[1] Univ Calif San Francisco, Dept Neurol Surg, 505 Parnassus Ave,M779, San Francisco, CA 94143 USA
[2] Univ Calif San Francisco, Eli & Edythe Broad Ctr Regenerat Med & Stem Cell, San Francisco, CA 94143 USA
[3] Univ Calif San Francisco, Vet Affairs Med Ctr, San Francisco, CA 94143 USA
[4] Indiana Univ Sch Med, Dept Neurol Surg, Indianapolis, IN 46202 USA
[5] Goodman Campbell Brain & Spine, Indianapolis, IN USA