1. Department of Neurosurgery, Inha University School of Medicine, Incheon, Korea.
2. Department of Neurosurgery, Cheju Halla General Hospital, Jeju, Korea.
3. Department of Neurosurgery, Seoul St. Mary's Hospital, The Catholic University of Korea, Seoul, Korea.
4. Department of Radiology, Seoul St. Mary's Hospital, The Catholic University of Korea, Seoul, Korea.