1. Department of Neurosurgery, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, P.R. China
2. Department of Neurosurgery, Xi'an Gaoxin Hospital, Xi'an, Shaanxi 710061, P.R. China
3. Department of Neurosurgery, Chongqing University Cancer Hospital, Chongqing 400030, P.R. China