MRCP2-3299

A 25-year-old man is brought to the Emergency Department by his friends as they have noticed him acting strangely over the last 6 months. His friends are particularly concerned about his excessive drinking and going out without informing them. They have also noticed his walking has become progressively more unsteady and he often slurs his speech. His mother has a history of depression and his father has a history of seizures.

On examination, he has coarse nystagmus to lateral gaze bilaterally, slurred speech, and an ataxic gait. The rest of his neurological examination is normal.

What is the most likely diagnosis?