1. Department of Neurosurgery, Spine and Spinal Cord Institute, Gangnam Severance Spine Hospital, Yonsei University College of Medicine, Seoul, Korea.
2. Department of Neurosurgery, 21 Century Hospital, Ansan, Korea.
3. Department of Radiology, Dong-A University Medical Center, Busan, Korea.
4. Department of Neurosurgery, The Armed Forces Capital Hospital, Seongnam, Korea.