C M Chen1, X G Yu2, S Wang3. 1. Department of Neurosurgery, Fujian Medical University Union Hospital, Fuzhou 350001, China. 2. Department of Neurosurgery, the 1th Medical Center of Chinese PLA General Hospital, Beijing 100853, China. 3. Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100070, China.