1. Department of Neurology, Asan Medical Center, College of Medicine, University of Ulsan, Seoul, Korea.
2. Department of Neurology, Chung-Ang University College of Medicine, Seoul, Korea.
3. Department of Neurology, Ulsan University Hospital, College of Medicine, University of Ulsan, Ulsan, Korea.
4. Department of Neurology, Jeonbuk University Hospital, College of Medicine, Jeonbuk University, Jeonju, Korea.
5. Department of Otolaryngology, Asan Medical Center, College of Medicine, University of Ulsan, Seoul, Korea.