1 Division of Neurology, Department of Medicine, Jichi Medical University School of Medicine, 3311-1 Yakushiji, Shimotsuke, Tochigi, 329-0498, Japan. r1821sk@jichi.ac.jp.
2 Division of Neurology, Department of Medicine, Jichi Medical University School of Medicine, 3311-1 Yakushiji, Shimotsuke, Tochigi, 329-0498, Japan.
3 Division of Hematology, Department of Medicine, Jichi Medical University, Tochigi, Japan.
4 Department of Pathology, Faculty of Medicine, University of Tsukuba, Ibaraki, Japan.