1. Anesthesia and Surgery Center, Chengdu Shang Jin Nan Fu Branch of West China Hospital, Sichuan University, Chengdu, Sichuan, P. R. China
2. Department of Neurosurgery, West China Hospital, Sichuan University, Chengdu, Sichuan, P. R. China
3. Institute of Neuroscience, Third Affiliated Hospital, Zhengzhou University, Zhengzhou, P. R. China.