1. Department of Otolaryngology, Head and Neck Surgery Tokyo Medical University Shinjuku‐ku Japan
2. Department of Clinical Oncology Tokyo Medical University Ibaraki Medical Center Inashiki‐gun Japan
3. Department of Otorhinolaryngology Yokohama Asahi Chuo General Hospital Yokohama‐shi Japan
4. Department of Hearing Implant Sciences Shinshu University School of Medicine Matsumoto‐shi Japan
5. Department of Otorhinolaryngology Shinshu University School of Medicine Matsumoto‐shi Japan