Effects of different morphological types of enlarged vestibular aqueduct on clinical onset and cochlear implantation.

Objective: To investigate the influence of different morphological features of the enlarged vestibular aqueduct (EVA) on clinical onset and postoperative speech rehabilitation outcomes in pediatric patients undergoing cochlear implantation (CI) at our institution. Methods: A retrospective analysis was conducted on children diagnosed with EVA who underwent primary CI at our hospital. Clinical data, audiological profiles, and imaging characteristics were reviewed. Patients were categorized based on hearing loss (HL) symmetry: symmetric HL group (interaural threshold difference < 20 dB) and asymmetric HL group (difference ≥ 20 dB). The symmetric HL group was further stratified by age of onset into early-onset and late-onset subgroups. Based on disease progression, patients were classified into sudden HL and fluctuating HL subgroups. Radiological measurements included the vestibular aqueduct (VA) aperture angle and length. Postoperative speech outcomes in the early-onset subgroup were followed up at 1-6 years post-CI and compared with a matched control group of children with normal inner ear structures undergoing CI during the same period. Results: Eighty-one children with EVA were enrolled. Fifty-six cases presented with symmetric HL, while 25 cases exhibited asymmetric HL. Regarding progression patterns, 24 cases were classified as fluctuating HL and 25 as sudden HL. In the symmetric HL group, the early-onset subgroup demonstrated significantly larger bilateral VA aperture angles and shorter bilateral VA lengths compared to the late-onset subgroup. In the asymmetric HL group, the ear with worse HL had a larger VA aperture angle but a shorter VA length than the better-hearing ear. Postoperative speech performance improved over time in both groups; however, the early-onset subgroup consistently scored lower across all four speech evaluation metrics at 1-6 years post-CI compared to the control group. Conclusion: A wide and shallow vestibular aqueduct appears to render children more susceptible to inner ear damage induced by intracranial pressure fluctuations. This morphological predisposition likely contributes to earlier onset, greater severity, and more sudden progression of hearing loss, ultimately compromising postoperative speech rehabilitation outcomes.