1. Department of Neurosurgery, Chuncheon Sacred Heart Hospital, Hallym University, Chuncheon, Gangwon, Korea.
2. Department of Neurosurgery, Seoul National University Bundang Hospital, Seongnam, Korea.
3. Department of Neurosurgery, Soonchunhyang University Hospital, Seoul, Korea.
4. Department of Neurosurgery, Seoul National University Hospital, Seoul, Korea.