Download - Cranial Nerve Function- A&P Review
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