1. Department of Surgery, Faculty of Medicine, School of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan
2. Division of Neurosurgery, Department of Surgery, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan
3. Department of Surgery, Kaohsiung Municipal Ta Tung Hospital, Kaohsiung, Taiwan
4. Department of Surgery, Kaohsiung Municipal Hsiao Kang Hospital, Kaohsiung, Taiwan