1. Department of Otolaryngology-Head & Neck Surgery, Kagawa Rosai Hospital, Marugame, Japan
2. Department of Otolaryngology-Head & Neck Surgery, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan
3. Department of Otolaryngology, International University of Health and Welfare School of Medicine, Narita, Japan
4. Department of Otolaryngology-Head and Neck Surgery, Kochi Health Sciences Center, Kochi, Japan