It is well established that patients with Parkinson’s disease (PD) can develop cognitive, behavioural, and mood changes.¹ Cognitive decline has been reported to be present in up to 84% of patients who survive for 15 years after diagnosis.² Several mechanisms may underlie these clinical problems including cholinergic deficiency, dopaminergic dysfunction, prefrontal-caudate nucleus disconnection, and intrinsic limbic and cortical pathology (Lewy bodies, Alzheimer-like changes). Concerns have been raised about the possibility that subthalamic deep brain stimulation (STN-DBS) could also produce cognitive changes and mood and behavioural alterations.^3,4 We report the clinical and neuropathological features of a patient with advanced PD who developed behavioural changes and dementia while on STN-DBS.

CASE REPORT

A 74 year old man suffering from PD for 11 years presented troublesome dyskinesias and unpredictable motor fluctuations that did not respond to multiple changes in medication. The Hoehn and Yahr stage was IV while “off” and III while “on” medication. The Schwab and England scale score was 40% in the “off” and 80% in the “on” condition. The UPDRS-III score was 56 while “off” and 21 while “on”. No clinically evident signs of cognitive impairment were present. The Mini-Mental State Examination (MMSE) score was 28/30. Neuropsychological assessment was considered to be normal except for …