1. Department of Neurosurgery, The First Hospital of Shanxi Medical University, Taiyuan, Shanxi 030001, P.R. China
2. Department of Immunology, Shanxi Provincial Cancer Hospital, Taiyuan, Shanxi 030013, P.R. China
3. Department of Neurosurgery, People's Hospital of Zhengzhou, Zhengzhou, Henan 450053, P.R. China
4. Department of Neurosurgery, The Fifth People's Hospital of Datong, Datong, Shanxi 037006, P.R. China