Data management According to the trial design, a table will be formulated for data collection. Collected data will be input into an electronic database by professional staff using a double-data entry strategy. Information accuracy will be checked when all recruited patients are followed up. The database will be locked by the researcher in charge and will not be altered. All information relating to this trial will be preserved by Department of Neurosurgery, Chinese PLA General Hospital of China. The electronic database will be fully disclosed to a professional statistician for statistical analysis.