1. Department of Neurology, Chungnam National University Sejong Hospital, Sejong, Korea.
2. Department of Neurology, Chungnam National University Hospital, Chungnam National University College of Medicine, Daejeon, Korea.
3. Department of Neurology, Kyung Hee University Hospital, Seoul, Korea.
4. Department of Neurology, MRC and Movement Disorder Center, Seoul National University Hospital, Parkinson Study Group, Seoul National University College of Medicine, Seoul, Korea.