Objective: To describe temporal bone findings on computed tomography (CT) imaging in GJB2-related hearing loss (HL). We asked whether evaluation of the temporal bone is required in individuals with biallelic GJB2 mutations.
Study design: Randomized, blinded, controlled, prospective measurement.
Methods: Blood from 264 pediatric cochlear implant users was analyzed for mutations in the GJB2 gene. Thirty-six aspects of the temporal bone on CT imaging were evaluated in 53 individuals (106 ears) with biallelic disease causing GJB2 mutations. A subset of patients was age matched and compared with normally hearing individuals. Subjects with biallelic GJB2 mutations were tested for mutations in the SLC26A4 gene to rule out Pendred syndrome as a confounding cause of large vestibular aqueduct syndrome.
Results: Approximately 53% of ears of subjects (72% of subjects) with biallelic GJB2 mutations had at least one temporal bone anomaly. The most common findings were 1) dilated endolymphatic fossa (28%); 2) hypoplastic modiolus (25%); 3) large vestibular aqueduct (8%); 4) hypoplastic horizontal semicircular canal (8%); 5) hypoplastic cochlea (4%). Compared with normally hearing individuals, the GJB2 group had hypoplasia of the cochlear nerve canal, lateral semicircular canal vestibule, internal auditory canal (t tests, P < .001), and were 11 times more likely to have a hypoplastic modiolus. Dilated endolymphatic fossae were 1.4 times more common in the GJB2 group, and large vestibular aqueducts were 3 times more common in the GJB2 group, as compared with normally hearing controls.
Conclusions: Temporal bone anomalies are common in GJB2-related HL, and imaging of the temporal bone should be included in routine evaluation of these individuals.