1. Department of Neurosurgery, Iwate Medical University, Morioka;
2. Department of Neurosurgery, Kobe City General Hospital;
3. Department of Neurosurgery, Asahikawa Red Cross Hospital, Asahikawa;
4. Department of Neurosurgery, Hyogo Emergency Medical Center/Kobe Red Cross Hospital, Kobe;
5. Department of Neurosurgery, National Cardiovascular Center;
6. Cerebrovascular Division, Department of Medicine, National Cardiovascular Center, Osaka; and
7. Department of Neurosurgery, Nagasaki University School of Medicine, Nagasaki, Japan