1. Department of Neurosurgery, St. Vincent’s Hospital, The Catholic University of Korea, Suwon;
2. Department of Neurosurgery, Incheon St. Mary’s Hospital, The Catholic University of Korea, Incheon;
3. Department of Neurosurgery, Kangneung Asan Hospital, The Ulsan University, Kangneung;
4. Department of Neurosurgery, Chungbuk National University of Korea, Suwon; and
5. Department of Neurosurgery, Eunpyeong St. Mary’s Hospital, The Catholic University of Korea, Seoul, Korea