CN III

Question 1

Causes of CN III palsy

Answer 1

Central

1. Vascular (brainstem infarct)
2. SOL
3. Demyelination (rare)

Peripheral

1. Compressive lesion
   - aneurysm at PCA
   - tumour causing raised ICP
   - basal meningitis
2. Infarction
   - diabetes
3. Trauma
4. Cavernous sinus lesion

Question 2

3 features of CN III palsy

Answer 2

• ptosis
• eye down and out/divergent strabismus
• pupillary dilatation
• Unreactive to direct light reflex, but reactive to indirect light reflex

Question 3

3 causes of horizontal nystagmus

Answer 3

1. Vestibular (if chronic, fast component towards lesion)
2. Cerebellar (towards lesion)
3. INO

Question 4

5 causes of monocular diplopia

Answer 4

1. Astigmatism
2. Myopia
3. Dislocated lens
4. Cataract
5. Hysteria