This study aimed to (a) investigate the effect of using a hearing aid in conjunction with a cochlear implant in opposite ears on speech perception in quiet and in noise, (b) identify the speech information obtained from a hearing aid that is additive to the information obtained from a cochlear implant, and (c) explore the relationship between aided thresholds in the nonimplanted ear and speech perception benefit from wearing a hearing aid in conjunction with a cochlear implant in opposite ears. Fourteen adults who used the Nucleus 24 cochlear implant system in 1 ear participated in the study. All participants had either used a hearing aid in the nonimplanted ear for at least 75% of waking hours after cochlear implantation, and/or, hearing loss less than 90 dB HL in the low frequencies in the nonimplanted ear. Speech perception was evaluated in 3 conditions: cochlear implant alone (CI), hearing aid alone (HA), and cochlear implant in conjunction with hearing aid in opposite ears (CIHA). Three speech perception tests were used: consonant-vowel nucleus-consonant (CNC) words in quiet, City University of New York style (CUNY) sentences in coincident signal and noise, and spondees in coincidental and spatially separated signal and noise. Information transmission analyses were performed on the CNC responses. Of the 14 participants tested, 6 showed significant bimodal benefit on open-set speech perception measures and 5 showed benefit on close-set spondees. However, 2 participants showed poorer speech perception with CIHA than CI in at least 1 of the speech perception tests. Results of information transmission analyses showed that bimodal benefit (performance with CIHA minus that with CI) in quiet arises from improved perception of the low frequency components in speech. Results showed that participants with poorer aided thresholds in the mid-to-high frequencies demonstrated greater bimodal benefit. It is possible that the mid-to-high frequency information provided by the hearing aids may be conflicting with the cochlear implants.

The aims of the present study are to investigate: (1) the effect of using a hearing aid (HA) or a second cochlear implant (2nd CI) on speech recognition in noise for children; (2) the ability to perceive phoneme groups of different frequencies when using a CI and an HA in opposite ears (bimodal fitting) and when using a CI in each ear (bilateral implant fitting), and (3) the relationship between aided thresholds in the HA ear and bimodal advantage. Thirteen school-age children who consistently used a bimodal or bilateral implant fitting participated. Perception was evaluated using consonant-nucleus-consonantwords presented from in front with noise from either side. Significant bimodal or bilateral CI advantage in speech perception was demonstrated by most subjects in at least 1 noise condition. Comparisons indicated that the bimodal advantage obtained by the bimodal subjects was greater than the bilateral CI advantage obtained by the bilateral-implant subjects in the noise front condition, but also suggested that the 2nd CI may provide more functional advantage in real life. The mechanisms underlying the advantage provided by the second device appear to be different in the bimodal and bilateral groups. Information transmission analysis did not show a clear difference between the groups in the pattern of advantage across phoneme groups. For the bimodal subjects, those with better aided thresholds at low frequencies and poorer aided thresholds at 4 kHz demonstrated greater bimodal advantage. Overall, these findings encourage the use of bimodal and bilateral implant fittings for children, provide insight into the individual variability in bimodal outcome, and enhance understanding of the differences between an HA and a 2nd CI when used together with an implant in the opposite ear.

Children over age 4 yr may gain significant additional benefit from a second implant, including improved speech perception in some noise contexts and functional advantages in daily life. There is, however, no evidence from this study to suggest that binaural listening skills, including localization, will develop during the first 6 mo. Furthermore, some children who may be committed users of a first implant may not adapt to or benefit from a second implant during the first 6 mo of device use. Although the factors influencing benefit cannot be clearly identified, limited preoperative auditory experience with the second ear, a delay of years between implants, relatively advanced age, and lack of second-implant-alone experience do not preclude benefit. Continued evaluation of these and additional subjects will clarify the factors that do contribute to benefit. Such information will be vital in helping families of implanted children to make an informed decision regarding a second implant.

The aim of this study was to describe the adaptation to bilateral cochlear implant use and the perceptual benefits demonstrated by 10 children who were successful users of a first implant when a second was received before four years of age. Although one subject rejected the second implant at switch-on, the nine subjects who accepted the device adapted easily to bilateral implant use and developed useful listening skills with the second implant. Tests of localization (left versus right) and speech detection in noise were administered in the unilateral and bilateral conditions, usually after six months experience. All subjects demonstrated some bilateral benefit on speech detection testing (mostly due to a headshadow effect), and the majority localized left versus right. Results suggested that outcomes may be negatively impacted by increased age at the time of second implant switch-on. The majority of the subjects adapted well to bilateral implant use within six months and demonstrated some perceptual benefit and, according to subjective parent reports, improved daily functioning; however, device rejection must be discussed pre-operatively as a possibility.

Listening in background noise was more difficult for our group of children with AN/AD-type hearing loss than for their normal-hearing peers. However, the noise effects were not consistent across subjects and some children demonstrated reasonable perceptual ability at low signal-to-noise ratios. The ways in which speech understanding is affected by competing signals may be different for different types of hearing deficit, but the results of this investigation indicate that significant perceptual disruption occurs both in children with auditory neuropathy/dys-synchrony and sensorineural type hearing loss.