1. Otsuka ENT Clinic, Yokohama, Kanagawa, Japan
2. Department of Otorhinolaryngology, Nippon Medical School, Musashikosugi Hospital, Kawasaki, Kanagawa, Japan
3. Department of Otorhinolaryngology, Shin-Yurigaoka General Hospital, Kawasaki, Kanagawa, Japan
4. Department of Otorhinolaryngology and Head and Neck Surgery, Nippon Medical School, Tokyo, Japan