53. Oculomotor nerve (CN III) lesion

Question 1

Neurological examination

Answer 1

Examine together with CN II by checking pupillary reflex. Both pupils should constrict when one of the eyes is in contact with light.
Extraocular movements composed of CN III, IV and VI
- I: Pursuit: Pat. keeps his/her head still and following with their eyes the moving target in front of their face, that draws the letter “H”
- II: Saccades: Rapid, conjugate movement of the eyes between objects
- III: Vestibulo-ocular movement: Fixating on an object while head us being turned passively

Question 2

Innervation of CN III

Answer 2

Superior, infectior & medial rectuses
Inferior oblique
Levator palpebrae
Efferent limb of pupillary reflex

Innervate some of the mus. that control eye movements

Question 3

Signs and symptoms when damaged (oculomotor nerve palsy)

Answer 3

Unable to move the eye normally
Ptosis (drooping eyelid)
Mydriasis (pupil dilation)
Strabismus
Diplopia

Complete oculomotor nerve palsy: Down & upward position in the affected eye

Question 4

Causes of oculomotor nerve palsy

Answer 4

Direct trauma, demyelinating diseases (MS), increased ICP (brain tumor, subarachnoid hemorrhage), microvascular diabetes, ischemia (insuff. of the vasa nervosa or small vessels that supply the nerve)

Question 5

Treatment

Answer 5

May resolve depending on cause.
Alleviate symptoms (pain and diplopia: NSAID for pain. If diplopia is from large-angle divergence of the visual axes, patch one eye. If angle of deviation is smaller, fusion in primary position often can be achieved using horizontal or vertical prism or both.