Cranial Nerves

Question 1

CN I

Answer 1

Olfactory
Afferent
Function: Smell
Test: Test sense of smell on each side using common, non-irritating odor
Abnormal findings: Anosmia (inability to detect smells), seen with frontal lobe lesions

Question 2

CN II

Answer 2

Optic
Afferent
Function: vision
Test: Visual Acuity test (Snellen eye chart); Visual Field Test (temporal and vertical peripheral vision by confrontation)
Abnormal Findings: Blindness, myopia (impaired far vision), presbyopia (impaired near vision) ; Field defects: homonymous hemianopsia (loss of vision on same side in both eyes)

Question 3

CN III

Answer 3

Oculomotor
Efferent, Somatic, Visceral
Function: Elevates eyelids, turns eye up,down&in (convergence), constricts pupil, accommodates lens
Test: shine light in eye, accommodation to light, pupil moves medially when viewing object at close range
Abnormal Findings: absence of pupillary reflex, lateral strabismus (exotropia) Anisocoria (unequal pupils), Horner’s Syndrome, CNIII Paralysis

Question 4

CN IV

Answer 4

Trochlear
Efferent (somatic)
Function: Turns the adducted eye down and causes intorsion (inward rotation)
Test: saccades, smooth pursuit (follow moving finger) one eye at a time
Abnormal findings: impaired eye movements, ptosis, medial strabismus (diplopia or nystagmus)

Question 5

CN V

Answer 5

Trigeminal
Afferent, efferent
Function: sensation from face, cornea, anterior tongue; muscles of mastication, dampens sound
Test: test pain, light touch sensation; test corneal reflex (cotton); palpate temporal and masseter muscles (open mouth, move jaw side to side, bite on tongue depressor)
Abnormal findings: loss of facial sensation, numbness with lesion, trigger area, loss of corneal reflex, weakness, asymmetries in movement and strength

Question 6

CN VI

Answer 6

Abducens 
Efferent (somatic) 
Function: turns eye out 
Test: saccades, smooth pursuit
Abnormal findings: impaired eye movements, ptosis, strabismus

Question 7

CN VII

Answer 7

Facial
Afferent, efferent (somatic and visceral)
Function: taste anterior tongue, muscle of facial expression, dampens sound (stapedius), tearing, salivation
Test: symmetry of facial muscles (elevate eyebrows and forehead, smile, frown, pucker lips, close eyes tight, puff out cheeks) ; apply sweet, salty, sour to lateral anterior tongue
Abnormal findings: paralysis, unilateral LMN (Bells palsy), bilateral LMN (GBS), unilateral UMN (stroke), decreased taste

Question 8

CN VIII

Answer 8

Vestibulocochlear
Afferent
Function: balance, hearing
Test: balance and protective function(VSR), eye-head coordination (VOR), auditory acuity (tuning fork), Rinne test
Abnormal findings: vertigo, balance, disequilibrium, gaze instability, nystagmus, deafness, tinnitus, unilateral conductive loss, sensorineural loss

Question 9

CN IX

Answer 9

Glossopharyngeal
Afferent, Efferent
Function: taste from posterior tongue, sensation post. Tongue, oropharynx, salivation
Test: apply sweet, salty, sour to posterior tongue, swallowing, gag reflex, phonation
Abnormal findings: loss of taste

Question 10

CN X

Answer 10

Vagus
Afferent, efferent
Function: thoracic and abdominal viscera, muscle of larynx and pharynx, dec HR, inc, GI motility
Test: swallowing, phonation, say ”ah”
Abnormal findings: dysphasia, dysphasia, dysarthria

Question 11

CN XI

Answer 11

Spinal accessory
Efferent
Head movements (SCM, Trapz)
Test: strength of shoulder elevation, cervical flexion, rotation, SB, laryngeal elevation (adams apple)
Abnormal findings: LMN: atrophy, fasciculations, weakness; dysphagia

Question 12

CN XII

Answer 12

Hypoglossal
Efferent
Tongue movements and shape
Test: listen to articulation, examine resting position, tongue protrusion and side to side
Abnormal findings: dysarthria, atrophy, fasciculations, tongue deviations, UMN Lesion: tongue deviates away from side of cortical lesion, tremors or involuntary tongue Movements