Evaluation of the bimodal benefit in a large cohort of cochlear implant subjects using a contralateral hearing aid.

Abstract

To investigate the benefit of contralateral residual hearing in a large group of cochlear implant recipients with different degrees of residual hearing. One hundred and forty-one adult patients (age in years: mean 58.82, min 16.27, max 88.20) wearing a cochlear implant and a contralateral hearing aid, bimodal. Rehabilitative. All 141 patients underwent speech perception testing in quiet and noise with cochlear implant (CI) alone, and with CI and hearing aid (HA). Additionally, pure-tone air conduction threshold levels were measured in all subjects. The bimodal benefit was analyzed and correlations to the hearing threshold for different audiometric frequencies were calculated. Comparison between the scores for CI alone and CI + HA showed statistically significant advantages (p < 0.0001) in all four tests. The benefit for sentences in noise to each individual patient showed a negative correlation with the hearing threshold level of 125 Hz and 250 Hz, using a linear regression analysis applying the Spearman's rho correlation coefficient (r = -0.32, -0.232), and a significant difference at p = 0.006, p = 0.007. The correlations involving speech understanding in sentences in noise, and the hearing level of 500 Hz and above, are not significant for the benefit obtained with a contralateral hearing aid. The benefit of combined electric and acoustic hearing in bimodally fitted subjects depends mainly on residual hearing in the low-frequency range below 500 Hz. For bimodal fitting to yield significant benefits, hearing loss in the contralateral ear should not exceed 80 dB HL in the low frequencies.