[1] Ain Shams Univ, Fac Med, Dept Otorhinolaryngol, Phoniatr Unit, Cairo 11566, Egypt
[2] Univ Coll Hosp London NHS Trust, London, England
[3] Natl Hosp Neurol & Neurosurg, London, England
[4] UCL, Dept Targeted Intervent, London, England
[5] City Univ London, Dept Hlth Sci, London, England
[6] Helsinki Univ Hosp, Dept Otorhinolaryngol & Phoniatr Head & Neck Surg, Helsinki, Finland
[7] Univ Helsinki, Helsinki, Finland
[8] Zagazig Univ, Dept Otorhinolaryngol, Phoniatr Unit, Zagazig, Egypt
[9] Assiut Univ, Dept Otorhinolaryngol, Phoniatr Unit, Assiut, Egypt