Cranial Nerve 3, 4, and 6 palsies

Question 1

What components does CN 3 have?

Answer 1

CN 3 has both motor (central) and parasympathetic (peripheral) components.

Question 2

What are the motor components of CN 3?

Answer 2

Motor output to the ocular muscles

Question 3

What disease process primarily affects the motor component of CN 3?

Answer 3

Motor output of CN 3 is primarily affected by vascular diseases including: diabetes mellitus, due to decrease diffusion of oxygen and nutrients to the interior fibers from compromised vasculature that resides on outsides of the nerve.

Question 4

What are signs of a CN 3 motor output dysfunction?

Answer 4

1. ptsosis

2. down and out gaze (lateral rectus pulls outward, and superior oblique pulls downward)

Question 5

What are the parasympathetic components of CN 3?

Answer 5

Parasympathetic fibers on the periphery are first affected by compression (posterior communicating artery aneurysm (PICA) or uncal herniation).

Question 6

What are signs of parasympathetic dysfunction of CN 3?

Answer 6

1. blown pupil (unopposed sympathetic innvervation leads to dilation)
2. down and out gaze (lateral rectus pulls outward, and superior oblique pulls downward)

Question 7

What are signs of a CN 4 palsy?

Answer 7

1. eyes move upward (unopposed inferior oblique muscle) particularly with contralateral gaze
2. head tilt toward the side of the lesion

Question 8

What difficulties may patients with CN 4 palsy describe?

Answer 8

1. difficulty walking down stairs

Question 9

What are signs of CN 6 pasly?

Answer 9

Patient is unable to abduct eye (move laterally) and may have medially directed eye. Caused by unopposed medial rectus.