Belavadi & Prashanth: Clinical Importance of Cranial Nerves

Review Article International Ayurvedic Medical Journal ISSN:2320 5091

CLINICAL IMPORTANCE OF CRANIAL NERVES Belavadi S. N. Prashanth A. S. Dept. of Kayachikitsa, Ayurveda Mahavidyalaya Hubli, Karnataka, India

ABSTRACT There are 12 pairs of Cranial nerves in the body having major importance in clinical practice among these Nerves some are Sensory, Some are Motor and some are both. It most important and necessary in every Neurological patient to examine these affected or involved nerves to find out its lesion and this helps to diagnose and plan the treatment in various neurological disorders. In this present article the clinical importance of tweleve pairs of cranial nerves, Location, Examination, Functions and Applied aspects of each Cranial nerve has been discussed. Keywords: Cranial Nerves, Motor function, Sensory, Facial nerve, Motor and Sensory Pathway

INTRODUCTION motor neurons lie in nuclei within the Cranial- of or relating to the cranium brain.(3) which encloses the brain; Nerves - Any The 12 pairs of Cranial nerves supply bundle of nerve fibers running to various muscles of Eyeball, Face, Palate, Pharynx, organs and tissues of the body. Cranial Larynx, Tongue and two large muscles of Nerves: Means any of the 12 paired nerves Neck. Besides these are afferent loop to that originate in the Brain stem.(1) special senses like Smell, Sight, Hearing, The systemic examination of Cranial Taste and Touch.(4) nerve is an important part of the Cranial nerves are involved in head and examination of every neurological patient. It neck function, and processes such as eating, may reveal a lesion of a Cranial nerve speech and facial expression. These arise nucleus or its central connections, or it may from the brain as twelve pairs. They pass show an interruption of the lower motor through or into the cranial bones (thus neurons.(2) cranial nerves) and are numbered I to XII Cranial nerve like spinal nerve is a roughly in order from top (rostral) to bottom part of the peripheral nervous system. 12 (caudal). Their functions are those of the pairs of Cranial nerve 10 originate from the head, some are concerned with awareness brain stem but all passes through foramina of, and communication with, the of the skull. environment; and some are concerned with Some Cranial nerve contain only sensory sustenance, the gut tube and movements fibers and thus are called sensory and motor associated with it.(5) fibers and are referred to mixed nerves. The Meaning of 12 cranial nerves: With cell bodies of sensory neurons are found Mnemonic means Of or relating to or outside the brain, whereas the cell bodies of involved the practice of aiding the memory. Belavadi & Prashanth: Clinical Importance of Cranial Nerves Mnemonics- A method or system for Vestibulocochlear nerve (victory): improving the memory.(6) Vestibulum- vestibule, Kokhlos and snail Olfactory nerve (oh): Olfacere- to smell, Primirily Sensory. this is Sensory. Glossopharangeal (Give): Glossa- tongue, Optic nerve (oh): Optikos- Vision, Eye or Pharynx-Throat this is both Motor and Optics this is Sensory. Sensory. Occulomotor nerve (oh): Oculus-eye, Vagus nerve (value): Vagus- Vagrant or motor- mover, this both Motor and sensory. wondering both Motor and Sensory. Troclear nerve (try): Trokholear- pulley, Accessory nerve (and): Accessorius- this is both Motor and sensory. Primarily assisting this is both Motor and sensory. Motor. Primarily Motor. Abducent nerve (again): Ab- away, duces- Hypoglossal nerve (Happiness): Hypo- to lead both Motor and sensory. Primarily below, glossa-tongue. (7) Motor. Cranial Nerves: There are totally 12 pairs Trigeminal nerve (try):: Tri-three, of cranial nerves explained in all modern geminus-twin, trigeminus- three fold for its texts. branches this is both Motor and Sensory. Facial nerve (failure):: Facies- face this is both Motor and Sensory.

Table 1: showing cranial nerve location, examination, functions and applied aspects (8), (9), (10) Name Location Examination Functions Applied Olfactory nerve Arises in olfactory mucosa -determine the nasal passages are For smell -unilateral anosmia passes olfactory foramina in clear. -bilateral anosmia the cribriorm plate of -apply some easily recognizable -complete anosmia ethomoid bones and ends in aromatic substance. Ex: oil of Allergic rhinitis cause olfactory bulb. peppermint, oil of cloves, temporary -ask the patient to identify the olfactoryimpairment smell. Optic nerve Arises in the retina of eye -ask the patient whether any Vision Fracture in the orbit, passes through optic foramen change in the eye sight. Visual lesion of vision pathway from optic chaisma acuity should be tested for near Disease cns may results & distant vision by snell`s type vision field loss of -visual fields should be tested by vision activity. closing right eye by looking into Damage- blindness, the examiners right eye. optic neuritis -examination of fundi- by opthalmoscope patient is asked to look distinct objects. - optic disc- creamy pink, retina- pinkish red, blood vessels - macula is examined by asking the patient look directly at the light of the opthalmoscope Oculomotor Motor portion- originates in - this supplies all the extra ocular Mototrfunction- The patient see double midebrain, passes through muscles except superior oblique movements of eyelid and vision(diplopia) orbital fissure and distributed and lateral rectus. eyeball occulomotor of Ptosis, to levator palpebrae superioris -in a complete lesion lense for near vision. Lteral squint of upper eyelid and extrinsic occulomotor nerve eye cannot be Sensoryfunction – eyeball muscle superior moved upward, downward or muscles strabismus patois inferior mideal rectus and inward. pupil dilatation, diplopic. mideal oblique. Sensory parts- consists of the fibers from proprioceptors in eyeball muscles passes through supernal orbital fissure and terminate in Belavadi & Prashanth: Clinical Importance of Cranial Nerves midebrain. Trochlear Motor portion- originate from Supplies superior oblique Motor function- Double vision, midbrain passes through muscles which rotates the eye movements of eye ball. cavernous sinus superior orbital fissure and downward and laterally. Sensory function- in thrombosis, aneurysm distributed to superior truckler nerve paralysis of the internal carotid oblique, muscle, an extinct diplopic and strabismus. artery. eyeball muscle . Sensory portion- consists of fibers of proprioceptors in superior oblique muscle that parts through superior orbital in mide brain. Fissure and terminate in midbrain. Trigeminal This has both motor & Supplies the lateral rectus Motor function-chewing Injury results paralysis sensory roots, passes through muscle which rotates the eye Sensory function- of muscles of trigeminal ganglion and laterally in this lesion patient Convey sensation of mastication and loss of emerge the opthalmc, cannot turn the eye laterally. touch pain temperature. sensation of touch. maxillary and mandbular. The sensory function may be tested by using cotton, a pin over each area of the face. Abducens Motor portion- originate in Motor function- With damage attached pons passes through superior, movements of eyeball eyeball cannot move. orbital fissure, distributed to Sensory function- muscle lateral rectus muscles sense Sensory portion- consists of fibers from proprioceptors in lateral rectus muscles pass through fissers, end inpons. Auditory/ Cochlear branch- arise in This nerve innervates the utricle Cochlear branches Injury causes vertigo, vestibulocochlear spinal organ from spinal and saccule which are sensitive function– convey ataxia, and nystagmus, nerve ganglion passes through the a to static changes in equilibrium. impulsesassociated with Deafness, tinnitus auditory meat’s and ends in hearing. thalamus. Vestibularbranches Vestibular branches- arise in function – semicircular canals succulent conveyimpulsesassociated utricle and forms end in pons with equilibrium. and cerebellum. Glossopharangeal Motor portion- originated in This supplies the Motor function Injury leads to difficulty medulla passes through stylopharyngeus muscle. Sensory Secretion of saliva in swallowing. jugular foramen and fibres innervate the posterior Sensoryfunction Reduced secretion of distributed to stylopharyngens 1/3rd of the tongue for general Taste, regulation of blood saliva, loss of sensation muscles sensation of taste. pressure and muscle. in the throat and loss of Sensory portion-aries from Isolated lesion of this nerve are taste. taste buds on posterior 1/3rd rare and usually involve the Glossopharangeal or tongue & from carotid vagus nerve. neuralgia sinus, passes through jugular foramen, ends in medulla. Contains fibers from somatic sensory receptors on posterior 1/3rd of tongue and proreceiptors in swallowing muscles supplied by motor portion. Vagus Motor portion- originated in -this innervates many important Motor function- Severing of both nerve medulla passes through organs but examination depends Smooth muscles in the upper body jugular foramen and upon testing the branches of contrition & relaxation interferes with terminates in muscles function of pharynx, soft palate, secretion of diagnosis swallowing paralyses, airways, lungs esophagus, and larynx. fluids. vocal cords and heart, stomach, small intestine -the pharyngeal or gag reflex Sensory function- interrupts sensation and gall bladder, may be tested by touching the sensation from visceral from many organs. parasympathetic innervate lateral wall of the pharynx with a organs supplies, muscle, involuntary muscle. spatula. sense. Sensory portion-aries from -the movement of the vocal cord essentially same structures may be tested by means of supplied by motor fibers laryngoscopic examination. passes through jugular foramen and ends in medulla and pons. Accessory Motor portion – consists of This supplies the sternocleido Cranial portion mediates If nerve damaged cranial portion and spinal mastoid and the trapezius muscle swallowing movements, The sternocledo mastoid 113 www.iamj.in IAMJ: Volume 2; Issue 1; Jan-Feb 2014 Belavadi & Prashanth: Clinical Importance of Cranial Nerves portion. Cranial portion by means of spilnal root spinal portion; spinal trapeziums muscles originated from medulla, portion mediates become paralyzed passes through jugular movements of head. resulting inability to foramen and supplies Sensoryfunction – raise the shoulders and voluntary muscles of pharynx Muscle sense difficulty in turning the and soft palate. head. Spinal portion_ originates from interior gray horn of 1st five cranial segments of spinal cord passes through jugular foramen & supplies sternocleidomastoid And trapeziums muscles. Sensory portion – consists of fibers from proprioceptors in muscles supplied by motor portion and passes through jugular foramen. Hypoglossal Motor portion – originates in This supplies the intrensic Motor function- Vascular accident`s medulla passes through muscles of the tongue and the Sensory function injury of the nerve in hypoglossal canal and styloglossus, hyoglosus and Muscles sense the neck may also supplies muscles of tongue. genioglossus muscles. movements of tongue follow stab and gun Sensory portion – consists of during speech and shot wounds. Paralysis fibers from proprioceptors in swallowing. of tongue tongue muscle that passes through hypoglossal canal and end in medulla. FIG 1: SHOWING CRANIAL NERVES DISTRIBUTION (11)

FACIAL NERVE: The facial nerve motor nucleus lies The facial nerve has two roots. in the ventrolateral tegmentum of the Pons. 1. The larger contains the motor nerve fibers The efferent’s fibers arising from the which supply the ipsilateral facial muscles. nucleus sweep dorsomedially to the flour of 2. The smaller root the intermediate nerve fourth ventricle loop sharply around the contains fibers covering taste sensation from sixth nerve nucleus and then pass the anterior two thirds of the tongue ventrolaterally to emerge from the lateral cutaneous sensory fibers from the posterior border of the candle Pons at the part of the ear and preganglionic cerebellopontine angle. parasympathetic fibers that innervate the After exiting from the Pons the facial lacrimal and submandibular and sublingual nerve is medial to the 8th nerve and between salivary glands. the two lies the intermediate nerve. These 3 MOTOR PATHAWAY: nerve passes through the internal auditory, meatus and than the facial nerve and 114 www.iamj.in IAMJ: Volume 2; Issue 1; Jan-Feb 2014 Belavadi & Prashanth: Clinical Importance of Cranial Nerves intermideate nerve inter the facial canal. In AUTONOMIC PATHWAY: Autonomic the facial canal on the middle site of the pathway facial nerve divide into two groups. middle ear the facial nerve turns sharply as 1. One groups passes with grater superficial the Genu of the facial nerve moving petrosal nerve to the pterygopalatine posterioly and inferiorly fives off a branch ganglion. Post ganglion fibers innervate the to the stapedins muscles and exits from the lachrymal glands and mucous membrane of skull through the stylomastoid foramen. the nose and mouth. CARTIO BULBAR PATHWAY: 2. The other groups of fibers travel in the The facial uncles is composted of a chordatympani and terminate in the number of distinct cell groups, each submandibular ganglion. Post ganglion innervating specific facial muscles. Those fibers innervate the submandibular and supplying the upper facial muscles receives sublingual salivation glands. bilateral supranuclear innervations, where as EXAMINATION POINTS those supplying the lower facial muscles It supplies the muscles of the facial receives mainly crossed fibers from the expression, supplies the anterior two-third of contra lateral hemisphere. the tongue. SENSORY PATHWAY: To test facial nerve- patient is asked to show In the facial canal there is an expansion of teeth by separating the lips with teeth the facial nerve as it makes its sharp clenched. backwards turn at the genu. The expansion If lesions of facial nerve is present on one is the geniculate ganglion and is formed by side , the mouth is distorted. the cell bodies of the nerve that gives rise to Another test usual will be ask the patient to two sensory components of facial nerve. close eyes firmly. SPECIAL VISCERAL: On the side of the lesion, the orbcularis special visceral AlterNet fibers convey taste occuli is paralyzed so that the eye lid on that sensation for the anterior two-thirds of the side is easily raised by the raising patient`s tongue. From the tongue this fibers travels upper lid by the physician. first from the inguinal nerve than the chord FACIAL NERVE REFLEXES: tympani which enters the skull crosses  In the clinical practice the corneal tympanic cavity and joined the facial nerve reflexes and to a lesser extent the glabellar in the facial canal. tap reflexes are of value. The glabellar tap SOMATIC ALTERNET NERVE: reflexes is polysynaptic and elicited by Somatic Alternet nerve fibers arise from a taping the forehead over the bridges of the small area of skin which included the nose and observing contraction of orbicular posterior part of the external auditory is ocuti as blinking bilaterally. After several meatus and the skin behind the ear and in taps there is habituation and blinking stops. fronts of the mastoid. They enter the facial  Other reflexes include canal just proximal to the stylomastiod  the naso lacrimal reflex of tearing in foramen from the cell bodies in the response to stimulation of the nasal mucosa, geniculation ganglion the fibers pass centrally in the intermediate nerve and terminate in the spinal trigeminal tract. 115 www.iamj.in IAMJ: Volume 2; Issue 1; Jan-Feb 2014 Belavadi & Prashanth: Clinical Importance of Cranial Nerves  the naso mental reflex which on the stampedes reflex, altered taste sensation a tapping the side of the nose, causes elevation facial nerve lesion. of the upper lip and The facial nucleus may be affected by  the stapedius reflex in which stapedius pontine lesion and the nerve by the lesions contracts in response to loud noise. in the cerebella pontine angle, within the LESION OF THE FACIAL NERVE: petro us temporal bone and outside the skull. Lesion of the facial nerve, its nucleus or PONTINE LESIONS: supranuclear pathways may produce These rarely affect the facial nucleus or  Facial muscles weakness, only peripheral nerve fibers in isolation and associated lesion affecting facial nerve itself affecting features include ipsilateral rector and taste sensation and autonomic function. conjugate gaze palsy trigeminal hemi paresis  Numbness is not an expected finding in and hemisonsary loss. Common pathology facial nerve lesion although symptomatic include Vascular lesion, Multiple sclerosis complaints of sensory disturbance are and Tumors and less common disorder being common in Bell’s palsy. brainstem Encephalitis, Syringobulbia and SUPRANUCLEAR LESIONS: Poliomyelitis.  The upper facial muscle have almost INFECTION INVOLVING THE equal bilateral cortical representation FACIAL NERVE: Ramsy hunt syndrome, whereas Lyme disease and Bilateral facial nerve- (11)  The lower facial muscles receive mainly Guillian-Barre Syndrome. crossed fibers from the contraletral CONCLUSION hemisphere thus a unilateral upper motor Now a days majority of the diseases neuron lesion causes contraletral facial belongs to Centrol Nervous System like weakness with the lower part of the face Stoke, Facila palsy in which we find the more affected than upper . involvement of Cranial nerves. Cranial  Depending upon the site of the lesion nerves better understood intrems of spontaneous emotional movements may be Uppermotor neuron and Lower motor more affected than voluntary movements neuron. Involvement of Different Crainial and vice versa. nerves impact on different sense organs of SUPRANUCLEAR AND PERIPHERAL the body like Tongue (Loss of taste), Eye LESION: (Unable to close), Nose (Loss of Smell) etc. A lesion of the nucleus or facial nerve It is better to plan taretment based on the generally causes equal weakness of all cause not based on symptoms. ipsiletral facial muscles and the clinical feature are exemplified by Bell’s palsy. Considering the origins and site of union with facial nerve of the greater superficial petrosal nerve, the nerve of stapedius and chorda tympani, the presence of impaired lacrimation hyperacusis or an impaired

116 www.iamj.in IAMJ: Volume 2; Issue 1; Jan-Feb 2014 Belavadi & Prashanth: Clinical Importance of Cranial Nerves FIG- 2 SHOWING FACIAL NERVES DISTRIBUTION 12

FIG- 3 SHOWING FACIAL NERVES DISTRIBUTION.13

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117 www.iamj.in IAMJ: Volume 2; Issue 1; Jan-Feb 2014 Belavadi & Prashanth: Clinical Importance of Cranial Nerves Indian reprint- 2009, Published by Pvt. Ltd, 13. B.D.Chaurasia’s, Humana Anatomy Vol New Delhi. P.No. 361 & 362 and 346-348. 3, Head, Neck and Brain, 5th edition, Reprint 10. B.D.Chaurasia’s, Humana Anatomy Vol 2005-2009. CBS Publishers & Distributors 3, Head, Neck and Brain, 5th edition, Reprint PVT Ltd , New Delhi. P.No.337-376. 2005-2009. CBS Publishers & Distributors CORRESPONDING AUTHOR PVT Ltd , New Delhi. P.No.337-376. Dr. S. N. Belavadi 11. Michal Donaghy, Brains Disease of Ph.D Scholar Nervous System, 1st edition 1993. 12th Department of Kayachikitsa, Ayurveda edition 2009. Edited by oxford University Mahavidyalaya Press republised 2009-2011 Printed in india Hubli, Karnataka, India by sirohi brother, Noida (up). P.No.526-528. Email: [email protected] 12. www.medicalnewstoday.com Source of support: Nil Conflict of interest: None Declared

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