RENEWED INTEREST in the surgical treatment of Parkinson disease (PD), essential tremor (ET), and other movement disorders has been fueled by an improved understanding of the functional anatomy of the basal ganglia and their connections; refinements of methods and techniques in neurosurgery, neurophysiology, and neuroimaging; and the emergence of complications from chronic medical therapy.1 Because of an increased awareness of surgical options for patients with PD, the attitudes of physicians toward referring patients for surgery have been changing. In one survey, 94.3% of neurologists considered referring their patients with PD for surgery.2