Bilateral Enlarged Vestibular Aqueduct: Auditory, Genetic and Radiological Characterization, and Benefits of Cochlear Implants.

Abstract

The study aimed to describe the auditory phenotype of patients with bilateral enlarged vestibular aqueduct, including benefits of cochlear implantation, and to look for genotype-phenotype correlation. Retrospective single-center study. Tertiary adult reference center. Fifty-eight patients were included. Evolution of pure tone and speech audiometry was analyzed. Cochlear size, vestibular aqueduct width, and endolymphatic duct and sac volume were assessed on both computed tomography scan and magnetic resonance imaging. Genetic explorations were documented, and genotype-phenotype correlations were explored. Outcomes after cochlear implant (CI) were analyzed. Hearing loss was diagnosed at 4 ± 4.0 years, being initially severe-to-profound in 74% of the ears. Sudden sensorineural hearing loss concerned 54% of patients. Both vestibular aqueduct and endolymphatic sac showed symmetric measurements (P < .001). Patients with SLC26A4 biallelic alterations (n = 22) had more associated thyroid disorders (14/22 vs 3/31, P < .001), earlier (2 ± 1.6 years old [yo] vs 5 ± 4.5 yo, P < .001) and lower age-adjusted pure-tone average (P < .001, two-way analysis of variance), and greater endolymphatic sac volume (369 ± 118.1 mm³ vs 194 ± 208.7 mm³, P = .042), compared with patients with unconclusive genetic results. Consequently, more patients with SLC26A4 biallelic alterations received a CI (19/22 vs 17/31, P = .015) and at an earlier age (18 ± 12.5 yo vs 34 ± 18.9 yo, P = .009). Finally, 12 months after cochlear implantation, speech intelligibility for words improved from 23% ± 27.6% to 61% ± 34.7% in silence (P = .0012), and from 30% ± 31.3% to 87% ± 10.6% in noisy conditions. The auditory phenotype of patients with bilateral enlarged vestibular aqueduct is variable but seems to be more severe in case of biallelic alterations of SLC26A4. However, cochlear implantation benefits to these patients, regardless of genotype.