Bilateral bone-anchored hearing aids for bilateral permanent conductive hearing loss: A systematic review

Objective. To systematically review the outcomes of bilateral versus unilateral bone-anchored hearing aids (BAHA) for individuals with bilateral permanent conductive hearing loss (CHL) with the goal of (1) deriving clinically oriented insights into the advantages and disadvantages of bilateral fitting and (2) identifying gaps in knowledge to stimulate future research. Data Sources. Medline, EMBASE, and Cochrane databases were searched for studies of all languages published between 1977 and July 2011. Review Methods. Studies were included if subjects of any age had permanent bilateral CHL and bilateral implanted BAHAs. Outcome measures of interest were any subjective or objective audiologic measures, quality of life indicators, or reports of adverse events. Results. In all, 628 abstracts were generated from the literature searches; 11 studies met the criteria for data extraction and analysis. All 11 studies were observational. In most studies, comparisons between unilateral and bilateral BAHA were intra-subject. Bilateral BAHA provided audiologic benefit compared to unilateral BAHA (improved thresholds for tones [2 studies], speech in quiet [5 studies] and in noise [3 studies], and improved localization/lateralization [3 studies]) and patients' perceived subjective benefit from bilateral BAHA (3 studies). Disadvantages of bilateral BAHAs included listening in noise in some conditions (3 studies), presumed additional cost, and presumed increase in adverse event risk. Conclusion. Bilateral BAHA provided additional objective and subjective benefit compared to unilateral BAHA; however, there was a limited number of studies available with good quality evidence. Aspects of bilateral BAHA that would benefit from further investigation are described, and recommendations for bilateral BAHA candidacy criteria are provided.