OBJECTIVE: Description of two siblings with unexplained, progressive, perceptive hearing loss after head trauma. DESIGN: Case report. SUBJECTS: Two siblings aged six and eight years old with bilateral, intermittent but progressive hearing loss. RESULTS: These patients had a c.1172G>A (p.Ser391Asn) mutation in the SLC26A4 gene, which has not previously been reported and which caused Pendred or enlarged vestibular aqueduct syndrome. The diagnosis was based on the perceptive hearing loss, computed tomography findings and mutation analysis. The patients were each fitted with a cochlear implant because of their severe, progressive, perceptive hearing loss with deep fluctuations. The results were good. CONCLUSION: Further testing for the presence of an enlarged vestibular aqueduct is recommended when children present with sudden progression in perceptive hearing loss, whether or not in combination with head trauma. Cochlear implantation is indicated in patients with persistent, progressive hearing loss that leads to deafness. Implantation can be undertaken successfully despite cochlear hypoplasia.