Cranial nerve palsy

Question 1

What are the signs of Third Nerve Palsy and why?

Answer 1

Ptosis - Droopy Eyelid (loss of superior palpebrae superioris)
Eyes Downward (unopposed superior oblique)
Eyes Outwards (unopposed lateral rectus)

Question 2

Why do you have a dilated pupil in Third Nerve Palsy?

Answer 2

Two Reasons:
Overaction of Sympathetic causes mydriasis (dilation) with dilator pupillae (radial muscles)

Underactive Parasympathetic Branch causes miosis with sphincter pupillae (circular muscles)

Question 3

What are the types of lesions that cause Third Nerve Palsy, with examples?

Answer 3

Medical Lesions (hypertension, DM)
Surgical Lesions

Question 4

Explain how medical lesions work

Answer 4

Refer to PUPIL-SPARING palsies:
Vasculature to nerve affected - central part of nerve affected, not pupils as those parasympathetic fibres pass in the outer portion of the nerve

Question 5

Explain how surgical lesions work

Answer 5

Refer to PUPIL AFFECTING
Posterior communicating artery aneurysm, affects outer portion of nerve (parasympathetic fibres for pupils)

Question 6

What is the relation of the oculomotor nerve in relation to the Circle of Willis?

Answer 6

Oculomotor nerve runs in between the posterior cerebral artery and the superior cerebellar artery

Question 7

How would you treat Third Nerve Palsy?

Answer 7

Usually neurosurgical involvement - clipping of aneurysm // Control of underlying conditions

Question 8

What are the two signs of Fourth Nerve Palsy and why?

Answer 8

Eyes Upward (unopposed inferior oblique)
Eyes Inwards (unopposed inferior oblique)

Question 9

What are the signs of Sixth Nerve Palsy and why?

Answer 9

Eyes Inwards (unopposed medial rectus)