1. Department of Neurosurgery, Myong Ji St. Mary's Hospital, Seoul, Korea.
2. Department of Neurosurgery, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
3. Department of Neurosurgery, St. Vincent's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
4. Statistics and Actuarial Science, Soongsil University, Seoul, Korea.
5. Department of Biostatistics, College of Medicine, The Catholic University of Korea, Seoul, Korea.
6. Department of Neurosurgery, Cell Death Disease Research Center, St. Vincent's Hospital, College of Medicine, The Catholic University of Korea, Suwon, Korea.