1. Department of Neurology, Ewha Womans University School of Medicine, Ewha Womans University Mokdong Hospital, Seoul, Korea.
2. Department of Neurology, Soonchunhyang University School of Medicine, Soonchunhyang University Bucheon Hospital, Bucheon, Korea.
3. Department of Neurology, Ajou University School of Medicine, Ajou University Hospital, Suwon, Korea.
4. Department of Occupational and Environmental Medicine, Ewha Womans University School of Medicine, Ewha Womans University Mokdong Hospital, Seoul, Korea.