1. Department of Neurosurgery, Tangdu Hospital, The Fourth Military Medical University, Xi'an, Shaanxi, China.
2. Department of Neurosurgery, The Second Affiliated Hospital of Shaanxi University of Chinese Medicine, Xi'an, China.
3. Department of Anesthesiology, Tangdu Hospital, The Fourth Military Medical University, Xi'an, Shaanxi, China.
4. Department of Health Statistics, The Fourth Military Medical University, Xi'an, Shaanxi, China.
5. Time and Frequency Measurement Department, National Time Service Center, Chinese Academy of Sciences, Xi'an, Shaanxi, China.
6. Department of Neurosurgery, Xijing Hospital, The Fourth Military Medical University, Xi'an, Shaanxi, China.