Clinical presentation

A 51-year-old man presented with a 1-year history of gait imbalance and difficulties in the execution of fine movements. On examination, he had hypomimia, bilateral and symmetrical bradykinesia and rigidity (unified Parkinson’s disease rating scale (UPDRS) =17). He had no tremor, impairment of eye movement and cerebellar or pyramidal signs.

MR scan of brain found a giant inter-hemispheric arachnoid cyst, exerting a moderate mass effect on the basal ganglia bilaterally (figure …