1. Department of Neurology and Neurological Sciences, Stanford University, Palo Alto, CA, USA
2. Department of Neurosurgery, Stanford University, Palo Alto, CA, USA
3. Palo Alto Veterans Affairs Health Care System, Palo Alto, CA, USA
4. Department of Veterans Affairs Medical Center, San Francisco, CA, USA
5. Department of Neurology, University of California, San Francisco, CA, USA