Effects of bilateral subthalamic stimulation on cognitive function in Parkinson disease

Background: Chronic bilateral subthalamic deep brain stimulation (STN-DBS) is known to improve motor function in patients with Parkinson disease (PD). However, the possible effects of STN-DBS on neuropsychological functions have been studied less. Objective: To investigate the effects of STN-DBS on neuropsychological functions in PD. Design: Before-after trial. Patients and Methods: Fifteen consecutive patients were assessed before and 3 months after implantation of stimulators for STN-DBS (postsurgical assessment with the stimulators switched on). Both assessments were performed with patients in a drug-free condition. The neuropsychological battery consisted of tests measuring memory and visuospatial and frontal functions. Results: The comparison between presurgical and postsurgical performance showed a moderate deterioration in verbal memory and prefrontal and visuospatial functions, and a moderate improvement in a prefrontal task and obsessive-compulsive traits. The motor state improved in all patients. Conclusion: Therapy with STN-DBS improves motor symptoms in PD without any clinically relevant neuropsychological deterioration.