Long Wang1, Xiang'en Shi2, Hai Qian3. 1. Department of Neurosurgery, Fu Xing Hospital, Capital Medical University, Beijing, China. 2. Department of Neurosurgery, Fu Xing Hospital, Capital Medical University, Beijing, China; Department of Neurosurgery, SanBo Brain Hospital, Capital Medical University, Beijing, China. Electronic address: shixen@sina.com. 3. Department of Neurosurgery, SanBo Brain Hospital, Capital Medical University, Beijing, China.