1. Department of Otorhinolaryngology, Marquesado de Santa Marta 1, Clínica Universidad de Navarra, 28047 Madrid, Spain
2. Department of Otorhinolaryngology, Clínica Universidad de Navarra, 31008 Pamplona, Spain
3. Department of Otorhinolaryngology, Hospital Universitario de Móstoles, 28938 Madrid, Spain
4. Department of Otorhinolaryngology, Facultad de Medicina, Universidad Francisco de Vitoria, 28223 Madrid, Spain
5. Department of Otorhinolaryngology, Hospital Universitario Donostia, 20014 San Sebastian, Spain