1. Department of Neurology, College of Medicine, Ewha Woman's University, Seoul, Korea.
2. Department of Neurology, College of Medicine, Korea University Guro Hospital, Seoul, Korea.
3. Department of Neurology, CHA Bundang Medical Center, CHA University, Seongnam, Korea.
4. Department of Biostatistics, Ewha Institute of Convergency Medicine, Seoul, Korea.