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 test Tone heard midline without lateralization  Rinne tuning fork test AC >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 resistance Shoulder 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