1. Division of Otorhinolaryngology, Sendai Municipal Hospital, Sendai, Japan.
2. Medical Education Center, Aichi Medical University School of Medicine, Nagakute, Japan.
3. Department of Otolaryngology-Head and Neck Surgery, Tohoku University Graduate School of Medicine, Sendai, Japan.
4. Department of Anatomy, Chonbuk National University College of Medicine, Jeonju, Korea.
5. Department of Anatomy, Tokyo Dental College, Chiba, Japan.
6. Division of Internal Medicine, Iwamizawa Kojin-kai Hospital, Iwamizawa, Japan.