1. Department of Neurosurgery, Kangnam St. Peter's Hospital, Seoul, Korea.
2. Department of Neurosurgery, The Catholic University of Korea College of Medicine, Daejeon St. Mary's Hospital, Daejeon, Korea.
3. Department of Neurosurgery, The Catholic University of Korea College of Medicine, Seoul St. Mary's Hospital, Seoul, Korea.
4. Department of Neurosurgery, The Catholic University of Korea College of Medicine, Uijeongbu St. Mary's Hospital, Uijeongbu, Korea.