A 2011 AHRQ review of the evidence of the effectiveness of CI in people with bilateral hearing loss - the device's primary use - found low to moderate quality data that showed:
speech perception in noisy conditions was much better for people who had implants in both ears done at the same time, compared to people who had only one; that no conclusions could be drawn about changes in speech perception in quiet conditions and health-related quality-of-life. There was only one good study comparing implanting implants in both ears at the same time, to implanting them sequentially; this study found that in the sequential approach, the 2nd implantation made no change, or made things worse.
[6]
A 2015 review, examining whether CI implantation to treat people with bilateral hearing loss had any effect on
tinnitus, found the quality of evidence to be poor, and the results variable: overall total tinnitus suppression rates varied from 8% to 45% of people who received CI; decrease of tinnitus was seen in 25% to 72%, of people; for 0% to 36% of the people there was no change; increase of tinnitus occurred in between 0% to 25% of patients; and in between 0 - 10% of cases, people who didn't have tinnitus before the procedure, got it.
[7]
A 2016 systematic review of CI for people with
unilateral hearing loss found that of the studies conducted and published, none were randomized, only one evaluated a control group, and no study was blinded; after eliminated multiple uses of the same subjects, the authors found that 137 people with UHL had received a CI.
[8] While acknowledging the weakness of the data, the authors found that CI in people with UHL improves
sound localization compared with other treatments in people who lost hearing after they learned to speak; in the one study that examined this, CI did improve sound localization in people with UHL who lost hearing before learning to speak.
[8] It appeared to improve
speech perception and to reduce
tinnitus.
[8]
A 2015 literature review on the use of CI for people with
auditory neuropathy spectrum disorder found that description and diagnosis of the condition was too heterogeneous as of that date, to make clear claims about whether CI is a safe and effective way to manage it.
[9]