1. Department of Neurosurgery, Hyogo Medical University, Nishinomiya 663-8501, Japan
2. Department of Neurosurgery, Gifu University, Gifu 501-1112, Japan
3. Department of Surgical Pathology, Hyogo Medical University, Nishinomiya 663-8501, Japan
4. Department of Neuroendovascular Surgery, Kameda Medical Center, Kamogawa 296-0041, Japan
5. Department of Medicine, Graduate School of Medical Sciences, Kindai University, Higashiosaka 577-8502, Japan