1. Department of Otolaryngology, Head and Neck Surgery, Rechts der Isar Hospital, Technical University Munich, Munich, Germany
2. Department of Otolaryngology, Head and Neck Surgery, University Hospital Jena, Friedrich Schiller University Jena, Jena, Germany
3. Department of Otolaryngology, Head and Neck Surgery, Asklepios Hospital, Bad Toelz, Germany.