyond the reach of cur- CANCER TREATMENT OPTIONS AND DECISIONS; COGNITIVE rent treatment options, neurologists and oncolo- FUNCTION AND DYSFUNCTION; CONCUSSION; END OF LIFE gists may recommend clinical trials that are CONCERNS; MEMORY AND MEMORY IMPAIRMENT; METAS- investigating new treatments. It is important to TASIS; MULTIPLE ENDOCRINE NEOPLASIA (MEN); NEUROFI- fully understand both the risks and the potential BROMATOSIS; RETINOBLASTOMA; SURGERY BENEFIT AND benefits of investigational treatments before agree- RISK ASSESSMENT; TRAUMATIC BRAIN INJURY (TBI). C central nervous system The collective structures weeks, 26 to 34 gestational weeks, and 36 to 40 of the BRAIN and SPINAL CORD, exclusive of the CRA- gestational weeks. NIAL NERVES and SPINAL NERVES (the cranial nerves About 10 percent of cerebral palsy occurs as a and the spinal nerves, along with their branches, result of injuries that occur during or after birth make up the PERIPHERAL NERVOUS SYSTEM). The cen- that deprive the brain of oxygen (HYPOXIA). Other tral nervous system functions as the master con- known causes of cerebral palsy acquired in the trol center for the body, maintaining processes to early postnatal period include untreated NEONATAL support basic survival as well as conducting com- JAUNDICE (JAUNDICE of the newborn), Rh factor plex voluntary and conscious activities. The cra- BLOOD TYPE incompatibility, and head injury such nium (skull) and spinal column (vertebrae) as may occur in MOTOR VEHICLE ACCIDENTS or falls. enclose and protect the central nervous system. Most often the causes of cerebral palsy in an indi- For further discussion of the central nervous vidual remain uncertain and likely represent a system within the context of the structures and combination of circumstances (multiple factors). functions of the nervous system, please see the Cerebral palsy has widely variable presenta- overview section “The Nervous System.” tions. These presentations help determine the See also COMA; CONSCIOUSNESS; SKELETON; UNCON- stage of development—prenatal, perinatal, or SCIOUSNESS. postnatal—in which the damage to the brain occurs. Other conditions that often accompany cerebral palsy Disturbances of motor movement cerebral palsy include HEARING LOSS, VISION IMPAIR- resulting from damage to the structures of the MENT, developmental disorders, LEARNING BRAIN responsible for movement, notably the basal DISORDERS, intellectual impairment, and SEIZURE ganglia. About 500,000 Americans, children and DISORDERS. These conditions reflect damage to adults, have cerebral palsy. Cerebral palsy is per- other structures of the brain that may have manent though nonprogressive (does not worsen occurred as a result of exposure to the same event over time). Though cerebral palsy often is congen- or circumstance responsible for the cerebral palsy ital (present at birth) and may result from GENE (especially hypoxia). Doctors classify the forms of MUTATION, it is not hereditary (passed from parents cerebral palsy according to the pattern of symp- to child). toms present. The four general classifications cur- Neurologists believe about 90 percent of the rently in use are spastic, athetoid (dyskinetic), damage that results in cerebral palsy occurs in ataxic, and mixed. PREGNANCY during the development of the NERVOUS Spastic cerebral palsy Spastic cerebral palsy SYSTEM, sometimes long before birth. Known affects about 70 percent of those who have cere- causes of such damage include INFECTION, such as bral palsy and is the “classic” form first docu- RUBELLA (German MEASLES) and TOXOPLASMOSIS,in mented by English physician William Little in the the mother during pregnancy and interruptions of mid-1800s. In spastic cerebral palsy the affected BLOOD flow to the developing fetus. These events muscles are in a state of continuous contraction, may disrupt critical stages of brain development. causing them to feel and appear stiff. Spasticity The most vulnerable times are 3 to 20 gestational affects motor movement and balance. Over time 238 cerebral palsy 239 the spastic muscles tend to remain fixed in their palsy have this form, which most commonly positions (contractures) as the contracted MUSCLE affects the arms and legs though also can involve fibers eventually shorten. There are four forms of the face. Facial involvement typically results in spastic cerebral palsy that affect the body in differ- speech, eating, and swallowing difficulties. The ent ways: movements generally subside during sleep and often intensify during emotional experiences. • Spastic diplegia affects both arms and both legs, Ataxic cerebral palsy Ataxic cerebral palsy is though it affects the legs more severely. The the least common form of cerebral palsy, affecting legs of people who have spastic diplegic cere- only about 5 percent of people who have cerebral bral palsy often turn in at the knees and cross palsy. Ataxic cerebral palsy affects a person’s bal- with walking, causing a characteristic, awkward ance and coordination, causing the person to “scissors gait.” Balance and sustained move- adopt a wide stance and gait. In this form of cere- ment may be difficult. Severe leg involvement bral palsy muscle tone may be normal, increased, may result in the inability to walk. When arm or decreased. Tasks that require rapid or prolonged involvement is moderate to severe, the person movements are often the most difficult. People may need assistance to eat, bathe, dress, and who have ataxic cerebral palsy may also have carry out many of the functions of daily living. intention tremors, in which their arms or legs • Spastic hemiplegia (also called spastic hemi- shake uncontrollably with purposeful movement paresis) affects the arm, trunk, and leg on one such as taking a step or reaching for an object. side of the body. Balance is generally better Mixed cerebral palsy About 10 percent of peo- than with spastic diplegia because one side of ple who have cerebral palsy have a mix of the the body functions normally, though gait is standard forms. The most common mixed form is awkward. Spastic hemiplegia may also affect spastic and athetoid, in which the person has both one side of the face, sometimes resulting in stiff, contracted muscles and involuntary, writhing speech, eating, and swallowing difficulties. movement. Mixed forms of cerebral palsy also Some people who have spastic hemiplegic cere- range from mild to severe, though are more likely bral palsy experience tremors (uncontrollable to interfere with mobility and independence at shaking) on the affected side of the body. less severe levels because of the multiple effects. • Spastic paraplegia (also called spastic parapare- Symptoms and Diagnostic Path sis) affects only the legs. As with spastic diple- The symptoms of cerebral palsy generally do not gia, movement when walking may be become apparent until an infant is 2 months to 2 awkward. Balance is generally better, though, years old. Neurologists have identified hand pref- because the arms and upper body function nor- erence before age 12 months as one of the first mally and can to some extend offset the dys- indications of spastic hemiplegic cerebral palsy; in functions of the lower body. the course of normal development a child does • Spastic quadriplegia (also called spastic quadri- not acquire hand preference until older than 12 paresis) affects the entire body—face, arms, months. Infants who have cerebral palsy may trunk, legs—with equal severity. People who reach developmental markers, such as sitting have mild spastic quadriplegic cerebral palsy unassisted or rolling over, more slowly than nor- may function relatively normally, though peo- mal. Some have obvious hypertonicity (tense ple who have moderate to severe damage may muscles) or hypotonicity (flaccid muscles). be relatively immobilized and dependent on The pediatrician closely monitors a child at risk others for care. for cerebral palsy, regularly assessing motor skills, reflexes, and other dimensions of growth and Athetoid cerebral palsy Athetoid, or dyskinetic, development. Common at-risk factors include low cerebral palsy causes persistent, involuntary birth weight, preterm (premature) delivery, movements that are slow, rhythmic, and writhing. seizure disorders, severe neonatal jaundice, Rh About 15 percent of people who have cerebral incompatibility, and a history of difficulties during 240 The Nervous System pregnancy. The doctor may conduct diagnostic some forms of cerebral palsy, notably spastic imaging procedures such as COMPUTED TOMOGRAPHY hemiplegic, symptoms may change from day to (CT) SCAN and MAGNETIC RESONANCE IMAGING (MRI) to day. Spasticity may develop into contractures. visualize the structures of the brain. An ELECTROEN- However, the person’s overall neuromuscular sta- CEPHALOGRAM (EEG) helps identify electrical irregu- tus remains unchanged. The doctor may conduct larities in the brain that may identify structural repeated NEUROLOGIC EXAMINATION and diagnostic abnormalities. Though none of these tests conclu- procedures to monitor any changes in symptoms, sively diagnoses cerebral palsy, the tests help rule though generally can make a firm diagnosis when out other possible causes of symptoms. the child is age three to five years. As the child grows older the symptoms of cere- bral palsy often become unmistakable. Among Treatment Options and Outlook them are Cerebral palsy is irreversible. Treatment targets relieving symptoms and may include medications • spasticity and contractures of the limbs to relieve spasticity (such as baclofen), tremors, • inability to crawl or walk sialorrhea, and muscle tenseness. Many people • vision impairment take combinations of medications tailored to their specific needs and symptoms. People who have • hearing loss severe spastic cerebral palsy may benefit from • swallowing and speech difficulties injections of medication into the fluid around the • SIALORRHEA (drooling) SPINAL CORD, which allows higher concentrations of • URINARY INCONTINENCE the medication to reach the NERVE cells than the person could otherwise tolerate. The severity of symptoms does not worsen, PHYSICAL THERAPY can specifically target particu- though symptoms may change over time. With lar muscle groups and developmental delays, and

KNOWN RISK FACTORS FOR CEREBRAL PALSY Risk Factor Preventive Measures maternal RUBELLA (viral INFECTION) rubella VACCINE before PREGNANCY maternal TOXOPLASMOSIS (protozoan infection) avoid contact with cat feces (such as when cleaning a litter box or working in an outdoor garden) thoroughly cook pork and lamb preterm delivery appropriate and consistent PRENATAL CARE low birth weight appropriate nutrition diligent management of DIABETES avoid smoking avoid drinking ALCOHOL

Rh incompatibility Rh screening before pregnancy Rh serum to mother after birth of Rh-incompatible child to protect future children

NEONATAL JAUNDICE PHOTOTHERAPY head injury methods to reduce risks for falling appropriate infant restraints in motor vehicles chorea 241 is especially effective when children who have the amount of cerebrospinal fluid in circulation is cerebral palsy are young. Parents and physical only 150 mL. The vascular arachnoid mater therapists work together with stretching exercises absorbs cerebrospinal fluid into the BLOOD circula- to keep muscles from contracting and activities tion. Cerebrospinal fluid is 99 percent water that that improve coordination and balance. Speech contains electrolytes, GLUCOSE (sugar), and pro- and swallowing therapy teaches methods for gain- teins. The composition, color, and pressure of ing optimal muscle control. Physical therapy is cerebrospinal fluid are important diagnostic char- often a long-term, even lifelong, process with spe- acteristics, which a neurologist may assess using cific methods for the stages of development a child LUMBAR PUNCTURE. In health cerebrospinal fluid is goes through during the process of growing up. sterile so the presence of BACTERIA or another Continued physical therapy often is helpful for PATHOGEN is diagnostic of INFECTION. adults who have cerebral palsy, helping to keep them as independent as possible. CEREBROSPINAL FLUID Surgical approaches include THALAMOTOMY (tar- color clear geted ablation, or destruction) of cells in the thala- volume 150 milliliters mus, a brainstem structure that helps regulate pressure 100 to 200 millimeters of water voluntary movement, operations to lengthen con- white blood cells > 5 per cubic millimeter tracted muscles, and RHIZOTOMY (selectively cutting red blood cells none segments of spinal nerve roots to block nerve sig- GLUCOSE 60 to 80 milligrams per deciliter (mg/dL) nals to reduce spasticity). Many people who have protein 20 to 45 mg/dL cerebral palsy are able to live fairly independently sodium 138 milliequivalents per liter (mEq/L) with assistive devices and mobility aids. Comput- chloride 119 mEq/L ers are especially valuable tools, with adaptive potassium 2.8 mEq/L technology to allow a person who has extreme mobility limitations to communicate. For further discussion of cerebrospinal fluid within the context of the structures and functions Risk Factors and Preventive Measures of the NERVOUS SYSTEM, please see the overview sec- Most often doctors do not know the exact causes tion “The Nervous System.” of cerebral palsy, even when they can correlate See also BRAIN HEMORRHAGE; BRAIN TUMOR; the presentation to specific windows of prenatal ENCEPHALITIS; MENINGITIS; MULTIPLE SCLEROSIS; NEURO- development or to perinatal or postnatal events. LOGIC EXAMINATION. Appropriate and consistent PRENATAL CARE helps a woman maintain a pregnancy that is as healthy as chorea Rapid, irregular, and involuntary move- possible, reducing the risk not only for cerebral ments that occur as a result of damage to struc- palsy but also for other complications and condi- tures of the BRAIN, notably the basal ganglia and tions that could harm the unborn child. Among subthalamic nucleus, that regulate voluntary MUS- the known causes of cerebral palsy, some are pre- CLE function. The word chorea is from the Greek ventable and others are not. word for “dance.” Researchers believe chorea rep- See also ATAXIA; ATHETOSIS; CONTRACTURE; QUALITY resents damage to the mechanisms within these OF LIFE; REFLEX; SPASM. structures that ordinarily suppress extraneous NERVE signals to the muscles. Such damage allows cerebrospinal fluid The liquid that circulates the signals through, creating confused and exces- between the arachnoid mater and pia mater, the sive motor response. Chorea often occurs in com- middle and inner MENINGES surrounding the BRAIN bination with ATHETOSIS (called choreoathetosis) and SPINAL CORD. Its purpose is to cushion and pro- and is a symptom rather than a condition. tect these structures. Specialized cells that line the Chorea usually involves the arms and legs choroid plexuses (ventricular structures within the though may also involve the face and trunk. The brain) produce cerebrospinal fluid at a rate of movements of chorea appear randomly and seem about 500 milliliters (mL) every 24 hours, though to flow from one part of the body to the other, 242 The Nervous System though often are abrupt and exaggerated. In its and remember are key functions of the BRAIN. mildest form chorea appears as restless fidgeting; Numerous metabolic and neurologic conditions in its most severe form (called ballism) chorea pre- affect these functions, some transiently and others vents mobility and actions such as holding objects. permanently. Medications may also alter cognitive Chorea occurs in numerous neurologic conditions, function, either intentionally (as with the acetyl- including HUNTINGTON’S DISEASE (formerly called cholinesterase inhibitors to treat ALZHEIMER’S DIS- Huntington’s chorea), PARKINSON’S DISEASE, SYS- EASE) or as undesired side effects. Adequate TEMIC LUPUS ERYTHEMATOSUS (SLE), untreated NEONA- cognitive function is essential for learning as well TAL JAUNDICE (kernicterus), RETINITIS PIGMENTOSA, as for independent living. and CEREBRAL PALSY. Some research suggests The two frontal lobes of the cerebrum conduct autoimmune processes contribute to some forms most of the functions of cognition, with the other of chorea. One form of chorea, Sydenham’s cerebral lobes contributing processes such as sen- chorea, results from streptococcal INFECTION that sory input and behavioral cues. The prefrontal migrates to the brain after untreated or under- areas of the frontal lobes are the most active in treated STREP THROAT. regard to cognitive functions, performing func- The diagnostic path depends on whether there tions related to analytic thought, judgment, and are known neurologic conditions or the chorea is concentration. Other areas of the frontal lobes a new symptom occurring without a known regulate motor movement necessary for language underlying neurologic cause. In the latter situa- expression and speech. The temporal lobes, tion the doctor conducts generalized BLOOD tests to located beneath and somewhat behind the frontal measure thyroid HORMONE levels, electrolyte levels, lobes, interpret language input and recall memo- cell composition of the blood, and antibodies for ries. One temporal lobe also contains the speech streptococcus. The clinician may also conduct center. The structures of the limbic system, diagnostic imaging procedures such as MAGNETIC notably the amygdala and the hippocampus, con- RESONANCE IMAGING (MRI) and COMPUTED TOMOGRA- trol the storage of recent memories. PHY (CT) SCAN to assess the brain’s structure. Such procedures will show tumors, STROKE, and Symptoms and Diagnostic Path anatomic abnormalities that could be responsible The symptoms of cognitive dysfunction vary for the chorea. according to the damaged area of the brain. Symp- Treatment may include ANTIBIOTIC MEDICATIONS toms tend to appear gradually when the cause of when blood tests identify, or the doctor suspects, the damage is a progressive neurologic disorder. A strep infection. Antiseizure medications, MUSCLE person in the early stages of cognitive loss may: RELAXANT MEDICATIONS, and some of the ANTIPSY- CHOTIC MEDICATIONS (notably haloperidol) often • become easily confused relieve the chorea. Forms of chorea that result • get lost on familiar routes from transient conditions typically improve or go • be unable to perform tasks such as using a away within weeks to months. Forms of chorea checkbook or reading a book that result from permanent damage, such as TRAU- MATIC BRAIN INJURY (TBI) or HYPOXIA (extended oxy- • say the wrong words gen deprivation), or from degenerative conditions, • fail to remember recent events such as Huntington’s disease, do not improve and may worsen as the underlying neurologic condi- When the cause of cognitive dysfunction is tion progresses. damage to the brain that occurs as a result of See also ANTIBODY; AUTOIMMUNE DISORDERS; DYSTO- TRAUMATIC BRAIN INJURY (TBI) or STROKE, the cogni- NIA; RHEUMATIC HEART DISEASE; SPINAL CORD INJURY; tive loss is generally obvious though may improve THYROID GLAND; TIC. over time and with treatment. The diagnostic path begins with a comprehensive medical examina- cognitive function and dysfunction The abilities tion, including assessment of PERSONAL HEALTH HIS- to think, reason, concentrate, process language, TORY, and a general NEUROLOGIC EXAMINATION. The cognitive function and dysfunction 243

COGNITIVE FUNCTIONS OF KEY BRAIN AREAS Brain Area Key Cognitive Functions Indications of Damage cerebrum—frontal lobes logic inability to conduct tasks such as simple math or preparing meals analytic thought cannot get from one place to another, such as home to the store judgment cannot follow directions or instructions concentration difficulty finding the right words to speak or write language formation short, fragmented attention span and expression inability to assess right and wrong planning organization cerebrum—temporal lobes language interpretation inability to understand what others say memory recall cannot remember previously learned information cerebrum—parietal lobes PROPRIOCEPTION (awareness inability to write of body’s location in its physical environment) cerebrum—occipital lobes visual interpretation inability to read amygdala/hippocampus memory storage cannot remember recent events cannot learn new information

findings determine subsequent diagnostic proce- around of symptoms arising from these causes. dures, which often include COMPUTED TOMOGRAPHY Because many of the areas of the brain involved (CT) SCAN or MAGNETIC RESONANCE IMAGING (MRI) to in cognition are functional rather than anatomic visualize brain structure and ELECTROENCEPHALO- divisions, their locations vary somewhat among GRAM (EEG) to evaluate the brain’s electrical activ- individuals. This is one of the factors that creates ity. Cognitive assessment testing measures the challenge for neurologists when assessing the ability to perform analytic and computational extent of damage and the potential for recovery of tasks; recall information; and orient to time, place, functions when the cause of the damage is injury and current events. to the brain. In most people, recovery reaches its maximum level in about two years from the time CONDITIONS THAT MAY AFFECT COGNITIVE FUNCTION of injury. Targeted, persistent PHYSICAL THERAPY and ALZHEIMER’S DISEASE BRAIN HEMORRHAGE OCCUPATIONAL THERAPY can help the brain “repro- BRAIN TUMOR CREUTZFELDT-JAKOB DISEASE (CJD) gram” to use other areas for some cognitive func- DEMENTIA HUNTINGTON’S DISEASE tions. HYPOGLYCEMIA medication side effects When the cause of cognitive loss is a progres- MULTIPLE SCLEROSIS ORGANIC BRAIN SYNDROME sive neurologic disorder, treatment efforts are pri- PARKINSON’S DISEASE sleep deprivation marily supportive and aim to maintain STROKE TRAUMATIC BRAIN INJURY (TBI) independent functioning for as long as possible. Medications such as acetylcholinesterase inhibitors Treatment Options and Outlook sometimes improve symptoms in people who Treatment approaches target the underlying have Alzheimer’s disease though are less pre- causes of cognitive dysfunction. Stopping med- dictably effective in other degenerative disorders ications and correcting metabolic disorders that that affect cognitive function. Other medications disrupt thinking or memory result in rapid turn- may improve psychiatric stability, motor function, 244 The Nervous System and related symptoms that contribute to cogni- Neurologists may use various assessment tion, improving the person’s overall ability to approaches, such as the Glasgow Coma Scale or engage in cognitive activities. the Rancho Los Amigos Scale (RLAS), to evaluate the depth of a coma and the extent of damage to Risk Factors and Preventive Measures the BRAIN that the coma represents. Brain damage resulting from stroke or TBI is the See also ANESTHESIA; DELIRIUM; UNCONSCIOUSNESS. leading cause of cognitive dysfunction among adults in the United States. Preventive measures concussion An injury to the BRAIN resulting that target these events correspondingly lower the from a blow to the head. The blow causes the likelihood of cognitive dysfunction. For stroke brain to jolt against the inside of the cranium such measures include appropriate treatment for (skull), causing BLOOD vessels within the brain tis- HYPERTENSION (high BLOOD PRESSURE) and DIABETES, sue to rupture. Often these are small blood vessels the leading causes of stroke. For TBI such meas- and the bleeding is comparable to that of minor ures include appropriate protective devices such as bruising, though any damage within the brain seat belts in vehicles and helmets for activities that may have potentially serious consequences, entail risk for contact injuries to the head. depending on its location. Brain tissue may also There is some evidence that the herbal supple- swell as a protective response to traumatic injury. ment GINKGO BILOBA helps maintain alertness and Concussion is the most common head injury. cognitive function in people who are healthy and Symptoms and Diagnostic Path may improve concentration and cognition in peo- The symptoms of concussion vary with the sever- ple who have mild forms of cognitive dysfunction ity of the blow. The symptoms of mild to moderate or memory impairment. However, neither pre- concussion typically include scription medications nor herbal products have the ability to fully restore cognitive functions lost • HEADACHE to permanent brain damage such as occurs with • dizziness Alzheimer’s disease or TBI. • confusion or disorientation See also ENCEPHALOPATHY; MEMORY AND MEMORY IMPAIRMENT. • vision changes or disturbances such as “seeing stars” or seeing double (DIPLOPIA) coma A sustained state of loss of CONSCIOUSNESS • ringing in the ears (TINNITUS) from which a person cannot be aroused. When in • brief loss of memory, especially of the incident a coma a person does not respond to any external causing the concussion stimuli, including PAIN. REFLEX responses may or may not be present, depending on the depth of The symptoms of mild to moderate concussion the loss of consciousness. Some comas are typically go away in 15 minutes to several hours. reversible with immediate and appropriate med- Symptoms that are more extensive suggest severe ical intervention. However, irreversible coma typi- concussion and typically include cally leads to PERSISTENT VEGETATIVE STATE or BRAIN DEATH. • severe headache • one pupil larger than the other

COMMON CAUSES OF COMA • NAUSEA and VOMITING BRAIN HEMORRHAGE CARDIAC ARREST • drowsiness or inability to stay awake DRUG OVERDOSE ENCEPHALITIS • persistent confusion excessive ALCOHOL consumption hepatic ENCEPHALOPATHY • irritability, agitation, or emotional instability HYPERGLYCEMIA hypoglycemia • weakness on one side of the body STROKE toxic exposure TRAUMATIC BRAIN INJURY (TBI) untreated HYPOTHYROIDISM A person may have a reddened area, a bruise, UREMIA or swelling at the site of impact, although often consciousness 245 there are no outward indications that a concus- Risk Factors and Preventive Measures sion has occurred. The most common causes of concussion are MOTOR VEHICLE ACCIDENTS, team sports (especially contact Because the potential for serious BRAIN sports such as football and boxing), bicycle acci- damage exists even with an apparently dents, and shaking an infant or young child. minor concussion, a person who experi- ences a blow to the head that results in Never shake an infant or young child, loss of CONSCIOUSNESS or symptoms of even in play. Infants and young chil- concussion that last longer than 15 min- dren are particularly vulnerable to utes should undergo examination by a BRAIN injury that can occurs with force- physician. ful shaking (shaken baby syndrome). The damage can cause concussion or, The diagnostic path includes a basic NEUROLOGIC when severe, be permanent or fatal. EXAMINATION to assess the person’s level of CON- SCIOUSNESS and REFLEX responses. The doctor may Collisions and crashes when downhill skiing, conduct diagnostic imaging procedures such as snowboarding, roller skating, inline skating, and COMPUTED TOMOGRAPHY (CT) SCAN or MAGNETIC RESO- skateboarding are also common causes of concus- NANCE IMAGING (MRI) to determine whether there is sion. Measures to reduce the risk for concussion active bleeding within the brain and to assess the and other injuries include using appropriate per- extent of damaged tissue when the concussion is sonal protective equipment and devices, such as severe. The doctor may also conduct an ELECTROEN- safety belts and helmets; following safety proce- CEPHALOGRAM (EEG) to assess the brain’s electrical dures and regulations; and proper training and activity. technique when participating in sporting activities. See also TRAUMA PREVENTION; TRAUMATIC BRAIN GRADING OF CONCUSSION INJURY (TBI). grade 1 brief confusion but no loss of CONSCIOUSNESS consciousness A state of awareness of one’s grade 2 extended confusion and little or no memory of external environment, typically when a person is the event that caused the concussion but no awake and the cerebrum (the largest part of the loss of consciousness BRAIN responsible for sensory, voluntary, and cog- nitive functions) is fully functional. Most grade 3 loss of consciousness lasting a few minutes to researchers believe consciousness results from the several hours with brief to extended confusion interactions of physiology, chemistry, cognition, upon return of consciousness and no memory and memory. However, scientists do not fully of the event that caused the concussion understand how consciousness occurs. A clinical assessment of consciousness typically incorporates Treatment Options and Outlook measures of how well a person is oriented to cur- Treatment is generally watchful waiting. The doc- rent events and surroundings. Altered states of tor may choose to hospitalize the person for close consciousness range from sleep, from which a per- medical observation or may recommend regularly son is easily aroused, to COMA, from which a per- arousing the person for 24 to 48 hours to monitor son cannot be aroused. A network of nerves in the the person’s ability to exhibit full consciousness. brainstem, midbrain, and cerebral cortex, the Most concussions are mild and recovery is com- reticular-activating system (RAS), is primarily plete. However, severe or repeated concussions responsible for regulating the level of conscious- can lead to permanent brain damage or even ness. death. It is important to monitor a person who has See also COGNITIVE FUNCTION AND DYSFUNCTION; had a concussion for changes in alertness, behav- DELIRIUM; HALLUCINATION; MEMORY AND MEMORY ior, and symptoms such as headache and to seek IMPAIRMENT; PERSISTENT VEGETATIVE STATE; UNCON- medical reevaluation if they occur. SCIOUSNESS. 246 The Nervous System cranial nerves The 12 paired nerves that origi- tory epithelium, a structure of hairlike extensions nate within the cranium (skull). The cranial which respond to scent molecules that enter the nerves convey sensory signals and control motor NOSE. The second cranial nerves, the optic nerves, functions primarily for the head, neck, and face. originate at the front of the brain near the olfac- Cranial NERVE X, also called the vagus nerve, tory bulbs. The OPTIC NERVE fibers converge into serves the organs of the trunk as well. The cranial the optic tracts that terminate as they enter the nerves and the SPINAL NERVES combined make up retinas of the eyes. the PERIPHERAL NERVOUS SYSTEM, dividing and Cranial nerves VIII, the vestibulocochlear branching throughout the body to extend nerve nerves, are the third purely sensory pair of cranial fibers to all tissues. nerves and arise from the brainstem near the When identifying the cranial nerves numeri- juncture of the pons and the medulla oblongata. cally, neurologists generally use Roman numerals The vestibulocochlear nerve travels parallel to cra- I through XII to refer to the cranial nerves or des- nial nerve VII, the facial nerve, through a portion ignate them as first cranial nerve, second cranial of the fallopian channel (a narrow tunnel through nerve, and so forth. The numbers of the cranial the cranium) as each leaves the brain. Each nerves designate the cranial nerves in order from vestibulocochlear nerve has two branches, one the front to the back of the BRAIN and brainstem. that terminates within the cochlea, responsible for Cranial nerve IV, the trochlear nerve, is the small- hearing, and one that terminates within the struc- est, and cranial nerve V, the trigeminal nerve, is tures of the vestibule, responsible for balance. the largest of the cranial nerves. Cranial nerve X Cranial nerve pairs III through VII and IX has the most diverse and extensive functions. through XII originate from clusters of cells within structures of the brainstem. Cranial nerves III Types of Cranial Nerves (oculomotor nerves), IV, VI (abducens nerves), XI Cranial nerves are sensory, motor, or mixed (con- (spinal accessory nerves), and XII (hypoglossal vey both sensory and motor signals). Sensory nerves) have purely motor functions. The remain- nerves or nerve components are afferent; they ing cranial nerves—V, VII, IX (glossopharyngeal), conduct signals from the body to the brain and and X—have mixed sensory and motor functions. may be general (conveying sensory information such as temperature and PAIN) or special (convey- Conditions That Can Affect the Cranial Nerves ing sensory information for sight, hearing, taste, Damage to the cranial nerves may result from or smell). Motor nerves or nerve components are trauma, INFLAMMATION, INFECTION, AUTOIMMUNE DIS- efferent; they conduct signals from the brain to ORDERS, and tumors. Depending on the nerve the body and may be somatic (serving striated or affected the consequences may be disturbances of voluntary MUSCLE), visceral (serving the smooth sensory perceptions, such as altered taste or muscle of internal organs), or branchial (serving diminished smell, or disturbances of motor func- the structures that arise from the embryonic gill tion, such as the facial PARALYSIS of BELL’S PALSY arches, which are primarily the structures of the (damage to cranial nerve VII). HERPES ZOSTER lower face, jaw, and THROAT). The cranial nerves (shingles) frequently affects cranial nerve V, caus- cross before leaving the brain and brainstem, serv- ing extreme pain along the involved DERMATOME ing structures on the opposite side of the body. (pattern of nerves) of the face. ACOUSTIC NEUROMA is a noncancerous, slow-growing tumor affecting Origins and Paths of the Cranial Nerves cranial nerve VIII that causes progressive HEARING Cranial nerves I and II are special sensory nerves. LOSS. The first cranial nerves, the olfactory nerves, origi- For further discussion of the cranial nerves nate in the olfactory bulbs at the front of the within the context of the structures and functions brain, in a region sometimes called the rhinen- of the NERVOUS SYSTEM, please see the overview sec- cephalon. The olfactory nerve fibers unify to tion “The Nervous System.” become the olfactory tracts as they pass along the See also CENTRAL NERVOUS SYSTEM; SMELL AND underside of the brain and terminate in the olfac- TASTE DISORDERS; SPINAL CORD. cranial nerves 247

THE CRANIAL NERVES Cranial Nerve Pair Type Functions I—olfactory nerve sensory (special) sense of smell

II—optic nerve sensory (special) sense of sight

III—oculomotor nerve motor (somatic) muscles that move the EYE up and down and side to side muscles that adjust the LENS motor (visceral) muscles that constrict the pupil

IV—trochlear nerve motor (somatic) muscles that move the eye in a circular motion (superior oblique)

V—trigeminal nerve sensory (general) general sensations of the face, surface of the head, MOUTH, surface of the eye, mucous membranes of the NOSE and THROAT, front two thirds of the tongue, and jaw muscles motor (somatic) muscles of chewing

VI—abducens nerve motor (somatic) muscles that move the eye side to side (lateral rectus)

VII—facial nerve sensory (general) general sensations of the face, surface of the head, and front two thirds of the tongue sensory (special) sense of taste, front two thirds of the tongue motor (somatic) muscles that control facial expression motor (visceral) muscles that regulate the flow of tears and saliva

VIII—vestibulocochlear nerve sensory (special) sense of balance (vestibular function of the inner EAR) sense of hearing (cochlear function of the inner ear)

IX—glossopharyngeal nerve sensory (general) general sensations of the back of the tongue, back of the throat, and surface of the eardrum sensory (special) sense of taste, back part of the tongue and palate motor (visceral) carotid body (arterial baroreflex sensors for BLOOD PRESSURE) muscles of the throat for swallowing and GAG REFLEX muscles of the tear glands muscles of the SALIVARY GLANDS

X—vagus nerve sensory (general) general sensations for the bronchial structures, gastrointestinal tract, outer ear, and throat sensory (special) sense of taste from the back of the palate motor (visceral) muscles of the heart’s ventricles muscles of the gastrointestinal tract muscles of the bronchial structures muscles of the throat

XI—spinal accessory nerve motor (somatic) muscles of the neck that move the head

XII—hypoglossal nerve motor (somatic) muscles that move the tongue and back of the throat for swallowing and speech 248 The Nervous System

Creutzfeldt-Jakob disease (CJD) A rare degen- The discovery of infectious prions has caused erative, and at present fatal, BRAIN condition that some researchers to suspect that these protein par- results from the distortion and malfunction of pro- ticles cause nearly all CJD. Researchers do not teins in the brain. Protein particles called prions know, however, how most people would acquire appear to be the responsible agents. Prions are infectious prions. Only about 110 people world- infectious, meaning they can pass from one per- wide (mostly in England where BSE first surfaced) son to another to cause disease. CJD is a brain- are known to have died from CJD acquired wasting disease that destroys brain tissue, leaving through eating BSE-contaminated beef. About spongelike holes throughout the brain. Doctors 150 people worldwide are known to have died diagnose about 300 cases of CJD a year in the from iatrogenic CJD acquired through medical United States, though many researchers feel this is procedures. Health-care providers and suppliers of an inaccurate representation of how many people donor tissues and products now follow more strin- develop the condition because diagnosis can take gent preparation and sterilization techniques to place only by examining brain tissue at autopsy. kill infectious prions. These measures significantly Autopsy is not a standard procedure in the United reduce, though do not eliminate, the risk of States or in most countries. acquired CJD. Though known to doctors for more than a cen- tury, CJD came to international prominence in the Symptoms and Diagnostic Path early 1990s with the discovery that a form of Though the incubation period for CJD is typically prion infection in cows, bovine spongiform very long (10 to 25 years), once symptoms encephalopathy (BSE), could be transmitted to develop the course of the disease is quite rapid. humans through consumption of meat in which Symptoms tend to appear with dramatic sudden- the nervous tissues present in the meat contained ness and include infectious prions (infectious prions occur only in nervous tissue). Researchers designated this form • erratic behavior and emotional outbursts as variant CJD (vCJD) to distinguish it from the • memory disturbances classic form of CJD. • DEMENTIA Another form of CJD is iatrogenic CJD in which an individual acquires the disease as a • loss of motor function (jerky movements and result of medical treatments using tissues from a unsteady gait) cadaver donor with had undiagnosed CJD. Cur- • cognitive dysfunction rent methods for harvesting such tissues and sub- stances, notably dura mater for transplantation The diagnostic path includes a comprehensive and human growth HORMONE (hGH) extracted PERSONAL HEALTH HISTORY to determine any family from cadaver PITUITARY GLAND, now include proce- history or exposures that suggest CJD as well as dures to reduce the risk for INFECTION. imaging procedures such as COMPUTED TOMOGRAPHY CJD is a difficult disease to track to its origins (CT) SCAN and MAGNETIC RESONANCE IMAGING (MRI), because the time from onset to show of symptoms which can show the damage in the brain. The can be several decades. Before BSE (also called neurologist makes the diagnosis on the basis of “mad cow disease”) focused attention on CJD, clinical findings, including the progression of doctors believed the malformed proteins charac- symptoms, after ruling out other causes. Definitive teristic of CJD occurred spontaneously in individ- diagnosis can be made only by analysis of brain uals who perhaps had a GENETIC PREDISPOSITION for tissue after death. such damage or had unknown environmental exposure that set the chain of events in motion. Treatment Options and Outlook Some forms of CJD appear to have a genetic com- All forms of CJD are, at present, progressive and ponent as they tend to run in families, and fatal. Treatment is primarily palliative, aiming to researchers have identified GENE mutations that improve the person’s comfort and QUALITY OF LIFE produce the defective proteins. to the extent possible. CJD typically results in loss Creutzfeldt-Jakob disease (CJD) 249 of neurologic function that leads to death within CJD through donated blood and blood products, two years after symptoms appear. though the risk has been well established for cer- tain kinds of tissues and extracted substances. Risk Factors and Preventive Measures Many countries now have strict regulations for Because the transmission of prion infections the raising and slaughtering of cattle, as well as remains uncertain, the United States and many testing for the presence of BSE. These regulations countries in Europe have imposed strict guidelines are constantly evolving. for tissue and blood donation. Health experts dis- See also COGNITIVE FUNCTION AND DYSFUNCTION; agree as to whether there is a risk for acquiring FOOD SAFETY. D deep brain stimulation A surgical procedure to can respond to the neurosurgeon’s directions and treat tremors in disorders such as PARKINSON’S DIS- report any unusual effects. The neurosurgeon typ- EASE and benign essential tremor. In such condi- ically has the person hold a small object to moni- tions, researchers believe the BRAIN structures tor improvement of the tremors with the responsible for fine motor movement become electrode’s placement and activation. During the unable to block extraneous NERVE signals, allowing third and final stage of the operation the neuro- far more nerve signals to reach the muscles. The surgeon implants the pulse generator into a overstimulation results in the tremors. Deep brain pocket of tissue beneath the clavicle (collarbone) stimulation generally becomes a viable treatment under local or sometimes general ANESTHESIA and option when noninvasive measures are no longer runs the other end of the insulated wire under the successful in controlling tremors and the tremors skin to connect at the pulse generator. The neuro- are severe enough to disrupt daily living. The neu- surgeon uses a computer to program the pulse rosurgeon implants a thin wire with electrodes at generator to deliver the appropriate STRENGTH and the tip into the thalamus or subthalamic nucleus, rate of electrical impulses. structures of the brainstem responsible for fine The operation lasts about 90 minutes. The neu- motor movement. A battery-powered pulse gener- rosurgeon removes the stereotactic halo when the ator then sends electrical signals to the electrodes. operation is finished. Minor side effects, usually The signals block the thalamus or subthalamic temporary, may include tingling and balance dis- nucleus from sending extraneous nerve signals to turbances from the wire passing through the the muscles, which slows or stops the tremors. brain. Complications are rare; when they do occur The first step of deep brain stimulation surgery they may include excessive bleeding and postop- is the placement of a stereotactic halo, a circular erative INFECTION. Most people return to full and brace the neurosurgeon attaches to the person’s regular activities within two weeks. The batteries skull with local anesthetic to numb the areas of in the pulse generator last about five years, after the skull where the halo attaches. The halo holds which the neurosurgeon replaces the pulse gener- the instruments in precise position during the ator and batteries together. Deep brain stimulation OPERATION. The second step of the surgery is typically provides long-term relief from tremors, implanting the electrodes. After injecting a local though in degenerative conditions such as Parkin- anesthetic to numb the SKIN and periosteum cov- son’s disease the benefit eventually diminishes as ering the cranium (which are the only areas that the condition progresses. contain nerves sensitive to PAIN), the neurosur- See also QUALITY OF LIFE; SURGERY BENEFIT AND RISK geon drills a tiny hole and inserts a very thin insu- ASSESSMENT; TREMOR DISORDERS. lated wire, feeding it slowly to the thalamus or subthalamic nucleus, using MAGNETIC RESONANCE delirium A state of extreme confusion generally IMAGING (MRI) to visualize and guide the path of resulting from reversible causes. Delirium appears the wire. to result from multiple imbalances in the brain’s The person remains conscious and relatively neurotransmitters. The causes of these imbalances aware during this part of the surgery, so he or she are generally multiple or complex, such as the 250 dementia 251 metabolic disruptions that are the hallmark of the midbrain. Because the midbrain handles func- withdrawal from prolonged ALCOHOL INTOXICATION tions related to basic emotional response (such as (delirium tremens). Other metabolic disturbances, fear and anger) and basic motor function, Lewy such as occur with LIVER FAILURE (hepatic body dementia typically produces symptoms that ENCEPHALOPATHY) or ketoacidosis of DIABETES, also appear a blend of Parkinson’s disease and cause delirium. Some people experience delirium Alzheimer’s disease. Some researchers believe the as a reaction to general ANESTHESIA or certain med- three conditions may share common origins, ications, or as a consequence of very high FEVER. though the mechanisms of their relationship People who are elderly are more vulnerable to remain undetermined. delirium, though delirium may occur at any age. Vascular dementia STROKE, TRANSIENT ISCHEMIC The presentation of delirium, which varies ATTACK (TIA), BRAIN HEMORRHAGE, carotid ATHERO- widely, is often difficult to distinguish from that of SCLEROSIS, and cerebral vascular disease (athero- disorders such as DEMENTIA. A person experiencing sclerosis affecting the arteries within the brain) delirium may exhibit DELUSION, HALLUCINATION, dis- deprive areas of the brain of the BLOOD supply they orientation, restlessness, and inability to concen- require to remain functional. Brain neurons can trate. The person’s recent health history, including survive only a short time (three minutes or less) history of substance abuse or ALCOHOLISM, gener- without oxygen; the body cannot replace lost neu- ally provides the determining information. BLOOD rons as it can certain other types of cells. tests may show electrolyte or GLUCOSE (sugar) Traumatic brain injury Injury to the brain imbalances. The diagnostic path focuses on finding such as may occur in MOTOR VEHICLE ACCIDENTS may the underlying cause. Delirium nearly always permanently damage areas of the brain. TRAUMATIC resolves when the doctor identifies and treats the BRAIN INJURY (TBI) is the most common cause of underlying cause. dementia in people under age 60. Depending on See also COGNITIVE FUNCTION AND DYSFUNCTION; the extent and location of the injury, it is some- PSYCHOSIS. times possible to retrain other areas of the brain to carry out some of the lost cognitive functions. dementia The loss of cognitive function resulting from changes in the structure of or damage to the Symptoms and Diagnostic Path BRAIN. Metabolic disturbances that create biochem- The symptoms of dementia may appear gradually ical imbalances in the body, such as chronic CIRRHO- or suddenly depending on the cause. They typi- SIS, may alter the brain’s biochemistry as well, cally include establishing transient dementia (dementia that goes away when the underlying imbalance returns • loss of memory, which may manifest in terms to normal). An ADVERSE REACTION to medication or of forgetfulness, failure to recognize familiar interaction among medications may also produce people and places, and inability to carry out symptoms of dementia that typically end when the familiar activities such as cooking or driving to person stops taking the medication. Most often, the store however, dementia represents permanent loss of • inappropriate behavior, such as outbursts of abilities related to thought, memory, logic, analysis, anger calculation, planning, and organization. • inability to find the right words when speaking Degenerative neurologic disease ALZHEIMER’S DIS- • personality changes EASE, PARKINSON’S DISEASE, HUNTINGTON’S DISEASE, and other progressive, degenerative conditions affect- • inability to make basic decisions, such as which ing the brain are the primary causes of dementia. shirt to wear or what to eat These conditions cause the death of neurons in • pronounced decline in PERSONAL HYGIENE areas of the brain that conduct cognitive activities (bathing and wearing clean clothes) and are the most common causes of dementia. Lewy body dementia Lewy bodies are abnor- The diagnostic path begins with a comprehen- mal protein deposits that form in the structures of sive medical examination to look for common and 252 The Nervous System easily remedied causes for the symptoms. Among vey motor signals to and sensory signals from the such causes might be undiagnosed conditions such body. The body’s dermatome pattern is fairly con- as HYPOTHYROIDISM, DIABETES, vitamin B12 defi- sistent among individuals though each person has ciency, neurosyphilis, and medication reactions or subtle unique characteristics. Identifying the interactions. The doctor will also take a careful involved dermatome for chronic PAIN, MUSCLE medical history, looking for evidence of recent weakness, or PARALYSIS helps the neurologist deter- injury or trauma or of family history of conditions mine the region of the spine where the damage such as Parkinson’s disease and Alzheimer disease. originates. This is particularly useful for therapies The doctor may conduct diagnostic imaging proce- such as NEURAL BLOCKADE (NERVE BLOCK) and RHIZO- dures such as MAGNETIC RESONANCE IMAGING (MRI) TOMY, which are treatments for intractable pain or and COMPUTED TOMOGRAPHY (CT) SCAN to rule out spasticity. The body’s dermatome has the appear- BRAIN TUMOR, brain hemorrhage, or stroke. ance of a topographic map when rendered as a Dementia is generally a clinical diagnosis based on visual representation. symptoms and on ruling out treatable causes of A dermatome is also a bladed surgical instru- the symptoms. ment used to remove very thin layers of SKIN such as for skin transplantation. Treatment Options and Outlook See also CEREBRAL PALSY; COMPLEX REGIONAL PAIN Treatment and outlook vary with the cause of the SYNDROME; SPINAL CORD INJURY. dementia. Metabolic dementia is often transient, with normal brain function returning when treat- dyskinesia Abnormal, involuntary movements. ment restores the body’s metabolic balance. Dyskinesia results from damage to the structures Dementia that results from injury to the brain or within the BRAIN responsible for motor movement neurodegenerative conditions such as Alzheimer’s and coordination, notably the basal ganglia. disease is generally permanent. Treatment aims to ATHETOSIS, CHOREA, DYSTONIA, MYOCLONUS, tics, and improve remaining cognitive abilities through tremors are all forms of dyskinesia that may activities that use and exercise the brain, such as appear in neurologic disorders such as PARKINSON’S reading and crossword puzzles. Adaptive measures DISEASE, HUNTINGTON’S DISEASE, TOURETTE’SSYN- may also help, such as writing out instructions or DROME, RESTLESS LEGS SYNDROME, CEREBRAL PALSY, and drawing maps or pictures. Persistent, and particu- essential benign tremor. Abnormally slow move- larly progressive, dementia may result in loss of ments are bradykinetic (bradykinesia) and abnor- independent function. mally rapid movements are hyperkinetic (hyperkinesis). It is common for people who have Risk Factors and Preventive Measures neuromotor disorders to have more than one form Age is the primary risk factor for dementia. About of dyskinesia. Medications such as anticholinergics half of people over age 85 have Alzheimer’s dis- and MUSCLE relaxants can sometimes improve ease, the leading cause of dementia. Lewy body dyskinesia. dementia and vascular dementia also become sig- Tardive dyskinesia is a form of dyskinesia that nificantly more common with advanced age. develops with long-term use of DOPAMINE antago- Appropriate medical and lifestyle management of nist medications, which block dopamine from conditions such as HYPERTENSION (high BLOOD PRES- reaching dopamine receptors in the brain. SURE), atherosclerosis, LIVER disease, and diabetes Dopamine antagonists are the convention of treat- helps mitigate their health consequences. ment for Parkinson’s disease. Many ANTIPSYCHOTIC See also COGNITIVE FUNCTION AND DYSFUNCTION; MEDICATIONS to treat SCHIZOPHRENIA and other seri- CREUTZFELDT-JAKOB DISEASE; DELIRIUM; MEMORY AND ous psychiatric illnesses also are dopamine antago- MEMORY IMPAIRMENT. nists. Tardive dyskinesia is often irreversible. See also TREMOR DISORDERS. dermatome A region of the body a specific, sin- gle spinal NERVE root serves. The SPINAL NERVES con- dyslexia See LEARNING DISORDERS. E electroencephalogram (EEG) A diagnostic pro- ened room while the technologist allows the EEG cedure that records the electrical activity of the machine to record the electrical impulses the elec- BRAIN. The neurologist uses EEG to assess the trodes pick up and conduct to the machine. The brain’s function. Electrodes attached to the scalp technologist may use flashing or steady light to detect the brain’s electrical impulses and carry the stimulate areas of the brain. A typical diagnostic signals to the EEG machine. An amplifier converts EEG of the brain may take 15 to 90 minutes to the impulses into patterns that the machine complete. records either in analog form (in which styluses The different regions of the brain generate create tracings on a slowly moving roll of paper) characteristic patterns of electrical activity, meas- or digital form (in which a computer creates an ured in Hertz (Hz). EEG typically captures five electronic record). types of electrical activity or brain waves:

Reasons for Doing This Test • Alpha waves are 8 to 13 Hz, originate from the Neurologic conditions, from BRAIN HEMORRHAGE to forward lobes, normally are present only when BRAIN TUMOR to SEIZURE DISORDERS, cause predictable the eyes are closed, and form a moderate- and detectable deviations from the normal electri- amplitude symmetrical pattern. cal patterns. EEG also shows the level of electrical • Beta waves are 2 to 13 Hz, originate from the activity in the brain of a person who is UNCON- back lobes, normally are present during wake- SCIOUS, in a COMA, or in a PERSISTENT VEGETATIVE fulness, and form a low-amplitude symmetrical STATE. The neurologist must interpret the EEG pattern. findings in context with the person’s age, PERSONAL HEALTH HISTORY, medications, and other clinical • Delta waves are 0 to 4 Hz, normally are present findings to arrive at a diagnosis. only during deep sleep, and form a high-ampli- tude symmetrical pattern. Preparation, Procedure, and Recovery • Theta waves are 4 to 8 Hz, normally are present EEG generally requires no preparation or recovery during the transition from wakefulness to and does not cause discomfort. To conduct the sleep, and form a moderate-amplitude erratic EEG, the technologist first measures the scalp to pattern. determine the sites for placing the electrodes. The sites represent a standard pattern, the most com- • A pattern of spikes and waves is always abnor- mon of which is called the 10/20 system in refer- mal, features erratic amplitude and cycle, and ence to the relationships among the sites. A key of typically indicates a seizure disorder. letters and numbers denote the lobe and the elec- trode’s position. The technologist then attaches Risks and Complications electrodes to locations on the scalp. Small dots of There are no risks or complications from EEG. glue hold the electrodes in place; the glue may be There is no discomfort from attaching the elec- difficult to remove when the EEG is over. During trodes or during the recording process. Sometimes the EEG the person lies on a table in a quiet, dark- removing the electrodes pulls the HAIR, and the 253 254 The Nervous System glue used to attach the electrodes to the scalp may the structures of the brain and detect any abnor- be difficult to cleanse from the hair. malities. See also APNEA; NEUROLOGIC EXAMINATION; SLEEP Treatment targets the underlying condition. DISORDERS. Some forms of encephalopathy are reversible, though encephalopathy may be an end-stage cir- encephalopathy Widespread (as opposed to cumstance in conditions such as LIVER failure or localized) dysfunction of the BRAIN. Encephalopa- RENAL FAILURE. Encephalopathy resulting from thy may be short term and temporary or result degenerative neurologic conditions such as from irreversible damage to the brain such as can CREUTZFELDT-JAKOB DISEASE (CJD) is not reversible. occur with metabolic, infectious, and degenerative Many people who recover from encephalopathy diseases. Symptoms of encephalopathy include have no long-term residual effects. Some people may have persistent symptoms such as cognitive • personality changes dysfunction or mood swings, or may develop • mood swings SEIZURE DISORDERS. • cognitive dysfunction CONDITIONS ASSOCIATED WITH ENCEPHALOPATHY • memory impairment ALCOHOLISM ALZHEIMER’S DISEASE • slurred speech BRAIN HEMORRHAGE BRAIN TUMOR • disorientation CIRRHOSIS CREUTZFELDT-JAKOB DISEASE (CJD) • UNCONSCIOUSNESS or COMA DRUG OVERDOSE ENCEPHALITIS END-STAGE RENAL DISEASE (ESRD) Hashimoto’s THYROIDITIS The diagnostic path begins with a comprehen- HEAVY-METAL POISONING HEMATOCHROMATOSIS sive medical examination, discussion of PERSONAL HYPERTENSION HYPOXIA HEALTH HISTORY, and basic NEUROLOGIC EXAMINATION. ILLICIT DRUG USE LIVER FAILURE BLOOD tests to measure electrolytes, enzymes, PARKINSON’S DISEASE POLIOMYELITIS blood composition, GLUCOSE and INSULIN levels, and STROKE WILSON’S DISEASE HORMONE levels can provide clues as to whether there is a condition of metabolic imbalance. The See also DEMENTIA; END OF LIFE CONCERNS; doctor may conduct diagnostic imaging proce- LIFESTYLE AND HEALTH; ORGANIC BRAIN SYNDROME. dures such as COMPUTED TOMOGRAPHY (CT) SCAN or MAGNETIC RESONANCE IMAGING (MRI) to visualize epilepsy See SEIZURE DISORDERS. G–H

Guillain-Barré syndrome A rare disorder in and findings allow the neurologist to make a clini- which the IMMUNE SYSTEM attacks the myelin cal diagnosis. sheaths of the PERIPHERAL NERVES, causing weakness or PARALYSIS, diminished reflexes, and loss of feel- Treatment Options and Outlook ing. The loss of myelin strips the NERVE axons of Treatment is primarily supportive though some insulation, inhibiting their ability to conduct elec- people improve with intravenous IMMUNOGLOBULIN, trical impulses. Doctors do not know what causes which helps restore normal immune system func- Guillain-Barré syndrome but believe it is a compli- tion, or plasmapheresis, which removes antibodies cation of bacterial or viral INFECTION. The most from the BLOOD. Most people require hospitaliza- common association is with Campylobacter jejuni, tion. About 30 percent of people require tempo- which causes the foodborne illness CAMPYLOBACTE- rary MECHANICAL VENTILATION until function returns RIOSIS. Other associations are with INFLUENZA, PNEU- to the muscles that conduct breathing. MONIA, GASTROENTERITIS, and some vaccinations. About 85 percent of people make a complete recovery, without residual effects, in six months to Symptoms and Diagnostic Path a year though may need PHYSICAL THERAPY and Symptoms typically are acute, beginning 7 to 10 other supportive treatment to regain MUSCLE days after the precipitating event (such as viral STRENGTH and function. About 10 percent of people infection) and reaching peak severity within 14 have residual neurologic complications such as days. Commonly, tingling and weakness, and altered sensation or weakness of the hands and sometimes PAIN, begin with the feet and move sym- feet. Very rarely, paralysis persists. Guillain-Barré metrically up the body. The weakness may become syndrome is fatal in about 5 percent of people, paralysis, depending on the extent of demyeliniza- usually in those who are older (age 65 or more) or tion that takes place. Some people experience mild who experience very rapid progression to com- symptoms and others experience symptoms that plete paralysis and respiratory failure. result in complete paralysis including respiratory distress. Some people experience irregularities in Risk Factors and Preventive Measures HEART RATE, RESPIRATION RATE, BLOOD PRESSURE, and About two thirds of people recall a viral or bac- other autonomic functions. About half of people terial infection within 2 to 12 weeks of their neu- who develop Guillain-Barré syndrome have mod- rologic symptoms. The most significant risk for erate to severe pain with movement. Guillain-Barré syndrome is C. jejuni infection The diagnostic path includes careful assessment (campylobacteriosis). CYTOMEGALOVIRUS (CMV), of recent PERSONAL HEALTH HISTORY, notably for viral EPSTEIN-BARR VIRUS (infectious mononucleosis), or bacterial infection, and procedures such as LUM- and varicella-zoster virus (CHICKENPOX) are other BAR PUNCTURE, nerve conduction studies, and COM- infections commonly associated with Guillain- PUTED TOMOGRAPHY (CT) SCAN or MAGNETIC RESONANCE Barré syndrome. There are no measures known to IMAGING (MRI) to rule out other causes of the symp- prevent the syndrome. toms. Though there is no single conclusive test for See also ANTIBODY; MONONUCLEOSIS, INFECTIOUS; Guillain-Barré syndrome, the pattern of symptoms MULTIPLE SCLEROSIS. 255 256 The Nervous System

Huntington’s disease An inherited, degenerative ington’s disease though these changes are not con- disorder of structures in the BRAIN that regulate clusively diagnostic. The only certain diagnostic movement, mood and personality, and cognitive procedure is GENETIC TESTING, done from a sample function and memory. Huntington’s disease fol- of BLOOD, to determine whether the IT-15 gene is lows an autosomal dominant INHERITANCE PATTERN, defective. with each child of an affected parent having a 50 percent chance of inheriting the GENE MUTATION Treatment Options and Outlook that allows the condition to develop. The defective Huntington’s disease is progressive and fatal, gen- gene is IT-15 on CHROMOSOME 4. It causes an alter- erally causing death 15 to 30 years after the onset ation in a protein called the Huntington protein of symptoms. Treatment aims to improve symp- that has a key, though poorly understood, role in toms and QUALITY OF LIFE. Treatment may include maintaining the putamen and the caudate ANTIPSYCHOTIC MEDICATIONS, ANTIDEPRESSANT MEDICA- nucleus, two structures within the basal ganglia. TIONS, ANTIANXIETY MEDICATIONS, and BOTULINUM All people have the Huntington protein; the pro- THERAPY to relieve dystonia. Therapeutic needs and tein’s function becomes defective when the gene effectiveness changes as the disease progresses. that regulates it is mutated. People who have the Emotional support through counseling and SUP- mutation for Huntington’s disease will develop the PORT GROUPS is often helpful for the person who disorder, generally in midlife though occasionally has Huntington’s disease and for family members the disorder manifests in late ADOLESCENCE (juve- and caregivers. Most people who develop Hunt- nile Huntington’s disease). ington’s disease can remain active and independ- Symptoms and Diagnostic Path ent for 10 years or so after the onset of symptoms. Early symptoms of Huntington’s disease are Risk Factors and Preventive Measures general and may not appear related. They include The only risk for Huntington’s disease is genetic. • irritability As yet researchers do not know how to prevent Huntington’s disease from developing in those • DEPRESSION, BIPOLAR DISORDER, or anxiety who carry the mutated gene. Genetic testing to • anger and hostility detect the presence of the gene in people who • diminished energy have a family history of Huntington’s disease but • disturbances of balance and coordination have no symptoms themselves is available; how- ever, it is because there are no known treatments • forgetfulness for the disorder. Though finding the gene is nor- • inability to concentrate mal is a great relief, learning one carries the • delusions and hallucinations mutated gene is often a difficult challenge. Some people prefer to know so they can make appropri- As the disease progresses the neuromuscular ate plans and decisions, including family planning. symptoms become more pronounced and include Health experts strongly recommend GENETIC COUN- DYSKINESIA (notably CHOREA and ATHETOSIS) and DYS- SELING for people who have family history of TONIA. Cognitive dysfunction also becomes promi- Huntington’s disease or symptoms that suggest nent, and the person may no longer recognize Huntington’s disease. familiar places and people. PSYCHOSIS may also See also COGNITIVE FUNCTION AND DYSFUNCTION; increase. DELUSION; END OF LIFE CONCERNS; HALLUCINATION; The diagnostic path includes a comprehensive MEMORY AND MEMORY IMPAIRMENT; PARKINSON’S DIS- medical examination, detailed exploration of PER- EASE. SONAL HEALTH HISTORY and FAMILY MEDICAL PEDIGREE, and NEUROLOGIC EXAMINATION. Diagnostic imaging hydrocephaly Excessive cerebrospinal fluid procedures such as COMPUTED TOMOGRAPHY (CT) within the cranium (skull). Hydrocephaly, also SCAN or MAGNETIC RESONANCE IMAGING (MRI) may called hydrocephalus, may develop for numerous show changes in the brain characteristic of Hunt- reasons, such as congenital BRAIN defects, TRAU- hydrocephaly 257

MATIC BRAIN INJURY (TBI), meningitis, subarachnoid injury) to the brain. Symptoms are difficult to dis- hemmorage, and brain tumors. Untreated or tinguish from those of the underlying condition, uncontrolled hydrocephaly places pressure on the though may include severe HEADACHE, NAUSEA, and structures of the brain and can displace brain tis- VOMITING. sue, causing permanent damage to the brain. In Treatment for hydrocephaly is usually surgery an infant whose cranium has not yet fused, to place a shunt in the brain ventricle to drain the hydrocephaly may cause the head to enlarge as excessive cerebrospinal fluid. The shunt is a small, the pressure of the excessive fluid pushes the rigid catheter that attaches to a one-way valve (to bones outward. prevent cerebrospinal fluid from flowing back into Hydrocephaly occurs when the brain’s ventri- the brain). The valve in turn attaches to a long, cles produce too much CEREBROSPINAL FLUID or thin, flexible catheter that the surgeon channels there is an obstruction that blocks the flow of the beneath the SKIN to drain into the peritoneal cav- fluid through the ventricles and spinal canal. ity. The body then absorbs the fluid. Treatment Diagnostic prenatal ULTRASOUND often detects also targets any underlying causes for the hydro- hydrocephaly in an unborn child. After birth or in cephaly. Usually the shunt is a permanent therapy, adults, MAGNETIC RESONANCE IMAGING (MRI) or COM- though may require periodic replacement. The PUTED TOMOGRAPHY (CT) SCAN can identify hydro- risks of shunting are postoperative infection and cephaly, which most commonly occurs as a deterioration of the shunt, valve, or catheter. complication of INFECTION or blunt trauma (closed See also BIRTH DEFECTS; BRAIN TUMOR; SPINA BIFIDA. L learning disorders Difficulties with cognitive widely, diagnosing learning disorders is often chal- functions such as analytical thinking, reading, lenging. The diagnostic path may incorporate writing, speech, listening, comprehension, and numerous approaches including neurologic, memory. Learning disorders are neurologic and vision, hearing, and speech pathology evaluations; arise from physical disturbances in BRAIN function. psychologic testing; achievement testing; and Such disturbances may be due to abnormalities in classroom observation. It may be difficult to reach brain structure that occur during fetal develop- a clear diagnosis; test results may be inconclusive ment, injuries to the brain that result from oxygen or inconsistent. In the United States, diagnostic deprivation during PREGNANCY or CHILDBIRTH, or testing and remedial or adaptive educational serv- TRAUMATIC BRAIN INJURY (TBI) during childhood. Fre- ices are available at no cost to families for all chil- quently, however, the reason for a learning disor- dren from birth to age 21. der remains unknown. Though social factors influence the extent to which a person who has Treatment Options and Outlook learning disorders is able to overcome challenges, Treatment is often multidisciplinary, integrating such factors do not cause learning disorders. alternate learning approaches with appropriate PHYSICAL THERAPY, speech pathology, OCCUPATIONAL Symptoms and Diagnostic Path THERAPY, and counseling. Treatment efforts may Often the first indication of a learning disorder is a involve the entire family. The rate and extent of gap between a child’s abilities and the abilities that progress varies widely and depends on multiple are normal for the child’s age. Depending on the factors. Many people learn to compensate for their type of disorder, this gap may become apparent learning disorders to the extent that they are able early in childhood or be detected when the child to lead normal, productive lives. For some people, starts school. Symptoms may include a child’s learning disorders present lifelong challenge. inability to Risk Factors and Preventive Measures • speak in sentences by age 3 Because learning disorders result from neurologic • speak clearly enough for others to understand damage, they are very seldom preventable. Appro- by age 3 priate PRENATAL CARE is important to provide opti- mal opportunity for healthy fetal development • tie shoes and fasten buttons by age 5 and growth. Appropriate care during childbirth • sit still through the reading of a short story by and in the immediate newborn stage is especially age 5 crucial. Some learning disorders, such as dyslexia • read and write as expected for age or grade (difficulty reading), appear to run in families, level leading researchers to believe genetic components may be involved. Some learning disorders also involve deficits in See also APHASIA; APRAXIA; ATTENTION DEFICIT motor skills and physical coordination. Because HYPERACTIVITY DISORDER (ADHD); CEREBRAL PALSY; COG- the rate and nature child development varies NITIVE FUNCTION AND DYSFUNCTION; DOWN SYNDROME; 258 lumbar puncture 259

FETAL ALCOHOL SYNDROME (FAS); HEARING LOSS; MEM- brospinal fluid immediately upon the needle’s ORY AND MEMORY IMPAIRMENT; SPEECH DISORDERS. entry, then allows small samples of fluid, usually about three milliliters total, to drip through the lumbar puncture A diagnostic procedure, collo- needle into collection containers. The laboratory quially called spinal tap, in which the doctor will run different tests on each sample. inserts a needle between the lumbar vertebrae in Some people experience discomfort or tingling the lower back to withdraw CEREBROSPINAL FLUID sensations when the doctor inserts the needle into from the spinal canal for laboratory examination. the spinal canal; occasionally the needle contacts a The point of entry into the spinal canal is below spinal NERVE rootlet. When finished collecting fluid the end of the SPINAL CORD, so there is no risk of samples, the doctor withdraws the needle and the needle entering the spinal cord. puts a pressure bandage over the site. Some doc- tors recommend lying flat in bed for three to four Reasons for Doing This Test hours after the lumbar puncture to reduce the risk Cerebrospinal fluid may contain BACTERIA, BLOOD, for postlumbar puncture HEADACHE, though lying or alterations of its composition that may suggest flat does not always prevent this common compli- or confirm numerous conditions affecting the cation. The brain’s ventricles continuously replen- BRAIN and spinal cord such as INFECTION, INFLAMMA- ish cerebrospinal fluid, completely replacing the TION, cancer, certain brain tumors, BRAIN HEMOR- full volume circulating in the brain and spinal RHAGE, and MULTIPLE SCLEROSIS. Lumbar puncture cord three to four times a day. may also return negative results that rule out such The entire procedure takes about 20 minutes. conditions. The doctor may use therapeutic lum- Some results may be available from the laboratory bar puncture to administer medications, such as within a few hours, while other results may take baclofen as treatment for severe spasticity due to several days to several weeks, depending on what cerebral palsy or other neurologic disorders, or tests the doctor requested. CHEMOTHERAPY drugs for certain cancers affecting the brain or spinal cord. Risks and Complications The primary risk of lumbar puncture is introducing Preparation, Procedure, and Recovery bacteria into the cerebrospinal fluid that causes There is no advance preparation for lumbar punc- infection, which occurs rarely. Some people experi- ture. Immediately before the procedure the doctor ence bleeding after the procedure. Headache is the cleanses the area where the needle will enter the most common complication, affecting about one spinal canal. The person may lie on his or her side fourth of people who have lumbar puncture. The with knees drawn to chest, or sit with the head on headache may be mild to severe and typically lasts a pillow that is resting on a table. These postures 24 to 48 hours. Unfortunately PAIN-relief medica- bend the spine in such a way as to open the spaces tions (ANALGESIC MEDICATIONS) do not usually help between the vertebrae. The doctor administers a the headache. Tiredness and backache are also local anesthetic to numb the SKIN at the insertion common for a day or two after the procedure. site. The doctor measures the pressure of the cere- See also BRAIN TUMOR; NEUROLOGIC EXAMINATION. M memory and memory impairment The abilities pus, an area of the temporal lobe, is essential for to recall past events and to anticipate future forming new memories. The hippocampus also is events are hallmarks of the human experience the area of the brain responsible for emotion and and their diminishment an indication of various emotional expression. disorders that affect BRAIN function. Memory is the The mechanisms of short-term memory—infor- process by which the brain stores and retrieves mation the brain retains for seconds to minutes, information. Memory impairment may affect the such as the name of the waiter taking a menu processes of memory storage, memory retrieval, or order or the amount of a purchase—appear to cre- both, and may be temporary or permanent. ate only temporary shifts in neuronal connections. The information has transient (and often time- Mechanisms of Memory Storage and Retrieval limited) value so the brain gives it transient atten- The brain manages memories through multiple tion. The mechanisms of long-term memory— processes, both organic and functional, that memory of events and people from days to involve numerous areas of its lobes and structures. decades ago—create permanent changes in the Most researchers believe the brain stores memo- neuronal pathways among cells in the regions of ries in bits and fragments, which it then reassem- the brain that participate in memory storage and bles when recalling a specific memory. Cognitive retrieval. Once formed, these pathways appear to processes (thought and analysis) and emotion sig- remain intact and fully functional even when nificantly shape memory storage and recall, even, there is no retrieval for extended periods of the some experts believe, to the extent of causing memories they connect. memory errors and false memories. Such memory Researchers categorize long-term memory as mistakes can occur when the brain blends events either explicit (also called declarative) or implicit in the processes of storing and retrieving. Accord- (also called nondeclarative or procedural). Explicit ingly, there is much controversy among medical as memory requires conscious attention to recall well as legal professionals about the objectivity information, such as when taking a test or telling and precision of memory. the story of a childhood event. Explicit memory Storing memories begins with sensory or emo- appears to involve primarily the frontal, temporal, tional NERVE impulses that travel to the brain. Dif- and parietal lobes of the cerebral cortex. Implicit ferent areas of the brain receive, interpret, and memory contains information the brain retrieves encode (prepare for storage) the various kinds of and acts on automatically, without conscious nerve impulses that arrive. Memory is either attention. Riding a bicycle, playing a musical short-term (transient) or long-term (relatively instrument, driving a car, and throwing a ball are permanent). Bridging the two is working memory, common functions of implicit memory. Implicit through which the brain encodes information to memory involves primarily the prefrontal cerebral allow its storage in long-term memory. The extent cortex and the cerebellum, which coordinate vol- to which a person gives attention to incoming untary MUSCLE activity, and the amygdala, a small information helps determine whether and how almond-shaped structure in front of the hip- the information enters memory. The hippocam- pocampus that governs fear and fear response. 260 memory and memory impairment 261

The amygdala also appears to be where face recog- researchers do not fully understand the mecha- nition, in conjunction with emotional associations nisms of memory, they do not fully understand such as love or fear, takes place. how memory impairment occurs. Memory retrieval requires activating, or stimu- The quality of memory, particularly short-term lating, the neuronal pathways that connect the memory, normally diminishes somewhat with stored information. This involves interactions advanced age (age 70 and beyond). Though forget- among neurotransmitters, hormones, and electri- fulness tends to become more common as people cal impulses, though precisely how these interac- get older, significant memory impairment is not an tions happen remains a mystery. Some memory inherent dimension of aging. Much age-associated retrieval occurs in response to external cues and memory impairment results from conditions that stimuli, such as responding to questions or seeing occur with aging. ATHEROSCLEROSIS, in which plaque a familiar face. Implicit memory retrieval appears deposits accumulate in the walls of the arteries to activated by exposure to a circumstance, for narrow the passageways for BLOOD, is among the example getting on a bicycle or behind the wheel leading causes of impaired memory in older adults. of a car. Explicit memories are more complex. Neurologic disorders that affect memory, such as Those with strong emotional connections seem ALZHEIMER’S DISEASE and DEMENTIA, almost exclu- more rapidly and vividly recalled. sively occur in people over age 60. Circumstances that can affect memory in peo- Causes of Memory Impairment ple of any age include BRAIN TUMOR, INFECTION such Everyone experiences occasional forgetfulness, as ENCEPHALITIS or MENINGITIS, systemic neurologic most commonly with respect to recent informa- conditions such as MULTIPLE SCLEROSIS, and disor- tion. Such forgetfulness may range from the ders that alter the body’s chemical balance such as names of newly introduced people to where the LIVER disease or untreated metabolic disorders. car keys are or the driving route to give a co- Memory impairment may be transitory (come and worker a ride home. Many researchers believe go, such as with a TRANSIENT ISCHEMIC ATTACK [TIA]), such forgetfulness represents an incompletion in may return when treatment resolves the underly- the brain’s processes for establishing neuronal ing cause (such as when the brain heals after an pathways. Only when information becomes repe- infection or surgery), or may be permanent titious does the brain create connections among (which occurs when there is tissue damage or loss neurons to accommodate it. The more frequently in areas of the brain that perform functions of a person encounters the same information (such memory, such as often occurs with STROKE or TRAU- as a person’s name), the more complete the neu- MATIC BRAIN INJURY [TBI]). ronal connections among the various regions of the brain that store the information. Forgetfulness CONDITIONS THAT CAN AFFECT MEMORY may also represent the brain’s efforts to “clean ALZHEIMER’S DISEASE ATHEROSCLEROSIS (cerebral vascular house” and maintain efficiency by purging unused BRAIN HEMORRHAGE disease) or extraneous information. CONCUSSION CREUTZFELDT-JAKOB DISEASE (CJD) Memory impairment occurs when the brain DEMENTIA ENCEPHALITIS cannot establish new neuronal pathways to store ENCEPHALOPATHY HUNTINGTON’S DISEASE new memories or use existing neuronal pathways MENINGITIS ORGANIC BRAIN SYNDROME to retrieve memories already stored. A person PARKINSON’S DISEASE SEIZURE DISORDERS experiencing memory impairment may be unable STROKE TRANSIENT ISCHEMIC ATTACK (TIA) to remember the names of close family members TRAUMATIC BRAIN INJURY (TBI) or how to drive home from the store. Though memory and cognition (thought and reason) are Amnesia and memory loss are common terms for distinct functions within the brain, neither is espe- disturbances of memory. Amnesia is the inability cially effective without the other. Correspond- to recall past information or to remember infor- ingly, cognitive dysfunction and memory mation relevant to the future, such as appoint- impairment often occur together. Because ments. Amnesia may result from the inability to 262 The Nervous System retrieve existing memories or to store new memo- as well as when health conditions exist that have ries, and may be temporary (such as following the potential to impair memory. Memory special- CONCUSSION) or permanent. Memory loss is an ists can help individuals develop methods and imprecise term that usually refers to the perma- approaches to maintain optimal memory capabil- nent inability to retrieve information from long- ity as well as to accommodate memory impair- term memory. ment. The herbal products GINKGO BILOBA and GINSENG may improve circulation to the brain, Symptoms and Diagnostic Path resulting in overall improvement of memory and It is normal for people to forget recent information cognitive functions. such as where they placed the car keys or phone numbers they use infrequently. Forgetfulness Risk Factors and Preventive Measures crosses the line to memory impairment when a Diseases, systemic and neurologic, and injuries to person cannot remember information essential for the brain are the primary risk factors for memory daily activities, such as familiar faces and names or impairment. To a great extent, injuries to the brain where he or she lives. The diagnostic path that might result in impaired memory are pre- includes a comprehensive medical examination, ventable through safety measures, such as wear- neurologic examination, and imaging procedures ing appropriate protective headgear and avoiding such as COMPUTED TOMOGRAPHY (CT) SCAN to identify activities with a high risk for head injury. Lifestyle possible organic causes within the brain. Func- factors influence some conditions that can cause tional magnetic resonance imaging (fMRI), a memory impairment, such as HEART ATTACK and dynamic variation of MAGNETIC RESONANCE IMAGING stroke. Chronic ALCOHOLISM contributes to episodic (MRI) that shows the functional activity of the as well as progressive memory loss. Family history brain, may show areas of diminished activity dur- may be a risk factor for neurologic conditions such ing memory tasks. Memory and cognitive tests as Alzheimer’s disease and dementia, for which help identify the kinds of memory affected and there are no known measures of prevention. define remaining memory functions. See also ACCIDENTAL INJURIES; AGING, NEUROLOGIC Treatment Options and Outlook CHANGES THAT OCCUR WITH; ANTI-AGING APPROACHES; Treatment for memory impairment depends on ARTERIOSCLEROTIC PLAQUE; COGNITIVE FUNCTION AND the underlying cause. Memory functions lost due DYSFUNCTION; HYPNOSIS; LEARNING DISORDERS; NEURON; to injury or infection such as encephalitis often POST-TRAUMATIC STRESS DISORDER (PTSD). return as the brain heals. The return commonly takes place in fragments, often with older memo- meninges The connective tissue membranes that ries (such as from childhood) emerging first. enclose and protect the BRAIN and SPINAL CORD (col- Memory impairment due to conditions such as lectively called the CENTRAL NERVOUS SYSTEM). There stroke or Alzheimer’s disease is generally perma- are three meninges: nent. Medications such as the acetylcholinesterase inhibitors doctors prescribe to treat Alzheimer’s • The dura mater is the tough, outermost disease improve memory and cognition in many meninx. It has two layers, a fibrous outer layer people in the early to middle stages of the condi- that attaches to the inside of the cranium (skull tion though do not appear especially effective in bones) and a soft inner layer that contains an treating memory impairment resulting from other extensive network of BLOOD vessels. The dura causes. Permanent memory impairment may also mater sometimes folds back on itself (dural be progressive, as occurs with degenerative condi- reflections) or its layers separate to form pock- tions such as Alzheimer’s disease and PARKINSON’S ets (dural sinuses). DISEASE. • The arachnoid mater is the middle meninx. Exercising memory and cognition, such as with crossword puzzles and other activities that require • The innermost meninx is the pia mater, a tis- storage and recall of information, helps keep these sue-like membrane that covers the surface of abilities as functional as possible in healthy aging the brain. multiple sclerosis 263

CEREBROSPINAL FLUID circulates between the (double vision), blurred vision, impaired color arachnoid mater and the pia mater, in an enve- vision and scotomas (blind spots in the field of lope-like pocket called the subarachnoid space. vision). Other symptoms are neurologic and include DURA MATER GRAFTS AND CJD For several decades neurosurgeons have used • weakness and lack of coordination in the arm grafts of dura mater acquired from cadaver or leg on one side of the body donors to replace dura mater removed during • gait disturbances such as stumbling neurosurgery or in circumstances of extensive • transient PARESTHESIA (tingling or numbness that injury to the BRAIN. In the late 1990s researchers comes and goes without apparent cause) on traced several cases of CREUTZFELDT-JAKOB DISEASE one side of the body (CJD) to the grafts, which had been harvested from individuals who turned out to have CJD. US • intermittent loss of BLADDER control (URINARY Food and Drug Administration (FDA) regulations INCONTINENCE) now establish strict criteria for the harvesting and • emotional lability processing of dura mater grafts to reduce the risk • VERTIGO and dizziness of transmitting infectious conditions such as CJD. • fatigue For further discussion of the meninges within • SEXUAL DYSFUNCTION (notably ERECTILE DYSFUNC- the context of the structures and functions of the TION in men) NERVOUS SYSTEM, please see the overview section “The Nervous System.” Because symptoms are typically transient they See also MENIGITIS. often occur over a number of years before a person seeks medical attention for them. The diagnosis is multiple sclerosis A chronic, progressive primarily one of exclusion so the diagnostic path demyelinating disorder that affects the CENTRAL includes a general medical examination, BLOOD NERVOUS SYSTEM (BRAIN and SPINAL CORD) and the tests, NEUROLOGIC EXAMINATION, LUMBAR PUNCTURE, CRANIAL NERVES, notably the optic nerves. Though and imaging procedures such as MAGNETIC RESO- the cause of multiple sclerosis remains unknown, NANCE IMAGING (MRI) of the brain to rule out other most researchers believe the condition is an potential causes, such as BRAIN TUMOR, of symptoms. autoimmune disorders in which the body’s IMMUNE Imaging procedures, especially MRI, also may show RESPONSE attacks myelin, the fatty substance that the lesions (scarring) that characterize multiple coats nerves. The areas under attack become sclerosis. However, there is no conclusive diagnos- inflamed and separate from the nerves, and as tic test for multiple sclerosis and a person may seek they heal scars form. Over time the SCAR tissue medical care for a number of years before doctors damages the nerves and disrupts the passage of feel confident making the diagnosis. electrical impulses. The progression of demyelina- tion is generally slow, occurring over several Heat often worsens the symptoms of decades. There is wide variation in the severity of multiple sclerosis. For this reason, doc- multiple sclerosis among individuals. Some people tors advise against hot tubs, saunas, experience few symptoms and negligible interfer- exposure to hot weather, and hot show- ence with their regular activities and other people ers or baths. lose control of muscles and mobility. Treatment Options and Outlook Symptoms and Diagnostic Path For most people the course of multiple sclerosis is One of the earliest signs of multiple sclerosis is one of alternating relapse and REMISSION, without RETROBULBAR NEURITIS, an INFLAMMATION of the OPTIC predictability for the frequency or duration of NERVE (second cranial NERVE) that impairs vision. either. Treatment depends on the severity and fre- Indications of retrobulbar neuritis include DIPLOPIA quency of symptoms. People who have mild 264 The Nervous System

MEDICATIONS TO TREAT MULTIPLE SCLEROSIS Drug or Medication Course of Action Concerns/Side Effects interferon beta 1a (Rebif) genetically engineered proteins that direct may cause development of antibodies interferon beta 1b (Betaseron) IMMUNE SYSTEM responses against viruses NAUSEA, VOMITING, MUSCLE aches (flu-like enhances natural immune function symptoms) requires weekly intramuscular injections glatiramer (Copaxone) block IMMUNE RESPONSE from attacking flushing, shortness of breath myelin requires daily subcutaneous injection alternative to beta INTERFERONS corticosteroids (prednisone, suppress immune response HYPERTENSION prednisolone, dexamethasone) reduce INFLAMMATION OSTEOPOROSIS increased risk for INFECTION selective serotonin reuptake stabilize emotions drowsiness, dry MOUTH, sexual side effects inhibitor (SSRI) antidepressants reduce DEPRESSION interactions with other medications (fluoxetine, sertraline, cannot take with tricyclic antidepressants venlafaxine, parocetine) tricyclic antidepressants reduce PAIN drowsiness, dry mouth, sexual side effects (amitriptyline, nortriptyline, reduce DEPRESSION interactions with other medications imipramine, doxepin) cannot take with SSRI antidepressants muscle relaxants (baclofen, reduce muscle spasms drowsiness tizanidine, diazepam, muscle weakness clonazepam)

BOTULINUM THERAPY spasticity that does not respond to other may cause weakness in injected muscles treatment temporarily paralyzes muscles into which it is injected

ANTIVIRAL MEDICATIONS (acyclovir, improve immune system response to may slow attacks Famvir, valacyclovir, amantadine) viruses modafinil reduce drowsiness HEADACHE difficulty sleeping

ANALGESIC MEDICATIONS relieve pain (acetaminophen, NONSTEROIDAL reduce inflammation STOMACH irritation (NSAIDS) ANTI-INFLAMMATORY DRUGS [NSAIDS]) mitoxantrone (Novantrone) CHEMOTHERAPY agent intravenous injection every three months for slows attacks on myelin up to three years extends periods of remission nausea, vomiting muscle aches may increase risk for cardiovascular disease myoclonus 265 episodes of symptoms with extended period of multiple sclerosis, as the condition is far less com- remission, treatment may consist of watchful mon in tropical regions of the world and more waiting and approaches to relieve symptoms that likely to occur when other family members have become troublesome. People who have moderate the condition. However, researchers do not fully to severe episodes of symptoms with short periods understand the connections among these factors. of remission may improve with medications Some researchers believe there may also be specifically for multiple sclerosis. Because these involvement of an as yet undetected VIRUS. There medications have significant side effects, cannot are no known measures for preventing multiple reverse neurologic damage that has already sclerosis. occurred, or halt the progression of multiple scle- See also AMYOTROPHIC LATERAL SCLEROSIS (ALS); rosis, doctors reserve their use for people whose AUTOIMMUNE DISORDERS; GENETIC PREDISPOSITION; symptoms are debilitating. Other medications can LESION; SCAR; SCOTOMA. suppress the body’s immune response, helping slow the attacks. myoclonus Involuntary and episodic contrac- Lifestyle factors such as nutritious EATING HABITS tions, twitching, or spasms of MUSCLE groups. and daily physical activity help maintain motor Harmless manifestations of myoclonus include functions and coordination. WEIGHT LOSS AND brief HICCUPS or the rapid jerking people may WEIGHT MANAGEMENT are essential for people who experience when falling asleep (sometimes called have multiple sclerosis, as maintaining appropriate sleep starts). Myoclonus also may be a symptom of body weight reduces the workload of the muscles. injury to motor neurons, to the NERVE cells in the Regular physical exercise also helps to counter SPINAL CORD that direct voluntary movement, or DEPRESSION. Most people are able to continue with to parts of the BRAIN that participate in move- physical activities they enjoyed before developing ment. Myoclonus occurs as rapid, jolt-like multiple sclerosis. Because heat exacerbates symp- episodes and may take various forms that include toms, people who live in warmer climates may the following: want to use the cooler early morning or late evening hours for physical activities outdoors, and • Action myoclonus occurs or intensifies during use indoor air-conditioned facilities at other times. attempts at voluntary movement, such as walk- Swimming provides good aerobic conditioning as ing or eating. It most commonly develops after well as the opportunity to strengthen weakened circumstances of extended oxygen deprivation muscles in an environment of reduced resistance. to the brain (HYPOXIA), such as may occur with Though it is progressive, multiple sclerosis gen- STROKE, HEART ATTACK, or near drowning. erally does not cause death or shorten life • Essential myoclonus is not associated with any expectancy. Most people who have multiple scle- detectable neurologic injury or dysfunction to rosis are able to participate in the work and leisure account for the symptoms. activities they enjoy when the condition is in • Stimulus-sensitive myoclonus occurs as an remission, and periods of remission may last 10 apparent HYPERSENSITIVITY REACTION (neurologic) years or longer. People who have more aggressive to external stimuli, such as sounds and lights. forms of multiple sclerosis may progress to assisted mobility within a shorter period of time than peo- • Sleep myoclonus occurs when sleep starts ple who have the more classic, slowly progressive become excessive and disruptive to sleep. Some forms of the condition. neurologists believe sleep myoclonus is a form of stimulus-sensitive myoclonus in which the Risk Factors and Preventive Measures person may or may not recognize the external Multiple sclerosis affects twice as many women as stimuli that trigger the myoclonic episodes. men and most commonly makes its first appear- • Cortical reflex myoclonus, reticular reflex ance between the ages of 20 and 40 years. It is myoclonus, and progressive myoclonus likely that external environment (such as climate) epilepsy, are SEIZURE DISORDERS that include and genetics both influence the development of myoclonus among their symptoms. 266 The Nervous System

• Palatal myoclonus occurs when the muscles of binations of muscle relaxants and antiseizure the soft palate at the back of the MOUTH contract medications. Finding a therapeutically effective rapidly and rhythmically though usually with- balance of medications is often a trial-and-error out disrupting the ability to swallow or speak. process. Most people who have myoclonus require lifelong treatment. The pattern and consistency of the myoclonic episodes help the neurologist determine the CONDITIONS IN WHICH MYOCLONUS MAY OCCUR underlying cause or location of the neurologic ALZHEIMER’S DISEASE BRAIN HEMORRHAGE injury (sometimes called a LESION). The diagnostic BRAIN TUMOR CREUTZFELDT-JAKOB DISEASE (CJD) path typically includes a comprehensive NEURO- ENCEPHALITIS MULTIPLE SCLEROSIS LOGIC EXAMINATION and imaging procedures such as PARKINSON’S DISEASE prolonged HYPOXIA MAGNETIC RESONANCE IMAGING (MRI) or COMPUTED SEIZURE DISORDERS SPINAL CORD INJURY TOMOGRAPHY (CT) SCAN to locate or rule out neuro- STROKE TRAUMATIC BRAIN INJURY (TBI) logic damage. The neurologist may also conduct an electromyogram (EMG) to assess the activity of See also ATHETOSIS; CHOREA; NEURON; RESTLESS the affected muscle groups. Treatment aims to LEGS SYNDROME; SPASM; TIC; TOURETTE’S SYNDROME; reduce the symptoms and typically includes com- TREMOR DISORDERS. N–O

narcolepsy A sleep disorder in which a person Some people also benefit from scheduled short feels chronically tired and sleep deprived, and may naps throughout the day, which may provide rest- experience uncontrollable episodes of falling asleep ful sleep as well as decrease feelings of sleepiness. during the day. People who have narcolepsy have Researchers do not know what causes narcolepsy, disturbed sleep patterns while falling asleep, often though there is some evidence that it may be an experiencing premature sleep PARALYSIS (an inabil- Autoimmune disorder because there seems to be ity to move which normally occurs in rapid eye involvement of HUMAN LEUKOCYTE ANTIGENS (HLAS), movement [REM] sleep as a protective mechanism which are fundamental to the IMMUNE RESPONSE. to keep the body from enacting dreams), hypna- There is also some evidence that people who have gogic hallucinations (inability to distinguish narcolepsy have reduced levels of a neuroprotein between dreamlike images and reality when falling called hypocretin. However, researchers do not asleep), and daytime cataplexy (sudden, brief know what these correlations mean or how they episodes of MUSCLE weakness or inability to move). cause narcolepsy. Narcolepsy is a lifelong condition. As well, the person experiences abnormal and very See also APNEA; AUTOIMMUNE DISORDERS; RESTLESS short REM sleep periods (detected through diag- LEGS SYNDROME. nostic sleep studies) that prevent restful sleep. Researchers believe narcolepsy is far more common nerve An organization of connected neurons than diagnosis data suggest because many people that conducts electrical impulses, typically forming do not seek medical evaluation or treatment. the structure of a fiber. The nerve fibers may be The diagnostic path includes a general medical microscopic, such as the nerves that carry examination and basic NEUROLOGIC EXAMINATION to impulses from the fingertips to the BRAIN, or evaluate overall health and neurologic function. clearly visible to the EYE, such as the SPINAL CORD. Diagnostic sleep studies reveal the characteristic The PERIPHERAL NERVES originate in the brain, brain- traits of narcolepsy, distinguishing the disorder stem, and SPINAL CORD and extend to their destina- from other SLEEP DISORDERS. Treatment is a combi- tions in the body. A cluster or mass of nerves nation of medications that may include located outside the CENTRAL NERVOUS SYSTEM (brain and spinal cord) is a ganglion. • AMPHETAMINES (STIMULANTS) to diminish daytime For further discussion of nerves within the con- sleepiness text of the structures and functions of the nervous system, please see the overview section “The Ner- • modafinil, a nonamphetamine DRUG that targets vous System.” different BRAIN functions from amphetamines to improve daytime alertness See also DIABETES; NEURALGIA; NEURITIS; PERIPHERAL VASCULAR DISEASE (PVD). • sleep medications such as flurazepam and other benzodiazepine drugs to encourage relaxation nerve cell See NEURON. when falling asleep • tricyclic antidepressants such as imipramine nervous system The BRAIN and network of and desipramine to improve REM sleep nerves that convey electrical impulses to and from 267 268 The Nervous System all structures in the body. The two major divisions pain. The diagnostic path includes a NEUROLOGIC of the nervous system are the CENTRAL NERVOUS SYS- EXAMINATION and often electromyogram (EMG) to TEM and the PERIPHERAL NERVOUS SYSTEM. The central assess the function of the nerves in the affected nervous system consists of the brain and SPINAL area. The neurologist may conduct diagnostic CORD. The peripheral nervous system consists of all imaging procedures such as COMPUTED TOMOGRAPHY other NERVE structures, including the CRANIAL (CT) SCAN or MAGNETIC RESONANCE IMAGING (MRI)to NERVES, the SPINAL NERVES, and the PERIPHERAL determine whether there is compression of the NERVES. affected nerve, such as from a tumor, or to rule For further discussion of the structures and out other possible causes of the pain. functions of the nervous system, please see the overview section “The Nervous System.” Treatment Options and Outlook See also NEURON; NEURORECEPTOR; NEUROTRANS- Treatment targets the cause when known, such as MITTER. PHYSICAL THERAPY or surgery to relieve compression against a nerve, removal from exposure to poten- neuralgia PAIN that occurs along a DERMATOME tial toxins, or ANTIVIRAL MEDICATIONS for posther- (the tract of a NERVE). Neuralgia is often severe, petic neuralgia. Tricyclic antidepressants are sharp, and brief (each episode lasting 15 seconds particularly effective for relieving the pain of or less) though repetitive. The most common trigeminal neuralgia. Other medications to relieve causes of neuralgia are INFECTION (notably HERPES pain include nonnarcotic and narcotic oral ANAL- ZOSTER, also called postherpetic neuralgia) and GESIC MEDICATIONS, topical analgesics such as cap- compression (a “pinched” nerve). DIABETES, saicin, certain antiseizure medications, topical untreated (tertiary) SYPHILIS, MULTIPLE SCLEROSIS, lidocaine patches, corticosteroid/lidocaine injec- and PORPHYRIA are among the health conditions tions as neural blockades (nerve blocks) and TRIG- that can cause neuralgia. Exposure to toxins, GER-POINT INJECTION. These and other treatments notably heavy metals such as arsenic and lead, can provide relief from the symptoms of neuralgia may cause certain forms of neuralgia. Often, how- for most people. Taking medications, even narcotic ever, the doctor cannot identify the cause of neu- analgesics, on a regular schedule is usually more ralgia. Neuralgia may affect any dermatome in the effective than waiting until pain occurs or body. Those most often affected are the CRANIAL becomes intolerable. ACUPUNCTURE and BIOFEED- NERVES that serve the face and head (especially the BACK are also effective for some people. glossopharyngeal, trigeminal, facial, and occipital), Postherpetic neuralgia generally improves and the intercostal nerves (ribs), and the posterior tib- often resolves (goes away) within 2 to 12 months as ial nerve (ankle and foot). the underlying damage to the involved dermatome heals. Neuralgia due to other causes may persist, Symptoms and Diagnostic Path particularly if the cause is chronic (such as diabetes Neuralgia typically begins with sudden, sharp pain or MULTIPLE SCLEROSIS). When medications and other along the affected dermatome. The attacks may be therapies cannot control the pain (intractable neu- momentarily disabling and last 10 to 15 seconds. ralgia), the neurologist or pain specialist may rec- However, a person may experience dozens of ommend RHIZOTOMY, a surgical OPERATION to cut the sequential attacks in episodes, with periods of nerve rootlets responsible for conducting the pain REMISSION during which there is no pain. The pain is impulses. Such intervention usually, though not always, ends the pain though may also alter sen- • always in the same location sory perception along the dermatome. • near the surface rather than deep in the body • often intense and intermittent, though some- Risk Factors and Preventive Measures times continuous Age is the most significant risk factor for neural- gia, particularly postherpetic neuralgia. Reduced Sometimes touching a particular area on the immune function, especially in people who have SKIN or actions, such as chewing trigger, attacks of HIV/AIDS or take IMMUNOSUPPRESSIVE THERAPY such as neurofibromatosis 269 after ORGAN TRANSPLANTATION, allows the dormant TANCE PATTERN. The tumors, notably those that varicella-zoster VIRUS to emerge and cause shin- involve the SKIN, are initially benign (noncancer- gles. Injuries to the nerves, such as repetitious ous) though have a high risk for turning cancer- motion and compression injuries, also become ous. Neurofibromatosis type 1 (NF-1) is the more more common with advancing age. common form; it generates dozens of tiny tumors. Antiviral medications, such as acyclovir or fam- Neurofibromatosis type 2 (NF-2) primarily ciclovir, taken within 72 hours of the onset of her- involves the SPINAL CORD and eighth cranial NERVE pes zoster symptoms may be effective in (vestibulocochlear nerve). Both forms of neurofi- preventing postherpetic neuralgia. Without antivi- bromatosis may also involve the BONE, skin, MUS- ral therapy, about 20 percent of people who CLE, and connective tissue as well as the BRAIN and develop herpes zoster infection subsequently the visceral organs. develop postherpetic neuralgia. The extent to The earliest sign of neurofibromatosis is often which antiviral therapy for the herpes zoster lightly colored patches of skin (café au lait mac- affects the likelihood of developing postherpetic ules). Many people who have NF-1 develop neuralgia remains unknown. Other preventive numerous small growths that look like moles measures include prompt treatment of NEURITIS (nevi). However, it is possible to press these tumors (INFLAMMATION of a nerve), appropriate intake of below the surface of the skin as though turning vitamin B12 (which is vital for proper nerve func- them into themselves (called a buttonhole effect), tion), and avoidance of toxins that can damage whereas moles and similar growths are firm and the nerves. remain above the skin’s surface when pressed. See also AGING, NEUROLOGIC CHANGES THAT OCCUR Tumors of NF-2 that arise in the spinal cord may WITH; HEADACHE; HEAVY-METAL POISONING; NEURAL cause deformity of the spine and SCOLIOSIS. BLOCKADE (NERVE BLOCK); NEUROPATHY. Because the neurofibromas often develop within the tissues of the brain, other symptoms neuritis INFLAMMATION of a NERVE. Neuritis is usu- may include seizures, intellectual impairment, and ally an indication of an underlying injury or dis- disturbances of motor function. Other symptoms ease process such as irritation, compression, or depend on the locations of the tumors. The diag- INFECTION of the involved nerve. The most com- nostic path includes a comprehensive FAMILY MED- mon symptom is PARESTHESIA (tingling) though ICAL HISTORY; immediate family members who have some people may experience PAIN (NEURALGIA) or similar symptoms or a diagnosis of neurofibro- numbness. The diagnostic path is primarily clini- matosis make the diagnosis fairly conclusive. A cal, based on the person’s symptoms and a NEURO- NEUROLOGIC EXAMINATION and imaging procedures LOGIC EXAMINATION. PAPILLITIS and RETROBULBAR such as MAGNETIC RESONANCE IMAGING (MRI) and NEURITIS, inflammations involving different parts of COMPUTED TOMOGRAPHY (CT) SCAN of the brain may the OPTIC NERVE, can result in vision loss. Retrobul- reveal tumors. bar neuritis can be an early sign of MULTIPLE SCLE- The preferred treatment is surgery to remove ROSIS. Treatment targets the underlying cause and the tumors whenever practical, and close monitor- may include anti-inflammatory medications or ing of tumors that the surgeon cannot remove to ANTIBIOTIC MEDICATIONS; when the cause is compres- assess any changes that could indicate developing sion due to an entrapment syndrome (such as malignancies. Unfortunately the tumors tend to CARPAL TUNNEL SYNDROME), surgery may be neces- recur. Left untreated, however, the tumors often sary to relieve the compression. cause deformity of the tissues and structures in See also SCIATICA. which they are growing. As well, the risk for malignancy is very high. Health experts strongly neurofibromatosis A genetic disorder in which recommend GENETIC COUNSELING for people diag- tumors (neurofibromas) form within the tissues nosed with neurofibromatosis. and structures of the NERVOUS SYSTEM. There are See also ACOUSTIC NEUROMA; BRAIN TUMOR; CRA- two primary forms of neurofibromatosis, both of NIAL NERVES; GENETIC DISORDERS; MACULE; NEVUS; which occur in an autosomal dominant INHERI- PHEOCHROMOCYTOMA. 270 The Nervous System neurologic examination A series of basic diag- the neurons called synaptic corridors. The end of nostic procedures that help the neurologist assess the axon branches into numerous extensions an individual’s neurologic status. A fundamental called presynaptic terminals. The gap between an dimension of the neurologic examination is obser- axon of one neuron and the dendrites of another vation, through which the neurologist can gain neuron is a synapse. much information about a person’s mental status Neurons communicate (conduct nerve (cognition and memory), motor function (balance, impulses) through an electrochemical process coordination, STRENGTH), and sensory perception called action potential, an exchange of electrically (touch, vision, hearing). Specific procedures charged particles (ions) across the cell’s mem- include testing the reflexes, response to specific brane. A neuron at rest contains a negative charge sensory stimuli (soft touch, PAIN, vibration, partic- within its membrane though the environment ular smells or tastes), and the ability to carry out outside the cell membrane carries a positive directed movements (such as tracking the move- charge. A nerve impulse creates a surge or spike of ment of an object or touching specific body loca- electrical energy that causes ion channels in the tions). The neurologist generally performs basic cell membrane to open. At the same time the neu- tests of VISUAL ACUITY and field of vision, hearing, ron releases a chemical messenger, a NEUROTRANS- and examination of the inner EYE. MITTER. Basic assessment of cognitive function and The neurotransmitter binds with the appropri- memory may include reading, spelling, and draw- ate NEURORECEPTOR on the dendrites of the neuron ing activities. Tasks such as unbuttoning and but- intended to receive the nerve impulse. The type of toning, writing one’s signature, and handling neuron—for example, motor or sensory—deter- small objects test dexterity and fine motor move- mines which neurotransmitters and neurorecep- ment. The ways in which a person stands, walks, tors are present. As the neuron’s polarity changes and rises from and lowers to sitting and prone (the neuron achieves action potential), the electri- positions help the neurologist further assess MUS- cal impulse moves to the neuron. The process CLE strength, coordination, and PROPRIOCEPTION takes only a minuscule fraction of a second to (awareness of the body’s position relative to its complete. An enzyme then initiates reuptake environment). The neurologist may conduct other (recycling) of the neurotransmitter, setting the evaluations and procedures, including more stage for the next cycle. Neurons align in neuronal extensive cognitive testing, depending on basic pathways that facilitate the conduction of nerve findings. A basic neurologic examination may take impulses for optimal efficiency. about 20 minutes for the neurologist to complete. Neurons are the oldest cells in the body. Most See also COGNITIVE FUNCTION AND DYSFUNCTION; develop in the early to middle stages of gestation, MEMORY AND MEMORY IMPAIRMENT; REFLEX. with the final surge of neuron production taking place shortly before birth. The body’s full comple- neuron A NERVE cell. A neuron consists of a cell ment of neurons is present at birth, the majority body, nucleus containing the cell’s DNA, cytoplasm, of which survive and function for the course of a organelles (structures within the cytoplasm that full lifetime. The body cannot replace neurons conduct functions such as energy production), that die, and neurons do die at a fairly consistent axons (fibers that carry nerve impulses away from rate, barring injury or disease, of about one per the neuron), and dendrites (rootlike structures day throughout life. that receive the nerve impulses). A myelin sheath See also CELL STRUCTURE AND FUNCTION. (coating of myelin, a fatty substance) may enclose a neuron’s axon, insulating it to maintain the neuropathy Dysfunction of or damage to the integrity of the nerve impulses the axon carries. PERIPHERAL NERVES. Neuropathy may be temporary Dendrites do not have myelin sheaths. An axon or permanent and may result from numerous may extend several inches to several feet, while causes, such as INFECTION, compression, degenera- dendrites remain close to the neuron’s cell body. tive disease processes, and AUTOIMMUNE DISORDERS. Axons and dendrites extend into spaces around Neuropathy may involve only a single peripheral neurotransmitter 271

NERVE (as in compression) or multiple peripheral See also ALTERNATIVE METHODS FOR PAIN RELIEF; nerves, either in a pattern (as in RAYNAUD’S SYN- CRANIAL NERVES; NEURALGIA; NEURITIS; RETROBULBAR DROME or shingles) or diffusely throughout the NEURITIS; RHIZOTOMY; SPINAL NERVES. body (as in neuropathy of DIABETES). Neurologists classify the more than 100 forms of neuropathy neuroreceptor A molecular structure on the into broad categories according to the type of surface of a cell membrane that accepts (binds nerve affected—motor, sensory, mixed, and auto- with) a NEUROTRANSMITTER (chemical messenger). nomic. Nearly always a neuroreceptor is specific for only The symptoms of neuropathy vary widely with one neurotransmitter. The common analogy is the nerves affected and extent of the condition that a neuroreceptor functions like a lock and a causing the neuropathy. PAIN, MUSCLE weakness or neurotransmitter functions like a key; only the loss of muscle function, disturbances of sensory correct key can open the lock. Neuroreceptors perception, and dysfunction of autonomic tend to align along the cell membrane such that processes such as digestion are among the myriad they match across cells, facilitating communica- symptoms that can occur with neuropathy. The tion between cells. Most cells contain numerous diagnostic path typically seeks to identify the and different neuroreceptors. Drugs may also bind underlying cause of the damage, which then with neuroreceptors, causing an effect (partial or becomes the target for treatment methods. Some complete) that emulates that of the matching neu- neuropathies resolve (go away) with appropriate rotransmitter (agonist) or that blocks the neurore- treatment, though often there is some residual ceptor from accepting the neurotransmitter damage as the nerves are delicate and the body (antagonist). Some neuroreceptors have multiple cannot replace neurons that die. binding sites that accept different chemicals (such Because pain is a common symptom of neu- as neurotransmitters, drugs, and ions). ropathy, treatment often includes medications For further discussion of neuroreceptors within such as analgesics, tricyclic antidepressants, cer- the context of the structures and functions of the tain antiseizure medications, injected anesthetics nervous system, please see the overview section and corticosteroids, and topical anesthetics or “The Nervous System.” analgesics (lidocaine or capsaicin). Surgery may be See also ADDICTION; PARKINSON’S DISEASE. appropriate to relieve compression against a nerve or to sever the nerve when other treatments fail neurotransmitter A chemical that facilitates the to relieve incapacitating pain. Noninvasive passage of NERVE impulses among neurons. A neu- approaches to pain management that are some- rotransmitter may allow or block the travel of a times effective include BIOFEEDBACK and ACUPUNC- nerve impulse. Neurons store the chemical com- TURE. ponents of their neurotransmitters in microscopic structures called the synaptic vesicles, synthesizing the appropriate neurotransmitter when conduct- CONDITIONS THAT CAN CAUSE NEUROPATHY ing a nerve impulse. The sending NEURON’s axon chronic CIRRHOSIS CYTOMEGALOVIRUS (CMV) releases the neurotransmitter into the synapse DIABETES EPSTEIN-BARR VIRUS (space between neurons). The neurotransmitter GENETIC DISORDERS GUILLAIN-BARRÉ SYNDROME crosses the synapse to bind with the appropriate Hansen’s disease HEAVY-METAL POISONING NEURORECEPTOR on the dendrites of the receiving HIV/AIDS HYPOTHYROIDISM long-term ALCOHOLISM LYME DISEASE MULTIPLE SCLEROSIS NEUROFIBROMATOSIS NEUROTRANSMITTERS PERIPHERAL VASCULAR DISEASE (PVD)RAYNAUD’S SYNDROME acetylcholine aspartate RENAL FAILURE REPETITIVE motion INJURIES DOPAMINE EPINEPHRINE SCIATICA shingles gamma-aminobutyric acid (GABA) glutamate SYSTEMIC LUPUS ERYTHEMATOSUS (SLE) traumatic injury monoamine oxidase (MAO) NOREPINEPHRINE

VASCULITIS vitamin B12 deficiency serotonin 272 The Nervous System neuron. Hormones may also function as neuro- COMMON DISORDERS ASSOCIATED transmitters. WITH ORGANIC BRAIN SYNDROME

The appropriate balance of neurotransmitters is ALZHEIMER’S DISEASE DEMENTIA essential for neurologic function, as some neuro- ENCEPHALITIS HEART ATTACK transmitters are excitory (allow nerve impulses to hepatic NEUROPATHY HUNTINGTON’S DISEASE move from one neuron to another) and others are HYDROCEPHALY HYPOXIA inhibitory (block nerve impulses). Neurotransmit- long-term ALCOHOLISM MENINGITIS ters have specific functions. The BLOOD–BRAIN BAR- PARKINSON’S DISEASE SEPTICEMIA RIER allows the NERVOUS SYSTEM to maintain STROKE substance abuse different levels of neurotransmitters in the BRAIN TRANSIENT ISCHEMIC ATTACK (TIA) TRAUMATIC BRAIN INJURY (TBI) and in the body. Acetylcholine, for example, is essential in the brain for functions of cognition Symptoms and Diagnostic Path and memory. A diminished level of acetylcholine The presentation and severity of symptoms varies in the brain is among the hallmark characteristics with the underlying condition and other health of ALZHEIMER’S DISEASE. DOPAMINE is critical for factors. Symptoms extend over time and often movement; PARKINSON’S DISEASE develops when the worsen with time. Key symptoms include cells in the brain that produce dopamine die. Dopamine also facilitates nerve impulses that acti- • confusion, disorientation, and DELIRIUM vate the brain’s pleasure centers. Monoamine oxi- • difficulty carrying out tasks that require dase (MAO), serotonin, and NOREPINEPHRINE are thought, logic, and reasoning such as shopping key to mood. ANTIDEPRESSANT MEDICATIONS act by or traveling to and from home altering the balance of these three chemicals in • diminished ability to interact with others in the brain. In the body, acetylcholine conducts social settings electrical impulses between neurons and MUSCLE cells to facilitate movement. EPINEPHRINE and nor- • diminished ability to independently carry out epinephrine conduct electrical impulses in the activities of daily living such as bathing, dress- HEART. ing, and preparing meals For further discussion of neurotransmitters • lapses of memory, especially inability to within the context of the structures and functions remember recent events of the nervous system, please see the overview section, “The Nervous System.” The diagnostic path begins with a ROUTINE MED- See also AGING, NEUROLOGIC CHANGES THAT OCCUR ICAL EXAMINATION to assess health overall and a WITH; HORMONE. NEUROLOGIC EXAMINATION to evaluate brain function and cognitive abilities. Because symptoms can organic brain syndrome A collective term for result from electrolyte imbalance, HORMONE distur- disorders of cognition (thought and logic) and bances, high or low BLOOD GLUCOSE (sugar) levels, memory that arise from physical changes that take and other factors, the routine medical examina- place in the BRAIN. Numerous neurologic and tion typically includes a complete blood count metabolic disorders can cause organic brain syn- (CBC) and other blood tests. The doctor may also drome, as can head trauma and INFECTION, such as conduct a basic cardiovascular evaluation, includ- ENCEPHALITIS. Organic brain syndrome sometimes ing ELECTROCARDIOGRAM (ECG) and measurement of becomes an ambiguous diagnosis when there are BLOOD PRESSURE. A number of health conditions few distinct or apparent causes to explain mental that can cause cognitive disturbances become deterioration in people who are elderly. However, more common with advanced age, some of which the physical changes that occur in the brain to are easily treatable such as HYPOTHYROIDISM, HYPER- produce organic brain syndrome are more com- TENSION, ADRENAL INSUFFICIENCY, and cardiac mon in old age though are not inevitable aspects ARRHYTHMIA. The doctor may also conduct diagnos- of aging. tic imaging procedures such as COMPUTED TOMOGRA- organic brain syndrome 273

PHY (CT) SCAN or MAGNETIC RESONANCE IMAGING (MRI) Risk Factors and Preventive Measures to evaluate the brain and its blood flow. Organic brain syndrome is most common among people 70 years of age and older because many of Treatment Options and Outlook the conditions that produce the symptoms of Treatment targets the underlying condition when organic brain syndrome become more common appropriate and otherwise focuses on maintaining with advanced age. Mitigating the risk factors for QUALITY OF LIFE. Recent research shows that daily these conditions, which range from CARDIOVASCULAR physical activity such as walking may slow the pro- DISEASE (CVD) to DIABETES to chronic LIVER disease, gression of disorders such as ALZHEIMER’S DISEASE reduces the likelihood for developing cognitive and other degenerative disorders that produce impairments due to physical changes in the brain. organic brain syndrome symptoms. Adequate Lifestyle measures such as nutritious EATING HABITS, nutrition is also essential. Medications such as anti- daily physical activity, not smoking, and maintain- depressants and antipsychotics may help moderate ing healthy weight further contribute to neurologic behaviors and improve the person’s sense of well- as well as overall health. Activities that make use of being. Medications to treat Alzheimer’s disease, logic and reasoning, such as reading and crossword called acetylcholinesterase inhibitors, may improve puzzles, may help maintain mental acuity. cognitive ability or at least delay the progression of See also AGING, NEUROLOGIC CHANGES THAT OCCUR its decline. Because organic brain syndrome tends WITH; COGNITIVE FUNCTION AND DYSFUNCTION; END OF to be progressive, family members need to plan for LIFE CONCERNS; GENERATIONAL HEALTH-CARE PERSPEC- ongoing care and support. TIVES; MEMORY AND MEMORY IMPAIRMENT. P pallidotomy A surgical procedure in which the Most people return to full and regular activities neurosurgeon destroys a portion of the globus pal- within two weeks. lidus, a structure of the midbrain that participates The effects of pallidotomy are permanent, in regulating motor movement. Researchers in the though they do not affect the progression of the 1950s discovered that pallidotomy could signifi- Parkinson’s disease. As Parkinson’s disease pro- cantly reduce symptoms of PARKINSON’S DISEASE gresses, however, symptoms reemerge. Pallido- such as MUSCLE rigidity, DYSKINESIA, and gait freez- tomy is not very effective as treatment for other ing (akinesia). Until recent advances in technol- movement disorders. ogy, however, the risks of the surgery were greater See also DEEP BRAIN STIMULATION; SURGERY BENEFIT than the benefits. Current neurosurgery tech- AND RISK ASSESSMENT; TREMOR DISORDERS. niques use MAGNETIC RESONANCE IMAGING (MRI) to locate the globus pallidus and precisely guide the paralysis The loss of motor function as a result insertion and placement of a thin probe the neu- of damage (injury or disease) to the BRAIN or SPINAL rosurgeon uses to ablate (destroy) a few cells at a CORD. STROKE and trauma are the most common time until the OPERATION achieves the desired causes of paralysis. Paralysis may also occur with result. This minimizes the risk of damage to adja- INFECTION such as POLIOMYELITIS, complications of cent structures of the BRAIN. The person remains illness such as GUILLAIN-BARRÉ SYNDROME, and neu- conscious and responds with movements as the rologic disorders such as AMYOTROPHIC LATERAL SCLE- neurosurgeon directs. ROSIS (ALS) and BELL’S PALSY. Paralysis may affect The first step of the surgery is the placement of one side of the body (hemiplegia), the lower body a stereotactic halo, a circular brace attached to the (paraplegia), or the entire body (quadriplegia), skull (done under local anesthetic). The halo holds depending on the location of the damage. Some the instruments in precise position during the paralysis is temporary, with function returning operation. The second step of the surgery is the when the underlying condition resolves (such as ablation, or destruction of tissue in the globus pal- with Bell’s palsy and some kinds of BRAIN HEMOR- lidus. After injecting a local anesthetic to numb RHAGE). In other circumstances, such as when the SKIN and periosteum covering the cranium, the injury destroys NERVE tissue or structures, paralysis only areas that contain nerves sensitive to PAIN, is permanent. the neurosurgeon drills a tiny hole and inserts the probe, feeding it slowly to the globus pallidus with Symptoms and Diagnostic Path MRI visualization. The operation takes 45 to 90 The primary symptom of paralysis is loss of MUSCLE minutes, with improvement apparent immedi- function. In most cases, paralysis comes on ately. The neurosurgeon removes the stereotactic quickly. Some people also experience disturbance halo when the operation is finished. Complica- or loss of sensory perception, depending on the tions are rare; when they do occur they may cause of the damage. The diagnostic path gener- include excessive bleeding, postoperative ally begins with COMPUTED TOMOGRAPHY (CT) SCAN or INFECTION, and visual disturbances (the path to the MAGNETIC RESONANCE IMAGING (MRI) to identify any globus pallidus runs very near the optic tract). correctable or treatable cause for the paralysis and 274 Parkinson’s disease 275 to assess the extent of damage. Prompt interven- manent, to a NERVE or group of nerves. The “pins tion is essential for recovery from conditions such and needles” feeling in a hand or foot that “falls as brain hemorrhage, stroke, BRAIN TUMOR, and asleep” is a common experience of transient, or compression of the spinal cord. temporary, paresthesia that results from compres- sion of the nerves such as from the limb being Treatment Options and Outlook tucked under the body during sleep or when sit- When possible, treatment attempts to remove or ting for an extended period without moving. mitigate the source of the paralysis. Such efforts CARPAL TUNNEL SYNDROME and ROTATOR CUFF IMPINGE- might include surgery to remove a tumor or col- MENT SYNDROME are among the common conditions lected BLOOD (as in subdural HEMATOMA) or other that cause compression of the nerves through fluid that accumulates within the cranium (HYDRO- swelling and entrapment. CEPHALY). Rapid treatment can halt and even Pathologic paresthesia—parethesia arising from reverse the effects of stroke due to cerebral infarc- disease or injury—often occurs with PERIPHERAL tion (blood clot in the brain). Once paralysis VASCULAR DISEASE (PVD) or NEUROPATHY of DIABETES, becomes permanent, the emphasis of treatment conditions in which impaired BLOOD circulation shifts to maintaining optimal function of remain- causes damage to the PERIPHERAL NERVES of the ing motor abilities and learning methods of hands and feet. Deficiency of B vitamins, espe- accommodation. PHYSICAL THERAPY and OCCUPA- cially B12, and HEAVY-METAL POISONING (for example, TIONAL THERAPY are essential dimensions of such arsenic or mercury) affects the myelin sheathing treatment. Many people who have partial paraly- of nerves and commonly results in paresthesia. sis are able to return to independent living and Paresthesia is also a symptom of numerous neuro- often to their jobs and many of their favorite logic disorders and conditions and may occur in activities. Mobility aids such as wheelchairs, conjunction with NEURALGIA (PAIN along a nerve crutches, canes or walking sticks, walkers, and tract). Treatment for chronic or persistent pares- braces improve independence and QUALITY OF LIFE. thesia targets the underlying cause and may range from noninvasive methods such as BIOFEEDBACK Risk Factors and Preventive Measures and HYPNOSIS to therapeutic interventions such as The risk factors for paralysis are those of the medications or surgery. underlying causes of damage to the brain and See also BELL’S PALSY; MULTIPLE SCLEROSIS; SPINAL spinal cord. Traumatic injury is the most signifi- CORD INJURY; SYSTEMIC LUPUS ERYTHEMATOSUS (SLE). cant risk factor for people under age 30 years, par- ticularly young men. Conditions such as stroke, Parkinson’s disease A degenerative neuromus- neurologic disorders, and tumors become more cular disorder that results from the progressive common causes of paralysis among people age 50 loss of neurons within the structures of the mid- years and older. Preventive measures include seat brain, notably the substantia nigra, that produce belt use, protective headgear for activities such as DOPAMINE, a NEUROTRANSMITTER essential for MUSCLE bicycling and downhill skiing, and prudent judg- function. The loss of muscle function affects both ment when swimming and diving. Lifestyle voluntary (movement) and involuntary (swallow- choices such as nutritious EATING HABITS, not smok- ing, digestion, urination) activities. ing, and daily physical activity help reduce the risk for conditions such as stroke. Other causes of Symptoms and Diagnostic Path paralysis, such as CEREBRAL PALSY or ALS, are not Symptoms become apparent when the number of preventable. dopamine-producing cells drops to about 20 per- See also PARKINSON’S DISEASE; SPINA BIFIDA; SPINAL cent of normal and typically include CORD INJURY; TRAUMATIC BRAIN INJURY (TBI). • resting tremor usually affecting the fingers, paresthesia The sensation of tingling or burning hands, feet, and occasionally the MOUTH in a particular part or region of the body. Pares- • bradykinesia (slowed movement) thesia is a symptom of damage, temporary or per- • stiffness and rigidity of the muscles 276 The Nervous System

• shuffling, hunched posture when walking symptoms for a year or two with reprogramming (Parkinsonian gait) to adjust the intervals and intensity of the electri- • loss of balance, especially when changing direc- cal impulses. tion during walking Parkinson’s disease typically progresses over several decades. With early treatment many peo- Other symptoms develop as the condition pro- ple can remain symptom free for years. As the gresses and may include SIALORRHEA (excessive number of dopamine-producing cells in the brain drooling), HYPERHIDROSIS (excessive sweating), BLE- continues to decline, however, medications to PHAROSPASM, and difficulty speaking and swallow- treat Parkinson’s disease become less effective and ing. There is no definitive diagnostic test for eventually do not work at all. Though Parkinson’s Parkinson’s disease, so the diagnostic path consid- disease continues to progress, it is not fatal for ers both personal health history and clinical find- most people when the age of onset is 60 or later. ings. The neurologist may conduct imaging procedures such as COMPUTED TOMOGRAPHY (CT) Risk Factors and Preventive Measures SCAN and MAGNETIC RESONANCE IMAGING (MRI) to rule Researchers do not know what causes Parkinson’s out other causes of the symptoms, such as BRAIN disease, though it does appear to run in some fam- TUMOR or STROKE. ilies. The most significant risk factor for Parkin- son’s disease is advancing age, as neurologists Treatment Options and Outlook diagnose the condition most frequently in people Treatment targets the symptoms. Some medica- who are age 60 or older. Researchers believe most tions replace dopamine or function as dopamine early-onset Parkinson’s disease, which often agonists to activate dopamine receptors. The begins in the 30s or 40s, is genetic. There are no antiviral medication amantadine improves symp- measures known to prevent Parkinson’s disease. toms in some people. Response to medications is See also AGING, NEUROLOGIC CHANGES THAT OCCUR highly individual. The neurologist chooses med- WITH; ALZHEIMER’S DISEASE; DEMENTIA; HUNTINGTON’S ication combinations according to the person’s DISEASE; PALLIDOTOMY; THALAMOTOMY; TREMOR DISOR- age, general health status, apparent rate of pro- DERS. gression, and other factors. Most people take com- binations of medications to address different peripheral nerves The nerves that branch from aspects of the condition and to offset the side the CENTRAL NERVOUS SYSTEM to serve the body. The effects of some medications. The person eventu- primary peripheral nerves are the CRANIAL NERVES ally becomes resistant to levodopa, a dopamine and the SPINAL NERVES, which branch into smaller precursor that currently is the only dopamine- and numerous nerves that extend to all parts of replacement DRUG available. A person who has the body. The peripheral nerves may be visible to Parkinson’s disease can typically take levodopa for the unaided EYE, as are the cranial nerves and the five to seven years. spinal nerves, or microscopic, as are the tiny The US Food and Drug Administration (FDA) nerves that serve areas such as the fingertips. Sen- recently approved the surgical treatment DEEP sory nerves carry signals to the BRAIN and motor BRAIN STIMULATION (DBS) as a treatment for Parkin- nerves carry signals to the body. Some nerves son’s disease that no longer responds to medica- have both functions. tions. In DBS, the neurosurgeon implants an For further discussion of the peripheral nerves electrode deep into the BRAIN near the thalamus (a within the context of the structures and functions structure with an integral role in movement and of the nervous system, please see the overview motor function). The electrodes connect to a pulse section “The Nervous System.” generator, similar in concept to a HEART PACEMAKER, See also SPINAL CORD. implanted in a small pocket of tissue. The neurol- ogist programs the pulse generator to deliver regu- peripheral nervous system The CRANIAL NERVES, lar electrical impulses that subdue dyskinesias, SPINAL NERVES, and their extensions. The peripheral rigidity, and tremors. DBS can provide relief from nervous system has two major subdivisions: the poliomyelitis 277 somatic NERVOUS SYSTEM and the autonomic nerv- See also COMA; CONSCIOUSNESS; END OF LIFE CON- ous system. The nerves of the somatic nervous CERNS; QUALITY OF LIFE. system are both sensory (conduct signals from the body to the BRAIN) and motor (carry signals from poliomyelitis A contagious viral INFECTION, often the brain to the structures of the body that are called simply polio, that affects the nerves and under voluntary control). The nerves of the auto- motor function throughout the body. Poliomyelitis nomic nervous system regulate involuntary func- is rare today in the United States and other devel- tions such as HEART RATE and digestion as well as oped countries as a result of aggressive vaccination the endocrine and exocrine glands. The auto- programs. The first injectable VACCINE to prevent nomic nervous system has two further subdivi- poliomyelitis became available in 1955; a more sions: the sympathetic nerves (which serve the effective oral vaccine (modified live VIRUS) became thorax and lumbar region) and parasympathetic available in 1963. The last known “wild” nerves (which serve the head and sacral region. poliomyelitis infection occurred in the United For further discussion of the peripheral nervous States in 1979. Subsequent poliomyelitis illness system within the context of the structures and resulted from infections acquired in other coun- functions of the nervous system as a whole, please tries or from exposure of the nonvaccinated to the see the overview section “The Nervous System.” oral vaccine. The switch to an enhanced inactive See also CENTRAL NERVOUS SYSTEM; ENDOCRINE (killed) poliovirus vaccine (IPV), capable of pro- GLAND; PERIPHERAL NERVES. viding lifelong immunity, in 1987 eliminated the latter as a cause of poliomyelitis. Oral poliovirus persistent vegetative state An extended state of vaccine is no longer available in the United States. unconsciousness in which higher BRAIN activity Three strains of poliovirus can cause infection. The (cerebral cortex function) is negligible or lost complete vaccination series consists of four doses though the brainstem continues to operate to sus- of vaccine, one for each strain and a final booster. tain the vital functions of living such as breathing, HEART RATE, and BLOOD PRESSURE. Basic motor func- Adults who travel to parts of the world tion, such as spontaneous though undirected where poliomyelitis remains endemic movement, may also occur as the brainstem is (notably Africa and Southeast Asia) responsible for some motor functions. The person should receive either the complete inac- may also make sounds, move the eyes, and move tive poliovirus vaccine (IPV) series, if the MOUTH. However, there is no recognition of or never vaccinated or previous vaccina- purpose to these actions, and the person cannot tion status is unknown, or an IPV follow instructions to move in certain ways and booster otherwise. does not speak, drink, or eat. A person may remain in a persistent vegetative Most poliomyelitis is either subclinical (no state for months, years, or decades with adequate symptoms) or nonparalytic (runs a course of ill- nutritional support. Though in general the longer a ness with symptoms similar to those of INFLUENZA). person remains in a persistent vegetative state the Paralytic poliomyelitis, which affects the BRAIN and less likely he or she will recover conscious function, SPINAL CORD, occurs in about 2 percent of infec- occasionally individuals emerge after extended tions. Among those who develop paralytic periods. The likelihood of recovery depends on the poliomyelitis, the risk for death due to PARALYSIS of extent and nature of damage to the cerebral cortex, the muscles of BREATHING and residual paralysis which imaging procedures such as MAGNETIC RESO- after recovery from the infection are high. More NANCE IMAGING (MRI) and COMPUTED TOMOGRAPHY (CT) than 90 percent of people who develop nonpara- SCAN can help assess. Persistent vegetative state lytic poliomyelitis, which affects PERIPHERAL NERVES, raises many medical, legal, and ethical concerns for recover without complications. health-care providers as well as family members in In the late 1970s health experts began tracking regard to how long to sustain life through support- the emergence of some polio-like symptoms, such ive measures. as MUSCLE weakness and generalized fatigue, in 278 The Nervous System people who had recovered from childhood • muscle PAIN and cramping throughout the body poliomyelitis. Though researchers do not fully • extreme irritability understand what causes postpolio syndrome, it appears to result from damage the poliovirus The diagnostic path begins with a PERSONAL caused to motor neurons during the active infec- HEALTH HISTORY to determine the likelihood and cir- tion rather than a recurrent or new poliomyelitis cumstances of exposure to the poliovirus. The infection. About one in four people who recover presence of poliovirus in CEREBROSPINAL FLUID from paralytic poliomyelitis develops postpolio obtained via LUMBAR PUNCTURE confirms the diag- syndrome 10 to 40 years later. nosis.

Symptoms and Diagnostic Path Treatment Options and Outlook Subclinical poliomyelitis is a very mild infection Treatment is supportive while the infection runs that does not cause symptoms. The symptoms of its course, which is typically two to three weeks. nonparalytic poliomyelitis are similar to those of Such support may include medications to relieve influenza and include muscle SPASM and pain, improve gastrointestinal and urinary function, and treat secondary bacter- • NAUSEA, VOMITING, and DIARRHEA ial infections (commonly affecting the urinary • moderate FEVER tract and the upper respiratory tract). Paralysis that affects breathing may require MECHANICAL VEN- • muscle aches and weakness TILATION. • extreme fatigue Most people who survive the course of the dis- • irritability ease recover, though many have residual complica- • muscle aches in the lower back and calves tions such as partial paralysis or muscle deformities that result from the extensive damage to motor • painful SKIN RASH neurons. When damage is high in the spinal cord, The course of nonparalytic illness runs about the person may experience continued difficulty two weeks, during which symptoms gradually breathing or relatively complete paralysis. subside. The symptoms of paralytic poliomyelitis Risk Factors and Preventive Measures are far more severe and are similar to those of Vaccination prevents infection with the poliovirus; MENINGITIS or ENCEPHALITIS. They include poliomyelitis occurs only in people who have not • moderate to high fever received proper vaccination or who received vac- cination in childhood and travel in later adulthood • stiffness and pain in the neck and upper back to parts of the world where poliomyelitis remains • HEADACHE endemic (notably Africa and Southeast Asia). • rapid onset of muscle weakness that may See also INCUBATION PERIOD; PREVENTIVE HEALTH progress to paralysis within hours CARE AND IMMUNIZATIONS. R reflex An involuntary response to a stimulus is most problematic at night because it interferes that produces a limited and predictable action. with sleep. Neurologists do not know what causes Some reflexes are present only in early infancy restless legs syndrome, though many believe it is a and are survival-related, such as the rooting movement disorder arising from dysfunction of reflex, which guides an infant to locate the nipple the structures in the midbrain that regulate motor for BREASTFEEDING, or the startle (Moro) reflex, in function. Many people receive relief when taking which an infant makes a grasping motion with the medications used to treat PARKINSON’S DISEASE such arms and legs in response to stimulation that sug- as DOPAMINE agonists and levodopa, suggesting dis- gests falling. Other reflexes that represent normal turbances of neurotransmitters such as dopamine neurologic function in infancy may reappear later and acetylcholine create subtle disruptions of in life as signs of neurologic damage, such as motor response. Restless legs syndrome is also Babinski’s reflex (a spreading of the toes with firm common in people who have Parkinson’s disease. stimulation of the sole of the foot). Reflexes that The diagnostic path incorporates a comprehen- remain throughout life generally protect the body sive NEUROLOGIC EXAMINATION primarily to rule out in some way, such as the gag reflex (which helps other potential causes for the symptoms. The neu- prevent large objects from entering the throat) rologist may conduct electromyogram (EMG) and the corneal reflex (in which contact with the studies of the muscles in the legs to evaluate their CORNEA causes the eyelid to close). The SPINAL CORD responses to NERVE impulses. Sleep studies often manages most reflexes. reveal the extent to which the symptoms interfere A reflex represents a complete circuit of stimu- with sleep. Treatment may include a combination lus, sensory NERVE function, spinal cord (and of medications, such as dopamine agonists, MUSCLE sometimes BRAIN) participation, and motor nerve relaxants, sleep aids, and ANALGESIC MEDICATIONS for function. Neurologists call this circuit a reflex arc. pain relief. Some people experience relief from Abnormal reflex responses indicate interruption of symptoms and improved sleep with alternative the arc and damage to the neurologic structures. A therapies such as ACUPUNCTURE and BIOFEEDBACK. number of reflexes become abnormal when there Restless legs syndrome affects 12 to 20 million is TRAUMATIC BRAIN INJURY (TBI) or SPINAL CORD Americans. Many people who have restless legs INJURY, for example, or in neurologic disorders that syndrome do not seek medical care because they damage brain and nerve tissue such as PARKINSON’S do not know there are treatments available to ease DISEASE and MULTIPLE SCLEROSIS. their symptoms. Restless legs syndrome is chronic, See also NEUROLOGIC EXAMINATION. often developing in midlife or later. There are no known measures to prevent restless legs syn- restless legs syndrome A chronic disturbance of drome. the PERIPHERAL NERVES in the legs that causes symp- See also APNEA; NEUROTRANSMITTER; SLEEP DISOR- toms of burning, irritation, itching, crawling sen- DERS. sations, and often PAIN. Accompanying these discomforts is the urge to move the legs, which Reye’s syndrome A rare complication of certain diminishes the symptoms. Restless legs syndrome viral infections in children, notably CHICKENPOX, 279 280 The Nervous System upper respiratory INFECTION, and INFLUENZA (the constellation of metabolic disturbances that typify flu). Researchers do not know what causes Reye’s the syndrome. These metabolic disturbances often syndrome to develop though it is significantly cause serious complications such as ARRHYTHMIA more likely to occur in children who receive (abnormal electrical activity in the heart) and aspirin or bismuth subsalicylate (Pepto Bismol) to HYPOTENSION (low BLOOD PRESSURE). Kidney function treat the symptoms of their viral infections. also may suffer, leading to RENAL FAILURE. Overall about 75 percent of children survive There is a strong correlation between Reye’s syndrome; about two thirds of survivors aspirin and other salicylates (such as have no long-term consequences. When such bismuth subsalicylate, better known as consequences occur, they may include SEIZURE DIS- the trade product Pepto Bismol) and ORDERS, intellectual impairment, and neuromuscu- Reye’s syndrome in children. Do not lar dysfunction. The later the stage of Reye’s give these products to children who syndrome at the time of diagnosis, the higher the may have viral infections. risk for complications, including death.

Though Reye’s syndrome affects multiple organ Risk Factors and Preventive Measures systems, the most serious consequence (and usu- Reye’s syndrome occurs nearly exclusively in chil- ally the first indication of the syndrome’s appear- dren under age 15 years and develops during the ance) is ENCEPHALOPATHY (disturbances of BRAIN course of a viral infection. IMMUNIZATION for function). Early diagnosis and aggressive thera- influenza and chickenpox can prevent these infec- peutic intervention are essential to prevent or tions, which are commonly associated with Reye’s manage metabolic and neurologic complications. syndrome. There are no known measures for pre- Reye’s syndrome can be fatal. venting Reye’s syndrome. Early diagnosis and aggressive treatment are essential for optimal Symptoms and Diagnostic Path recovery. The first symptoms of Reye’s syndrome are those See also CHILDHOOD DISEASES. of encephalopathy developing within a week of a viral infection. These symptoms include rhizotomy A surgical OPERATION to selectively sever segments (rootlets) of the dorsal (back) or • confusion ventral (front) roots of a spinal NERVE to treat • memory disturbances intractable and debilitating PAIN or spasticity such • agitation as may occur with neuromuscular disorders. The operation reduces the number of nerve impulses • progressive UNCONSCIOUSNESS the nerve roots convey. Rhizotomy may be an Reye’s syndrome causes excessive deposits of appropriate treatment for CEREBRAL PALSY, SPINAL fatty acids in the LIVER; thus liver biopsy provides CORD INJURY, and other conditions that generate the definitive diagnosis. The deposits interfere DYSTONIA, CHOREA, or ATHETOSIS. Rhizotomy gener- with the liver’s ability to function, resulting in sys- ally becomes a therapeutic option only when temic metabolic disturbances, such as electrolyte other methods have failed to control symptoms, and enzyme imbalances, that are apparent from though may be an earlier recommendation for BLOOD tests. Deposits of fatty acids may accumulate certain presentations of spastic cerebral palsy. The in other organs as well, such as the HEART, KIDNEYS, neurosurgeon performs the operation with the and PANCREAS. person under general ANESTHESIA. Risks and com- plications of rhizotomy include excessive bleeding, Treatment Options and Outlook postoperative INFECTION, altered sensory perception A child who has Reye’s syndrome requires hospi- in the affected limb (usually foot or leg), and, talization in the intensive care unit. Because the rarely, PARALYSIS. cause of Reye’s syndrome remains unknown, See also BOTULINUM THERAPY; SURGERY BENEFIT AND treatment is supportive and aims to manage the RISK ASSESSMENT. S

seizure disorders Abnormal discharge of electri- CEPHALOGRAM (EEG), and diagnostic imaging proce- cal activity in certain areas of the BRAIN that causes dures such as COMPUTED TOMOGRAPHY (CT) SCAN or various involuntary consequences. Most seizures MAGNETIC RESONANCE IMAGING (MRI). The EEG typi- originate in areas of the cerebral cortex. cally shows irregularities in electrical activity even Seizure disorders may occur spontaneously when the person is not having seizures. Because (without identifiable cause) or as a consequence sleep deprivation makes the brain more sensitive of damage to the brain such as TRAUMATIC BRAIN to electrical activity, the neurologist may request INJURY (TBI) or CEREBRAL PALSY. Among the more the person remain awake for 24 hours before the common forms of seizure disorders are EEG. These procedures are generally conclusive for diagnosing seizure disorders. • epilepsy, in which seizures are recurrent and often frequent Treatment Options and Outlook • absence seizures, in which the person experi- Antiseizure medications are the mainstay of treat- ences very brief episodes of loss of conscious- ment for seizure disorders. Often a person may ness though often is unaware they occur require two or more medications that have differ- ent actions to adequately suppress inappropriate • clonic–tonic seizures, in which the person loses electrical activity in the brain and prevent seizures consciousness and there is convulsive move- from occurring. Because antiseizure medications ment of the legs and arms alter the brain’s biochemistry and have potentially • focal seizures, in which the person may or may serious side effects, neurologists tend not to treat a not lose consciousness and the seizure affects a single episode of seizure but opt instead to take an specific and localized part of the body approach of watchful waiting.

Seizures generally end within a minute and do MEDICATIONS TO TREAT SEIZURE DISORDERS not themselves harm injuries may occur if a per- carbamazepine (Tegretol) gabapentin (Neurontin) son falls or has a seizure in a hazardous location lamotrigine (Lamictal) levetiracetam (Keppra) such as a swimming pool. There is no reason to oxcarbazepine (Trileptal) phenobarbital intervene with a person who is having a seizure, phenytoin (Dilantin) tiagabine (Gabitril) other than for safety. Some people, especially chil- topiramate (Topamax) valproic acid (Depakote) dren, may have seizures during FEVER. Such zonisamide (Zonegran) seizures, called febrile seizures, do not indicate the person has a seizure disorder. Treatment is generally long-term, though chil- dren may outgrow certain kinds of seizure disor- Symptoms and Diagnostic Path ders. Medications successfully prevent seizures in Seizure disorders run the gamut from causing most people, though require regular monitoring to barely noticeable to disabling symptoms. The diag- ensure that BLOOD concentrations remain thera- nostic path includes a thorough PERSONAL HEALTH peutic. Dysfunctions of the LIVER and KIDNEYS are HISTORY, NEUROLOGIC EXAMINATION, ELECTROEN- the most significant side effects of antiseizure 281 282 The Nervous System medications. Surgery to interrupt electrical activity Meningocele and myelomeningocele are rare. in the brain is sometimes an option for intractable Myelomeningocele can be life threatening, seizures (seizures that fail to respond to medica- depending on its location and the extent of expo- tion therapy). sure of the spinal cord, which presents a signifi- Risk Factors and Preventive Measures cant risk for INFECTION (MENINGITIS or ENCEPHALITIS). Neurologists do not know the cause of most Symptoms and Diagnostic Path seizure disorders; thus there are no measures known to prevent them from developing. People Diagnostic prenatal ULTRASOUND detects many neu- who have recurrent seizures or do not experience ral tube defects before birth. At birth, symptoms of full suppression of seizures with treatment should meningocele and myelomeningocele are apparent not drive or engage in other activities that can put as deformities of the spine. COMPUTED TOMOGRAPHY them or others at risk. Many states have laws that (CT) SCAN or MAGNETIC RESONANCE IMAGING (MRI) help regulate the conditions under which a person who the neurosurgeon assess the extent of the damage has a seizure disorder may obtain a driver’s and plan an appropriate course of treatment. license; such laws vary among states. Treatment Options and Outlook See also MYOCLONUS. Spina bifida occulta requires no treatment. spina bifida A form of neural tube defect in Surgery is necessary to repair meningocele, though which the distal (lower) portion of the neural tube nearly always recovery is complete. Meningocele fails to close early in embryonic development. In repair often heals with minimal or no residual con- very mild spina bifida the defect may be unappar- sequences, and the child grows up with normal ent and cause no problems. Severe spina bifida neurologic function. Complex surgery often is nec- essary to repair myelomeningocele, and residual leaves the SPINAL CORD partially or completely exposed, resulting in numerous complications that complications are usually extensive. Ongoing com- plications include paralysis, deformity, and HYDRO- often include deformity and PARALYSIS. Doctors identify three forms of spina bifida: CEPHALY (excessive CEREBROSPINAL FLUID) that requires a shunt. Children born with myelo- • Spina bifida occulta is the most common and meningocele require lifetime medical and support- the mildest form. Only a small portion of a sin- ive care. Many have permanent URINARY gle vertebra fails to close properly. The spinal INCONTINENCE and FECAL INCONTINENCE because the cord and the SPINAL NERVES develop correctly. lower spinal cord, which is nonfunctional, regu- The surface of the spine looks and feels normal, lates urination and defecation. Some may learn to and the person has no symptoms. walk with crutches or braces. Developmental delays and LEARNING DISORDERS are common. • Meningocele is when the meninges (mem- branes that enclose the spinal cord) protrude Risk Factors and Preventive Measures under the surface of the SKIN through the Folic acid supplementation greatly reduces the risk incompletely closed vertebrae (usually two or for neural tube defects such as spina bifida, per- more). The spinal cord and spinal nerves haps by 70 percent. Health experts recommend develop correctly, however. that all women of childbearing ability and age take • Myelomeningocele is the most severe form. daily folic acid supplement regardless of their The spinal canal is open and exposed along the pregnancy plans, as the most important period of lower spine. The spinal cord and meninges typ- supplementation appears to be the four to six ically appear as a saclike structure, which may weeks before CONCEPTION through the first be under or on top of the skin. The spinal cord trimester of pregnancy. Some antiseizure medica- and spinal nerves do not develop correctly, and tions (notably valproic acid), DIABETES, and OBESITY often there are deformities of the pelvis, increase the risk for neural tube defects. Though abdominal and pelvic organs, and lower limbs. most spina bifida seems to occur spontaneously, spinal cord injury 283 women who have had one child with spina bifida spinal cord injury Traumatic damage to the are more likely to have others. Researchers are SPINAL CORD, usually the result of a blow to the not certain whether the connection is genetic or spine or sudden, forceful twisting. MOTOR VEHICLE environmental. ACCIDENTS account for 40 percent and VIOLENCE See also BIRTH DEFECTS; NEURAL TUBE DEFECTS; PRE- (gunshot and knife wounds) accounts for 25 per- NATAL CARE. cent of spinal cord injuries in the United States. Other common causes are diving into shallow spinal cord The largest NERVE in the body, water, sports-related injuries, and significant falls. extending from the base of the BRAIN (medulla More than 80 percent of those who experience oblongata) through the spinal canal to the second spinal cord injuries are men, more than half of lumbar vertebra. The average adult spinal cord is whom are under age 30. 16 to 20 inches long and about the thickness of a man’s thumb. The outer structure of the spinal SPINAL CORD injury is a medical emer- cord is white matter (myelinated neuronal axons); gency that requires immediate treat- the inner structure is gray matter (NEURON cell ment at a neurologic trauma center. It is bodies). The inner gray matter is roughly the critical that only properly trained med- shape of an H, with the horns extending to the ical personnel attempt to move some- roots of the 31 pairs of SPINAL NERVES that branch one who may have suffered a spinal from the spinal cord. cord injury. The spinal cord is the primary neurologic con- duit between the body and the brain. It transmits Such injuries typically cause the vertebrae to motor nerve impulses from the brain to the body compress the spinal cord, damaging the long and sensory nerve impulses from the body to the axons that make up the spinal cord’s white matter. brain. The spinal cord also has rudimentary filter- The axons are the fibers that extend from neurons ing and control functions, responding to certain in the BRAIN and brainstem. This type of injury, kinds of nerve impulses, and serves as the center which neurologists classify as incomplete, permits for reflexes related to urination, defecation, and some NERVE impulses to travel the spinal cord and MUSCLE stretch (essential for movement and bal- is sometimes recoverable. Much less commonly, ance). trauma partially or completely severs the spinal The spinal column, a sequence of joined verte- cord. A complete spinal cord injury exists when brae, encloses and protects the spinal cord. CARTI- no nerve impulses can travel through or around LAGE cushions between each vertebra (vertebral the point of trauma. Circumstances that increase disks) allow the spine to flex and twist without the damage include bleeding, which can increase jeopardizing the spinal cord. Significant trauma, pressure and/or directly damage neurons, and a such as may occur in an automobile accident, can surge of neurotransmitters, notably glutamate, at compress, bruise, or sever the spinal cord. Such the site of the injury, which overwhelms and kills injuries cause paralysis. A severed spinal cord can- neurons. not regenerate, though sometimes partial to full function returns with release of the source of Symptoms and Diagnostic Path compression or after HEALING of a bruise. Tumors The primary symptom of spinal cord injury is may also compress the spinal cord. immediate PARALYSIS below the point of trauma. For further discussion of the spinal cord within When the injury is high on the spinal cord, above the context of the structures and functions of the the lumbar vertebrae, the paralysis may affect the nervous system, please see the overview section DIAPHRAGM and muscles of the chest, preventing “The Nervous System.” the mechanics of BREATHING from taking place. See also HERNIATED NUCLEUS PULPOSUS; MOTOR Injury at the cervical level is most severe; injury at VEHICLE ACCIDENTS; NEUROFIBROMATOSIS; REFLEX; the C1 or C2 level is usually not survivable SPINAL CORD INJURY. because this is the level of neurologic functions 284 The Nervous System that support survival such as respiration, BLOOD spinal nerves The 31 paired nerves that branch PRESSURE, and HEART RATE. COMPUTED TOMOGRAPHY from the SPINAL CORD, extending into the body to (CT) SCAN or MAGNETIC RESONANCE IMAGING (MRI) can form the PERIPHERAL NERVES. The spinal nerves and show the full extent of the injury. the CRANIAL NERVES together make up the PERIPH- ERAL NERVOUS SYSTEM. The spinal nerves emerge Treatment Options and Outlook from the gray matter of the spinal cord in two The standard of care is to administer an intra- roots. The ventral (anterior or front) spinal NERVE venous corticosteroid medication, methylpred- root is the motor portion of the spinal nerve that nisolone, within eight hours of a spinal cord. The carries nerve impulses from the BRAIN and spinal methylprednisolone reduces the body’s natural cord to the peripheral body. The dorsal (posterior inflammatory response, lessening the risk for or back) spinal nerve root is the sensory portion of added pressure within the spinal canal and the the spinal nerve that carries nerve impulses from direct damage to neurons that INFLAMMATION the body to the spinal cord and brain. Each spinal causes. Other treatment options may include sur- nerve root immediately branches into several gery to stabilize the spine and remove any BONE rootlets, which subsequently give rise to the fragments or debris from the spinal canal or using peripheral nerves that serve the body (excluding braces to immobilize the spine. Supportive meas- the head and face). ures such as MECHANICAL VENTILATION may be neces- sary, depending on the level of the injury. SPINAL NERVE PAIRS Ongoing treatment typically includes early and cervical: 8 pairs, designated C1 through C8 aggressive PHYSICAL THERAPY, OCCUPATIONAL THERAPY, thoracic: 12 pairs, designated T1 through T12 and other rehabilitation approaches to maintain lumbar: 5 pairs, designated L1 through L5 MUSCLE tone and STRENGTH as well as to restore as sacral: 5 pairs, designated S1 through S5 much independence as possible. Much of this coccygeal: 1 pair, designated CO1 treatment may take place at an inpatient rehabili- tation center that specializes in spinal cord Spinal nerve pairs C1 through C4 serve the neck injuries. Many people are able to recover to a rea- and are collectively referred to as the cervical sonable level of function through the use of plexus. Spinal nerve pairs C5 through T1 serve the mobility aids and assistive devices. When the upper extremities and main trunk and are collec- injury is incomplete, full recovery is sometimes tively known as the thoracic plexus. Spinal nerve possible. However, it is difficult for neurologists to pairs L1 through L5 (the dorsal roots of L4 and L5) predict what level of recovery is likely. An individ- serve the lower back and legs and are collectively ual’s general health condition, motivation, and referred to as the lumbar plexus. Spinal nerve pairs persistence are important influences. L4 (the ventral roots of L4 and L5) through S3 serve the structures of the lower abdomen and are Risk Factors and Preventive Measures collectively known as the sacral plexus. Spinal Measures that reduce the risks for spinal cord nerve pairs S4, S5, and CO1 serve the structures of injury are those that lower the likelihood of motor the pelvis, including the genitals, and are collec- vehicle accidents. Many of these risks are behav- tively known as the pudendal plexus. iors such as excessive speed, driving while intoxi- For further discussion of the spinal nerves cated, and failure to wear seat belts. Proper within the context of the structures and functions technique and equipment for athletic activities of the nervous system, please see the overview such as horseback riding, downhill skiing, bicy- section “The Nervous System.” cling, and contact sports help improve the safety See also MULTIPLE SCLEROSIS; SPINA BIFIDA; SPINAL of participating in these events. CORD INJURY. See also CORTICOSTEROID MEDICATIONS; NEURON; NEUROTRANSMITTER; QUALITY OF LIFE; TRAUMATIC BRAIN stupor A state in which a person is unaware of INJURY (TBI). and does not interact with the external environ- stupor 285 ment except when vigorously stimulated to brief CUSSION), ENCEPHALOPATHY, seizures, DRUG overdose, arousal. Stupor is very near COMA on the scale of and poisoning. Because some causes of stupor are CONSCIOUSNESS. Stupor may result from numerous potentially lethal, doctors attempt to identify them circumstances, including HYPOGLYCEMIA (low BLOOD quickly. Treatment depends on underlying cause. GLUCOSE level), INTOXICATION, HYPOXIA (lack of oxy- See also PERSISTENT VEGETATIVE STATE; SEIZURE DIS- gen), injury (TRAUMATIC BRAIN INJURY [TBI] or CON- ORDERS; UNCONSCIOUSNESS. T–U

tardive dyskinesia See DYSKINESIA. the stereotactic halo when the operation is com- pleted. Complications are rare; when they do thalamotomy A surgical procedure in which the occur they may include excessive bleeding, post- neurosurgeon destroys a small portion of the THAL- operative INFECTION, and stimulation of taste or AMUS, which plays a role in certain kinds of motor visual disturbances (due to the probe passing near movement. Thalamotomy may be an appropriate or through these areas of the brain). Most people treatment for tremor-predominant PARKINSON’S return to full and regular activities in about two DISEASE, tremor disorders such as benign essential weeks. tremor, and DYSTONIA. Neurosurgeons first per- The effects of thalamotomy are permanent and formed thalamotomy in the 1950s. Until recent may end symptoms for some people, especially advances in technology, however, the risks of the those who have benign essential tremor. Symp- surgery (especially damage to adjacent BRAIN struc- toms often reemerge when the underlying condi- tures) were far greater than the benefits. Current tion is progressive. However, thalamotomy is not neurosurgery techniques use MAGNETIC RESONANCE very effective treatment for the DYSKINESIA of clas- IMAGING (MRI) to locate the portions of the thala- sic Parkinson’s disease. mus that participate in movement, typically the See also DEEP BRAIN STIMULATION; PALLIDOTOMY; ventral intermediate (VIM) nucleus. The neuro- SURGERY BENEFIT AND RISK ASSESSMENT. surgeon then uses MRI to precisely guide the insertion and placement of a thin probe into the tic An involuntary MUSCLE SPASM that typically VIM. A burst of heat through the electrode occurs repetitiously and spontaneously. Tics most ablates, or destroys, a few cells at a time until the commonly involve muscle groups in the face and OPERATION achieves the desired result. The person neck and may appear purposeful, such as an eye- remains conscious during the operation and lid tic that gives the appearance of winking or a tic responds with movements as the neurosurgeon involving the muscles around the MOUTH that directs. causes a person to look as though he or she were The first step of thalamotomy is the placement grimacing. Vocal tics are spasms that involve the of a stereotactic halo, a circular brace the neuro- VOCAL CORDS and produce noises such as grunts. surgeon attaches to the skull (done under local Tics are very common, especially in childhood, anesthetic). The halo holds the instruments steady and in isolation usually have no neurologic signifi- and in precise position during the operation. The cance. Some people experience tics during times neurosurgeon uses a local anesthetic to numb the of anxiety. Tics that persist or occur in conjunction SKIN and periosteum covering the cranium, the with other symptoms may indicate a compressed only areas that contain nerves sensitive to PAIN, NERVE or an underlying neurologic or neuromus- and drills a small hole in the BONE. The neurosur- cular condition. Tic disorders that reflect neuro- geon slowly feeds the probe toward the thalamus, logic disturbances include TOURETTE’S SYNDROME using MRI to guide the process. The operation and tic douloureux (more commonly called takes 60 to 90 minutes, and improvement is trigeminal NEURALGIA). apparent immediately. The neurosurgeon removes See also CEREBRAL PALSY; DYSKINESIA. 286 traumatic brain injury (TBI) 287

Tourette’s syndrome A neurologic disorder in Tourette’s syndrome does not result from signifi- which a person experiences an array of tics (invol- cant neurologic damage and does not threaten untary and repetitive movements). Researchers health or well-being. SUPPORT GROUPS and thera- believe Tourette’s syndrome results from subtle pists can help people develop COPING MECHANISMS imbalances of neurotransmitters in the BRAIN. The for living with Tourette’s syndrome. Because stress imbalances cause disturbances of motor function and anxiety exacerbate symptoms, people who that affect the muscles of movement as well as have Tourette’s syndrome generally benefit from functions of articulation and vocalization. Most stress reduction methods and approaches such as people who have Tourette’s syndrome experience BIOFEEDBACK. simple neuromuscular tics such as involuntary See also ATTENTION DEFICIT HYPERACTIVITY DISORDER movements of the eyelids or MOUTH, or even the (ADHD); NEUROTRANSMITTER; OBSESSIVE–COMPULSIVE head and extremities. Some people also experi- DISORDER (OCD); STRESS AND STRESS MANAGEMENT; TIC. ence vocal tics, in which they express noises such as grunts and coughs. And some people experi- traumatic brain injury (TBI) Damage, often per- ence articulation tics in which they speak words, manent, to the BRAIN that results from trauma, sometimes obscenities, involuntarily and often blunt or open. TBI may be acute (occur suddenly) loudly, as though the words erupted from them. or chronic (occur over time as a result of cumula- Although these tics have the appearance of con- tive injuries). Acute TBI most often occurs from a scious behavior (and some people can temporarily blow to the head, such as from a significant fall or suppress them through conscious effort), they are collision. Open trauma to the head, such as gun- involuntary neurologic disturbances. shot wound, may also result in acute TBI. Chronic There are no clear diagnostic markers for TBI develops in people who receive repeated Tourette’s syndrome. Symptoms typically begin in blows to the head, such as athletes who partici- childhood, around age seven or eight, and peak pate in contact or collision sports. Boxing, soccer, during ADOLESCENCE before trailing off. Many peo- and American football are the leading causes of ple who have Tourette’s syndrome have few chronic TBI in the United States. The effects of TBI episodes of tics after they reach midlife, though may range from mild disturbances of thought or neurologists consider Tourette’s syndrome a movement to incapacitating loss of cognitive and chronic, lifelong condition. When evaluating the motor function or PERSISTENT VEGETATIVE STATE. symptoms of Tourette’s syndrome, the neurologist may conduct numerous tests and procedures to Shaken baby syndrome, a form of CHILD rule out other potential causes, including psychi- ABUSE, is a significant and preventable atric illness, of the symptoms. The neurologist will cause of TRAUMATIC BRAIN INJURY (TBI)in generally make the diagnosis of Tourette’s syn- young children. Children are especially drome after ruling out such possibilities and when vulnerable to brain injury and may symptoms persist for a year or longer. experience permanent damage or die Many people who have Tourette’s syndrome from events that would not harm an respond to combinations of medications including adult. ANTIPSYCHOTIC MEDICATIONS, ANTIDEPRESSANT MEDICA- TIONS, STIMULANTS, and the BLOOD PRESSURE medica- Symptoms and Diagnostic Path tion clonidine (Catapres). All of these medications Symptoms of TBI may be vague and mild or sud- have varied effects on neurotransmitters and the den and severe. Common symptoms include brain’s biochemical balance. Though it may take a period of trial and error to find the combination • significant or persistent HEADACHE that is most effective for each individual, nearly • loss of CONSCIOUSNESS everyone who has Tourette’s syndrome experi- • unequal dilation of the pupils ences diminished symptoms with appropriate treatment. Though the tics, especially the vocaliza- • weakness or PARALYSIS on one side of the body tions and articulations, can be disconcerting, • blurred or double vision (DIPLOPIA) 288 The Nervous System

• ringing in the ears (TINNITUS) person can remain in a persistent vegetative state • progressive loss of cognitive function and mem- for months to years. ory Risk Factors and Preventive Measures • seizures Blows to the head are the primary risk factor for • personality changes traumatic brain injury. Preventive measures include wearing seat belts, helmets, and other pro- The diagnostic path begins with an assessment tective equipment. Appropriate training and meth- of any history of trauma to the head, such as falls ods reduce the risk for head injuries that occur or MOTOR VEHICLE ACCIDENTS. When a single event is during sporting events and competitive athletics. not apparent, the doctor will look for cumulative See also COGNITIVE FUNCTION AND DYSFUNCTION; injury. A NEUROLOGIC EXAMINATION can identify MEMORY AND MEMORY IMPAIRMENT; SEIZURE DISORDERS; signs of sensory or motor disturbances that suggest STROKE. the areas of the brain where there may be injury. Diagnostic imaging procedures, such as COMPUTED tremor disorders Conditions in which there is TOMOGRAPHY (CT) SCAN or MAGNETIC RESONANCE IMAG- damage to the areas of the BRAIN that regulate or ING (MRI), often reveal signs of injury such as sub- coordinate movement, resulting in involuntary, dural or intracranial HEMATOMA, cranial FRACTURE, rhythmic back-and-forth movements of the or altered brain structure. ELECTROENCEPHALOGRAM extremities (most commonly the hands) and (EEG) may provide further evidence in the form of sometimes the head. Such damage may result abnormal electrical activity in certain areas of the from STROKE; injury; or, some researchers specu- brain. late, the cumulative effect of NEURON loss over the course of the lifetime. Tremor disorders become Treatment Options and Outlook increasingly common with advancing age. The Treatment depends on the cause and extent of the most common tremor disorder is benign essential injury. Surgery is often necessary to drain col- tremor, which affects about five million Americans lected BLOOD (hematoma), relieve pressure, most of whom are age 60 or older. remove BONE fragments or other matter when there is an open wound, or repair damaged blood BENIGN ESSENTIAL TREMOR vessels. Most treatment targets maintaining and VERSUS PARKINSON’S DISEASE restoring brain function through PHYSICAL THERAPY, Though tremor is a symptom of PARKINSON’SDIS- OCCUPATIONAL THERAPY, and speech therapy. A per- EASE, Parkinson’s disease is not a tremor disorder son may need to relearn basic activities of daily and tremor disorders do not indicate a person living, or to use his or her nondominant hand. has Parkinson’s disease. The tremors that charac- Rehabilitation may also target lost abilities such as terize Parkinson’s disease are most intense when reading or writing. The extent of recovery the hands are still and diminish with activity. depends on the nature of the injury and the per- Tremors of benign essential tremor are most son’s overall health status and age. Though trau- intense during activity and may entirely disap- matic brain injury typically results in some degree pear when the affected limbs are at rest. of permanent symptoms, many people are able to recover enough to return to an acceptable level of Symptoms and Diagnostic Path independent living. Tremors tend to develop gradually and may Significant injury may result in COMA (UNCON- worsen during times of stress or anxiety. They first SCIOUSNESS that extends for a few hours to a appear as mild and intermittent trembling. Over month) or persistent vegetative state (uncon- time the movement becomes more clearly rhyth- sciousness that persists beyond a month). Though mic and begins to interfere with tasks such as CT scan or MRI can help the neurologist monitor holding a pen to write. Tremors may also affect the state of physical damage within the brain, it is the VOCAL CORDS, making the voice sound waver- difficult to project the likelihood for recovery. A ing. This is the point at which people tend to seek unconsciousness 289 medical care. The diagnostic path begins with a people who mutations in one or both of two complete PERSONAL HEALTH HISTORY and family genes, etm1 and etm2. Researchers suspect as yet health history. The neurologist conducts a NEURO- unidentified mutations in other genes are respon- LOGIC EXAMINATION, and may conduct COMPUTED sible for tremor disorders in people who do not TOMOGRAPHY (CT) SCAN or MAGNETIC RESONANCE IMAG- have etm1 or etm2 mutations. Other tremor disor- ING (MRI) of the brain to look for changes that sug- ders may have genetic components as well. gest other causes for the tremors. The diagnosis Tremor disorders are far more common in people combines the neurologist’s clinical observations who are older than age 60 than in those who are about the characteristics of the tremor with nega- younger. However, there are no known measures tive findings for other causes. to prevent tremor disorders. See also DYSKINESIA; GENE; MUTATION; PARESTHESIA. Treatment Options and Outlook Medications to mitigate tremors include beta block- unconsciousness A state in which a person is ers such as propanolol, certain Antiseizure medica- unaware of and does not interact with the exter- tions (notably primidone), and MUSCLE relaxants nal environment. The most common experiences such as alprazolam. BOTULINUM THERAPY, in which of unconsciousness are sleep, fainting (SYNCOPE), the neurologist injects botulinum toxin into and general ANESTHESIA. Unconsciousness may also affected muscles to paralyze them, can provide occur with CONCUSSION, seizures, HYPOTENSION (low long-term relief for some people. Surgical interven- BLOOD PRESSURE), ENCEPHALITIS, ENCEPHALOPATHY, and tions such as DEEP BRAIN STIMULATION and THALAMO- INTOXICATION. Most people are easily aroused from TOMY may be options for tremors that fail to respond the unconsciousness of sleep though people who to less invasive treatments. Most people are able to are unconsciousness due to other causes may not find treatments that minimize the extent to which arouse until or if the underlying cause resolves. tremors interfere with their daily activities. See also ARRHYTHMIA; BRAIN DEATH; CONSCIOUS- NESS; COMA; LONG QT SYNDROME (LQTS); PAROXYSMAL Risk Factors and Preventive Measures ATRIAL TACHYCARDIA (PAT); PERSISTENT VEGETATIVE Benign essential tremor appears to run in families. STATE; SEIZURE DISORDERS; WOLFF-PARKINSON-WHITE About half of tremor disorders appear to occur in SYNDROME. THE MUSCULOSKELETAL SYSTEM

The musculoskeletal system encompasses the bones, muscles, tendons, ligaments, and fasciae. Practitioners who diag- nose and treat health conditions of the musculoskeletal system are orthopedists (also called orthopedic surgeons). Orthopedists may further specialize in sports medicine or physiatry (rehabilitative medicine).

This section, “The Musculoskeletal System,” pres- trapezium 1 each wrist bicuspid 4 top, 4 bottom, ent a discussion of the structure and function of trapezoid 1 each wrist in pairs on each side the bones, muscles, and other connective tissues. capitate 1 each wrist of MOUTH It also contains entries about the health condi- hamate 1 each wrist molar 6 top, 6 bottom, tions that can affect musculoskeletal function.The metacarpal (hand): 10 3 at the back of each section “The Nervous System” contains entries for 5 each hand side of mouth conditions that affect musculoskeletal function phalanx (finger): 28 but are primarily neurologic in nature. 14 each hand Major Skeletal Muscles innominate (pelvis): 2 head, neck, and shoulders Structures of the Musculoskeletal System fusion of ilium, ischium, frontalis Bones pubis 1 each side orbicularis oculi axial SKELETON: 80 bones spine: 26 upper leg: 2 masseter head (cranium): 8 ervical vertebrae 7 femur 1 each leg temporalis frontal 2 thoracic vertebrae 12 patella (kneecap): 2 medial pterygoid parietal 1 lumbar vertebrae 5 1 each leg trapezius temporal 2 sacrum 1 lower leg: 4 semispinalis capitis occipital 1 coccyx 1 fibula 1 each leg splenis capitis ethmoid 1 sternum: 1 tibia 1 each leg sternocleidomastoid sphenoid 1 ribs: 24 tarsal (ankle): 14 arm auditory ossicles: 6 12 pairs each side talus 1 each ankle deltoid malleus 1 each ear appendicular skeleton: 120 bones calcaneus 1 each ankle biceps incus 1 each ear clavicle (collarbone): 2 navicular 1 each ankle triceps stapes 1 each ear scapula (shoulder blade): 2 cuboid 1 each ankle brachialis face: 14 upper arm: 2 cuneiform 3 each ankle brachioradialis lacrimal 2 humerus 1 each arm metatarsal (foot): 10 palmaris longus nasal 2 lower arm: 4 5 each foot extensor carpi radialis zygoma 2 radius 1 each arm phalanx (toe): 28 flexor carpi radialis turbinate 2 ulna 1 each arm 14 each foot extensor carpi ulnaris vomer 1 carpal (wrist): 16 TEETH (permanent): 32 flexor carpi radialis maxilla 2 scaphoid 1 each wrist incisor 4 top, 4 bottom, extensor digitorum palate 2 lunate 1 each wrist front center of mouth lexor digitorum mandible 1 triquetrum 1 each wrist cuspid 2 top, 2 bottom, abductor pollicis brevis hyoid: 1 pisiform 1 each wrist each side of mouth abductor pollicis longus 290

The Musculoskeletal System 293

torso leg synchronization with bone-destroying cells (osteo- pectoralis major pectineus clasts) which remove old bone structure. pectoralis minor sartorius Framework: the skeleton The 206 bones of the serratus anterior adductor longus adult human skeleton give the body shape, pro- external oblique rectus femoris tection, and mobility. There are two divisions of internal oblique adductor magnus the skeleton: intercostal gracilis diaphragm biceps femoris • The axial skeleton forms the body’s central transverse abdominus semitendinosus alignment; its bones are primarily those of sup- rectus abdominis vastus lateralis port and shelter. iliopsoas vastus medialis • The appendicular skeleton “hangs from” the back semimembranosus axial skeleton; its bones are primarily those of teres major tibialis anterior movement. infraspinatus tibialis posterior rhomboideus major gastrocnemius Bones provide the structure that gives the body latissimus dorsi soleus resistance against gravity and makes movement gluteus maximus peroneus longus possible. Long bones, such as those in the arms gluteus medius flexor hallucis and legs, function as levers for the skeletal mus- obturator extensor cles to generate movement and locomotion. A honeycombed structure within the long bones Functions of the Musculoskeletal System reduces their density and weight while increasing The musculoskeletal system gives the body form their STRENGTH. The compact construction of short and structure, protects the internal organs, and bones, such as those in the hands and feet, sup- provides movement. It determines body height ports functions that require greater strength and and mass. It is the foundation for facial features, less leverage. Flat bones, such as the scapulae hand characteristics, and athletic ability. The (shoulder blades) and pelvis (hip bones), provide bones of the SKELETON form the core of the struc- surface area for firmly anchoring the large skeletal tural body; the muscles build the body’s outward muscles that make movement possible. appearance. In tandem, the bones and the muscles Some bones function as armor, protecting vital carry the body through life. structures and organs. The smooth, thick bones of A soft start: the skeleton’s origins The SKELETON the skull completely encase the BRAIN in a cham- arises from the mesoderm very early in embryonic ber that has few natural points of entry. Vertebrae development, taking rudimentary form at about separated by cushions of cartilage enclose the three weeks of gestational age. Hyaline CARTILAGE, SPINAL CORD, their irregular shapes deflecting access a tough, dense type of connective tissue, forms the while at the same time permitting FLEXIBILITY. The template that will become the ossified (mineral- ribs form a cage that contains the HEART and LUNGS, hardened) skeleton. Though the process of ossifi- providing a framework for the bellows-like action cation begins before birth, the greater percentage of the lungs with the thick sternum like a shield to of the skeleton is still cartilage at birth to facilitate shelter the heart. passage through the birth canal. Form and function: the muscles The 650 or so After birth an intricate, HORMONE-regulated muscles in the body give the body shape and process immediately sets about to convert cartilage make movement, including locomotion, possible. cells (chondrocytes) to BONE cells (osteocytes). This The skeletal muscles cover and protect the bones, process of ossification takes the first two decades attaching directly to them. Muscles also support of life to reach fruition. Bone tissue continues to and protect other structures such as BLOOD vessels grow and change throughout life even after bone and nerves. Most skeletal muscles work in oppos- size reaches stability through another process ing pairs, with one MUSCLE group contracting and called bone remodeling, in which bone-building the other relaxing in synchronization to permit cells (osteoblasts) create new bone structure in the balanced, coordinated, and smooth move- 294 The Musculoskeletal System ments necessary for all body mobility from sitting establishes unconscious awareness of the body’s to running. location within its physical environment. Proprio- Muscle cells form collective structures, muscle ception helps the brain interpret and respond to fibers, that are the functional units of movement. the myriad messages about the body’s relation to NERVE impulses from motor neurons (nerve cells gravity and speed. that direct movement) travel from the NERVOUS Harder than bone: the teeth The TEETH are the SYSTEM to the muscle fibers. The NEUROTRANSMITTER hardest structures in the body, formed of calcium acetylcholine facilitates the transfer of the impulse and other minerals with a nearly impermeable from the NEURON to the muscle fiber. Some muscle enamel coating. The jaw bones—the maxilla fibers remain in a state of partial contraction, pro- (upper jaw) and the mandible (lower jaw)— viding muscle tone that supports posture. Other anchor the teeth. Like most mammals, humans muscle fibers contract and relax in rapid sequence, have two sets of teeth, the deciduous (sometimes providing muscle strength. called primary, milk, or baby teeth) and the per- Connecting structures: tendons, ligaments, and manent. Deciduous teeth begin to erupt through fasciae Specialized structures of connective tissue the gum line at about age four months; they drop join the bones and the muscles. Tendons, fibrous out and permanent teeth replace them starting at bands that arise from muscle, join muscle to bone. about age six or seven years. The adult mouth Ligaments are tough and sinewy; they connect contains 32 permanent teeth, generally occurring bones to each other. Sheetlike FASCIA covers the in pairs on each side of the mouth. They are of muscles, connecting muscle to muscle and muscle three major structures: to SKIN. Articulating interfaces: the joints The ends of • Incisors and cuspids have sharp surfaces for cut- the bones come together in various ways that ting; these teeth are in the front of the mouth. facilitate their movement. Hinge joints, such as • Molars have flat surfaces for grinding and crush- the knee and the elbow, allow flexion and exten- ing; these teeth are in the back of the mouth. sion. Ball and socket joints, such as the hips and • Bicuspids, sometimes called premolars, function shoulders, allow rotational movement. The joints somewhat as transitional structures, capable of of the cranium—called sutures—are fused, allow- secondary biting and preliminary chewing; they ing no movement at all. The vertebrae—the bones are in the middle of the jaw line. of the spine—have slight movement between each but collectively allow the body to bend in half. Within the calcium cap is the tooth’s living tis- Most joints contain cartilage, the body’s most sue, the pulp. Hollow extensions penetrate deep dense type of connective tissue, to cushion and into the bones of the jaw, their protective canals protect the bones. Cartilage is very smooth, almost encasing the nerves and blood vessels that supply slick, permitting movement with minimal resist- the pulp. Chips and cracks in the enamel occur ance. Synovial fluid lubricates larger joints, fur- over time, weakening its protection and allowing ther reducing friction. A thin coat of cartilage BACTERIA to penetrate and begin to destroy the cal- covers the caps of the long bones in the arms and cium cap, exposing the inner pulp. This kind of the legs. Thick pads of cartilage cushion the knees damage—dental caries (cavities)—is the leading and the vertebrae, joints that bear considerable oral health challenge. The teeth also facilitate force with movement such as walking. speech, functioning like reflective walls to amplify Biomechanics of movement Movement is a sound and providing resistance for the tongue as it function of leverage and resistance that represents reshapes sound into words. a complex and intricate interaction among the nerves, muscles, connective tissues, and bones. Health and Disorders The cerebral cortex coordinates the numerous of the Musculoskeletal System processes that make movement possible, integrat- The musculoskeletal system carries the human ing external sensory data with internal messages. body hundreds of thousands of miles in the course A specialized sensory process, PROPRIOCEPTION, of a typical lifetime. Trauma notwithstanding, it The Musculoskeletal System 295 does so with few “maintenance” requirements and OSGOOD-SCHLATTER DISEASE OSTEOARTHRITIS little complaining. Proper nutrition and regular OSTEOGENESIS IMPERFECTA OSTEOMALACIA physical exercise are about all the bones, muscles, OSTEOMYELITIS OSTEOPENIA and connective structures require for most of life. OSTEOPETROSIS OSTEOPOROSIS However, the musculoskeletal system is vulnera- PAGET’S DISEASE OF THE BONE PATELLOFEMORAL SYNDROME ble to numerous hereditary, congenital, and PLANTAR FASCIITIS POLYDACTYLY acquired health conditions. Trauma is the most POLYMYOSITIS REITER’S SYNDROME significant risk to the musculoskeletal structures, REPETITIVE MOTION INJURIES RHABDOMYOMA particularly the limbs and joints. Sprains, strains, ROTATOR CUFF IMPINGEMENT SCIATICA and fractures are common injuries. Over time, the SYNDROME SKELETAL DYSPLASIA repeated trauma of daily function also takes its SPASM SPINAL STENOSIS toll. OSTEOARTHRITIS, the consequence of degenera- SPRAINS AND STRAINS SYNDACTYLY tive damage to the joints, is the most common SYNOVITIS TALIPES EQUINOVARUS musculoskeletal ailment, affecting as many as 60 TEMPOROMANDIBULAR DISORDERS TENDONITIS million Americans. TORTICOLLIS Hereditary and congenital disorders can affect both the structure and function of the muscu- Traditions in Medical History loskeletal system—and by extension, of other sys- Not until the end of the Renaissance did physi- tems of the body as well. Connective tissue, the cians and scientists fully understand the structure foundation of the musculoskeletal system, exists of the human musculoskeletal system. The skele- in nearly every body structure. Disorders of con- ton represented death; only without flesh was it nective tissue such as MARFAN SYNDROME affect not visible. Seeing a bone, even in life, was never a only the skeleton and muscles but the walls of the good thing. Fractures, particularly compound frac- arteries and the structure of organs. Though many tures in which the bone ends broke through the movement disorders are neurologic in origin, dis- surface of the skin, were frequently fatal. INFEC- orders of muscle function such as MUSCULAR DYS- TION was nearly inescapable. Fractures that did not TROPHY also affect mobility and motor function. kill often maimed; ancient doctors had little knowledge of biomechanics and without guidance HEALTH CONDITIONS from technology commonplace today, setting a OF THE MUSCULOSKELETAL SYSTEM fracture was at best an imprecise art. ACHILLES TENDON INJURY ACHONDROPLASIA The discovery of the X-RAY—electromagnetic ADHESIVE CAPSULITIS ANKLE INJURIES energy capable of penetrating soft tissue—in the ANKYLOSING SPONDYLITIS ARTHROGRYPOSIS late 19th century finally gave doctors a means to BACK PAIN BAKER’S CYST examine the bones of living people. With X-ray BONE CANCER BONE SPUR doctors could see the bone ends of fractures and BURSITIS CARPAL TUNNEL SYNDROME realign those ends for proper HEALING, and ortho- CERVICAL SPONDYLOSIS CHARCOT-MARIE-TOOTH (CMT) pedic medicine was born. Today X-ray remains the CHONDRITIS DISEASE quintessential diagnostic tool for skeletal injuries. CONGENITAL HIP DYSPLASIA CONTRACTURE CRAMP DISLOCATIONS Breakthrough Research and Treatment Advances DYSTONIA EPICONDYLITIS Today’s technology allows incredible visualization FIBROMYALGIA FRACTURE of musculoskeletal structures, well beyond the GOUT HERNIA black-and-white X-ray, and of musculoskeletal HERNIATED NUCLEUS PULPOSUS INFECTIOUS ARTHRITIS functions—with minimal intrusion into the body. KNEE INJURIES KYPHOSIS Nucleotide bone scans, MAGNETIC RESONANCE IMAG- LIPOMA LORDOSIS ING (MRI), ULTRASOUND, and COMPUTED TOMOGRAPHY MARFAN SYNDROME MUSCULAR DYSTROPHY (CT) SCAN allow doctors to “see” injuries such as MYASTHENIA GRAVIS MYOPATHY torn ligaments, ruptured tendons, and stress frac- MYOTONIA NEUROGENIC ARTHROPATHY tures. Arthroscopy uses fiberoptic technology to 296 The Musculoskeletal System view the inside of a JOINT, providing a method of have identified many of the GENE mutations minimally invasive visualization for diagnostic and responsible for muscular dystrophy, for example. therapeutic purposes. Though GENE THERAPY as treatment for genetically As in most areas of health and medicine, the based musculoskeletal conditions remains experi- most significant breakthroughs in research and mental, the potential is great for treatments that treatment for musculoskeletal conditions comes can reverse the effects of gene mutations to halt from new discoveries in genetics. Researchers and correct disease processes. A

Achilles tendon A thick, strong band of connec- flats), and jumping are activities that place the tive tissue at the back of the heel that joins the Achilles tendon at risk for injury. gastrocnemius and soleus muscles of the calf (back Achilles tendonitis causes PAIN and tenderness of the lower leg) to the calcaneus (heel BONE). The to touch at the base of the calf muscles on the Achilles TENDON makes possible extension of the back of the leg. The inflamed area may appear foot, a necessary element of walking, running, swollen. Though the pain may restrict the ability and jumping. A sharp tap to the Achilles tendon to use the foot and ankle, the mechanical func- with a REFLEX mallet causes the foot to jerk down- tions of the Achilles tendon remain intact, and the ward; this is the Achilles tendon reflex. Motor person can perform the movements necessary to NEURON diseases such as AMYOTROPHIC LATERAL SCLE- walk. Achilles tendonitis may follow a competitive ROSIS (ALS) and post-polio syndrome produce event that places high stress on the legs, such as a abnormal Achilles tendon reflex responses. race, or may develop during a new training regi- Injury to the Achilles tendon affects the ability men. to move the foot down. The Achilles tendon is An Achilles rupture occurs suddenly during vulnerable to damage during running and jump- movement that stresses the Achilles tendon, such ing, and especially “plant and twist” kinds of as running. The Achilles tendon is especially vul- movements, common in numerous sports such as nerable to quick movements that place extreme baseball, basketball, tennis, soccer, football, and stress on it, such as a “plant and twist” maneuver running. The tendon may become inflamed (TEN- in sports such as tennis, soccer, basketball, soccer, DONITIS) or tear (rupture). and football. Runners may tear the Achilles ten- For further discussion of the Achilles tendon don when starting from blocks or when accelerat- within the context of musculoskeletal structure ing for the finish. The injury causes a popping and function, please see the overview section “The sensation, followed by pain and an inability to Musculoskeletal System.” move the ankle and foot very well. When the tear See also ACHILLES TENDON INJURY; LIGAMENT; is complete, severing the Achilles tendon, the per- POLIOMYELITIS. son cannot point the foot downward to perform the basic movements of walking. Pain is most Achilles tendon injury Traumatic damage to the often at the back of the heel. ACHILLES TENDON, the broad band of connective tis- The ability to move the foot is generally the dis- sue that joins the calf muscles to the heel of the tinguishing factor between Achilles tendonitis and foot. The most common Achilles TENDON injury is Achilles tendon rupture. The doctor’s examination INFLAMMATION, called Achilles TENDONITIS, tends to includes testing the Achilles tendon reflex, prob- develop somewhat gradually as an overuse injury. ing for areas of sensitivity (palpable divot), and A tear in the Achilles tendon, called a rupture, watching the person move the feet with the legs generally happens suddenly during an athletic dangling (seated on an examination table) and activity or event. Extended running, especially when walking. Diagnostic imaging procedures uphill or in shoes with flat heels (such as racing such as MAGNETIC RESONANCE IMAGING (MRI) and

297 298 The Musculoskeletal System

ULTRASOUND can confirm the diagnosis though usu- • enlarged head and prominent forehead ally are not necessary unless the doctor suspects a • short arms and legs complete rupture and needs to assess the extent • short hands and short, thick fingers with a dis- and location of damage before surgery to repair it. tinct separation between the middle and ring Most Achilles tendon injuries heal with ice, fingers rest, and NONSTEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS) to reduce inflammation and pain. The • abnormalities in the opening at the base of the doctor may choose to cast the lower leg and foot BRAIN, the foramen magnum, and in the verte- to immobilize the ankle when the injury is severe. brae that compress the SPINAL CORD, affecting Surgery is usually necessary to repair significant or BREATHING total Achilles tendon rupture. HEALING is complete • craniofacial anomalies such as narrow nasal when the person can move the injured foot with passages, flat NOSE, and short jaw the same ease and range of motion as the unin- jured foot, which may take six weeks to three Evaluation for an infant born with achon- months for repair and six months for rehabilita- droplasia typically includes COMPUTED TOMOGRAPHY tion, depending on the injury’s severity. Swim- (CT) SCAN, ULTRASOUND, or MAGNETIC RESONANCE ming is an excellent activity for rehabilitation, as it IMAGING (MRI) to evaluate the extent of skeletal allows full range of motion and use of the Achilles anomalies, especially those that may affect the tendon without impact. spinal cord and thus vital functions such as Stretching and WARM-UP before athletic activi- breathing. Some infants also have or develop ties, including WALKING FOR FITNESS, are the most HYDROCEPHALY (fluid accumulation within the cra- effective methods for reducing the risk of injury to nium), which may require a shunt for draining the Achilles tendon. People who have tight calf the excess fluid. As they grow, children who have muscles or previous Achilles tendon injury benefit achondroplasia are vulnerable to KYPHOSIS (a hump from regular stretching (once or twice daily) in the upper back) and LORDOSIS (curvature of the regardless of athletic activity. lower spine). They are also susceptible to frequent See also ANKLE INJURIES; ATHLETIC INJURIES; BONE OTITIS media (middle EAR INFECTION) because the SPUR; SPRAINS AND STRAINS. shortened facial structures mean the eustachian tubes, valvelike structures between the middle ear achondroplasia A genetic disorder in which the and the THROAT, are also shorter than normal and rate CARTILAGE cells (chondrocytes) convert to BONE do not function properly. cells is greatly slower than normal, resulting in Though some children may benefit from bone- skeletal abnormalities such as shortened limbs and lengthening operations, in most situations there diminished height. Achondroplasia is the most are no treatments to normalize the development of common cause of SKELETAL DYSPLASIA, commonly bone. Bone-lengthening surgery is extensive and called dwarfism. Though achondroplasia can occur expensive, has significant risk for side effects (such as an autosomal dominant inherited genetic disor- as infection and permanent damage to the bones), der, it more commonly occurs as a spontaneous and is controversial among medical experts. Some MUTATION of a GENE on CHROMOSOME 4 that encodes specialists use HUMAN GROWTH HORMONE (HGH) SUP- fibroblast growth factors, the proteins that regu- PLEMENT early in the child’s life, though this is also late cartilage cell conversion. Prenatal testing can controversial and does not produce predictable identify whether a FETUS has achondroplasia, results. Adults who have achondroplasia generally though doctors generally offer the test only when reach a maximum height of about four feet. there is reason to suspect the condition could be See also EUSTACHIAN TUBE; GENETIC COUNSELING; present or along with other GENETIC TESTING. GENETIC DISORDERS; INHERITANCE PATTERN; OPERATION; Because infants born with achondroplasia have SURGERY BENEFIT AND RISK ASSESSMENT. distinctive physical features, the disorder is obvi- ous at birth. adhesive capsulitis A condition in which the The characteristics of achondroplasia include JOINT capsule of the shoulder joint fuses (adheres) aging, musculoskeletal changes that occur with 299 to the head of the humerus (long BONE of the though remains limited. A few people experience upper arm), causing PAIN and constricting range of residual pain and contractures that result in long- motion. Doctors do not know what causes adhe- term disability. sive capsulitis, commonly called frozen shoulder. The condition may be primary, in which there are Risk Factors and Preventive Measures no contributory conditions, or secondary, in which Conditions that appear to increase the risk for other conditions exist that may cause changes that adhesive capsulitis include HYPERTHYROIDISM (over- allow adhesive capsulitis to develop. Adhesive active THYROID GLAND), DIABETES, and HYPERLIPIDEMIA capsulitis affects women somewhat more fre- (elevated CHOLESTEROL BLOOD LEVELS and TRIGLYC- quently than men and typically occurs in people ERIDE BLOOD LEVEL). Adhesive capsulitis is also more over age 50. common in people who have SPINAL CORD INJURY, PARKINSON’S DISEASE, certain forms of NEUROPATHY, Symptoms and Diagnostic Path and traumatic injury to the structures of the Adhesive capsulitis begins with acute pain in one shoulder. Despite these correlations, doctors do shoulder that occurs for no obvious cause. Within not know what initiates the onset of adhesive cap- weeks to months adhesions (scarlike tissue) sulitis and therefore do not know what measures develop that progressively limit the affected shoul- may prevent its development. der’s range of motion. Most people first notice See also CHRONIC PAIN; COMPLEX REGIONAL PAIN restricted movement when trying to reach up and SYNDROME; SURGERY BENEFIT AND RISK ASSESSMENT. behind, such as combing the HAIR, and when try- ing to reach back and behind, such as for a wallet aging, musculoskeletal changes that occur with in the pocket. The adhesions and range of motion The muscles, connective tissues, and SKELETON restrictions progress until the person has very lim- arise from the mesoderm in the EMBRYO at about ited use of the shoulder. In most people the adhe- two weeks of gestational age. The skeleton’s first sions gradually lessen and the pain subsides over a form is as fibrous membranes (the bones of the period of one to three years. Doctors sometimes cranium) or CARTILAGE. Through a process called refer to the three stages of adhesive capsulitis as ossification or osteogenesis, cartilage cells (chon- freezing, frozen, and thawing. drocytes) convert to BONE cells (osteoblasts, osteo- The pattern of symptoms is generally distinctive cytes, and osteoclasts). This early ossification uses enough to allow diagnosis. The doctor may choose the fibrous membrane (called intramembranous to perform diagnostic imaging procedures such as ossification) or the cartilage skeleton (called endo- X-RAY or MAGNETIC RESONANCE IMAGING (MRI) to rule chondral ossification) as a mold or template. Bone out other possible causes of the symptoms. cells replace the connective tissue cells to form the bone matrix. Treatment Options and Outlook Areas of specialized bone tissue called second- Because adhesive capsulitis is nearly always self- ary ossification centers form in the long bones; limiting, treatment primarily targets pain relief. these become the epiphyses or growth plates. Analgesic medications, heat, and PHYSICAL THERAPY After birth the epiphysis extends through the in combination may improve range of motion. growth of cartilage, which ossification then When symptoms are severe and do not respond to replaces as bone. The process extends through these measures, the doctor may recommend nearly the first two decades of life. Disorders of arthroscopic surgery to release the contractures. In ossification include ACHONDROPLASIA, MARFAN SYN- most people such surgery relieves the pain and DROME, ACROMEGALY, and OSTEOGENESIS IMPERFECTA. improves range of motion. MUSCLE structures gain definition, mass, and The entire course of adhesive capsulitis, treated STRENGTH as growth occurs. By four months of age 1 nonsurgically, typically spans 1 ⁄2 to 3 years, after a healthy infant can support his or her head and which about half of people recover completely at about six months can sit unsupported and roll with no residual pain or restrictions on range of over from front to back or back to front. Between motion. In some people range of motion improves 8 and 12 months, an infant begins to crawl, throw 300 The Musculoskeletal System things, and pull into a standing position. By 14 and lower leg; traumatic injury accounts for most months most infants are walking on their own, upper extremity amputations. Other causes of and by 18 months can run and jump. Motor amputation include uncontrollable OSTEOMYELITIS skills—the ability to use the musculoskeletal sys- (INFECTION of the BONE), severe PERIPHERAL VASCULAR tem for mobility—continue to evolve throughout DISEASE (PVD), and tumors. childhood. These skills, along with muscle mass US surgeons perform nearly 200,000 amputa- and BONE DENSITY, peak in the late 20s. tions each year. Surgical amputation is a treat- By age 40, musculoskeletal structures and func- ment of last resort, becoming an option only tions begin to decline. Joints begin to show the when other treatments fail and leaving the limb effects of wear. One health consequence of this is threatens the person’s health. Surgical amputation OSTEOARTHRITIS, which can become severe enough is a major OPERATION performed in a hospital. For to warrant JOINT REPLACEMENT. Softening of the lig- most amputations the person stays 2 to 10 days in aments and other connective tissues makes joints the hospital. more vulnerable to injury. Muscle mass and bone density gradually decrease, as does strength and Surgical Procedure FLEXIBILITY. In women these decreases become dra- With the person asleep under general ANESTHESIA, matic with MENOPAUSE, with the sudden and signif- the surgeon cuts through the SKIN and MUSCLE to icant decline in estrogen. (Estrogen is one of the reach the bone, structuring the incisions so tissue hormones that influences the movement of cal- remains to create a flap that covers the surgical cium between the BLOOD circulation and the wound. The surgeon may need to use a saw to cut bones.) The rate of decrease remains fairly con- the bone, though in some circumstances the stant in men, who have inherently larger amounts amputation takes place at the JOINT (called a disar- of muscle and bone. ticulation). For limb amputation the surgeon However, by about age 75 or 80 gender differ- shapes the bone ends and remaining tissue to sup- ences balance out. Men and women alike have port a prosthesis. significantly less muscle tissue and bone structure, When there is no infection or risk for infection increasing susceptibility to injury from falls and is minimal, the surgeon closes the surgical wound other accidents. Though bone remodeling contin- by suturing the muscles together around the bone ues, it proceeds at a much slower pace. Other and pulling tissue and skin over the end in a flap. changes in the body may result in bone resorption outpacing bone rebuilding. The risk for neuromus- Risks and Complications cular disorders such as PARKINSON’S DISEASE also The primary risks of amputation are excessive rises. At age 80, a woman may have lost four bleeding during surgery and infection and poor inches or more of her height as a consequence of HEALING after surgery. The risk for infection is musculoskeletal changes. Men also lose height, highest in people who have problems with BLOOD though typically not as dramatically. circulation in the extremities, such as may occur See also ACCIDENTAL INJURIES; AGING, NEUROLOGIC in PVD or diabetes. People who have diabetes may CHANGES THAT OCCUR WITH; ESTROGENS; HIP FRACTURE be slow to heal from the surgery of amputation, IN OLDER ADULTS; HORMONE; LIGAMENT; RHEUMATOID usually an extension of the complications of dia- ARTHRITIS. betes that made necessary the limb amputation. Complications such as failure to heal or spreading amputation Removal or loss of a limb or body GANGRENE (dead tissue) require a follow-up surgery part. Amputation may be surgical, in which the to attempt to improve the surgical wound for bet- removal is intentional to treat a disease condition, ter healing. or traumatic, in which accidental injury results in the loss of the body part. Most amputations Outlook and Lifestyle Modifications involve digits (fingers and toes) and limbs. In the Recovery and limitations depend on the type of United States, complications of DIABETES account amputation and the underlying health conditions. for the majority of surgical amputations of the foot With focused PHYSICAL THERAPY and OCCUPATIONAL ankle injuries 301

THERAPY, most people can return to a satisfactory are lateral or inversion injuries. When the foot level of function and participation in many of the rolls outward, the damage occurs to the structures activities they previously enjoyed. A PROSTHETIC on the inside of the foot; these are medial or ever- LIMB often allows nearly normal function. Adap- sion injuries. A sharp blow or twist can break the tive devices and equipment can improve safety, base of the tibia or more commonly the fibula (the mobility, and independence. People who have smaller of the lower leg bones). A severe LIGAMENT amputations as a result of severe chronic disease stretch or tear can pull a piece of the bone away, such as diabetes or PVD often find they have bet- called an avulsion FRACTURE. Repeated stress such ter QUALITY OF LIFE after amputation because the as occurs with intense running or jumping can remaining tissue of the limb is healthy. cause stress fractures in the bones of the ankle or Amputation may be emotionally difficult for OSTEOARTHRITIS within the ankle JOINT. the person as well as for his or her loved ones. The loss of a body part may affect the person’s self- Symptoms and Diagnostic Path image and self-esteem. Some people feel guilty PAIN and swelling after a sudden twist or blow to about their health situations, and others feel angry the ankle are the typical symptoms of ankle or depressed. The health-care team generally injury. Both can be intense, and most people are includes a social worker or psychologist to help reluctant to or cannot bear weight on the affected the person go through the grieving process and ankle. There is a strong correlation between the cope with the range of feelings and emotions. severity of symptoms, including the ability to walk See also ACCIDENTAL INJURIES; OCCUPATIONAL or bear weight, and the type or seriousness of HEALTH AND SAFETY; PHANTOM PAIN; SURGERY BENEFIT injury. When it is possible to bear weight on the AND RISK ASSESSMENT. ankle immediately following the injury and there is no pain to the lower portion of the fibula, frac- ankle injuries Sprains and fractures of the ankle ture is unlikely. The doctor may order an X-ray of resulting from accidental trauma. The ankle is vul- the ankle to rule out fracture. nerable to twisting under the pressure of sudden, unexpected movement. Though ankle injuries are Treatment Options and Outlook common ATHLETIC INJURIES, they also occur during The mainstay of treatment for ankle injuries of routine activities such as stepping off a curb, walk- any kind is RICE—rest, ice, compression, and eleva- ing on uneven surfaces, and walking in high tion. An elastic wrap may help support the injured heels. OBESITY AND HEALTH conditions that impair ankle, though caution is necessary to make sure balance increase the risk for ankle injuries. Doc- the wrap is not too tight, particularly during the tors in the United States treat about 4 million first 48 hours when the ankle may continue to ankle injuries each year, most of which are sprains swell. The doctor may choose to cast a serious (injury to ligaments and tendons). sprain. Fractures require casting or surgery or Three bones come together to form the ankle: both. Casting is generally adequate for simple frac- the tibia and fibula, the long bones of the lower ture in which the broken bone remains nondis- leg, and the talus, a platform-like BONE that forms placed (stays in relative alignment). Displaced, the back of the foot. Three sets of strong ligaments comminuted, and open fractures typically require hold these bones in place; equally strong muscles pins, screws, or plates to hold the bones in place and tendons give the ankle range of motion. This while they heal. Sometimes this hardware structure is necessary because the ankle bears the remains in place and sometimes the surgeon body’s weight. Transferring that weight from one removes it when HEALING is complete, depending foot to the other when walking places the equiva- on the nature of the fracture. 1 lent of 1 ⁄2 times the body’s weight on the weight- Most simple strains (injury to the muscles and bearing ankle and foot. tendons) heal in 4 to 6 weeks. A simple sprain Most ankle injuries occur when the foot rolls (injury to the ligaments), which doctors may clas- inward, which stretches, tears, or otherwise dam- sify as grade 1 or grade 2, generally heals in 4 to 6 ages structures on the outside of the ankle; these weeks. A severe sprain (grade 3) may take 12 to 302 The Musculoskeletal System

16 weeks to fully heal. Doctors consider healing that primarily affects the spine. The inflammation complete when the injured ankle can bear the permanently damages the vertebrae (bones of the body’s weight without pain and with normal spine), causing outgrowths of bony tissue that fuse range of motion during normal activities, though vertebrae to one another such that their mobility very severe injuries may result in permanent limi- and range of motion can become extremely lim- tations or laxity. ited. Ankylosing spondylitis, sometimes called Marie-Strümpell disease, is one of the AUTOIMMUNE Risk Factors and Preventive Measures DISORDERS related to RHEUMATOID ARTHRITIS. In most Slipping, twisting, and falling are the most com- people who develop the condition, symptoms mon risks for ankle injury. MOTOR VEHICLE ACCI- remain confined to the spine. However, in some DENTS, athletic activities that involve running and people inflammation also involves structures of jumping, and recreational activities such as down- the EYE (IRITIS and UVEITIS), the HEART valves, the hill skiing are also frequent causes of ankle LUNGS, and other joints such as the shoulders and injuries. People who are physically inactive or hips. who have had multiple ankle strains may have WEAK ANKLES, a circumstance in which the liga- Symptoms and Diagnostic Path ments supporting the ankle are soft or lax. Exces- Early symptoms of ankylosing spondylitis are gen- sive body weight places further stress on the eral and include low BACK PAIN and stiffness, espe- ankles and may cause the foot to turn inward, cially upon awakening. The PAIN often becomes stretching the muscles and connective tissues in intense at night, which is the primary reason any ways that limit their ability to provide stability people seek medical evaluation. Over time the during movement such as walking. OSTEOPOROSIS, stiffness and pain may spread to the entire back, a condition of diminished BONE DENSITY, makes shoulders, and hips. As the condition progresses, the bones of the ankle vulnerable to fracture additional symptoms may include loss of spine under circumstances that otherwise would not FLEXIBILITY and range of motion, constricted move- cause injury. Osteoporosis is a particular risk in ment of the chest (from inflammation of the joints women who are past MENOPAUSE and in men over connecting the ribs to the spine), fatigue, and age 65. hunched or stooped posture. Regular weight-bearing activity such as walking The diagnostic path typically includes a com- helps strengthen the structures of the ankle. Peo- prehensive medical examination and PERSONAL ple who are prone to ankle injuries may choose to HEALTH HISTORY, X-rays of the spine, and BLOOD tests wrap, tape, brace, or otherwise support their to look for signs of inflammation within the body. ankles during activities that involve increased risk Because symptoms are fairly general until the for unexpected twisting, such as running or sports. condition is well advanced, early diagnostic efforts A physical therapist can teach specific exercises to look for more common causes such as OSTEO- strengthen weak ankles and improve FLEXIBILITY. ARTHRITIS. WARM-UP exercises to stretch and loosen the ankles are important before engaging in physical Treatment Options and Outlook activities. It is important to wear the right shoes Treatment typically combines prescription medica- for the activity, to give the foot and ankle proper tions such as ANTI-INFLAMMATORY DRUGS (NSAIDS) support. Worn-out shoes, even if designed for the and PHYSICAL THERAPY with lifestyle measures such particular activity, increase the risk for injury. as daily physical exercise, stretching and flexibility See also ACHILLES TENDON INJURY; FLAT FEET; MUS- activities, and techniques to support upright pos- CLE; PHYSICAL THERAPY; RESISTANCE EXERCISE; SHIN ture. Some people experience symptom relief and SPLINTS; SPRAINS AND STRAINS; TENDON; WALKING FOR delayed progression of the condition with medica- FITNESS; WEEKEND WARRIOR. tions used to treat rheumatoid arthritis, such as DISEASE-MODIFYING ANTIRHEUMATIC DRUGS (DMARDS). ankylosing spondylitis A form of chronic, Though treatment cannot prevent the vertebrae degenerative arthritis (INFLAMMATION of the joints) from fusing, lifestyle measures can help retain arthrogryposis 303 maximum functional capacity of the spine. Many Symptoms and Diagnostic Path doctors aim for a goal of shaping the fusion so the The doctor may suspect arthrogryposis when the spine remains erect, which allows better mobility pregnant mother reports that the movements of than when the spine fuses into a hunched pos- her unborn baby are infrequent. ULTRASOUND can ture. Ankylosing spondylitis is a lifelong condition. detect the changes in soft tissue structure and BONE fusions at the joints before birth; the joint Risk Factors and Preventive Measures deformities are obvious at birth. The delivery of an Ankylosing spondylitis typically begins before age infant who has arthrogryposis may be challenging 40 and is more common in men. It is also more when the affected joints prevent normal passage common in people who have INFLAMMATORY BOWEL through the birth canal. The obstetrician may rec- DISEASE (IBD) and in people of Native American ommend CESAREAN SECTION to avoid injury to heritage. Researchers have identified a GENE, HLA- infant and mother. Ultrasound after birth may B27, associated with ankylosing spondylitis. The provide additional information about the extent to HUMAN LEUKOCYTE ANTIGENS (HLAS) are proteins on which contractures affect the infant’s joints as well the surfaces of cell membranes that identify the as help doctors determine whether there are other cells to the IMMUNE SYSTEM. HLA-B27 is one of the anomalies present. numerous genes that encodes for HLAs. Researchers believe this variant of the gene pre- Treatment Options and Outlook disposes an individual for ankylosing spondylitis Treatment depends on the extent of the contrac- though does not inevitably result in the condition. tures though typically combines surgery to correct Remaining as active as possible helps extend the joint deformities and casting with aggressive PHYSI- spine’s flexibility and range of motion. CAL THERAPY to restore as much function as possi- See also CERVICAL SPONDYLOSIS; GENETIC PREDISPO- ble. Surgery can relieve the abnormal tension SITION; REITER’S SYNDROME; ROUTINE MEDICAL EXAMI- shortened connective tissue and MUSCLE structures NATION; X-RAY. place on the joints, and the surgeon often can reconstruct more functional alignments to arthrogryposis The collective term for a group of improve movement of the joint. Surgery may also congenital disorders, also called arthrogryposis restructure bone tissue, generally in multiple multiplex congenita, in which multiple contrac- operations timed with growth patterns throughout tures restrict JOINT function throughout the body. childhood. Physical therapy helps strengthen the Joints may be partially or completely fused. tissues and extend range of motion. Researchers believe about 30 percent of arthrogry- Although the deformities are permanent, they posis develops when the FETUS is not able to move are not progressive; thus the condition does not freely in the UTERUS before birth. The restricted worsen as the child grows. Aggressive treatment movement causes muscles and connective tissues early in life may allow a relatively normal lifestyle such as tendons and ligaments to grow abnor- in late childhood and adulthood when contractures mally around the immobile joints, fixing them in are mild to moderate. Severe contractures tend to their positions. Circumstances that may restrict result in permanent disabilities that require adap- fetal movement include tive techniques and devices for mobility.

• insufficient AMNIOTIC FLUID Risk Factors and Preventive Measures • abnormalities of the uterus Inability of the fetus to move freely in the uterus is the primary risk factor for arthrogryposis. • large UTERINE FIBROIDS Pregnancies in women who have neuromuscular • twins or other multiples disorders such as MYASTHENIA GRAVIS, MULTIPLE SCLE- • neurologic and other developmental anomalies ROSIS, or MYOTONIA are at higher risk. Extended high in the fetus, such as MUSCULAR DYSTROPHY or FEVER during PREGNANCY, such as may occur with MITOCHONDRIAL DISORDERS, that inhibit normal serious INFECTION, may affect the development of movement the fetus in ways that impair muscle, connective 304 The Musculoskeletal System tissue, and NERVE structure and function. These mild to moderate ANALGESIC MEDICATIONS for PAIN impairments secondarily affect joint function. relief, depending on the extent of discomfort he or About 30 percent of arthrogryposis is heredi- she feels. Because the entry into the joint is mini- tary, though affected parents may have such mild mal, many people experience little discomfort or symptoms that they do not know they have the pain after the procedure. condition. When one or both parents have arthro- gryposis, there is increased risk the infant will also Risks and Complications have the condition. GENETIC TESTING and GENETIC As with any surgical procedure, arthroscopy has a COUNSELING may help such parents evaluate their risk for excessive bleeding and INFECTION. However, risk and make FAMILY PLANNING decisions. these complications are uncommon. Soreness and See also CONGENITAL ANOMALY; CONTRACTURE; bruising at the incision sites is common though GENETIC DISORDERS; LIGAMENT; SURGERY BENEFIT AND usually mild. When the arthroscopic examination RISK ASSESSMENT; TALIPES EQUINOVARUS; TENDON. reveals more extensive damage than the orthope- dic surgeon can repair arthroscopically, the opera- arthroscopy A MINIMALLY INVASIVE SURGERY proce- tion may become an open surgery with longer dure that allows an orthopedic surgeon to view recovery and rehabilitation periods. the inside of a JOINT using a lighted, flexible endo- scope adapted for this use, called an arthroscope. Outlook and Lifestyle Modifications Arthroscopy, also called arthroscopic surgery, has Most people recover from arthroscopic procedures both diagnostic and therapeutic applications. fully and without complications, returning to their Inserted into the joint through a small incision, regular activities within several days to two the arthroscope has a tiny camera at its tip that weeks, depending on the surgeon’s recommenda- sends images to a monitor. The orthopedic sur- tion and the type of procedure. Arthroscopic pro- geon manipulates the arthroscope and specially cedures generally repair injuries that have limited designed instruments to examine the joint and the person’s mobility or function, so most people repair damage to CARTILAGE, LIGAMENT, TENDON, and are much improved after their operations and may other tissues. Arthroscopy has largely replaced return to activities their injuries had prevented OPEN SURGERY for most operations on the joints them from performing. except JOINT REPLACEMENT. See also ENDOSCOPY; MENISCECTOMY; SURGERY BEN- EFIT AND RISK ASSESSMENT. Surgical Procedure The orthopedic surgeon performs arthroscopy in a athletic injuries ACCIDENTAL INJURIES that occur hospital operating suite or an AMBULATORY SURGERY during athletic activities or sporting events. Though facility. Most arthroscopies are same-day (outpa- a certain degree of risk is inherent in athletic tient) procedures, with the person arriving a few events, particularly competitions, most athletic hours before the scheduled arthroscopy and going injuries occur for three main reasons. They are home a few hours after the surgeon completes the procedure. ANESTHESIA may be regional (a NERVE • inadequate CONDITIONING or TRAINING block that numbs the limb) or general (puts the • insufficient WARM-UP and pre-event preparation person to sleep). The orthopedic surgeon makes • inappropriate or improperly fitted clothing, two or more small incisions around the JOINT: one shoes, equipment, or protective gear for the insertion of the arthroscope, one for inser- tion of the irrigating catheter, and others for inser- Athletic injuries may be acute (occur suddenly) tion of the arthroscopic instruments. Most or chronic (develop over time). The most common arthroscopic procedures take 20 to 60 minutes. acute injuries are SPRAINS AND STRAINS—damage to After the arthroscopic operation, the person the soft tissue structures of the musculoskeletal sys- rests in the recovery area until the anesthetic is tem. Also common are fractures and open wounds fully worn off and the person is comfortable (cuts and scrapes). Chronic injuries among recre- enough to go home. Generally the person receives ational, collegiate, and professional athletes gener- athletic injuries 305 ally arise from overuse and may result in discom- COMMON ATHLETIC INJURIES fort and limitations of use long after athletic partic- ACHILLES TENDON INJURY ANKLE INJURIES ipation ends. OSTEOARTHRITIS, EPICONDYLITIS, and BLISTER BURSITIS PATELLOFEMORAL SYNDROME are the most common CHAFING CHARLEYHORSE chronic injuries among athletes. CONCUSSION contusion (bruising) Training and conditioning activities that CRAMP DISLOCATIONS improve overall STRENGTH, FLEXIBILITY, and EPICONDYLITIS fasciitis ENDURANCE can significantly reduce the risk for FRACTURE KNEE INJURIES injury. Equally important is proper technique LACERATIONS (cuts and scrapes) PATELLOFEMORAL SYNDROME (including clothing and equipment) for the activity. SHIN SPLINTS SPRAINS AND STRAINS It is worthwhile to attend clinics and classes for spe- STINGER TENDONITIS cific activities to learn methods and techniques that both improve performance and reduce the risk for See also BLISTER PREVENTION; CROSS-TRAINING; DIS- injury. Most athletic injuries are preventable. ABILITY AND EXERCISE; YOGA. B

back pain PAIN that arises from injury to the Symptoms and Diagnostic Path structures of the spine. Most back pain involves Back pain, whether acute or chronic, may be the soft tissue structures—muscles, ligaments, ten- sharp, dull, shooting, persistent, intermittent, or dons, and CARTILAGE. Back pain is very common, achy in character. The nature and location of the affecting nearly every adult at some time in his or pain sometimes helps the doctor determine the her lifetime and is second only to HEADACHE as a cause. Most back pain results from soft tissue reason for missing work. Though most back pain injury; unless there are neurologic symptoms, heals without residual consequences, chronic back such as weakness or numbness in the legs or arms, pain (back pain that continues beyond three to six the doctor may recommend a trial of conservative months) remains the leading cause of occupa- treatment before progressing to diagnostic testing. tional disability. Pain that persists requires further diagnostic effort Acute back pain develops suddenly, a conse- that may include X-RAY, COMPUTED TOMOGRAPHY (CT) quence of traumatic injury or surgery, and SCAN, or MAGNETIC RESONANCE IMAGING (MRI). These improves when the underlying cause improves. imaging procedures help the doctor visualize the The low back (lumbar spine) and the neck (cervi- structure of the spine to determine whether there cal spine) are the most vulnerable to traumatic is deterioration or other injury that could be press- injury. Low back strain is a common injury often ing on spinal NERVE roots and other structures of related to overuse, incorrect lifting (including the back to produce pain. lifting too much weight), and sudden twisting movements. Cervical strain often results from Treatment Options and Outlook incorrect posture, especially prolonged sitting in Most acute back pain improves with conservative the same position, or whiplash-type trauma in treatment to relieve INFLAMMATION. Such treatment which the head moves suddenly and more rap- may include alternating heat and cold to the area idly than the body in a whipping fashion that of pain, ANALGESIC MEDICATIONS for pain relief, NON- stretches muscles and ligaments. Chronic back STEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS) to pain is pain that exists or continues when there is relieve inflammation and pain, and sometimes no pathologic reason and more often affects the MUSCLE RELAXANT MEDICATIONS when MUSCLE spasms low back. are a problem. Some doctors recommend a day or two of relative inactivity to allow the back muscles to rest and relax, though some studies show HEAL- ING Back PAIN with accompanying numb- occurs more rapidly in mild to moderate back ness or weakness in the legs may indi- pain when people continue their regular activities cate damage to NERVE structures. Neck (except strenuous exercise or heavy lifting). pain with FEVER or headache may indi- Treatment for chronic back pain depends on cate serious INFECTION (ENCEPHALITIS or what underlying reasons the doctor can identify MENINGITIS). These circumstances require that could be accountable. Complementary meth- immediate medical evaluation. ods such as ACUPUNCTURE, various types of MASSAGE THERAPY, CHIROPRACTIC manipulation, and OSTEO- 306 bone 307

PATHIC MANIPULATIVE TREATMENT (OMT) often provide whether other factors are involved. Occasionally a relief. YOGA and PHYSICAL THERAPY are methods for Baker’s cyst is a symptom of a torn meniscus (CAR- improving FLEXIBILITY and STRENGTH after the initial TILAGE in the knee), in which case treatment such injury heals. as surgery may be necessary. Nearly always a Baker’s cyst eventually goes away without treat- Risk Factors and Preventive Measures ment. Key risk factors for back pain include occupational See also ARTHROSCOPY; BURSITIS; KNEE INJURIES; risk (jobs that require heavy lifting, pushing, or OSTEOARTHRITIS; SYNOVITIS; TENDONITIS. pulling), OBESITY, physical inactivity, and cigarette smoking. Most back pain occurs as a result of injury bone The rigid tissue that gives the body struc- to the back, commonly strained muscles or ture and mobility. Bone consists of living cells con- sprained ligaments. Regular physical exercise to tained within a mineralized structure called the maintain strength and flexibility reduces the risk bone matrix. Collagen fibers form intricate net- for such injury and aids in weight loss efforts when works to which crystals of calcium phosphate, cal- excessive body weight is a factor. Proper lifting cium carbonate, and other mineral compounds technique and good posture are also important. adhere, forming the dense and rigid structure See also ACUTE PAIN; ANKYLOSING SPONDYLITIS; CER- familiar as bone. Despite its density and its impres- VICAL SPONDYLOSIS; CHRONIC PAIN; CONDITIONING LIGA- sion as a static structure, bone is in a perpetual MENT; OSTEOARTHRITIS; SCIATICA; SPASM; SPINAL CORD state of change, called remodeling. Throughout INJURY; TENDON. life certain processes destroy old bone and other processes construct new bone. Baker’s cyst A fluid-filled sac, also called a popliteal cyst, that forms at the back of the knee. Bone Cells The cyst develops when there is a tear in the syn- Three types of cells make up bone tissue: ovial capsule (the membranous structure contain- ing the fluid that lubricates the JOINT) that allows • Osteoblasts form new bone. In response to synovial fluid to leak into the ears of least resist- stimulation from hormones such as CALCITONIN, ance, which is the popliteal fossa. The leaking ESTROGENS, and TESTOSTERONE, osteoblasts draw fluid bulges out from the knee joint or forms a calcium and other minerals into the bone to connection with a BURSA in the back of the knee. strengthen and solidify the bone matrix. Either circumstance allows synovial fluid to col- Osteoblasts produce a collagen-based substance lect, forming a noticeable lump behind the knee. called osteoid. Calcium, phosphorus, magne- A Baker’s cyst is soft to the touch and usually sium, and other minerals bind with the osteoid painless, though a large cyst can be uncomfortable to form mineralized bone (the bone matrix). or painful with movement or pressure. • Osteocytes make up the structure of existing bone. Contained within the bone matrix, osteo- NOTHING TO DO WITH BAKING cytes have a lifespan of 20 years or more. It is a common assumption that the term Baker’s Osteocytes begin their lives as osteoblasts, then cyst has something to do with being a baker, just become enclosed in the bone’s mineralized as bricklayer’s shoulder tends to afflict bricklay- structure. The spaces they occupy within the ers and tennis elbow develops in people who mineralized framework are lacunae. Each frequently play tennis (both conditions are forms lacuna has a rich BLOOD supply to nourish and of BURSITIS). But Baker’s cyst takes its name from support the osteocytes. the British surgeon who first identified it: William Morrant Baker (1839–1896). • Osteoclasts remove old bone. Osteoclasts derive from monocytes and are phagocytic; they encir- cle and consume cellular debris. As they con- When the cyst causes PAIN, the doctor may use sume old bone tissue, osteoclasts release its MAGNETIC RESONANCE IMAGING (MRI) to determine calcium into the blood circulation. PARATHYROID 308 The Musculoskeletal System

HORMONE plays a key role in regulating this fluids, and other cells. The structure of cancellous release. The process of bone resorption leaves bone is more elastic than that of compact bone, vacant lacunae on the surface of the bone that allowing the bones to absorb compression such as subsequently fill with new bone structure. occurs with walking, running, and jumping. Can- cellous bone has less than half the density of com- In health, osteoblasts and osteoclasts function pact bone but many times more the surface area. in relative balance so the rate of new bone forma- Some bones contain a center channel, the tion matches the rate of old bone destruction. This medullary canal, that houses BONE MARROW. In process of bone remodeling is one of maintenance, children every bone contains red bone marrow, not growth. Bone growth, in which the bones the type of bone marrow that produces new blood increase in size, occurs through ossification (con- cells. By adulthood only the long bones, sternum, version of CARTILAGE cells to bone cells). Imbalance and hip bones contain appreciable amounts of red may result from disease processes that alter HOR- bone marrow. Yellow bone marrow, a mix of col- MONE levels in the body or when calcium levels in lagen and fatty tissues, occupies the innermost the blood circulation are too low. Calcium is vital layer of most other bones. Some bones do not to numerous cellular activities and crucial for MUS- contain any marrow. CLE contraction and the conduction of NERVE sig- A thin but tough membrane called the perios- nals; when its levels in the blood circulation are teum covers the surface of the bones except at the inadequate, the body accelerates bone resorption joints. It forms the attachment surface for tendons so it can withdraw calcium from the bones. and ligaments. The periosteum contains a rich network of blood vessels and nerves that help Bone Structure nourish the compact bone. Osteoblasts in the Were they solid, bones would weigh more than periosteum are “first responders” when there is the body could support or the muscles could injury to the bone, rapidly forming new bone for move. So instead they are a combination of densi- repair. The nerves in the periosteum are largely ties that provide a balance between STRENGTH and responsible for PAIN signals when there is injury to mass. Though all bones contain the same elements the bone. of structure, the particular combination of those elements varies according to the bone’s role. Types of Bones The outermost layer of bone, called compact The SKELETON contains four basic types of bones: bone or cortical bone, is made of multiple thin long, short, flat, and irregular. Long bones, such as layers, called lamellae, that contain tightly packed those in the arms and legs, must support the body’s osteocytes. Each lamella contains a somewhat dif- weight and mass. Their length and structure also ferent structure of cells, altering the density and allows them to function as levers to make move- orientation of the bone structure for maximum ment possible. A thin layer of compact bone pro- strength. Compact bone is heavily mineralized and vides the rigidity the long bones require; a very dense; tooth enamel is the only other sub- substantial middle layer of cancellous bone pro- stance in the body that is harder than compact vides added bone mass for strength and stability. bone. An intricate network of canals, called the The intricate trabecular structure of cancellous Haversian systems, bring blood vessels and nerves bone makes it much stronger for supporting through the lamellae to nourish and support com- weight, though more vulnerable to impact. At each munication among the osteocytes. Compact bone end of a long bone is the epiphysis, or growth plate, protects the inner bone structures and provides where ossification takes place during growth in the stiffness necessary to leverage the muscles for childhood. The shaft of a long bone is its diaphysis. movement. Lengthwise through the center of a long bone is a The middle layer of bone is cancellous, or medullary canal that contains bone marrow. spongy, bone, also called trabecular bone, where Short bones, such as those that form phalanges mineralized filaments form intricate networks of (metacarpals in the fingers and metatarsals in the walls and spaces. The spaces contain osteocytes, toes), are structurally long bones on a much bone cancer 309 smaller scale. However, a short bone does not PALATE/CLEFT PALATE AND LIP; JOINT; LIGAMENT; MONO- have a medullary canal or bone marrow. Flat CYTE; MUSCLE; PHAGOCYTE; SKELETON; TENDON. bones, such as the scapulae (shoulder blades), sternum (breastbone), and pelvis (hip bones), bone cancer Cancer that occurs in the tissues of serve as attachment surfaces for the large muscles the BONE, either as primary cancer (cancer that of movement. They contain a substantial thickness originates in the bone) or metastatic cancer (can- of compact bone with a thin layer of cancellous cer that spreads to the bone from an origin else- bone in the center. The sternum and the pelvis where in the body). Primary bone cancer is rare; also contain bone marrow. Irregular bones, such doctors in the United States diagnose about 2,500 as the vertebrae (bones of the spine), carpals people with primary bone cancer each year. Its (bones of the wrist), and tarsals (bones of the three forms are ankle), are primarily structures of compact bone with cancellous bone centers. • osteosarcoma, which arises from osteoid (the formative tissue of new bone) usually in the Bone Health and Disease upper leg or upper arm in young people ages Bones require a steady intake of dietary calcium 10 to 25 and other minerals as well as an adequate amount • Ewing’s SARCOMA, which results from a TRANSLO- of vitamin D, VITAMIN K, and various hormones to CATION GENE MUTATION and generally arises from maintain themselves. Deficiencies (and less com- the long bones (and occasionally soft tissue monly, excesses) of these substances alter bone structures) during ADOLESCENCE structure in ways that can affect bone function. • chondrosarcoma, which develops in the carti- Though a certain degree of demineralization lage of the shoulders or pelvis in adults over occurs naturally as a component of the aging age 50 process, excessive calcium loss results in thin and weak bones that are particularly vulnerable to Osteosarcoma accounts for about a third of pri- FRACTURE. Fracture is the most common health mary bone cancers. RADIATION THERAPY for other condition that affects the bones. Other health con- cancers increases the risk for osteosarcoma. ditions involving the bones include OSTEOPOROSIS, Though primarily a cancer of childhood, osteosar- INFECTION (OSTEOMYELITIS), and congenital muscu- coma sometimes occurs in older adults. Oncolo- loskeletal anomalies (BIRTH DEFECTS that affect gists (cancer specialists) often stage primary bone muscle and bone structure and function). cancer only as localized (one contained site) or metastasized (spread to multiple sites). HEALTH CONDITIONS THAT AFFECT THE BONES The bone is a common site for cancer that ACHONDROPLASIA arthrogryposis metastasizes from other sites in the body such as BONE cancer BONE SPUR the BREAST, PROSTATE GLAND, and COLON. Metastatic cleft palate FRACTURE cancer retains the name of its original site. Multi- KYPHOSIS LORDOSIS ple myeloma, a cancer of the BLOOD, also affects MARFAN SYNDROME OSGOOD-SCHLATTER DISEASE bone structure though is not a true bone cancer. OSTEOGENESIS IMPERFECTA OSTEOMALACIA OSTEOMYELITIS OSTEOPENIA Symptoms and Diagnostic Path OSTEOPOROSIS POLYDACTYLY The main symptom of bone cancer is PAIN, usually RHEUMATOID ARTHRITIS SCOLIOSIS at the site of the tumor. The pain may be present for SKELETAL DYSPLASIA SPINA BIFIDA several months before becoming intense enough for the person to seek treatment, or may develop For further discussion of bone structure and suddenly. Sometimes the first indication of bone function, please see the overview section “The cancer is a FRACTURE, either spontaneous (without Musculoskeletal System.” trauma) or as a consequence of minor trauma that See also AGING, MUSCULOSKELETAL CHANGES THAT would not fracture healthy bone. The diagnostic OCCUR WITH; CALCIUM AND BONE HEALTH; CLEFT path typically begins with X-rays, which can show 310 The Musculoskeletal System most bone cancers. COMPUTED TOMOGRAPHY (CT) DISEASE OF THE BONE; PROSTATE CANCER; SURGERY FOR SCAN, MAGNETIC RESONANCE IMAGING (MRI), and CANCER. radioisotope bone scan can provide greater detail about the tumor to aid in its diagnosis. POSITRON bone density The amount of mineral, primarily EMISSION TOMOGRAPHY (PET) SCAN can detect whether calcium, the bones contain that gives them their or to what extent the cancer has metastasized to mass. BONE density is important to give the SKELE- other sites in the body. A blood test to measure the TON enough structure to support the body. Insuffi- level of alkaline phosphatase, an enzyme cient bone density results in the bone loss osteoblasts release when configuring new bone tis- conditions OSTEOPENIA and OSTEOPOROSIS. Numerous sue, may suggest—though cannot confirm—bone hormones participate in maintaining bone density. cancer. Blood levels of this enzyme are normally Among them are estrogen, TESTOSTERONE, CALCI- high during periods of bone growth. Biopsy of the TONIN, vitamin D (in the form of calciferol), and tumor provides the definitive diagnosis. PARATHYROID HORMONE. Though calcium is the min- eral most commonly associated with bone struc- Treatment Options and Outlook ture and bone density, other minerals that also are Treatment depends on the location and size of the important, including magnesium and phosphorus. tumor. Treatment options for primary bone can- Bone density naturally diminishes with increas- cers include CHEMOTHERAPY, radiation therapy, and ing age, beginning at about age 35, at a rate of surgery to remove the tumor. Often, radiation about 2 percent per year. Because estrogen is par- therapy or chemotherapy administered first can ticularly essential for maintaining bone density in shrink the tumor so the surgeon can remove it women, bone density drops precipitously at without the need to amputate the involved limb. MENOPAUSE when a woman’s estrogen production Oncologists often administer chemotherapy both drops to nearly nothing. Because men’s bodies are before and after surgery. The course of larger, they inherently have greater bone mass. chemotherapy before surgery is typically 8 to 10 Testosterone contributes to this mass, as it does a weeks; chemotherapy after surgery may extend man’s greater MUSCLE mass. The natural decrease for a year. The oncologist is likely to add radiation in bone density is usually not a health concern therapy to the treatment regimen when there are until a man reaches his middle to late 60s. metastases the surgeon cannot safely remove. Treatment for metastatic cancer of the bone Disorders of Bone Density depends on the type of primary cancer and the Most health problems related to bone density arise degree of METASTASIS. from diminished bone mass, which presents The outlook after treatment depends on the increased risk for bone FRACTURE. Spontaneous extent of cancer present at the time of diagnosis. fracture (fracture that occurs without trauma or Significant surgery, such as AMPUTATION, requires other cause) is possible when bone density is very intensive rehabilitation. The outlook for metastatic low. The spine and the hip are at particular risk. cancer of the bone depends on the type of primary The most common of these conditions are cancer and the aggressiveness of metastatic disease. osteopenia (bone loss that places the individual at increased risk for fracture) and osteoporosis (bone Risk Factors and Preventive Measures loss that places the individual at significant risk for Though Ewing’s sarcoma has a clear genetic con- fracture). Compression fractures of the spine, in nection, doctors know little about the risk factors which the vertebrae collapse, can endanger the for and causes of other forms of primary bone SPINAL CORD; HIP FRACTURE IN OLDER ADULTS is a key cancer. Radiation exposure, such as radiation ther- cause of disability and death. Medications are apy to treat a different cancer, increases the risk available that stimulate bone growth, helping for osteosarcoma. There are no measures known restore lost bone mass. The doctor may prescribe to prevent bone cancer. such medications, along with lifestyle measures See also BREAST CANCER; CANCER TREATMENT such as RESISTANCE EXERCISE, to increase bone den- OPTIONS AND DECISIONS; COLORECTAL CANCER; PAGET’S sity. Excessive bone mass is far less common bursa 311 though may occur in conditions such as OSTEOPET- Because older adults have lower bone mass, the ROSIS. Z-score is less significant than the T-score for assessing the presence of osteopenia and osteo- Bone Density Testing porosis. Generally the T-score and the Z-score cor- A number of tests can measure bone density. relate; a person who has a low T-score also has a Among them are low Z-score. The difference between an individual’s bone • dual energy X-RAY absorptiometry (DEXA or density score and the representative standard DXA), which uses low-DOSE X-ray to measure score is the standard deviation (SD), reported as a the bone mass in the spine and hip positive (+) or negative (–) figure. Each full SD • peripheral dual energy X-ray absorptiometry represents about 10 percent of normal bone mass. (pDEXA or pDXA), which uses low-dose X-ray The lower the T-score, the greater the percentage to measure the bone mass in the wrist or heel of bone loss. A T-score that is 2.5 SDs or more • single-energy X-ray absorptiometry (SXA), below the norm (–2.5) is the diagnostic marker for which uses low-dose X-ray to measure the osteoporosis. bone mass in the wrist or heel BONE DENSITY SCORES • quantitative ULTRASOUND, which uses sound waves to measure the bone mass in the heel, Diagnostic Category T-Score Z-Score patella (kneecap), and tibia (long bone in the healthy –1 or higher –1 or higher lower leg) OSTEOPENIA (increased –1 to –2.5 –1 to –2.5 risk for fracture) • quantitative computed tomography (QCT), OSTEOPOROSIS (significant below –2.5 below –2.5 which uses X-ray to measure the bone mass in risk for fracture) the spine • peripheral quantitative computed tomography See also ESTROGENS; HORMONE; OSTEOMALACIA. (pQCT), which uses X-ray to measure the bone mass in the wrist bone spur An extension of BONE tissue, also called an osteophyte, that commonly develops DEXA provides the most detailed information near a JOINT. A bone spur has a jagged, pointed and is simple to perform. QCT and pQCT are varia- appearance. Doctors believe bone spurs develop as tions of COMPUTED TOMOGRAPHY (CT) SCAN that use a means of protecting a joint exposed to excessive somewhat higher doses of X-ray and are more com- stress or disease process. Most bone spurs do not plex to perform but can be more reliable in people cause symptoms, though may be apparent as who have already had fractures of the spine or hip. bumps in the MUSCLE or other soft tissue. Bone Mobile clinics and even some pharmacies use spurs cause PAIN when they irritate surrounding peripheral methods for screening. All testing meth- tissues such as MUSCLE and CARTILAGE. Bone spurs ods to measure bone density are painless, noninva- are especially common in the heels, hands, shoul- sive, and take 20 minutes or less to complete. ders, and spine. Bone density tests report two scores: NONSTEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS) often succeed in relieving the INFLAMMATION and • The T-score compares an individual’s bone den- pain. For bone spurs that cause substantial pain, sity to a figure that represents the bone density the doctor may inject the site with cortisone and a of a healthy adult in his or her mid-20s, the topical anesthetic agent to reduce inflammation period when bone density is at its highest. The and relieve pain. comparison is gender specific. See also ACHILLES TENDON INJURY; REPETITIVE • The Z-score compares an individual’s bone den- MOTION INJURIES. sity to a figure that represents other adults of the same age. The Z-score comparison is also bursa A fluid-filled sac between layers of MUSCLE gender specific. that buffers the movement of muscles against each 312 The Musculoskeletal System other. A synovial membrane, which secretes a affected. An adult has 130 to 160 bursae through- lubricating fluid (synovial fluid), lines the inside of out the body, any of which may become inflamed. the bursa. This is the same kind of membrane and The primary symptoms of bursitis are PAIN and fluid that encloses and lubricates the joints. Most swelling in the area of the involved bursa. When people have between 130 and 160 bursae there is also FEVER, an INFECTION may be the cause throughout their bodies, typically located near of the bursitis. Bursitis due to infection often joints. Bursae are vulnerable to INFLAMMATION requires surgical debridement (opening the bursa (BURSITIS) and fibrosis (scarring), both of which to remove damaged tissue and accumulated pus) cause pain and interfere with the bursa’s proper and treatment with ANTIBIOTIC MEDICATIONS. Inter- function. mittent cold packs over the affected area during For further discussion of bursae within the con- the first 48 hours of symptoms may slow inflam- text of musculoskeletal structure and function, mation and relieve pain. After 48 hours intermit- please see the overview section “The Muscu- tent heat provides greater relief. NONSTEROIDAL loskeletal System.” ANTI-INFLAMMATORY DRUGS (NSAIDS) further relieve See also CARTILAGE; JOINT; LIGAMENT; TENDON. inflammation and pain. Most bursitis improves in two to six weeks with bursitis INFLAMMATION of a BURSA, a fluid-filled such treatment. The doctor may inject a steroid sac between muscles or between muscles and BONE medication, alone or in combination with a local that protects tissues from friction during move- anesthetic agent, into a bursa that is causing ment. Bursitis is a common condition often associ- severe or chronic pain and restricting range of ated with overuse of particular joints though the motion. Though resting the affected JOINT is help- joints themselves are normal. Casual terminology ful in the early stages when the bursitis is most for bursitis often relates it to the activities that uncomfortable, regular physical activity hastens precipitate it, such as tennis elbow. Accidental falls HEALING and maintains full function of the joint. and blunt blows over bursae may also cause bursi- See also MUSCLE; OSGOOD-SCHLATTER DISEASE; tis, particularly of the deep bursae. Bursae near OSTEOARTHRITIS; REPETITIVE MOTION INJURIES; RHEUMA- the shoulder, elbow, hip, and knee are most often TOID ARTHRITIS; TENDONITIS. C

calcium and bone health The correlation OSTEOPENIA and OSTEOPOROSIS. Osteoporosis is the between dietary intake of calcium and the density leading cause of HIP FRACTURE IN OLDER ADULTS, and STRENGTH of the bones. Calcium is essential for which often results in long-term disability or pre- proper BONE structure, strength, and mass. The mature death. Though loss of bone density with bones contain about 99 percent of the calcium in aging is inevitable, lifelong measures such as ade- the body. From before birth until about age 30, quate calcium intake and daily weight-bearing the body adds calcium and other minerals to bone exercise can maintain bone health and prevent tissue to increase bone mass and strengthen the osteoporosis. skeletal structure. The SKELETON reaches peak bone The body must obtain calcium through dietary mass and strength in the late 20s. After age 30, sources or supplements. The amount of calcium bone mass begins to decrease. With increasing an individual needs changes across the spectrum age after 30 the body’s ability to absorb dietary of age. The years of ADOLESCENCE are among the calcium diminishes. Cigarette smoking and long- most vulnerable for inadequate calcium consump- term excessive ALCOHOL consumption accelerate tion because teens tend to drink much less milk the decrease. It is important for long-term bone and eat fewer dark green vegetables, the primary health that peak bone mass be as high as possible. dietary sources of calcium in the American diet. Regular weight-bearing exercise, such as walking and running, stimulates the growth of new bone CALCIUM INTAKE NEEDS tissue. Age Daily Adequate Intake (AI) Amount of Calcium BONES: THE BODY’S CALCIUM BANK birth to 3 years 500 milligrams (mg) Calcium is a vital mineral for many activities in 4 to 8 years 800 mg cells throughout the body, including the conduc- 9 to 18 years 1300 mg tion of NERVE signals and the contraction of MUS- 19 to 50 years 1000 mg CLE cells. The body uses the calcium stores in the 51 years and older 1200 mg bones to meet its other needs for calcium when dietary intake does not meet those needs and Natural dietary sources of calcium include dairy calcium in the BLOOD circulation drops. CALCI- products (milk, cheese, yogurt), dark leafy vegeta- TONIN and PARATHYROID HORMONE are the hor- bles such as spinach and broccoli, and tree nuts mones that primarily regulate calcium transport such as almonds and pecans. Many foods sold in between the blood circulation and the bones. the United States are calcium-fortified (contain added calcium). They include orange juice, cere- als, breads, SOY milk, and soy products such as Without adequate calcium the bones can tofu. Low-fat dairy products, which have lower become dangerously thin and weak, making them amounts of saturated fats, are the more healthful susceptible to FRACTURE under circumstances that choice and contain just as much calcium as higher otherwise would not harm the bones. The key fat products. Labels on packaged foods in the health conditions of inadequate BONE DENSITY are United States state, per serving, the food’s calcium 313 314 The Musculoskeletal System

DIETARY SOURCES OF CALCIUM Food Source Serving Size Amount of Calcium per Serving almonds 3 ounces 210 milligrams (mg) blackstrap molasses 1 tablespoon 170 mg bok choy (cooked) 1 cup 160 mg broccoli (cooked) 1 cup 60 mg canned salmon (with bones) 3 ounces 180 mg canned sardines (with bones) 3 ounces 325 mg clams (steamed) 3 ounces 80 mg collards 1 cup 265 mg cottage cheese 1 cup 155 mg crab (steamed) 3 ounces 90 mg hard cheese (cheddar, swiss) 1 ounce 225 mg kale (cooked) 1 cup 95 mg milk 1 cup 300 mg mollusks (steamed) 3 ounces 80 mg mozzarella cheese 1 ounce 200 mg okra 1 cup 125 mg provolone cheese 1 ounce 205 mg raisins 1 cup 75 mg rhubarb (cooked) 1 cup 345 mg

1 ricotta cheese ⁄2 cup 335 mg sauerkraut 1 cup 70 mg spinach (cooked) 1 cup 245 mg turnip greens (cooked) 1 cup 200 mg yogurt 8 ounces 425 mg carpal tunnel syndrome 315 content and its percentage of the daily adequate See also CRAMP; DIET AND HEALTH; EXERCISE AND intake (AI) amount. HEALTH; HYPERCALCEMIA; HYPERPARATHYROIDISM; HYPO- Three forms of calcium are commonly available CALCEMIA; HYPOPARATHYROIDISM; MINERALS AND as dietary supplements: calcium carbonate, cal- HEALTH; PARATHYROID GLANDS; SMOKING AND HEALTH; cium citrate, and calcium phosphate. However, VITAMINS AND HEALTH. many doctors believe the form of calcium matters far less than maintaining adequate intake of cal- carpal tunnel syndrome A collection of symp- cium. Individuals have varying tolerances and toms resulting from compression of the median responses to the different forms of calcium supple- NERVE as it passes through the carpal tunnel, a nar- ments. Many doctors recommend calcium carbon- row channel in the carpal bones of the wrist. The ate in the form of chewable antacid tablets as the ligaments that form the carpal tunnel can become most available, easiest to take, and least expensive irritated and inflamed, constricting the median calcium supplement product. Because numerous nerve and the tendons in the area. The median factors influence how much calcium the gastroin- nerve supplies the inside of the hand, the thumb, testinal tract absorbs, health experts recommend and the first three fingers (the ulnar nerve sup- obtaining as much calcium as possible through plies the outside of the hand and the little finger). dietary sources with calcium supplementation to Compression of the nerve affects sensation and make up the difference. Total calcium consump- function in the hand. tion that exceeds 2000 milligrams (mg) a day does not provide any added benefit and may cause Symptoms and Diagnostic Path health problems due to excessive calcium. Symptoms of carpal tunnel syndrome progress The body also requires vitamin D to absorb gradually over months to years. They may include dietary calcium. The primary sources of vitamin D are sunlight and dietary supplements. The body • tingling can synthesize (make) as much vitamin D as it • numbness needs with adequate SKIN exposure to sunlight. • weakness However, many people do not get enough sun- light. SUN PROTECTION products, necessarily applied • loss of ability to use the thumb and first two or to protect against SUNBURN block the ultraviolet three fingers rays that activate vitamin D synthesis. As well, • PAIN that shoots from the hand up the forearm there is not adequate ultraviolet light exposure during the winter months for people who live in Some people also experience perceptible the northern hemisphere—in the United States, swelling and tenderness to touch over the wrist. above a line roughly drawn from San Francisco to Symptoms are generally intermittent at the onset Boston. Because of these factors, most calcium- and progress to occur more frequently and have fortified foods also contain supplemental vitamin greater intensity. The diagnostic path includes tests D. Inadequate vitamin D causes softness of the of the hand and wrist that are able to bring on or bones—RICKETS in children and OSTEOMALACIA in intensify the symptoms. The doctor may order adults—regardless of calcium intake because the electromyogram (EMG) and nerve conduction body cannot absorb calcium without vitamin D. studies for further diagnostic information. Though insufficient calcium intake is by far the more significant health issue because of the effect Treatment Options and Outlook it has on bones, excessive calcium consumption Treatment efforts attempt to manage symptoms has potentially serious adverse effects on the body conservatively, with measures such as NONS- systemically. Excessive calcium can cause ARRHYTH- TEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS), injec- MIA (irregularity in the HEART RATE), MUSCLE tion of a corticosteroid, and splinting. When fluid cramps, kidney stones (NEPHROLITHIASIS), and NERVE retention (edema) is a factor, diuretic medications disturbances. (“water pills”) may help. Some people experience 316 The Musculoskeletal System improvement in their symptoms when they take STRAINS; SURGERY BENEFIT AND RISK ASSESSMENT; TEN- vitamin B6 (pyridoxine) supplements. Certain DON. YOGA postures that increase FLEXIBILITY and STRENGTH of the wrists improves symptoms for cartilage Dense connective tissue that provides some people. Surgery, either open or laparoscopic, the foundation for BONE in the developing fetus to cut the carpal LIGAMENT is the curative treatment and covers bone ends in the joints in adults. The for most people who have carpal tunnel syn- fetal SKELETON forms first as a translucent type of drome. Such an OPERATION opens the carpal tun- cartilage called hyaline cartilage, with conversion nel, relieving compression against the median to bone beginning at about the fourth week of nerve. Full recovery from the open procedure pregnancy. Calcification continues after birth. In takes about 12 weeks and from the laparoscopic the adult skeleton, hyaline cartilage forms the procedure about 8 weeks. A rare complication of disks between the vertebrae in the back, the rings carpal tunnel surgery is permanent weakness in that give the TRACHEA stability, and the extensions the hand as a consequence of cutting the median that connect the ribs to the sternum. A type of nerve. Other possible complications, also rare, cartilage that contains fibers of elastin that allow include excessive bleeding and postoperative greater FLEXIBILITY, called elastic cartilage or yellow INFECTION. cartilage, gives shape to the outer ears (auricles), auditory canal (EAR canal), and end of the NOSE. Risk Factors and Preventive Measures Cartilage consists of a thick, somewhat elastic Doctors believe many people who develop carpal base of collagen (an insoluble protein) with small tunnel syndrome have an inherently narrow clusters of cartilage cells (chondrocytes) suspended carpal tunnel, making the passage tighter. within it. Though cartilage does not have its own Women, who have smaller BONE structures than BLOOD or NERVE supplies, it continuously renews men, are three times more likely to develop carpal itself through a process called remodeling in tunnel syndrome. Carpal tunnel syndrome may which chondrocytes facilitate a slow turnover of also follow injury to the wrist, such as strain or collagen molecules and other substances. This FRACTURE, or accompany OSTEOARTHRITIS of the remodeling provides chondrocytes with the NUTRI- wrist. People who have DIABETES, PERIPHERAL VASCU- ENTS they need to function. LAR DISEASE (PVD), and other conditions associated Researchers believe imbalances in the remodel- with NEUROPATHY (injury to the nerves) are particu- ing process, in which the breakdown of collagen larly susceptible to compression syndromes such molecules exceeds rebuilding, is the basis for as carpal tunnel syndrome. OSTEOARTHRITIS. Various mechanisms, notably Work that subjects the wrists to continuous repeated trauma such as through use of the joints vibration or repetitive movement also increases the and activation of CYTOKINES through the inflamma- risk for carpal tunnel syndrome. The highest risk is tory process, contribute to this imbalance. Damage among people who do assembly-line work, such as to cartilage is the foundation of osteoarthritis, HER- in manufacturing, professional sewing, meat pack- NIATED NUCLEUS PULPOSUS, and most KNEE INJURIES. ing, and poultry processing. Job tasks in these occu- For further discussion of cartilage within the pations subject the wrists to repeated flexing under context of musculoskeletal structure and function, pressure. Though occupations involving extensive please see the overview section “The Muscu- typing, keyboarding, or data entry were long sus- loskeletal System.” pected as prime causes of carpal tunnel syndrome, See also BURSA; JOINT; LIGAMENT; TENDON. recent studies support only a slight increase in risk. Frequent short breaks to stretch and flex the wrists cervical spondylosis Narrowing of the channel during work and wearing supportive wrist braces between the vertebrae in the neck through which can help prevent carpal tunnel syndrome or mini- the SPINAL CORD passes. Cervical spondylosis results mize its symptoms. from chronic, degenerative OSTEOARTHRITIS in which See also ENDOSCOPY; OCCUPATIONAL HEALTH AND there is extensive INFLAMMATION and damage to the SAFETY; REPETITIVE MOTION INJURIES; SPRAINS AND CARTILAGE disks that separate and cushion the cervi- Charcot-Marie-Tooth (CMT) disease 317 cal vertebrae (bones of the neck). The damage is before they reach their destinations. CMT is the permanent and eventually restricts the movement most common inherited neuromuscular disorder of the neck. Pressure against the NERVE roots of the in the United States, affecting about 150,000 spinal cord may cause tingling or loss of sensation Americans. CMT is slowly progressive though not in the shoulders and arms. Sometimes the pressure fatal, with symptoms typically beginning in late also causes weakness of the muscles in the upper ADOLESCENCE or early adulthood. back and the arms. Cervical spondylosis is more There are numerous forms of CMT, each arising common in people over age 60. from MUTATION of different genes that encode the Symptoms of cervical spondylosis include proteins that form the myelin sheath. The most common is CMT1, which occurs in three autoso- • stiffness in the neck mal dominant variations that cause abnormal • HEADACHE structure in the myelin sheath: • PAIN along the back of the neck that radiates • CMT1A results when the person inherits an into the shoulders and upper arms extra copy of the GENE on CHROMOSOME 17 that • abnormal sensation in the upper back and encodes peripheral myelin protein 22 (PMP- arms, sometimes extending to the hands and 22), causing excessive production of PMP-22. fingers • CMT1B occurs as a result of mutations to the The diagnostic path includes X-RAY of the neck gene that encodes myelin protein 0 (MP-0). and upper back, which typically reveals the • CMT1C results from mutations to genes that changes in the alignment of the vertebrae as well encode for other peripheral myelin proteins, as the formation of bone spurs and calcifications though researchers have not yet identified the within the disks. Additional imaging procedures mutations. such as COMPUTED TOMOGRAPHY (CT) SCAN, MAGNETIC RESONANCE IMAGING (MRI), and myelogram (injec- Other forms of CMT include tion of radio-opaque dye into the spinal column) • CMT2, in which there are defects in the axons often show the degree to which the spondylosis of the peripheral nerves rather than in the compresses the nerve roots or, when degeneration structure of the myelin sheath is severe, the spinal cord itself. Treatment options include NONSTEROIDAL ANTI- • CMT3, also called Dejerine-Sottas disease, INFLAMMATORY DRUGS (NSAIDS) to relieve inflamma- which results from mutations to the MP-0 or tion and pain. A soft cervical collar that PMP-22 gene and causes severe symptoms immobilizes the neck allows the muscles of the beginning in the first year of life neck to relax, helping inflammation to recede. • CMT4, in which various gene mutations cause Injections of steroid medications can often reduce symptoms that begin in childhood and progress inflammation that does not respond to other treat- to complete loss of motor function of the lower ments. Heat and PHYSICAL THERAPY aid HEALING and extremities by adolescence restoration of movement. Though cervical • CMTX, which arises from a mutation in the spondylosis is a chronic and progressive condition, connexin 32 gene on the X chromosome and most people are able to obtain relieve through a causes more severe symptoms in males combination of medical and lifestyle methods. See also ANKYLOSING SPONDYLITIS; BACK PAIN; BONE Occasionally CMT occurs as a spontaneous SPUR; CHRONIC PAIN; LIFESTYLE AND HEALTH. mutation, without family history of the disease, and may affect any of the genes that encode for Charcot-Marie-Tooth (CMT) disease An inher- myelin proteins. ited neuromuscular disorder in which the myelin sheath that covers and protects the PERIPHERAL Symptoms and Diagnostic Path NERVES deteriorates. The loss of the myelin sheath Symptoms affect primarily the legs and feet in allows NERVE signals to escape from the nerves most forms of CMT, though in some forms may 318 The Musculoskeletal System also affect the arms and hands. Though the motor feet. Despite the progressive nature of CMT, the symptoms of CMT are most prominent, CMT also condition is not fatal; and with adaptive devices affects sensory perceptions and can cause tingling and environmental modifications, most people and numbness (PARESTHESIA). Characteristic symp- who have CMT can enjoy productive lifestyles. toms of CMT include Risk Factors and Preventive Measures • apparent clumsiness or difficulty walking, run- CMT is nearly always an inherited condition, so ning, and jumping the key risk factor is genetics. GENETIC COUNSELING • progressive weakness in the legs and feet, and can assist couples with FAMILY PLANNING. Early diag- occasionally in the arms and hands nosis and treatment preserves muscle strength and function to the greatest extent possible. High-top • atrophy (wasting) of MUSCLE mass in the shoes and braces to support the ankle extend affected extremities mobility and reduce the risk for ankle injuries • diminished sensory perception in the extremi- such as sprains, strains, and fractures. ties, particularly of heat, cold, and PAIN See also DISABILITY AND EXERCISE; EXERCISE AND • foot drop and heel slap when walking, indica- HEALTH; FRACTURE; GENETIC DISORDERS; INHERITANCE tions of muscle weakness in the lower leg and PATTERN; REFLEX; SPRAINS AND STRAINS. foot Charcot’s joints See NEUROGENIC ARTHROPATHY. The diagnostic path includes a comprehensive NEUROLOGIC EXAMINATION, detailed PERSONAL HEALTH chondritis INFLAMMATION of CARTILAGE that may HISTORY, nerve conduction studies, and elec- occur anywhere in the body though is most com- tromyogram (EMG). The neurologist may also mon in the cartilage of the ribs (costochondritis), perform a nerve biopsy to examine the structure on the ends of the bones (osteochondritis), and of nerve cells in the muscle tissue and GENETIC within the external EAR (auricular chondritis). TESTING for mutations known to cause CMT. The Chondritis often results from trauma, such as a neurologic examination typically shows dimin- blow or, when the external ear is involved, after a ished or absent reflexes at the elbow, knee, and burn injury. Bacterial INFECTION may accompany ACHILLES TENDON. the inflammation. Polychondritis is an autoim- mune disorder in which inflammation affects mul- Treatment Options and Outlook tiple locations of cartilage throughout the body. CMT is a progressive, lifelong condition. Symp- Some rheumatologists believe polychondritis is a toms in CMT1 generally stop short of complete form of VASCULITIS. NONSTEROIDAL ANTI-INFLAMMA- loss of motor function in the affected extremities. TORY DRUGS (NSAIDS) may suppress the inflamma- Other forms of CMT, notably CMT4 and CMTX, tory response. Bacterial infection requires may result in inability to walk. PHYSICAL THERAPY treatment with ANTIBIOTIC MEDICATIONS. However, and daily physical activity—STRENGTH exercise, chondritis may respond slowly to treatment RESISTANCE EXERCISE, and activities to improve bal- because cartilage does not have a BLOOD supply to ance and FLEXIBILITY such as YOGA—can extend carry medications to the site of the inflammation. unassisted mobility. Bicycling and swimming are Heat and rest may provide some relief. excellent activities for AEROBIC EXERCISE as well as See also AUTOIMMUNE DISORDERS; BACTERIA; SYN- for strengthening and flexibility with minimal OVITIS; TENDONITIS. impact on the ankles, which are the most vulnera- ble as CMT progresses. Adaptive devices such as clubfoot See TALIPES EQUINOVARUS. braces, walkers, and wheelchairs can aid mobility when motor function deteriorates to a point that congenital hip dysplasia A condition in which cannot support independent mobility. Some peo- the head of the femur (thigh BONE) does not prop- ple benefit from surgery to rebalance muscles and erly seat in the acetabulum (pelvic socket) at tendons, in particular to provide support for the birth. Numerous potential causes may account for crepitus 319 congenital hip DYSPLASIA, also called congenital hip and sometimes little (third and fourth) fingers displacement or developmental dysplasia of the to draw toward the palm hip. The dysplasia is sometimes apparent at birth; • foot drop, which results from damage to the doctors may suspect it when the delivery presen- muscles and nerves of the lower leg tation is breech because this holds the infant’s hips in a flexed position. Symptoms may include a per- • wrist drop, which results from damage to the ceptible clicking, often felt and heard, when mov- muscles and nerves of the lower arm ing the legs to activate the hip JOINT. Rarely, the • Volksmann’s contracture, which results from leg may be obviously out of alignment with the injury that restricts the flow of BLOOD to the pelvis. X-RAY can often confirm the diagnosis, forearm and hand though some dysplasias may not be detectable until the infant is older. Early symptoms of contracture include diffi- The pediatrician may choose watchful waiting culty straightening a joint and occasionally dis- for a mild dysplasia. A special brace called a Pavlik comfort or PAIN with movement of the joints. harness holds the hips in their proper position in Therapeutic efforts such as gentle stretching and moderate dysplasia, until the connective tissues braces may improve function, though surgery may develop the STRENGTH to hold the femur snugly be necessary to release fibrotic tissue. within the acetabulum. Severe dysplasia or dys- See also ARTHROGRYPOSIS; SCAR; TALIPES EQUINO- plasia that is undetected until the child is walking VARUS. may require closed reduction, in which the ortho- pedic surgeon manipulates the joint into place cramp A painful, involuntary, and often with the child under ANESTHESIA, or open reduc- extended contraction of a MUSCLE. Cramps may tion, in which the orthopedic surgeon makes sur- occur in any muscle and often occur with overuse, gical repairs to the joint. Early and appropriate such as writer’s cramp and leg cramps during run- treatment is important for proper mobility and ning. Overexertion, DEHYDRATION, and fatigue are development of the leg. key contributors to muscle cramps. Uterine cramps See also BIRTH DEFECTS; CONGENITAL ANOMALY; SUR- are common with MENSTRUATION. Gentle stretching GERY BENEFIT AND RISK ASSESSMENT. and massage can relieve the contraction, allowing the muscle to relax. Heat to the area, such as with contracture An abnormal shortening or tighten- menstrual cramps, helps maintain the muscle in a ing of connective tissue or MUSCLE that impedes relaxed state. Stretching before physical exercise proper movement of a JOINT, digit, or other mus- helps prepare the muscles for activity. Adequate culoskeletal structure. Contractures typically hydration helps muscles release toxic byproducts develop when fibrous tissue (scarring), which is into the BLOOD circulation. relatively inflexible, replaces normal connective See also DYSMENORRHEA; SPASM. tissue. This process may reflect autoimmune activ- ity in the body (such as occurs in RHEUMATOID crepitus A cracking, clicking, or snapping sound, ARTHRITIS), repeated trauma (such as occurs in also called crepitation, that occurs with movement REPETITIVE MOTION INJURIES), or a neuromuscular of a JOINT. Crepitus may occur in normal, healthy disorder (such as MUSCULAR DYSTROPHY or CEREBRAL joints though is often quite pronounced in degen- PALSY). Contractures can cause permanent defor- erative joint disorders in which the surfaces of mity of joints, resulting in limited function or joint structures are rough or irregular and protec- movement. tive CARTILAGE structures have deteriorated. Crepi- Common types of contracture include tus is a common feature of TEMPOROMANDIBULAR DISORDERS, PATELLOFEMORAL SYNDROME, fractures due • Dupuytren’s contracture, in which fibrous tis- to trauma, and OSTEOARTHRITIS. sue in the fascia of the hand causes the ring See also FRACTURE; RHEUMATOID ARTHRITIS. D–G dislocations Separations of the structures within Some people experience relief with high doses of a JOINT, typically as a result of traumatic injury. anticholinergic drugs that affect acetylcholine, a The digits (fingers and toes), shoulders, and hips neurotransmitter important to fine motor move- are particularly vulnerable to dislocation. Trau- ments. When the dystonia occurs in a localized or matic dislocation is very painful. Generally a doc- regional part of the body, BOTULINUM THERAPY tor should reduce the dislocation (restore the (injections of weakened botulinum toxin) some- bones to their correct positions) and evaluate the times can paralyze the muscles enough to signifi- injury for any damage that would require addi- cantly reduce or eliminate the dystonia. The tional treatment; however, people tend to “pop” effects of botulinum therapy are temporary, how- dislocations back into place themselves. Such self- ever, with repeat treatments required about every treatment can cause further trauma, depending on six months. the circumstances. Splinting the joint and apply- See also BLEPHAROSPASM; SPASM; TIC; TORTICOLLIS. ing ice to the area can reduce swelling and PAIN until the doctor can realign the structures. Some- epicondylitis INFLAMMATION of the TENDON at the times a dislocation reflects an abnormality of the elbow end of the humerus (long BONE of the upper joint that requires a doctor’s assessment and treat- arm). Epicondylitis may be lateral or medial. Lat- ment to prevent subsequent dislocations. eral epicondylitis, commonly called tennis elbow, See also FRACTURE; RICE; SPRAINS AND STRAINS. affects the outer side of the elbow (little finger side). Bending the wrist back or applying pressure dwarfism See SKELETAL DYSPLASIA. to the bony projection (the humeral epicondyle) on the outside of the elbow causes PAIN at the dystonia Extended contractions of the muscles elbow. Painting and plastering are common occu- that hold the body in unnatural postures. Dysto- pational causes of lateral epicondylitis. Medial epi- nia may occur as a primary disorder of movement, condylitis, commonly called baseball elbow or typically a hereditary disorder, or as an undesired golfer’s elbow, affects the inner side of the elbow SIDE EFFECT of certain medications to treat PARKIN- (thumb side). Bending the wrist toward the palm SON’S DISEASE, PSYCHOSIS, SCHIZOPHRENIA, and SEIZURE of the hand or squeezing a ball held in the palm of DISORDERS that affect DOPAMINE binding in the the hand causes pain at the base of the elbow. BRAIN. Dopamine is a key NEUROTRANSMITTER for The doctor makes the diagnosis on the basis of movement as well as for mood. Sometimes, symptoms and personal history of overuse or a though unfortunately not always, stopping the blow to the elbow. Diagnostic procedures are usu- medication ends DRUG-related dystonia. Inherited ally not necessary. Treatment combines NON- forms of primary dystonia may be spastic (involve STEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS) or rigid, distorted postures) or repetitious, often injections of CORTICOSTEROID MEDICATIONS, which rhythmic, involuntary movements such as gri- reduce inflammation and pain, with alternating maces, twitches, and jerking. heat and cold to the area. A brace or band worn There are no treatments for primary dystonia over the humeral epicondyle provides relief for that are certain to stop the MUSCLE contractions. some people. Epicondylitis generally goes away in 320 fibromyalgia 321

8 to 12 weeks. Recurrent epicondylitis may • fatigue require surgical repair. • gastrointestinal symptoms that suggest IRRITABLE See also OSTEOARTHRITIS; TENDONITIS. BOWEL SYNDROME (IBS), such as frequent NAUSEA and DIARRHEA fascia The fibrous membrane that covers con- • DEPRESSION, anxiety, and mood swings nective tissue. Deep fasciae enclose, support, and separate MUSCLE structures deep within the body. • headaches Superficial fasciae support the SKIN and connect • hypersensitivity to sensory stimulation (sight, the skin to inner layers of tissue. Fascia has high sound, touch, taste, smell) tensile STRENGTH and a sheetlike appearance. It varies in thickness, depending on its location and The diagnostic path begins with a comprehen- purpose. Fasciae throughout the body are suscep- sive medical examination including general BLOOD tible to INFECTION, INFLAMMATION, and traumatic and urine tests, a NEUROLOGIC EXAMINATION, and injury. detailed PERSONAL HEALTH HISTORY. The doctor may See also CONTRACTURE; FIBROMYALGIA NECROTIZING conduct further tests to rule out other conditions FASCIITIS; PLANTAR FASCIITIS. that can cause similar symptoms, such as rheuma- toid arthritis and SYSTEMIC LUPUS ERYTHEMATOSUS fibromyalgia A chronic condition of PAIN felt in (SLE). However, there are no tests that can confirm the muscles and connective tissues throughout the the diagnosis of fibromyalgia. Doctors typically fol- body, with accompanying fatigue and multiple low clinical guidelines for reaching a diagnosis of trigger points (areas on the body where the slight- fibromyalgia that include the presence of these est touch activates a severe pain response). Char- key signs: acteristically people experience a constant level of discomfort with pressure or contact causing overt • diagnostic tests rule out other possible causes pain in the shoulders, chest, back, hips, and knees. for the symptoms Many people also experience stiffness in the areas • point tenderness (discomfort or pain with mild of pain, similar to the stiffness of RHEUMATOID pressure) at a minimum of 11 places on the ARTHRITIS or OSTEOARTHRITIS. However, there is no body JOINT INFLAMMATION or deterioration with fibro- • widespread, persistent aching or pain in the myalgia. Fibromyalgia may persist for months to muscles and joints for at least three months years. About 6 million Americans have fibromyal- gia, the majority of whom are women. The diagnosis also considers factors researchers Researchers believe fibromyalgia develops through believe may be precipitating, such as recent INFEC- a convergence of multiple factors. TION or injury, the existence of any AUTOIMMUNE DISORDERS, and family history of fibromyalgia. Symptoms and Diagnostic Path Symptoms generally begin between ages 30 and The symptoms of fibromyalgia are widely variable, 50. making diagnosis somewhat of a challenge for many people. Some people have periods of weeks Treatment Options and Outlook to months without any symptoms, interlaced with Treatment efforts focus on relieving symptoms to a periods of weeks to months with symptoms severe degree that allows participation in regular activi- enough to prevent normal activity. Other people ties and satisfactory QUALITY OF LIFE with the pre- have a clear path of symptom onset, persistence, sumption that symptoms will persist indefinitely. and improvement that spans months to years. Though the condition may eventually go away, in Characteristic symptoms of fibromyalgia include most people the course of fibromyalgia is unpre- dictable though symptoms do not worsen. Treat- • MUSCLE pain throughout the body ment is a process of finding the combination of • sleep disturbances such as insomnia and REST- approaches that most effectively relieves symp- LESS LEGS SYNDROME toms. Common treatment options include 322 The Musculoskeletal System

• ANALGESIC MEDICATIONS such as acetaminophen health conditions such as OSTEOGENESIS IMPERFECTA, and NONSTEROIDAL ANTI-INFLAMMATORY DRUGS severe OSTEOPOROSIS, or BONE CANCER. Fractures (NSAIDS) to relieve pain may take various forms, including • ANTIDEPRESSANT MEDICATIONS to treat depression • avulsion, in which a small chip of bone breaks and to relieve pain away • MUSCLE RELAXANT MEDICATIONS • closed (simple), in which the bone ends remain • CHIROPRACTIC, OSTEOPATHIC MANIPULATIVE TREAT- relatively in alignment and do not penetrate MENT (OMT), and MASSAGE THERAPY to relax mus- through the SKIN cles and improve range of motion and • comminuted, in which the bone fragments into FLEXIBILITY of joints multiple pieces • ACUPUNCTURE for pain relief and stress reduction • compression, in which the bones collapse onto • YOGA and TAI CHI to improve flexibility, STRENGTH, one another (such as vertebrae in the back) and balance and to relieve stress • greenstick, which typically occur in young chil- • MEDITATION for stress relief dren whose bones are still supple and appear as a bend or curve rather than an outright break Doctors seldom prescribe narcotic pain reliev- in the bone ers, sleep medications, CORTICOSTEROID MEDICATIONS (such as prednisone), or benzodiazepine muscle • open (compound), in which the bone ends are relaxants (such as diazepam), because these treat- significantly separated and protrude through ments interfere with normal activities and are not the skin, causing an open wound proven to improve symptoms long term. As well, • spiral, which occur when sudden force twists the side effects and potential dependency issues the bone and the break runs in line with the with these medications are greater than the short- bone’s axis term benefits for most people. Doctors also recom- • stress, in which hairlike cracks develop in bones mend daily physical exercise because it increases subject to repetitive stress (such as the tibia, the the release of endorphins and enkephalins, the long bone in the lower leg, with running) body’s natural pain relievers. It also stretches and strengthens the muscles and connective tissues, Bone fractures require prompt care from a doc- and promotes a sense of accomplishment and tor. Nearly always it is necessary to immobilize the well-being. bone ends so they remain aligned and can heal back together. Risk Factors and Preventive Measures About 80 percent of people who have fibromyal- Do NOT move a person who may have a gia are women, though researchers do not know fractured neck or back. Summon emer- why this gender correlation exists. People who gency medical aid and keep the person have autoimmune forms of arthritis, such as still, calm, and as comfortable as possi- rheumatoid arthritis or ANKYLOSING SPONDYLITIS, also ble. have increased risk for fibromyalgia. Because researchers do not know what causes fibromyal- Symptoms and Diagnostic Path gia, there are no recommended preventive meas- Severe PAIN and rapid swelling after trauma are ures. the most common symptoms of bone fracture. See also ACUTE PAIN; ALTERNATIVE METHODS FOR Most often, the person cannot bear weight or put PAIN RELIEF; CHRONIC FATIGUE SYNDROME; CHRONIC PAIN; pressure on the involved area. The limb or digit STRESS AND STRESS MANAGEMENT. may appear distorted or a bone end may protrude through the skin. X-RAY nearly always confirms fracture A break in a BONE. The most common the diagnosis, though more sophisticated imaging cause of bone fracture is traumatic injury. Sponta- procedures such as MAGNETIC RESONANCE IMAGING neous fracture may occur in people who have (MRI) and bone scan are occasionally necessary gout 323 to confirm stress fractures and some spiral frac- frozen shoulder See ADHESIVE CAPSULITIS. tures. gangrene The death of tissue (necrosis) resulting Treatment Options and Outlook from deprivation of BLOOD circulation to an area of Treatment immobilizes the bone ends. The most the body. Gangrene most commonly affects the common method of immobilization is a plaster or digits (fingers and toes) and extremities (hands fiberglass cast, applied as a wet wrap around the and feet). FROSTBITE, PERIPHERAL VASCULAR DISEASE fracture and usually spanning the joints above and (PVD), NEPHROPATHY of DIABETES, severe INFECTION below the break in the bone. The cast hardens as (such as clostridial infections and NECROTIZING it dries, and remains in place for three to six FASCIITIS), and RAYNAUD’S SYNDROME are common weeks for most fractures. Other methods of exter- causes of gangrene. TESTICULAR TORSION in which a nal immobilization include splints and braces. TESTICLE becomes strangulated (twisted such that Sometimes the doctor must move the bone its blood supply is cut off) can result in testicular ends into alignment, a procedure called reduction. gangrene. A strangulated HERNIA, which entraps a For most fractures that require reduction, the doc- segment of bowel, can similarly result in intestinal tor first administers a strong sedative or gangrene. Gangrene can also affect internal organs ANESTHESIA, then manipulates the bones. When no that lose their blood supply, such as may occur incision is necessary the reduction is a closed with a major thromboembolism (blood clot in an reduction; when the doctor must open the frac- ARTERY). Gangrene tends to progress as it con- ture site to realign the bones the reduction is an sumes healthy tissue. Gangrenous tissue is charac- open reduction (surgery). During an open reduc- teristically black or greenish black and may have a tion the doctor generally places pins, plates, foul odor. Because the tissue is dead, the person screws, or nails to hold the bone ends in place. has no sensation of PAIN from the area though Fractures set via open reduction generally do not inflamed tissue at the periphery of the gangrenous require casting and the person can return to tissue may cause intense pain. movement as tolerated because the hardware Methods to improve blood circulation, such as holds the bone together. thrombolytic medications to dissolve blood clots Most fractures heal within 6 to 10 weeks. and vasodilator medications to dilate (widen) the Immobilized muscles atrophy (shrink), and the arteries for increased blood flow, may restore person may need PHYSICAL THERAPY to restore MUS- enough circulation to allow the area to heal. Oxy- CLE STRENGTH and JOINT range of motion after the gen delivered under pressure in a hyperbaric doctor removes the cast or other immobilizing chamber is sometimes successful in restoring device. The area of HEALING remains thicker than enough oxygen to the tissues that they can begin the rest of the bone for up to a year. Refracture at to heal. Generally, however, the doctor must sur- the same site is very unlikely. gically remove all gangrenous tissue for HEALING to take place. Such removal may require AMPUTATION Risk Factors and Preventive Measures of the affected digit or limb. Often recovery is then MOTOR VEHICLE ACCIDENTS and athletic or recre- complete, depending on the underlying cause for ational activities that expose a person to impact or the gangrene. People who have diabetes, PVD, or falling present the greatest risk for fractures. Older peripheral neuropathy have increased risk for people are vulnerable to fractures with falls, pri- gangrene to develop in what would otherwise be marily as a consequence of OSTEOPENIA or osteo- minor wounds. porosis (conditions in which the bones become See also INFECTIOUS ARTHRITIS; OSTEOMYELITIS; thin and weak). Proper protective equipment—for PROSTHETIC LIMB. example seat belts, pads, braces, and helmets—can prevent many fractures and other injuries. gout A form of inflammatory arthritis. Gout See also ACCIDENTAL INJURIES; ATHLETIC INJURIES; develops when uric acid crystals form within the CONCUSSION; HIP FRACTURE IN OLDER ADULTS; SPRAINS JOINT capsules, causing irritation and INFLAMMATION. AND STRAINS. Uric acid is a waste byproduct of the METABOLISM of 324 The Musculoskeletal System forms of protein (nucleic acids) called purines. medications do not prevent gout from progressing Purines occur naturally in the body as well as in but can extend the time between attacks as well as meats consumed in the diet (especially organ reduce the permanent damage the inflammation meats such as liver and fish such as mackerel and can cause. herring). The most common site for gout is the first (largest) joint of the big toe. Gout may also FOODS WITH HIGH PURINE CONTENT affect the metatarsal and tarsal joints in the feet as anchovies asparagus bacon well as the ankles and knee; it less commonly beef beer brains involves the fingers and wrists. cod crab duck ham herring kidneys Symptoms and Diagnostic Path lentils liver lobster Gout generally begins with sudden and severe PAIN mackerel mushrooms mussels in the affected joint, usually the first joint of the oysters sardines scallops big toe. The pain commonly arrives at night and shrimp sweetbreads trout wakes the person. The affected joint may be red, turkey veal venison swollen, and warm to the touch. The pain and other symptoms typically go away within 10 days, Risk Factors and Preventive Measures and there can be an extended period before symp- About 20 percent of people who have gout also toms return. The diagnostic path includes X-rays have other family members who have gout, giving of the affected joints and tests of the BLOOD and rise to suspicion of a genetic factor. Circumstances URINE to measure uric acid levels. Sometimes the that increase the amount of uric acid in the blood doctor will numb the joint and use a needle and circulation significantly raise the risk for gout. syringe to withdraw synovial fluid to examine for Such circumstances include consumption of foods the presence of uric acid crystals. As gout pro- high in purines, medications that affect the body’s gresses, often the uric acid crystals also form ability to excrete purines (such as diuretic medica- deposits, called tophi, under the SKIN. tions and immunosuppressive drugs after ORGAN TRANSPLANTATION), DIABETES, HYPERLIPIDEMIA, and Treatment Options and Outlook OBESITY. Excessive ALCOHOL consumption interferes Treatment during a gout attack focuses on reliev- with the ability of the KIDNEYS to filter uric acid ing inflammation and pain. NONSTEROIDAL ANTI- from the blood. Though there do not appear to be INFLAMMATORY DRUGS (NASAIDS) or CORTICOSTEROID effective ways to prevent gout from developing, MEDICATIONS are generally the first line of medica- avoiding circumstances that increase blood uric tions to target these symptoms. Medications to acid levels can reduce the frequency and severity reduce the risk for future gout attacks include of gout attacks. Men are more likely to develop colchicine, allopurinol, and probenecid, which gout before age 50 and women after age 50. slow the body’s production of uric acid. These See also OSTEOARTHRITIS; RHEUMATOID ARTHRITIS. H hernia A separation or tear in the fibers of a the extent to which it allows intestinal structure to MUSCLE that allows the underlying tissue or struc- protrude through the muscle wall. Many abdomi- ture to bulge through. Hernias may occur as a nal hernias are more prominent with coughing or result of congenital weakness or incomplete clo- bearing down. Symptoms of hiatal hernia may sure of a channel in the muscle (such as an umbil- include DYSPEPSIA (heartburn) and difficulty swal- ical or inguinal hernia) or because of injury lowing. Diagnosis is primarily clinical, based on (unintended or surgical). The common types of the appearance of the symptoms. The doctor may hernia are request an ULTRASOUND examination to confirm the presence of the hernia and to create a visual image • inguinal hernia, which occurs in the inguinal to help assess the appropriate therapeutic course. canal (groin) • femoral hernia, which occurs in the upper Treatment Options and Outlook thigh Most hernias require surgery to repair the weak- • umbilical hernia, which occurs at the umbilicus ness in the muscle wall. The doctor may decide to (belly button) take an approach of watchful waiting when the • HIATAL HERNIA, which occurs in the DIAPHRAGM hernia is very small, in a young child, or in a per- and is not visually perceptible son for whom surgery is a significant risk. Nonsur- gical approaches such as a truss (a supportive • incisional hernia, which occurs at the site of a device that places pressure against the hernia to surgical incision, usually abdominal keep it within the abdominal wall) may relieve Hernias present in children often heal as the symptoms for the short term but cannot correct child grows. Hernias in adults are often present the hernia. Though some hernias may remain from childhood and become problematic when small and inconsequential for long periods of time some sort of strain puts pressure on them. Hernias they may become problematic without warning, are somewhat more common in men. When the at which point they may require immediate or person or doctor can push the hernia back into urgent medical attention. An incarcerated hernia the muscle wall it is reducible; an incarcerated is a medical emergency that requires immediate hernia is a hernia that will not recede. When the surgery, otherwise the strangulated tissue dies and hernia traps a segment of intestine or other tissue is at very high risk for GANGRENE. to the extent that it cuts off the BLOOD supply, it is Hernia repair surgery, called herniorrhaphy or a strangulated hernia. Though some hernias, par- hernioplasty, can be OPEN SURGERY (an OPERATION in ticularly in children, may correct themselves, most which the surgeon makes a two- to three-inch- hernias require surgery to repair the defect in the long incision over the site of the hernia and muscle wall. directly exposes the involved muscles) or MINI- MALLY INVASIVE SURGERY (an operation in which the Symptoms and Diagnostic Path surgeon uses a laparoscope and special instru- A hernia may appear as a painless bulge or may ments to operate through one to three small inci- cause discomfort, depending on its location and sions). ANESTHESIA may be regional, epidural, or 325 326 The Musculoskeletal System general. Variables that influence the surgeon’s represent a health condition that requires treat- decision about the type of operation include the ment. However, the situation becomes problem- location and size of the hernia, the person’s age atic when the herniation places pressure against and general health status, and whether the hernia the roots of the SPINAL NERVES or the SPINAL CORD, is reducible or incarcerated. causing PAIN and weakness or numbness in the leg For most hernia repairs the surgeon places a (typically only one leg). Though symptoms may small piece of plastic mesh behind the opening in seem to start suddenly, they reflect processes that the muscle wall to help support the muscle layers. usually have been under way for a considerable The surgeon then sutures those layers together to time. restore stability and STRENGTH to the muscle wall. Recovery takes about two weeks for a laparoscopic Symptoms and Diagnostic Path surgery and up to six weeks for an open surgery. The main symptom of herniated disk is sharp, Once repaired, hernias do not generally recur shooting pain in the low back and in the leg though it is common to feel twinges of discomfort (called radiculopathy). The pain in the leg is more and even PAIN periodically at the site up to several significant for many people, and the leg may feel years after the surgery. weak or numb in certain areas, depending on which spinal NERVE roots the herniation com- Risk Factors and Preventive Measures presses. Some people experience discomfort in Repeated straining, such as with bowel move- both legs, may have difficulty walking, and may ments or because of chronic COUGH, can pressure a have partial or complete loss of bladder or bowel weak place in the abdominal wall. Though sud- function. den, strenuous movement can bring out a hernia, such movement can occur with a strong SNEEZE or Sudden loss of bladder or bowel control cough as easily as lifting too heavy a weight. is a serious symptom that requires Regardless of the activity that bears blame, the immediate evaluation from a doctor. underlying cause of a hernia is a weakness in the muscle structure. Though exercises to improve The diagnostic path begins with a comprehen- muscle strength may prevent injuries such as sive medical examination, including NEUROLOGIC strains and muscle tears, exercises cannot prevent EXAMINATION and detailed PERSONAL HEALTH HISTORY. or treat hernia. There are no known measures for Diagnostic imaging procedures such as X-RAY of preventing hernia. the spine, COMPUTED TOMOGRAPHY (CT) SCAN, MAG- See also SURGERY BENEFIT AND RISK ASSESSMENT; NETIC RESONANCE IMAGING (MRI), and myelography SWALLOWING DISORDERS. (dye injected into the spinal column and viewed with X-ray) often reveal the location and severity herniated nucleus pulposus Damage to the of the herniation. The doctor may also request structure of the CARTILAGE that cushions the verte- nerve conduction studies and electromyogram brae, also called a herniated, slipped, or ruptured (EMG) to assess neuromuscular function. It is pos- disk. A herniated nucleus pulposus becomes sible for diagnostic tests to be unable to pinpoint increasingly common with advancing age, the the precise cause of the symptoms, which does not result of wear and deterioration of the tough outer necessarily rule out herniation. cartilage (called the annulus fibrosus) that allows the soft inner portion of the disk (called the Treatment Options and Outlook nucleus pulposus) to bulge beyond its enclosure. Most doctors prefer, and most people respond to, Often there is a clear tear in the outer cartilage (a conservative, nonsurgical treatment that targets rupture). A traumatic injury, such as a motor relieving the pain and INFLAMMATION. Such an vehicle accident, or heavy lifting may also cause a approach may include disk to herniate. This deterioration and bulging is common • NONSTEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS) enough that doctors believe in itself it does not • heat or cold to the area hip fracture in older adults 327

• limited activity for two to three days to allow tors. Most people recover from an episode of ACUTE the inflammation to subside PAIN with conservative treatment and are able to return to their regular activities. • MUSCLE RELAXANT MEDICATIONS to relieve MUSCLE BACK PAIN CHRONIC PAIN SCIATICA SMOK SPASM See also ; ; ; - ING CESSATION; SURGERY BENEFIT AND RISK ASSESSMENT. • structured, progressive PHYSICAL THERAPY includ- ing strengthening exercises for the back and hip fracture in older adults An injury, often proper techniques for lifting preventable, that often results in significant dis- • gradual return to regular activities ability or premature death. One in four hip frac- tures in adults over age 50 results in limited When pain is severe or does not respond to oral mobility after HEALING; one in four is fatal. Hip medications the doctor may inject the area with a FRACTURE becomes a risk with increasing age for a corticosteroid medication in combination with a combination of factors that include local anesthetic. Such an injection typically pro- vides rapid and direct relief that lasts from several • increasing loss of BONE and MUSCLE mass result- weeks to several months and may be sufficient to ing in decreased STRENGTH and unsteady balance heal the damage to the disk. • slowed reflexes and physical reactions A small percentage of disk herniations continue to cause pain and interfere with normal activities • diminished VISUAL ACUITY after conservative treatment efforts. In such situa- • OSTEOPOROSIS (a condition of thin, weak bones tions, the doctor may recommend LAMINECTOMY, a due to loss of BONE DENSITY) surgical OPERATION to remove the damaged disk. • health conditions such as ALZHEIMER’S DISEASE Health experts strongly encourage a second opin- that impair judgment ion consultation with another doctor who special- izes in treating back conditions before agreeing to • health conditions such as PARKINSON’S DISEASE back surgery. Though successful back surgery both that impair mobility relieves pain and restores function, complications • medication side effects such as drowsiness, are high enough to have earned designation as a dizziness, and orthostatic HYPOTENSION (a sudden health condition themselves: failed back surgery drop in BLOOD PRESSURE that occurs when rising) syndrome (FBSS). Both orthopedic surgeons and neurosurgeons perform surgeries for conditions of Falls, two thirds of which occur in the home, the spine; it is often valuable to have opinions account for 95 percent of hip fractures. Risks from each type of doctor before making a decision include loose rugs on the floor, uneven or slippery about back surgery. walking surfaces, and objects out of place that become obstacles. Though women are more likely Risk Factors and Preventive Measures to fracture a hip in a fall, men are more likely to The key risk factors for herniated nucleus pulpo- die after hip fracture. Hip fracture has such a poor sus are age and sudden stress to the back such as prognosis because recovery requires extended heavy lifting or traumatic injury. Cigarette smok- immobility, which has high risk for complications ing accelerates normal processes of deterioration such as BLOOD clots and PNEUMONIA. Older adults and reduces the flow of BLOOD to the structures of are often reluctant to tell family members or their the spine. Regular physical exercise to strengthen doctors when they fall for fear of losing independ- back muscles and abdominal muscles improves ence. Efforts to reduce the risk for falls are the support for the spine, helping maintain proper most effective measures for preventing hip frac- alignment of the vertebrae to reduce wear and ture. Measures to strengthen bone and muscle, deterioration. Proper lifting methods reduce strain such as daily walking and light RESISTANCE EXERCISE on the back. Though there are no measures to (weightlifting), also help. prevent herniation, such measures help protect See also ACCIDENTAL INJURIES; QUALITY OF LIFE; the spine from injury that exacerbates other fac- REFLEX. I–J

infectious arthritis INFLAMMATION of a JOINT that ment. Joints are particularly vulnerable to injury results from INFECTION. The infectious agent and damage resulting from repetitious motion. (PATHOGEN) may be BACTERIA or mycobacteria or a VIRUS, or fungus and travels to the joint through HEALTH CONDITIONS INVOLVING THE JOINTS the BLOOD circulation. Infectious arthritis, also ADHESIVE CAPSULITIS ANKLE INJURIES called septic arthritis, may also develop as a conse- ANKYLOSING SPONDYLITIS ARTHROGRYPOSIS quence of contamination during surgery on the CONGENITAL HIP DYSPLASIA CONTRACTURE joint. The doctor may withdraw fluid from the DISLOCATIONS EPICONDYLITIS infected joint to examine its cells and determine INFECTIOUS ARTHRITIS KNEE INJURIES the causative pathogen. NEUROGENIC ARTHROPATHY OSTEOARTHRITIS Immediate treatment with the appropriate RHEUMATOID ARTHRITIS SYNOVITIS ANTIBIOTIC MEDICATIONS or ANTIFUNGAL MEDICATIONS is essential to limit damage to the joint. NON- For further discussion of joints within the con- STEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS) are text of the structures and functions of the muscu- effective for relieving inflammation, PAIN, and loskeletal system, please see the overview section FEVER associated with infectious arthritis. Some- “The Musculoskeletal System.” times needle aspiration or surgery is necessary to See also BURSA; JOINT REPLACEMENT; LIGAMENT; drain accumulated pus from the joint. With MUSCLE; OSTEOARTHRITIS; TENDON. prompt and appropriate treatment, most people recover from infectious arthritis with few or no joint replacement A surgical OPERATION, also complications or long-lasting residual effects. called total JOINT replacement, to remove a See also OSTEOARTHRITIS; RHEUMATOID ARTHRITIS; severely diseased or damaged joint and replace it SYNOVITIS; TENDONITIS. with a prosthetic joint. OSTEOARTHRITIS and RHEUMATOID ARTHRITIS are often to blame for joint joint An articulating structure that connects two deterioration severe enough to require joint or more BONE surfaces to allow movement. The replacement. The most commonly replaced joints movement may be slight or the joint fused, such as are hips, knees, and shoulders. Prosthetic joints the sutures in the cranium (skull). A joint may are also available for fingers, elbows, and ankles. function like a hinge, such as the knee and elbow, Prosthetic joints are made of a variety of materials, or like a ball and socket, such as the hip and shoul- usually combinations of metals (such as titanium) der. In the carpal (hand) and tarsal (foot) joints, the and plastic composites (such as polyethylene) that bones glide along each other. Synovial capsules are durable, strong, and light. enclose joints that allow extensive movement between the bone surfaces, such as the knees, hips, Surgical Procedure and shoulders. The synovial membrane produces Joint replacement requires a hospital stay of three synovial fluid, which lubricates the bone ends to seven days. The surgeon performs the operation within the joint to reduce friction between or with the person under general ANESTHESIA. For hip among the structures of the joint during move- or knee replacement, an option is epidural or 328 joint replacement 329 spinal anesthesia with sedation for comfort. A INFECTION of the surgical wound. A particular risk joint replacement operation takes about two with joint replacement is infection that infiltrates hours, during which the surgeon makes an inci- the bone, causing more extensive damage than a sion large enough to adequately expose the joint, repeat joint replacement could repair. Other cuts away the damaged joint structures, prepares potential complications of joint replacement the remaining BONE structure to receive the pros- include failure of the prosthesis, loosening of the thesis, and cements or otherwise attaches the insertion of the prosthesis into the bone ends, DIS- prosthesis components into place. After the sur- LOCATIONS, and loss of function due to wear over geon finishes the operation, the person goes to the time. recovery unit for close nursing supervision and care until the anesthesia wears off and PAIN control Outlook and Lifestyle Modifications is satisfactory, usually for two to four hours. A prosthetic joint has a life expectancy of 5 to 15 Return to activity begins almost immediately years, depending on the joint and the person’s and is essential for full recovery of joint function. lifestyle. Some strenuous physical activities may It is especially important for the person to begin no longer be possible, depending on the replaced walking right away for hip and knee replace- joint. A replacement hip or knee generally cannot ments. The doctor will prescribe ANALGESIC MEDICA- tolerate activities such as running and jumping, TIONS for pain relief. Intensive PHYSICAL THERAPY for example, though swimming and bicycling are moves the new joint through passive and active excellent alternatives for aerobic conditioning and range of motion exercises. Frequent walking also improving STRENGTH, ENDURANCE, and FLEXIBILITY. reduces the risk for blood clots. The doctor may Most people who undergo joint replacement enjoy prescribe medication, support stockings, or inflat- vastly improved QUALITY OF LIFE after HEALING is able compression cuffs. complete. Complete rehabilitation and return to normal activities may take three to six months. Risks and Complications See also PATIENT CONTROLLED ANALGESIA; POSTOPER- All surgeries carry the risk for excessive bleeding ATIVE PROCEDURES; PREOPERATIVE PROCEDURES; PROS- during or after the operation, blood clots, and THETIC LIMB; SURGERY BENEFIT AND RISK ASSESSMENT. K

knee injuries Sprains, strains, CARTILAGE tears, “loose” or may not bear the person’s weight. With and fractures involving the structures of the knee. a moderate to severe injury the person hears and The knee is a hinge JOINT that allows the leg to flex feels a substantial “pop” from the knee, which is (bend back) and straighten, essential actions of the LIGAMENT tearing. Depending on which liga- walking. Unique among hinge joints in the body, ment the injury damages, the knee may feel it the knee also allows a small amount of rotation. wants to bend too far back, extend too far for- The knee is vulnerable to both traumatic and repe- ward, or slip to one side or the other. A significant tition injuries. Knee injury is the leading reason for blow to the side of the knee can cause multiple visits to orthopedic surgeons in the United States. injuries within the knee, rendering the knee use- The knee primarily joins the femur (thigh BONE) less. Hyperextension and dislocated patella present to the tibia (shin bone) and the fibula (small long characteristic appearances that make the diagnosis bone behind the tibia). It also contains the patella obvious. A fractured patella can cause excruciating (kneecap), a small bone that provides added lever- pain and complete inability to use the knee or leg. age for movement of the lower leg. A C-shaped The diagnostic path begins with a detailed thick pad of cartilage, the meniscus, cushions the accounting of the nature of the pain and descrip- ends of the bones from each other. Each knee tion of any precipitating trauma. The doctor will contains two menisci: the medial meniscus, which thoroughly examine both knees. Diagnostic proce- wraps around the inside of tibia, and the lateral dures may include X-RAY, especially if the doctor meniscus, which wraps around the outside of the suspects a FRACTURE, though COMPUTED TOMOGRAPHY tibia. Strong ligaments bind the knee from each (CT) SCAN or MAGNETIC RESONANCE IMAGING (MRI) typi- side and the center, holding the bones in place. cally yield more information about the nature and The most damaging traumatic injuries to the extent of soft tissue injuries such as are most com- knee are those that result from a blow or fall that mon in the knee. Diagnostic ARTHROSCOPY, a MINI- rapidly stretches the ligaments and causes them to MALLY INVASIVE SURGERY, may be necessary to fully tear (ligament sprain). Sudden twisting motions in assess the damage and has the advantage of allow- which the foot plants but the rest of the leg con- ing the surgeon to immediately repair the injury. tinues to move also expose the knee to such injury. The knee takes considerable pounding in Treatment Options and Outlook the course of everyday activities that subject it to Ice to the knee and restricting movement are the repeated impact (such as occurs with walking, most effective immediate treatments for traumatic running, and jumping). Repetition or “wear and injury. Prompt icing can reduce INFLAMMATION and tear” injuries of the knee include OSTEOARTHRITIS swelling to minimize the severity of the injury. and PATELLOFEMORAL SYNDROME. Suspected patella fracture or severe sprain requires immobilization to prevent further dam- Symptoms and Diagnostic Path age. Many knee injuries heal with conservative, PAIN and swelling are symptoms common to many nonsurgical treatment approaches. The doctor kinds of knee injuries. Damage to ligaments and may recommend a knee wrap or brace, depending menisci often result in an unstable knee that feels on the injury. NONSTEROIDAL ANTI-INFLAMMATORY 330 knee injuries 331

COMMON KNEE INJURIES Injury Common Causes Key Symptoms anterior cruciate LIGAMENT (ACL) sudden twisting of the knee or blow to the pop or snap felt and heard sprain front of the knee swelling mild PAIN “loose” feeling to knee inability to bear weight on the leg hyperextension direct blow to the front of the knee pain with hyperextension soreness after knee returns to normal extension lateral collateral ligament (LCL) impact to the inside of the knee pain sprain pop or snap felt and heard knee buckles to the outside medial collateral ligament (MCL) impact to the outside of the knee pain sprain pop or snap felt and heard knee buckles to the inside meniscus tear sudden rotation of the upper body with the pain foot planted clicking or locking within the knee instability of the knee patella DISLOCATION impact to the side of the patella pain fall that jars the side of the patella patella obviously out of position, usually to the side of the knee inability to bend the knee patella FRACTURE sharp blow to the patella severe pain and swelling inability to move the knee or bear weight on the leg patellar TENDON rupture stumbling in an attempt to avoid a fall pain landing after a jump from considerable height tenderness to touch at point of rupture difficulty bending or extending the lower leg displaced patella

PATELLOFEMORAL SYNDROME long-term repetitious movement of the knees pain with bending or extending the knee such as with running and bicycling poor conditioning posterior cruciate ligament (PCL) impact or blow to the front of the knee pop or snap felt and heard sprain swelling mild pain “loose” feeling to knee inability to bear weight on the leg 332 The Musculoskeletal System

STAGE SCALE: LIGAMENT SPRAIN OR TEAR Grade Extent of Injury or Damage Symptoms grade 1 or first degree minor stretching of LIGAMENT fibers though mild PAIN with pressure to the knee knee remains stable mild swelling grade 2 or second degree moderate tear of the ligament with some moderate pain with pressure to the knee instability of the knee moderate swelling grade 3 or third degree complete tear of the ligament and its nerves; little if any pain with pressure to the knee unstable knee pronounced pop felt and heard at time of injury inability to bear weight or use the knee

DRUGS (NSAIDS) relieve inflammation and pain for EXERCISE can strengthen these muscles. YOGA is both traumatic and overuse injuries. Gentle excellent for improving FLEXIBILITY as well as stabil- stretching and exercise such as walking help keep ity of the knees. Knee supports, braces, and pro- the knee flexible and facilitate HEALING. tective pads reduce the risk of knee injury in some Mild to moderate ligament sprains often heal sports. Proper technique and adequate physical without surgery in four to six weeks. Severe liga- conditioning are crucial elements of injury pre- ment sprains and meniscal tears often require sur- vention for any athletic activity. Other preventive gery to repair. Orthopedic surgeons can perform measures include stretching and WARM-UP before nearly all such operations arthroscopically, which and after participating in vigorous exercise or allows minimal recovery time. PHYSICAL THERAPY sports events. facilitates rehabilitation after surgery and most See also ANKLE INJURIES; ATHLETIC INJURIES; people able to return to regular activities in about OSGOOD-SCHLATTER DISEASE; STRENGTH; WALKING FOR six months. Return to sports may require more FITNESS. time, especially for activities of high vulnerability for knee injury such as football, soccer, downhill kyphosis A deformity of the upper spine that skiing, and basketball. gives the appearance of a hump in the upper back. Kyphosis may represent a CONGENITAL ANOMALY in Risk Factors and Preventive Measures the structure of the spine or may develop later in Contact sports (such as football) and other sports life as a consequence of damage to the CARTILAGE that involve running, twisting, and jumping (such disks between the vertebrae that allow the verte- as soccer, basketball, and tennis) expose the knee brae to slide out of position. Mild kyphosis gener- to direct blows with great risk for injury. Any ally does not cause symptoms and may be sport that uses cleats to improve traction (such as noticeable only with X-rays of the spine. Moderate track, soccer, and football) has increased risk for kyphosis can cause upper BACK PAIN, resulting from knee injury resulting from excessive torsion distorted posture that strains the back muscles. (twisting under pressure). Sports and athletic Treatment may include PHYSICAL THERAPY or CHIRO- activities account for the majority of knee injuries PRACTIC care to stretch the back, strengthen mus- in people under age 25. By midlife, repetitive cles, and improve posture. Sometimes sleeping on trauma (such as results from running) begins to a very firm mattress with a low pillow allows the take its toll and overuse injuries become more spine to correct itself. The doctor may prescribe a common. Excessive body weight further stresses back brace for moderate kyphosis. Severe kyphosis the knees. may require surgery to realign and support the Strong thigh muscles—the quadriceps in the vertebrae. front and the hamstrings in the back—improve See also ACHONDROPLASIA; LORDOSIS; OSTEOPORO- stability of the knee. Weight-lifting or RESISTANCE SIS; SCOLIOSIS; X-RAY. L

laminectomy A surgical OPERATION to remove a further damage may occur to the same vertebra or segment of vertebra (BONE of the spine) to relieve other vertebrae. About 70 percent of people experi- pressure against the SPINAL CORD or a spinal NERVE ence full relief from their symptoms and return to root. Laminectomy treats neurologic symptoms work and recreational activities without restriction. arising from HERNIATED NUCLEUS PULPOSUS (herniated See also BACK PAIN; SCIATICA; SPINAL NERVES; SUR- or slipped disk), CERVICAL SPONDYLOSIS, and SPINAL GERY BENEFIT AND RISK ASSESSMENT. STENOSIS. When laminectomy is the appropriate therapeutic choice, it has a fairly high success rate ligament A cordlike structure of tough connec- for relieving symptoms (such as PAIN, weakness, tive tissue that binds bones together at joints. Lig- and numbness in the leg) and allowing the person aments are vulnerable to injury from stretching, to return to regular activities. However, it is which can cause them to tear. Such a ligament important to first consider all other therapeutic injury is a sprain. Most sprains heal with conser- options as the rate of success for back surgery is vative treatment, though some (notably complete highly variable. tears) require surgery to repair them. Ligaments Laminectomy is an OPEN SURGERY on the back may also join or support organs and structures performed under general ANESTHESIA. An orthope- other than bone, such as the round ligaments in dic surgeon or a neurosurgeon may perform the the pelvis that suspend the UTERUS within the operation. The surgeon makes a long incision (five abdominal cavity. to seven inches) along the spine at the site of the See also BONE; JOINT; MUSCLE; SPRAINS AND STRAINS; impingement; separates the soft tissue structures TENDON. from the vertebra to expose the bone; and removes a lamina, one of the flat segments of the lipoma A benign (noncancerous) soft tissue vertebral arch. Depending on the cause of the tumor. Lipoma is the most common type of tumor. impingement and the overall health of the verte- It arises from adipocytes—fat cells—though can brae (whether there is progressive deterioration develop in any kind of tissue. Lipomas are particu- such as is common with spinal stenosis), the sur- larly common in the MUSCLE, appearing as a small geon may choose also to fuse the operated verte- painless lump. A lipoma near the surface of the bra to an adjacent healthy vertebra for stability. SKIN feels soft and fairly well defined. Lipoma does Most people stay in the hospital up to three days not hurt or become cancerous and requires no after the operation. Recuperation and return to treatment unless it becomes larger than five cen- normal activities takes six to eight weeks. timeters. Large lipomas may be cosmetically unac- The risks of laminectomy include excessive ceptable or cause irritation to the surrounding bleeding during surgery, postoperative INFECTION, tissue. The doctor may choose to biopsy or remove continued symptoms after HEALING, and sensory dis- a lipoma that occurs in the BREAST or COLON, to be turbances resulting from surgical injury to the certain of the diagnosis as other kinds of breast spinal nerve root. When the cause of the nerve and colon tumors may be malignant (cancerous). compression was deterioration of the vertebra due Lipomas have a tendency to recur after surgery to to a progressive condition such as OSTEOARTHRITIS, remove them. 333 334 The Musculoskeletal System

See also ADENOMA; BREAST CANCER; COLORECTAL ACHONDROPLASIA and other forms of SKELETAL DYS- CANCER; SURGERY BENEFIT AND RISK ASSESSMENT. PLASIA. Lordosis does not usually cause symptoms lordosis An abnormally exaggerated inward cur- other than its appearance. Sometimes lordosis vature of the lumbar spine at the small of the results from habitual poor posture. X-RAY is usu- back, giving the appearance of protruding but- ally sufficient to confirm the diagnosis. Treatment tocks in the back and protruding belly in the front. attempts to prevent progression of the curvature Lordosis may result from congenital abnormalities as well as to correct the existing deformity to of the spine and often develops when a child retain spinal stability for support of the axial begins to walk. CONGENITAL HIP DYSPLASIA, CEREBRAL SKELETON. However, most lordosis in otherwise PALSY, SPINA BIFIDA, and neuromuscular disorders in healthy children corrects itself as the child grows. which the muscles are weak are common congen- See also CONGENITAL ANOMALY; KYPHOSIS; SCOLIOSIS; ital causes for lordosis. Lordosis is also common in SURGERY BENEFIT AND RISK ASSESSMENT. M–N

Marfan syndrome A genetic disorder arising festation of this aspect of Marfan syndrome. To from mutations in the fbn1 GENE that affect the compensate, the heart intensifies the STRENGTH and structure of connective tissues throughout the frequency of its contractions, which over time body. The fbn1 gene encodes for fibrillin 1, a pro- enlarges the heart (CARDIOMYOPATHY). tein molecule essential for the formation of There are no definitive diagnostic tests for Mar- elastin. Elastin is the basis of the fibers that form fan syndrome, and symptoms are sometimes mild the connective tissues. In Marfan syndrome the enough to escape detection until midlife or later elastin is too soft, allowing connective tissues to when cardiovascular problems begin to emerge. stretch more than normal. The INHERITANCE PATTERN An accumulation of symptoms points to the diag- for Marfan syndrome is autosomal dominant, nosis, particularly if there is a family history of meaning one parent who has the mutated gene Marfan syndrome. The doctor may conduct can pass the condition to his or her children. Mar- GENETIC TESTING for the fbn1 gene MUTATION to con- fan syndrome primarily affects the cardiovascular firm the diagnosis. system, musculoskeletal system, and eyes. Treatment Options and Outlook Symptoms and Diagnostic Path Treatment focuses on early detection of and ther- Marfan syndrome produces hallmark physical apy for potential complications, notably CARDIO- characteristics that include VASCULAR DISEASE (CVD). Doctors advise against activities, especially competitive sports, that cause • tall, lanky frame with extraordinarily long arms rapid and extreme changes in BLOOD PRESSURE and • elongated, narrow face HEART RATE. Treatment may include medications to maintain low blood pressure and heart rate as pre- • crowded TEETH ventive measures. Most people who have Marfan • narrow, sunken chest syndrome should have an ECHOCARDIOGRAM (ULTRA- • long, thin fingers SOUND examination of the heart) annually to screen for changes in the heart’s size and valve Many people who have Marfan syndrome have function and the stability of the aorta. Early sur- severe MYOPIA (nearsightedness) and abnormalities gery to intervene when echocardiogram suggests a of the CORNEA. Within the body, one of the most dissecting aortal aneurysm can be lifesaving. significant effects of Marfan syndrome is on the major BLOOD vessels, notably the AORTA, and the Risk Factors and Preventive Measures HEART valves. Because the connective tissue within Because cardiovascular complications of Marfan the walls of the arteries is softer than it should be, syndrome can be severe or life threatening, doc- the walls of the arteries are susceptible to separa- tors recommend GENETIC COUNSELING for people tion (ANEURYSM). As well, the heart valves are who have the disease. Marfan disease is preventa- often larger than normal and do not close prop- ble only by preventing transmission of the erly, allowing blood to backflow within the heart. mutated bfn1 gene. For the 30 percent or so of Mitral valve prolapse is the most common mani- people in whom the mutation is spontaneous 335 336 The Musculoskeletal System

(occurs without apparent family history of the cialized form of muscle called myocardial, also condition), there are no measures of prevention. under control of the autonomic nervous system. See also GENETIC DISORDERS. The bulk of the muscle tissue in the body is skele- tal (striated) muscle, which responds to voluntary meniscectomy A surgical OPERATION to remove control through the CENTRAL NERVOUS SYSTEM. part or all of a damaged meniscus in the knee. The skeletal muscles are responsible for move- Each knee has two menisci, C-shaped pads of CAR- ment and account for about 40 percent of the TILAGE that cushion the ends of the femur (thigh body’s mass. They generally appear in opposing BONE) and tibia (shin bone) as they come together pairs attached to BONE via tendons. When one within the knee JOINT. Meniscus tears are common muscle contracts, its opposing muscle relaxes. This ATHLETIC INJURIES and occur when there is torsion allows smooth, balanced movement. The SKELETON under pressure—the body above the knee twists provides resistance and leverage for the muscles as suddenly during movement but the foot remains they contract and relax. The body contains about planted. Most of the time the orthopedic surgeon 650 muscles, the largest of which is the gluteus can perform a partial meniscectomy with maximus (main muscle of the buttocks) and the ARTHROSCOPY (MINIMALLY INVASIVE SURGERY using a smallest of which is the stapedius in the middle specialized endoscope), which allows rapid recov- EAR (moves the stapes bone). ery and return to regular activities. Movement requires interaction between neu- Cartilage, which is very dense, does not have its rons (NERVE cells) and muscle fibers. This interac- own BLOOD supply but rather draws necessary tion occurs at the neuromuscular junction, a NUTRIENTS from surrounding tissues and fluids. Tears synapse where the NEURON’s axons end (terminate) near the outer edge of the meniscus are more likely and the muscle fiber begins. When conveying a to heal than tears in the center of the meniscus. The nerve impulse to activate a skeletal muscle fiber, surgeon may attempt to repair an outer tear though the motor neuron releases a molecule of acetyl- will likely need to remove the damaged segments choline, a NEUROTRANSMITTER. The acetylcholine of meniscus when the tear is interior. The goal is to molecule binds with an acetylcholine receptor on remove as little of the meniscus as possible because the muscle fiber, forming a biochemical bridge without it the bone ends loose protection. It is that allows the nerve impulse to travel from the equally important to remove any pieces of the neuron to the muscle fiber. The impulse creates an meniscus that are torn or fragmented to prevent action potential in the muscle fiber—a cycle of them from “jamming” the joint. activation, discharge, and recovery—that becomes The risks of meniscectomy include excessive a muscle contraction. bleeding during surgery and postoperative INFEC- Skeletal muscles contain two types of fiber that TION, both of which are rare. Full recovery after dictate how rapidly and with what intensity they arthroscopic surgery takes about six weeks and complete an action potential. Type 1 fibers, also after OPEN SURGERY may take up to six months. called slow-twitch or red fibers (red because they Even after HEALING, complete meniscectomy may have a high myoglobin content), have a slow and limit some athletic activities that place significant steady response. Type 1 fibers are in a constant stress on the knee, such as downhill skiing. state of partial contraction; they provide muscle See also KNEE INJURIES; PHYSICAL THERAPY; SURGERY tone and are essential for maintaining the body’s BENEFIT AND RISK ASSESSMENT. posture. Type 2 fibers, also called fast-twitch or white fibers (white because they contain very lit- muscle Contractile fibers or the structures these tle myoglobin), have a rapid response. Type 2 fibers form. Muscles move the body, some under fibers are responsible for muscle STRENGTH. Most voluntary control and others reflexively. The gas- skeletal muscles contain a combination of type 1 trointestinal tract, genitourinary tract, and BLOOD and type 2 fibers. Exercise to extend ENDURANCE vessels contain smooth (nonstriated) muscle, increases the percentage of type 1 fibers; exercise which is under involuntary control of the auto- to improve strength increases the percentage of nomic NERVOUS SYSTEM. The HEART contains a spe- type 2 fibers. muscular dystrophy 337

For further discussion of muscle within the dystrophin, which is essential for skeletal (stri- context of the structures and functions of the ated) muscle cell integrity and function. Without musculoskeletal system, please see the overview it the skeletal muscles deteriorate and movement section “The Musculoskeletal System.” becomes difficult or impossible. About 50,000 See also CELL STRUCTURE AND FUNCTION; FASCIA; Americans have muscular dystrophy. The three LIGAMENT; PROPRIOCEPTION; TENDON. most common of the nine major types of muscular dystrophy are Duchenne’s muscular dystrophy, muscle relaxant medications Medications that facioscapulohumeral muscular dystrophy, and relieve MUSCLE spasms, cramps, and stiffness. Some myotonic muscular dystrophy. muscle relaxants are also called antispasmodic Duchenne’s muscular dystrophy Duchenne’s is medications. Doctors may prescribe these medica- an X-linked recessive MUTATION affecting the dys- tions to treat acute BACK PAIN, acute sprains, severe trophin GENE. As such, it nearly exclusively affects muscle tension HEADACHE, and muscle spasticity boys. Symptoms begin to appear in early child- due to conditions such as CEREBRAL PALSY, MULTIPLE hood with characteristic postures and gait. Pro- SCLEROSIS, SPINAL CORD INJURY, MUSCULAR DYSTROPHY, gression is steady, and most boys who have FIBROMYALGIA, and many others. There are various Duchenne’s lose the ability to walk by about age types of muscle relaxant medications that work 12. The skeletal muscles of the upper chest through different mechanisms, though all act on become involved in ADOLESCENCE, affecting BREATH- the CENTRAL NERVOUS SYSTEM rather than on the ING. Duchenne’s is usually fatal before age 20. muscles directly. Because of this, most muscle A milder presentation of similar symptoms and relaxants also affect alertness, balance, and other pattern of progression with a later age of onset neurologic functions. (late childhood or early adolescence) is Becker’s As with any medication, muscle relaxants can muscular dystrophy. Though the course of the dis- have adverse side effects and interact with other ease is ultimately fatal, most who have it live into drugs, including OVER-THE-COUNTER (OTC) DRUGS and their 30s. Treatment is primarily supportive, with herbal remedies. Typically muscle relaxants pro- PHYSICAL THERAPY to help preserve muscle STRENGTH vide short-term relief during acute injury. Once and function. CORTICOSTEROID MEDICATIONS may muscle fibers begin to heal, they return to normal improve symptoms. contraction and relaxation patterns and muscle Facioscapulohumeral muscular dystrophy An relaxant medications are no longer necessary or adult-onset type of muscular dystrophy, facio- helpful for recovery. Muscle relaxants in the ben- scapulohumeral muscular dystrophy affects men zodiazepine family of drugs (such as diazepam) and women equally. Symptoms first appear as cause significant drowsiness and can become habit weakness in the muscles of the face and shoulder forming; doctors generally prescribe them spar- girdle (upper arms and shoulders). The shoulders ingly because of these risks. often “wing” outward. Over the course of the dis- ease, muscle weakness moves downward through COMMON MUSCLE RELAXANT MEDICATIONS the body though the lower arms are usually the carisoprodol chlorzoxazone last affected. Symptoms are mild enough in about cyclobenzaprine diazepam half of those who have this form of muscular dys- metaxalone methocarbamol trophy to permit fairly normal function and mobility throughout life. In others, symptoms may See also ADVERSE REACTION; CRAMP; DRUG INTERAC- affect swallowing and mobility. TION; MEDICINAL HERBS AND BOTANICALS; PHYSICAL Myotonic muscular dystrophy In myotonic mus- THERAPY; SPRAINS AND STRAINS; SPASM. cular dystrophy the muscles lose the ability to relax after contraction, causing them to become stiff. muscular dystrophy The collective term for a Myotonic muscular dystrophy is the most common group of GENETIC DISORDERS of the MUSCLE resulting type of adult-onset muscular dystrophy and affects in progressive weakness. Most types of muscular men and women equally. The cause is a mutation dystrophy arise from a deficiency of the protein in the gene that encodes for myotonica protein 338 The Musculoskeletal System

MAJOR TYPES OF MUSCULAR DYSTROPHY Type of Muscular Dystrophy Key Characteristics Inheritance Pattern Duchenne’s most common type X-linked recessive affects primarily muscles of the upper arms, upper legs, and pelvic girdle first symptoms usually appear between ages 2 and 6 myotonic affects primarily muscles of the face and neck, hands, and feet autosomal dominant gastrointestinal, cardiac, EYE, neurologic, and endocrine involvement later in the disease first symptoms appear in adulthood

Becker’s affects primarily muscles of the upper arms, upper legs, and X-linked recessive pelvic girdle very similar to Duchenne’s with milder symptoms symptoms begin in late childhood or early ADOLESCENCE limb-girdle affects primarily the muscles of the pelvic girdle and shoulder autosomal recessive or girdle autosomal dominant symptoms begin in late adolescence or early adulthood facioscapulohumeral affects primarily the muscles of the face, neck, and shoulders autosomal dominant symptoms begin in late adolescence or early adulthood congenital affects all skeletal muscles autosomal recessive often affects the CENTRAL NERVOUS SYSTEM, causing seizures symptoms are present at birth oculopharyngeal affects the muscles of the eyelids and THROAT autosomal dominant symptoms begin in middle to late adulthood distal affects the forearms, hands, lower legs, and feet autosomal recessive or symptoms begin in adulthood autosomal dominant

Emery-Dreifuss affects primarily the shoulders, upper arms, pelvis, and lower X-linked recessive legs symptoms typically appear first as contractures, then weakness symptoms begin in late childhood or early adolescence

kinase. Other gene mutations may also contribute. of posture and gait (walking style). The diagnostic Though progression is usually slow, myotonic mus- path begins with detailed PERSONAL HEALTH HISTORY cular dystrophy affects other body systems as well. and family health history. Because muscular dys- Cataracts and diabetes are common. trophies are inherited disorders, the family health history is particularly important. A comprehensive Symptoms and Diagnostic Path NEUROLOGIC EXAMINATION identifies the specific In most forms of muscular dystrophy, the primary symptoms, which helps narrow the diagnosis. symptoms are muscle weakness and disturbances BLOOD tests may show excessive proteins that indi- myopathy 339 cate muscle destruction. Each type of muscular neuron releases often dissipates before a receptor dystrophy has fairly characteristic patterns of becomes available. As a result, muscle contrac- symptoms. Muscle biopsy shows damage to the tions are weak. Muscles that have the fewest muscle cells. numbers of acetylcholine receptors to begin with—the muscles of the eyelids, eyes, face, Treatment Options and Outlook MOUTH, and THROAT—are the most dramatically Treatment for all types of muscular dystrophy is affected. Muscle function worsens during activity primarily supportive. Physical therapy, braces, that uses affected muscles, such as chewing or orthotics, and mobility aids extend the ability to talking, and improves after rest. walk and function independently. Corticosteroid Myasthenia gravis may develop at any age medications slow the progression of symptoms in though is most common in women under age 40 some types of muscular dystrophy, notably and men over age 60. Researchers do not know Duchenne’s. Though all types of muscular dystro- what causes myasthenia gravis but suspect a dys- phy are lifelong, muscular dystrophy is not neces- function of the THYMUS, a structure of the immune sarily fatal. Many people with milder types of the system responsible for the maturation of T-cell disease live normal life expectancy with relative lymphocytes, may play a significant role. The thy- independence. mus, which normally has little function in adults, is abnormally active in people who have myasthe- Risk Factors and Preventive Measures nia gravis. Symptoms of myasthenia gravis relate Muscular dystrophy is always inherited, so the key to the muscles affected and may include difficulty risk factor is family history. People who have mus- focusing the eyes, slurred speech, or difficulty cular dystrophy or family history of muscular dys- swallowing. Involvement of peripheral muscles trophy should consider GENETIC COUNSELING to aid may result in balance and gait dysfunctions. in FAMILY PLANNING decisions. There are no meas- Because myasthenia gravis is relatively rare, ures known to prevent muscular dystrophy, doctors typically explore more common causes for though research holds hope for GENE THERAPY that weak muscles before looking specifically for myas- can someday correct the mutations that cause the thenia gravis. BLOOD tests can detect the presence of disease. the acetylcholine receptor antibodies in most peo- See also CATARACT; MYOPATHY. ple who have myasthenia gravis. Other diagnostic procedures that point to the disorder include spe- myasthenia gravis A rare autoimmune disorder cialized electromyogram (EMG) and tests that in which the IMMUNE SYSTEM produces antibodies measure the muscle’s response to acetylcholine. that target acetylcholine receptors on the cell Treatment includes anticholinesterase medica- membrane surfaces of MUSCLE cells. Acetylcholine tions, which block the action of cholinesterase, an is a NEUROTRANSMITTER that carries NERVE impulses enzyme that breaks down acetylcholine, and from neurons to muscle cells to initiate move- IMMUNOSUPPRESSIVE MEDICATIONS, which interfere ment. Acetylcholine receptors are specialized mol- with the release of antibodies to slow the destruc- ecules that bind acetylcholine molecules, a process tion of acetylcholine receptors. Many people expe- analogous to plugging an electrical cord into an rience significant improvement in their symptoms outlet. The NEURON releases acetylcholine to carry after THYMECTOMY (a surgical OPERATION to remove the impulse across the synapsis to the muscle cell. the thymus). Most people who have myasthenia Binding forms a complete circuit and the nerve gravis are able to enjoy relatively normal lives impulse passes from the neuron to the muscle cell. with appropriate treatment. The antibodies present in myasthenia gravis See also ANTIBODY; AUTOIMMUNE DISORDERS; attack and destroy acetylcholine receptors, reduc- IMMUNE RESPONSE; LYMPHOCYTE; SURGERY BENEFIT AND ing the ability of acetylcholine to carry to comple- RISK ASSESSMENT; T-CELL LYMPHOCYTE. tion the nerve impulses that direct movement. Because there are fewer acetylcholine receptors in myopathy MUSCLE weakness that occurs when myasthenia gravis, the acetylcholine molecule the muscle cells do not function properly. There are 340 The Musculoskeletal System numerous forms of myopathy, many of which are der often improves when the underlying condi- congenital (present at birth) or genetic (the result tion improves. Though myotonia is a lifelong cir- of inherited GENE mutations). Some myopathies cumstance, most people who have myotonia are are progressive (become worse with time) and able to enjoy fairly normal lifestyles with appro- others remain stable. Metabolic disorders, HIV/AIDS, priate medication therapy. IMMUNE DISORDERS, and ADVERSE REACTION to drugs See also CELL STRUCTURE AND FUNCTION; GENETIC (including ALCOHOL) may cause myopathies. Treat- DISORDERS; INHERITANCE PATTERN; MUTATION; MYOPATHY; ment targets the cause of the myopathy in NEURON. acquired myopathy and attempts to relieve symp- toms when myopathy is congenital or genetic. neurogenic arthropathy Degeneration of a JOINT, Treatment approaches may include medications, commonly the knee, as a consequence of NEUROPA- PHYSICAL THERAPY, braces or other devices to sup- THY (impaired NERVE function) that causes loss of port weak muscle structures and aid mobility, and sensation. Injuries occur to the affected joint MASSAGE THERAPY. because there is limited perception of PAIN or sense See also CARDIOMYOPATHY; GENETIC DISORDERS; of the joint’s position relative to the body and its INHERITANCE PATTERN; MITOCHONDRIAL DISORDERS; immediate environment (PROPRIOCEPTION). Neuro- MUTATION; NEUROPATHY; POLYMYOSITIS. genic arthropathy sometimes called Charcot’s joints, often includes unrecognized fractures that myotonia A neuromuscular circumstance in do not heal properly because the joint is in contin- which the muscles contract properly but do not uous motion. As a result the joint becomes relax, causing temporary stiffness. Movement may deformed and dysfunctional, changes that cause be slow and difficult until the muscles warm up, only mild discomfort because of the underlying after which they seem to function more smoothly. NEUROPATHY. Myotonia may be a symptom, such as with some The diagnostic path begins with recognition of forms of MUSCULAR DYSTROPHY, or a congenital con- the underlying neuropathy. X-RAY can usually dition. Myotonia congenita is a rare form of confirm the damage to the joint. Treatment for myotonia that occurs as a result of GENE muta- neurogenic arthropathy aims to preserve joint tions. Some forms of myotonia are progressive structure and function to the extent possible and though most are not. Myotonia is a disorder of the may include BONE graft or surgery to stabilize the ion channels in the MUSCLE cells (channelopathy), joint. Some people are good candidates for JOINT most often the chloride, sodium, or potassium REPLACEMENT, though in progressive forms of neu- channels. The ion channels regulate the ion rogenic arthropathy the joint may continue to exchange that must occur for a cell to “fire,” deteriorate around the prosthesis. which in the case of muscle cells is to contract and relax. CONDITIONS ASSOCIATED The diagnosis of myotonia is primarily clinical, WITH NEUROGENIC ARTHROPATHY based on the doctor’s observance of the person’s AMYLOIDOSIS CHARCOT-MARIE-TOOTH (CMT) DISEASE movement and muscle function. Characteristic DIABETES Hansen’s disease (leprosy) alterations in the electromyogram (EMG) gener- SPINA BIFIDA SPINAL CORD INJURY ally can confirm the diagnosis. Treatment with antiseizure medications and drugs that affect the See also CHARCOT-MARIE-TOOTH (CMT) DISEASE; ion channels often improve symptoms and muscle FRACTURE; INFECTIOUS ARTHRITIS; OSTEOARTHRITIS; function. Myotonia resulting from another disor- RHEUMATOID ARTHRITIS. O

occupational therapy A therapeutic approach to lump and PAIN in the area of the knee. Pain is teach people the skills they need for living as inde- often more intense when going up and down pendently as possible with long-term injury or dis- steps, running, and jumping. Osgood-Schlatter ability. Occupational therapy focuses on disease tends to affect girls at a younger age (10 to techniques and devices to make easier the activi- 12 years) than it affects boys (12 to 14 years). The ties and events of daily living, aiding with such doctor bases the diagnosis on the presentation of circumstances as recovery after STROKE, develop- symptoms and the findings on X-RAY studies. The mental disability in children, and rehabilitation doctor may also conduct a bone scan when the X- after serious injury or surgery. The doctor may ray findings are unclear. However, diagnosis is also recommend occupational therapy for people usually straightforward. who have neuromuscular disorders, MYOPATHY, Osgood-Schlatter disease is self-limiting; it goes NEUROPATHY, and CHRONIC PAIN syndromes. Occupa- away when growth in the tibia ceases. Ice to the tional therapists also conduct home visits to rec- area and NONSTEROIDAL ANTI-INFLAMMATORY DRUGS ommend environmental adaptations to reduce the (NSAIDS) to relieve INFLAMMATION and pain are gen- risk of falls as well as to accommodate factors such erally sufficient treatment. A physical therapist or as wheelchair accessibility. In the United States sports medicine specialist can teach the child occupational therapy services require a prescrip- stretching exercises for the quadriceps and for the tion from a doctor. hamstrings, in the back of the thigh, to reduce See also PHYSICAL THERAPY; QUALITY OF LIFE. pressure against the patellar tendon. See also ATHLETIC INJURIES; PHYSICAL THERAPY. Osgood-Schlatter disease A disorder of the epi- physis (growth plate) of the tibia, the long BONE in osteoarthritis A condition of progressive degen- the lower leg (shin bone) that typically develops in eration of the joints. Osteoarthritis tends to athletically active adolescents. ADOLESCENCE is the develop in adults age 60 and older and to affect period during which growth of the long bones is joints subject to excessive stress throughout life, very rapid. The patellar TENDON stretches across the often in occupational settings. Recreational and head of the tibia to attach at the top of the tibial athletic activities may also result in osteoarthritis. tubercle. Athletic activities that extensively use the The fingers, cervical spine (neck), knees, hips, and quadriceps MUSCLE in the thigh, such as basketball, lumbar spine (low back) are most commonly place considerable pressure on the tendon insertion affected. About 20 million Americans have point. In Osgood-Schlatter disease, sometimes osteoarthritis. called jumper’s knee, tiny fragments of developing Osteoarthritis damages CARTILAGE, the thin layer bone tissue pull away from the epiphysis and of smooth connective tissue that coats the ends of become embedded in the tendon. As these frag- bones with the joints. Cartilage is so dense that it ments, called avulsion fractures, mineralize they does not have its own BLOOD supply. Instead, it form a hard lump just below the patella (kneecap). relies on adjacent tissues and the synovial fluid to The main symptoms of Osgood-Schlatter dis- supply it with the NUTRIENTS it requires. Cartilage ease, also called osteochondrosis, are a noticeable cannot regenerate or rebuild itself so damage to it 341 342 The Musculoskeletal System is permanent. Osteoarthritis is a leading cause of Risk Factors and Preventive Measures disability in the United States. The primary risk for osteoarthritis is increased age. Osteoarthritis is uncommon in people under age Symptoms and Diagnostic Path 50. Early diagnosis allows early treatment, which Many people who have osteoarthritis sufficient to helps prevent further deterioration of the involved show up on X-RAY have few if any symptoms. JOINT. Because so many factors converge to estab- Researchers estimate that by age 60, more than lish osteoarthritis, there are no measures known half of Americans have radiologic evidence of to prevent it. osteoarthritis. However, fewer than 20 percent of See also ANKYLOSING SPONDYLITIS; EXERCISE AND Americans seek medical treatment for symptoms HEALTH; INFECTIOUS ARTHRITIS; REITER’S SYNDROME; of osteoarthritis. Stiffness and PAIN in the joints are RHEUMATOID ARTHRITIS; SPINAL STENOSIS. the main symptoms of osteoarthritis. Discomfort is usually greatest in the morning when first getting osteochondrosis See OSGOOD-SCHLATTER DISEASE. out of bed and after physical activity. The diagnostic path may include X-ray to assess osteogenesis imperfecta A genetic disorder, the extend of damage within painful joints. But commonly called brittle BONE disease, in which because the damage primarily affects cartilage, a there are defects in the ways the body produces soft tissue, the full extent of osteoarthritis is not type 1 collagen, a fibrous protein that is the foun- likely to be apparent with X-ray. The doctor may dation of bone formation. As a result the bones request other diagnostic procedures to rule out lack proper structure and density and are highly conditions that have similar symptoms. However, susceptible to FRACTURE. The defective collagen a detailed PERSONAL HEALTH HISTORY in combination may affect other structures in the body as well, with a comprehensive medical examination is notably the LUNGS. HEARING LOSS is also common. generally sufficient for the doctor to make the Most osteogenesis imperfecta is inherited though diagnosis. may occur as the result of spontaneous MUTATION. There are four types of osteogenesis imperfecta: Treatment Options and Outlook Treatment for osteoarthritis attempts to slow the • Type 1 osteogenesis is the most common. Peo- degeneration by reducing INFLAMMATION. NON- ple who have type 1 disease generally reach STEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS) and normal height and have few obvious skeletal injections of CORTICOSTEROID MEDICATIONS are very deformities. Type 1 osteogenesis imperfecta typ- effective in accomplishing this goal. NSAIDs also ically causes more fractures during childhood relieve pain. Other treatment includes easing the than in adulthood. Hearing loss is pronounced stress on the joints, daily physical exercise for and begins early in childhood. WEIGHT LOSS AND WEIGHT MANAGEMENT, and meas- • Type 2 osteogenesis imperfecta is the most rare ures such as moist heat to affected joints. Exercises and the most severe. It produces numerous can strengthen the muscles and other structures of deformities of the SKELETON and often is fatal in the joints. YOGA is excellent for improving range of infancy. The abnormal collagen formation also motion and FLEXIBILITY. profoundly affects the lungs, causing significant Though there are no treatments that can cure BREATHING problems. osteoarthritis, a blend of medical therapies and lifestyle modifications can keep symptoms in • Type 3 osteogenesis imperfecta produces obvi- check. Many people who have osteoarthritis are ous skeletal deformities. Fractures before birth able to enjoy favorite activities with few if any are common; ULTRASOUND can detect them in restrictions when they follow appropriate meas- the FETUS. Type 3 disease also affects the lungs ures to control future damage of the joints. Signif- and muscles. Hearing loss begins in early child- icant damage to the joint may require joint hood and often becomes complete by ADOLES- replacement. CENCE. osteomyelitis 343

• Type 4 osteogenesis imperfecta is more severe • numbness or tingling around the lips than type 1 but less severe than type 3. Frac- • MUSCLE weakness tures are most common before PUBERTY. Hearing • pathologic bone FRACTURE (fractures that occur loss begins in early childhood and is often pro- with minimal trauma or spontaneously) found. Bone biopsy provides the conclusive diagnosis. The bones of infants who have osteogenesis Treatment is usually intense vitamin D supple- imperfecta are very fragile and may fracture with mentation until bone mineralization returns to the slightest contact, even that of picking up or normal. Depending on the underlying cause of the holding the infant. Nonetheless, touch and hold- osteomalacia, some people may also need to take ing are very important for proper development. phosphorus supplements. Most people recover The health-care team can provide suggestions to fully with appropriate treatment. minimize the risk for fracture. Treatment for frac- See also ANTACIDS; CALCIUM AND BONE HEALTH; ture is generally conservative, targeting a balance MINERALS AND HEALTH; OSTEOPENIA; OSTEOPETROSIS; between immobilizing the fracture long enough OSTEOPOROSIS; RICKETS; VITAMINS AND HEALTH. for it to heal and allowing normal MUSCLE function as quickly as possible. Physical activity helps osteomyelitis An INFECTION of the BONE. Typically strengthen muscles and bone, which in turn mini- the infection starts elsewhere in the body and mizes fractures. The most numerous fractures spreads through the BLOOD circulation to the bone, occur during childhood when the bones are grow- though may originate in the bone as a complica- ing and thus have lower mineral content. The risk tion of surgery on the bone (such as open reduc- for fracture is lifelong, however, and may increase tion of a FRACTURE or JOINT REPLACEMENT). Bacterial in women after MENOPAUSE when BONE DENSITY nat- infection causes most osteomyelitis, though other urally declines. There are as yet no treatments to pathogens such as fungi (yeast) may also be overcome the collagen deficiencies of osteogenesis responsible. The long bones in the leg are the most imperfecta. common locations for osteomyelitis in children; See also GENETIC DISORDERS; INHERITANCE PATTERN. osteomyelitis in adults tends to settle in the hip or pelvis. osteomalacia Softening of the bones that most often occurs as a result of vitamin D deficiency or Symptoms and Diagnostic Path abnormalities in vitamin D METABOLISM that pre- Symptoms of osteomyelitis include vent mineral crystals from accumulating in the BONE tissue. Vitamin D is essential to bone remod- • PAIN from the area of the infection eling and the bone’s ability to draw calcium and • swelling in the area of the infection other minerals from the BLOOD circulation. Osteomalacia develops when there is insuffi- • FEVER cient mineralization of the osteoid, a collagen- • generalized discomfort and sense of not feeling based substance the osteoblasts (bone-forming well cells) produce. Instead of hardening into the bone matrix, the osteoid simply accumulates within the The diagnostic path begins with a comprehen- bone. Other causes of osteomalacia include sive medical examination and PERSONAL HEALTH HIS- chronic LIVER disease, END-STAGE RENAL DISEASE TORY to identify any recent infections, injuries, or (ESRD), hypophosphatemia (insufficient phospho- surgeries. X-RAY may show the area of infection, rus intake or metabolism), fluoride toxicity, and though other imaging procedures such as bone excessive antacid consumption. scan or MAGNETIC RESONANCE IMAGING (MRI) often Symptoms of osteomalacia include produce more complete information. Biopsy of the site confirms the diagnosis and can identify the • bone PAIN, especially in the hips responsible PATHOGEN. Blood tests such as complete 344 The Musculoskeletal System blood count (CBC) are likely to show elevated symptoms such as pain can keep the infection white blood cell (WBC) count and other changes contained enough for antibiotic therapy to be in the blood when there is an infection present. effective. See also BACTERIA; FUNGUS. Treatment Options and Outlook Surgical debridement (an OPERATION to clean pus osteopenia A preclinical circumstance of and damaged tissue from the infected area) and reduced BONE DENSITY. Doctors generally consider ANTIBIOTIC MEDICATIONS administered intravenously osteopenia to precede OSTEOPOROSIS. Osteopenia are the first course of treatment for osteomyelitis. has no symptoms and is a diagnosis the doctor Once the infection is under control, the doctor arrives at as a consequence of the person’s BONE may switch to oral antibiotics. The course of density score with radiologic (X-RAY based) bone antibiotic treatment may extend six weeks or density measurement. About 34 million Ameri- more, depending on how well the infection cans, mostly women at or beyond MENOPAUSE and responds. men older than age 60, have osteopenia. Infections in the bone are particularly hard to Osteopenia may result from various metabolic treat because the bone’s blood circulation does not circumstances. The World Health Organization deliver antibiotic medications to the bone very (WHO) defines osteopenia as bone density that is effectively. The infection may cause an ABSCESS no greater than 2.5 standard deviations below (pocket of pus) that in turn causes the death of normal bone density (reported as a T-score bone tissue. When such a scenario unfolds, the between –0.1 and –2.5). Conventional diagnostic osteomyelitis becomes chronic and may destroy methods establish a scale of bone density relative considerable bone tissue. It may be necessary for to that of a young person of the same gender at an the orthopedic surgeon to create a surgical wound age when bone density is at its peak. over the site of the infection to clean it and irri- Many people can restore bone density through gate the area. RESISTANCE EXERCISE and increased calcium con- Acute osteomyelitis that responds to antibiotic sumption. Doctors generally do not treat osteope- medication may heal without complications. nia beyond these measures but instead closely Chronic osteomyelitis, particularly with abscess, monitor bone density. Osteopenia is a warning may have a less favorable outcome with extended sign for women approaching or beyond antibiotic therapy necessary for several months. menopause, as bone density loss accelerates when Several surgical operations may be necessary to estrogen levels in the body decrease. Lifestyle fac- clean the infection site and prevent abscesses from tors that contribute to osteopenia include physical forming. The surgeon may leave the wound open inactivity, cigarette smoking, and excessive ALCO- or insert a drain to facilitate HEALING. Long-term HOL consumption, all of which interfere with cal- chronic osteomyelitis can cause permanent dam- cium transfer and other metabolic processes age to the structure of the bone. When chronic related to bone remodeling. osteomyelitis accompanies joint replacement, it See also CALCIUM AND BONE HEALTH; ESTROGENS; may be necessary to remove the prosthesis until EXERCISE AND HEALTH; LIFESTYLE AND HEALTH; OSTEOPET- the infection heals. The treatment of last resort is ROSIS. AMPUTATION. osteopetrosis A rare genetic disorder in which Risk Factors and Preventive Measures BONE remodeling is defective. Though the body People at particular risk for osteomyelitis are those builds new bone (osteoblastic activity), it does not who have DIABETES or who are on hemodialysis for adequately clear away old bone (osteoclastic activ- END-STAGE RENAL DISEASE (ESRD). Trauma to the ity). Consequently the bones become very dense bone, such as open fracture or surgery, also though are also very brittle and vulnerable to increases the risk for infection. Prevention is not FRACTURE. When symptoms are present early in always possible, though using measures to appro- childhood (infantile osteopetrosis), the outcome is priately care for wounds and respond to early very poor because the excessive bone structure osteoporosis 345 crowds out the BONE MARROW. BONE MARROW TRANS- Symptoms and Diagnostic Path PLANTATION is at present the only successful treat- Early indications of accelerated bone loss include 1 ment for infantile osteopetrosis but itself carries loss of more than ⁄2 inch in height and develop- significant risk. ment of kyphosis (hump in the middle of the Adult-onset osteopetrosis is present from birth back). However, these signs develop slowly and but does not cause symptoms until adulthood over considerable time, often several decades, when the abnormalities of bone structure are which makes them less apparent. Health experts advanced enough to become apparent. Many call osteoporosis a silent disease because there are adults who have osteopetrosis do not have overt few indications of its presence until it is well symptoms and discover they have the disorder established. Often the first symptom of osteoporo- when receiving treatment for another condition sis is an unexpected fracture. The wrist, spine, and for which the doctor requests an X-RAY. X-ray pro- hip are the most vulnerable sites for fracture. X- vides definitive diagnosis as osteopetrosis has a RAY shows a characteristic porous structure to the distinct, characteristic presentation. There are no bones, demonstrating the loss of mineral content treatments for adult-onset osteopetrosis other and bone mass. Bone density tests such as DEXA than efforts to reduce the risk for fracture. Adult- scan can detect demineralization before fracture onset osteopetrosis increases the risk for occurs. OSTEOMYELITIS (INFECTION of the bone), which is one Doctors use a scale of relative percentage of of the common reasons people initially seek med- bone loss to measure the severity of osteoporosis. ical care. The scale represents bone loss as a standard devia- See also GENETIC DISORDERS; INHERITANCE PATTERN; tion (SD) from the accepted norm for optimal MUTATION; OSTEOMALACIA; OSTEOPOROSIS. healthy bone mass. An SD value of –2.5 or greater (2.5 SDs below the norm) is diagnostic for osteo- osteoporosis A condition of diminished BONE porosis. Testing facilities report this value as a T- DENSITY (the extent of mineralization of the bones). score; the norm for comparison is the bone Though some loss of mineralization is a normal density of a young healthy person of the same process of aging, osteoporosis represents an accel- gender. Another representation is the Z-score, erated loss that causes health problems. Osteo- which compares the person’s bone density to that porosis weakens the BONE structure; increases the of the norm for others of the same age and gen- risk for FRACTURE; and may result in bone deformi- der. Some testing facilities report bone loss as a ties, particularly of the spine. The spine and hip percentage; a –2.5 SD value represents about a 35 are most vulnerable to fracture. Osteoporosis typi- percent loss of bone density (bone mass is 65 per- cally affects women after MENOPAUSE, though may cent of what it should be). develop earlier in women who do not produce estrogen, and men age 75 and older. About 10 Treatment Options and Outlook million Americans have osteoporosis, 80 percent Weight-bearing and RESISTANCE EXERCISE is essential of whom are women. to stimulate bone remodeling activity. For estab- Osteoporosis appears to primarily affect women lished osteoporosis treatment focuses on decreas- for two reasons: estrogen and body size. ing the resorption of bone to increase bone mass. Researchers do not fully understand how estrogen Several kinds of medications can achieve this protects bone health but they do know that when effect. Among them are calcium and vitamin D estrogen levels fall dramatically, as with supplements, estrogen supplements, bisphospho- menopause, bone demineralization accelerates. As nates, PARATHYROID HORMONE supplement, CALCI- well, women have inherently less body mass— TONIN supplement, and Selective estrogen receptor bone mass and MUSCLE mass—than men. Some modulators (SERMs). Individual circumstances researchers theorize that bone demineralization determine which treatment approaches are most takes longer to affect men because their larger appropriate. skeletons can withstand a greater loss of calcium Calcium and vitamin D The body’s ability to before becoming thin and weak. absorb dietary calcium diminishes with advancing 346 The Musculoskeletal System age. As well, people tend to drink less milk and within the body that regulate bone remodeling. consume fewer dairy products, the primary Parathyroid hormone stimulates osteoblast activity sources of dietary calcium, as they get older. Most (new bone formation); calcitonin suppresses adults should take calcium supplements to get osteoclast activity. Taken as supplements, these 1000 to 1200 milligrams of calcium daily com- hormones have similar actions. They are not as bined with dietary calcium. Though calcium can- effective as the bisphosphonates, however. not restore bone structure that is already lost to Selective estrogen receptor modulators (SERMs) osteoporosis, the bones need abundant calcium Women who are beyond menopause can take simply to maintain bone remodeling. Vitamin D is SERMs, sometimes called designer ESTROGENS, necessary for the body to absorb calcium. which have many estrogen-like actions in the Estrogen Before the 1990s doctors routinely body. As the name suggests, however, SERMs prescribed hormone replacement therapy (HRT) selectively target estrogen receptors so are not for women going through and women beyond entirely the same as estrogen. Some SERMs, menopause. The prevailing belief was that HRT notably raloxifene, have an estrogen-like effect on provided protection for women against CARDIOVAS- bone remodeling without estrogen-like effects CULAR DISEASE (CVD) and osteoporosis. Extensive elsewhere in the body. SERMs stop bone loss but studies demonstrated that HRT provided no pro- do not stimulate new bone tissue. tection for HEART disease and in fact increased the risk for some kinds of CVD (notably STROKE) as Risk Factors and Preventive Measures well as some forms of cancer. Women over age 70 who are white or Asian and The findings regarding osteoporosis were not as are thin have the greatest risk for osteoporosis. definitive as expected. Estrogen does slow the loss However, regardless of ethnicity women past of bone. However, its effect is most pronounced menopause have increased risk for osteoporosis during the first three to five years after because of the loss of estrogen. Other risk factors menopause and it does not stimulate production for osteoporosis include long-term use of systemic of new bone. Though doctors sometimes prescribe CORTICOSTEROID MEDICATIONS (such as to treat estrogen replacement (in combination with PROG- AUTOIMMUNE DISORDERS or endocrine disorders), cig- ESTERONE supplement for women who have their arette smoking, low calcium consumption, physi- uteruses) for women who are at high risk for cal inactivity, excessive CAFFEINE consumption, and developing osteoporosis, other medications are excessive ALCOHOL consumption. often more effective with fewer risks. Bisphosphonates Bisphosphonates are medica- COMPLICATIONS OF FRACTURE tions that block the activity of osteoclasts to resorb Though fracture alone is a significant health con- bone and calcium. Because these drugs are rela- cern, the complications of fracture can be life tively new, doctors do not know their long-term threatening. Fracture generates a high risk for consequences. Bisphosphonates can stop the pro- BLOOD clots as well as for fat emboli—fragments gression of osteoporosis as well as prevent osteo- of fatty tissue that the fracture dislodges and that porosis from developing in men and women who make their way into the blood circulation. Blood have high risk. However, bone loss resumes when clots and fat emboli can cause STROKE or HEART the person stops taking the medication. ATTACK, depending on where they lodge in the blood vessels. BISPHOSPHONATES TO TREAT OR PREVENT OSTEOPOROSIS Calcium and vitamin D supplementation in alendronate clodronate combination with weight-bearing or resistance etidronate ibandronate exercise early in life, but particularly before dem- pamidronate risedronate ineralization becomes significant, is the most effective preventive treatment. Health experts Parathyroid hormone and calcitonin Parathy- believe nearly all osteoporosis is preventable. But roid HORMONE and calcitonin are natural hormones as with other lifestyle-related health conditions, osteoporosis 347 prevention efforts must begin in childhood and See also AGING, MUSCULOSKELETAL CHANGES THAT continue through life. The most effective time to OCCUR WITH; DIET AND HEALTH; EXERCISE AND HEALTH; supplement calcium is when the body is building HIP FRACTURE IN OLDER ADULTS; OSTEOMALACIA; bone mass—before age 20. OSTEOPENIA; SKELETON; SMOKING AND HEALTH. P

Paget’s disease of the bone A rare and some- out the body. The pattern of bone damage is char- times hereditary condition in which the process of acteristic. BONE remodeling sporadically accelerates. The new bone that forms to replace old bone has increased Treatment Options and Outlook mass, enlarging the bone structure, though is Treatment for Paget’s disease of the bone targets weaker than normal bone. Paget’s disease of the both bone loss and symptoms such as pain. Med- bone affects bones randomly throughout the body. ications to slow bone resorption (osteoclast activ- Most often affected are the spine, hips, legs, and ity) help retain more normal bone structure. cranium (skull). Paget’s disease of the bone is Among these medications are CALCITONIN and more common in people over age 40 and affects the bisphosphonates (alendronate, clodronate, men and women about equally. Some researchers etidronate, pamidronate, risedronate, and tilu- believe Paget’s disease of the bone is genetic and dronate). ANALGESIC MEDICATIONS and NONSTEROIDAL other researchers believe a VIRUS activates it. ANTI-INFLAMMATORY DRUGS (NSAIDS), in over-the- counter or prescription products, may be neces- Symptoms and Diagnostic Path sary to relieve pain. It is not uncommon for someone to be unaware he or she has Paget’s disease of the bone until sev- Risk Factors and Preventive Measures eral bone fractures occur. Other people have obvi- The primary risk factor for Paget’s disease of the ous abnormalities of the spine, bowed legs, and bone is a family history, known or suspected, of moderate to severe JOINT PAIN and bone pain. the condition. Though there are no measures to When there is family history of Paget’s disease of prevent Paget’s disease of the bone, early diagnosis the bone the doctor may look in that direction for offers the best opportunity to mitigate bone loss diagnosis. When there is not, doctors tend to first and other symptoms. explore more common causes for similar symp- See also BONE CANCER; CALCIUM AND BONE HEALTH; toms (such as OSTEOPOROSIS). The diagnostic path GENETIC DISORDERS; OSTEOGENESIS IMPERFECTA; OSTEO- then becomes circuitous, and diagnosis may take MALACIA. quite some time. BLOOD tests to measure the presence of an palmar fibromatosis See CONTRACTURE. enzyme, alkaline phosphatase, suggest a disorder of bone growth when the enzyme is present. patellofemoral syndrome Pain at or around the Alkaline phosphatase levels in the body rise patella (kneecap) that often is worse when walk- whenever there is new bone growth activity. ing or running downhill or going down steps. Though not diagnostically conclusive, elevated Many people also experience the same kind of alkaline phosphatase further points in the direc- pain when sitting with the knees bent for a pro- tion of Paget’s disease of the bone. COMPUTED longed time. Doctors believe patellofemoral syn- TOMOGRAPHY (CT) SCAN and MAGNETIC RESONANCE drome results from a combination of factors that IMAGING (MRI) can show the extent to which the include anatomy (individual variations in the dysfunctional remodeling affects bones through- structure of the knee), biomechanics (the function 348 plantar fasciitis 349 of the knee), and the kinds of activities the person physical therapy A therapeutic approach to conducts. maintain or improve the biomechanics of the The more inactive an individual is, the more body. Physical therapy employs many modalities likely he or she is to develop patellofemoral syn- (types of treatments) including passive and active drome. However, most doctors do not believe this range of motion exercises, THERAPEUTIC MASSAGE, condition is one of overuse. Some experts believe hydrotherapy, therapeutic ULTRASOUND, heat and an imbalance of STRENGTH among the four parts of cold, strengthening exercises, FLEXIBILITY exercises, the quadriceps permits dysfunctional tracking of and balance exercises. In the United States physi- the patella, contributing to the syndrome. Most cal therapy requires a doctor’s prescription. The athletic activities that use the quadriceps, such as doctor may prescribe physical therapy for people running and bicycling, strengthen the lateral recovering from serious injury, surgery, or STROKE. (outer) muscles more than the medial, pulling the Physical therapy also is helpful for conditions of patella off track. impaired motor function such as CEREBRAL PALSY and PARKINSON’S DISEASE. Symptoms and Diagnostic Path See also OCCUPATIONAL THERAPY; QUALITY OF LIFE; The main symptom of patellofemoral syndrome is STRENGTH. PAIN going down steps or downhill and when sit- ting for long periods of time with the knees bent plantar fasciitis INFLAMMATION of the FASCIA along (flexed). The characteristic and specific nature of the bottom of the foot (plantar surface). Fascia is a these symptoms allow the doctor to make a thin, tough sheet of connective tissue that covers straightforward clinical diagnosis. X-rays and and connects the muscles, tendons, and other other diagnostic imaging procedures are not nec- connective tissue structures throughout the body. essary unless there is reason to suspect another It becomes irritated and inflamed with overuse. reason for the symptoms. Plantar fasciitis develops with repeated stretching of the plantar fascia such as may occur with Treatment Options and Outlook extensive walking or prolonged standing on a Treatment often combines one of the NONSTEROIDAL hard surface such as concrete. People whose jobs ANTI-INFLAMMATORY DRUGS (NSAIDS) to relieve require walking on hard surfaces, such as mail INFLAMMATION and pain with PHYSICAL THERAPY to carriers and police patrol officers, are particularly strengthen the quadriceps, particularly the medial vulnerable to plantar fasciitis. Excessive body (inner) muscles of this group. Most people experi- weight contributes to the stress the plantar fascia ence relief from this treatment approach within experiences, as do overly flat shoes, exacerbating two weeks and can return to their regular activi- the inflammation. ties, including most sports, in four to six weeks. The pain of plantar fasciitis is distinctly charac- teristic; the doctor usually makes the diagnosis on Risk Factors and Preventive Measures the basis of symptoms. The PAIN begins in the heel Women, particularly those in their late teens and and is most significant when returning to the feet early 20s who are inactive, are more likely than after being off of them for a while, such as when men to develop patellofemoral syndrome. first getting out of bed in the morning or after an Researchers do not know why this is. Exercises to extended work break. Immediate ice to the area of maintain balanced strength in the quadriceps MUS- pain helps suppress the inflammation; NON- CLE appears to prevent further occurrences of STEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS) block symptoms. A soft knee brace that holds the patella the inflammatory response and relieve pain. Shoes in position may also help maintain proper tracking with cushioned soles and insoles, shock-absorbing of the patella. Some athletic trainers advocate floor mats, and shoe orthotics to hold the foot in wrapping or taping the knee before participation the best position for the individual are among the in an athletic event, which accomplishes a similar methods that reduce the risk for plantar fasciitis. purpose. Stretching exercises to loosen the fascia further See also KNEE INJURIES. relieve pressure. Most people recover from an 350 The Musculoskeletal System episode of plantar fasciitis within six to eight • JOINT PAIN weeks. With appropriate preventive measures, • fatigue many people are able to keep symptoms from • difficulty swallowing returning. See also LIGAMENT; MUSCLE; REPETITIVE MOTION The diagnostic path includes BLOOD tests to INJURIES; TENDON; WEIGHT LOSS AND WEIGHT MANAGE- detect antibodies and elevated enzymes that indi- MENT. cate muscle injury within the body. Muscle biopsy may show the inflammation within the sample of polydactyly Extra fingers or toes. Polydactyly muscle tissue. Sometimes MAGNETIC RESONANCE may occur spontaneously and isolated (without IMAGING (MRI) presents a pattern of the inflamma- apparent cause) or in conjunction with GENETIC tion’s presence in the body. Because there are no DISORDERS such as PATAU’S SYNDROME (trisomy 13). conclusive diagnostic tests for polymyositis, the Most often the extra digit is on the little finger or diagnostic journey can be arduous and frustrating. little toe side of the hand or foot, respectively, and is so rudimentary as to be functionless. Nearly Treatment Options and Outlook always the doctor recommends removing the Treatment for polymyositis is a combination of extra digit, which may be done with banding (the CORTICOSTEROID MEDICATIONS and IMMUNOSUPPRESSIVE doctor places a band tightly around the base of a MEDICATIONS, which work together to mitigate the rudimentary digit, cutting off its BLOOD supply so it IMMUNE SYSTEM’s inflammatory response. Physical slowly withers and falls off) or as a surgical AMPU- therapy for passive and active range of motion TATION. exercises helps maintain optimal joint function. See also AUTOSOMAL TRISOMY; SYNDACTYLY. Daily physical activity has similar effect. Polymyositis is a lifelong condition that, when polymyositis A chronic condition of widespread symptoms are severe, can result in permanent dis- INFLAMMATION of the muscles. The inflammation ability. causes weakness and difficulty with everyday movements including walking, reaching for Risk Factors and Preventive Measures objects, bathing, and dressing. Polymyositis is a Because researchers do not know what causes type of inflammatory MYOPATHY that many polymyositis, there are no known measures to researchers believe is autoimmune in its origins. prevent its development. Early diagnosis and Other researchers believe polymyositis and other treatment offer the most effective approach for inflammatory myopathies develop after viral minimizing the course of the disease and reducing INFECTION or as side effects of cholesterol-lowering the seriousness of its symptoms. therapy with statin medications. Polymyositis has See also ANTIBODY; AUTOIMMUNE DISORDERS; alternating periods of RECURRENCE and REMISSION CHRONIC PAIN; QUALITY OF LIFE; SYSTEMIC LUPUS ERYTHE- that tend to be lifelong. Most people are age 50 or MATOSUS (SLE); VIRUS. older when they develop the condition. proprioception The body’s sense of its location Symptoms and Diagnostic Path within its physical environment. Proprioceptors The severity and range of symptoms vary among are specialized molecules on PERIPHERAL NERVES in individuals as well as across episodes within the the muscles that send a continuous barrage of same person. Symptoms of polymyositis may NERVE impulses to the basal ganglia and other include structures of the BRAIN that have roles in balance and movement. The balance functions in the • MUSCLE weakness throughout the body though vestibular structures of the inner EAR also con- most pronounced in the shoulders, upper arms, tribute sensory information. Proprioception is hips, and thighs essential for all voluntary movement. Propriocep- • both sides of the body equally affected tion diminishes in neuromuscular disorders such prosthetic limb 351 as PARKINSON’S DISEASE and also with ALCOHOL that are important to consider include comfort intoxication. The classic field SOBRIETY test is a and durability of the prosthesis. Most often it is measure of proprioceptive loss. advantageous to begin using the prosthesis as soon See also VESTIBULAR NEURONITIS. as possible after the amputation, to return to nor- mal daily living. prosthetic limb An artificial arm, hand, leg, or There are numerous designs and styles of pros- foot that provides functional replacement for an thetic limbs; the prosthesis is fitted to the person amputated or missing limb. A prosthesis repre- to meet the person’s unique individual needs. sents a balance between function and presentable Some prosthetic limb designs, particularly upper appearance. Prosthetic limbs available today can extremity, strive to appear as natural as possible. provide a very high level of function, allowing Other designs are primarily functional. Some many people to return to nearly the same lifestyle designs are mechanical and others are electronic. as before the amputation. Some prostheses are for specific purposes, such as Selection and fitting of the prosthesis can take athletic activities (running, hiking, bicycling, place as soon as the AMPUTATION stump heals from downhill skiing). Other prostheses may be more the surgery. The prosthesis must attach firmly to oriented toward allowing the person to return to a the amputation stump, which is more difficult particular occupation or skill. with high amputations (shoulder or hip). Factors See also OCCUPATIONAL THERAPY; QUALITY OF LIFE. R

Reiter’s syndrome An inflammatory disorder with a needle and syringe) from affected joints. X- commonly associated with INFECTION by the RAY studies may show characteristic changes in the MICROBE Chlamydia trachomatis. Other pathogens affected joints. that cause GASTROENTERITIS or SEXUALLY TRANSMITTED DISEASES (STDS) may also be responsible. Reiter’s Treatment Options and Outlook syndrome involves three components: URETHRITIS, The mainstay of treatment for Reiter’s syndrome is reactive arthritis (arthritis that develops in reac- therapy with NONSTEROIDAL ANTI-INFLAMMATORY tion to infection elsewhere in the body), and CON- DRUGS (NSAIDS). NSAIDs, usually prescription JUNCTIVITIS. People who have Reiter’s syndrome forms, control both inflammation and PAIN. An often have the human leukocyte antigen (HLA) active bacterial infection requires treatment with B27, which is also associated with the autoim- the appropriate ANTIBIOTIC MEDICATIONS. Symptoms mune arthritis ANKYLOSING SPONDYLITIS. Some peo- tend to last three to six months in most people; ple develop INFLAMMATION of the AORTA and other sometimes longer. In about a third of people, the major arteries as a consequence of the involve- arthritis component becomes chronic. Two thirds ment of vascular connective tissue. of people fully recover without residual effects.

Symptoms and Diagnostic Path Risk Factors and Preventive Measures Any of the three components of Reiter’s syndrome Men who develop Reiter’s syndrome outnumber may appear first, though commonly the urethritis women about 10 to 1. Sexually transmitted is the first to manifest symptoms. The other two chlamydia infection is the most common cause of components generally appear within 28 to 35 days the syndrome, so measures to reduce exposure to of the first component. Symptoms typically STDs can significantly reduce the development of include Reiter’s syndrome. See also BACTERIA; HUMAN LEUKOCYTE ANTIGENS • general feeling of malaise (HLAS); INFECTIOUS ARTHRITIS; PATHOGEN; SEXUAL • low-grade FEVER HEALTH. • MUSCLE aches and soreness, particularly when resting repetitive motion injuries Soft tissue injuries that occur as a result of overuse or performing the • burning, itchy eyes same motion over and over. Repetitive motion • conjunctivitis or IRITIS injuries, sometimes called cumulative trauma • inflammation of the TENDON insertion point in injuries, may occur as occupational injuries or affected joints (a unique arthritic symptom) ATHLETIC INJURIES. The most common repetitive • genital discharge and painless, shallow ulcers motion injuries are TENDONITIS (INFLAMMATION of a TENDON) and BURSITIS (inflammation of a BURSA). The diagnostic path includes laboratory testing These injuries may develop near any JOINT though for CHLAMYDIA in urethral and genital discharges as are most common in the knees, hips, wrists, well as any fluid the doctor aspirates (withdraws elbows, and shoulders. 352 ruptured disk 353

Typical symptoms of repetitive motion injuries apeutic approach for most musculoskeletal are injuries such as SPRAINS AND STRAINS. Rest removes the injured part from the source of the injury. Ice • PAIN and swelling slows the process of INFLAMMATION and eases PAIN. • numbness or tingling Compression, such as a wrap or brace, provides • limited range of motion or movement support so the muscles can relax. Elevation slows When establishing the diagnosis the doctor the flow of BLOOD through the part, further easing pays particular attention to the personal history of pain, reducing swelling, and enforcing rest. work, recreational, and other activities the indi- See also ATHLETIC INJURIES; BURSITIS; FRACTURE; vidual performs on a regular basis. Diagnostic SYNOVITIS; TENDONITIS. imaging procedures are usually not necessary. Treatment is rest from the activity that caused the rotator cuff impingement syndrome A chronic symptoms in combination with NONSTEROIDAL ANTI- overuse condition involving the rotator cuff, a INFLAMMATORY DRUGS (NSAIDS); heat or cold to the group of muscles and tendons in the shoulder that site; and PHYSICAL THERAPY to learn stretching exer- stabilizes the shoulder JOINT—the glenohumeral cises and techniques for lifting, standing, and sit- joint where the humerus (long BONE of the upper ting that support musculoskeletal health. arm) joins the upper part of the scapula (shoulder Poor posture, staying in one position for an blade)—during elevation of the arm. The rotator extended time, and repeating the same motion cuff is vulnerable to strains ranging in severity without breaking from it are the key risks for repet- from minor stretching of the tissues to significant itive motion injuries. Prevention efforts include fre- tears. The resulting INFLAMMATION constricts, or quent changes in posture and position and impinges, the ability of the shoulder to move frequent, short breaks from the repetitious task. through its full range of motion. OSTEOARTHRITIS This may be as simple as switching hands may also inflame the joint with the same conse- to perform the task or pausing at regular intervals quence. to stretch the muscles, stomp the feet, roll the neck The doctor’s examination includes a series of and shoulders, and shake or wiggle the hands. movements designed to elicit specific results that See also CARPAL TUNNEL SYNDROME; OCCUPATIONAL are relatively conclusive for rotator cuff impinge- HEALTH AND SAFETY; PATELLOFEMORAL SYNDROME; PLAN- ment. However, other conditions can produce sim- TAR FASCIITIS; ROTATOR CUFF IMPINGEMENT SYNDROME; ilar symptoms. COMPUTED TOMOGRAPHY (CT) SCAN, SYNOVITIS. MAGNETIC RESONANCE IMAGING (MRI), or ARTHROSCOPY may be necessary to confirm the diagnosis. rhabdomyoma A benign (noncancerous) tumor Most rotator cuff impingement symptoms that originates in MUSCLE tissue, usually skeletal respond to conservative treatment that includes muscle. Rhabdomyoma is somewhat more com- hot or cold to the shoulder, NONSTEROIDAL ANTI- mon in children than adults. The doctor may INFLAMMATORY DRUGS (NSAIDS), injection with CORTI- choose to surgically remove the rhabdomyoma to COSTEROID MEDICATIONS, PHYSICAL THERAPY, and rest obtain a definitive diagnosis and rule out cancer. with limited exercises to maintain FLEXIBILITY and However, rhabdomyoma does not become cancer- function of the joint. ADHESIVE CAPSULITIS, in which ous. Rather, it may have the appearance of a can- the tissues fuse together within the joint, is a major cerous tumor so the doctor removes it for biopsy risk of immobilizing the shoulder. Though most and laboratory analysis. Rhabdomyoma may occur people recover from an episode of symptoms with- in the HEART, presenting a potentially life-threaten- out residual complications, rotator cuff impinge- ing situation that usually requires surgery to ment syndrome tends to be chronic, with repeated remove the tumor. aggravation setting off new cycles of symptoms. See also LIPOMA. See also ATHLETIC INJURIES; MUSCLE; REPETITIVE MOTION INJURIES; SPRAINS AND STRAINS; TENDON. RICE The acronym for rest, ice, compression, and elevation. RICE is the common first-line ther- ruptured disk See HERNIATED NUCLEUS PULPOSUS. S

sciatica Irritation and INFLAMMATION of the sciatic scoliosis An abnormal curvature that takes the NERVE, which runs from the lumbar spine (low spine to the side. The healthy spine does not curve back) down the buttock and into the leg. Sciatica to the side. Scoliosis is idiopathic—that is, doctors is a type of peripheral NEUROPATHY that is often a do not know what causes it. Treatment to chronic condition. Injuries to the hip and pelvis straighten the spine in childhood is important may involve the sciatic nerve. However, often because the curvature is likely to become more there is no identifiable cause for sciatica. extreme in adulthood and can interfere with vari- The main symptom of sciatica is a shooting or ous functions, including BREATHING. Scoliosis searing PAIN that extends through the buttock and screening among children in the public schools is into the leg. Sciatica usually involves only one common in the United States. Adult-onset scolio- side of the body though sometimes symptoms sis, though uncommon, may occur with OSTEO- are bilateral (involve both sides), depending on POROSIS, RHEUMATOID ARTHRITIS, and other the cause. Typically no particular incident sets inflammatory conditions that affect the spine. off the pain; it just occurs and may be severe. Sci- atica may also interfere with foot placement or Symptoms and Diagnostic Path walking. The distinguishing symptom of scoliosis is an S- The diagnostic path begins with a NEUROLOGIC shaped curvature seen in the spine from behind. EXAMINATION that focuses on the lower body. In sci- Subtle symptoms of scoliosis that can help detect atica the reflexes at the knee and heel (ACHILLES the condition before the curvature becomes pro- TENDON REFLEX) are often slow or absent. Diagnos- nounced include tic procedures such as electromyogram (EMG) and nerve conduction studies typically produce abnor- • shoulders or hips that are noticeably uneven in mal results as well. Treatment targets the cause of height the sciatica when known and symptoms other- • the tendency to lean to one side wise. Medications such as NONSTEROIDAL ANTI- • the appearance of a twisted or uneven waist INFLAMMATORY DRUGS (NSAIDS) can relieve inflammation and pain, though people who have • shoulder blades that protrude prominently from severe pain may need prescription ANALGESIC MED- the upper back ICATIONS for pain relief. Exercises and physical • complaints of backache or shoulder discomfort activity to strengthen muscles and improve FLEXI- BILITY are helpful when the inflammation subsides. The diagnosis of scoliosis is generally clear from Most sciatica is a long-term, chronic condition that physical examination, though the doctor may con- comes and goes. Specific movements or activities duct X-RAY studies of the back to confirm it. may trigger pain in some people, and in other people the pain appears without apparent provo- Treatment Options and Outlook cation. Treatment for scoliosis includes exercises to stretch See also DIABETES; HERNIATED NUCLEUS PULPOSUS; and strengthen the structures of the back and SPINAL NERVES; SPINAL STENOSIS. often a brace that holds the spine in a more erect 354 sprains and strains 355 posture. A child may need to wear a scoliosis that form the body’s axis or perpendicular line, brace only at night or all the time, depending on which include the head, rib cage, and spine. It the severity of the scoliosis. Severe scoliosis or sco- contains 80 bones. The remaining 126 bones— liosis that persists despite treatment may require arms, hands, legs, feet, shoulders, pelvis, hips— surgery, in which the surgeon realigns the verte- form the appendicular skeleton. brae, sometimes bracing them with steel or tita- The primary functions of the skeleton are to nium rods to maintain them in proper position. give the body structure, support and protect the Most scoliosis, when detected early, responds very body’s internal organs, and enable mobility. well to treatment and is gone by the time the child Within certain bones is the BONE MARROW, which reaches late ADOLESCENCE. produces the body’s BLOOD cells. The skeleton also serves as the body’s “calcium bank,” storing cal- Risk Factors and Preventive Measures cium when levels in the blood circulation are ade- Because doctors do not know what causes most quate and pulling calcium from the bones when scoliosis, there are no known risk factors or pre- blood levels of calcium drop too low. ventive measures. Scoliosis often accompanies For further discussion of the skeleton within other conditions such as CEREBRAL PALSY, MUSCULAR the context of the structures and functions of the DYSTROPHY, and SPINA BIFIDA. Health experts urge musculoskeletal system, please see the overview women of childbearing age to take folic acid sup- section “The Musculoskeletal System.” plements, which can prevent many NEURAL TUBE See also BONE; CALCIUM AND BONE HEALTH; OSTEO- DEFECTS such as spina bifida. It also tends to run in MALACIA; OSTEOPOROSIS. families, leading doctors to suspect there are hereditary factors at play. sprains and strains Acute, traumatic injury to See also KYPHOSIS; LORDOSIS; SURGERY BENEFIT AND muscles, tendons, and ligaments, typically as a RISK ASSESSMENT. consequence of rapid and unexpected stretching such as may occur with a stumble, sudden twist- skeletal dysplasia Dysfunctional growth of the ing movement, or fall. A sprain is an injury to a SKELETON such that the person is of significantly LIGAMENT; ligaments connect bones to each other. short stature. There are numerous forms of skele- A strain is an injury to a MUSCLE or TENDON; ten- tal dysplasia, commonly and collectively called dons extend from muscles to connect them to dwarfism, most of which are hereditary. Skeletal bones. Sprains and strains nearly always occur in dysplasia may also occur as a result of HORMONE or near joints. A muscle, tendon, or ligament may deficiencies during childhood. Each type of skele- rupture (tear completely) under the force of a tal dysplasia presents characteristic symptoms. In sudden stretch. Though immediate treatment— general, skeletal dysplasias result in extremely RICE (rest, ice, compression, elevation)—remains short stature. The structures of the skeleton are the same, a rupture may later require surgical nearly always disproportionate. Disorders of repair. growth that are metabolic cause proportionate smallness. HORMONE THERAPY may increase skeletal A severe strain or sprain often is diffi- growth when the cause is endocrine or metabolic. cult to distinguish from a FRACTURE and There are no treatments to alter the skeleton should be treated as a fracture until when the cause of the dysplasia is genetic. medical assessment determines it is not. See also ACHONDROPLASIA; GENETIC DISORDERS; INHERITANCE PATTERN; OSTEOGENESIS IMPERFECTA; RICK- Symptoms and Diagnostic Path ETS; SCURVY. The main symptoms of a sprain or strain are PAIN and swelling following a sudden movement that skeleton The organization of the bones in the involves a JOINT. Both are often immediate, and it body. The skeleton has two primary organizational may be difficult to use the limb. Grade 1 sprains divisions: the axial skeleton and the appendicular and strains are painful but minor and do not nec- skeleton. The axial skeleton consists of the bones essarily require a visit to the doctor. However, it is 356 The Musculoskeletal System not possible to look at an injury and know Risk Factors and Preventive Measures whether there is a FRACTURE. A doctor should eval- Though sprains and strains are often ATHLETIC uate any injury in which INJURIES, they can occur during everyday activities such as walking or lifting as well as in MOTOR VEHI- • it is difficult to bear weight or use the arm or CLE ACCIDENTS. Proper technique for sports, includ- hand ing WARM-UP, and for lifting can prevent many soft tissue injuries. Taping or bracing vulnerable joints • there is numbness or tingling beyond the point such as ankles, knees, and wrists provides addi- of the injury (in the foot with an ankle injury, tional support. for example) See also ACCIDENTAL INJURIES; ANKLE INJURIES; HIP • pain is severe though the injury looks minor FRACTURE IN OLDER ADULTS; KNEE INJURIES; SURGERY BENEFIT AND RISK ASSESSMENT; WEAK ANKLES. Grade 2 injuries seldom require diagnostic imaging, though the doctor may request X-RAY, spasm A sudden, involuntary, and extended COMPUTED TOMOGRAPHY (CT) SCAN, OR MAGNETIC RESO- MUSCLE contraction. Muscle spasms generally last NANCE IMAGING (MRI) when there is doubt as to the no longer than a few seconds and are quite severity of the injury because this can affect the painful. Spasms may involve skeletal or involun- treatment approach. Doctors assign a grade value tary muscle. Muscle spasms of the pulmonary sys- to a sprain or strain to identify its severity, with tem may manifest as ASTHMA or bronchiospasms grade 1 the least and grade 4 the most severe. that, when severe, may interfere with BREATHING. ARTHROSCOPY may be necessary to accurately dis- Skeletal muscle spasms may result from overuse, tinguish a grade 3 from a grade 4 injury. extreme cold, or neuromuscular disorders. Heat, massage, and gentle stretching can relieve muscle Grade of Sprain/Strain Severity of Injury spasms. WARM-UP before strenuous exercise and grade 1 stretching and minor tearing of regular activities to stretch and strengthen the fibers but structure remains intact muscles help prevent muscle spasm. grade 2 partial tear of the structure and See also CHARLEYHORSE; CRAMP; MYOPATHY. some instability of the JOINT grade 3 significant tear of the structure and spinal stenosis Narrowing of the vertebral chan- major instability of the joint nel, usually in the lower (lumbar) back, that com- grade 4 complete tear of the structure and presses the SPINAL CORD or the spinal NERVE roots. inability to use the joint The narrowing may develop as a consequence of osteoarthritic changes, the formation of BONE Treatment Options and Outlook spurs, or a congenital defect in which the verte- Grade 1 and grade 2 sprains and strains heal in bral channel is unusually narrow to begin with. two to six weeks with conservative treatment that Symptoms of spinal stenosis are weakness or includes continued RICE: rest, ice (or heat, after numbness in the legs, along with disturbances of 48 hours, if heat feels better than ice), compres- gait (the mechanics of walking) and balance. sion (elastic wrap, soft splint, tape, or brace), and There may also be low BACK PAIN and PAIN in the elevation of the injured body part. Some grade 3 legs. and nearly all grade 4 sprains and strains require The diagnostic path typically includes compre- surgery to repair the damage and reconstruct the hensive medical examination with full NEUROLOGIC tissues. The doctor can do this repair during diag- EXAMINATION and diagnostic imaging procedures nostic arthroscopy or with arthroscopic surgery such as MAGNETIC RESONANCE IMAGING (MRI) or COM- after confirming the diagnosis through other PUTED TOMOGRAPHY (CT) SCAN that can show dimen- means. Recovery after surgery may take up to six sional views of the internal and external months, depending on the location and severity of structures of the spine. Such views help the doctor the injury. determine the location and extent of the stenosis. synovitis 357

When diagnosis is early, conservative treatment involves the third and fourth fingers or toes, such as exercises that extend the spine (bend the though sometimes affects multiple fingers or toes. body forward) and medications such as NON- Treatment is typically to separate the fused digits STEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS) may surgically to allow full use of the hand or foot. reduce the causes of the stenosis enough to relieve See also GENETIC DISORDERS; LIGAMENT; POLY- the compression of the nerves. Heat, cold, and DACTYLY; SURGERY BENEFIT AND RISK ASSESSMENT. weight loss also help. Physical exercise that stretches and strengthens the muscles without synovitis INFLAMMATION of the synovial mem- compressing the spine, such as bicycling and brane that lines the JOINT capsule of joints such as swimming, improves the ability of the muscles to the hip and knee. Synovitis is common in RHEUMA- support the body and further relieves pressure on TOID ARTHRITIS, GOUT, SYSTEMIC LUPUS ERYTHEMATOSUS the spine. (SLE), and INFECTION. Generally there is PAIN, often When these measures do not relieve symptoms, severe, and swelling due to fluid accumulation. surgery to widen the vertebral channel may be The SKIN over the joint is often hot to the touch necessary to prevent permanent loss of function in and red. The doctor may aspirate (withdraw with the legs. Because the outcome of back surgery is a fine needle) some fluid from within the joint to less predictable than many other kinds of surgery, rule out INFECTION. it is important to discuss and understand the Most synovitis improves with NONSTEROIDAL expected benefits and potential risks of any OPERA- ANTI-INFLAMMATORY DRUGS (NSAIDS); severe or recur- TION the doctor proposes. rent synovitis may require injected CORTICOSTEROID See also BONE SPURS; CERVICAL SPONDYLOSIS; MEDICATIONS along with a local anesthetic to relieve OSTEOARTHRITIS; SCIATICA; SPINAL NERVES; SURGERY BEN- PAIN and reduce inflammation. The extent of EFIT AND RISK ASSESSMENT. improvement depends on the underlying cause. Unfortunately synovitis often becomes a chronic syndactyly Fingers or toes that are fused presence with rheumatoid arthritis. DISEASE-MODI- together by connective tissue. Sometimes the FYING ANTIRHEUMATIC DRUGS (DMARDS), which slow fusion is only SKIN (simple syndactyly) and other the progression of rheumatoid arthritis, may times the fusion involves MUSCLE, ligaments, and lessen the symptoms of synovitis as well. When BONE (complex syndactyly). Syndactyly is present BACTERIA are present in the synovial fluid, treat- at birth and often indicates a genetic disorder with ment requires ANTIBIOTIC MEDICATIONS. additional symptoms. Most commonly the fusion See also BURSITIS; TENDONITIS. T

talipes equinovarus A CONGENITAL ANOMALY in cutting, tearing, and chewing the food as well as which an infant is born with one foot or both feet for forming the sounds of language. A person deformed into the shape of a club, hence the com- develops two sets of teeth during his or her life- mon term for the condition, “clubfoot.” The time. The first set, the primary teeth, erupts affected foot turns in and under at the heel, such around six months of age and remains in place that the top of the foot appears nearly upside- until six or seven years of age. Then the perma- down. All the bones, muscles, and other connec- nent teeth begin to push through the gum and the tive tissues are usually present though deformed primary teeth fall out. There are 20 primary teeth in structure. and 32 permanent teeth by adulthood. The last 4 The anomaly forms in the last part of the first permanent teeth, molars in the back of the mouth trimester of PREGNANCY when the muscles, bones, called the wisdom teeth, erupt through the gum- and connective tissues develop. Researchers do line at age 18 to 20. not know what causes talipes equinovarus though believe it is a combination of environmental fac- When a blow to the face knocks out a tors (such as the fetus’s position in the UTERUS) and tooth, retrieve the tooth and put it in a genetic factors. The condition must be corrected plastic bag with ice. The dentist often for the child to walk; treatment is most successful can put the tooth back in place and the when it begins shortly after birth. tooth will reroot. The current standard of treatment is progres- sive casting during the first months of life, typi- The outer layer of the tooth, the enamel, is the cally with the cast changed each week to move densest, hardest substance in the body. Highly the foot slightly closer to normal position and mineralized, enamel cannot replace itself when gradually stretch the foot’s soft tissue structures damaged. At the core of the tooth is one of the (the Ponseti casting method). Often the doctor softest, the pulp. The pulp encases and nourishes must cut the ACHILLES TENDON to allow it to the NERVE. Between the enamel and the pulp is a lengthen so the foot may completely return to its layer of calcified tissue almost as hard as BONE, the normal position. When the foot finally reaches dentin. The tooth’s root extends from the jaw- normal position, the doctor removes the casts and bone. The main health condition to affect the replaces them with a special brace that the child teeth is DENTAL CARIES, or cavities. A cavity is a hole wears for two months. Some children require fur- through the enamel that allows BACTERIA to enter ther bracing at night for another few months. the tooth. The bacteria eat away at the tooth’s After treatment, the foot looks and functions as inner structure until reaching the pulp, at which normal. point the cavity causes PAIN. A dentist can plug a See also BIRTH DEFECTS; BONE; GENETIC DISORDERS; cavity with a resin filler to stop the process and MUSCLE. preserve the tooth. Other health conditions that can affect the teeth include GINGIVITIS, PERIODONTAL teeth Calcified formations that grow from the DISEASE and traumatic injury. gums in the MOUTH. The teeth are necessary for See also HALITOSIS; GLOSSITIS; SIALADENITIS. 358 tendonitis 359 temporomandibular disorders A group of con- Risk Factors and Preventive Measures ditions in which there is INFLAMMATION and often Stress is often a significant factor in the circum- degeneration of the temporomandibular JOINT, the stances that contribute to temporomandibular dis- large joint that connects the lower jaw (mandible) orders, particularly with bruxism and clenching of to the temporal BONE of the cranium. There are the jaw, which causes irritation of the muscles and numerous possible causes for temporomandibular other tissues in the joint area. Many people find disorders, ranging from a CONGENITAL ANOMALY of their symptoms improve with a combination of structure (such as uneven bite) to OSTEOARTHRITIS direct treatment (such as NSAIDs and heat) and and grinding the TEETH (bruxism). indirect approaches such as MEDITATION or other stress-reduction techniques. These measures can Symptoms and Diagnostic Path reduce MUSCLE tension. The symptoms of temporomandibular disorders See also CHRONIC PAIN. include tendon A tough, fibrous band of connective tis- • inability to fully open the MOUTH sue that joins MUSCLE to BONE. A tendon originates • locking of the jaw when open in the muscle. Like muscle, tendons have a rich BLOOD and NERVE supply. At its other end the ten- • clicking sounds or sensations when chewing don inserts into the bone. Mineralization at the • PAIN in the temporomandibular joint insertion point creates a contiguous flow of tissue • chronic HEADACHE from muscle to bone. The largest tendon in the body is the ACHILLES TENDON, which joins the mus- The diagnostic path begins with a comprehen- cles of the calf to the bone of the heel. The most sive examination of the head and mouth. Some- common health conditions involving tendons are times the doctor determines the cause is primarily TENDONITIS (INFLAMMATION of a tendon) and tendon dental, such as uneven bite, and refers the person rupture (a tear in the tendon). to a dentist for evaluation and treatment. Deterio- See also BURSA; LIGAMENT; PATELLOFEMORAL SYN- ration and inflammation of the joint are medical DROME; ROTATOR CUFF IMPINGEMENT SYNDROME. problems the doctor can attempt to treat. X-RAY can show whether there is a misalignment of the tendonitis INFLAMMATION of a TENDON. Tendonitis joint structures or deterioration of the bones. most often occurs as an overuse injury. Overuse There is usually no need for additional diagnostic causes the fibers of the tendon to stretch and procedures unless the doctor feels the need to rule tear, leaving microscopic injuries throughout out other causes for the symptoms. the tendon. Occasionally calcium deposits develop in a tendon. The injury activates the IMMUNE Treatment Options and Outlook RESPONSE, which in turn initiates the inflammatory Treatment for temporomandibular disorders may response. include medications such as NONSTEROIDAL ANTI- The main symptoms of tendonitis are PAIN at INFLAMMATORY DRUGS (NSAIDS) to relieve inflamma- the tendon’s insertion point on the BONE and tion and pain, heat or cold to the joint, dental swelling over the site. Tendonitis most commonly splints or other devices to realign the bite, and occurs at the wrist, elbow, shoulder, knee, dental repairs, if necessary. Temporomandibular ACHILLES TENDON, and heel. Within the first 24 disorders tend to be chronic. Many people put up hours, RICE (rest, ice, elevation, and compression) with the discomfort for a considerable time before is the most effective therapeutic approach. NON- seeking medical care, by which time joint deterio- STEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS) help ration or other problems may be serious. Treat- relieve PAIN and inflammation. Most tendonitis ment may take time to be effective. In rare improves within 72 hours and completely heals in circumstances, usually when injury or congenital two to three weeks with appropriate treatment. anomaly causes a structural problem with the See also ACHILLES TENDON INJURY; ADHESIVE CAP- joint, surgery may be necessary. SULITIS; EPICONDYLITIS; PATELLOFEMORAL SYNDROME; 360 The Musculoskeletal System

ROTATOR CUFF IMPINGEMENT SYNDROME; SHIN SPLINTS; causes for the symptoms, particularly in adults for SYNOVITIS. whom the symptoms are new. Treatment aims to relax and lengthen the neck muscles on the torticollis Extended contraction of the muscles in affected side through PHYSICAL THERAPY as well as the neck, pulling the head down and to the side. self-performed stretching and FLEXIBILITY exercises Torticollis, also called wryneck, may be present at (for adults). Rarely, surgery is necessary to release birth or acquired. Acquired torticollis may develop the muscles. Baclofen, an anticholinergic medica- after injury to the nerves or muscles of the neck tion that blocks neurotransmitters essential for though sometimes the doctor is unable to deter- MUSCLE contraction, provides relief for some peo- mine the cause. Often the neck muscles are stiff. In ple. MASSAGE THERAPY and sometimes cervical trac- addition to the altered posture of the head and tion help acquired torticollis that becomes chronic. neck, other symptoms of torticollis include Early treatment usually corrects congenital torti- HEADACHE and restricted ability to move the head. collis. The diagnostic path includes a comprehensive See also CEREBRAL PALSY; NEUROTRANSMITTER; NEUROLOGIC EXAMINATION to rule out other possible SPASM; TALIPES EQUINOVARUS. PAIN AND PAIN MANAGEMENT

PAIN is an unpleasant, subjective sensation associated with numerous health conditions and circumstances. Pain spe- cialists are physicians who have additional education and training in the treatment and management of pain. Pain specialists may be anesthesiologists, internists, neurologists, orthopedic surgeons, psychiatrists, or physiatrists.

The entries in this section, “Pain Management,” transition from the PERIPHERAL NERVOUS SYSTEM to are about pain and its treatment. Entries dis- the central NERVOUS SYSTEM. cussing health conditions for which pain may be a The first structure within the brain to receive symptom appear in the system section appropriate the nerve signals of pain is the thalamus. The for the condition. thalamus further filters the impulses and takes rudimentary action to address certain aspects of The Mechanisms of Pain the pain response. It initiates reflex reactions for Pain can be a potent symptom, pointing to a sig- pain signals that require it, dissipates some nificant injury or disease process within the body. impulses that it interprets as meaningless, and Pain can also be a measure of HEALING, marking sends the remainder on to the cerebral cortex for the body’s progress toward wellness. And pain can more sophisticated interpretation. Neuron activity be an indicator of dysfunction, persisting when in the cerebral cortex determines how the person there is no apparent reason for its existence. At a will perceive the pain—whether the signals are primal level, pain is a sensory survival mecha- indeed pain and what it will feel like (sharp, dull, nism. It tells the body to rapidly move to avoid its stabbing) and how intense it will be (mild, moder- source or cause. The SPINAL CORD conveys pain sig- ate, severe). Pain generally results in one of two nals directly to several regions of the CENTRAL actions: removing the involved body part from the NERVOUS SYSTEM, such as the thalamus, that regu- source of the pain or limiting the movement of late the body’s REFLEX responses. the body part. The message of pain begins with specialized molecules, called nociceptors, that line the den- Traditions in Medical History drites of peripheral neurons. Dendrites are For thousands of centuries people have used nat- branchlike networks that extend from a NEURON to ural substances to relieve pain. Willow bark con- capture electrical signals and convey them to the tains salicylic acid, the basis of aspirin. Oil of NERVE body, which focuses them into a more wintergreen (Gualtheria procumbens) also contains organized nerve impulse. Nerve impulses travel salicylic acid. Opium occurs naturally in the along chains of neurons (nerve fibers) until they poppy species Papaver somniferum. The leaves of reach the large nerve clusters, the dorsal ganglia, the coca plant (Erythroxylum coca) contain COCAINE. that feed into the spinal cord. The dorsal ganglia Many modern analgesics contain synthetic prepa- further sort and focus nerve impulses, blocking rations or derivations of these potent pain reliev- many from continuing to the BRAIN but allowing ers. Some substances ancient healers turned to for passage for others. At this point the pain messages pain relief had very narrow margins of safety:

361 362 Pain and Pain Management mandrake, henbane, and hemlock, among others. genetic factors that come into play as well, such as Today’s pharmacopoeia recognizes these sub- the function or dysfunction of the genes that reg- stances as dangerous poisons that have no thera- ulate the production and activity of cytochrome peutic applications. Other approaches to pain enzymes. The LIVER produces these enzymes, such relief before the 20th century included ALCOHOL as CYTOCHROME P450 (CYP450) ENZYMES, that are and the literal “bite the bullet.” integral to how the body metabolizes numerous The first pharmaceutical preparation for pain medications, including analgesics. Understanding relief was aspirin, which came into use at the end pain pathways has helped doctors understand of the 19th century. Pharmaceutical preparations how analgesics interfere with those pathways, of OPIATES and other pain relievers soon followed. allowing clinicians to select the analgesics with the Dozens of ANALGESIC MEDICATIONS are now available highest likelihood for relieving the pain. that can effectively treat and often prevent pain Researchers know, too, that the body releases along the full spectrum of severity. numerous biochemicals after injury (traumatic or surgical) that influence how nociceptors perceive Breakthrough Research and Treatment Advances stimuli. The body also releases biochemicals such Research in the 1990s provided breakthroughs in as endorphins and enkephalins that act at the lev- knowledge and understanding of pain mecha- els of both peripheral nociceptors and central nisms and, accordingly, for new ways to provide (spinal cord and brain) neuroreceptors. Research pain relief. Researchers know, for example, that is under way to develop medications that stimu- women and men experience pain differently, rais- late release of endorphins and enkephalins as well ing the probability that hormones play a key role as to target other mechanisms of the pain pathway in pain perception and tolerance. There are to relieve pain with lowered risk of side effects. A

acute pain PAIN that arises suddenly and is often (NSAIDS) block the release of PROSTAGLANDINS, bio- intense or severe in its quality. Acute pain signals chemicals the IMMUNE RESPONSE generates that acti- injury to the body resulting from trauma, surgery, vate both the inflammatory response and NERVE or disease process that damages tissue. Acute pain transmission of pain signals. Narcotic analgesics, is short lived (typically less than one month) and such as morphine and oxycodone, bind to recep- goes away when the condition causing it improves tors in the brain, preventing the release of neuro- or goes away. Doctors may use the term EUDYNIA to transmitters. As a result the pain impulse cannot identify acute pain. Pain that does not go away be transmitted and the brain does not perceive when the underlying cause improves becomes pain. CHRONIC PAIN, or MALDYNIA. COMMON CAUSES OF ACUTE PAIN Chest pain may indicate heart attack or ADHESIVE CAPSULITIS APPENDICITIS pulmonary embolism and requires ATHLETIC INJURIES BARRETT’S ESOPHAGUS emergency medical evaluation. BONE SPUR BURNS BURSITIS cancer People often describe acute pain as sharp, stab- corneal ABRASION CYSTITIS bing, or burning. Physical signs that accompany DENTAL CARIES DIVERTICULAR DISEASE acute pain include DYSMENORRHEA EPICONDYLITIS EPIDIDYMITIS FRACTURE • rapid BREATHING (TACHYPNEA) GALLBLADDER DISEASE HEADACHE • rapid HEART RATE (tachycardia) HERNIATED NUCLEUS PULPOSUS HERPES ZOSTER ILEUS KNEE INJURIES • elevated BLOOD PRESSURE MASTITIS NEPHROLITHIASIS • clammy SKIN NEURITIS ORCHITIS • dilated pupils OSGOOD-SCHLATTER DISEASE OTITIS media PANCREATITIS PEPTIC ULCER DISEASE Severe acute pain may cause loss of CONSCIOUS- PERICARDITIS PERITONITIS NESS; severe pain requires prompt or emergency PLEURISY SCIATICA medical evaluation. Chronic and terminal health SHIN SPLINTS SICKLE CELL DISEASE conditions may also cause episodes of acute pain. SINUSITIS SPRAINS AND STRAINS Treatment for acute pain is two-pronged, tar- STREP THROAT SUNBURN geting the pain as well as the underlying cause. surgery SYNOVITIS ANALGESIC MEDICATIONS are generally effective for TENDONITIS URETHRITIS pain relief. There are numerous types of analgesic wounds medications; doctors often prescribe or recom- mend them in combinations that target the nature Nonmedication methods also provide relief and sometimes the cause of the pain. For exam- from acute pain. Sometimes just resting the ple, the NONSTEROIDAL ANTI-INFLAMMATORY DRUGS affected area calms irritation and discomfort. 363 364 Pain and Pain Management

Wrapping or bracing an injured JOINT or limb pro- behaviors and degree to which the child responds vides support during activity. Ice to the affected to comforting measures to help caregivers assess area soothes INFLAMMATION, slowing the release of the level of pain the child is experiencing. prostaglandins and other biochemicals that stimu- Because a child’s body is not fully developed, it late the pain response. Heat and therapeutic mas- metabolizes medications differently from that of sage help tight, stiff muscles relax and improves an adult’s body. Analgesic medications to relieve BLOOD flow to the HEALING area. Alternating heat pain thus have different therapeutic levels, dura- and ice can provide substantial relief for muscu- tions of effectiveness, and toxic levels. Some anal- loskeletal pain. gesics have undergone clinical study to quantify See also ANESTHESIA; DERMATOME; EYE PAIN; MAS- their actions and side effects in children though SAGE THERAPY; NEURORECEPTOR; PATIENT CONTROLLED many have not. Pediatric dosing for analgesics is ANALGESIA (PCA); TERMINAL PAIN. sometimes imprecise and tends to err on the side of undertreating pain in children. Children who aging, changes in pain perception that occur have significant or CHRONIC PAIN should receive with The perceptions of PAIN and the responses care from pediatric pain specialists to ensure that to pain relief methods change across the spectrum they receive adequate pain relief. of age. A long-held belief is that infants experi- ence pain only in the most rudimentary fashion; Pain in the Elderly current research shows that infants experience The number of peripheral sensory receptors grad- nearly the same range and nature of pain as do ually diminishes with aging, affecting the PERIPH- adults. They also have the capacity to remember ERAL NERVOUS SYSTEM’s ability to detect pain and pain experiences. Children of all ages have sur- convey pain signals to the central nervous system. prisingly sophisticated understanding of pain and This can result in more serious injury before there pain relief. At the other end of the spectrum, for is adequate stimulus to avoid the situation. An about a third of people over age 60 pain is a daily older person may experience scalding and damage experience. But as the body ages its ability to to the SKIN from water that is too hot, for example, respond to ANALGESIC MEDICATIONS and other before nociceptors detect the danger. Sensory approaches to pain relief changes. So does its abil- receptors, including nociceptors, are also more ity to generate its own natural pain relievers, susceptible to dysfunction and may overrespond endorphins and enkephalins. to stimuli, resulting in MALDYNIA. Other changes that take place in the body affect Pain in Infants and Children the METABOLISM of drugs, which in many circum- Though an infant’s NERVOUS SYSTEM continues to stances means that less of the medication is neces- develop after birth, the mechanisms for nocicep- sary to achieve the desired therapeutic effect. The tion (stimulation of nerves to transmit pain signals body may take longer to clear the medication, to the CENTRAL NERVOUS SYSTEM) are capable of meaning doses should be farther apart (such as function at about 28 weeks of gestational age—12 every six hours instead of every four hours) or that weeks before a full-term delivery. Though infants the DRUG may more quickly accumulate to a level of under age 12 months cry when in pain and toxicity. Changes in gastric acid production and exhibit reflexive behaviors to avoid painful stim- STOMACH function make the lining of the stomach uli, it is difficult to determine the severity of the more vulnerable to damage from highly acidic pain. Young children (ages 1 to 5 years) are able to products, increasing the risk of bleeding with acidic assess the severity of their pain and convey this to medications such as ibuprofen and aspirin. Because caregivers. A common pain scale for young chil- of this the American Geriatric Society recommends dren is the Wong-Baker Faces Scale, which uses a that most people over age 65 take acetaminophen series of smiling-to-frowning faces for children to as the first choice for mild to moderate pain relief. describe how their pain feels. Other pain assess- Because older people are more likely to have ment scales make use of the child’s physical health conditions that require regular medications, alternative methods for pain relief 365 the risk for ADVERSE REACTION, undesired side effects, such as those related to pain. Many health-care and DRUG INTERACTION is high. Among those condi- centers provide biofeedback training; the person tions are many that cause chronic pain, such as then uses biofeedback techniques when needed. OSTEOARTHRITIS, SCIATICA, and gout, increasing the Biofeedback is especially effective for helping avert need for pain relief methods. It is important for the the onset of migraine and MUSCLE tension older person to receive adequate pain relief, espe- headaches, relaxing tense muscles that contribute cially from chronic pain, which sometimes means to muscle SPASM and pain, and relieving stress. taking narcotic pain relievers. Health experts rec- ommend methods that minimize the use of anal- Hypnosis gesic medications, such as MASSAGE THERAPY, heat Hypnosis is a state of deep relaxation in which a and cold, ACUPUNCTURE, BIOFEEDBACK, and relaxation person is especially receptive to suggestions the techniques such as MEDITATION. Regular physical hypnotherapist makes. These suggestions may exercise, such as walking, increases the body’s pro- include visualization and relaxation techniques to duction of endorphins and enkephalins, amino apply in specific circumstances, such as when feel- acids that function as natural pain relievers. ing tense or that pain is starting. Some people are See also AGING, EFFECTS ON DRUG RESPONSE AND able to practice self-hypnosis, which is particularly DRUG METABOLISM; ALTERNATIVE METHODS FOR PAIN helpful for stress reduction with chronic pain con- RELIEF; EFFICACY; EUDYNIA; NARCOTICS; NONSTEROIDAL ditions. ANTI-INFLAMMATORY DRUGS (NSAIDS); OVERDOSE. Chiropractic alternative methods for pain relief Methods for Chiropractic manipulation of the neck and back treating PAIN (typically CHRONIC PAIN) that are out- (spine) can relieve muscle tightness, improve FLEX- side the parameters of conventional approaches IBILITY, and restore function. The foundation of such as ANALGESIC MEDICATIONS. Among the more chiropractic is realignment of the spine to restore common alternative methods for pain relief are balance to the body. Chiropractic care requires vis- ACUPUNCTURE, BIOFEEDBACK, HYPNOSIS, CHIROPRACTIC, its to a chiropractor; the number and frequency of MAGNET THERAPY, and MASSAGE THERAPY. Herbal and visits depend on the health condition. Chiropractic botanical products may also bring relief from pain manipulation is particularly effective for condi- associated with specific conditions. tions such as chronic low back pain, chronic neck pain, REPETITIVE MOTION INJURIES, and other muscu- Acupuncture loskeletal pain. The chiropractor also teaches In 1997 the US National Institutes of Health (NIH) methods to minimize injury through proper pos- released a consensus statement regarding acupunc- ture, movement, and stretching. ture. The statement cites these circumstances in which studies demonstrate acupuncture’s effective- Magnet Therapy ness in relieving pain: after dental surgery, men- Magnetic energy affects the flow of fluids and strual cramps (DYSMENORRHEA), FIBROMYALGIA, electrolytes (salts) through the cells of the body. myofascial pain syndrome, OSTEOARTHRITIS, chronic Though research studies show conflicting results low BACK PAIN, CARPAL TUNNEL SYNDROME, HEADACHE, as to the effectiveness of static magnets (magnets and tennis elbow. In the Eastern tradition, or magnetic devices worn on the body), pulsed acupuncture works by unblocking the pathways of electromagnetic therapy is an effective therapeutic chi, the energy of life. In the Western tradition, method physical therapists and physiatrists use. researchers postulate that acupuncture acts on Static magnets may provide a less intense effect. nociceptors and PERIPHERAL NERVES. People who have implanted electronic devices such as a PACEMAKER should not use static magnets Biofeedback or have pulsed electromagnetic therapy because Biofeedback allows a person to influence the per- these treatments may affect the device’s proper ceptions and responses of certain body functions functioning by altering its electromagnetic field. 366 Pain and Pain Management

Massage Therapy pain by acting on neuroreceptors in the brain. Therapeutic massage relaxes stiff muscles and Other analgesics have multiple effects, such as increases the flow of BLOOD. These effects improve NONSTEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS), flexibility and movement, and bring pain-relieving which also relieve INFLAMMATION and FEVER, and chemicals (the body’s own substances or medica- acetaminophen, which also relieves fever. Other tions in the blood circulation) to the area. Massage kinds of medications primarily prescribed for other therapy is effective for many types of pain and therapeutic uses are effective for pain relief in cer- helps relieve the emotional stress that often tain pain syndromes. Some ANTIDEPRESSANT MEDICA- accompanies conditions of chronic pain. TIONS, antiseizure medications, beta-antagonist medications (beta-blockers), and calcium channel Herbal and Botanical Remedies antagonists (calcium channel blockers) can pro- Numerous herbal and botanical remedies have vide relief from and often can prevent NEUROGENIC pain-relieving actions. Some are effective for spe- PAIN (pain arising from injury to nerves) and cific discomfort, such as DONG QUAI for dysmenor- migraine HEADACHE. rhea (menstrual cramps) and FEVERFEW for migraine headaches. These herbs appear to block Routes of Administration the release of PROSTAGLANDINS, substances the body Analgesic medications are available in numerous produces that cause INFLAMMATION. Research stud- formulations for several different ROUTES OF ADMIN- ies also support the effectiveness of CHONDROITIN ISTRATION. The most common route of administra- and GLUCOSAMINE, chemical compounds that occur tion for analgesics is oral—pills, tablets, capsules, naturally in the body. These compounds block the and liquids taken by mouth. Some medications actions of enzymes that destroy connective tissue. absorb poorly through the gastrointestinal tract so Taken as nutritional supplements, chondroitin and are far more effective in other forms such as trans- glucosamine may be as effective as NSAIDs for dermal patch, suppository, and injection. Topical relieving the inflammation of osteoarthritis that medications applied to the SKIN may relieve MUSCLE causes pain. Herbal and botanical products for and JOINT pain. The choice of both the analgesic pain relief may interact with OVER-THE-COUNTER medication and its route of administration affects (OTC) DRUGS and prescription medications, notably how rapidly and how completely the medication NSAIDS. relieves pain. Oral The processes of digestion—how much Benefits and Risks of and what kinds of food are in the STOMACH and Alternative Pain Relief Methods gastrointestinal tract as well as individual varia- Some alternative pain methods can interact or tions in the digestive process—affect how rapidly interfere with conventional therapies the doctor oral medications enter the BLOOD circulation. Most prescribes or recommends. It is important to dis- oral analgesics begin to have an effect within 20 to cuss alternative methods with the doctor to effec- 45 minutes and stay in the bloodstream at a thera- tively integrate them with other therapeutic peutic level for two to six hours. Some long-acting approaches and to minimize the risk for complica- formulations are effective for 12 to 24 hours. tions, including worsening of the condition or Transdermal patch Some products are avail- interactions with other methods. able in transdermal patches, small adhesive See also CRANIOSACRAL MASSAGE; MEDICINAL HERBS patches placed on the surface of the skin, which AND BOTANICALS; MIND–BODY INTERACTIONS; OSTEO- get the medication rapidly into the blood circula- PATHIC MANIPULATIVE TREATMENT (OMT); REFLEXOLOGY; tion via absorption through the skin. The trans- REIKI; SAME; YOGA. dermal patch is also effective for delivering sustained-release medication (medication that analgesic medications Drugs, products, and slowly absorbs over a planned period of time, preparations that relieve PAIN, often called pain often 48 to 72 hours). relievers. Some kinds of analgesic medications, Topical Topical medications are also applied to such as OPIATES and other NARCOTICS, solely relieve the surface of the skin though are not absorbed analgesic medications 367 into the blood circulation to any significant extent. PCA and intrathecal analgesia offer highly Topicals come as creams (water-based), ointments effective pain control for ACUTE PAIN after surgery (oil-based), gels, sprays, and liquids. Topical anal- as well as severe pain due to chronic or terminal gesics may contain aspirin or other forms of salicy- conditions. Continuous infusion of local anesthe- late, local anesthetic such as lidocaine (which sia is especially effective after major surgery, numbs the skin’s surface), hydrocortisone (an reducing the amount of narcotic analgesics neces- anti-inflammatory DRUG to reduce swelling at the sary to provide adequate pain relief. Continuous skin’s surface), and capsaicin. infusion of local anesthesia also allows greater Suppository Rectal suppositories package the comfort for coughing, deep BREATHING, and return medication in a soft, waxy capsule that, after to mobility, factors that are essential for HEALING as insertion into the RECTUM, melts to release the well as to prevent postoperative complications. analgesic. The rectal mucosa (mucous membrane Injections can cause discomfort and bleeding at lining of the rectum) has a rich blood supply that the injection site. rapidly draws in the medication. Analgesics in suppository form are especially effective when How These Medications Work nausea is a problem and for people who have dif- Analgesic medications work by altering how the ficulty swallowing. NERVOUS SYSTEM processes pain messages. They may Injection The more potent analgesics, notably narcotics, are poorly absorbed through the gas- • raise the pain threshold (the point at which trointestinal tract and thus are available in nociceptors perceive stimuli as painful); aceta- injectable forms (shots). An injection may be minophen functions in this way • block production of PROSTAGLANDINS and other • intravenous (directly into a VEIN), which pro- biochemicals that sensitize nociceptors and acti- vides the most rapid (usually seconds) though vate the inflammatory response; NSAIDs func- short-term (30 minutes to 2 hours) pain relief tion in this way • intramuscular (into a muscle), which provides • bind with neuroreceptors in the BRAIN to alter fast relief (within 10 minutes) that can last the brain’s interpretation of pain signals; opi- three to four hours ates and other narcotics function in this way • subcutaneous (into the layer of fatty tissue • alter the balance of peripheral and central beneath the skin), which provides prompt relief (brain) neurotransmitters; antidepressants and (within 20 to 30 minutes) but slower release of antiseizure medications function in this way the medication into the blood circulation for analgesia that can last six to eight hours • change the ionization of cells to affect how molecules pass through them; beta blockers • PATIENT-CONTROLLED ANALGESIA (PCA), in which and calcium channel blockers function in this intravenous medication flows steadily into a way vein (intravenous administration) via a pump that regulates the amount of medication, either Taking analgesic medications properly is as as at a preset rate or by patient demand (when important as the correct choice of drug when it the person presses the button to release more comes to effective pain relief. Some analgesics medication) need to be taken on a scheduled basis because • continuous infusion of local anesthesia, which they are more effective when they reach a steady infiltrates tissue in a specific area with an anes- THERAPEUTIC LEVEL in the blood. These medications thetic agent that relieves pain by numbing the generally provide sustained pain relief for short- nerves such as after a surgical OPERATION term acute pain due to trauma or surgery and for • intrathecal analgesia, in which the pain special- long-term CHRONIC PAIN. Other analgesics are more ist inserts a thin catheter into the space around effective when taken as needed, often indicated as the SPINAL CORD that delivers the analgesic in “prn” in the doctor’s instructions. These medica- somewhat the same fashion as PCA tions generally cover mild to moderate acute pain 368 Pain and Pain Management and breakthrough pain with chronic conditions or Risks and Side Effects during recovery from injury or surgery. Risks and side effects vary according to the med- ication. It is possible to have an ALLERGY to any NARCOTICS AND ADDICTION analgesic, creating the potential for HYPERSENSITIV- Many people, including doctors, are fearful of ITY REACTION. Though OVERDOSE is possible with any the potential for addiction with long-term use of analgesic, it is a particular risk with aspirin, aceta- NARCOTICS (OPIATES). However, numerous studies minophen, and NSAIDs. People are more likely to show that addiction is very rare, affecting fewer self-medicate with these drugs and to take multi- than 1 percent of people who take opiates for ple products that contain these drugs as ingredi- severe CHRONIC PAIN. Pain alters the mechanisms ents without recognizing the cumulative amount in the BRAIN that respond to opiates such that exceeds safety. These drugs also have a lower these mechanisms do not interpret the effect of threshold for hepatotoxicity (damage to the LIVER) the opiate as producing pleasure (a key factor in and renal toxicity (damage to the KIDNEYS), and addiction). As well, addiction involves a combi- can cause irreversible LIVER FAILURE or RENAL FAIL- nation of physical and emotional factors that typ- URE even when taken at recommended dosage lev- ically are not present in severe pain. The els. Though many people worry about overdose unwarranted fear of addiction prevents many with narcotics (opiates), it is far less of a risk. people from taking or receiving enough medica- However, inappropriate use of narcotics has high tion to relieve their pain. risk for addiction. Aspirin and NSAIDs also are irritating to the gastrointestinal tract and may cause bleeding. Therapeutic Applications Medications such as beta-blockers, calcium Aspirin, acetaminophen, and over-the-counter channel blockers, and antiseizure medications NSAIDs are the most widely used medications in have particular risks associated with these classifi- the United States. They have numerous therapeu- cations of drugs. Though people taking these tic applications for mild to moderate relief from drugs for their primary intended purpose (cardio- pain, inflammation, and fever. Doctors generally vascular conditions or seizure disorders, respec- move to prescription medications when OVER-THE- tively) are generally well aware of these risks, COUNTER (OTC) DRUGS are not effective or when the people taking them for pain relief may not recog- nature of the pain is such that it exceeds their nize warning signs of adverse reaction. It is impor- ability to provide relief (such as after surgery or tant to weigh the potential benefits and risks of significant injury). As knowledge and understand- taking these drugs for pain relief. Analgesic med- ing about the mechanisms of pain grow, doctors ications also interact with numerous other med- are increasingly able to structure pain relief ications, including OTC products and herbal approaches that integrate different kinds of drugs remedies. for optimal effectiveness. The therapeutic applica- See also ALTERNATIVE METHODS FOR PAIN RELIEF; tion of many analgesics is highly individualized. ANESTHESIA; NEURORECEPTOR; SCHEDULED DRUGS. C–E

chronic fatigue syndrome A constellation of joints; headaches; difficulty sleeping or unrest- symptoms that exist within a framework of pro- ful sleep; feeling of overwhelming exhaustion found, persistent fatigue and generalized PAIN. Nei- after physical exertion. ther the fatigue nor other symptoms improve with rest. Chronic fatigue syndrome often debilitates In addition to these core symptoms, most peo- those who have it and confounds the doctors try- ple have numerous other symptoms that may ing to treat them. Researchers have as yet been include unable to identify clear pathologic (disease process) reasons that account for the symptoms of • ABDOMINAL PAIN chronic fatigue syndrome. Proposed causes • CHEST PAIN and shortness of breath include viral INFECTION (such as with EPSTEIN-BARR • chronic COUGH VIRUS or human herpesvirus 6), HYPERSENSITIVITY • NAUSEA, gastrointestinal discomfort, and DIAR- REACTION (ALLERGY), autoimmune disorder or other RHEA IMMUNE SYSTEM dysfunction, hormonal imbalance, chronic intermittent HYPOTENSION (low BLOOD PRES- • night sweats SURE), subclinical ANEMIA, and HYPOGLYCEMIA (low • DEPRESSION, anxiety, or panic attacks blood sugar). In many people chronic fatigue syn- • jaw pain drome appears after a serious viral infection or • earaches after an event that causes significant stress. • “pins and needles” sensations Symptoms and Diagnostic Path • dizziness In many people, the initial symptoms of chronic fatigue syndrome are those of a viral infection There are no diagnostic procedures that define such as INFLUENZA. But the symptoms do not go chronic fatigue syndrome. Rather, the doctor away after the typical timeline for such an infec- orders certain diagnostic tests to rule out other tion. Because ongoing symptoms are widely vari- potential causes for the symptoms. These include able and often without apparent physical cause, BLOOD tests to measure thyroid HORMONE levels, medical experts have established two basic criteria blood cell types and counts, electrolytes, globulins, for a diagnosis of chronic fatigue syndrome. For and GLUCOSE levels in the blood circulation. The six months or longer the person must have doctor may desire additional blood tests and uri- nalysis. Abnormal findings point in a different • severe, chronic fatigue for six months or longer clinical direction; a diagnostic criterion for chronic with diagnostic evaluation unable to find a fatigue syndrome is that such routine tests are medical reason for the fatigue normal. • four or more of the eight additional key symp- Diagnostic imaging procedures such as MAG- toms: sore THROAT, MUSCLE pain, tender LYMPH NETIC RESONANCE IMAGING (MRI) and COMPUTED nodes, noticeable difficulty with concentration TOMOGRAPHY (CT) SCAN may rule out other sus- and short-term memory; pain in numerous pected conditions though do not help the doctor 369 370 Pain and Pain Management reach a diagnosis of chronic fatigue syndrome. have the disorder, chronic fatigue syndrome is a Because the length of time the person experiences long-term condition that does eventually improve symptoms is a crucial element of the diagnosis, the or go away. The timeline for improvement is diagnostic journey is often frustrating. widely variable though typically spans several years. Many communities have SUPPORT GROUPS in Treatment Options and Outlook which people who have chronic fatigue syndrome Because doctors do not know what causes chronic can share their experiences and concerns. fatigue syndrome, treatment targets symptoms and is generally a combination of approaches tai- Risk Factors and Preventive Measures lored to the individual’s responses and improve- Again because doctors do not know what causes ments. Treatment options include chronic fatigue syndrome, there are no specific measures to prevent it. Doctors diagnose chronic • low-DOSE ANTIDEPRESSANT MEDICATIONS, which fatigue syndrome in about four times as many may relieve pain as well as improve the quality women as men. For the most part chronic fatigue of sleep syndrome is relatively indiscriminate, affecting people across the spectrum of age and health status. • ANTIANXIETY MEDICATIONS, which may relieve symptoms of anxiety, panic attacks, abnormal See also AUTOIMMUNE DISORDERS; COGNITIVE FUNC- TION AND DYSFUNCTION; FIBROMYALGIA; GENERALIZED SKIN sensations, and dizziness ANXIETY DISORDER; LYMPH NODE; QUALITY OF LIFE; STIM- • ANTIHISTAMINE MEDICATIONS, which may relieve ULANTS. symptoms such as runny NOSE and nasal con- gestion chronic pain PAIN that persists longer than three • modafinil, a nonamphetamine stimulant med- months or beyond the point of HEALING for the ication doctors commonly prescribe to treat condition that causes it. Chronic pain is very com- NARCOLEPSY, which improves alertness and cog- mon, affecting the daily lives and activities of an nitive function in some people who have estimated one in six Americans—about 60 million chronic fatigue syndrome people. The most prevalent causes of chronic pain in the United States are low BACK PAIN, arthritis, • NONSTEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS), and HEADACHE. which may relieve JOINT pain and generalized Pain experts differ in their definitions of what discomfort constitutes chronic pain. Research in the past • daily physical activity at a level that is consis- decade has provided new understanding about the tent but does not trigger a worsening of fatigue mechanisms of functional and dysfunctional pain. or other symptoms Some pain specialists view all chronic pain as dys- functional because it no longer serves the purpose • alternative methods such as ACUPUNCTURE, of warning the body. In this view the pain itself BIOFEEDBACK, MASSAGE THERAPY, CRANIOSACRAL becomes the disorder, called MALDYNIA, and treat- MASSAGE, HYPNOSIS,REIKI, and therapeutic touch ment targets pain relief. • MEDITATION, relaxation techniques, and stress- Other pain specialists consider some kinds of relief methods chronic pain (that which accompanies chronic health conditions such as RHEUMATOID ARTHRITIS) to Treatment often but does not always relieve remain symptomatic rather than dysfunctional. symptoms enough to allow participation in the The pain persists because the underlying condition normal activities of living. For many people who that causes it persists or progresses. In this view have chronic fatigue syndrome, the fatigue is so treatment targets the underlying condition, which overwhelming that it prevents virtually any level often includes therapies to relieve pain as well as of activity despite treatment for other symptoms. the pathology of the condition and its other symp- Some people experience continued symptoms that toms. In rheumatoid arthritis, for example, treat- wax and wane in severity. For most people who ment attempts to slow the inflammatory process complex regional pain syndrome 371 that causes degeneration in the joints as well as to thetic NERVOUS SYSTEM, the functional division of relieve the pain of the degenerative changes. the nervous system that regulates BLOOD flow. Therapeutic methods for chronic pain typically Complex regional pain syndrome is typically combine various approaches to find those that are chronic (ongoing and long term) and often pro- most effective for the individual. The subjective gressive (symptoms worsen over time). It most nature and diverse causes of chronic pain often often develops in people who are between the mean effective relief comes through a process of ages of 40 and 60. trial and error. Generally lifestyle measures to maintain healthy body weight and optimal range Symptoms and Diagnostic Path of motion, such as daily physical exercise, are The symptoms of complex regional pain syndrome important for all types of pain. Exercise increases typically involve a limb, with the arm being more the body’s release of endorphins and enkephalins, common than the leg. In addition to pain, the amino acid structures that act as natural pain course of disease causes pathologic (abnormal) relievers. changes in the SKIN, MUSCLE, connective tissue, and BONE. Early symptoms include CONDITIONS IN WHICH CHRONIC PAIN IS COMMON ANKYLOSING SPONDYLITIS BURSITIS • severe burning pain that intensifies with slight CANCER CARPAL TUNNEL SYNDROME touch, even that of a breeze (a nociceptor dis- CERVICAL SPONDYLOSIS CHONDRITIS turbance called allodynia) CHRONIC FATIGUE SYNDROME chronic SINUSITIS • swelling in the affected arm or leg COMPLEX REGIONAL PAIN SYNDROME EPICONDYLITIS • increased HAIR and nail growth FIBROCYSTIC BREAST DISEASE FIBROMYALGIA • dry, thin skin that alternates between warm GOUT HIV/AIDS and cool to the touch without influence from INFLAMMATORY BOWEL DISEASE (IBD) interstitial CYSTITIS the external environment and may become IRRITABLE BOWEL SYNDROME (IBS)lowBACK PAIN cyanotic (bluish in color) or mottled (areas of migraine HEADACHE myofascial pain syndrome irregular color) NEUROGENIC ARTHROPATHY NEUROPATHY OSTEOARTHRITIS OSTEOMYELITIS • altered sweating (sometimes excessive, some- PATELLOFEMORAL SYNDROME REPETITIVE MOTION INJURIES times inadequate sweat production) RHEUMATOID ARTHRITIS SCIATICA SICKLE CELL DISEASE spastic CEREBRAL PALSY Symptoms change as the syndrome unfolds. SPINAL CORD INJURY TENDONITIS Later symptoms include UTERINE FIBROIDS uterine prolapse • severe burning pain affects larger area of the VAGINISMUS VULVODYNIA limb

See also ACUTE PAIN; OSTEOARTHRITIS. • diminished ability to move the limb • decreased hair and nail growth complex regional pain syndrome A chronic and • permanent changes in the skin’s texture and often progressive condition of severe PAIN. There color (often becomes mottled) are two types of complex regional pain syndrome: type 1 (also called reflex sympathetic dystrophy), • changes in bone structure and BONE DENSITY that are apparent on X-RAY in which there is no identifiable NERVE injury, and type 2 (also called causalgia), which follows signif- • TENDON contractions and muscle SPASM icant injury to a nerve. Type 2 is more common • muscle atrophy (wasting of muscle tissue) though the symptoms, treatment, and course of disease are similar for both types. Researchers do The diagnostic path is primarily clinical because not fully understand the development and pro- the symptoms are fairly distinctive, particularly gression of either type of this syndrome but when there is history of traumatic or surgical believe it results from dysfunction of the sympa- injury to the involved limb. STROKE or HEART 372 Pain and Pain Management

ATTACK may also be a precipitating event. The doc- gresses, permanent damage to the limb becomes tor may use X-ray, bone scan, nerve conduction extensive and may render the limb useless. In studies, and other procedures to assess the neuro- severe cases the syndrome spreads to involve muscular function of the limb. A comprehensive other parts of the body. NEUROLOGIC EXAMINATION can rule out other possible causes of pain or complicating factors. However, Risk Factors and Preventive Measures there are no conclusive diagnostic procedures for Though doctors know that type 2 complex this syndrome. regional pain syndrome, the more common type, develops after significant trauma to the limb, they Treatment Options and Outlook do not know what causes it to occur. Type 1 com- The earlier treatment begins, the better the out- plex syndrome is even more baffling because there look. Treatment may involve a blend of is no clear injury that precipitates symptoms. approaches, including Accordingly, there are no measures known to pre- vent this disorder. However, early diagnosis and • anti-inflammatory medications such as NONS- treatment can prevent the condition from pro- TEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS) or gressing, limiting the extent of permanent damage CORTICOSTEROID MEDICATIONS to reduce INFLAMMA- that occurs. TION and swelling See also LIVING WITH PAIN; MALDYNIA; QUALITY OF • tricyclic ANTIDEPRESSANT MEDICATIONS and anti- LIFE. seizure medications, which are often effective in relieving NEUROGENIC PAIN eudynia PAIN that exists as a symptom clearly associated with an underlying health condition or • TRANSCUTANEOUS ELECTRICAL NERVE STIMULATION circumstance and results from stimulation of noci- (TENS) ceptors (specialized sensors on the dendrites of • NEURAL BLOCKADE (NERVE BLOCK) for pain that does neurons that convey pain messages). Eudynia, not respond to noninvasive treatments also called ACUTE PAIN, is typically short lived. Such • RHIZOTOMY or sympathectomy (surgery to cut the pain is a common feature of injury and numerous nerve carrying the pain messages) for pain that disease processes and is the body’s signal that does not respond to other methods of relief something is wrong. Eudynia responds well to • medications to prevent bone loss treatment with ANALGESIC MEDICATIONS and non- medication methods such as rest, ice, compression • PHYSICAL THERAPY and MASSAGE THERAPY to main- (if appropriate), and elevation (if appropriate)— tain FLEXIBILITY and mobility the RICE approach. ACUPUNCTURE and NEURAL BLOCK- • heat or cold to sites of pain ADE (NERVE BLOCK) are other methods that provide • BIOFEEDBACK relief for pain due to traumatic injury or surgery. • ACUPUNCTURE Eudynia resolves as the underlying condition improves. Early treatment may arrest symptoms and pre- See also ANESTHESIA; CHRONIC PAIN; MALDYNIA; vent their progression. When the condition pro- NEURON; NOCICEPTOR. H

headache PAIN perceived as coming from the causes people to unknowingly tense their muscles, face and head. Headache is a common experience, is a key factor. The stress may be emotional, related with about 45 million adults in the United States to job or family issues, or the stress may be physical, having frequent headaches. There are numerous arising from lack of sleep, sitting too long in one types of headache resulting from various causes. position, going without eating, or loud noise. The Among them are tension headache, migraine tightened muscles aggravate nociceptors, the sen- headache, cluster headaches, sinus headache, and sory molecules that respond to intense stimuli, rebound headache. Headache may also indicate which generate nerve signals of pain. The irritated HYPERTENSION (high BLOOD PRESSURE), TRANSIENT muscles may also develop some INFLAMMATION, fur- ISCHEMIC ATTACK (TIA), or STROKE. Headache also is ther stimulating nociceptors. Researchers believe common with COLDS, flu, and FEVER. Very rarely biochemical factors, such as altered neurotransmit- headache may signal an INFECTION such as MENINGI- ter balances (which affect the function of neurons) TIS or an ANEURYSM or a tumor in the BRAIN. and increased production of PROSTAGLANDINS (which The nerves in the soft tissue of the head, neck, influence inflammation and changes in the walls of and face transmit the pain signals familiar as blood vessels), may also contribute to tension headache. There are no sensory nerves in the headaches by affecting the sensitivity of nocicep- brain or bones of the skull, even though headache tors. Tension headaches range in severity from mild pain often feels as though it comes from deep discomfort to pain severe enough to cause NAUSEA, within the head. Pain associated with events VOMITING, and disturbances of vision. Many tension within the brain, such as tumor or stroke, arises headaches go away when the stressful situation from the increase in pressure within the cranium ends. Others may last for several days or become (enclosure of the skull) these conditions cause. chronic (recurring). The pressure stimulates the network of nerves that interlace with BLOOD vessels at the base of the Migraine Headache brain. This NERVE and blood vessel network Migraine is the most common type of vascular extends into the soft tissue surrounding the skull, headache. About 28 million Americans experience magnifying the perception of pain. chronic migraine headaches. For many people the pain of migraine is debilitating. The conventional Sudden, severe headache or headache understanding of migraine is that the pain is a with stiff neck, high or prolonged FEVER, reaction to extreme changes (constriction and or blow to the head may signal a med- dilation) in the blood vessels that serve the head, ical emergency that requires urgent likely as a consequence of rapid fluctuations in evaluation from a doctor. neurotransmitters, prostaglandins, and other sub- stances that affect circulation. Recent research Tension Headache suggests there are genetic components to the Tension headaches are the most common type of mechanisms that regulate blood vessel constriction headache, resulting from MUSCLE tenseness in the and dilation in the head, postulating that defects shoulders, neck, and head. Stress, which often in genetic encoding (the protein messengers genes 373 374 Pain and Pain Management send to cells that direct their activities) cause the monal connection. Some women have persistent abnormal vessel activity. Migraines tend to run in migraines until pregnancy and then never have a families, which supports the premise of genetic migraine headache again. Other women develop involvement. migraines during pregnancy or after menopause. There are two types of migraine: Oral contraceptives (birth control pills), which are hormones, also influence migraine headaches, • Classic migraine begins with an aura—a sen- improving them in some women and worsening sory experience, such as seeing flashing lights them in others. The hormonal connection seems or smelling a particular odor that is not actually obvious but its precise nature remains elusive. present, that portends the arrival of the headache. Disturbances of vision, confused Cluster Headache thinking, and tingling in parts of the body such Cluster headache is a less common type of vascu- as the hands or feet may accompany the aura. lar headache in which a migraine-style headache Nausea and often vomiting may come next. recurs at about the same time of day for two to Within about 30 minutes the pain erupts, often four months. The pain of cluster headache affects beginning on one side of the head or around one side of the head and is typically severe. What the EYE. The pain may stay on one side of the will become a series of headaches begins suddenly, head or spread to the entire head. A classic often around one eye. The involved eye becomes migraine lasts 24 to 48 hours. red and swollen, and the same side of the NOSE • Common migraine lacks an aura though often often becomes congested. Each headache lasts 30 there are vision disturbances, confusion, nau- to 90 minutes and then goes completely away. A sea, and vomiting before the headache starts. person may go several months to several years The pain may start on one side of the head and between clusters. However, severe chronic cluster spread to both sides, or start with full involve- headache can occur in such a regular pattern that ment of the entire head. A common migraine there is very little break between the end of one may last three or four days. cluster and the start of the next. Cluster headache is more common in men and does not appear to Medications are the usual approach for recur- have a hereditary component. ring migraines. The most effective are those that prevent the migraine from unfolding. A class of Sinus Headache drugs called triptans offering a new approach to Sinus headaches result from the pressure of sinus migraine treatment became available in the early congestion. The pain typically emanates from the 1990s. Triptans (such as sumatriptan and front of the face, is more severe upon first waking zolmitriptan) work by binding with receptors on and when tipping the head downward, and the cells in arterial walls that selectively constrict includes POSTNASAL DRIP among its symptoms. arteries, preventing the fluctuations in dilation Sinus congestion may result from a cold, ALLERGIC and constriction that result in pain. The effective- RHINITIS (seasonal allergies), or sinus infection. The ness of the different triptan products is highly doctor should evaluate sinus headache that lasts individual, so often a period of trial and error is longer than three weeks or when there a thick, necessary to find the right match between person green or yellow discharge accompanies the and drug. Triptans also have potentially severe headache as these symptoms may indicate a bacte- side effects, including HEART ATTACK resulting from rial infection that requires treatment with ANTIBI- constricted CORONARY ARTERIES. People who have OTIC MEDICATIONS. CARDIOVASCULAR DISEASE (CVD) such as CORONARY ARTERY DISEASE (CAD) or ISCHEMIC HEART DISEASE Rebound Headache (IHD), or who have significant risk for CVD, should Rebound headache is an unpleasant circumstance not take triptans. that develops as a consequence of long-term use of Migraine headaches are most common in men- analgesic medications (more than twice a week on struating women, raising the probability of a hor- a fairly regular basis) to treat chronic headache. The headache 375 headache improves or goes away with the medica- • To what extent does the headache interfere with tion but then returns when the medication wears regular activities? off or the person does not take the medication. • Are there any disturbances of vision (such as Eventually the medication can no longer relieve flashing lights or double vision), awareness, the headache and often the headaches become alertness, sensory perception, ability to speak, more frequent and more severe. ability to move? Treatment for rebound headache requires a • Do there seem to be any particular triggers for shift to other methods for relieving pain, such as the headache, such as stressful situations, spe- ACUPUNCTURE or BIOFEEDBACK. The doctor may also cific foods, certain locations or activities? prescribe medications to prevent headaches, such as propanolol or isometheptene, and a triptan • Are there other symptoms such as fever, sinus medication to thwart a migraine at its early warn- congestion, stiff neck, nausea, vomiting? ing signs (such as an aura). It may take several • What methods and medications have been tried weeks to two months for the headaches to fully to relieve the headache? Are they unsuccessful, recede. Stress management methods such as MEDI- sometimes successful, or partially successful? TATION and YOGA help shift focus to controlling and healing the pain rather than on the pain itself. The doctor will also ask questions about any other health conditions and whether other family KEEP A HEADACHE JOURNAL members have chronic headache, migraine Doctors recommend people who have frequent headache, seasonal allergies, and AUTOIMMUNE DIS- headaches keep a journal that describes their ORDERS. The doctor typically performs a general symptoms in detail. This helps identify patterns medical examination including a basic NEUROLOGIC for how the headaches develop and what effects EXAMINATION and a basic OPHTHALMIC EXAMINATION. various pain relief measures have to relieve the Imaging procedures such as COMPUTED TOMOGRAPHY pain. (CT) SCAN and MAGNETIC RESONANCE IMAGING (MRI) may rule out rare causes for headache such as Symptoms and Diagnostic Path stroke or tumor. However, the doctor often can The symptoms of headache provide important make the diagnosis based on the symptoms and clues about the cause and potential treatment headache history. options. The doctor will want to know the follow- ing: Treatment Options and Outlook Most treatment approaches for chronic headache • How does the pain feel? Common descriptions combine medications and other methods to relieve of headache pain include sharp, dull, throb- symptoms when the headache occurs and prevent bing, stabbing, viselike. headaches from recurring. Relaxation techniques • How does the pain start? Some headaches start such as meditation and yoga can help lessen the as minor discomfort and increase to a level of effect of stress. Other methods in which the per- pain that interferes with activities. Some son learns to recognize indications that a headaches start suddenly with moderate to headache is coming on are often effective in stop- severe pain. ping the headache from unfolding. Biofeedback and HYPNOSIS may help a person halt a headache. • Where is the pain? Headache pain may be pri- Numerous prescription medications are available marily on one side of the head or face, involve to prevent headaches. the entire head and face, or involve only the Heat to the back of the neck and resting in a face or only the head. The pain may feel like it dark, quiet room are measures that often soothe encircles the head, is deep or along the surface headaches that do occur. Medication is the main- of the scalp, or comes from a specific location. stay of treatment for headache once it develops. • How long does each headache last and how Aspirin, acetaminophen, and NONSTEROIDAL ANTI- often do headaches occur? INFLAMMATORY DRUGS (NSAIDS) such as ibuprofen are 376 Pain and Pain Management

TYPES OF CHRONIC HEADACHES Type of Headache Characteristic Symptoms Treatment Approaches cluster severe migraine-like PAIN on one side of the medications and other methods to try to prevent the head or face cluster of headaches nasal congestion on the affected side medications and other methods to head off a headache headache recurs, usually daily, for a period as it is starting of weeks to months (a cluster) and then goes analgesics during the headache do not usually take away for a period of time effect quickly enough to be useful migraine aura (classic migraine) such as flashing lights rest in a quiet, dark room or other sensory activation before the caffeine headache itself begins NONSTEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS): vision, sensory, and cognitive disturbances ibuprofen, naproxen (classic and common migraine) beta-blockers: propanolol, atenolol moderate to severe pain often on one side calcium channel blockers: amlodipine, verapamil of the head ergot derivatives: ergotamine, dihydroergotamine, NAUSEA and VOMITING ergotamine with CAFFEINE inability to participate in regular activities triptans: almotriptan, eletriptan, naratriptan, rizatriptan, sumatriptan, zolmitriptan antidepressants: amitriptyline, fluoxetine, nortriptyline, paroxetine, sertraline isometheptene NARCOTICS: injection of morphine for severe pain rebound headache that returns as soon as the medications to prevent headache such as beta-blocker medication taken to relieve it wears off or isometheptene relaxation techniques and other nonmedication methods sinus pain along the cheek bones, around the eyes, ANTIBIOTIC MEDICATIONS for INFECTION in the jaw ANTIHISTAMINE MEDICATIONS for ALLERGIC RHINITIS pain is worse upon first waking up in the decongestant spray or drops morning and when tipping the head forward oral decongestant medications nasal congestion and postnasal drip tension steady, pressure-type pain that comes on over-the-counter analgesics: acetaminophen, aspirin, gradually NSAIDs often occurs during times of physical or antidepressants: amitriptyline, fluoxetine, nortriptyline, emotional stress paroxetine, sertraline may go away when source of stress ends relaxation and stress management methods frequent stretching and movement to change position ACUPUNCTURE MASSAGE THERAPY CHIROPRACTIC headache 377 often effective for relieving the pain of headache require treatment with antibiotic medications for once it develops. Severe headache of any type infection or ANTIHISTAMINE MEDICATIONS for allergic may require narcotic analgesic medications to rhinitis. Decongestant medications (nasal sprays, relieve the pain. The exception is cluster nasal drops, or oral forms) may help sinus headache, for which preventive measures are headache of either type. more effective because the headache, despite the severity of its pain, generally lasts a shorter period Risk Factors and Preventive Measures of time than it takes for analgesic medications to Risk factors for headaches include physical and achieve a therapeutic effect in the body. The herb emotional stress, low blood GLUCOSE from missing FEVERFEW, available as an over-the-counter dietary meals, exposure to environmental irritants such as supplement in the United States, is effective cigarette smoke, excessive CAFFEINE consumption, against migraines for some people. allergies or HYPERSENSITIVITY REACTION, foods that Medication is also the mainstay of prevention contain tyramines (such as red wine, smoked for migraines and cluster headache, though pre- meats, and hard cheeses), and MENSTRUATION in vention approaches are more effective for women. Preventive measures include relaxation migraine than cluster headaches. Medications that techniques and stress management methods, may prevent migraines and cluster headache avoiding known or suspected factors that precipi- when taken on a regular basis include propra- tate headache, and prophylactic (preventive) med- nolol, methylsergide, amitriptyline, valproic acid, ication. The right combination of approaches can verapamil, and lithium carbonate. Triptans taken significantly reduce the frequency and severity of at the first indication of migraine are effective for chronic headaches. many people in preventing the headache. Occa- See also ACUPUNCTURE; LIVING WITH PAIN; NEURAL- sionally a doctor may give an injection of narcotic GIA; NEURON; NEURORECEPTOR; STRESS AND STRESS MAN- analgesic such as morphine. Sinus headaches may AGEMENT. L–M

living with pain Approaches and methods for to weeks). BIOFEEDBACK, VISUALIZATION, and MEDITA- improving QUALITY OF LIFE when PAIN is part of daily TION are additional methods for coping with and living. For one in five Americans, pain is a daily managing pain. experience. Nearly 60 million people in the United See also ACUTE PAIN; CHRONIC PAIN; EUDYNIA; States have OSTEOARTHRITIS, 45 million experience HEADACHE; MALDYNIA; MASSAGE THERAPY; STRESS AND frequent headaches severe enough to interfere STRESS MANAGEMENT. with regular activities (28 million of them have chronic or recurrent migraine headaches), and 5 maldynia CHRONIC PAIN that exists without million have chronic low BACK PAIN. apparent organic or physical cause. The defining Living with pain requires an integration of med- characteristic of maldynia is that the PAIN does not ical and lifestyle methods. There are many kinds of activate specific pain receptors (nociceptors) or ANALGESIC MEDICATIONS, some of which provide gen- follow conventional pain pathways. Some eral pain relief and others that target specific kinds researchers believe maldynia represents a mal- of pain. Research over the past 10 years has pro- function of the BRAIN’s pain interpretation vided significant insight into the mechanisms of processes, likely an imbalance among brain neuro- pain, resulting in new classifications of drugs that transmitters. Other researchers believe maldynia intercede at different junctions along pain path- represents disturbances in the body’s pain sensory ways. ROUTES OF ADMINISTRATION such as transdermal mechanisms, perhaps changes at the level of the patches (SKIN patches) or long-acting oral formula- NEURON that alter the sensitivity of pain signals. tions can deliver a steady rate of pain medication, Maldynia is an extraordinarily frustrating con- smoothing out the ups and downs that accompany dition. Beyond the limitations on enjoying life other dosage forms such as short-acting tablets and that continual pain imposes, there are the psycho- pills. Though most people do not want to take med- logic ramifications of the perception that the pain ications on a regular basis, medications may be nec- is not real. Doctors who are unfamiliar with essary to slow a disease process (such as RHEUMATOID chronic pain syndromes may be suspicious of ARTHRITIS) or to alleviate enough pain to allow par- reported pain without apparent cause that persists ticipation in daily activities. despite efforts to resolve it and may dismiss the Daily physical exercise, such as walking, bene- person’s symptoms as “psychosomatic” or emo- fits nearly every condition in which there is pain. tional in its basis. Research suggests that though Physical activity stimulates the body to release emotions influence pain perception, this occurs endorphins, enkephalins, and other biochemicals through biochemical and physiologic pathways in that act as natural pain relievers or otherwise the body and the CENTRAL NERVOUS SYSTEM. influence the body’s inflammatory response and pain mechanisms. Regular activity also improves Symptoms and Diagnostic Path MUSCLE STRENGTH and JOINT FLEXIBILITY, helps main- The primary symptom of maldynia is pain that tain healthy body weight, and relieves stress. does not go away and has no apparent cause. Doc- Alternative methods such as ACUPUNCTURE and CHI- tors do not generally consider chronic health con- ROPRACTIC can provide extended pain relief (days ditions for which pain is a component, such as 378 maldynia 379

OSTEOARTHRITIS, to be maldynia because the pain, relievers in the body called endorphins. Exercise though persistent and long-term, results from an also improves balance, MUSCLE tone, and one’s identifiable cause. The pain associated with mal- overall sense of well-being. dynia may be sharp or dull, burning or aching, Maldynia is a life-altering condition. It inter- generalized or focused, continuous or intermit- feres with nearly every aspect of life, and often is tent. The one constant no matter the nature of the partially to completely disabling. Maldynia can pain is the absence of any pathologic reason for persist for years, go through cycles of improve- the pain to exist. ment and worsening, or suddenly disappear. The The diagnostic path differs for each individual, elusive nature of its symptoms makes maldynia a generally focusing on ruling out potential causes difficult challenge. However, with appropriate for pain. Diagnostic procedures that rule out par- medical guidance and a positive outlook, many ticular causes of pain may include imaging proce- people are able to achieve a reasonable QUALITY OF dures such as COMPUTED TOMOGRAPHY (CT) SCAN or LIFE. It is important to find a doctor who under- MAGNETIC RESONANCE IMAGING (MRI), electromyelo- stands and has experience treating chronic pain gram (EMG), evoked potential studies, and NERVE syndromes, and to keep the faith that improve- conduction studies. ment is possible.

Treatment Options and Outlook Risk Factors and Preventive Measures Treatment for maldynia ranges from nonnarcotic Researchers continue to look for the reasons for and narcotic ANALGESIC MEDICATIONS to nerve block maldynia. There does appear to be a correlation injections to alternative approaches such as between maldynia and a preceding circumstance ACUPUNCTURE and BIOFEEDBACK. For most people of untreated or undertreated ACUTE PAIN. Appropri- with maldynia, treatment is a process of trial and ate pain relief for acute pain (EUDYNIA) may pre- error with the goal of allowing participation in vent maldynia from following a significant trauma desired daily activities rather than complete relief such as injury or surgery. Otherwise, there are as from pain. Treatment is unique to the individual yet no clear risk factors and consequently no and varies over time, depending on effectiveness known measures to prevent maldynia. and improvement of the pain. Daily physical activ- See also ALTERNATIVE METHODS FOR PAIN RELIEF; ity to the extent possible releases natural pain NEUROTRANSMITTER.

TREATMENT OPTIONS FOR MALDYNIA Over-the-Counter Prescription Medications Injected Medications Mechanical Approaches Alternative Approaches Medications acetaminophen NSAIDs: diclofenac, TRIGGER-POINT MASSAGE THERAPY ACUPUNCTURE aspirin diflunisal, etodolac, INJECTIONS PHYSICAL THERAPY BIOFEEDBACK NONSTEROIDAL ANTI- fenoprofen, flurbiprofen, NERVE blocks TRANSCUTANEOUS exercise INFLAMMATORY DRUGS meclofenamate, injectable narcotics ELECTRICAL NERVE hydrotherapy (NSAIDS): ibuprofen, oxaprozin, piroxicam epidural blocks STIMULATION (TENS) MEDITATION ketoprofen, naproxen NARCOTICS: codeine, epidural steroids heat/cold self-hypnosis topical analgesics hydromorphone, intracathal injection CHIROPRACTIC topical levorphanol, manipulation counterirritants oxycodone, oxymorphone SPINAL CORD antidepressants: selective electrostimulation serotonin reuptake inhibitors (SSRIs), tricyclics N neural blockade (nerve block) An injection of ment along the nerve’s pathway is also possible an analgesic medication into a NERVE to block the though uncommon. transmission of PAIN to the CENTRAL NERVOUS SYSTEM See also ANALGESIC MEDICATIONS; CRANIAL NERVES; from a part of the body. Neural blockade is com- SPINAL NERVES. mon as preventive analgesia for ACUTE PAIN follow- ing surgery or injury and sometimes effective for neurolysis Destruction of part or all of a NERVE to treatment of CHRONIC PAIN. The doctor may also use prevent it from transmitting PAIN signals to the CEN- a neural blockade as a trial to determine the effec- TRAL NERVOUS SYSTEM. Neurolysis generally becomes tiveness of such an approach before conducting a a treatment option for CHRONIC PAIN, or MALDYNIA, permanent procedure such as RHIZOTOMY or NEU- when other methods to control pain are unsuccess- ROLYSIS. The effects of neural blockade are tempo- ful. There are three major methods of neurolysis: rary though generally long-lasting for most people (several weeks to several months, depending on • Chemical neurolysis involves injecting a chemi- the anesthetic agent). The doctor may inject a cal into the nerve that destroys the NEURON bod- major nerve, such as the brachial plexus, or a ies. Commonly used chemicals include phenol, spinal nerve. The most common sites for neural ethyl ALCOHOL, and hypertonic saline. blockade include • Surgical neurolysis involves cutting the nerve along the pain pathway that carries pain signals • occipital and trigeminal nerves, which serve the to the BRAIN. face and head • Ablative methods, primarily radiofrequency abla- • mandibular and maxillary nerves, which serve tion (which uses heat) and cryoablation (which the jaw and lower face uses freezing), cause neurons to die. • suprascapular nerve, which serves the shoulder The effects of neurolysis are permanent. Com- • brachial plexus, which serves the upper arm, plications and risks include undesired loss of sen- neck, and side of the face sation, loss of movement (PARALYSIS), bleeding, incomplete pain relief, or worsened pain. The • femoral nerve, which serves the hip and femur results of neurolysis vary among individuals and (thigh) sometimes take several weeks to months to • sciatic nerve, which serves the back of the leg become fully effective. When neurolysis is suc- and foot cessful, it ends the pain. See also ANALGESIC MEDICATIONS; ALTERNATIVE The risk is slight for complications or adverse METHODS FOR PAIN RELIEF; COMPLEX REGIONAL PAIN SYN- reactions. Bleeding and bruising at the site of the DROME; NEURAL BLOCKADE (NERVE BLOCK); RHIZOTOMY; injection are fairly common and generally minor. SURGERY BENEFIT AND RISK ASSESSMENT. Some people are allergic to topical anesthetics and may have a HYPERSENSITIVITY REACTION to a neural neurogenic pain PAIN that results from dysfunc- blockade. Unintended loss of sensation or move- tion of the nociceptors, specialized molecules on 380 nociceptor 381 the dendrites of neurons that detect pain and initi- These medications may cause potentially serious ate transmission of pain signals to the CENTRAL side effects, especially antiseizure medications. NERVOUS SYSTEM. Neurogenic pain often follows an Treatment may control pain until the underlying injury (traumatic or surgical) for which pain is a condition improves or may be a long-term thera- reasonable symptom. However, when the injury peutic process, depending on the cause of the dys- heals, the nociceptors can remain hypersensitive function. to stimuli, particularly touch and temperature, See also NEURON; NEUROTRANSMITTER; NOCICEPTOR; which they perceive as painful, and the nocicep- PSYCHOGENIC PAIN. tors continue to initiate pain signals. Neurogenic pain often accompanies degenerative neurologic nociceptor A specialized molecule on the den- conditions such as MULTIPLE SCLEROSIS and pain syn- drite of a sensory NEURON that interprets stimuli as dromes such as trigeminal NEURALGIA and COMPLEX PAIN and activates NERVE fibers (C fibers and A- REGIONAL PAIN SYNDROME. delta fibers) to send pain signals to the CENTRAL The sensation of neurogenic pain is characteris- NERVOUS SYSTEM. Nociceptors activate the with- tically that of a persistent tingling, burning, or drawal REFLEX—the sudden, involuntary move- “pins and needles” feeling. Some people also feel ment to get away from the stimulus such as sharp stabs of pain. The diagnostic path typically jerking one’s hand from a hot surface. Sensory includes evaluation of other potential causes for neurons often have extensive networks of den- the pain in the context of any history of a muscu- drites, the branchlike fibers that extend from the loskeletal injury or neurologic condition. Diagno- nerve body to draw input into the neuron. Noci- sis is often clinical (based on symptoms) after the ceptors pepper these dendrites, serving as one of doctor has assessed or ruled out possible condi- the body’s most primal warning mechanisms of tions that could account for the symptoms. danger from physical harm. They respond to sen- sations of heat, cold, sharp, and pressure. MEDICATIONS TO TREAT NEUROGENIC PAIN TRANSCUTANEOUS ELECTRICAL NERVE STIMULATION amitriptyline baclofen (TENS), a pain relief method, uses mild electrical carbamazepine dantrolene current to stimulate nociceptors. Researchers desipramine fluoxetine believe this either restores the neuron’s normal gabapentin paroxetine perceptions of stimuli or overloads the neuron so phenytoin sertraline that it cannot transmit pain signals. Doctors tizanidine valproic acid believe counterirritants such as capsaicin topical ointment work in a similar fashion. Some Western Because neurogenic pain results from NERVOUS researchers believe ACUPUNCTURE’s effectiveness for SYSTEM dysfunction, conventional ANALGESIC MED- pain relief comes from its ability to stimulate or ICATIONS such as NONSTEROIDAL ANTI-INFLAMMATORY block nociceptor function; Western doctors often DRUGS (NSAIDS) and narcotics are not especially combine electrical stimulation with acupuncture effective for providing pain relief. Low-DOSE tri- to intensify this effect. cyclic ANTIDEPRESSANT MEDICATIONS and antiseizure For further discussion of nociceptors, please see medications often do provide relief, apparently the overview section “Pain and Pain Management.” through their influence on BRAIN neurotransmit- See also ALTERNATIVE METHODS FOR PAIN RELIEF; ters. Selective serotonin reuptake inhibitor (SSRI) ANALGESIC MEDICATIONS; DERMATOME; PROPRIOCEPTION; antidepressants are also effective in some people. SPINAL NERVES; TRADITIONAL CHINESE MEDICINE (TCM). P

pain An unpleasant perception in response to a ICATIONS, NEURAL BLOCKADE (NERVE BLOCK), and stimulus to the body. Multiple mechanisms con- ACUPUNCTURE. tribute to the perception of pain, which follows For further discussion of pain mechanisms and specific and predictable pathways to the BRAIN. The pain management, please see the overview section brain then interprets the nature of the pain and “Pain and Pain Management.” directs the appropriate body response. Pain is one See also ACUTE PAIN; ALTERNATIVE METHODS FOR of the body’s main defenses for protecting itself PAIN RELIEF; CHRONIC PAIN; EUDYNIA; MALDYNIA; NEU- from harm. The pain REFLEX is the unconscious RORECEPTOR; NEUROTRANSMITTER; TERMINAL PAIN. and immediate effort to remove the body part from the source of the stimulus and protect it phantom pain The sensation of PAIN that feels as from further damage, for example pulling the though it came from an amputated limb or other hand from contact with a sharp object and grab- body part. Researchers believe phantom pain bing the wound (which applies pressure to stop results from continued activity, after the AMPUTA- bleeding as well as the further release of TION, among neurons in the BRAIN that interpret PROSTAGLANDINS and other substances that stimu- NERVE signals. Severed nerve fibers near the site of late INFLAMMATION and the pain response. the amputation continue to send signals even Pain can take the form of many and varied though the surgery has removed most of their characteristics: it can be sharp, dull, constant, nociceptors (molecules that detect stimuli as pain). intermittent, stabbing, throbbing, burning, local- The remaining portions of the nerves continue to ized, widespread. These characteristics help iden- function, and the brain interprets their incomplete tify possible causes for the pain. The presence of messages as pain signals. The pain often feels of health conditions such as DIABETES, PERIPHERAL VAS- the same nature as pain that might have been CULAR DISEASE (PVD), MULTIPLE SCLEROSIS, and SYS- present in the limb before the amputation. TEMIC LUPUS ERYTHEMATOSUS (SLE) also provide clues Many people who have phantom pain also as to the underlying reasons for pain. have stump pain (pain in the remaining portion of Pain management methods target various inter- the limb). Stump pain generally results from the sections along the pain pathway. Some approaches damage to the nerves at the site of the amputa- and medications aim to reduce the production of tion. Doctors do not know the extent to which substances (such as prostaglandins) at the site of stump pain contributes to phantom pain. injury, reducing the body’s biochemical call to One therapeutic approach that may prevent action that stimulates nociceptors. Others attempt phantom pain is administration of CALCITONIN, a to block NERVE signals from entering the dorsal HORMONE that prevents calcium from leaving the root ganglia, and still others manipulate neuro- BONE to enter the BLOOD circulation, after the OPER- transmitters and neuroreceptors in the brain to ATION. Doctors are uncertain why calcitonin has a alter the brain’s interpretation and resulting per- preventive affect in this way. Phantom pain seems ception of pain signals that reach the thalamus to respond better to medications used to treat NEU- and the cerebral cortex. Numerous methods are ROGENIC PAIN than to conventional ANALGESIC MED- available to relieve pain, including ANALGESIC MED- ICATIONS. Such medications include antiseizure 382 psychogenic pain 383 medications, tricyclic ANTIDEPRESSANT MEDICATIONS, cumstances, for example, rather than as a result of and antispasmodic medications. physiologic changes that would reasonably bring See also ACUTE PAIN; CHRONIC PAIN; EUDYNIA; MAL- about increase or decrease in pain intensity. DYNIA; NEURON; NOCICEPTOR. Psychogenic pain may be acute (come on sud- denly) or chronic (persist over an extended time). psychogenic pain A PAIN disorder in which the Most people benefit from a combination of treat- pain the person experiences has no apparent ment that incorporates PSYCHOTHERAPY, nonmedica- organic or physical basis. Psychogenic pain often tion methods for pain relief, and mild ANALGESIC has accompanying psychologic components such MEDICATIONS or other medications appropriate for as anxiety or DEPRESSION. Recurring HEADACHE, BACK the person’s symptoms. Recovery depends on the PAIN, generalized MUSCLE pain, and STOMACH pain ability of the person and his or her health-care are common presentations of psychogenic pain. team to get to the bottom of the issues presenting In psychogenic pain, the experience of pain is themselves as pain, to appropriately address and as real as if there were a clear physical cause. resolve them. However, over time the nature of the pain devi- See also ACUTE PAIN; ALTERNATIVE METHODS OF PAIN ates from the characteristics the doctor would RELIEF; BEHAVIOR MODIFICATION THERAPY; CHRONIC PAIN; expect to observe with pain of organic cause. The GENERALIZED ANXIETY DISORDER (GAD); HYPOCHONDRIA- intensity of the pain may vary with external cir- SIS; MALDYNIA; SOMATIZATION DISORDER. T

terminal pain PAIN that results from the end- sistent levels of pain appear to block the normal stages of disease processes such as cancer, CARDIO- processes that would result in slowed breathing. VASCULAR DISEASE (CVD), and AIDS. Doctors Because the body continues to adjust to balance consider a health condition to be terminal when vital functions, there is no clear OVERDOSE ceiling the person is likely to live less than six months. for narcotics taken to treat severe or terminal Terminal pain occurs because damage to the tis- pain. ADDICTION, with its psychologic components, sues and structures of the body is extensive and is not a concern in treatment for most severe pain, widespread. The damage often directly involves including terminal pain. nerves. The pain may have a range of characteris- Family members who are concerned that their tics, from deep and sharp to pervasive and aching terminally ill loved ones are not receiving ade- or dull. quate pain relief should discuss this with the Current standards of practice in the United patient’s doctors and other health-care providers States call for doctors to prescribe or health-care and request consultation with a pain specialist if providers to administer ANALGESIC MEDICATIONS suf- concerns continue. Medications and therapies are ficient to relieve pain and provide comfort, even readily available to provide relief from terminal to the point of sedation if that is what is necessary. pain. Family members may worry that such sedation is See also CANCER TREATMENT OPTIONS AND DECI- tantamount to euthanasia and hastens death, but SIONS; END OF LIFE CONCERNS. this is not the case. The sedation, when the med- ication has such an effect, allows the person’s transcutaneous electrical nerve stimulation body to relax more deeply. The resulting sleep (TENS) A small device that transmits mild elec- increases comfort. Periods of wakefulness are then trical impulses through electrodes attached to the more peaceful. Administration methods such as surface of the SKIN above areas of PAIN. The implanted catheters and PATIENT CONTROLLED ANAL- impulses alter the function of the neurons (noci- GESIA (PCA) pumps allow the person to regulate the ceptors) responsible for transmitting pain signals degree of pain relief. to the CENTRAL NERVOUS SYSTEM. TENS is primarily a The amounts of medications, typically NAR- treatment for CHRONIC PAIN such as neck or low COTICS, necessary to accomplish this are typically BACK PAIN and is most effective for pain that is mild much higher than conventional dosaging. Doctors to moderate in severity. The doctor may suggest who are not familiar with pain treatment or ter- applying the electrodes above trigger points or minal illness are often concerned such amounts major nerves, or along dermatomes, depending on are too high and risk an life-threatening ADVERSE the path of the pain. REACTION such as depressed respiration (BREATHING) Settings that provide relief are highly individu- and HEART RATE. However, recent studies demon- alized and often TENS requires a period of trial strate that terminally ill people tolerate these high and error before the person finds electrode posi- doses without the adverse reactions people with tions, impulse intensity and duration, and timing less severe pain might experience. The physiologic settings that work. Though it is possible to set the changes that occur in the body with high or per- delivery of electrical impulses at such a level as to 384 trigger-point injection 385 be painful, there is no risk for electrical shock Typically a pain specialist, often an orthopedic from TENS. It is important to keep the electrode surgeon (specialist in musculoskeletal conditions) pads covered with gel. The main SIDE EFFECT with or a neurologist (specialist in conditions that affect TENS is irritation to the skin from the adhesive the NERVOUS SYSTEM), administers the trigger-point that holds the electrodes in place or from using injection. Depending on the cause of the damage, the electrodes without adequate gel. People who the injection may combine a local anesthetic with have an implanted PACEMAKER or IMPLANTABLE CAR- a corticosteroid medication to directly target DIOVERTER DEFIBRILLATORS (ICD) cannot use TENS INFLAMMATION in the area. The injection is an office because the electrical current of the TENS inter- procedure that causes brief discomfort from the feres with the pacing signals. insertion of the needle. Complete relief from pain See ACUPUNCTURE; DERMATOME; MALDYNIA; NERVE; immediately follows as the anesthetic numbs the NEURON; NOCICEPTOR; TRIGGER-POINT INJECTION. nerves. After the numbness wears off pain relief often lasts several months and for some people is trigger-point injection An injection of local permanent. anesthetic into an area of MUSCLE that has tight- The main risks of trigger-point injection are dis- ened into a knot that constricts or pressures a comfort at the time of injection and bruising at the NERVE, causing severe PAIN. Trigger points are site that may cause superficial (surface) tenderness highly sensitive to touch or other stimuli and may for several days. Ice to the site lessens the risk for form after musculoskeletal injuries and in CHRONIC bruising and relieves its discomfort. Other specific PAIN conditions such as myofascial pain syndrome risks depend on the injection site. and FIBROMYALGIA. See also ANESTHESIA; CORTICOSTEROID MEDICATIONS. U–V

understanding pain Though there are numerous intensity among individuals as well as in the same physiologic mechanisms responsible for PAIN, the person. actual experience of pain is subjective. Not only do people perceive similar pain differently but the Chronic Pain intensity and nature of pain varies within an indi- CHRONIC PAIN is the most frustrating kind of pain vidual. Many people find it difficult to express to because it is dysfunctional—that is, it exists without their doctors how much pain they are experienc- purpose—and often does not respond consistently ing, or may not themselves fully understand the to pain treatment approaches. The body’s pain intensity of their pain. Pain thresholds—the levels response is a protective mechanism intended to at which pain becomes intolerable— vary widely. draw conscious attention to an injurious process within the body and to enforce restricted use of the The Subjective Nature of Pain affected area of the body to facilitate healing. Despite all that doctors understand about the Chronic pain exists beyond this design, often devel- causes and mechanisms of pain, every person oping as an extension of purposeful pain (EUDYNIA) experiences pain differently. Numerous factors to become nonpurposeful (MALDYNIA) though frame an individual’s perceptions and experiences sometimes arising for no apparent reason. of pain. Key among them are Chronic pain can be quite debilitating. Health experts estimate that more than 70 million Ameri- • fear about the cause of the pain cans live with chronic pain that is intense enough • knowledge (or lack of knowledge) to interfere with their participation in common functions and activities. Though movement such • about the mechanisms of pain as walking often improves chronic pain regardless • expectations about treatments for pain of its source, the effort of engaging in even modest • the presence of other health conditions and physical activity can feel overwhelming. their symptoms Referred Pain • the appropriateness of treatment for any A person experiences referred pain at a location underlying condition that might be causing the some distance from the source of the pain. The pain location is sometimes so far removed from the • the appropriateness of treatment for the pain, source of the pain that the person does not con- including ANALGESIC MEDICATIONS (pain relief nect the pain with its cause. For example, gall medications) stones in the GALLBLADDER (cholelithiasis) often • attitudes of others, including family members cause pain in the upper back beneath the shoulder and health care providers, about the pain blade. Pain associated with HEART ATTACK may occur as referred pain to the left arm, shoulder, Though specific kinds of pain, such as postoper- neck, and lower jaw. ative pain (pain during recovery from surgery) Referred pain often adds challenge to diagnos- typically have certain characteristics, pain varies in ing the underlying cause of the pain. Even doctors 386 understanding pain 387

first look for a direct cause for the pain. When one people wait to see whether the pain will go away does not exist, diagnostic efforts extend to referred instead of going to a hospital emergency room for causes. Injured nerves are common sources of evaluation. The time wasted on such waiting can referred pain. Doctors do not fully understand the be the difference between life and death or signifi- physiologic mechanisms of referred pain. cant disability due to permanent heart damage. Though no one wants to feel silly for thinking he COMMON SOURCES OF REFERRED PAIN or she is having a heart attack and then discover- Pain Felt May Arise From ing the problem is dyspepsia (heartburn) or acid reflux, doctors would much rather this were the beneath the right shoulder the gallbladder case than for the person to delay seeking medical in the shoulder or neck the diaphragm or esophagus care and have the symptoms turn out to be a between the shoulder blades the stomach heart attack. Prompt medical intervention can in the groin the kidneys often minimize or prevent damage to the heart. in the middle of the back the kidneys or intestines in the ear the throat Explaining Pain to the Doctor in the lower back the uterus or intestines Because pain is so subjective, it is often difficult to around the belly button the appendix quantify its intensity when explaining it to the beneath the sternum the stomach or heart doctor. It can be helpful to present the doctor with in the sides (flanks) the kidneys the answers to questions such as these: under the left arm the heart back of the leg the lower spine • Where does it hurt? When to Seek Medical Care for Pain • How does the pain feel—is it sharp, dull, throb- bing, steady, aching, sharp? It may be a combi- Many people wait until pain becomes unbearable nation of these sensations, or change in specific before seeking medical evaluation and treatment, circumstances. particularly when no other symptoms exist. Such reluctance may arise from a perception that one • How long has the pain been present? Has the should be able “tough it out” or from fear that the pain changed in any way since it started? pain indicates a serious health problem. Often • Under what circumstances is the pain present? pain is an early symptom, however, and prompt Is it constant or intermittent? Does it get worse medical treatment can head off serious health at night or with activity? consequences. A person should seek medical eval- • What makes the pain worse? uation for pain that • What makes the pain better? • arises suddenly for no obvious reason • Does the pain limit participation in usual activi- • occurs with an injury and does not improve in ties? If so, from what activities and in what 48 hours ways? • worsens over time or recurs frequently Providing specific measures such as these help • is accompanied by symptoms such as blurred or both the person who has pain and the doctor double vision, numbness or loss of function in treating the pain to understand the effects the any part of the body, or difficulty breathing pain is having on the person’s ability to function • occurs in the chest, particularly as a pressing or in daily life. heavy sensation • is associated with bloody sputum, vomit, urine, Appropriate Pain Relief or stools Analgesic medications (pain relief medications) • interferes with regular activities are the most common therapeutic approach for acute and chronic pain. There are many kinds of Chest pain may indicate HEART ATTACK and medications that provide pain relief; the appropri- requires urgent medical evaluation. All too many ate medications depend on the cause and nature 388 Pain and Pain Management of the pain, other health conditions that are pres- numerous clinical studies have demonstrated that ent, other medications the person is taking, and addiction very seldom occurs. Physicians who are the person’s overall health status. Nonmedication pain management specialists or who frequently methods of pain relief, such as ACUPUNCTURE and treat conditions in which pain is a key symptom therapeutic massage, may also be effective. are most familiar with current approaches to pain It is important to take pain relief medications management. according to the directions on the label for both See also ALTERNATIVE METHODS FOR PAIN RELIEF; prescription drugs and OVER-THE-COUNTER (OTC) DRUG INTERACTION; LIVING WITH PAIN; NEUROGENIC PAIN; DRUGS. Many medications prescribed for pain PAIN MANAGEMENT IN CANCER; PATIENT-CONTROLLED relief, particularly to treat postoperative pain or ANALGESIA (PCA); PHANTOM PAIN; SCHEDULED DRUG; chronic pain, are most effective when taken on a SIDE EFFECT; WONG-BAKER FACES PAIN RATING SCALE. schedule that maintains a THERAPEUTIC LEVEL of the drug in the blood circulation. variable pain response The fluctuations that Just as people experience pain differently, peo- occur in the experience of PAIN. Pain’s subjective ple respond to pain medications differently. Con- nature means its intensity often varies with cir- sequently, the appropriate dose and schedule for cumstances not directly related to the cause of the the medication varies. As well, some medications pain. Factors such as heat, cold, moisture, signifi- are more effective for certain kinds of pain and cant drops or rises in the barometric pressure, pro- not very effective for other kinds of pain. It is longed sitting at a computer or riding in a car, important to let the doctor know if the prescribed certain activities or lack of activity, the consistency medication does not adequately relieve the pain or with which the person takes pain relief medica- causes unpleasant side effects. tion, and even the foods the person consumes all Many people, including doctors, worry about may influence pain intensity. The variability of ADDICTION with the use of NARCOTICS. As a result, pain, especially chronic pain, is often frustrating doctors may underprescribe or people may take because the person cannot always anticipate how less medication than is necessary to relieve the he or she will feel, even under given circum- pain. However, narcotics remain the most effective stances. Specific conditions may act either to ease analgesic medications for moderate to severe pain, or aggravate pain, though not necessarily with especially pain during recovery from surgery or predictable consistency. serious injuries and pain due to CANCER. Although See also ANALGESIC MEDICATIONS; EUDYNIA; LIVING many people do develop TOLERANCE to pain relief WITH PAIN; MALDYNIA; QUALITY OF LIFE; UNDERSTANDING medications being taken over an extended time, PAIN; WEIGHT AND PAIN. W–Z

weight and pain The influence of excessive body other substances that act like natural pain reliev- weight on the experience of PAIN. Excessive body ers in the brain. The effects of these substances weight may itself be the cause of pain, particularly lasts far longer than the exercise session. pain that affects the joints, or may contribute to Regular physical exercise also strengthens mus- pain due to underlying health conditions such as cles and connective tissues and broadens flexibil- FIBROMYALGIA, ANKYLOSING SPONDYLITIS, PLANTAR ity. These effects increase the stability of the joints, FASCIITIS, and GOUT. OBESITY is a risk factor for improving joint function. Even when pain is unre- numerous chronic conditions that cause pain lated to the joints, these effects are beneficial for including OSTEOARTHRITIS and chronic BACK PAIN. most underlying health conditions for which pain is a key symptom. And regular physical activity Excessive Body Weight improves cardiovascular function, notably circula- and Musculoskeletal Structures tion, increasing the flow of blood to all parts of the Excessive body weight has numerous adverse body. Increased blood flow brings oxygen and effects on the musculoskeletal system because it other vital substances to areas of HEALING, helping alters the person’s posture and movement. The both to speed healing and to keep scar tissue from effects are most noticeable on the joints, which stiffening. may develop chronic discomfort and aching. Every However, the natural tendency is to avoid 10 pounds of body weight in excess of healthy activity when pain is present. A reduced level of weight increases the force the knees experience activity may be appropriate for certain health con- during walking by about 50 pounds each time the ditions, especially for a defined period of recovery foot strikes the ground. Weight-bearing joints time. Extended inactivity contributes to, rather below the waist (hips, knees, ankles, and feet) are than relieves, pain. It may also give rise to other particularly vulnerable to weight-related pain. health complications such as DEEP VEIN THROMBOSIS Because excessive body weight strains muscu- (DVT) or PULMONARY EMBOLISM (blood clots in the loskeletal structures, it often contributes to pain veins of the legs or in the lungs), pneumonia symptoms related to chronic conditions such as (fluid accumulation in the lungs, and pressure back pain. The pressure of the excessive weight sores or decubitus ulcers. Extended inactivity also over time may also cause damage to the joints; tends to encourage further weight gain, even numerous studies implicate overweight and obe- when food intake remains the same, because sity in the development or escalated progression of reduced movement means the body uses less osteoarthritis, the most common degenerative dis- energy. order affecting the joints. Appropriate Physical Activity Physical Activity and Pain Relief The doctor can recommend activities and intensity Regular, moderate physical activity often improves levels that are appropriate for both the health con- chronic pain regardless of its source. Exercise, par- dition and the person’s FITNESS LEVEL. A physical ticularly activities that extend 20 minutes or therapist or qualified fitness and training expert longer, causes the body to release endorphins and can develop a customized program for progressive 389 390 Pain and Pain Management

fitness improvement as well as weight loss. Such a pain). Children choose the face that best expresses consultation is especially helpful for people who how their pain feels to them. have been physically inactive for a long period of Many hospitals and pediatricians use the time or who have challenges such as FLAT FEET or FACES scale, available on a pocket-size card, WEAK ANKLES. Moving too quickly into an intense because it is straightforward and even very young exercise program can worsen the underlying children are usually able to associate how they health condition or cause other injuries. The doc- feel with one of the faces. The most effective tor may also recommend nutritional counseling approach is for the health care provider to explain for further weight loss. to the child what the faces indicate in terms of See also AEROBIC FITNESS; AEROBIC EXERCISE; DIS- pain severity (for example, smiling face being no ABILITY AND EXERCISE; EXERCISE AND HEALTH; LIVING pain and very sad face with tears being the worst WITH PAIN; OBESITY AND HEALTH; PHYSICAL ACTIVITY REC- pain) and then ask the child to choose the face OMMENDATIONS; WALKING FOR FITNESS; WEEKEND WAR- that best expresses how he or she feels. RIOR; WEIGHT AND WEIGHT MANAGEMENT. The FACES scale has associated numeric values (0 to 5) to aid the health care provider in inter- Wong-Baker FACES pain rating scale A propri- preting the child’s pain level. The scale also help etary, commonly used visual tool designed for use clinicians to assess pain as a symptom during the with children to help them quantify the intensity diagnostic process as well as to evaluate the effec- of PAIN they are experiencing. Developed by tiveness of pain relief methods and medications Donna Wong, Ph.D., R.N. and Connie Baker, for treatment of post-operative, traumatic, and Ph.D., R.N., the FACES scale presents a sequence chronic pain. of six faces with expressions ranging from happy See also AGING, CHANGES IN PAIN PERCEPTION THAT (no pain) to neutral (some pain) to sad (much OCCUR WITH; ANALGESIC MEDICATIONS. MEDICAL ADVISORY REVIEW PANEL

Kyra J. Becker, M.D., is codirector of the Uni- topics. Educated in Germany and the United States, versity of Washington Stroke Center in Seattle, she has extensive experience in natural therapies Washington. She is also an associate professor of and integrative medicine. Dr. Fleckenstein is board- neurology and neurological surgery at the Univer- certified in internal medicine. sity of Washington School of Medicine. Dr. Becker Dr. Fleckenstein received her medical degree provides patient care through her practice at Har- from Universität Hamburg, Germany. She com- borview Medical Center and is a primary investi- pleted her internship and residency in primary gator on several stroke-related research studies. care medicine at Carney Hospital in Boston, Mass- Dr. Becker received her bachelor of science achusetts, and a fellowship in ambulatory medi- (B.S.) degree in biology summa cum laude from Vir- cine at VA Brockton, Massachusetts. Her ginia Tech in Blacksburg, Virginia, and her doctor subspecialty certification in natural medicine is of medicine (M.D.) degree from Duke University from Ärztekammer Hamburg (German Board). School of Medicine in Durham, North Carolina. She completed her internship in internal medi- Nancy A. Lewis, Pharm.D., is a clinical phar- cine, residency in neurology, and clinical fellow- macist and medical science liaison for MGI ship in critical care neurology all at Johns Hopkins Pharma, Inc., a biopharmaceutical company spe- Hospital in Baltimore, Maryland. Dr. Becker is cializing in oncology and acute care products. Dr. board-certified in neurology and psychiatry with a Lewis frequently conducts workshops and focused special certification in vascular neurology. training presentations. She is an active member of the Washington-Alaska Cancer Pain Initiative. James C. Blair, III, PA-C, is director of Madrona Dr. Lewis received her bachelor of science Hill Urgent Care Center in Port Townsend, Wash- (B.S.) in pharmacy and her doctor of pharmacy ington. Mr. Blair is a physician assistant certified (Pharm.D.) degrees from the University of Wash- with special recognition in primary care and sur- ington in Seattle, Washington. She serves on the gery. He is an advanced cardiac life support clinical faculty at the University of Washington in (ACLS) instructor and has worked much of his Seattle, Washington and on the adjunct faculty at career to provide emergency services in small hos- Washington State University in Pullman, Wash- pitals and clinical care settings in rural communi- ington. ties. Mr. Blair received his associate of science Gary R. McClain, Ph.D., is a psychologist, coun- degree in nursing from Wenatchee Valley College selor, and consultant in New York City. Dr. McClain in Wenatchee, Washington, and completed the has more than 25 years of experience as a mental MEDEX Northwest Physician Assistant Program at health professional and in the business world. The the University of Washington School of Medicine focus of his practice is healthcare and wellness. in Seattle, Washington. Dr. McClain’s graduate studies were in clinical psychology and education, with a focus on adult Alexa Fleckenstein, M.D., writes books and con- personality development and learning. He ducts lectures and workshops about natural health received his doctor of philosophy (Ph.D.) from the 391 392 Medical Advisory Review Panel

University of Michigan. Dr. McClain has coau- care medicine at the University of Washington thored or edited 14 books and frequently conducts School of Medicine, Seattle, Washington. workshops. Maureen Pelletier, M.D., C.C.N., F.A.C.O.G.,is Maureen Ann Mooney, M.D., is a clinical, surgi- board-certified in obstetrics and gynecology as well cal, and cosmetic dermatologist in private practice as in clinical nutrition. A former aviation medical in Puyallup, Washington, where she specializes in examiner, Dr. Pelletier is also licensed as a medical treating skin cancer. Dr. Mooney is trained to per- acupuncturist and is a DAN! (Defeat Autism Now!) form Mohs’ Micrographic Surgery. Dr. Mooney is physician. She is in private practice in Cincinnati, board-certified in dermatology and dermato- Ohio, with an emphasis on integrative medicine. pathology. Dr. Pelletier received her medical degree (M.D.) Dr. Mooney received her bachelor of science from Tufts University School of Medicine in (B.S.) degree in biology summa cum laude from the Boston, Massachusetts, and completed her resi- University of Minnesota College of Biological Sci- dency in obstetrics and gynecology at the Univer- ences in St. Paul, Minnesota, and her doctor of sity of Cincinnati. She received clinical training in medicine (M.D.) degree from the University of mind-body medicine at the Mind-Body Institute at Minnesota School of Medicine in Minneapolis, Harvard University and completed the integrative Minnesota. She completed her internship at Hen- medicine program at the University of Arizona nepin County Medical Center in Minneapolis, School of Medicine. Dr. Pelletier is a national and Minnesota, and her residency in dermatology at international lecturer. New Jersey Medical School in Newark, New Jer- sey. Dr. Mooney also completed fellowships in Otelio S. Randall, M.D., F.A.C.C., is director of Dermatopathology at New Jersey Medical School the preventive cardiology program, hypertension and Mohs’ Micrographic Surgery at Louisiana and clinical trials, and the Cardiovascular Disease State University Healthcare network in New Prevention and Rehabilitation Center at Howard Orleans, Louisiana. University Hospital in Washington, D.C. Dr. Ran- dall is widely published in peer-reviewed journals Margaret J. Neff, M.D., M.Sc., is attending and has authored two books. He has received physician, pulmonary and critical care medicine, numerous awards during his career, including the at Harborview Medical Center in Seattle, Wash- 2004 Outstanding Faculty Research Award from ington. Dr. Neff is a medical monitor for the Cystic Howard University School of Medicine. Fibrosis Therapeutic Diagnostics Network, co-chair Dr. Randall received his bachelor’s degree (B.S.) of one of the biomedical committees of the Uni- in chemistry from Howard University and his versity of Washington Institutional Review Board, medical degree (M.D.) from the University of and a clinical investigator on several research Michigan Medical School in Ann Arbor, Michigan. studies. She is board-certified in internal medi- He completed his internship at the State Univer- cine, pulmonary disease, and critical care medi- sity of New York at Brooklyn, residencies in inter- cine. nal medicine at Baylor College of Medicine in Dr. Neff earned her bachelor’s degree in biologi- Houston, Texas, and University of Michigan Hos- cal sciences (B.S.) and medical degree (M.D.) from pital, and a fellowship in cardiology at the Univer- Stanford University in Stanford, California, and her sity of Michigan Hospital. Dr. Randall is designated master of science (M.S.) degree in epidemiology a specialist in hypertension by the ASH specialists from the University of Washington in Seattle, program in affiliation with the American Society Washington. She completed her internship and res- of Hypertension (ASH). idency in internal medicine and a fellowship in intensive care at Stanford University and a fellow- Susan D. Reed, M.D., M.P.H., is program director ship in pulmonary/critical care at the University of for the Women’s Reproductive Health Research Washington. Dr. Neff is an assistant professor of Program at the University of Washington in Seattle, medicine in the division of pulmonary and critical Washington. She is a clinician at Harborview Medical Advisory Review Panel 393

Medical Center and University of Washington Christina M. Surawicz, M.D., is gastroenterol- Medical Center. Dr. Reed is also an affiliate investi- ogy section chief of at Harborview Medical Center gator at the Center for Health Studies and Fred in Seattle, Washington. She is also professor of Hutchinson Cancer Research Center, and an associ- medicine and assistant dean for faculty develop- ate professor of obstetrics and gynecology, and an ment at the University of Washington School of adjunct professor in epidemiology at the University Medicine in Seattle. Dr. Surawicz is widely pub- of Washington School of Medicine. Dr. Reed’s areas lished in peer-reviewed journals and has of clinical and research interest are gynecologic authored, edited, and contributed to dozens of issues for women with genetic diseases, cross-cul- books. tural medicine, and management of menopause. Dr. Surawicz received her undergraduate Dr. Reed received her master’s degree (M.S.) in degree, a bachelor of arts (B.A.) in biology, from human genetics from Sarah Lawrence College in Barnard College in New York City and her medical Bronxville, New York, her medical degree (M.D.) degrees (M.D.), awarded with honors, from the from Stanford University Medical Center in Stan- University of Kentucky College of Medicine in ford, California, and her Master of Public Health Lexington, Kentucky. She completed her medical (M.P.H.) degree from the University of Washing- internship, medical residency, and gastroenterol- ton School of Public Health. Dr. Reed is a licensed ogy fellowship at the University of Washington in genetic counselor and board-certified in obstetrics Seattle. Dr. Surawicz is board-certified in internal and gynecology. medicine and gastroenterology.

Jerry Richard Shields, M.D., is an ophthalmol- Denise L. Wych, R.N. C.M., is a cardiac nurse ogist in private practice in Tacoma, Washington. case manager at Palmetto Health-Richland Heart He sees general ophthalmology patients and per- Hospital in Columbia, South Carolina, where she forms laser correction and cataract surgery. Dr. integrates clinical and medical appropriateness cri- Shields is board-certified in ophthalmology and teria in discharge planning and resource utiliza- VISIX-certified. tion within the framework of an interdisciplinary Dr. Shields received his bachelor of science health-care team. She has worked in medical-sur- (B.S.) degree in biology cum laude from Wake For- gical, intensive care unit, newborn, school nurs- est University in Winston-Salem, North Carolina, ing, and home health. and his medical degree (M.D.) from the Medical Ms. Wych received her diploma in nursing College of Georgia in Augusta, Georgia. He com- from Providence School of Nursing in Sandusky, pleted his internship in internal medicine and his Ohio. She served 10 years as an officer in the US residency in ophthalmology at the University of Navy Nurse Corps, during which she was twice Washington in Seattle, Washington. awarded the Navy Achievement Medal.

INDEX

Page numbers in bold indicate eudynia 372 Alzheimer’s disease 221–223 major treatment of a topic. Page fibromyalgia 321–322 memory and memory numbers with an italic t indicate maldynia 379 impairment 261 tables. neural blockade 380 neuralgia 268–269 psychogenic pain 383 organic brain syndrome 272, A acyclovir 103 273 ABCD skin examination (for ADA (Americans with Disabilities Parkinson’s disease 275–276 malignant melanoma) 197, 198t, Act) 30 tremor disorders 288–289 199–200, 200t Adam’s apple 57 aging, otolaryngologic changes that abducens nerve 246, 247t addiction 368, 384 occur with 7, 8–9, 45–46, 52–54 abscess 44, 143 adenoid hypertrophy 7–8 aging, vision and eye change that absence seizures 281 adenoids 7–8, 58 occur with 71–72, 72t accidental injuries 218, 327 adhesive capsulitis 298–299, 353 ARMD 70–71 ACE inhibitor. See angiotensin- adipocytes 333–334 astigmatism 73 converting enzyme inhibitor adipose tissue 128, 134–135, cataract 77–78 acetaminophen 364, 366–368, 375 333–334 dacryocystitis 85 acetylcholine adolescence 313 dry eye syndrome 86 Alzheimer’s disease 221–223 adolescent nervous system 220–221 ectropion 87 botulinum therapy 141 adult acne. See rosacea glaucoma 94 hyperhidrosis 165 adult-onset osteopetrosis 345 ischemic optic neuropathy muscle 336 adverse drug reaction 365, 384 97–98 musculoskeletal system 294 aerobic exercise 63 night blindness 102 nervous system 217 aerosols and glues 49 presbyopia 108–109 neurotransmitter 272 age-related cataracts 77 AHA. See alphahydroxyl acid acetylcholine receptor 339 age-related macular degeneration AIDS. See HIV/AIDS acetylcholinesterase inhibitors 222, (ARMD) 69, 70–71, 73, 78 AIDS Clinical Trials Group (ACTG) 262, 273 age spots. See lentigines system 169 Achilles tendon 297, 358, 359 aging, changes in pain perception AIDS-related Kaposi’s sarcoma Achilles tendon injury 297–298 that occur with 364–365 168, 169 achondroplasia 298, 334 aging, effects on drug metabolism air puff tonometry 119 acne 131–133, 132t and drug response 364–365 albinism 135–136, 176 acne, adult. See rosacea aging, integumentary changes that alcohol 313, 362 acoustic neuroma 7 occur with 134–135, 210–211 alcoholism 262 acquired nystagmus 102 aging, musculoskeletal changes that ALK (automated lamellar acrochordon 133 occur with 299–300 keratoplasty) 112 actinic keratosis 133–134, 135, 158 adhesive capsulitis 298–299 alkaline phosphatase 348 action myoclonus 265 herniated nucleus pulposus allergic rhinitis 8, 51 action potential 270 326–327 allergies 18, 150 acupuncture 61, 365, 375, 378, hip fracture in older adults 327 allergy 368 381 osteoarthritis 341–342 allodynia 371 acute bacterial sinusitis 52 osteoporosis 345–347 allograft 199 acute cough 18 polymyositis 350 alopecia 135, 136–138, 137t, 162, acute pain 363–364, 363t aging, neurologic changes that 173 analgesic medications 367 occur with 220–221 alopecia areata 137, 138

395 396 Index alphahydroxyl acid (AHA) 144, 171 aneurysm 233 aspiration 18, 25 alpha waves 253 angioedema 206 aspirin 59, 280, 361, 362, 368, 375 alprazolam 289 angioma 138 aspirin therapy 183 ALS (amyotrophic lateral sclerosis) angiotensin-converting enzyme asthma 356 223–225 (ACE) inhibitor 18, 42t astigmatism 73, 80–82, 111 alternative methods for pain relief ankle injuries 301–302 ataxia 226–227 365–366, 380 ankylosing spondylitis 302–303 ataxia telangiectasia 226 Alzheimer’s disease 221–223 anterior uveitis 120 ataxic cerebral palsy 239 aphasia 225 antianxiety medications 16 atheoid cerebral palsy 239 cognitive function and anticholinergic medication 50, 320 atherosclerosis 58, 261 dysfunction 243 anticoagulation therapy 235 athetosis 227 dementia 252 antidepressant medications 119, athlete’s foot. See tinea memory and memory 217, 272, 366, 367, 381 athletic injuries 304–305, 305t impairment 262 antifungal medications 204, 204t Achilles tendon injury 297–298 nervous system 217–219 antihistamine medications 12, 21, ankle injuries 301–302 neurotransmitter 272 52, 61, 62 knee injuries 332 organic brain syndrome 273 antipsychotic medications 252 meniscectomy 336 amblyopia 72–73, 100, 110, 118 antiseizure medication Osgood-Schlatter disease 341 American Academy of Neurology analgesic medications 367, 368 repetitive motion injuries 352 233 phantom pain 382–383 RICE 353 American Academy of Pediatrics 40 seizure disorders 281, 281t rotator cuff impingement American Cancer Society 168 spina bifida 282 syndrome 353 American Sign Language (ASL) 51 tremor disorders 289 sprains and strains 356 American-Speech-Language- antispasmodic medications. See atopic dermatitis 150 Hearing Association (ASLHA) 28 muscle relaxant medications atrophic (dry) ARMD 70–71 Americans with Disabilities Act antiviral medications 269 audiologic assessment 9–10, 41, 43 (ADA) 30 anxiety 383 audiometry 9 amlexanox (Aphthasol) 14 aorta 352 auditory canal 14–15, 59 ammonia 152 aphasia 225 auditory ossicles 41 amnesia 261 Aphthasol (amlexanox) 14 aura 374 amputation 300–301, 323, 351, aphthous ulcer (canker sore) 14 auricle 14, 41 382 apocrine sweat glands 128, 164, auricular chondritis 318 Amsler grid 70, 71, 73, 117 202 autograft 198, 199 amygdala 231, 260–261 apolipoprotein E (apoE) 221 autoimmune disorders amyloid plaques 221 appendicular skeleton 293, 355 alopecia 137 amyotrophic lateral sclerosis (ALS) applanation tonometry 119 alopecia areata 138 223–225 apraxia 225–226 bullous pemphigoid 142 analgesic medications 366–368 aqueous humor 67, 92, 93 chondritis 318 acute pain 363 arachnoid mater 262 chronic fatigue syndrome aging, changes in pain area postrema 229 369–370 perception that occur with Aricept (donepezil) 222 cicatricial pemphigoid 79 364 ARMD. See age-related macular DLE 152–153 earache 21 degeneration dry eye syndrome 86 eudynia 372 arteric ischemic optic neuropathy episcleritis 88 headache 377 98 iritis 97 living with pain 378 arterioles 127 multiple sclerosis 263 maldynia 379 arthritis 302–303, 322–324. See also myasthenia gravis 339 neural blockade 380 specific forms of arthritis, e.g.: narcolepsy 267 pain and pain management osteoarthritis pemphigus 182–183 361, 362 arthrogryposis 303–304 polymyositis 350 rebound headache 374–375 arthroscope 304 sialadenitis 50 terminal pain 384 arthroscopy 295–296, 304 urticaria 206 analog devices 27 ASL (American Sign Language) 51 vitiligo 207 anaphylaxis 206 ASLHA (American-Speech- autologous grafts 205 androgenic alopecia 137, 162 Language-Hearing Association) automated lamellar keratoplasty anesthesia 385 28 (ALK) 112 Index 397 autonomic nervous system 216, 277 birth defects. See also congenital bone cell 298, 299 avulsion 322 anomaly bone density 310–311, 313, avulsion fracture 301, 341 acne medications 132 344–347 axial skeleton 293, 355 congenital hip dysplasia bone disease (osteogenesis axon 216, 220, 270, 271, 283 318–319 imperfecta) 342–343 minoxidil and finasteride 138 bone loss 345 B spina bifida 282–283 bone marrow 308, 309, 344–345, back pain 306–307 talipes equinovarus 358 355 ankylosing spondylitis 302 birthmark 139–141, 140t, 203 bone marrow transplantation 345 cervical spondylosis 316–317 bismuth subsalicylate (Pepto bone spur 311, 356 chiropractic 365 Bismol) 280 bony labyrinth 4 herniated nucleus pulposus bisphosphonates 346, 348 Botox (botulinum neurotoxin A) 326–327 black eye 74 141 laminectomy 333 bleeding control 22 botulinum neurotoxin A (Botox) spinal stenosis 356 blepharitis 74, 96, 106 141 baclofen (Lioresal) 102, 259, 360 blepharoplasty 75, 210 botulinum neurotoxin B (Myobloc) bacteria 39 blepharospasm 75 141 bacterial labyrinthitis 31 blindness 92 botulinum therapy 141 bacterial sinusitis 52 blind spot 117, 121. See also optic blepharospasm 75 bad breath. See halitosis disk dystonia 320 Baker, William Morrant 307 blinking 65 hyperhidrosis 165 Baker’s cyst 307 blister 141 sialorrhea 50 balance 3–4, 33–35 bulla 141–142 tremor disorders 289 ball and socket joint 294 epidermolysis bullosa 154 wrinkles 210 ballism 242 frostbite 159 bovine spongiform encephalopathy barotrauma 11, 48 impetigo 166 (BSE) 248 basal cell carcinoma 130, 176, pustule 190 BPPV (benign paroxysmal 196–197, 198t staphylococcal scalded skin positional vertigo) 11–12 basal ganglia 227, 231, 238, 241, syndrome 200 bradykinesia 252 252, 256 blood 323 braille 75–76 baseball elbow (medial blood-brain barrier 229, 230, 272 Braille, Louis 75 epicondylitis) 320 blood cells 355 brain 230–233, 231t, 233t basement membrane 154 blood clots 346 Alzheimer’s disease 221 Becker’s muscular dystrophy 337, blood donation 189 analgesic medications 367, 368 338t blood vessels 127–128, 244, aphasia 225 bedsore. See decubitus ulcer 373–374 blood-brain barrier 229 behind the ear (BTE) hearing aid bloody nose. See epistaxis cerebral palsy 238–241 27 blowing the nose 12–13, 36 cerebrospinal fluid 241 Bell’s palsy 87, 228–229 Bogart-Bacall syndrome 13 CJD 248–249 Benadryl. See diphenhydramine boil. See furuncle coma 244 benign essential blepharospasm 75 bone 307–309, 309t, 311t concussion 244–245 benign essential tumor 286, 288 ankle injuries 301 deep brain stimulation 250 benign paroxysmal positional calcium and bone health dementia 251–252 vertigo (BPPV) 11–12 313–315 EEG 253–254 benign tumor. See tumor, fracture 322–323 encephalopathy 254 noncancerous musculoskeletal system 293 Huntington’s disease 256 benzodiazepines 16 osteogenesis imperfecta hydrocephaly 256–257 benzonatate 19 342–343 learning disorders 258–259 beta blocker 289, 367, 368 osteomalacia 343 maldynia 378 beta waves 253 osteomyelitis 343–344 memory and memory bicuspid 294 osteopetrosis 344–345 impairment 260–262 bifocal eyeglasses 83 Paget’s disease of the bone 348 meninges 262–263 binocular diplopia 86 skeleton 355 musculoskeletal system 293 binocular vision 121 talipes equinovarus 358 nervous system 215, 217, 218 biochemicals 362 tendon 359 organic brain syndrome biofeedback 365, 375 bone cancer 309–310 272–273 398 Index

pain and pain management 361 candidiasis 179 lobes of 231t seizure disorders 281–282 canker sore 14 nervous system 215 smell and taste disturbances capillaries 229 pain and pain management 361 52–54 carbuncle 143 seizure disorders 281 traumatic brain injury (TBI) cardiomyopathy 335 cerebral dominance 215 287–289 cardiovascular disease (CVD) 221, cerebral palsy 217, 227, 238–241, tremor disorders 288–289 233, 335, 384 240t brain cells 215 cardiovascular system 3, 4 cerebrospinal fluid 241, 241t brain damage (chorea) 241–242 carpal tunnel syndrome 275, brain 230 brain death 233, 244, 253 315–316 hydrocephaly 256–257 brain hemorrhage 233–235, 234t cartilage 316 lumbar puncture 259 brainstem 54, 215, 232, 235, 277 achondroplasia 298 meninges 263 brain tumor 235–237, 235t, 236t aging, musculoskeletal changes otorrhea 41 branchial motor nerves 246, 247t that occur with 299 rhinorrhea 47 breast 200 back pain 306 cerebrum 242 breathing 4, 5, 13, 16, 39, 63 cauliflower ear 14 cerumen 14–15, 15, 21, 29, 40, 41 breathing difficulties 206 chondritis 318 cervical spine 306 brittle bone disease. See crepitus 319 cervical spondylosis 316–317 osteogenesis imperfecta herniated nucleus pulposus 326 cesarean section 303 broken nose 13 knee injuries 330 chalazion 79 bronchi 182 kyphosis 332 Charcot’s disease. See amyotrophic bruise. See ecchymosis meniscectomy 336 lateral sclerosis bulla 141–142, 142, 142t, 154–155, musculoskeletal system 294 Charcot-Marie-Tooth (CMT) disease 182 osteoarthritis 341–342 317–318 bullous keratopathy 76 spinal cord 283 Chédiak-Higashi syndrome 136 bullous myringitis 35 Catapres (clonidine) 287 chemical peel 144–145, 210 bullous pemphigoid 142 cataract 67, 77–78, 78t, 103 chemotherapy 42t, 169, 169t, 237, bursa 311–312 cataract extraction and lens 310 bursitis 312, 352 replacement 68–69, 76, 78–79 chest pain 363 cauliflower ear 14 chickenpox 103 C causalgia 371 chi (energy of life) 365 CAD (coronary artery disease) 211 cavernous hemangioma 139 child abuse 287 caffeine 377 cavities, dental. See dental caries childhood diseases (Reye’s calcification 316 cell structure and function 270, syndrome) 279–280 calcitonin 346, 348, 382 340 children calcium 355 cellulitis 143–144, 155 aging, changes in pain calcium and bone health 310, central nervous system 238 perception that occur with 313–315, 313t, 314t, 343, 345–346 aging, neurologic changes that 364 calcium channel blockers 367, 368 occur with 220 aging, integumentary changes calculus, salivary 50 brain 230–233 that occur with 134 callus 141, 143 cranial nerves 246–247 concussion 245 caloric test 12, 62 multiple sclerosis 263–265 hearing loss 29 Campylobacter jejuni 255 muscle relaxant medications impetigo 166 cancellous (spongy) bone 308, 309 337 rhabdomyoma 353 cancer nervous system 215 scoliosis 354, 355 actinic keratosis 133 neural blockade 380 verbal apraxia 225–226 bone cancer 309–310 neurogenic pain 380–381 vision impairment 122–123 Kaposi’s sarcoma 168–169 nociceptor 381 chiropractic 365, 378 laryngectomy 31 pain and pain management 361 chlamydia 80, 352 pemphigus 182, 183 peripheral nerves 276 Chlamydia trachomatis 352 retinoblastoma 114 central neurotransmitters 367 chloasma 145 skin cancer 196–198 central serous retinopathy 115 cholesteatoma 15, 48 terminal pain 384 cerebellum 215, 232 cholesterol blood levels 124, 211 cancer treatment options and cerebral cortex chondritis 318 decisions 176, 310, 372–373, 384 forebrain 230, 231 chondrocyte 293, 298, 316 Candida albicans 57, 58, 180, 181t hyperhidrosis 164 chondroitin 366 Index 399 chondrosarcoma 309 cochlea 3, 16–17, 30, 37 torticollis 360 chorea 241–242 cochlear implant 6, 17 congenital cataracts 77 chorionic villi sampling (CVS) 155 cognitive function and dysfunction congenital dermal melanocytosis choroid 113, 120 242–244, 243t 139 chromosome 4 256, 298 ataxia 226–227 congenital heart disease 16 chromosome 19 221 chronic fatigue syndrome congenital hip dysplasia 318–319 chronic bacterial sinusitis 52 369–370 congenital nystagmus 102 chronic cough 18–19 CJD 248–249 congenital ptosis 110 chronic fatigue syndrome 369–370 consciousness 245 congenital vision loss 106, 114 chronic injury 304–305 delirium 250–251 congestion, nasal 53 chronic pain 370–371, 371t dementia 251–252 conjunctiva 80, 108, 110 acute pain 363 Huntington’s disease 256 conjunctivitis 80, 87, 95–97, 352 adhesive capsulitis 298–299 learning disorders 258–259 connective tissue aging, changes in pain memory and memory Achilles tendon 297 perception that occur with impairment 260–262 Achilles tendon injury 297–298 364, 365 neurologic examination 270 aging, integumentary changes alternative methods for pain organic brain syndrome that occur with 134–135 relief 365 272–273 dermatofibroma 152 analgesic medications 367 sign language 51 fascia 321 cervical spondylosis 316–317 colds 19, 28–29, 32 fibromyalgia 321–322 complex regional pain syndrome cold sore 17–18 integumentary system 128 371–372 collagen 170, 316, 342 Kaposi’s sarcoma 168–169 fibromyalgia 321–322 color deficiency 80 Marfan syndrome 335–336 living with pain 378 coma 244, 244t, 277, 288 connective tissue disorders 117 maldynia 378–379 comminuted fracture 322 consciousness 245. See also neural blockade 380 common cold 5 unconsciousness neurolysis 380 common migraine 374 contact dermatitis 150, 185 polymyositis 350 compact bone 308, 309 contact lens 67, 83–84, 90, 109 psychogenic pain 383 completely in the canal (CIC) contact lens, implantable 101, 112 temporomandibular disorders hearing aid 27 continuous infusion of local 359 complex regional pain syndrome anesthesia 367 TENS 384–385 371–372 continuous positive airway pressure trigger-point injection 385 complex syndactyly 350 (CPAP) device 39 cicatricial pemphigoid 79, 87 compression fracture 322 contracture 319 CIC (completely in the canal) computed tomography (CT) scan cool laser. See excimer laser hearing aid 27 311 cornea 80–81 cilia 15 conception 217 astigmatism 73 ciliary body 120 concussion 244–245, 245t bullous keratopathy 76 circadian cycles 65 conditioned-play audiometry 9 cicatricial pemphigoid 79 cirrhosis 221 conductive hearing loss 28–29 cold sore 17 CJD. See Creutzfeldt-Jakob disease cones 91, 113, 114 conjunctivitis 80 classic migraine 374 congenital anomaly corneal injury 81 cleaning the ear 15, 21 albinism 135–136 corrective lenses 82 cleft palate/cleft palate and lip 6, arthrogryposis 303–304 ectropion 87 16, 60 cleft palate/cleft palate and lip entropion 87 clonic-tonic seizures 281 16 eye 89 clonidine (Catapres) 287 congenital hip dysplasia keratitis 99 closed-angle glaucoma 92, 93t 318–319 keratoconus 99 closed fracture 322 kyphosis 332 ocular herpes simplex 103 Clostridium botulinum 141 laryngocele 32 pterygium 110 clubfoot. See talipes equinovarus lordosis 334 PTK 108 cluster headache 374, 376t, 377 optic nerve hypoplasia 106 cornea donation 81 CMT (Charcot-Marie-Tooth) disease retinoblastoma 114 corneal injury 81, 91, 103 317–318 talipes equinovarus 358 corneal transplantation 81–82 coagulation 183 temporomandibular disorders corns 145–146 cocaine 49, 361 359 coronary artery disease (CAD) 211 400 Index corrective lenses 67, 82–84, 96, D diffuse scleritis 117 101, 109, 111 dacryocystitis 85 diffuse uveitis 120 cortical reflex myoclonus 265 dacryostenosis 85 digestion 366 corticosteroid medications dandruff 147–148, 148t, 151 diphenhydramine (Benadryl) 25, bulla 142 dark adaptation test 85–86 206 bullous pemphigoid 142 DBS. See deep brain stimulation diphtheria 6 DLE 153 deciduous teeth 294 diplopia 86, 86t, 94, 118 glossitis 25 decubitus ulcer 148–149, 148t discoid lupus erythematosus (DLE) ischemic optic neuropathy 98 deep brain stimulation (DBS) 250, 152–153, 153t osteoporosis 346 276 disease-modifying antirheumatic plaque, skin 186 deformity 185 drugs (DMARDs) 302, 357 retrobulbar optic neuritis 116 degenerative neurologic disease dislocations 320 spinal cord injury 284 251, 256, 275–276 Dix-Hallpike test 12 synovitis 357 delirium 250–251 DLE (discoid lupus erythematosus) Corynebacteria 157 delta waves 253 152–153 costochondritis 318 dementia 218, 251–252 donepezil (Aricept) 222 cotton swab 48 dendrite 270, 271, 361 dong quai 366 cough 18–19 dental caries 20, 39, 44, 57, 294, dopamine CPAP (continuous positive airway 358 aging, neurologic changes that pressure) device 39 depression 174, 265, 383 occur with 221 cradle cap 146 dermabrasion 149, 210 dystonia 320 cramp 319, 356 dermatitis 74, 79, 141, 146, integumentary system 127 cranial nerves 246–247, 247t 149–152, 152 midbrain 232 acoustic neuroma 7 dermatofibroma 152 nervous system 217 Bell’s palsy 228 dermatome 252, 268 neurotransmitter 272 brain 230 dermatophytes 204 nevus 178 functions of the mouth 5 dermis Parkinson’s disease 275 hindbrain 232 integumentary system 127–128 dopamine agonists 279 midbrain 232 melanocyte 175–176 dopamine antagonists 252 multiple sclerosis 263 skin 195 dorsal ganglia 361, 382 optic nerve 105 sunburn 201 dorsal spinal nerve root 284 peripheral nerves 276 sweat glands 202 double vision. See diplopia peripheral nervous system 276 designer estrogens 346 Down syndrome 16 salivary glands 49 desquamtion 26 drooling 50 smell and taste disturbances 53 DEXA (dual-energy X-ray drug interaction 365, 366 sneeze 54 absorptiometry) 311 dry (atrophic) ARMD 70 cranium 235, 256–257 dextromethorphan 19 dry eye syndrome 76, 79, 86 crepitus 319 diabetes dual-energy X-ray absorptiometry Creutzfeldt-Jakob disease (CJD) aging, neurologic changes that (DEXA) 311 248–249, 263 occur with 221 Duchenne’s muscular dystrophy croup 19 amputation 300 337, 338t cryotherapy 187 carbuncle 143 Dupuytren’s contracture 319 CT (computed tomography) scan cataract 77 dura mater 262, 263 311 cellulitis 143 dwarfism. See skeletal dysplasia curvature of the spine. See scoliosis cognitive function and dyskinesia 252, 256 cuspid 294 dysfunction 244 dyslexia 258 cutaneous lupus erythematosus. See erythrasma 157 dysmenorrhea 366 discoid lupus erythematosus furuncle 160 dysphagia. See swallowing disorders CVD. See cardiovascular disease gingivitis 25 dysplasia 318–319 CVS (chorionic villi sampling) 155 osteomyelitis 344 dyspraxia. See apraxia cyst 62, 131, 185–186, 307 paresthesia 275 dystonia 256, 286, 320 cystic fibrosis 36 retinopathy 115 dystrophic epidermolysis bullosa cytochrome P450 (CYP450) diaper rash 152 154 enzymes 362 diaphysis 308 cytokines 127, 316 diarrhea 152 E cytophotocoagulation 94 diencephalon 231–232 ear 20 Index 401

barotrauma 11 electrolarynx 21, 64 epidermolysis bullosa 154–155 cauliflower ear 14 electrolytes 365 epidermolysis bullosa simplex 154 cerumen 14–15 electronystagmography 12 epidural brain hemorrhage 234t cholesteatoma 15 electroretinography 87 epiglottis 5, 21–22 cleaning 15 embryo 212 epiglottitis 21–22 cochlea 16–17 embryonic development 125, 293 epilepsy 218, 281 eustachian tube 23 emergencies, medical epinephrine 161, 206, 272 foreign objects in 24 acute pain 363 epiphysis 308, 341 functions of 3–4 back pain 306 episcleritis 88 mastoiditis 33 Bell’s palsy 228 epistaxis 22 myringitis 35 black eye 74 epithelium 229 myringotomy 35 brain hemorrhage 233–234 Epley maneuver 12 noise exposure and hearing concussion 245 ergosterol 128 36–37 corneal injury 81 erysipelas 155–156 otitis 40 cough 18 erythema multiforme 156 otoplasty 41 epiglottitis 21–22 erythema nodosum 156, 156t otorrhea 41 eye pain 90 erythrasma 156–157 otosclerosis 41 fracture 322 erythrodermic psoriasis 188 otoscopy 41, 43 glaucoma 92 Erythroxylum coca 361 ototoxicity 43 glossitis 25 esophageal speech 22, 31, 64 tinnitus 58 headache 373 esotropia 118 tympanic membrane 59 herniated nucleus pulposus 326 ESRD (end-stage renal disease) 344 ear, nose, mouth, and throat 1–64, orbital cellulitis 106 essential myoclonus 265 2 pharyngitis 45 estrogens 145, 345, 346 breakthrough research and photophobia 108 eudynia 363, 372, 379. See also treatment advances 6 retinal detachment 113 acute pain ear 3–4 Reye’s syndrome 279–280 eumelanin 175 functions of 1–5 spinal cord injury 283 eustachian tube 3, 7–8, 15, 20, 22, health and disorders of 5 stupor 285 40 mouth and throat 4–5 toothache 57 Ewing’s sarcoma 309 nose 4 urticaria 206 excimer (cool) laser 108, 109, 184 overview 1–6 vision impairment 123 Exelon (rivastigmine) 222 structures of 1 enamel 358 exercise and health 357, 365, 371, traditions in medical history 5–6 encephalitis 6, 33, 272 378, 379 earache 20–21 encephalopathy 218, 233, 254, exfoliatve dermatitis 150 ear cartilage 185 254t, 280 exophthalmos 88, 94, 95, 106 ear lavage 15, 21 end of life concerns 223–225, 233, exotropia 118 early childhood nervous system 277, 384 expectorant 19 220 endolymphatic hydrops. See explicit memory 260 early-onset Alzheimer’s disease 222 Ménière’s disease extracapsular cataract extraction 78 ear muffs 37 endorphin 362, 371, 379 eye 66, 70–124, 89t ear plugs 37 end-stage renal disease (ESRD) 344 aging, vision and eye change ear protection 37 enkephalin 362, 371 that occur with 71–72 ear wax. See cerumen entropion 87 astigmatism 73 eating habits 265 enucleation 88, 109–110, 114 black eye 74 ecchymosis 154 epicondylitis 320–321 breakthrough research and eccrine sweat glands 128, 164, 202 epidermis treatment advances 69 ectropion 87 aging, integumentary changes cataract 77–78 edema 201 that occur with 135 cluster headache 374 EEG (electroencephalogram) epidermolysis bullosa 154 cornea 80–81 253–254 erythrasma 156–157 corneal injury 81 elastin 316, 335 integumentary system 127 corrective lenses 82–84 elderly nervous system 221, keratinocyte 170 enucleation 88 364–365 papilloma 180 functions 65, 67–68 electroencephalogram (EEG) papule 180 Graves’s ophthalmopathy 253–254 skin 195 94–95 402 Index

health and disorders of 68 fibula 301, 330 CMT disease 317–318 how the eye “sees” 67 filiform papillae 26 ichthyosis 166 lens 100 finasteride (Propecia) 137 Marfan syndrome 335–336 overview 65–69 finger 210, 350, 357 muscular dystrophy 337–339 physics of vision 67–68 fingernails 129, 167 myopathy 340 retina 113 Fitzpatrick skin type 158, 158t myotonia 340 structures 65 flashes 91 neurofibromatosis 269 traditions in medical history flat bones 309 nevus 178 68–69 flexibility 300, 365, 366 osteogenesis imperfecta eyeglasses 67, 83, 109 flexural psoriasis 188 342–343 eyelids floaters 74, 91, 113, 124 osteopetrosis 344–345 blepharitis 74 fluorescein staining 81, 91, 104, polydactyly 350, 350 blepharoplasty 75 108 skeletal dysplasia 355 blepharospasm 75 focal seizures 281 syndactyly 357 chalazion 79 folic acid 16, 217, 282, 355 genetic predisposition 222 cicatricial pemphigoid 79 follicles. See hair follicles genetics and molecular medicine ectropion 87 folliculitis 158–159 296 entropion 87 food safety 248, 249 genetic testing 136, 155 hordeolum 96 foot 297, 349–350, 358 GERD. See gastroesophageal reflux orbital cellulitis 106 Achilles tendon injury 297, 298 disorder ptosis 110 foot drop 319 germline mutations 114 xanthelasma 124 forebrain 230–231 giant-cell arteritis 98 xanthoma 211 foreign objects in the ear or nose giant congenital nevus 178 eye pain 85, 89–90, 89t 24, 47 gingivitis 25 eye patch 72, 81 fovea 113 ginkgo biloba 223, 244 eye strain 90 fracture 322–323 glaucoma 92–94, 93t bone 309 cataract 78 F bone cancer 309 eye pain 90 face 373 bone density 310 eyes 67 facelift. See rhytidoplasty dislocations 320 Graves’s ophthalmopathy 94 facial nerve 49, 53, 228–229, 246, hip fracture in older adults 327 intraocular pressure 97 247t osteoporosis 346 mydriasis 100 facioscapulohumeral muscular RICE 353 ocular herpes zoster 103 dystrophy 337, 338t sprains and strains 356 tonometry 119 failed back surgery syndrome freckles. See lentigines glial cells 230 (FBSS) 327 Friedrich ataxia 226 globus pallidus 274 farsightedness. See hyperopia; frontal lobe 231t, 242 glossitis 25 presbyopia frostbite 159–160, 159t glossopharyngeal nerve 49, 53 fascia 294, 321, 349–350 functional limitations 67 glucosamine 366 fat. See adipose tissue fungal infection 179, 204–205 glucose 77, 285, 377 fat emboli 346 furuncle 160 glutamate 224 fatigue. See chronic fatigue gonorrhea 80 syndrome G goose bumps 160–161 fbn1 gene 335 gag reflex 25 gout 323–324, 324t FBSS (failed back surgery ganglion 267 grade 1 braille code 75 syndrome) 327 gangrene 144, 159, 323 grade 1 sprain 355–356 FDA. See US Food and Drug gas-permeable contact lens 83, 99 grade 2 sprain 356 Administration gastroesophageal reflux disorder grade 3 sprain 356 female pattern alopecia 137 (GERD) 18, 45 grade 4 sprain 356 femoral hernia 325 gastrointestinal bleeding 368 graft vs. host disease 173 femur 330 Gehrig, Lou 224 granuloma telangiectaticum 161 fetus 303 gene mutation. See mutation Graves’s disease 88, 94–95 feverfew 366, 377 gene therapy 296 Graves’s ophthalmopathy 88, fibrillin 1 335 genetic counseling 256 94–95, 119 fibrinogens 127 genetic disorders gray matter 216, 283, 284 fibromyalgia 321–322, 385 achondroplasia 298 greenstick fracture 322 Index 403 guaifenesin 19 labyrinthitis 31 HPV. See human papillomavirus Gualtheria procumbens 361 Ménière’s disease 33–35 HRT (hormone replacement Guillain-Barré syndrome 255 myringitis 35 therapy) 346 gum disease 39, 44 noise exposure and hearing human genome 130 gum tissue 25, 39 36–37 human growth hormone (hGH) gustation 4–5 otosclerosis 41 248 guttate psoriasis 188–189 ototoxicity 42t, 43 human growth hormone (hGH) presbycusis 45–46 supplement 298 H sign language 51 human herpesvirus 8 (HHV-8) 168 HAART (highly active antiretroviral speech disorders 54–55 human leukocyte antigens (HLAs) therapy) 168 tinnitus 58 267, 303, 352 Haemophilus influenzae type b (Hib) hearing loss, age-related. See human papillomavirus (HPV) 133, 21 presbycusis 180, 209 hair 125, 127–129, 162, 162t, heart 353. See also cardiovascular humerus 353 166–167 disease Huntington’s disease 218, 242, 256 hair cell (ear) 16–17, 30, 36, 37, 58 heart attack 57, 211 hyaline cartilage 293, 316 hair follicles heat laser 172 hydrocephaly 256–257, 298 acne 131 heat rash. See miliaria hydrophilic contact lens 83–84 carbuncle 143 heavy-metal poisoning 275 hydroquinone 145 furuncle 160 heel 349 hydroxyzine (Vistaril) 206 goose bumps 160–161 Heimlich maneuver 18 hygiene 132–133 hidradenitis suppurativa 164 hematoma 234 hyperhidrosis 128, 141, 164–165 integumentary system 125, 129 hemorrhagic stroke 234 hyperkeratosis 170, 173–174 keratosis pilaris 170, 171 hepatitis C 173 hyperkinesis 252 nasal vestibulitis 36 hepatoxicity 368 hyperlipidemia 124, 211 sebaceous glands 194 herbal remedies 26, 366 hyperopia 73, 82, 96, 111 skin 195 Hermansky-Pudlak syndrome hyperpigmentation 145, 175 skin cancer 196–197 (HPS) 136 hypersensitivity reaction sweat glands 202 hernia 325–326 analgesic medications 368 hair loss. See alopecia herniated nucleus pulposus erythema multiforme 156 hair replacement 162–164, 163t 326–327 headache 377 hair root 129 herpes simplex 17–18, 74, 99, 103, myoclonus 265 hairy leukoplakia 32 207, 210 neural blockade 380 hairy tongue 26 herpes zoster 74, 99, 103, 269 piercings 185 halitosis 20, 26, 44 hiatal hernia 325 urticaria 205–206 Haversian systems 308 hidradenitis suppurativa 164 hypertension head 373 highly active antiretroviral therapy aging, neurologic changes that headache 235, 373–377, 376t (HAART) 168 occur with 221 headache journal 375 hindbrain 232 brain 233 healing 194, 361 hinge joint 294 brain hemorrhage 235 hearing aid 6, 10, 26–28, 29–30 hip fracture in older adults 327 cognitive function and hearing impairment (sign language) hippocampus 231, 260 dysfunction 244 51 Hippocrates 218 ototoxicity 42t hearing loss 28–30 histamine 187, 206 retinopathy 115 acoustic neuroma 7 HIV/AIDS 32, 168, 169, 384 tinnitus 58 audiologic assessment 9–10 hives. See urticaria hyperthyroidism 88, 94–95 barotrauma 11 HLA-B27 gene 303 hypertrophic scar 194 BPPV 12 HLAs. See human leukocyte antigens hypnosis 365, 375 breakthrough research and hordeolum 79, 96, 106 hypoglossal nerve 246, 247t treatment advances 6 hormone 131, 145, 310, 362, 374 hypopigmentation 175, 207–208 cholesteatoma 15 hormone replacement therapy hypothalamus 161, 231–232 cochlear implant 17 (HRT) 346 hypothermia (frostbite) 159–160 disorders of the ears, nose, hormone therapy 355 hypoxia 238 mouth, and throat 5 hot tub folliculitis 159 ear 20 HPS (Hermansky-Pudlak I hearing aid 26–28 syndrome) 136 iatrogenic CJD 248 404 Index

IBD (inflammatory bowel disease) polymyositis 350 intraoral electrolarynx 21 303 RICE 353 intrathecal analgesia 367 ibuprofen 375 rotator cuff impingement intravenous injection 367 ICD (implantable cardioverter syndrome 353 IOL (intraocular lens) 77–79 defibrillator) 385 synovitis 357 ion channels 340 ichthyosis 166 tendonitis 359–360 ions 216 immune disorders 25, 58, 150, 168, inflammatory bowel disease (IBD) iontophoresis 165 268–269. See also autoimmune 303 IPV (inactive poliovirus vaccine) disorders inflammatory myopathy 350 277 immune response inflammatory response 363 iridotomy 94 acute pain 363 ingrown hair 166–167, 188 iris 97, 120 lichen planus 173 ingrown nail 167 iritis 97 lichen simplex chronicus 174 inguinal hernia 325 ischemic optic neuropathy 97–98 phototherapy 184 inheritance pattern 222, 225, 256, isotretinoin 132 psoriasis 188 269, 335 itching. See pruritus rash 191 injected analgesic medications 367 tendonitis 359 inner ear 20 J toxic epidermal necrolysis 205 BPPV 11–12 jaw 57, 294, 359 immune system 255, 350 cochlea 16–17 jaw pain 57 immunocompromised 144, 170 functions of the ear 3–4 jock itch. See tinea immunoglobulin 255 labyrinthitis 31 joint 328, 328t immunoglobulin A (IgA) 79 Ménière’s disease 33–35 adhesive capsulitis 298–299 immunoglobulin E (IgE) 206 proprioception 350 arthroscopy 304 immunoglobulin G (IgG) 79 vertigo 60–61 contracture 319 immunosuppressive therapy 151, inner ear barotrauma 11 crepitus 319 168, 170 inner eye 91 dislocations 320 impetigo 166 integumentary system 125–211, gout 323–324 implantable cardioverter 126 infectious arthritis 328 defibrillator (ICD) 385 breakthrough research and musculoskeletal system 294 implantable middle ear hearing aid treatment advances 130 neurogenic arthropathy 340 27 dermis 127–128, 128t repetitive motion injuries 352 implicit memory 260 embryonic development 125 rotator cuff impingement inactive poliovirus vaccine (IPV) epidermis 127, 127t syndrome 353 277 fingernails and toenails 129 sprains and strains 355 incarcerated hernia 325–326 functions of 125–129 joint replacement 300, 328–329 incisional hernia 325 hair 128–129 jumper’s knee. See Osgood-Schlatter incisor 294 health and disorders 129–130, disease infantile osteopetrosis 344–345 130t junctional epidermolysis bullosa infantile seborrheic dermatitis. See overview 125–130 154 cradle cap structures of 125 infants 152, 245, 364 subcutaneous layer 128 K infection 143, 185, 203, 343–344 traditions in medical history 129 Kaposi’s sarcoma 168–169, 169t infectious arthritis 328, 341–342, intestinal polyp 180 keloid 170 352 in the canal (ITC) hearing aid 27 keloid scar 194 inflammation in the ear (ITE) hearing aid 27 keratin 127, 129, 170 bursa 312 intracerebral brain hemorrhage keratinocyte 170 bursitis 312 234t integumentary system 127, 129, cellulitis 143–144 intramuscular injection 367 130 chondritis 318 intraocular hypertension 119 pemphigus 182 epicondylitis 320–321 intraocular lens (IOL) 77–79 psoriasis 188 erythema nodosum 156 intraocular pressure 97 scale 194 infectious arthritis 328 glaucoma 92, 93 sebaceous glands 195 miliaria 176 Graves’s ophthalmopathy 94 skin 195 otitis 40 ophthalmic examination 104 squamous cell carcinoma 197 pain 382 orbital cellulitis 106 sunburn 200–201 plantar fasciitis 349–350 tonometry 119 toxic epidermal necrolysis 205 Index 405 keratitis 94, 99, 103 corrective lenses 82 Lou Gehrig’s disease. See keratoacanthoma 170 eye 89 amyotrophic lateral sclerosis keratoconus 83, 99 presbyopia 108 lower back 356 keratocyte 141, 143, 145, 170, 175 lens replacement 78, 112 lumbar puncture 241, 259 keratosis pilaris 170–171 lentigines 134, 172–173 lumbar spine 306, 334, 354 kneecap (patellofemoral syndrome) lesion 173, 173t lungs 168 348–349 acne 131 lupus disorders 152–153 knee injuries 330–332, 331t, 332t actinic keratosis 133–134 lutein 102 Baker’s cyst 307 erythema multiforme 156 lymphoma 150 meniscectomy 336 ichthyosis 166 neurogenic arthropathy 340 Kaposi’s sarcoma 168 M Osgood-Schlatter disease 341 keratoacanthoma 170 macula 70–71, 113 patellofemoral syndrome macule 175 macular degeneration. See age- 348–349 nevus 178–179 related macular degeneration kyphosis 298, 332, 345 petechiae 183 macule 174, 175, 186 pityriasis rosea 186 mad cow disease. See bovine L plaque, skin 186 spongiform encephalopathy labyrinthitis 31 prurigo 186–187 magnet therapy 365 lacrimal (tear) ducts 85, 86 psoriasis 188, 189 malaria 42t lamellae 308 purpura 190 Malassezia 148 laminectomy 333 scale 194 Malassezia fuffur 205 Langerhans cells 127 scar 194 malathion (Ovid) 181 language disorders (aphasia) 225 seborrheic keratosis 195 maldynia 363, 364, 378–379, 379t, lanugo 125 staphylococcal scalded skin 380 laryngectomy 21, 23, 31–32, 64 syndrome 200 male pattern hair loss (androgenic laryngitis 32, 64 thrush 58 alopecia) 137 laryngocele 32 vesicle 207 malignant melanoma 141, laryngoscopy 63 wheal 209–210 178–179, 197–198, 198t larynx xanthoma 211 malignant tumor. See tumor, Bogart-Bacall syndrome 13 leukemia 150 cancerous electrolarynx 21 leukoplakia 32 malnutrition 119 laryngectomy 31–32 levodopa 279 mandible 294, 359 laryngitis 32 Lewy body dementia 251, 252 Marfan syndrome 235, 295, laryngocele 32 lice 180–182 335–336 throat 57 lichen planus 173 Marie-Strümpel disease. See vocal cords 63–64 lichen simplex chronicus 173–174 ankylosing spondylitis voice therapy 64 life support 224–225, 233 massage therapy 366 laser skin resurfacing 172, 210 ligament 294, 301, 330, 332t, 333, mastoid bone 33 laser surgery 71, 108, 111–112, 114 355 mastoiditis 6, 33 laser therapy 192, 203 limbic system 242 maxilla 294 LASIK (laser-assisted in situ Lioresal. See baclofen maxillary sinuses 51 keratomileusis) eye surgery 69, lipoma 333–334 measles 30 109, 111, 112 Little, William 238 medial epicondylitis 320 lateral epicondylitis (tennis elbow) liver 280 medial meniscus 330 320 liver failure 368 median nerve 315–316 lateral meniscus 330 liver spots. See lentigines medical emergencies. See lazy eye. See amblyopia living with pain 378 emergencies, medical learning disorders 54, 258–259 lobes, of cerebral cortex 231, 231t, medical imaging 295–296 left brain 225 242, 243t meditation 375 legal blindness 67, 122, 122t, 123t lobular capillary hemangioma. See medulla oblongota 232 Legionnaires’ disease 42t granuloma telangiectaticum medullary canal 308 leg pain 356 location, sense of. See melanin lens 100 proprioception albinism 135 cataract 77–78 long bones 308, 309, 341 integumentary system 127, 129 cataract extraction and lens long-term memory 260 keratinocyte 170 replacement 78–79 lordosis 298, 334 melanocyte 175 406 Index

skin cancer 196 molar 294 muscle spasm. See spasm sunburn 200 monocular diplopia 86 muscular dystrophy 295, 337–339, melanocyte 175–176 monocular vision 121 338t aging, integumentary changes monovision 83, 109 musculoskeletal system 290–360, that occur with 135 morphine 363, 377 291, 292 chloasma 145 motion sickness 4 biomechanics of movement 294 integumentary system 127, 129 motor nerves 246, 247t, 252 bone 307–309 nevus 178 motor neuron disease 265, 297. See breakthrough research and skin 195 also amyotrophic lateral sclerosis treatment advances 295–296 sunburn 200 motor neurons 223–224 functions of 293 vitiligo 207 mouth 35 health and disorders of melanogenesis 175 canker sore 14 294–295, 295t melanoma. See malignant cold sore 17–18 joint 328 melanoma halitosis 26 joints 294 melasma. See chloasma leukoplakia 32 ligament 333 melatonin 65 myoclonus 266 muscle 336–337 membranous labyrinth 4, 33 oral hygiene 39 muscles 293–294 memory and memory impairment salivary glands 49 overview 290–296 251–252, 260–262, 261t, 270, teeth 358 skeleton 293, 355 272–273 temporomandibular disorders structures of 290–293 memory loss 261 359 teeth 294, 358 Ménière’s disease 33–35 thrush 57–58 tendons, ligaments, and fasciae meninges 33, 230, 234, 241, mouth and throat 4–5 294 262–263 movement, biomechanics of 294 traditions in medical history 295 meningitis 6, 33, 108 mucous membranes 49, 182 mutation meningocele 282 mucus 47, 51 achondroplasia 298 meniscectomy 336 multiple sclerosis 263–265, 264t, albinism 135–136 meniscus 330, 336 269 Alzheimer’s disease 221–222 menopause 343–345, 374 muscle 336–337 cerebral palsy 238 menstrual cycle 132 aging, musculoskeletal changes CJD 248 menstruation 131, 132, 374 that occur with 299–300 CMT disease 317 metabolism 364 bursa 311–312 color deficiency 80 metastasis 170, 197, 310 bursitis 312 Huntington’s disease 256 metastatic brain cancer 237 contracture 319 Marfan syndrome 335–336 metastatic cancer 309 cramp 319 musculoskeletal system 296 metastatic tumor 235, 237 dystonia 320 myotonic muscular dystrophy metencephalon 232 fibromyalgia 321–322 337–338 methylprednisolone 284 hernia 325–326 nervous system 218 microinfarction 86 lipoma 333 pemphigus 183 midbrain 232. See also brainstem musculoskeletal system 293–294 psoriasis 188 middle ear 15, 20, 23, 35, 41 myasthenia gravis 339 tremor disorders 289 middle ear barotrauma 11 myopathy 339–340 vitiligo 208 migraine headache 365, 366, myotonia 340 myasthenia gravis 339 373–374, 376t, 377 polymyositis 350 mydriasis 100, 107 migratory keratinocytes 170 rhabdomyoma 353 myelencephalon 232 miliaria 176 spasm 356 myelin 255, 263, 270, 317 miliaria crystallina 176 spastic cerebral palsy 238–239 myelomeningocele 282 miliaria rubra 176 sprains and strains 355 Myobloc (botulinum neurotoxin B) mineralization 359 tendon 359 141 minerals and health 313–315 tension headache 373 myocardial muscle 336 minimally invasive surgery torticollis 360 myoclonus 265–266, 266t (arthroscopy) 304 trigger-point injection 385 myofascial pain syndrome 385 minoxidil (Rogaine) 137 muscle fibers 336 myopathy 339–340, 350 mixed cerebral palsy 239 muscle function 274 myopia 73, 82, 100–101, 111, 113, Mohs, Frederic E. 176 muscle relaxant medications 75, 114 Mohs’ micrographic surgery 176 337, 337t myotonia 340 Index 407 myotonic muscular dystrophy reflex 279 myasthenia gravis 339 337–338, 338t seizure disorders 281–282 nervous system 217 myringitis 35 sialorrhea 50 neuron 270 myringotomy 33, 35, 35, 40, 41, 59 spinal cord 283 neuroreceptor 271 spinal cord injury 283–284 pain 382 N structures of 212 restless legs syndrome 279 nails 177–178, 177t, 179, 180 traditions in medical history 218 Tourette’s syndrome 287 narcolepsy 267 vertigo 60–61 nevus 139, 141, 178–179, 197 narcotics 363, 366, 367, 384. See neural blockade (nerve block) 380 night blindness 102, 114 also opiates neuralgia 268–269 NIH. See US National Institutes of nasal passages 12–13 neural tube 212, 217 Health nasal polyp 36 neural tube defects 217, 220, nits 181 nasal septal prosthesis (nasal 282–283 Nix (permethrin) 181 button) 49–59 neuritis 269, 269 nociceptor 381 nasal septum 49–50 neurocutaneous melanosis 178 acupuncture 365 nasal vestibulitis 36 neurofibrillary tangles 221 aging, changes in pain nasopharynx 22 neurofibromatosis 7, 139, 269 perception that occur with nausea 34, 61, 374 neurogenic arthropathy 340, 340t 364 nearsightedness. See myopia neurogenic pain 366, 380–381, neurogenic pain 380–381 neck 360, 365, 373 381t pain and pain management necrosis 323 neuroglia 230 361, 362 necrotizing scleritis 117 neurologic examination 253–254, phantom pain 382 neonatal jaundice 238 259, 270 pruritus 187 neovascular (wet) ARMD 70 neurolysis 380 tension headache 373 nerve 267 neuromuscular disorders 55, nodule 179 nerve damage 53, 306 317–318 acne 131 nerve impulses 260, 361. See also neuromuscular junction 336 erythema nodosum 156 neurotransmitter neuron 270 granuloma telangiectaticum 161 nervous system 212–289, 213, 214, aging, neurologic changes that hidradenitis suppurativa 164 267–268 occur with 220, 221 vocal cord nodule 63 aging, changes in pain ALS 223 nodulocystic acne 131 perception that occur with brain 230, 232 noise exposure and hearing 30, 364 maldynia 378 36–37, 45, 48 aging, neurologic changes that muscle 336 nonarteric ischemic optic occur with 220 nerve 267 neuropathy 98 analgesic medications 367 nervous system 215–217 noncancerous tumor. See tumor, brain 230–233 nociceptor 381 noncancerous breakthrough research and pain and pain management 361 nonsteroidal anti-inflammatory treatment advances 218–219 neuronal networks 220 drugs (NSAIDs) 366–368 cerebral palsy 238 neuropathy 270–271, 271t, 340 nonstriated muscle. See smooth cerebrospinal fluid 241 neuroreceptor 271 muscle communication within 216–217 aging, neurologic changes that nose 4, 37–38 cranial nerves 246–247 occur with 221 blowing of 12–13 functions of 212 analgesic medications 367 blowing the nose 12–13 health and disorders of nervous system 217 broken nose 13 217–218, 218t neuron 270 cluster headache 374 integumentary system 128 neurotransmitter 271 epistaxis 22 meninges 262–263 pain 382 foreign objects in 24 neurofibromatosis 269 pain and pain management 362 functions of 4 neurotransmitter 271–272 neurotransmitter 271–272, 271t nasal polyp 36 organization and structure 212, acute pain 363 postnasal drip 45 215–216, 216t Alzheimer’s disease 221, 223 rhinoplasty 47 overview 212–219 botulinum therapy 141 rhinorrhea 47 paralysis 274–275 brain 232 septal deviation 49 peripheral nervous system delirium 250 septal perforation 49–50 276–277 integumentary system 127 sinuses 51 408 Index

sneeze 54 refraction test 111 osteocyte 293, 307, 308 nostrils 36 slit lamp examination 117–118 osteogenesis imperfecta 342–343 NSAIDs. See nonsteroidal anti- Snellen chart 118 osteoid 309, 343 inflammatory drugs tonometry 119 osteomalacia 315, 343 nummular dermatitis 151 vision health 122 osteomyelitis 343–344, 345 nutritional deficiency 309 ophthalmoscopy 104–105 osteopenia 310, 344 nutritional supplements 366 opiates 362, 366, 368. See also osteopetrosis 344–345 nystagmus 12, 62, 102, 102t narcotics osteophyte. See bone spur opium 361 osteoporosis 345–347, 346t O optical coherence tomography ankle injuries 302 OA (ocular albinism) 136 (OCT) 105 bone density 310 obesity 39, 301 optic disk 105, 107, 113 calcium and bone health 313 obstructive sleep apnea 39, 59 optic nerve 105, 105t. See also optic osteopenia 344 OCA (oculocutaneous albinism) disk scoliosis 354 135–136 cranial nerves 246, 247t osteosarcoma 309 occipital lobe 231t eye 89 otitis 3, 8, 40, 41, 58 occupational health and safety. See eyes 65 otitis externa (swimmer’s ear) 21, also US Occupational Safety and glaucoma 92 40 Health Administration intraocular pressure 97 otitis interna 40 carpal tunnel syndrome ischemic optic neuropathy otitis media 40 315–316 97–98 achondroplasia 298 contact dermatitis 150 multiple sclerosis 263 eustachian tube 23 eye strain 90 retina 113 mastoiditis 33 noise exposure and hearing retrobulbar optic neuritis myringitis 35 36–37 115–116 myringotomy 35 repetitive motion injuries optic nerve atrophy 94, 105–106, ruptured eardrum 48 352–353 105t sinusitis 52 occupational therapy 223, 243, 341 optic nerve hypoplasia 106 traditions in medical history 5–6 OCT (optical coherence oral administration of medication tympanic membrane 59 tomography) 105 366 otoconia 11, 12 ocular albinism (OA) 136 oral contraception 132, 374 otoplasty 14, 41 ocular herpes simplex 103 oral hygiene 25, 26, 39, 44 otorrhea 41 ocular herpes zoster 103 orbital cellulitis 88, 106, 119 otosclerosis 9, 29, 41 ocular hypertension 97 organ harvest 81, 233, 248 otoscopy 41, 43 ocular hypotension 97 organic brain syndrome 272–273, ototoxicity 42t, 43 oculocutaneous albinism (OCA) 272t outer ear 20 135–136 organ of Corti 3, 17 outer ear barotrauma 11 oculomotor nerve 246, 247t Osgood-Schlatter disease 341 overdose 368, 384 off label use 153 OSHA. See US Occupational Safety overuse injury 359–360 oil of wintergreen 361 and Health Administration Ovid (malathion) 181 olfactory epithelium 53 ossification 293, 299, 308 oxycodone 363 olfactory nerve 37, 52, 53, 246, osteoarthritis 341–342 247t aging, musculoskeletal changes P onychocryptosis. See ingrown nail that occur with 300 pacemaker 385 onychomycosis 179 cartilage 316 Paget’s disease of the bone 348 open-angle glaucoma 92, 93t cervical spondylosis 316–317 pain 382. See also specific forms of open fracture 322 gout 323–324 pain, e.g. acute pain operation. See specific operations, e.g.: joint replacement 328 pain, living with 378 amputation musculoskeletal system 295 pain and pain management ophthalmic examination 103–104 spinal stenosis 356 361–385. See also specific pain dark adaptation test 85–86 temporomandibular disorders management medications and electroretinography 87 359 techniques, e.g.: analgesic fluorescein staining 91 osteoblast 293, 307, 308 medications ophthalmoscopy 104–105 osteochondritis 318 breakthrough research and optical coherence tomography osteochondrosis 341 treatment advances 362 (OCT) 105 osteoclast 307–308 mechanisms of 361 Index 409

overview 361–362 Pavlik harness 319 pia mater 262 traditions in medical history PCA. See patient controlled analgesia Pidgin Signed English (PSE) 51 361–362 pediculosis 180–182 piercings 14, 39, 184–185 pain perception 378 Pediculus humanus capitis 181 pigment birthmark 139 palatal myoclonus 266 Pediculus humanus corporis 181, 182 pilomotor reflex 160–161 palate 16 Pediculus pubis 181 pilonidal disease 185–186 pallidotomy 274 pelvis 309 pimple 131 Papaver somniferum 361 pemphigus 182–183 pineal gland 65, 229 papillae 4, 26 pemphigus foliaceus 182 pinguecula 108 papilledema 107, 115 pemphigus vulgaris 182, 183 pituitary gland 175, 229 papillitis 107, 269 peptic ulcer disease 42t pityriasis rosea 186 papilloma 180 Pepto Bismol (bismuth Pityrosporum 148 papule 180, 181, 186, 194 subsalicylate) 280 plantar fasciitis 349–350 paralysis 274–275 periodontal disease 25, 44 plaque, skin 173–174, 186, 189 Bell’s palsy 228–229 periosteum 308 plaque psoriasis 189 Guillain-Barré syndrome 255 peripheral nerves 276, 364, 365 plasmapheresis 205 poliomyelitis 277, 278 peripheral nervous system 215, plastic surgery 41, 47, 75 spina bifida 282 246–247, 276–277, 284, 361 platelet deficiency 190 spinal cord injury 283 peripheral neurotransmitters poliomyelitis 277–278 vocal cord paralysis 63 analgesic medications 367 polydactyly 350 paralytic poliomyelitis 277 CMT disease 317 polymyositis 350 paranasal sinuses 51 Guillain-Barré syndrome 255 polyp 36, 133 paraneoplastic pemphigus 182, 183 neuropathy 270–271 polyps 63 parasite 180–182, 194 proprioception 350 pons 232 parasympathetic nervous system restless legs syndrome 279 Ponseti casting method 358 216 spinal nerves 284 poptosis. See exophthalmos parathyroid hormone 307–308, 346 peripheral vascular disease (PVD) port wine stain 139 paresthesia 269, 275, 318 143, 275 posterior ampullar neurectomy 12 parietal lobe 231t peripheral vision 92–93 posterior canal plugging 12 Parkinson’s disease 275–276 peritonsillar abscess 44 postnasal drip 45, 51, 374 aphasia 225 permanent teeth 294, 358 postpolio syndrome 278 benign essential tumor vs. 288 permethrin (Nix) 181 precancerous conditions 32, deep brain stimulation 250 persistent vegetative state 244, 277 133–134, 180 dyskinesia 252 pertussis 6 pregnancy ectropion 87 petechiae 183 Bell’s palsy 229 integumentary system 127 phacoemulsification 78 cerebral palsy 238 memory and memory phakic intraocular contact lens chloasma 145 impairment 262 implantation 112 migraine headache 374 midbrain 232 phalanges 308–309 nervous system 217 nervous system 217–219 phantom pain 382–383 stretch marks 200 neurotransmitter 272 pharyngitis 5, 22, 45, 45 talipes equinovarus 358 pallidotomy 274 pharynx 45, 57 premature birth 115, 118 proprioception 350–351 phenol peel 144–145 premature sleep paralysis 267 seborrheic dermatitis 151 pheomelanin 175 premolar 294 smell and taste disturbances 53 photic sneezing 54 prenatal care 16, 241, 258, swallowing disorders 56 photocoagulation 71 282–283, 355 thalamotomy 286 photodynamic therapy 71 prenatal nervous system 220 paronychia 180, 181t. See also photophobia 95, 100, 107–108, presbycusis 8–9, 29, 45–46, 58 whitlow 136 presbyopia 83, 108–109, 112 Patau’s syndrome 350 photoreactive keratectomy (PRK) pressure sore. See decubitus ulcer patella 330 111–112 primary cancer 309 patellofemoral syndrome 348–349 photosensitivity 183–184, 193 primary teeth 358 pathologic paresthesia 275 phototherapeutic keratectomy primary tumor 235 pathologic vertigo 61 (PTK) 108, 108t prion 248, 249 patient controlled analgesia (PCA) phototherapy 184 PRK (photoreactive keratectomy) 367, 384 physical therapy 349 111–112 410 Index

Propecia (finasteride) 137 R resistance exercise 310, 332, 344, Propionibacterium acne 131, 132 radiation therapy 169, 237, 309, 345 proprioception 294, 340, 350–351 310 restless legs syndrome 279 prostaglandins 363, 366, 367, 373, radiculopathy 326 reticular-activating system (RAS) 382 rapid eye movement (REM) 267 245 prosthetic eye 69, 88, 109–110 rash 191, 191t retina 113, 113t prosthetic limb 351 impetigo 166 albinism 135 protective eyewear 121–122 lichen planus 173 ARMD 70–71 protein clumping 77 lichen simplex chronicus electroretinography 87 prurigo 186–187 173–174 eye 89 pruritus 187–188, 187t photosensitivity 183–184 flashes 91 PSE (Pidgin Signed English) 51 pityriasis rosea 186 optical coherence tomography pseudofolliculitis barbae 167, 188 scabies 194 (OCT) 105 Pseudomonas 180, 181t RAS (reticular-activating system) retinitis pigmentosa 114 Pseudomonas aeruginosa 159 245 retinopathy 114–115 psoralen plus ultraviolet A (PUVA) razor rash. See pseudofolliculitis scotoma 117 phototherapy 184, 187, 207 barbae retinal detachment 79, 91, psoriasis 188–190, 189t, 190t reactive arthritis 352 113–114, 124 psychogenic pain 383 rebound headache 374–375, 376t retinal ganglia cells 92 pterygium 110 rebound rhinorrhea 47 Retin-A (tretinoin) 145 PTK (phototherapeutic reconstructive surgery. See plastic retinitis pigmentosa 114 keratectomy) 108 surgery retinoblastoma 114, 118 ptosis 110 rectum 367 retinopathy 71, 87, 114, 114–115 puberty 131, 134, 164 red/green deficiency 80 retrobulbar optic neuritis 115–116, pubic pediculosis 182 reduction (fracture treatment) 323 263, 269 pulp (of tooth) 294, 358 reflex 279 Reye’s syndrome 59, 279–280 pulsed electromagnetic therapy Achilles tendon 297 rhabdomyoma 353 365 concussion 245 rheumatoid arthritis 117, 328, 354, pupil 100 cough 18–19 357, 370–371 pure-tone bone-conduction gag reflex 25 rhinitis, seasonal 52 audiometry 9 goose bumps 160–161 rhinoplasty 47 pure-toned audiometry 9 pain 382 rhinorrhea 5, 41, 45, 47 purines 324 pruritus 187 rhizotomy 241, 268, 280 purpura 190, 190t sciatica 354 rhytidoplasty 191–192, 210 pustular psoriasis 189 sneeze 54 RICE (rest, ice, compression, and pustule 158, 190 reflex sympathetic dystrophy 371 elevation) 353 PUVA. See psoralen plus ultraviolet refraction test 111, 118 acute pain 363 A phototherapy refractive errors 67, 99, 111, 111 ankle injuries 301 PVD. See peripheral vascular disease refractive surgery 96, 101, 111–113 eudynia 372 Reiter’s syndrome 352 sprains and strains 355, 356 Q relaxation techniques 375, 377 tendonitis 359 quality of life remodeling 316 rickets 315 amputation 300–301 REM (rapid eye movement) 267 ringworm. See tinea chronic fatigue syndrome Renaissance 295 rivastigmine (Exelon) 222 369–370 renal failure 368 rods 91, 113, 114 deep brain stimulation 250 renal toxicity 368 Rogaine (minoxidil) 137 joint replacement 329 repetitive motion injuries 352–353 root canal 44 living with pain 378 bone spur 311 rosacea 74, 79, 192–193, 192t maldynia 379 bursitis 312 rotator cuff impingement syndrome occupational therapy 341 carpal tunnel syndrome 315–316 275, 353 organic brain syndrome 273 knee injuries 330 rubella 30, 238 persistent vegetative state 277 plantar fasciitis 349–350 running 297 physical therapy 349 rotator cuff impingement ruptured eardrum 41, 47–48, 59 prosthetic limb 351 syndrome 353 smell and taste disturbances 52 tendonitis 359–360 S vision impairment 123 reproductive system 236–237 saccule 11 Index 411

Sacrcoptes scabei 194 shunt 257 sebaceous glands 194–195 St. John’s wort (hypercium) 183 sialadenitis 50 seborrheic keratosis 195 salicylic acid 361 sialolithiasis 50 stretch marks 200 saliva 49, 50 sialorrhea 49, 50, 55 sun protection 201–202 salivary calculus 50 sign language 51 sweat glands 202 salivary glands 4, 49, 50 sildenafil (Viagra) 80, 119 tattoos 203 scabies 194 simple syndactyly 350 tinea 204 scale 194 sinus congestion 374 tinea versicolor 204–205 scalp (dandruff) 147–148 sinuses 33, 36, 37, 51 toxic epidermal necrolysis 205 scapula 353 sinus headache 374, 376t vesicle 207 scar 194 sinusitis 18, 51–52, 53, 107 vitiligo 207–208 sciatica 354 situational vertigo 61 wart 209 sciatic nerve 354 Sjögren’s syndrome 50 wheal 209–210 sclera 65, 79, 88, 117, 123 skeletal dysplasia 298, 334, 355 whitlow 210 scleral shell 110 skeletal muscle 293–294, 336, 356 wrinkles 210–211 scleritis 117, 117t skeleton 355 xanthoma 211 sclerotherapy 203 aging, musculoskeletal changes skin cancer 196–198, 198t scoliosis 354–355 that occur with 299 aging, integumentary changes scotoma 117 bone 308 that occur with 135 seasonal rhinitis 52 calcium and bone health 313 birthmark 139, 141 sebaceous glands 194–195 muscle 336 Fitzpatrick skin type 158 acne 131, 133 musculoskeletal system 293 integumentary system 130 cradle cap 146 skeletal dysplasia 355 keratoacanthoma 170 dandruff 147, 148 skin 195, 196t lentigines 172 integumentary system 125 cellulitis 143–144 melanocyte 176 seborrheic dermatitis 147–148, 151 chemical peel 144–145 Mohs’ micrographic surgery 176 seborrheic keratosis 195 Fitzpatrick skin type 158 sun protection 201, 202 sebum 125, 128, 131, 162, 164, keloid 170 warning signs 127 194–195 keratinocyte 170 wrinkles 210 secondary ossification 299 keratosis pilaris 170–171 skin color 175 sectoral scleritis 117 laser skin resurfacing 172 skin grafts 198–199, 205, 207–208 sedation 384 lentigines 172–173 skin replacement 130, 198–199 seizure disorders 218, 265, lichen planus 173 skin self-examination 172, 178, 281–282, 281t miliaria 176 195, 198, 199–200, 200t selective estrogen receptor nails 176 skin tag. See acrochordon modulators (SERMs) 346 nevus 178–179 SLE. See systemic lupus selective serotonin reuptake nodule 179 erythematosus inhibitors (SSRIs) 217, 381 papule 180 sleep disorders 39, 267, 279 self-medication 368 pediculosis 180–182 sleep myoclonus 265 Semont maneuver 12 pemphigus 182–183 slit lamp examination 104, sensorineural hearing loss 28, 29, petechiae 183 117–118 58 photosensitivity 183–184 smallpox vaccine 150 sensory nerves 246, 247t phototherapy 184 smell and taste disturbances 52–54 septal deviation 49 piercings 184–185 smoking and health 64, 152, 153, septal perforation 49–50 pilonidal disease 185–186 313 septicemia 155 plaque 186 smooth muscle 336 septoplasty 49 prurigo 186–187 sneeze 13, 54 SERMs (selective estrogen receptor pruritus 187–188 Snellen, Herman 118 modulators) 346 pseudofolliculitis barbae 188 Snellen chart 104, 111, 118, 121 serotonin 217 psoriasis 188–190 snoring 39 sexually transmitted disease 352 purpura 190 soft palate 60 shaken baby syndrome 287 pustule 190 soft tissue 373 shingles 103 rash 191 soft tissue injuries. See repetitive short bones 308–309 scabies 194 motion injuries short-term memory 260 scale 194 solar keratosis. See actinic keratosis shoulder 298–299, 353 scar 194 somatic motor nerves 246, 247t 412 Index somatic nervous system 216, 277 actinic keratosis 133 subcutaneous injection 367 sore throat 45, 57 characteristics 198t subcutaneous layer 128, 195 spasm 286, 319, 320, 356, 365 epidermolysis bullosa 155 subdural brain hemorrhage 234t spastic cerebral palsy 238–239 integumentary system 130 substantia nigra 127, 178, 232 spastic diplegia 239 keratinocyte 170 subthalamic nucleus 241 spastic hemiplegia 239 keratoacanthoma 170 sunburn 200–201 spastic paraplegia 239 Mohs’ micrographic surgery 176 Fitzpatrick skin type 158 spastic quadriplegia 239 skin cancer 197 keratitis 99 speech audiometry 9 SSRIs. See selective serotonin photosensitivity 183–184 speech disorders 54–55, 63, reuptake inhibitors skin cancer 196, 198 225–226 stapes 41 sun protection 201–202 speech therapist 55 staphylococcal bacteria 166 vitiligo 207 SPF rating 201–202 staphylococcal scalded skin sunglasses 201 spider veins. See telangiectasis syndrome 200 sunlight 128, 175 spina bifida 217, 282–283 staphylococcus 143 sun protection 201–202 spina bifida occulta 282 Staphylococcus 143 actinic keratosis 134 spinal accessory nerve 246, 247t Staphylococcus aureus 180, 181t, 200 aging, integumentary changes spinal column 283 stasis dermatitis 151 that occur with 135 spinal cord 283 stem cells 130, 219 albinism 136 cerebrospinal fluid 241 stereotactic halo 250, 274, 286 calcium and bone health 315 herniated nucleus pulposus 326 sternum 309 laser skin resurfacing 172 laminectomy 333 steroid 78 skin cancer 196, 198 meninges 262–263 Stevens-Johnson syndrome. See sunscreen 201–202 nervous system 212, 215, 216 toxic epidermal necrolysis suntan 196 pain and pain management 361 stimulus-sensitive myoclonus 265 support groups 223 spina bifida 282–283 strabismus 72, 118, 136 suppositories 367 spinal nerves 284 stratum corneum 170 surgery. See specific forms of surgery spinal stenosis 356 stratum germinativum 127 swallowing 5 spinal cord injury 217–218, strep throat 32, 155 swallowing disorders 25, 32, 283–284 streptococcal bacteria 166 55–56, 60 spinal nerves 284 streptococcal infection 155–156 sweat glands 128, 164–165, 195, dermatome 252 streptococci bacteria 59 202 herniated nucleus pulposus 326 Streptococcus 143, 180, 181t swimmer’s ear (otitis externa) 21, laminectomy 333 stress and stress management 359, 40 neural blockade 380 366, 377 Sydenham’s chorea 242 peripheral nerves 276 stress fracture 322 sympathetic nervous system 216, peripheral nervous system 276 stretch marks 200 371 rhizotomy 280 striated muscle. See skeletal muscle synapse 217 sciatica 354 stroke synaptic corridor 270 spinal cord 283 aging, neurologic changes that syndactyly 357 spinal stenosis 356 occur with 221 synovial capsule 307, 328 spinal stenosis 356–357 aphasia 225 synovial fluid 328 spinal tap. See lumbar puncture apraxia 226 synovial membrane 312, 357 spine Bell’s palsy 228 synovitis 357 ankylosing spondylitis 302–303 brain 233 synthetic skin 199 back pain 306–307 brain hemorrhage 234 syphilis 186 chiropractic 365 cognitive function and systemic infections 185 kyphosis 332 dysfunction 244 systemic lupus erythematosus (SLE) lordosis 334 nervous system 218 50, 152–153 scoliosis 354–355 papilledema 107 spiral fracture 322 stromal keratitis 103 T sports injuries 287 stump pain 382 talipes equinovarus 358 sprains and strains 301–302, 304, stupor 284–285 talus 301 333, 353, 355–356 subarachnoid brain hemorrhage tardive dyskinesia 252 squamous cell. See keratinocyte 234t taste 4, 8 squamous cell carcinoma subarachnoid space 263 taste buds 4–5 Index 413 tattoos 203 tinea pedis 204 trigeminal nerve 54, 246, 247t TBI. See traumatic brain injury tinea versicolor 204–205 trigger-point injection 385 TCA (trichloroacetic acid) 144 tinnitus 58 triglyceride blood level 211 T-cell activation 188 hearing loss 29 triptans 374, 377 T-cell lymphocyte 339 Ménière’s disease 34 trochlear nerve 246, 247t tear ducts. See lacrimal ducts ototoxicity 42t, 43 tropia. See strabismus tears 65, 85–87 ruptured eardrum 47 tryosinase 127 teeth 358 tissue expansion 163, 205 T-score 311 dental caries 20 tissue flap 163 tumor, cancerous 114, 235–237, functions of the mouth 4 tissue graft 163 269 musculoskeletal system 294 toenails 129, 167 tumor, noncancerous (benign) oral hygiene 39 toes 145–146, 350, 357 acoustic neuroma 7 periodontal disease 44 tongue 25, 26, 57 angioma 138 toothache 57 tonometry 93, 97, 104, 119 brain tumor 235–237 teething 49 tonsillitis 6, 58–59 dermatofibroma 152 telangiectasis 203 tonsils 44, 57–59 granuloma telangiectaticum 161 telencephalon 230–231 toothache 20, 57 lipoma 333–334 temporal bone 359 topical analgesics 366–367 neurofibromatosis 269 temporal lobe 231t, 242, 260 torticollis 360 papilloma 180 temporomandibular disorders 359 Tourette’s syndrome 287 rhabdomyoma 353 tendon 359 toxic alopecia 137 seborrheic keratosis 195 epicondylitis 320–321 toxic epidermal necrolysis 205 tunnel vision 93 muscle 336 toxic optic neuropathy 119–120, tympanic membrane 59. See also musculoskeletal system 294 119t ruptured eardrum rotator cuff impingement toxic shock syndrome 47 barotrauma 11 syndrome 353 toxoplasmosis 238 cholesteatoma 15 sprains and strains 355 trabecular bone 308 ear 20 tendonitis 359–360 trabeculoplasty 94 functions of the ear 3 tendonitis 297, 320–321, 352, 353, trabeculotomy 94 myringitis 35 359–360 trachea 5, 182 myringotomy 35 tennis elbow 320 tracheoesophageal speech 23 tympanoplasty 59 TENS. See transcutaneous electrical transcervical electrolarynx 21 tympanic reflex 36 nerve stimulation transcutaneous electrical nerve tympanoplasty 11, 48, 59 tension headache 373, 376t stimulation (TENS) 381, 384–385 type 1 collagen 342 terminal pain 384 transdermal patch 366, 378 type 1 complex regional pain testosterone 131, 310 transplant-related Kaposi’s sarcoma syndrome 371, 372 tetracycline 183 168, 169 type 2 complex regional pain thalamotomy 241, 286 traumatic brain injury (TBI) syndrome 371, 372 thalamus 232, 286, 361 287–288 tyramines 377 therapeutic level 367 apraxia 226 theta waves 253 cognitive function and U throat 57 dysfunction 244 ultraviolet A (UVA) light 200 eustachian tube 23 concussion 244–245 ultraviolet B (UVB) light 200, 201 obstructive sleep apnea 39 dementia 251 ultraviolet B (UVB) phototherapy peritonsillar abscess 44 papilledema 107 184 postnasal drip 45 paralysis 275 ultraviolet light 175, 196, 315 swallowing disorders 55–56 tremor disorders 288–289 ultraviolet-protection factor (UPF) thrush 57–58 athetosis 227 rating 201 thymus 339 deep brain stimulation 250 umbilical hernia 325 tibia 301, 330, 341 dyskinesia 252 unconsciousness 245, 277, tic 75, 286, 287, 320 myoclonus 265–266 284–285, 289 tinea 179, 204, 204t pallidotomy 274 understanding pain 386 tinea barbae 204 Parkinson’s disease 275–276 UPF (ultraviolet-protection factor) tinea capitis 204 tretinoin (Retin-A) 145 rating 201 tinea corporis 204 trichloroacetic acid (TCA) 144 upper respiratory tract 19 tinea cruris 204 tricyclic antidepressant 268 urethritis 352 414 Index uric acid 323–324 Viagra. See sildenafil vocal tic 287 urination 216 violence 283 voice therapy 13, 63, 64 urticaria 183, 205–206 viral infection. See specific infections Volksmann’s contracture 319 US Food and Drug Administration viral labyrinthitis 31 vomiting 374 (FDA) virus. See specific viruses vulva 32 Alzheimer’s disease 222 visceral motor nerves 246, 247t botulinum therapy 141 vision health 121–122, 122t W keratoconus 99 vision impairment 122–123, 122t Waardenburg’s syndrome 136 meninges 263 albinism 135 warmup 302, 332, 356 myopia 101 amblyopia 72–73 wart 180, 209 Parkinson’s disease 276 ARMD 70–71 weak ankles 302 US National Institutes of Health braille 75–76 weight and pain 389 (NIH) 141, 365 color deficiency 80 weight loss and weight US Occupational Safety and Health corrective lenses 82–84 management 265 Administration (OSHA) 30, 37 diplopia 86 wet (neovascular) ARMD 70 utricle 11 entropion 87 wheal 205–206, 209–210 uveitis 97, 120 exophthalmos 88 white matter 216, 283 uvula 5, 16 eyes 67 whitlow 210 intraocular pressure 97 WHO (World Health Organization) V ischemic optic neuropathy 98 344 vaccination (poliomyelitis) 277, 278 keratoconus 99 withdrawal reflex 381, 382 vaccinia virus 150 myopia 101 women’s health vagus nerve 53, 246 nystagmus 102 episcleritis 88 variable pain response 388 optic nerve hypoplasia 106 fibromyalgia 321, 322 variant CJD (vCJD) 248 refractive errors 111 migraine headache 374 varicella zoster 103, 269 retinitis pigmentosa 114 osteoporosis 346 vascular birthmark 139 scleritis 117 pain and pain management 362 vascular dementia 251 visual acuity 121 Wong-Baker Faces Scale 364, 390 vascular headache 373–374 Vistaril (hydroxyzine) 206 World Health Organization (WHO) vasculitis 117 visual acuity 80, 104, 121 344 velopharyngeal insufficiency 60 visual cortex 105 wound care 141 velopharyngeal sphincter 60 visual field 102, 104, 121, 121t wrinkles 134–135, 141, 158, 191, ventral spinal nerve root 284 visual health (ophthalmic 210–211 venules 127 examination) 103–104 wrist drop 319 verbal apraxia 225–226 vitamin A 102 wryneck. See torticollis vernix 125 vitamin B 16, 142 vertebrae 302–303, 316–317, vitamin B12 119, 269, 275 X 326–327, 333 vitamin D 128, 315, 343, 345–346 xanthelasma 124, 211 vertebral channel 356–357 vitamins and health 315, 343 xanthoma 211 vertigo 60–61 vitiligo 127, 176, 207–208 xenograft 199 barotrauma 11 vitrectomy 123–124 X-rays 13, 295 BPPV 11, 12 vitreous detachment 67, 124 cholesteatoma 15 vitreous humor 67, 91, 113, Y labyrinthitis 31 123–124 YAG (yttrium-aluminum-garnet) Ménière’s disease 34 vocal cord cyst 62 laser surgery 79 ototoxicity 43 vocal cord nodule 63 yeast infection 57–58, 152 vestibular neruonitis 61, 62 vocal cord paralysis 63 yoga 332, 375 Vesalius, Andreas 218 vocal cord polyp 63 yttrium-aluminum-garnet (YAG) vesicle 207, 210 vocal cords 63–64 laser surgery 79 vestibular dysfunction 20, 31, 60–62 Bogart-Bacall syndrome 13 vestibular neuronitis 61–62 functions of the throat 5 Z vestibulocochlear nerve 17, 246, sneeze 54 zeaxanthin 102 247t tremor disorders 288–289 Z-score 311