1. Department of Neurosurgery, Seoul National University Bundang Hospital, Seongnam, Korea.
2. Department of Neurosurgery, Seoul National University College of Medicine, Seoul, Korea.
3. Department of Neurosurgery, Seoul National University Hospital, Seoul, Korea.
4. Department of Neurosurgery, Jeju University Hospital, Jeju, Korea.
5. Department of Neurosurgery, Seoul National University Boramae Hospital, Seoul, Korea.