1. Department of Neurological Surgery, University of California, UCI Medical Center, Orange, United States.
2. Department of Neurosurgery, UC San Diego School of Medicine, La Jolla, United States.
3. Department of Pathology, University of California, UCI Medical Center, Orange, California, United States.
4. Department of Orthopedic Surgery, University of California, UCI Medical Center, Orange, California, United States.