Objective: Although a relatively new technique, bilateral deep brain stimulation (DBS) of the subthalamic nucleus (STN) for the treatment of advanced cases of Parkinson's disease (PD) shows considerable promise. While the benefits of the STN stimulation for the treatment of motor symptoms of PD are well established, some studies have reported negative neuropsychological outcomes, especially in elderly patients. The objective of the present study was to investigate the neuropsychological effects of bilateral STN-DBS in a small sample of elderly patients with PD.
Methods: Six patients with PD (mean age 73.0 +/- 10.45 years) were assessed both before and approximately 6 months after DBS surgery in six neuropsychological domains. These domains included orientation, estimated IQ, attention/working memory, language, memory, and visual-spatial functioning. Additionally, depressive symptoms were assessed using the Geriatric Depression Scale. Daily doses of antiparkinsonian medications, in levodopa equivalents, were also compared pre- and postoperatively.
Results: Antiparkinsonian medications were reduced postoperatively by a mean of 65%, from a mean levodopa equivalent dosage of 987 mg/day to 346 mg/day. Category fluency, a word generation task within the language domain, was the only test in which participants demonstrated a statistically significant decline in performance. Participants demonstrated a mean score decrease of 41% (p < 0.05) in category fluency.
Conclusions: The pathophysiology of the observed deficit remains ill defined. However, despite a small sample size, the study provides further evidence that bilateral STN-DBS in PD patients can be associated with negative neuropsychological outcome in word fluency, especially in elderly patients. Implications regarding patient selection for bilateral STN-DBS and recommendations for future research are further discussed.
Copyright (c) 2007 S. Karger AG, Basel.