1 Department of Neurology, West China Hospital, Sichuan University, 37 Guo Xue Xiang, Chengdu, China 610041.
2 Department of Neurology, West China Hospital, Sichuan University, 37 Guo Xue Xiang, Chengdu, China 610041; Center of Cerebrovascular Diseases, West China Hospital, Sichuan University, 37 Guo Xue Xiang, Chengdu, China 610041; State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, 37 Guo Xue Xiang, Chengdu, China 610041. Electronic address: wyplmh@hotmail.com.