Speech Outcomes of Cochlear Implantation, from 1983 to Present: A Systematic Review

Objective We sought to assess whether the totality of advancements seen in cochlear implant (CI) design and implementation have translated to significant improvements in speech perception scores. Databases Reviewed EMBASE, PubMed/MEDLINE, and the Cochrane Central Register of Controlled Trials. Methods A systematic review of all English-language studies in peer-reviewed journals from 1946 to August 2022 was performed based on the Cochrane Handbook and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Eligible studies were of adult patients who underwent cochlear implantation with Cochlear®, Med-EL, or Advanced Bionics devices with 12 months postoperative sentence recognition testing results. Meta-regression was performed to assess the relationship between speech recognition score and year of implantation. Preimplantation score and unilateral versus bilateral implantation were adjusted for. Subgroup analysis was performed by restricting to studies of <5 years duration and in which outcomes were measured ≤12 months postoperatively to reduce the likelihood of patients with remotely implanted devices having undergone upgrades to more contemporary coding software. Results A total of 37 studies met criteria for inclusion, representing CIs implanted between 1983 and 2019. No significant association was identified between median study year and scores on 12-month postoperative sentence recognition testing on any of AzBio in quiet, CNC words, or HINT sentences in quiet. Subgroup analysis showed no difference in outcomes across 15 studies including patients implanted from 2007 to 2019. Conclusion In the absence of improved CI coding strategies since 2007, speech recognition outcomes in quiet have also not improved significantly since this time.