1 Department of Otorhinolaryngology and Head and Neck Surgery, 1st Faculty of Medicine, University Hospital Motol, V Uvalu 84, 150 06 Prague 5, Czech Republic.
2 Department of Otorhinolaryngology and Head and Neck Surgery, University Hospital Mannheim, Theodor-Kutzer-Ufer 1-3, 68167 Mannheim, Germany.
3 Department of Otorhinolaryngology and Head and Neck Surgery, University of Barcelona Medical School, Carrer Villarroel 170, 08036 Barcelona, Spain.