Jan 2019 The Hearing Journal
Nearly three-fourths of adult cochlear implant (CI) recipients have aidable acoustic hearing in the non-implanted ear that could be used in a bimodal hearing configuration. For a typical CI candidate, the amount of residual acoustic hearing is not sufficient to allow high levels of daily communication; however, that residual acoustic hearing can provide significant speech recognition and sound quality benefit when paired with a CI in a bimodal hearing configuration. Bimodal hearing also provides significantly improved performance on various tasks of music perception, including chord, melody, melodic contour, and timbre recognition, compared with a CI-alone condition.
Several bimodal hearing solutions are available, but there remains some confusion about optimal bimodal fittings, as the degree of bimodal benefit resulting from adding a hearing aid (HA) to a CI varies considerably among patients. Though unaided audiometric thresholds in a non-implanted ear and bimodal benefits have an inverse correlation, this correlation is driven by the extreme ends of the function, leaving little clinical guidance for the majority of patients with moderate to severe sensory losses in the non-implanted ear. While some studies provide guidance for the clinical fitting of bimodal listeners, there is a lack of prospective studies with large sample sizes that provide data-driven guidance for clinical fittings. Optimal bimodal fitting holds high clinical relevance to provide maximum bimodal benefit to patients with unilateral CI and accurately determine bilateral CI candidacy.
While we await the outcomes of prospective clinical trials systematically investigating the efficacy of various approaches to bimodal fitting in large populations, some peer-reviewed papers provide clinical guidance to inform and improve current audiology practices.