1. Department of Neurosurgery, Gachon University Gil Medical Center, Incheon, Korea.
2. Department of Neurosurgery, Chungnam National University Hospital, Daejeon, Korea.
3. Department of Neurosurgery, Soonchunhyang University Seoul Hospital, Seoul, Korea.
4. Department of Neurosurgery, Pusan National University Hospital, Busan, Korea.
5. Department of Neurosurgery, Seoul National University College of Medicine, Seoul, Korea.
6. Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University College of Medicine, Seoul, Korea.
7. Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.