1. Research Unit of Logopedics, University of Oulu, Oulu, Finland
2. Department of Otorhinolaryngology–Head and Neck Surgery, Turku University Hospital, Turku, Finland
3. Department of Otorhinolaryngology–Head and Neck Surgery, Oulu University Hospital, Oulu, Finland
4. Department of Otorhinolaryngology–Head and Neck Surgery, Kuopio University Hospital, Kuopio, Finland
5. Department of Otorhinolaryngology–Head and Neck Surgery, Tampere University Hospital, Tampere, Finland
6. Department of Otorhinolaryngology–Head and Neck Surgery, Helsinki University Hospital, Helsinki, Finland
7. Department of Otorhinolaryngology, University of Helsinki, Helsinki, Finland
8. Clinical Medicine Research Unit, University of Oulu, Oulu, Finland
9. Department of Otorhinolaryngology, Institute of Clinical Medicine, University of Eastern Finland, Kuopio, Finland