1. Department of Neurosurgery, College of Medicine, Chung-Ang University, Seoul, Korea.
2. Department of Neurosurgery, College of Medicine, Chung-Ang University Hospital, Seoul, Korea.
3. Department of Neurosurgery, Gyeongsang National University School of Medicine, Gyeongsang National University Hospital, Jinju, Korea.
4. Department of Neurosurgery, College of Medicine, Chung-Ang University Gwangmyeong Hospital, Seoul, Korea.