1. Department of Neurosurgery, Graduate School of Medical Sciences, Kyushu University
2. Clinical Research Center, National Hospital Organization, Nagoya Medical Center
3. Department of Preventive Medicine and Epidemiologic Informatics, National Cerebral and Cardiovascular Center
4. Department of Neurosurgery, National Kyushu Medical Center
5. Department of Neurosurgery, Kitakyushu Municipal Medical Center