Cross-sectional study demonstrates interaural asymmetry limits binaural summation in bilateral cochlear implant users, highlighting the critical role of poorer ear performance.
Key Points
Investigate how monaural performance, interaural asymmetry, and implantation timing (simultaneous vs. sequential) influence binaural spectral ripple discrimination and binaural summation in bilateral cochlear implant users.
Enrolled 20 Mandarin-speaking adult bilateral cochlear implant (BiCI) users: 10 with simultaneous implantation and 10 with sequential implantation.
Evaluated spectral resolution using the Spectral-temporally Modulated Ripple Test (SMRT) under monaural and binaural listening conditions.
Quantified binaural summation benefit (binaural minus better-ear SMRT score) and interaural asymmetry (difference between individual ear scores).
Binaural and monaural SMRT scores showed no significant differences between simultaneously and sequentially implanted groups.
Greater interaural asymmetry strongly correlated with reduced binaural summation in both the simultaneous (r = −.91, p < .001) and sequential (r = −.89, p < .001) groups.
Binaural SMRT performance correlated significantly with poorer-ear scores (r = .70, p < .001) and was predicted by poorer-ear performance (p < .001) alongside poorer-ear laterality (p = .022).