1. Department of Neurosurgery, Kohnan Hospital, Sendai, Japan
2. Division of Advanced Cerebrovascular Surgery, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
3. Department of Neurosurgery, Tohoku Medical and Pharmaceutical University Hospital, Sendai, Japan
4. Department of Neuroendovascular Therapy, Kohnan Hospital, Sendai, Japan; and
5. Department of Neurosurgery, Tohoku University Graduate School of Medicine, Sendai, Japan