1. Department of Neurosurgery, Tianjin Huanhu Hospital, Tianjin 300050, P.R. China
2. English Department, International Medical School, Tianjin Medical University, Tianjin 300070, P.R. China
3. Department of Physiology, Tianjin Medical University, Tianjin 300070, P.R. China
4. Department of Neurosurgery, Hebei United University, Tangshan, Hebei 063000, P.R. China