1. Department of Neurosurgery, Chung-Ang University Hospital, Chung-Ang University College of Medicine, Seoul, Republic of Korea;
2. Department of Neurosurgery, Hallym University Medical Center, Hallym University College of Medicine, Anyang-si, Gyeonggi-do, Republic of Korea; and
3. Department of Neurosurgery, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Republic of Korea