Bilateral cochlear implantation: an evidence-based medicine evaluation

Abstract

Objectives/hypothesis: The aim of this study was to evaluate the extent and quality of evidence reported on the outcomes of bilateral cochlear implantation and thereby to inform opinion about future patient management.

Study design: Retrospective literature review.

Methods: A detailed search of the medical literature was performed using the Medline, Embase, and CINAHL databases starting from the date of their conception. The quality of evidence in each article was assessed according to the categories of evidence as defined by the Oxford Centre for Evidence-based Medicine, Levels of Evidence (May 2001).

Results: A total of 37 studies were included; 28 (76%) investigated adult participants only, 7 (19%) investigated child participants, and 2 (5%) contained both groups. Of the studies presented, 9 (24%) studies contained level 2b evidence, 2 (6%) level 3b, 16 (43%) level 4, and 10 (27%) level 5 evidence. No studies were identified as representing evidence level 1. Adult bilateral recipients demonstrated an increase in sentence recognition of 21% correct over their first implanted ear (P < .001) and mean bilateral localization errors of 24 degrees against a monaural error of 67 degrees (P < .005).

Conclusions: The available evidence indicates that bilateral cochlear implantation confers material benefits not achievable with unilateral implantation, specifically in terms of sound localization and understanding of speech in noise. Well-designed prospective studies of sufficient size are now needed to precisely quantify these benefits, to validate outcome measures, especially in children, and to define the criteria for intervention.