Benefits of bimodal stimulation in children with cochlear implant: Role of contralateral residual acoustic hearing and auditory experience with bimodal stimulation

Abstract

There is a continuing growth in the number of cochlear implant (CI) recipients who have some amount of usable residual acoustic hearing in at least one ear. Many such recipients obtain perceptual benefits from the use of hearing aid (HA) in the contralateral ear. The present study aimed to assess the benefits of bimodal stimulation (i.e. CI in one ear and HA in the contralateral ear) in children as a function of the level of contralateral residual acoustic hearing and auditory experience with bimodal stimulation. Speech recognition performance was evaluated in quiet and noisy environments under monaural CI alone and bimodal CI+HA listening conditions. The results revealed that there was a significant effect of noise on speech recognition performance. There was a significant reduction (p<0.05) in speech recognition performance under monaural CI alone listening condition in noisy environment. However, the effect of noise on speech recognition performance was minimized under bimodal CI+HA listening conditions as compared to monaural CI alone listening condition. The subjects obtained significantly higher (p<0.05) speech recognition performance under bimodal CI+HA listening condition as compared to monaural CI alone listening condition especially in noisy environments. It was further observed that the subjects obtained similar bimodal benefit irrespective of differences in the level of contralateral residual acoustic hearing. However, subjects with longer duration of auditory experience with bimodal stimulation could only achieve significant bimodal benefits compared to the subjects with less auditory experience with bimodal stimulation. Hence, children who receive a monaural cochlear implant and cannot opt for bilateral cochlear implantation for whatever reasons should be encouraged to use a hearing aid in the opposite ear irrespective of the level of residual acoustic hearing in that ear. However, sufficient auditory experience with bimodal stimulation is needed to achieve this bimodal benefit.