1. Department of Neurosurgery, Ajou University Hospital, Ajou University School of Medicine, Suwon;
2. Department of Neurosurgery, Severance Hospital, Yonsei University College of Medicine, Seoul;
3. Department of Neurosurgery, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul; and
4. Department of Neurosurgery, Asan Medical Center, Ulsan University School of Medicine, Seoul, Republic of Korea