There are now many recipients of unilateral cochlear implants who have usable residual hearing in the non-implanted ear. To avoid auditory deprivation and to provide binaural hearing, a hearing aid or a second cochlear implant can be fitted to that ear. This article addresses the question of whether better binaural hearing can be achieved with binaural/bimodal fitting (combining a cochlear implant and a hearing aid in opposite ears) or bilateral implantation. In the first part of this article, the rationale for providing binaural hearing is examined. In the second part, the literature on the relative efficacy of binaural/bimodal fitting and bilateral implantation is reviewed. Most studies on comparing either mode of bilateral stimulation with unilateral implantation reported some binaural benefits in some test conditions on average but revealed that some individuals benefited, whereas others did not. There were no controlled comparisons between binaural/bimodal fitting and bilateral implantation and no evidence to support the efficacy of one mode over the other. In the third part of the article, a crossover trial of two adults who had binaural/bimodal fitting and who subsequently received a second implant is reported. The findings at 6 and 12 months after they received their second implant indicated that binaural function developed over time, and the extent of benefit depended on which abilities were assessed for the individual. In the fourth and final parts of the article, clinical issues relating to candidacy for binaural/ bimodal fitting and strategies for bimodal fitting are discussed with implications for future research.

Aim: The aim of this paper was to summarize the binaural advantages for sentence perception in noise and sound localization obtained by children and adults who wore a cochlear implant (CI) and a hearing aid in opposite ears (bimodal hearing devices). Patients and Methods: We evaluated the speech perception and sound localization ability of 29 children and 21 adults who received a Nucleus CI system in one ear and wore a hearing aid in the other ear. All subjects used hearing aids that were adjusted systematically to complement their CIs. Performance with a CI and a hearing aid was compared with that with a CI alone. Results: On average, both children and adults derived binaural advantages relating to binaural redundancy and head shadow for sentence perception in noise. Neither the degree of hearing loss nor the duration of use of bimodal hearing devices was significantly related to the amount of binaural speech benefits. Both groups also located sounds better with CI and a hearing aid than with CI alone. Conclusions: The evidence supports the implementation of binaural/bimodal fittings as the standard management of children and adults who receive a unilateral CI and who have residual hearing in the nonimplanted ear.

Listening to speech in competing sounds poses a major difficulty for children with impaired hearing. This study aimed to determine the ability of children (3-12 yr of age) to use spatial separation between target speech and competing babble to improve speech intelligibility. Fifty-eight children (31 with normal hearing and 27 with impaired hearing who use bilateral hearing aids) were assessed by word and sentence material. Speech reception thresholds (SRTs) were measured with speech presented from 0 azimuth, and competing babble from either 0 or 690 azimuth. Spatial release from masking (SRM) was defined as the difference between SRTs measured with co-located speech and babble and SRTs measured with spatially separated speech and babble. On average, hearingimpaired children attained near-normal performance when speech and babble originated from the frontal source, but performed poorer than their normal-hearing peers when babble was spatially separated from target speech. On average, normal-hearing children obtained an SRM of 3 dB whereas children with hearing loss did not demonstrate SRM. Results suggest that hearing-impaired children may need enhancement in signal-to-noise ratio to hear speech in difficult listening conditions as well as normal-hearing children.

We investigated speech perception advantages arising from the use of inter-aural time difference cues, and from the provision of redundant information by the use of a hearing aid contralateral to a cochlear implant (bimodal hearing devices). Thirty-eight subjects (14 normally hearing and 23 hearing-impaired) participated in this study. The effect of binaural redundancy was assessed by comparing the signal-to-noise ratio (SNR) required for 50% correct identification of sentences in noise when listening monaurally to that when listening binaurally. The use of inter-aural time difference cues was determined by comparing the binaural SNRs obtained with or without a noise delay of 700 micros between ears. Results indicated adults who used bimodal hearing devices benefited from binaural redundancy, but children did not. Whereas normally hearing subjects used inter-aural time difference cues to improve speech perception in noise, neither adults nor children who used bimodal hearing devices were able to do so.