[1] Hitoyoshi Med Ctr, Dept Neurosurg, 35 Oigamicho, Hitoyoshi City, Kumamoto 8688555, Japan
[2] Kumamoto Univ, Grad Sch Med Sci, Dept Neurosurg, 1-1-1 Honjo, Kumamoto, Kumamoto 8608556, Japan
[3] Tokuda Neurosurg Hosp, Dept Neursurg, 1-11248-1 Utsuma, Kanoya, Kagoshima 8930011, Japan
[4] Saiseikai Kumamoto Hosp, Dept Neurosurg, 5-3-1 Chikami, Kumamoto, Kumamoto 8614193, Japan
[5] Natl Med Org Kumamoto Med Ctr, Dept Neurosurg, 1-5 Ninomaru, Kumamoto, Kumamoto 8600008, Japan