Jin-Sun Jun1, Ryul Kim2, Hye-Min Jung2, Jung-Ick Byun3, Jin Myoung Seok4, Tae-Joon Kim5, Jung-Ah Lim6, Jun-Sang Sunwoo7, Han-Joon Kim2, Carlos H Schenck8, Kwang Ik Yang4, Ki-Young Jung2. 1. Department of Neurology, Kangnam Sacred Heart Hospital, Hallym University College of Medicine, Seoul, Republic of Korea. 2. Department of Neurology, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Republic of Korea. 3. Department of Neurology, Kyung Hee University Hospital at Gangdong, Kyung Hee University School of Medicine, Seoul, Republic of Korea. 4. Department of Neurology, Soonchunhyang University College of Medicine, Soonchunhyang University Cheonan Hospital, Cheonan, Republic of Korea. 5. Department of Neurology, Ajou University School of Medicine, Suwon, Republic of Korea. 6. Department of Neurology, Chamjoeun Hospital, Gwangju, Republic of Korea. 7. Department of Neurosurgery, Seoul National University Hospital, Seoul, Republic of Korea. 8. Minnesota Regional Sleep Disorders Center, and Department of Psychiatry, Hennepin County Medical Center and University of Minnesota Medical School, Minneapolis, MN.