1. Department of Neurology, Hitachinaka Medical Education and Research Center, University of Tsukuba Hospital, 20-1 Ishikawa-cho, Hitachinaka, Ibaraki 312-0057, Japan
2. Department of Neurology, Hitachi Ltd. Hitachinaka General Hospital, 20-1 Ishikawa-cho, Hitachinaka, Ibaraki 312-0057, Japan