1 Department of Neurology, The Second Xiangya Hospital of Central South University, 139 Middle Renmin Road, Changsha, 410011 Hunan, P. R. China.
2 Department of Neurology, The Second Xiangya Hospital of Central South University, 139 Middle Renmin Road, Changsha, 410011 Hunan, P. R. China. Electronic address: yangli762@gmail.com.
3 Department of Radiology, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania.