67 out of 91
Vertical nystagmus (AIPG 2010)
|A||occurs in phenytoin toxicity|
|B||in an unconscious patient suggests thalamic lesion|
|C||if upbeating indicates cerebellar tonsillar ectopia|
|D||if downbeating indicates a lesion in the pons|
Ans. A occurs in phenytoin toxicity
Thalamic lesion in an unconscious patient usually presents with downward deviation of the eyes. Arnold-Chiari's syndrome may present with down beating nystagmus.