1. Department of Neurosurgery, Graduate School of Medicine, University of the Ryukyus, Nakagami-gun, Japan
2. Department of Otorhinolaryngology, Head and Neck Surgery, Graduate School of Medicine, University of Miyazaki, Miyazaki-gun, Japan
3. Department of Otorhinolaryngology, Head and Neck Surgery, Graduate School of Medicine, University of the Ryukyus, Nakagami-gun, Japan