1. Department of Otorhinolaryngology, Head and Neck Surgery, University of Miyazaki, Miyazaki 889-2155, Japan
2. Department of Otorhinolaryngology, Head and Neck Surgery, The Jikei University School of Medicine, Minato-ku 105-8461, Japan
3. Miyazaki University Hospital Hearing Care Center, Miyazaki 889-1601, Japan
4. Department of Otorhinolaryngology, Head and Neck Surgery, International University of Health and Welfare Narita Hospital, Narita 286-0124, Japan
5. Department of Otorhinolaryngology, Head and Neck Surgery, University of Ryukyus, Nakagami-gun 903-0125, Japan
6. Department of Otorhinolaryngology, Head and Neck Surgery, International University of Health and Welfare Hospital, Nasushiobara 329-2763, Japan