Yanping Wei1, Hongzhi Guan2. 1. Department of Neurology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shuaifuyuan 1, Dongcheng District, Beijing, 100730, People's Republic of China. yp924@sina.com. 2. Department of Neurology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shuaifuyuan 1, Dongcheng District, Beijing, 100730, People's Republic of China.