[1] St Anna Hosp, Dept Otorhinolaryngol Head & Neck Surg, D-47259 Duisburg, Germany
[2] Univ Hosp RWTH Aachen, Aachen, Germany
[3] Med Zentrum Kreis Aachen Betriebsteil Bardenberg, Aachen, Germany
[4] Univ Hosp Maastricht, Dept Otorhinolaryngol Head & Neck Surg, Maastricht, Netherlands