1. Department of Neurosurgery, Kohnan Hospital, Taihaku-ku, Sendai, Japan
2. Department of Neuroendovascular Therapy, Kohnan Hospital, Taihaku-ku, Sendai, Japan
3. Department of Neurosurgery, Tohoku University, Aoba, Sendai, Japan
4. Department of Neurosurgery, Graduate School of Medicine, Tohoku University, Aoba, Sendai, Japan