Evidence of improved immediate verbal memory and diminished category fluency following STN-DBS in Chinese-Cantonese patients with idiopathic Parkinson's disease.

The present study investigated the neuropsychological effects of bilateral deep brain stimulation (DBS) on subthalamic nucleus (STN) in Chinese-Cantonese patients with idiopathic Parkinson's disease (PD). Twenty-seven patients were prospectively recruited from the Movement Disorder Clinic at the Hong Kong Prince of Wales Hospital. Neuropsychological evaluations were performed at baseline, 6 and 12 months following the DBS procedure. Assessment battery included standardized tests on global cognitive function, verbal memory, non-verbal memory, confrontation naming, visuospatial organization, attention and executive functions. Anxiety and depressive symptoms were measured by two self-reported questionnaires. Results demonstrated diminished performance on a category fluency task that occurred at 6 months post-operatively and persisted at 12-month re-evaluation; 29.6-33.3 % of patients showed reduction of more than 1 SD (standard deviation) at post-operative measure. Conversely, performance on an immediate recall task in a verbal memory test was found to improve significantly at the same time point and persisted through 12 months after surgery; 22.2-25.9 % showed an improvement (≥1 SD). Psychologically, anxiety symptoms were statistically decreased and the significant reduction occurred at 12 months after surgery. Patients who reported a moderate to severe level of anxiety reduced from 51.9 to 18.5 %. Our findings concurred with most evidences on the effects of STN-DBS on verbal fluency; on the other hand, we demonstrated improvement of immediate verbal memory that warranted further investigation.