ABR findings in inner ear anomaly subgroups: Influence of cochlear nerve deficiency

PURPOSE: This study aimed to investigate auditory brainstem response (ABR) findings across subgroups of inner ear anomalies and to compare the ABR profiles in cases with cochlear nerve deficiency (CND). METHODS: A total of 189 ears from 109 individuals with various inner ear anomalies were evaluated. Radiological findings were used to classify each ear into specific anomaly subgroups and to assess cochlear nerve status. ABR outcomes were then analyzed accordingly. RESULTS: CND was consistently observed in complete labyrinthine aplasia, rudimentary otocyst, cochlear aplasia, and common cavity malformations, with absent ABR wave V and cochlear microphonic (CM) responses. Cochlear hypoplasia and incomplete partition subtypes showed variable ABR and CM responses. In cochlear aperture anomalies, CND was consistently observed, with absent wave V but detectable CM of variable latency. Wave V responses differed significantly between normal and CND ears (p < 0.001), whereas CM responses did not (p = 0.055). CONCLUSIONS: This study delineates ABR characteristics specific to inner ear anomaly subgroups and highlights the influence of CND on ABR outcomes. The findings underscore the potential of detailed ABR analysis to serve as a valuable tool for guiding auditory rehabilitation decisions and emphasize its relevance in shaping future clinical practice guidelines.