1. Department of Neurology, Okayama University Medical School, Okayama, Japan
2. Department of Neurology, Tokai University School of Medicine, Isehara, Japan
3. Department of Neurosurgery, Hokkaido University Graduate School of Medicine, Sapporo, Japan
4. Department of Neurosurgery, Yamanashi University Medical School, Kofu, Japan
5. Department of Neurosurgery, Graduate School of Medicine, Yokohama City University, Yokomaha, Japan