1. Department of Otorhinolaryngology, Head and Neck Surgery, Technical University of Munich, 80333 Munich, Germany
2. Department of Otorhinolaryngology, Head and Neck Surgery, Faculty of Medicine, University of Innsbruck, 6020 Innsbruck, Austria
3. Department of Otorhinolaryngology, Head and Neck Surgery, Faculty of Medicine, University of Freiburg, 79085 Freiburg im Breisgau, Germany