Safety Study of Subthalamic Nucleus Gene Therapy for Parkinson's Disease

The purpose of this study is to determine the safety of using a modified virus to transfer a gene called GAD into a region of the brain called the subthalamic nucleus in patients with advanced Parkinson's disease. The overall goal of this approach is to ultimately normalize the flow of information in several brain regions responsible for movement, to ultimately improve function in patients with this disorder. The current study is primarily designed to evaluate the safety of this approach, but patients are also being monitored for possible signs of effectiveness as well.