1. Department of Neurology, Kyung Hee University Hospital at Gangdong, Kyung Hee University College of Medicine, Seoul, Korea.
2. Department of Neurology, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea.
3. Department of Neuropsychiatry, Seoul National University Hospital, Seoul, Korea.
4. Department of Neurology, Seoul National University Bundang Hospital, Seongnam, Korea.
5. Department of Neurology, Kangbuk Samsung Hospital, Seoul, Korea.
6. Department of Neurology, CHA University, CHA Bundang Medical Center, Seongnam, Korea.
7. Department of Neurology, Ajou University School of Medicine, Suwon, Korea.
8. Department of Neurology, Kangnam Sacred Heart Hospital, Hallym University College of Medicine, Seoul, Korea.
9. Minnesota Regional Sleep Disorders Center, and Department of Psychiatry, Hennepin County Medical Center and University of Minnesota Medical School, Minneapolis, MN, USA.