Cranial Nerves

Question 1

CN I Olfactory

Answer 1

Foramen: cribiform plate
Sensory
smell
hold stuff under nostrils

Question 2

CN II Optic

Answer 2

Foramen: optic canal
Sensory
vision

retinal ganglion cells -> optic chiasm -> thalamus -> primary visual cortex in the occipital lobe

optic discs (fundoscopy)
pupillary responses eg. RAPD
visual acuity
visual fields

Question 3

CN III Oculomotor

Answer 3

Foramen: superior orbital fissure

Motor: sup/medial/inf rectus, inferior oblique

Parasympathetic: ciliary muscle and pupillary constriction muscles (light reflex)

Test: response to light and accomodation

Question 4

CN IV Trochlear

Answer 4

Foramen: superior orbital fissure
Motor (superior oblique)
move eye medial and down

Question 5

CN V Trigeminal

Answer 5

Foramen: V1 ophthalmic - superior orbital
V2 maxillary - foramen rotunda
V3 mandibular - foramen ovale

Sensory: innervates face (ophthalmic, mandibular and maxillary)

Motor: to muscles of mastication
- masseter, temporalis, medial and lateral pterygoids

Test: sensory touch forehead chin and cheek
corneal reflex

Motor: jaw jerk and clench teeth (masseter), temporals feel temple while clench teeth

Question 6

CN VI Abducens

Answer 6

Foramen: superior orbital fissure
Motor
movement of lateral rectus - palsy eye looks towards nose

long intracranial course - affected by rising ICP (false localising sign)

Question 7

Test of CN III, IV, VI

Answer 7

follow finger with eyes, draw H shape

Question 8

CN VII Facial

Answer 8

Foramen: internal acoustic meatus (cranium)
(exits skull at stylomastoid foramen)
Both

Motor: muscles of facial expression
Sensory: taste (ant 2/3 tongue)
Parasymp: salivation and lacrimation

Test: facial expressions: close eyes against resistance, puff out cheeks, crease forehead, reveal teeth

Corneal reflex to test pontine function

Question 9

CN VIII vestibulocochlear

Answer 9

Foramen: internal acoustic meatus
Sensory
Hearing and balance

Hearing: audiometry, tragal rub
Test: weber (forehead) Rinne’s (mastoid)

Weber: conductive louder on affected side, sensioneural louder on normal ear
Rinne: conductive bone is louder than air (negative test)

Question 10

CN IX Glossopharyngeal

Answer 10

Foramen: jugular
Both

Sensory: taste (ant 1/3), proprioception for swallowing (pharynx) and blood pressure receptors

Motor: swallow and gag reflex

• test open mouth and say ah, watch for elevation of soft palate
• if lesion (unlat weakness) - deviation of uvula AWAY from lesion

Parasympathetic: saliva production

Involved in gag reflex

Question 11

CN X Vagus

Answer 11

Foramen: jugular
Both

Sensory: chemoreceptors, pain receptors, sensation of external ear, larynx and pharynx

Motor: HR and SV, peristalsis, speech and swallowing

Parasymp: same areas as motor, plus thoracic and abdomen

Question 12

Test for IX and X

Answer 12

patient say ah, soft palate raised, uvuAl deviation (motor lesion on opposite side
Gag reflex

Question 13

CN XI Spinal Accessory

Answer 13

Foramen: jugular
Motor
head rotation and shoulder shrugging via sternocleidomastoid and trapezius

Test: shrug shoulders against resistance
Testing right SCM: ask patient to turn head to left
- weakness usually iatrogenic -> biopsy LN

Question 14

CN XII Hypoglossal

Answer 14

Foramen: hypoglossal canal
Motor
Movement of tongue

Test: stick out tongue - lesion tongue will deviate ToWards the affected side

Question 15

Eye movements

Answer 15

CN III: inf/sup/medial rectus, inf oblique
CN IV: superior oblique
CN VI: lateral rectus