Opt. Lec 2b - Ocular neurology

Question 1

Which part of the CNS when damaged can be responsible for nystagmus?

Answer 1

Cerebellum - stabilises eye movements

Question 2

What are the 2 parts of the brain stem involved in vision and what are they responsible for?

Answer 2

Midbrain = superior and inferior colliculi (visual and auditory reflexes respectively
Contains nuclei involved in eye function : oculomotor (cranial nerve III), trochlear (cranial nerve IV) Pretectal

Pons includes nuclei involved with eye function - trigeminal (cranial nerve V), Abducent (cranial nerve VI) Facial (cranial nerve VII) Vestibulocochlear (cranial nerve VIII)

Question 3

What is the oculomotor nerve ( cranial nerve III) responsible for?

Answer 3

Nuclei - main
Motor supply to levator palpebrae superioris, recti and oblique

Accessory - parasympathetic supply to ciliary body muscles and the sphincter Pupillae

Damage = ptosis, strabismus, dilated pupil, loss of accommodation due to paralysis of ciliary muscle.
Commonly caused by cerebral aneurism

Question 4

What is the trochlear (cranial nerve IV) responsible for?

Answer 4

Motor supply to oblique which are involved in looking down,

It is the thinnest cranial nerve - susceptible to trauma t the base of the skull and spine

Due to paralysis of optic muscle causes strabismus (+compensatory head tilt) and Diplopia

Question 5

What is the trigeminal nerve (cranial nerve V) responsible for?

Answer 5

Has 4 nuclei located throughout the brainstem

3 branches which supply the eye and adnexa - 1 ophthalmic and 2 maxillary

Sensory nerves from:
Adnexa - lacrimal gland, eyelids, conjunctiva
Eye - cornea, sclera, iris and ciliary body

Sympathetic nerves to the
Adnexa - lacrimal gland
Eye - ciliary body and dilator Pupillae

Affected by the shingles virus

Question 6

What is the Abducent nerve (cranial nerve VI) responsible for ?

Answer 6

Pons

Motor supply to recti which are involved in looking outwards

It is a long nerve susceptible to raised pressure and inflammation inside the cranium

Damage to this nerve causes strabismus (deviating inwards)

Sometimes first presentation of MS

Question 7

What is the Facial nerve (cranial nerve VII) responsible for?

Answer 7

Pons

Motor supply to facial muscles including obicularis oculi
Serves the efferent part of blink reflex to corneal irritation/light/an approaching object to noise

Parasympathetic nerve supply to the lacrimal gland and the lacrimal nucleus that lies next to the salivary nucleus (crocodile tears)

Affected in Bells Palsy

Question 8

What is the Vestibulocochlear nerve (cranial nerve VIII) responsible for?

Answer 8

Pons

The vestibular part received impulses from the cerebellum and semi-circular canals. Coordinated hear and eye movements towards objects and holds eyes steady when spun around (vestibulo-ocular reflex)

The cochlear part
Receives impulses from the cochlea. Responsible for the afferent part of the blink reflex to sound.

Question 9

Which statement about the cranial nerve damage is TRUE?
A, Cranial nerve III damage can cause corneal ulcer
B. Cranial nerve IV damage can cause strabismus
C. Cranial nerve V can cause ptosis
D. Cranial nerve VI damage can cause lagophthalmos
E. Cranial nerve VII damage can cause nystagmus

Answer 9

B

Question 10

Which cranial nerve holds the eyes steady hen spun around? 
A. III
B. VIII
C. IV
D. VI
E. V

Answer 10

B