1. Departments of Otolaryngology, Head and Neck Surgery, Uppsala University Hospital, University Uppsala, Uppsala, Sweden;
2. Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden;
3. Department of ENT, Akershus University Hospital, University of Oslo, Oslo, Norway;
4. Centre for Clinical Research, Region Vastmanland-Uppsala University, Hospital of Vastmanland, Västerås, Sweden