Following systematic skull imaging of hundred and sixty seven individuals attending a medical referral centre for the deaf in Brussels, Belgium, fifteen patients (9 per cent) aged between two and 25 years were diagnosed with dilatation of the vestibular aqueduct. Careful audiological study, with a baseline assessment then longitudinal follow up, indicated mild to profound deafness with a progressive course (i.e. an average loss of 3.3 dB per year) and frequent dizziness. Sequencing of PDS was performed in all individuals. Alterations of this gene (either homozygous, heterozygous or compound heterozygous base changes) were found in 53 per cent of patients with a large vestibular aqueduct. Four new mutations (two missense, a splice site and a four base pair insertion) were described. We were unable to confirm a correlation between homozygosity, heterozygosity and a Pendred or deafness-only phenotype.
