[1] Shinshu Univ, Dept Otorhinolaryngol, Sch Med, 3-1-1 Asahi, Matsumoto, Nagano 3908621, Japan
[2] Keio Univ, Sch Med, Dept Otorhinolaryngol Head & Neck Surg, Tokyo, Japan
[3] Kitasato Univ, Sch Med, Dept Otolaryngol, Sagamihara, Kanagawa 228, Japan
[4] Tokyo Metropolitan Geriatr Hosp, Dept Otolaryngol, Itabashi Ku, Tokyo 173, Japan
[5] Ehime Univ, Dept Otolaryngol, Sch Med, Shigenobu Cho, Toon City, Ehime, Japan
[6] Iwate Med Univ, Dept Otorhinolaryngol, Morioka, Iwate 020, Japan
[7] Nagoya Univ, Grad Sch Med, Dept Otorhinolaryngol, Showa Ku, Nagoya, Aichi 4648601, Japan
[8] Hokkaido Univ, Grad Sch Med, Dept Otolaryngol Head & Neck Surg, Kita Ku, Sapporo, Hokkaido, Japan
[9] Okayama Univ, Grad Sch Med Dent & Pharm, Dept Otolaryngol Head & Neck Surg, Okayama, Japan
[10] Univ Tsukuba, Fac Med, Dept Otolaryngol, Tsukuba, Ibaraki, Japan
[11] Univ Tokyo, Fac Med, Dept Otolaryngol, Bunkyo Ku, Tokyo 113, Japan