Tonotopic versus conventional frequency mapping in adult cochlear implant recipients: a systematic review and...

In adult cochlear implant users, conventional frequency (CF) mapping is standard practice. Tonotopic fitting (TF) refers to a programming strategy in which the frequency allocation of the speech processor is matched as closely as possible to the natural tonotopic organization of the cochlea. Whether TF mapping improves outcomes over CF remains uncertain.

We searched PubMed, Embase, and Cochrane for randomized controlled trials comparing tonotopic versus conventional mapping in adult cochlear implant users. Random-effects meta-analysis was performed using RevMan 5.4. Continuous outcomes were analyzed using standardized mean difference (SMD) with 95% confidence intervals (CIs), and heterogeneity was assessed with I². A two-tailed P-value < 0.05 was considered statistically significant. We created an effect-direction plot for selected outcomes to provide a visual summary of the direction and consistency of effects across studies.

A total of five publications were included, representing four trials (n = 109). There was no significant difference between TF and CF mapping in speech understanding in quiet (SMD = -0.07; 95% CI -0.82, 0.68; P = 0.86; I² = 79%) and in noise (SMD = 0.51; 95% CI -0.44,1.46; P = 0.30; I² = 93%). The sensitivity analysis for speech understanding in noise favored TF. Also music perception favored TF on the effect direction plot, while sound quality showed variable outcomes.

TF mapping may have potential benefits over CF mapping for speech understanding in noise and music perception. Larger randomized trials are needed to establish the clinical significance of TF mapping.