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Cranial Nerves

I through XII

Olfactory Nerve I

Sense of smell

Damage causes impaired sense of smell

Optic Nerve II

Provides vision

Damage causes blindness in visual field

Oculomotor Nerve III

Somatic and Autonomic motor function Eye movement (Superior, inferior, medial rectus muscles and inferior

oblique muscle), opening of eyelid (levator palpebrae superioris), constriction of pupil (circular muscle), focusing (ciliary muscle and accomodation)

Damage causes drooping eyelid, dilated pupil, double vision, difficulty focusing and inability to move eye in certain directions

Trochlear Nerve IV

Eye movement (superior oblique muscle)

Damage causes double vision and inability to rotate eye inferolaterally

Trigeminal Nerve V

Ophthalmic branch – sensations from nasal cavity, skin of forehead, upper eyelid, eyebrow, nose

Maxillary branch – sensations from lower eyelid, upper lips and gums, teeth of the maxilla, cheek, nose, palate, pharynx

Mandibular branch – sensations from teeth of the mandible, lower gums and lips, palate, tongue. Motor function of temporalis and masseter muscles.

Damage produces loss of sensation and impaired chewing

Abducens Nerve VI

Provides eye movement (lateral rectus m.)

Damage results in inability to rotate eye laterally and at rest eye rotates medially

Facial Nerve VII

Somatic Motor - facial expressions Autonomic Motor - salivary and lacrimal glands, mucous

membranes of nasal and palatine mucosa Special Sensory - taste on anterior 2/3’s of tongue Damage produces sagging facial muscles and disturbed

sense of taste (no sweet and salty)

Branches of Facial Nerve

Clinical test: Test anterior 2/3’s of tongue with substances such as sugar, salt, vinegar, and quinine; test response of tear glands to ammonia fumes; test motor functions by asking subject to close eyes, smile, whistle, frown, raise eyebrows, etc.

Vestibulocochlear Nerve VIII

Special Sensory Provides hearing (cochlear branch) and sense of

balance (vestibular branch) Damage produces deafness, dizziness, nausea,

loss of balance and nystagmus

Glossopharyngeal Nerve IX

Somatic motor – Swallowing and voice production via pharyngeal muscles

Autonomic motor - salivation, gagging, control of BP and respiration Sensations from posterior 1/3 of tongue including taste Sensations from baroreceptors and chemoreceptors Damage results in loss of bitter and sour taste and impaired swallowing,

blood pressure anomalies (with CN X).

Vagus Nerve X Sensations from skin at back of ear,

external acoustic meatus, part of tympanic membrane, larynx, trachea, espophagus, thoracic and abdominal viscera

Sensations from bararoceptors and chemoreceptors

Special sensory – taste from epiglottis and pharynx

Somatic motor – Swallowing and voice production via pharyngeal muscles

Autonomic motor – smooth muscle of abdominal viscera, visceral glands secretions, relaxation of airways, and normal or decreased heart rate.

Damage causes hoarseness or loss of voice, impaired swallowing, GI dysfunction, blood pressure anomalies (with CN IX), fatal if both are cut

Accessory Nerve IX

Swallowing, head, neck and shoulder movement via trapezius and sternocleidomastoid and pharyngeal muscles

Damage causes impaired head, neck, shoulder movement

Hypoglossal Nerve XII

Tongue movements for speech, food manipulation and swallowing

If both are damaged – can’t protrude tongue

If one side is damaged – tongue deviates towards injured side

Cranial Nerve Disorders Trigeminal neuralgia (tic douloureux) recurring episodes of intense stabbing pain in

trigeminal nerve area (near mouth or nose)

pain triggered by touch, drinking, washing face

treatment may require cutting nerve

Bell’s palsy disorder of facial nerve causes paralysis of facial

muscles on one side

may appear abruptly with full recovery within 3-5 weeks

Lecture Objectives Lecture ObjectivesAfter today After today’’s lecture, the student will be able s lecture, the student will be able

to: to:

Describe how to examine the function of Describe how to examine the function of the cranial nerves the cranial nerves

Describe the more common abnormal Describe the more common abnormal findings associated with function of findings associated with function of the cranial nerves the cranial nerves

Describe abnormal findings that may Describe abnormal findings that may indicate a systemic disease indicate a systemic disease

CRANIAL NERVE EXAMINATION CRANIAL NERVE EXAMINATION

Objectives of the cranial nerve examination Objectives of the cranial nerve examination

Recognize signs and symptoms of Recognize signs and symptoms ofcranial nerve disorders cranial nerve disorders

Recognize signs and symptoms of Recognize signs and symptoms ofsystemic diseases systemic diseases

Distinguish between dental and neurological Distinguish between dental and neurological disorders disorders

Referral to physician for evaluation

CRANIAL NERVE EXAMINATION CRANIAL NERVE EXAMINATION

Evaluate function of the cranial Evaluate function of the cranialnerves during interview and clinical nerves during interview and clinicalexamination examination

Not test routinely Not test routinely

CN I CN I ––Olfactory Nerve Olfactory Nerve

Assess patency of nostrils Assess patency of nostrils


Present aromatic Present aromatic substance substance

Patient should be Patient should be able to identify the able to identify the odor with each odor with each nostril nostril


Altered smell or taste Altered smell or taste

Anosmia Anosmia––decrease or loss of smell decrease or loss of smell--Bilateral Bilateral––smoking, allergic rhinitis, smoking, allergic rhinitis,

cocaine, aging cocaine, aging

--Unilateral Unilateral––neurogenic, frontal lobe neurogenic, frontal lobe masses masses

Phantom smells Phantom smells

CN II CN II ––Optic Nerve Optic Nerve

Visual acuity Visual acuity

--Usually assess Usually assessduring interview during interview

–Snellenchartfor far vision



--Usually assess Usually assessduring interview during interview



--Rosenbaum Rosenbaumnear vision chart near vision chart

--Over 40 yrs old Over 40 yrs old



--Health History Health History


Visual acuity Visual acuity--Myopia Myopia--nearsightedness nearsightedness

--Hyperopia Hyperopia--farsightedness farsightedness

--Presbyopia Presbyopia––loss of accommodation loss of accommodation


Visual acuity Visual acuity--Diabetic retinopathy Diabetic retinopathy


Visual fields Visual fields

--Confrontation test Confrontation test


Pupillary light reflex Pupillary light reflex --direct light reflex direct light reflex

--consensual light reflex consensual light reflex

CN II CN II ––Optic Nerve Optic NervePupillary light reflex Pupillary light reflex

--direct light reflex direct light reflex

--consensual light consensual light reflex reflex

Absent or delayed pupillary light reflex

CNS trauma, Increased

intracranialpressure

CN III CN III ––Oculomotor Nerve Oculomotor Nerve

Accommodation Accommodation

Contraction of pupillary constrictor ms

Contraction of ciliary ms increases curvature of lens

Contraction of medial rectus ms causes convergence


Extraocular movements Extraocular movements

Oculomotor nerve elevates upper eyelid

Innervates –levator palpebrae superioris ms

Ptosisdrooping upper eyelid

Myasthenia gravis

Horner’s syndrome

CN III, IV, and VI CN III, IV, and VI ––Oculomotor, Oculomotor,Trochlear, and Abducens nerves Trochlear, and Abducens nerves

Extraocular movements Extraocular movements--Cardinal fields of gaze Cardinal fields of gaze



Oculomotornerve turns eye up,down and medially.

Innervates –superior rectus msmedial rectus msinferior rectus msinferior oblique ms

CN IV CN IV ––Trochlear Nerve Trochlear Nerve


Trochlearnerve turns the eye downward and inward.

Innervates –superior oblique ms

CN VI CN VI ––Abducens Nerve Abducens Nerve


Abducensnerve turnsthe eye laterally

Innervates –lateral rectus ms

CN III, IV, and VI CN III, IV, and VI ––Oculomotor, Oculomotor,Trochlear, and Abducens Nerves Trochlear, and Abducens Nerves

Nystagmus Nystagmus--fine oscillation (tremor) of fine oscillation (tremor) ofthe eyes the eyes

--Multiples etiologies Multiples etiologies••Vision impairment as child Vision impairment as child

••Vestibular disorders Vestibular disorders

••Cerebellar disorders Cerebellar disorders

••Drug toxicity (sedatives, anticonvulsants, alcohol) Drug toxicity (sedatives, anticonvulsants, alcohol)

Diplopia Diplopia––double vision double vision

CN V CN V ––Trigeminal Nerve Trigeminal NerveSensory Sensory

--Patient Patient’’s eyes closed, s eyes closed, test light touch on test light touch on face with cotton wisp face with cotton wisp

–Test forehead, cheeks, and chin

–Assess patient’s ability to detect sharp, dull, light pressure, hot and cold

CN V CN V ––Trigeminal Nerve Trigeminal NerveSensory Sensory

--Corneal reflex Corneal reflex

--Intra Intra--oral: oral:mucosa mucosateeth teeth

CN V CN V ––Trigeminal Nerve Trigeminal Nerve

Motor Motor

--Muscles of mastication Muscles of mastication

--Have patient bite against Have patient bite against resistance resistance

--Have patient protrude Have patient protrude mandible against resistance mandible against resistance

--Have patient go into lateral Have patient go into lateral excursive movements excursive movements against resistance against resistance

CN V CN V ––Trigeminal Nerve Trigeminal Nerve

Motor Motor--Rare Rare

Sensory Sensory

--Paresthesia Paresthesiafollowing oral surgery following oral surgery

--Trigeminal neuralgia Trigeminal neuralgia

CN VII CN VII ––Facial Nerve Facial Nerve

Motor Motor--Muscles of facial Muscles of facial

expression expression

CN VII CN VII ––Facial Nerve Facial NerveMotor Motor--Damage to the peripheral nerve presents Damage to the peripheral nerve presents

as paralysis to the entire side of face as paralysis to the entire side of face

--A central lesion (e.g., stroke) on one side A central lesion (e.g., stroke) on one side affects mainly the lower face on the side of affects mainly the lower face on the side of the lesion the lesion

--Bell Bell’’s palsy s palsy

CN VII CN VII ––Facial Nerve Facial NerveSensory Sensory

--Taste to the anterior 2/3 of the tongue Taste to the anterior 2/3 of the tongue

--Loss or altered taste following a stroke or Loss or altered taste following a stroke or damage to the lingual nerve (local damage to the lingual nerve (local anesthetic injection, laceration of tongue) anesthetic injection, laceration of tongue)

CN VIII CN VIII ––Vestibulocochlear VestibulocochlearNerve Nerve

--Observe if the patient turns one ear towards you Observe if the patient turns one ear towards you --Evaluate hearing using a ticking watch, rub Evaluate hearing using a ticking watch, rub

fingers together, whisper. fingers together, whisper.


--Observe equilibrium Observe equilibrium as patient walks or as patient walks or stands stands


Deafness Deafness––complete or partial, complete or partial, unilateral or bilateral unilateral or bilateral

Dysfunction of vestibular apparatus Dysfunction of vestibular apparatus (e.g., (e.g.,MMééni nièèrereSyndrome) Syndrome)--Dizziness Dizziness

--Falling Falling

--Abnormal eye movements Abnormal eye movements

--Nausea and vomiting Nausea and vomiting

CN IX CN IX ––Glossopharyngeal GlossopharyngealNerve Nerve

Sensory Sensory

--Sensation to the posterior 1/3 of the tongue Sensation to the posterior 1/3 of the tongue including taste and to the mucous including taste and to the mucous membranes of the pharynx membranes of the pharynx

--Sensory part of gag reflex Sensory part of gag reflex

CN IX CN IX ––Glossopharyngeal GlossopharyngealNerve Nerve Motor Motor

--Middle constrictor muscle of pharynx Middle constrictor muscle of pharynx

--Stylopharyngeus Stylopharyngeusmuscle muscle

CN X CN X ––Vagus Nerve Vagus NerveSensory Sensory

••Sensation to the inferior pharynx, larynx, heart, Sensation to the inferior pharynx, larynx, heart, lungs, and gut. lungs, and gut.

••Not tested Not tested

CN X CN X ––Vagus Nerve Vagus NerveMotor Motor--Soft palate, pharynx, and larynx Soft palate, pharynx, and larynx

--Patient say Patient say ““Aah Aah””and watch soft palate and watch soft palate rise rise

CN X CN X ––Vagus Nerve Vagus NerveMotor dysfunction Motor dysfunction

--Recurrent laryngeal nerve Recurrent laryngeal nerve ––hoarseness or weakness in the voice hoarseness or weakness in the voiceinability to cough voluntarily inability to cough voluntarily

--Dysphagia Dysphagia––difficulty swallowing difficulty swallowing

CN XI CN XI ––Accessory Nerve Accessory Nerve

Sternocleidomastoid ms Sternocleidomastoid ms

CN XI CN XI ––Accessory Nerve Accessory Nerve

Trapezius muscles Trapezius muscles

CN XII CN XII ––Hypoglossal Nerve Hypoglossal Nerve

Motor Motor--Muscles of tongue Muscles of tongue

--Geniohyoid Geniohyoidand andthyrohyoid thyrohyoidmuscles muscles

CN XII CN XII ––Hypoglossal Nerve Hypoglossal Nerve

Have patient stick Have patient stick out tongue. Should out tongue. Should be symmetrical. No be symmetrical. No tremors or wasting. tremors or wasting.

Tongue will deviate Tongue will deviate toward side of lesion toward side of lesion when tongue when tongue protruded. protruded.

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