Cranial Nerves

Question 1

CN I (Olfactory)

Answer 1

Sensory only
Function - smell
Pathway - cribriform plate

Question 2

CN II (Optic)

Answer 2

Sensory only
Function - sight
Pathway - optic canal

Question 3

CN III (Oculomotor)

Answer 3

Motor only
Function - eye movement (MR, IO, SR, IR), pupil constriction, accomodation, eyelid opening
Palsy results in ptosis, ‘down and out’ eye, dilated, fixed pupil
Pathway - superior orbital fissure (SOF)

Question 4

CN IV (Trochlear)

Answer 4

Motor
Function - eye movement (SO)
Palsy results in defective downward gaze -> vertical diplopia
Pathway - superior orbital fissure (SOF)

Question 5

CN V (Trigeminal)

Answer 5

Both (sensory and motor)
Function - facial sensation, mastication
Lesions may cause trigeminal neuralgia, loss of corneal reflex (afferent), loss of facial sensation, paralysis of mastication muscles, deviation of jaw to weak side
Pathway - V1 - superior orbital fissure (SOF); V2 - foramen rotundum; V3 - foramen ovale

Question 6

CN VI (Abducens)

Answer 6

Motor only
Function - eye movement (LR)
Palsy results in defective abduction -> horizontal diplopia
Pathway - superior orbital fissure (SOF)

Question 7

CN VII (Facial)

Answer 7

Both (sensory and motor)
Function - facial movement, taste (anterior 2/3rds of tongue), lacrimation, salivation
Lesions may result in flaccid paralysis of upper + lower face, loss of corneal reflex (efferent), loss of taste, hyperacusis
Pathway - internal auditory meatus

Question 8

CN VIII (Vestibulocochlear)

Answer 8

Sensory only
Function - hearing, balance
Can be affected in hearing loss, vertigo, nystagmus, acoustic neuromas (Schwann cell tumours of the cochlear nerve)
Pathway - internal auditory meatus

Question 9

CN IX (Glossopharyngeal)

Answer 9

Both (sensory and motor)
Function - taste (posterior 1/3rd of tongue), salivation, swallowing, mediates input from carotid body & sinus
Lesions may result in hypersensitive carotid sinus reflex, loss of gag reflex (afferent)
Pathway - jugular foramen

Question 10

CN X (Vagus)

Answer 10

Both (sensory and motor)
Function - phonation, swallowing, innervates viscera
Lesions may result in uvula deviates away from site of lesion, loss of gag reflex (efferent)
Pathway - jugular foramen

Question 11

CN XI (Accessory)

Answer 11

Motor only
Function - head and shoulder movement
Lesions may result in weakness turning head to contralateral side
Pathway - jugular foramen

Question 12

CN XII (Hypoglossal)

Answer 12

Motor only
Function - tongue movement
Tongue deviates towards side of lesion
Pathway - hypoglossal canal

Question 13

Corneal relex

Answer 13

Afferent limb - ophthalmic nerve (V1)

Efferent limb - facial nerve (VII)

Question 14

Jaw jerk reflex

Answer 14

Afferent limb - mandibular nerve (V3)

Efferent limb - mandibular nerve (V3)

Question 15

Gag reflex

Answer 15

Afferent limb - glossopharyngeal nerve (IX)

Efferent limb - vagal nerve (X)

Question 16

Carotid sinus reflex

Answer 16

Afferent limb - glossopharyngeal nerve (IX)

Efferent limb - vagal nerve (X)

Question 17

Pupillary light reflex

Answer 17

Afferent limb - optic nerve (II)

Efferent limb - oculomotor nerve (III)

Question 18

Lacrimation reflex

Answer 18

Afferent limb - ophthalmic nerve (V1)

Efferent limb - facial nerve (VII)