Cranial Nerves

Question 1

I

Answer 1

Olfactory

Function: smell

Test: sense of smell on each side, use common nonirritating odors; close off other nostril

Abnormal findings: Ansomia (inability to detect smells) –FRONTAL LOBE lesions

Question 2

II

Answer 2

Optic

Function: vision

Test: Visual acuity
CENTRAL=Snellen eye chart
VISUAL FIELDS = peripheral vision

Abnormal findings: blindness, myopia (impaired far vision), presbyopia (impaired near vision
Visual field deficits: homonymous hemianopsia

Question 3

II and III

Answer 3

Optic (II) and Oculomotor (III)

Function: pupillary reflexes

Test: Pupillary reactions (constriction) by shining light in eye
Examine pupillary size/shape

Abnormal findings: absence of pupillary constriction
Anisocoria (unequal pupils)
Horner’s syndrome
CN III paralysis

Question 4

III, IV and VI

Answer 4

Oculomotor (III), Trochlear (IV) and Abducens (VI)

Function:
CN III: turns eye up, down and in
CN IV: turns abducted eye down
CN VI: turns eye out

Test: Extraocular movements in all directions
Observe position of eye
Test pursuit eye movement

Abnormal findings:
Strabismus (eye deviates from normal conjugate position): eye pulled outward by CN VI; cannot look up/down/in
Impaired eye movements
Ptosis, pupillary dilation
Esotropia (eye pulled inward)
Eye cannot look out

Question 5

V

Answer 5

Trigeminal

Function: Sensory (face, cornea) and Motor (temporal and master muscles)

Test: pain, light touch: forehead, cheeks, jaws
Corneal reflex
Palpate muscles

Abnormal findings:
Loss of facial sensations, numbness with CN V lesion
Loss of corneal reflex IPSI
Weakness, wasting of muscles of mastication
Deviation of jaw when opened to IPSI side

Question 6

VII

Answer 6

Facial

Function: Facial expression

Test: motor function facial muscles (raise eyebrows, frown, show teeth, etc.)

Abnormal findings:
Paralysis IPSI facial muscles
Peripheral nerve injury: Bell’s palsy
CNS facial paralysis stroke

Question 7

VIII

Answer 7

Vestibulocochlear

Function: vestibular, VOR, cochlear function

Test: balance
Gaze instability with head rotations
Auditory acuity
Lateralization (Weber’s test): vibrating tuning fork on head check hearing
Air and bone conduction (Rinne’s test): tuning fork on mastoid process

Abnormal findings:
Vertigo, dysequilibrium
Nystagmus
Deafness, impaired hearing, tinnitus
Unilateral conductive loss
Sensorineural loss
Conductive loss

Question 8

IX and X

Answer 8

Glossopharyngeal (IX) and Vagus (X)

Function: Phonation, swallowing, palatal/pharynx control, gag reflex

Test: listen to voice quality
Examine for difficulty swallowing
Say “ah” and observe soft palate motion
Stimulate back of throat on each side

Abnormal findings:
Dysphonia: hoarseness (vocal cord paralysis) versus nasal quality (palatal weakness)
Dysphagia
Paralysis: palate fails to elevate (lesion of CN X), asymmetrical elevation, unilateral paralysis
Absent reflex: lesion of CN IX, possibly X

Question 9

XI

Answer 9

Accessory

Function: Trapezius, SCM

Test: Examine bulk, strength
Test shoulder elevation and flexion >90 deg
Test head rotation to CONTRA side
Test CS SB to each side

Abnormal findings: Atrophy, fasciculations, weakness
Inability to turn head to CONTRA side

Question 10

XII

Answer 10

Hypoglossal

Function: tongue movements

Test: articulation
Resting position of tongue
Tongue movements

Abnormal findings: Dysarthria (CN X or XII)
Atrophy or fasciculations of tongue
Impaired movements, deviation to weak side