Cranial Nerve Assessment

I: Olfactory Nerve

• Type: Sensory
• Function: Smell
• Test: Occlude one nostril and present an aromatic substance; a person should be able to identify an odor on each side of the nose

II: Optic Nerve

• Type: Sensory
• Function: Vision
• Test: Check visual acuity and visual fields by confrontation and examine the ocular fundus with an ophthalmoscope to determine the color, size, and shape of the optic disc

III: Oculomotor Nerve

• Type: Mixed
• Motor Function: Most extraocular muscle movement, opening of eyelids
• Parasympathetic Function: Pupil constriction, lens shape
• Palpebral fissures should be equal in width
• Test: Check pupils for size, regularity, equality, direct and consensual light reaction, and accommodation and assess extraocular movements by the cardinal positions of gaze

IV: Trochlear Nerve

• Type: Motor
• Function: Down and inward movement of eye
• Test: Same as CN III

V: Trigeminal Nerve

• Type: Mixed
• Motor Function: Muscles of mastication
• Sensory Function: Sensation of face and scalp, cornea, mucous membranes of mouth and nose
• Motor Test: Palpate the temporal and masseter muscles as the person clenches the teeth; muscles should feel equally strong on both sides; try to separate the jaws by pushing down on the chin; normally this is not possible
• Sensory Test: With the person's eyes closed, test light touch sensation by touching a cotton wisp to the forehead, cheeks, and chin and ask the person to say when the touch is felt to test the ophthalmic, maxillary, and mandibular divisions of the nerve

VI: Abducens Nerve

• Type: Motor
• Function: Lateral movement of the eye
• Test: Same as CN III

VII: Facial Nerve

• Type: Mixed
• Motor Function: Facial muscles, close eye, labial speech, close mouth
• Sensory Function: Taste on anterior 2/3 of tongue (sweet, salty, sour, bitter)
• Parasympathetic Function: Saliva secretion
• Motor Test: Note mobility and facial symmetry as the person performs actions such as smile, frown, close eyes tightly, lift eyebrows, show teeth, and puff cheeks; when pressing the person's puffed cheeks in, air should escape equally from both sides

VIII: Acoustic Nerve

• Type: Sensory
• Function: Hearing and equilibrium
• Test: Hearing acuity is tested by assessing the ability to hear normal conversation and by the whispered voice test

IX: Glossopharyngeal Nerve

• Type: Mixed
• Motor Function: Pharynx (phonation and swallowing)
• Sensory Function: Taste on posterior 1/3 of tongue, pharynx (gag reflex)
• Parasympathetic Function: Parotid gland, carotid reflex
• Motor Test: Depress the tongue with a tongue blade and note pharyngeal movement as the person says “ahhh” or yawns; the uvula and soft palate should rise in the midline, and the tonsillar pillars should move medially; touching the posterior pharyngeal wall with a cotton applicator stick should elicit pharyngeal sensation, but avoid the gag reflex and the voice should sound smooth and not strained

X: Vagus Nerve

• Type: Mixed
• Motor Function: Pharynx and larynx (talking and swallowing)
• Sensory Function: General sensation from carotid body, carotid sinus, pharynx, viscera
• Parasympathetic Function: Carotid reflex
• Test: Tested together with CN IX

XI: Spinal Accessory Nerve

• Type: Motor
• Function: Movement of trapezius and sternomastoid muscles
• Test: Examine the sternomastoid and trapezius muscles for equal size; check equal strength by asking the person to rotate the head forcibly against resistance applied to the side of the chin; then ask the person to shrug their shoulders against resistance, which should feel equally strong on both sides

XII: Hypoglossal Nerve

• Type: Motor
• Function: Movement of tongue
• Test: Inspect the tongue; no wasting or tremors should be present and note the forward thrust in the midline as the person protrudes the tongue; also ask the person to say “light, tight, dynamite” and note that lingual speech is clear and distinct