[1] Tsukuba Univ Hosp, Mito Kyodo Gen Hosp, Dept Neurol, Mito Area Med Educ Ctr, 3-2-7 Miyamachi, Mito, Ibaraki 3100015, Japan
[2] Tsukuba Univ Hosp, Mito Kyodo Gen Hosp, Dept Neurosurg, Mito Area Med Educ Ctr, Ibaraki, Japan
[3] Tsukuba Med Ctr Hosp, Dept Radiol, Ibaraki, Japan
[4] Tsukuba Med Ctr Hosp, Dept Neurosurg, Ibaraki, Japan
[5] Tsukuba Mem Hosp, Dept Radiol, Ibaraki, Japan
[6] Tsukuba Univ Hosp, Mito Kyodo Gen Hosp, Dept Gen Internal Med, Mito Area Med Educ Ctr, Ibaraki, Japan
[7] Tsukuba Univ Hosp, Mito Kyodo Gen Hosp, Dept Radiol, Mito Area Med Educ Ctr, Ibaraki, Japan
[8] Univ Tsukuba, Dept Neurol, Facil Med, Ibaraki, Japan