Clinical (eye): cranial nerve palsies

Question 1

what are the extraocular muscles innervated by?

Answer 1

by three cranial nerves

Question 2

what will damage to one of the cranial nerves cause?

Answer 2

paralysis of its respective muscles

Question 3

what does damage to one of the cranial nerves causing paralysis of respective muscles result in?

Answer 3

alter the resting gaze of the affected eye

Question 4

what does lesion of the oculomotor nerve (CN III) affect?

Answer 4

affects most of the extraocular muscles

Question 5

how does oculomotor nerve (CN III) lesion present?

Answer 5

The affected eye is displaced laterally by the lateral rectus and inferiorly by the superior oblique
‘down and out’ position’

Question 6

what does lesion of the trochlear nerve (CN IV) affect?

Answer 6

A lesion of CN IV will paralyse the superior oblique muscle.

Question 7

how does lesion of the trochlear nerve (CN IV) present?

Answer 7

There is no obvious affect of the resting orientation of the eyeball. However, the patient will complain of diplopia (double vision), and may develop a head tilt away from the site of the lesion

Question 8

what does lesion of the abducens nerve (CN VI) affect?

Answer 8

will paralyse the lateral rectus muscle

Question 9

how does lesion of the abducens nerve (CN VI) present?

Answer 9

The affected eye will aDducted by the resting tone of the medial rectus
(unopposed action of medial rectus - pulling eyes inwards)