1. Department of Neurology, Konkuk University Medical Center, Konkuk University School of Medicine, Seoul, South Korea
2. Parkinson Disease Study Group, Seoul National University Hospital, Seoul, South Korea
3. Department of Neurology and Movement Disorder Center, College of Medicine, Seoul National University, Seoul, South Korea
4. Department of Neurology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea