11Best of Both Worlds: Bimodal Hearing (CI + Hearing Aid)

FWhat bimodal hearing is

Bimodal hearing means a cochlear implant in one ear and an acoustic hearing aid in the contralateral ear, so the two ears are stimulated by fundamentally different means: electric pulses on one side, amplified sound on the other. The candidate for bimodal hearing is the implant user whose other ear retains aidable residual hearing, typically usable low-frequency thresholds even when the high frequencies are unaidable. Bimodal is distinct from electric-acoustic stimulation (EAS), in which electric and acoustic hearing are combined within the SAME ear after hearing-preservation implantation; bimodal combines the two across the two ears. Because most newly implanted adults simply keep wearing their existing hearing aid on the other ear, bimodal hearing is the default starting configuration for many users rather than a special intervention.[2004][2007]

TWhy the two ears complement each other

The cochlear implant excels at delivering high-frequency consonant detail and the temporal envelope of speech, but it codes pitch and fine temporal structure poorly. An acoustic hearing aid on residual low-frequency hearing preserves temporal fine structure and the fundamental frequency (F0) of voices, which carries voice pitch, intonation and the low-frequency portion of music. Combining the two gives the brain electric high-frequency detail plus acoustic low-frequency fine structure, a complementary pairing rather than two copies of the same impoverished signal. The low-frequency acoustic cue is especially valuable for separating a target voice from competing talkers, because F0 differences help the listener latch onto and follow one speaker.[2004][2011]

TThe documented bimodal benefit

Ching and colleagues showed adults using an implant plus a contralateral hearing aid gained binaural benefits over the implant alone, with the acoustic ear contributing voice and music cues the implant could not. Bimodal users show measurable gains in speech recognition in noise, music perception, affective prosody (emotional tone of voice), and talker identification compared with the implant alone. Cullington and Zeng found bimodal users performed at least as well as bilateral implant users on competing-talker speech, music, prosody and talker identification, with differences that did not reach statistical significance. Beyond test scores, bimodal aiding reduces listening effort and improves perceived sound quality, dimensions that pure intelligibility scores miss but that strongly affect daily satisfaction.[2004][2011][2017]

CBimodal or a second implant?

As long as the non-implanted ear provides genuinely useful acoustic information, bimodal hearing is a low-risk, low-cost way to obtain two-eared benefit without a second surgery. When residual acoustic hearing in that ear declines until the hearing aid no longer adds useful information, a second cochlear implant becomes the logical next step to restore binaural input. The decision turns on the value of the residual acoustic ear: good low-frequency hearing favors staying bimodal, while a hearing aid that the patient barely uses or that no longer contributes favors a second implant. Patient preference matters because some bimodal users strongly value the natural, acoustic sound quality of the aided ear and are reluctant to give it up even when objective scores would be similar with two implants.[2011][2007][2017]