1. Department of Neurosurgery, College of Medicine, Seoul National University, Seoul, Korea
2. Department of Neurosurgery, Seoul National University Hospital, Seoul, Korea
3. Department of Neurosurgery, College of Medicine, Inje University, Ilsan Paik Hospital, Goyang, Korea
4. Department of Neurosurgery, Inje University Ilsan Paik Hospital, Goyang, Korea