[1] Univ Calif San Francisco, Dept Neurol, San Francisco, CA 94143 USA
[2] Columbia Univ Coll Phys & Surg, Dept Neurol, New York, NY 10032 USA
[3] Columbia Univ Coll Phys & Surg, Dept Epidemiol, New York, NY 10032 USA
[4] Mailman Sch Publ Hlth, New York, NY USA
[5] Univ Calif San Francisco, Dept Radiol, San Francisco, CA 94143 USA
[6] Univ Calif San Francisco, Dept Pediat, San Francisco, CA 94143 USA
[7] Dept Publ Hlth, Oakland, CA USA
[8] Univ Calif San Francisco, Dept Biostat & Epidemiol, San Francisco, CA 94143 USA
[9] Univ Virginia, Dept Radiol, Charlottesville, VA USA
[10] Hosp Sick Children, Dept Neurol, Toronto, ON M5G 1X8, Canada