Medical Foundations of Workers’ Compensation

Objective: This section will introduce the student to the topic of hearing loss, the types, causes, and symptoms of hearing loss, and how to test for it. Hearing Loss Overview Anatomy Types of Hearing Loss Causes of Hearing Loss Symptoms Exams and Tests Preventing Hearing Loss Treating Hearing Loss

Hearing Loss Definitions General Definitions Testing Terminology (Age related hearing loss) Sensorineural Hearing Loss

Links to Review Diagram Ear Diagram Quiz (Test Yourself)

1 Medical Foundations of Workers’ Compensation Hearing Loss

Hearing Loss Overview Hearing loss is a common problem that affects people of all ages. It is especially common in older adults: Among those between the ages of 65 and 75, 30% to 35% have reduced hearing. Hearing loss may be mild or severe, temporary or permanent, depending on the cause. In adults, -induced hearing loss and age-related hearing loss are the most common types of hearing loss.

Whatever the cause, detection and treatment of hearing loss are important. Undiagnosed and untreated hearing loss can contribute to depression, social isolation, and loss of independence, especially in older adults. It can impact a person's personal safety and his or her productivity in the workplace and at home.

Evaluation of a hearing loss is also important because hearing loss is sometimes reversible. Even if a hearing loss can't be reversed, hearing aids and other devices can help the person get the most out of any remaining hearing and make communication, social interaction, and work and leisure activities easier and more enjoyable.

Anatomy There are four major sections of the ear:  Nerves (consists of 30,000 fibers) take information to the brain.  Inner Ear () receptors for hearing and balance. Contains chambers, each of which are broken down into 3 more chambers. Each of the 3 chambers has their own job.  (transformer). Three bones serve the transformer function – malleus (hammer), incus (anvil) and stapes (stirrup). The stapes (stirrup) moves by vibratory action.  External ear (only seen in mammals). It serves as a scoop and as a place to hang earrings.

The sections all play important roles in how we hear. A problem with any of them can cause a hearing loss.

Types of Hearing Loss There are three basic types of hearing loss:

 A conductive hearing loss occurs when the normal physical movement (conduction) of sound waves through the external or the middle ear is blocked or misdirected. Anything that disrupts the passage of sound through the external and middle ear—such as hardened , a foreign object, abnormal bone growth, swelling, or a tumor—can cause this type of hearing loss. Conductive hearing loss usually can be reversed by treating the underlying cause.  A sensorineural hearing loss occurs when sound reaches the inner ear normally

2 but a problem in the inner ear, the cochlear (auditory) nerve, or, rarely, the brain itself prevents proper hearing. Damage to the tiny hair cells in the cochlea, resulting from age-related changes or repeated noise exposure, is the most common cause of sensorineural hearing loss. Conditions such as stroke, , or a tumor also may result in a sensorineural hearing loss by causing nerve damage. Sensorineural hearing loss often cannot be reversed.  A mixed hearing loss, in which both the conductive and sensorineural systems are affected, can also occur.

Causes of Hearing Loss Hearing loss can have many possible causes. In adults, the most common causes of hearing loss are:  Noise. Noise-induced hearing loss can affect people of all ages and most often develops gradually over many years. In most cases, damage to the inner ear caused by exposure to harmful noise results in a permanent sensorineural hearing loss. Though extremely common, noise-induced hearing loss is almost always preventable.  Age. In age-related hearing loss, or presbycusis, changes in the nerve tissue and cells of the inner ear that occur as a person grows older, cause a gradual but steady sensorineural hearing loss. The loss may be mild or severe, but it is always permanent.

Other causes of hearing loss include:  Earwax or an object in the ear. Earwax is an especially common and easily treatable cause of temporary hearing loss.  Ototoxic medications and other substances (such as aspirin, , , tin, , and manganese) that can damage the ear.  Injury to the ear. Head injuries can also damage the structures in the ear and cause a sudden hearing loss.  Ear infection.  (a condition affecting the bones of the middle ear).  Acoustic neuroma (a benign tumor on the cochlear, or auditory, nerve).  Ménière's disease (a disorder of the inner ear that can affect hearing and balance. It is characterized by episodes of dizziness and tinnitus and progressive hearing loss, usually in one ear. It is caused by an increase in volume and pressure of the endolymph of the inner ear).

Symptoms People who have a hearing loss are sometimes not aware of it, especially when the loss has developed gradually. Family members or friends often notice signs that the person is having trouble hearing before the person realizes it.

Symptoms of hearing loss include:  Muffled hearing.  Not being able to understand what is being said, especially when there are competing voices or background noise. (Being able to hear someone speaking, but

3 not able to distinguish the specific words.)  Listening to the television or radio at higher volume than in the past.  Avoiding conversation and social interaction. Social situations can be tiring and stressful for a person who does not hear well. Some people may increasingly avoid those situations as hearing becomes more difficult. This may also contribute to (or be mistaken for) depression, especially when it occurs in older people.

Other symptoms that may occur with hearing loss include:  Ringing, roaring, hissing, or buzzing in the ear (tinnitus).  .  Pus or fluid discharge from the ear. This may result from an injury or infection that is causing hearing loss.  The feeling that you or your surroundings are spinning or whirling when neither you nor the surroundings are actually moving (). This may occur with Ménière's disease, acoustic neuroma, or certain other conditions.

Sudden hearing loss may be a medical emergency, especially when it follows a head or ear injury.

Exams and Tests Hearing loss can often be detected during a routine visit to a health professional. If a patient reports symptoms of hearing loss or the doctor detects a possible hearing problem, he or she may ask the patient about recent or long-term exposure to loud noise, any medications being taken (some may be ototoxic, meaning they have a deleterious effect upon the eighth nerve or on the organs of hearing and balance), physical symptoms (such as muffled hearing, ringing in the , or vertigo), and other factors. The patient’s answers to these questions may sometimes suggest the cause of the hearing loss.

Evaluation of a possible hearing problem also includes a physical examination of the ears, during which the doctor looks inside each ear using a lighted instrument called an . A physical exam of the ear can detect problems in the ear canal, , and middle ear, such as hardened earwax, an object or obstruction in the ear canal, infection or fluid in the ear, injury to the eardrum, and other problems that may contribute to hearing loss. The inner ear cannot be viewed through an otoscope.

If a patient’s symptoms, exam, or history suggests a hearing problem may be present, the doctor may do one or two simple tests to screen for hearing loss. These may include the “whisper” test as well as tuning fork tests.  Whisper test: a simple screening test that assesses a person’s ability to hear whispered speech across a short distance.  Tuning fork test: the examiner strikes a two-pronged metal device (tuning fork) to produce a tone. The base of the tuning fork may then be placed on the patient’s forehead or the bone behind the ear or may be moved around in the area near the ear. These quick, easy tests can provide valuable information about the type of hearing loss that may be present.

4 If the initial screening tests suggest or reveal a hearing loss, a more thorough hearing evaluation may be needed to assess whether there is a hearing loss, how severe the loss is, and what part of the ear is affected. A standard hearing evaluation includes the following tests:  Pure tone audiometry: an audiometer is used to produce tones that the patient listens for through earphones (air conduction) and via a bone conduction oscillator (bone conduction). Comparisons are made of the air and bone conduction thresholds to determine the nature of the hearing loss (conductive, sensorineural, or mixed).  Speech reception and word recognition tests: measure the patient’s ability to hear and understand speech.  Acoustic immitance tests ( and acoustic reflex tests): measure the amount of sound energy that is reflected back from the eardrum (tympanic membrane) and the bones of the middle ear instead of being conducted on to the inner ear. These tests help evaluate the function of the middle ear.

Depending on the suspected cause of hearing loss, other tests may also be done.  Imaging tests: such as computed tomography (CT) or magnetic resonance imaging (MRI) scanning might be done when an injury or tumor is suspected as the cause of the hearing loss.  Auditory brainstem evoked potential testing: may be used to evaluate the function of certain nerve pathways in the brain if acoustic neuroma or another nerve problem is suspected as the cause of hearing loss. An evoked potential is an electrical response in a nerve to a stimulus; the brain's response to a sound stimulus is the auditory brainstem evoked response. The response is recorded using electrodes taped to the head.

Preventing Hearing Loss Repeated exposure to loud noise is one of the most common causes of permanent hearing loss. For the most part, it is preventable.

There are many steps people can take to lower their risk of noise-induced hearing loss:  Pay attention to noise. Know what kinds of situations can generate harmful noise levels, and avoid these situations whenever possible. People can be exposed to harmful noise at work, at home, and in many other settings. For information about legal noise limits and hearing protection requirements in workplaces in the United States, contact the Occupational Safety and Health Administration (OSHA).  Use hearing protection. Wear hearing protectors, such as earplugs or earmuffs when exposed to potentially harmful noise. (Cotton balls or tissues stuffed in the ears do not offer much protection.) When used correctly, these types of protection can significantly reduce the level of sound that reaches the ear. Even lawn mowers, power tools, and some basic household appliances can cause hearing loss if hearing protectors are not worn.

5  Minimize total daily noise exposure. Noise exposure and the damage it can cause are cumulative. The potential for damage to a person’s hearing increases with the total amount of time spent exposed to noise. Those exposed to high noise levels on a regular basis at work should try to avoid noisy situations in their leisure time.  Control the volume when possible. Don't buy noisy toys, appliances, or tools when there are quieter alternatives. Reduce the noise by turning down the volume on the stereo, television, or car radio.

A person should not wait until he or she notices a hearing loss to start using noise protection. Noise-induced hearing loss tends to develop slowly and without pain or other symptoms, and many people may not notice that they have a hearing loss until it is severe.

Once noise-related damage to the ear is confirmed, it cannot be reversed. However, further damage can be prevented.

There are many steps employers can take to help prevent hearing loss, including but not limited to:  Conduct yearly noise surveys in all areas of a plant known to have any noise level greater than 80 db by a certified industrial hygienist. Include pulse noise levels.  Maintain accurate records of where employees are working at all times.

 Ensure workers with exposure levels greater than 85 dB are tested yearly by certified personnel and follow the regulations regarding what to do when threshold shifts change. Ensure noise exposure histories are completed and signed yearly by each employee.  Ensure workers wear hearing protection properly and document what protection each worker uses, as well as what attempts were taken to ensure the worker uses it properly.  Enforce attending hearing conservation safety classes for all employees who work in high noise areas that teaches the importance of wearing protection at work and at home.  Use engineering designs to muffle or bar noise whenever possible.  Keep accurate records of all the above  Understand that confirming noise-related damage requires multiple steps and follow them closely in any worker thought to have experienced a threshold hearing shift.

To lower the risk of injury-related, medication-related (ototoxic), and other types of hearing loss, people should:  Never stick a cotton swab, hairpin, or other object in the ear to remove earwax or to scratch. In general, the best way to prevent earwax problems is to leave earwax alone.

6  Ask a pharmacist or doctor whether prescribed medications can have hearing- related side effects (). Report any new hearing problem noticed while taking medication to a physician.  Always blow their nose gently and through both nostrils.  Swallow and yawn frequently during a plane’s decent when flying. Those with an upper respiratory problem, such as a cold, the flu, or a sinus infection, should take a decongestant a few hours before the plane is scheduled to land.  Learn and practice proper underwater descent techniques when scuba diving.  Always wear a seatbelt in the car, and wear a helmet when biking, skiing, or rollerblading. These habits can lower the risk of head and ear injury.  Stop smoking. Some studies have found that adults who smoke are more likely to develop hearing loss than nonsmokers, although other studies have not been able to show this association.

Treating Hearing Loss Treatment for hearing loss depends on what caused the hearing loss and whether the loss can be reversed. When dealing with temporary, reversible hearing loss, the specific treatment usually depends on the cause of the hearing loss.  Hearing loss related to ototoxic medications often improves once the person stops taking the medication.  When hearing loss is caused by impacted earwax, removing the wax usually restores normal hearing. Do not use a cotton swab or a sharp object to try to remove the wax, since this may push the wax even further into the ear or may cause injury.  Ear infections often clear up without treatment but some may require antibiotics.  An injury to the ear may heal without treatment or may need to be repaired surgically.  Surgery or medication may be needed to treat conditions such as otosclerosis, acoustic neuroma, or Ménière's disease.

When a worker is found to have hearing loss that is permanent and cannot be reversed, refer the employer to WISHA standards in correcting any work-related cause and stopping the possibility of any further damage to this worker.

When hearing loss is permanent and cannot be reversed, hearing devices can often improve a person's ability to hear and communicate. These devices include:  Hearing aids. Although they do not restore normal hearing, hearing aids can benefit people with noise-induced hearing loss or age-related hearing loss (presbycusis).  Cochlear implants. Cochlear implants may sometimes be used in people with severe or total permanent hearing loss who get little benefit from hearing aids.

Assistive listening devices, alerting devices, and other communication aids can also be helpful.

Although older people or their families may view hearing loss as a normal part of aging, diagnosis and treatment are very important. Hearing loss may contribute to loneliness, depression, and loss of independence for many older adults. Treatment cannot restore

7 lost hearing, but it can make communication, social interaction, and work and leisure activities easier and more enjoyable.

Hearing Loss Definitions General Definitions Binaural – pertaining to both ears

Decibel (db) – unit of measure relating to the intensity or loudness of a sound equal to one-tenth of a bel; one decibel equals approximately the smallest difference in acoustic power the human ear can detect. Every increase of 10 decibels (10 dB) sounds twice as loud

Hertz (Hz) – unit of measurement of frequency or pitch of a sound – the rate at which sound occurs

Monaural – pertaining to one ear

Testing Terminology Audiometry – The measurement of the acuity (clarity or clearness) of hearing for the various frequencies of sound waves. Documentation of no loud noise exposure for the 12 hours preceding the test is important. Audiometric tests should be performed by a licensed or certified audiologist, otolarygologist, or other qualified physician, or by a technician responsible to one of the above. In the state of Washington, the tester must be an audiometric technician certified by the Council for Accreditation in Occupational Hearing Conservation CAOHC.

Air Conduction Test – Audiometric measurements made under air-conduction earphones that check the hearing sensitivity of the entire .

Symbols used on the audiogram are: 0 Right ear unmasked X Left ear unmasked Right ear masked Left ear masked

The colors of the symbols are: Red Right ear Blue Left ear

Bone Conduction Test – Audiometric measurement made with a bone conduction oscillator/vibrator that theoretically checks the hearing sensitivity of the inner ear and auditory structures medial to the inner ear. A masking sound may be introduced into the ear not being tested to ensure the response of the appropriate ear.

8 Symbols used on the audiogram are: < Right ear unmasked [ Right ear masked > Left ear unmasked ] Left ear masked

The colors of the symbols are: Red Right ear Blue Left ear

Audiogram – A graphic representation of audiometric findings showing hearing levels as a function of frequency.

Audiometric results may be presented in different formats: a) Graph format (audiogram) in which the frequencies/pitches tested are indicated at the top of the graph from low pitch @ 500 Hz to high pitch @ 8000 Hz. Intensity/loudness level of the sound is indicated on the left side of the graph from very soft at the top at 0 dB to very loud at the bottom at 120 dB. The circles in red, representing thresholds for the right ear, and the blue X’s, representing thresholds for the left ear, are then plotted on this graph. b) Numerical format in which results are indicated by numerical values (e.g. 10, 20, 30 etc.). Test frequencies are listed for each ear with corresponding threshold values rather than plotting on graph. Serial are listings of audiometric test results for a number of different hearing tests in a single chart.

Audiogram range of hearing: 0-25 dB Normal hearing 30-40 dB Mild hearing loss 45-55 dB Moderate hearing loss 60-70 dB Moderately-severe hearing loss 75-90 dB Severe hearing loss 95+ dB Profound hearing loss

Proof of daily calibration and annual outside calibration should be readily available on request. Without such calibration, the test was not conducted per Council for Accreditation in Occupational Hearing Conservation (CAOHC).

Conductive Hearing Loss is a breakdown or obstruction in the transmission system.  Not caused by continuous excessive noise exposure.  May be caused by blocking the external ear canal with ear wax or a foreign body, a broken ear drum or head trauma.  Most cases can be reversed and hearing restored or stabilized by appropriate treatment.  A conductive hearing loss will appear normal on a bone conduction audiogram and therefore can be isolated from a sensory hearing loss.

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Sensorineural Hearing Loss results from changes in the inner ear or in the nerves carrying impulses to the brain.  Can be caused by noise exposure.  Must be tested more than once to prove any loss and cause.  Is permanent, and not treatable by medical or surgical means.  Sensorineural loss due to loud noise exposure is usually preventable with properly fit hearing protection devices, which provide adequate protection and are used consistently  Depending on the degree of hearing loss, hearing aid(s) may be beneficial

Tinnitus is a perception of sound in the absence of an acoustic stimulus.  May be a buzzing, ringing, roaring, whistling or hissing or may involve more complex sounds that vary over time.  May occur as a symptom of nearly all ear disorders, including obstruction of the ear canal, noise induced hearing loss, sensorineural hearing loss, and head trauma.  An associated hearing loss oftentimes is present.  There is no specific medical or surgical therapy.  Some patients benefit for the use on a tinnitus masker.  May be related to conditions/factors other than ear related problems (e.g. some medications).

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