1. Department of Neurosurgery, Ajou University School of Medicine, Suwon, Korea.
2. Department of Neurosurgery, Keimyung University School of Medicine, Dongsan Medical Center, Daegu, Korea.
3. Department of Neurosurgery, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.
4. Department of Neurosurgery, Seoul St. Mary's Hospital, The Catholic University of Korea, Seoul, Korea.