Systematic review of outcomes of cochlear implantation of different genotypes in patients with auditory neuropathy spectrum disorder

Background The diagnosis of auditory neuropathy spectrum disorder (ANSD) is based on the existence of cochlear microphonics or otoacoustic emissions, as well as aberrant or nonexistent-evoked auditory brainstem responses. The outcomes of cochlear implantation (CI) are thought to be significantly influenced by genetic reasons in ANSD. Objective The purpose of this systematic review was to gather more information regarding the relationship between various genetic variants and the outcomes of cochlear implantation in adult and pediatric patients with ANSD (both syndromic and non-syndromic). Methods Electronic databases "Medline/PubMed, Google Scholar, ScienceDirect, Europe PMC, and Cochrane Library" were searched for this systematic review. For cohort studies, the Newcastle-Ottawa scale (NOS score) was used to assess the quality of the retrieved research. The standardized mean difference produced by the Cohen's d or Hedges' g tests was used to assess the effect size measure. Results This comprehensive study showed that OTOF, GJB2, ATPA3, and OPA1 were among the genetic variants with improved CI outcomes. On the other hand, other genetic mutations displayed variable results (TMPRSS3) or worse CI outcomes (PJVK). For OTOF mutations, CI had a moderate effect (Hedges' g = 0.7), which led to good cochlear implant outcomes. The results of the GJB2 cochlear implant showed a significant effect size when pre- and post-implant assessments were compared. The results of CI for TMPRSS3 mutations were inconsistent, with one study demonstrating a negligible effect (Hedges' g = 0.2), and another study found a negative impact (Hedges' g = - 2.17). Poor CI results were indicated by PJVK mutations impacting CI outcomes. A significant impact was observed when comparing pre- and postimplantation outcomes (Cohen's d > 1) in cases of ATP1A3 mutations (CAPOS syndrome) and OPA1 mutations. In addition, early implantation produced better results than late implantation in certain genetic variations. Conclusion Some genetic variants, such as OTOF, GJB2, ATPA3, and OPA1, had improved CI outcomes, according to data extraction and synthesis of the systematic review's findings. Conversely, PJVK displayed worse CI results and inconsistent results for TMPRSS3 genetic mutations.