Influence of hearing in the non-implanted ear and age on long-term speech recognition benefit for adult cochlear implant users with asymmetric hearing loss

Abstract

Most cochlear implant (CI) users with normal hearing or mild to moderately-severe hearing loss in the non-implanted ear, known as asymmetric hearing loss (AHL), experience significant benefits in spatial hearing as compared to pre-operative abilities, though individual outcomes vary. This study analyzed the influence of the hearing in the non-implanted ear and age on long-term outcomes for 35 adult CI users with AHL. Unaided thresholds were measured behaviorally at annual post-activation visits and were used to calculate a pure-tone average (PTA; 0.5, 1, 2, 4 kHz). Sentence recognition in noise was assessed with the AzBio sentences in a 10-talker masker with the target presented from the front loudspeaker and the masker presented 90° toward the implanted ear, 90° towards the non-implanted ear, or co-located with the target. Spatial release from masking was calculated as the benefit in speech recognition when the masker was presented towards the implanted ear (SRMci) or the non-implanted ear (SRMcontra) as compared to the co-located configuration. Spatial release from masking did not change significantly after 1-year post-activation for SRMci and continued to significantly improve for SRMcontra. Hearing in the non-implanted ear significantly influenced SRMci. Age at surgery significantly influenced SRMcontra. Six (17%) participants experienced a PTA decline of ≥ 15 dB HL in the non-implanted ear, which negatively influenced spatial hearing. For those, performance generally improved with adjustments to the hearing aid fitting or after bilateral cochlear implantation. Long-term outcomes for adult CI users with AHL are significantly influenced by hearing in the non-implanted ear and age – though differentially across speech-in-noise configurations.