1. Department of Neurosurgery, Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, P.R. China
2. Department of Neurology, Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan 646000, P.R. China
3. Department of Neurosurgery, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA
4. Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA