[1] Univ Calif San Francisco, Dept Neurol, San Francisco, CA 94143 USA
[2] Weill Cornell Med Coll, Dept Neurol & Neurosci, New York, NY USA
[3] Calif Pacific Med Ctr, San Francisco, CA USA
[4] Univ Calif San Francisco, Dept Emergency Med, San Francisco, CA 94143 USA
[5] Univ Calif San Francisco, Dept Epidemiol & Biostat, San Francisco, CA 94143 USA