1. Department of Neurosurgery, University of California, San Francisco, and Parkinson's Disease Research, Education, and Care Center at the San Francisco Veteran's Affairs Medical Center, San Francisco, California
2. Department of Neurosurgery, University of California, San Francisco, San Francisco, California
3. Parkinson's Disease Research, Education, and Care Center at the San Francisco Veteran's Affairs Medical Center, San Francisco, California
4. Department of Neurosurgery, Emory University School of Medicine, Atlanta, Georgia