The effectiveness of bilateral cochlear implants for severe-to-profound deafness in adults: a systematic review

Objective: Assessment of the clinical effectiveness of bilateral cochlear implantation compared with unilateral cochlear implantation or bimodal stimulation, in adults with severe-to-profound hearing loss. In 2007, the National Institute for Health and Clinical Excellence (NICE) in the U. K. conducted a systematic review on cochlear implantation. This study forms an update of the adult part of the NICE review.

Data Sources: The electronic databases MEDLINE and Embase were searched for English language studies published between October 2006 and March 2011.

Study Selection: Studies were included that compared bilateral cochlear implantation with unilateral cochlear implantation and/or with bimodal stimulation, in adults with severe-to-profound sensorineural hearing loss. Speech perception in quiet and in noise, sound localization and lateralization, speech production, health-related quality of life, and functional outcomes were analyzed.

Data Extraction: Data extraction forms were used to describe study characteristics and the level of evidence.

Data Synthesis: The effect size was calculated to compare different outcome measures.

Conclusion: Pooling of data was not possible because of the heterogeneity of the studies. As in the NICE review, the level of evidence of the included studies was low, although some of the additional studies showed less risk of bias. All studies showed a significant bilateral benefit in localization over unilateral cochlear implantation. Bilateral cochlear implants were beneficial for speech perception in noise under certain conditions and several self-reported measures. Most speech perception in quiet outcomes did not show a bilateral benefit. The current review provides additional evidence in favor of bilateral cochlear implantation, even in complex listening situations.