[1] Univ Groningen, Univ Med Ctr Groningen, Dept Otorhinolaryngol Head & Neck Surg, NL-9700 RB Groningen, Netherlands
[2] Helsinki Univ Hosp, Dept Otorhinolaryngol Head & Neck Surg, Helsinki, Finland
[3] Univ Groningen, Univ Med Ctr Groningen, Dept Epidemiol, NL-9700 RB Groningen, Netherlands
[4] Reg Hosp Viborg, Ear Nose Throat Dept, Viborg, Denmark
[5] Maastricht Univ, Med Ctr, Dept Otorhinolaryngol Head & Neck Surg, Maastricht, Netherlands
[6] Univ Med & Pharm, Cluj Napoca Emergency Cty Hosp, ENT Dept, Cluj Napoca, Romania
[7] Univ Leipzig, Dept Otorhinolaryngol, D-04109 Leipzig, Germany
[8] Hosp Gral de Catalunya St Cugat del Valles, Dept Otorhinolaryngol, Barcelona, Spain
[9] Med Univ Graz, Dept Otorhinolaryngol, Graz, Austria
[10] Erasmus Univ, Dept Otorhinolaryngol Head & Neck Surg, Rotterdam, Netherlands
[11] Greater Poland Canc Ctr, Dept Otorhinolaryngol, Poznan, Poland
[12] Univ Athens, Hippocrate Gen Hosp, Dept Otorhinolaryngol 1, Athens, Greece
[13] Poznan Univ Med Sci, Dept Otolaryngol, Poznan, Poland
[14] Katharinen Hosp, Klinikum Stuttgart, Dept Otorhinolaryngol Head & Neck Surg, D-70174 Stuttgart, Germany
[15] Univ Hosp Louvain Mt Godinne, Dept Otorhinolaryngol, Yvoir, Belgium
[16] Med Univ Innsbruck, Dept Hearing Speech & Voice Disorders, A-6020 Innsbruck, Austria