1. Department of Otolaryngology, Jikei University School of Medicine, Minato-ku, Tokyo, Japan
2. Department of Otolaryngology, Dokkyo Medical University Saitama Medical Center, Koshigaya-shi, Saitama, Japan
3. Department of Otolaryngology, Tohoku Kosai Hospital, Sendai-shi, Miyagi, Japan
4. Department of Otolaryngology, Asahi General Hospital, Asahi-shi, Chiba, Japan