Influence of contralateral acoustic hearing on adult bimodal outcomes after cochlear implantation

Objective: To examine post-implantation benefit and time taken to acclimate to the cochlear implant for adult candidates with more hearing in the contralateral non-implanted ear than has been previously considered within local candidacy guidelines. Design: Prospective, within-subject experimental design. Study sample: Forty postlingual hearing-impaired adult subjects with a contralateral ear word score in quiet ranging from 27% to 100% (median 67%). Results: Post-implantation improvement of 2.4dB and 4.0dB was observed on a sentence in coincident babble test at presentation levels of 65 and 55dB SPL respectively, and a 2.1dB benefit in spatial release from masking (SRM) advantage observed when the noise location favoured the implanted side. Significant post-operative group mean change of between 2.1 and 3.0 was observed on the sub-scales of the speech, spatial, and qualities (SSQ) questionnaire. Degree of post-implantation speech reception threshold (SRT) benefit on the coincident babble test and on perception of soft speech and sounds in the environment was greater for subjects with less contralateral hearing. The degree of contralateral acoustic hearing did not affect time taken to acclimate to the device. Conclusions: The findings from this study support cochlear implantation for candidates with substantial acoustic hearing in the contralateral ear, and provide guidance regarding post-implantation expectations.