[1] Ajou Univ, Dept Otolaryngol, Sch Med, 164 Worldcup Ro, Suwon 16499, Gyeonggi Do, South Korea
[2] Seoul Natl Univ, Coll Med, Dept Otorhinolaryngol Head & Neck Surg, Seoul, South Korea
[3] Catholic Univ Korea, Seoul St Marys Hosp, Coll Med, Dept Otorhinolaryngol Head & Neck Surg, Seoul, South Korea
[4] Chonnam Natl Univ, Chonnam Natl Univ Hosp, Sch Med, Dept Otolaryngol Head & Neck Surg, Gwangju, South Korea
[5] Yonsei Univ, Coll Med, Dept Otorhinolaryngol, Seoul, South Korea
[6] Soonchunhyang Univ, Coll Med, Seoul Hosp, Dept Otorhinolaryngol Head & Neck Surg, Seoul, South Korea
[7] Pusan Natl Univ, Yangsan Hosp, Dept Otorhinolaryngol Head & Neck Surg, Coll Med, Yangsan, South Korea
[8] Sungkyunkwan Univ, Samsung Med Ctr, Dept Otorhinolaryngol Head & Neck Surg, Sch Med, Seoul, South Korea
[9] Dankook Univ, Dept Otolaryngol Head & Neck Surg, Coll Med, Cheonan, South Korea
[10] Kyungpook Natl Univ, Sch Med, Dept Otorhinolaryngol Head & Neck Surg, Daegu, South Korea
[11] Catholic Univ Korea, Bucheon St Marys Hosp, Coll Med, Dept Otorhinolaryngol Head & Neck Surg, Bucheon, South Korea
[12] Tntn Hosp, Dept Otolaryngol, Hwasung, South Korea
[13] Univ Ulsan, Asan Med Ctr, Dept Otorhinolaryngol Head & Neck Surg, Coll Med, Seoul, South Korea
[14] Seoul Natl Univ, Bundang Hosp, Dept Otorhinolaryngol Head & Neck Surg, Seongnam, South Korea
[15] Konyang Univ, Dept Otorhinolaryngol Head & Neck Surg, Coll Med, Daejeon, South Korea