1. Department of Human Anatomy, Basic Medical College, Ningxia Medical University, Yinchuan, Ningxia Hui Autonomous Region 750006, P.R. China
2. The Second Affiliated Hospital of Xi'an Medical University Xi'an, Shaanxi 710038, P.R. China
3. Department of Neurology, The People's Hospital, Yinchuan, Ningxia Hui Autonomous Region 750006, P.R. China