1. Department of Neurology, Yonsei University College of Medicine, Seoul, Korea.
2. Rehabilitation Institute of Neuromuscular Disease, Yonsei University College of Medicine, Seoul, Korea.
3. Department of Neurology, Mokdong Hospital, Ewha Womans University School of Medicine, Seoul, Korea.
4. Department of Pathology, Yonsei University College of Medicine, Seoul, Korea.