Cranial nerves ( function and palsies )

Question 1

Cranial nerve 1

Answer 1

Olfactory nerve

Question 2

Function of cranial nerve 1

Answer 2

Smell

Question 3

Pathway of cranial nerve 1

Answer 3

Cribiform plate

Question 4

Cranial nerve 1 palsy

Answer 4

1. head injury
2. tumor of olfactory groove
3. olfaction is temporarily lost after upper respiratory tract infection

Question 5

Cranial nerve II

Answer 5

Optic nerve

Question 6

visual pathway

Answer 6

1. Light allowed in by pupillary aperture
2. light is converted to action potential by retinal rod, cone and ganglion cells
3. Nasal visual field -> temporal retina
4. Temporal visual field -> Nasal retina
5. Axons from the optic nerve decussate at the optic chiasm
6. fibres from the nasal retina cross to form the optic tract
7. each optic tract carres information from the contralateral visual hemisphere
8. Reach lateral genticulate body
9. then pass in the optic radiation through the pariteal and temporal lobes to reach the visual cortex of the occipital lobe

Question 7

Ipsilateral mononuclear blindless

Answer 7

complete optic nerve lesion

Question 8

bitemporal hemianopia

both temporal visual fields

Answer 8

1. lesion at the optic chiasm

Question 9

Homonymous hemianopia

right or left - one nasal field and one temporal field of each eye

Answer 9

1. lesion at optic chiasm

Question 10

homonymous quadrantanopia

Answer 10

1. temporal lesiom

Question 11

homonymous hemianopia with macular sparing

Answer 11

lesion at the optic cortex

Question 12

cranial nerve III

Answer 12

Occulomotor nerve

Question 13

cranial nerve III function

Answer 13

1. Eye movement
   - Medial rectus
   - Inferior rectus
   - Superior rectus
   - Inferior oblique
2. Levator Palpebrae superioris -
3. Pupillary constriction
4. Accomadation

Question 14

Pathway of Cranial nerve III

Answer 14

1. Superior orbital fissue

Question 15

Cranial nerve III palsy

Answer 15

Palsy results in

• ptosis
• ‘down and out’ eye
• dilated, fixed pupil

Question 16

Causes of cranial nerve III lesion

Answer 16

1. aneurysm of Posterior communicating artery
2. infarction of the nerve - diabetes
3. mid brain infarction or tumor of midbrain

Question 17

Cranial nerve IV

Answer 17

1. trochlear nerve

2. supplies superior oblique muscle

Question 18

Cranial nerve IV palsy

Answer 18

1. Palsy results in defective downward gaze → vertical diplopia
2. commonly caused by head injury
3. mostly bilateral but very rare

Question 19

Cranial nerve V

Answer 19

1. largest cranial nerve
2. three branches ;
   - V1 - opthalmic nerve
   - V2 - Maxillary nerve
   ( both purely sensory)
   - V3 - Mandibular nerve
   ( motor as well as sensory)

Question 20

Cranial nerve V - V1

Answer 20

1. superior orbital fissure

2. sensory information from the scalp and forehead, the upper eyelid, the conjunctiva and cornea of the eye, the nose

Question 21

Cranial nerve V - V2

Answer 21

1. The maxillary nerve (V2)
2. carries sensory information from the lower eyelid and cheek, the nares and upper lip, the upper teeth and gums, the nasal mucosa, the palate and roof of the pharynx,
3. Foramen rotundum

Question 22

Cranial nerve V - V3

Answer 22

1. Foramen Ovale
2. carries sensory information from the lower lip, the lower teeth and gums, the chin and jaw
3. mandibular division (V3) of the trigeminal nerve controls the movement of eight muscles, including the four muscles of mastication: the masseter, the temporal and the medial and lateral pterygoids

Question 23

Cranial Nerve VI

Answer 23

1. Abducens
2. controls lateral rectus muscle
3. superior orbital fissure

Question 24

Cranial Nerve VI palsy

Answer 24

1. Palsy results in defective abduction → horizontal diplopia
2. Eye cannot be fully abducted and esotropia (inward eye deviation) may be visible

Question 25

Cranial nerve VI palsy causes

Answer 25

1. Multiple sclerosis
2. Wernicke’s encephalopathy
3. Pontine stroke