[1] Univ Southern Calif, Dept Neurol Surg, Los Angeles, CA 90007 USA
[2] Univ Southern Calif, Dept Preventat Med, Los Angeles, CA 90007 USA
[3] Univ Southern Calif, Keck Sch Med, Los Angeles, CA 90007 USA
[4] Childrens Hosp Los Angeles, Dept Surg, Div Neurol Surg, Los Angeles, CA 90027 USA
[5] Univ Calif San Francisco, Dept Neurol Surg, San Francisco, CA USA