The benefit of bilateral cochlear implants in adults with bilateral sensorineural hearing loss: a systematic review and meta-analysis

To perform a systematic literature review (SLR) on hearing and quality-of-life (QoL) benefits of bilateral versus unilateral cochlear implants (CIs) in adults with sensorineural hearing loss (SNHL), and to quantify benefits through a meta-analysis when feasible.
Embase, MEDLINE, and Cochrane were searched from January 2005–June 2022. Eligible studies presented effectiveness of CIs and/or QoL of adult CI users. Articles that presented numerical point estimates for, or numerical difference between, bilateral and unilateral CI, and measures of uncertainty were considered for meta-analysis, with data analyzed using fixed- and random-effects models.
Thirty-five articles were included. There was a trend of significant improvement with bilateral CIs in sound localization and binaural redundancy. A meta-analysis confirmed statistically significant benefits in speech perception (in quiet, 12.6 percentage point [95% confidence interval: 7.1, 18.1] improvement; in noise, improvement in speech reception threshold of 1.5 dB signal-to-noise ratio [–1.5 dB; 95% confidence interval: −2.5, −0.4]). There were beneficial trends of bilateral CIs regarding head-shadow effect and binaural release from masking. Significant improvements in hearing-specific QoL were observed; generic QoL was mostly unchanged.
Bilateral CIs provide audiological benefit over unilateral CI, resulting in hearing-specific QoL improvements. Lack of changes in generic QoL may reflect that instrument domains are insensitive to hearing-related changes when going from unilateral to bilateral CIs. Meta-analyses could not be performed for all hearing and QoL outcomes owing to variability in methodologies across studies.
These findings should be used to inform clinical decision-making to ensure the best outcomes for adults with bilateral SNHL.