1. Department of Otolaryngology, Japanese Red Cross Society Himeji Hospital, Himeji City, Hyogo, Japan;
2. Departments of Otolaryngology Head and Neck Surgery, Okayama University Graduate School of Medicine, Okayama City, Okayama, Japan;
3. Department of Otolaryngology Head and Neck Surgery, Kumamoto University Graduate School of Medicine, Kumamoto City, Kumamoto, Japan;
4. Nakada ENT Clinic, Himeji City, Hyogo, Japan;
5. Department of Pathology, Dentistry and Pharmaceutical Sciences, Okayama University Graduate School of Medicine, Okayama City, Okayama, Japan