1. Department of Neurosurgery, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.
2. Severance Institute of Vascular and Metabolic Research, Yonsei University College of Medicine, Seoul, Korea.
3. Department of Neurosurgery, Konkuk University Hospital, Cheongju, Korea.
4. Department of Neurosurgery, Kangwon National University Hospital, Gangwon, Korea.