The purpose of this observational study is the long term follow-up of Parkinson's patients who participated in a clinical trial in which they received AAV-GAD gene transfer into the subthalamic nucleus (STN) region of the brain. Patients will be followed once a year for up to five (5) years. The study will monitor and evaluate the long term effects of AAV-GAD and provide long term safety information.
Inclusion Criteria:
Exclusion Criteria: