Cranial Nerve Function- A&P Review 12 pairs of cranial

nerves originate from brain & brainstem Have sensory, motor

or mixed functions.

Enter and exit the brain rather than spinal cord

Essentially reflects brainstem activity

Cranial Nerve I- Olfactory Nerve Not routinely tested.

Test with: Report of loss of smell Head trauma Abnormal mental status Suspected intracranial

lesion

Sensory function With eyes closed occlude nares

and present aromatic substance

Able to correctly identify aromatic substance

Cranial Nerve II- Optic Nerve

Sensory Function Visual acuity

Snellen: 20/20 OS, 20/20 OD, 20/20 OU

Visual fields by confrontation Peripheral fields intact

by confrontation

Assess optic disc Color & shape Optic disc creamy

yellow, round, with distinct margins

Cranial Nerve III, IV, VI CN III- Oculomotor

Motor Function Medial, superior, inferior rectus muscles

& inferior oblique muscles Levator palpebrae muscles (elevate

eyelids) Palpebral fissures symmetrical, no ptosis

Parasympathetic Muscles of iris & ciliary body

PERRLA

CN IV- Trochlear Motor Function

Superior oblique CN VI- Abducens

Motor Function Lateral rectus EOMS intact without nystagmus

Cranial Nerve V- Trigeminal Motor Function

Palpate temporal & masseter muscles as patient clenches teeth Try to separate jaw by pushing

down on chin

Jaw strength equal bilaterally

Sensory Function Test light sensation with

cotton ball over Forehead (ophthalmic) Cheeks (maxillary) Chin (mandibular)

Sensation intact and equal bilaterally

Cranial Nerve VII- Facial Motor Function

Smile, frown, close eyes tightly(against attempt to open, lift eyes, show teeth & puff cheeks

Facial muscles intact & symmetrical Sensory Function

Not tested routinely Test only if suspect facial nerve

injury Taste on anterior 2/3rds of tongue

Apply cotton applicator to tongue with solution of sugar, salt, or lemon juice

Able to correctly identify sweet, salty & sour

Corneal Reflex Only perform if patient

with abnormal facial sensation or movement

Remove contact lenses Lightly touch cornea

with wisp of cotton from side

Tests the sensory afferent in CN V & motor efferent CN VII

Corneal Reflex Intact

Cranial Nerve VIII- Acoustic AKA

Vestibulocochlear Nerve Sensory Function

Assess hearing acuity: Ability to hear normal

conversation Whispered voice test

Whispered words heard bilaterally

Weber tuning fork testTone heard midline without lateralization

Rinne tuning fork testAC >BC

Cranial Nerve IX and X CN IX- Glossopharyngeal CN X- Vagus Motor Function

Swallow Swallowing intact

Depress with tongue blade & note pharyngeal movement as patient says “ahhh” Uvula rises midlines with phonation

Touch posterior pharyngeal wall to illicit gag reflex Gag reflex intact

Note sound of voice Sensory Function

Taste on posterior 1/3 of tongue Not routinely tested

Cranial Nerve XI- Spinal Accessory Motor Function

Rotate head against resistance

Shrug shoulders against resistanceShoulder shrug and head

movement

intact and

equal

bilaterally

Cranial Nerve XII-Hypoglossal Motor Function

Have patient protrude tongue No wasting or tremors Tongue midline

Tongue protrudes midline without tremors

Say “light, tight, dynamite” Note if clear and distinct

“Light, tight, dynamite” clear and distinct