1. Department of Neurology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
2. Department of Neurology, Seoul Metropolitan Goverment Boramae Medical Center, Seoul National University College of Medicine, Seoul, Korea.
3. Department of Neurology, Clinical Research Institute, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea.
4. Department of Clinical Epidemiology and Biostatistics, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.