1. Department of Neurosurgery, Hallym University Kangnam Sacred Heart Hospital, Hallym University College of Medicine, Seoul, Korea.
2. Department of Neurosurgery, Chung-Ang University Hospital, Chung-Ang University College of Medicine, Seoul, Korea.
3. Department of Neurosurgery, Dongguk University Kyungju Hospital, Dongguk University College of Medicine, Kyungju, Korea.