Lesions Of The Third Cranial Nerve

Question 1

Ptosis Of Upper Eyelid

Answer 1

• inactivation of the levator palpebrae superioris m
• unopposed orbicularis oculi

-contraction of frontalis muscle compensates for the ptosis
Wrinkled forehead
Raised eyebrow

Question 2

Lateral and Downward Deviation of the Affected Eye

Answer 2

• lateral strabismus (extropia)
• hypotropia
• Dipolopia: in all directions of gaze except on lateral gaze to the side of the third nerve lesion

Question 3

Pupillary Dilation

Answer 3

• loss of preganglionic parasympathetic innervation from Edinger-Westphal nucleus to the constrictor pupillae m
• unopposed action of the dilator pupillae m

Question 4

Paralysis of Accomodation

Answer 4

• ciliary m Innervated by Edinger-Westphal nucleus
• lack of pupillary constriction
• medial rectus m needed for convergence of the eye

Question 5

Aneurysms

Answer 5

Posterior cerebral or superior cerebellar arteries

Question 6

Tentorial Herniation of the Temporal Lobe

Answer 6

Displacement of the cerebral peduncle and stretching of the third nerve