1. Institute of Basic Medical Sciences, National Cheng Kung University, Tainan 701, Taiwan
2. Division of Neurosurgery, Department of Surgery, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung 833, Taiwan
3. School of Medicine, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan
4. Division of Neurosurgery, Department of Surgery, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung 807, Taiwan
5. Department of Neurology, Kaohsiung Chang Gung Memorial Hospital, College of Medicine, Chang Gung University, Kaohsiung 333, Taiwan
6. Department of Surgery, School of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan
7. Department of Neurosurgery, University of Virginia, Charlottesville, VA 22904, USA
8. Department of Physiology, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan
9. Cheng-Hsing Campus, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan