1. Department of Neurosurgery, Cerebrovascular Center, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.
2. Severance Institute for Vascular and Metabolic Research, Yonsei University College of Medicine, Seoul, Korea.
3. Department of Radiology, Cerebrovascular Center, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.