[1] Beijing Univ Chinese Med Subsidiary, Dongfang Hosp, Dept Neurol, Beijing, Peoples R China
[2] Tsinghua Univ, Dept Math Sci, Beijing 100084, Peoples R China
[3] Univ Calif Los Angeles, Stroke Ctr, Los Angeles, CA USA
[4] Univ Calif Los Angeles, David Geffen Sch Med, Dept Neurol, Los Angeles, CA 90095 USA