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