Effectiveness of hearing preservation interventions in cochlear implantation patients: A systematic review and meta-analysis

Cochlear implantation (CI) is a well-recognized method for hearing restoration in patients with sensorineural hearing loss. Studies demonstrated that residual hearing, especially the low frequency range, can be preserved after CI. The current systematic review and meta-analysis aim to provide solid evidence based on systematic search regarding hearing preservation and hearing thresholds in CI recipients.

We systematically searched three electronic databases, PubMed, Scopus and Web of Science, to collect relevant records. We included clinical trials and observational studies that investigated the effect of CI alone or accompanied with a hearing preservation method on hearing thresholds or incidence of hearing preservation. Double-arm and single-arm meta-analysis models were conducted using OpenMeta[Analyst] software to examine the effect of steroids and intra-operative auditory monitoring as a hearing preservation method. Also, Single-arm analysis models pooled studies that adopted soft surgical techniques.

The current study included a total of 35 observational studies, 9 non-randomized clinical trials, and 8 RCTs. In a meta-analysis model of five studies, the pooled SMD of both hearing threshold post-implantation and change from baseline - at all available frequencies - favored steroid group over control group (post-implantation: SMD=-0.706, P < 0.001; change from baseline: SMD=-0.337, P = 0.009) at the time of activation. Also, the pooled SMD of post-implantation hearing threshold and change from baseline favored steroid group over control group (post-implantation: SMD=-0.901, P = 0.001; change from baseline: SMD=-0.422, P = 0.033) at 6 months post-implantation. Moreover, the pooled SMD of post-implantation hearing threshold favored steroid group over control group (SMD=-0.666, P < 0.00) at 12 months post-implantation. However, the pooled SMD of change from baseline at 12 months did not favor either steroid or control groups (SMD=-0.216, P = 0.078). Intra-operative monitoring with real-time feedback showed better post-implantation hearing thresholds and more favorable change from baseline compared to groups with no real-time feedback (post-implantation: SMD=-0.888, P = 0.001; change from baseline: SMD=-0.565, P = 0.01). In a single-arm meta-analysis, the pooled threshold change from baseline up to 12 months was 15.239, 14.944, 9.691 and 2.489 at all available, low, middle and high frequencies, respectively.

This meta-analysis demonstrates that steroid use significantly enhances short-term hearing preservation following cochlear implant surgery. While intra-operative auditory monitoring shows promise, further clarity is needed regarding its consistent benefits. The adoption of soft surgical techniques also offers favourable outcomes; however, more randomized controlled trials are needed.