1 Department of Otorhinolaryngology-Head and Neck Surgery, Helsinki University Hospital, University of Helsinki, P.O. Box 263, 00029, Helsinki, Finland. antti.makitie@helsinki.fi.
2 Division of Ear, Nose and Throat Diseases, Department of Clinical Sciences, Intervention and Technology, Karolinska Institutet, Karolinska University Hospital, 171 76, Stockholm, Sweden. antti.makitie@helsinki.fi.
3 Department of Otorhinolaryngology-Head and Neck Surgery, Turku University Hospital, University of Turku, P.O. Box 52, 20521, Turku, Finland.
4 Department Otorhinolaryngology-Head and Neck Surgery, Sørlandet Hospital, 4604, Kristiansand, Norway.
5 Department of Otorhinolaryngology-Head and Neck Surgery, Landspitalinn University Hospital, Reykjavik, Iceland.
6 Sundhedshuset, 8000, Aarhus C, Denmark.
7 ENT Clinic Frohnleiten, Medical University of Graz, 8130, Graz, Austria.
8 Department of Otorhinolaryngology-Head and Neck Surgery, Skåne University Hospital, Lund University, 205 02, Malmo, Sweden.