Cranial Nerve Function AP Review o 12 pairs

Cranial Nerve Function- A&P Review o 12 pairs of cranial nerves originate from brain & brainstem n o o Have sensory, motor or mixed functions. Enter and exit the brain rather than spinal cord Essentially reflects brainstem activity

Cranial Nerve I- Olfactory Nerve o Not routinely tested. n Test with: o o o Report of loss of smell Head trauma Abnormal mental status Suspected intracranial lesion Sensory function n With eyes closed occlude nares and present aromatic substance Able to correctly identify aromatic substance

Cranial Nerve II- Optic Nerve o Sensory Function n Visual acuity o n Visual fields by confrontation o n Snellen: 20/20 OS, 20/20 OD, 20/20 OU Peripheral fields intact by confrontation Assess optic disc o o Color & shape Optic disc creamy yellow, round, with distinct margins

Cranial Nerve III, IV, VI o CN III- Oculomotor n Motor Function o o Medial, superior, inferior rectus muscles & inferior oblique muscles Levator palpebrae muscles (elevate eyelids) n n Parasympathetic o Muscles of iris & ciliary body n o PERRLA CN IV- Trochlear n Motor Function o o Palpebral fissures symmetrical, no ptosis Superior oblique CN VI- Abducens n Motor Function o Lateral rectus o EOMS intact without nystagmus

Cranial Nerve V- Trigeminal o Motor Function n Palpate temporal & masseter muscles as patient clenches teeth Try to separate jaw by pushing down on chin Jaw strength equal bilaterally o o Sensory Function n Test light sensation with cotton ball over o o o Forehead (ophthalmic) Cheeks (maxillary) Chin (mandibular) Sensation intact and equal bilaterally

Cranial Nerve VII- Facial o Motor Function Smile, frown, close eyes tightly(against attempt to open, lift eyes, show teeth & puff cheeks Facial muscles intact & symmetrical n o Sensory Function n Not tested routinely o n Test only if suspect facial nerve injury Taste on anterior 2/3 rds of tongue Apply cotton applicator to tongue with solution of sugar, salt, or lemon juice Able to correctly identify sweet, salty & sour o

Corneal Reflex Only perform if patient with abnormal facial sensation or movement o Remove contact lenses o Lightly touch cornea with wisp of cotton from side o Tests the sensory afferent in CN V & motor efferent CN VII Corneal Reflex Intact o

Cranial Nerve VIII- Acoustic o AKA n o Vestibulocochlear Nerve Sensory Function n Assess hearing acuity: o o Ability to hear normal conversation Whispered voice test Whispered words heard bilaterally Weber tuning fork test Tone heard midline without lateralization Rinne tuning fork test AC >BC

Cranial Nerve IX and X o o o CN IX- Glossopharyngeal CN X- Vagus Motor Function n Swallow o n Depress with tongue blade & note pharyngeal movement as patient says “ahhh” o n o Uvula rises midlines with phonation Touch posterior pharyngeal wall to illicit gag reflex o n Swallowing intact Gag reflex intact Note sound of voice Sensory Function n n Taste on posterior 1/3 of tongue Not routinely tested

Cranial Nerve XI- Spinal Accessory o Motor Function n n Rotate head against resistance Shrug shoulders against resistance Shoulder shrug and head movement intact and equal bilaterally

Cranial Nerve XII-Hypoglossal o Motor Function n Have patient protrude tongue o o No wasting or tremors Tongue midline n n Tongue protrudes midline without tremors Say “light, tight, dynamite” o Note if clear and distinct n “Light, tight, dynamite” clear and distinct