[1] Virginia Commonwealth Univ, Dept Neurosurg, Richmond, VA 23298 USA
[2] Virginia Commonwealth Univ, Dept Neurosurg Parkinsons Dis Res, Richmond, VA 23298 USA
[3] Virginia Commonwealth Univ, McGuire VAMC, Clin Care Ctr, Richmond, VA 23298 USA
[4] Univ Calif San Francisco, Dept Neurol Surg, San Francisco, CA 94143 USA