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 similar amount of listening effort expended by the two groups indicated that a higher signal-to-noise ratio overcame limitations in the auditory information received or processed by the participants with implants. This study is the first to objectively compare listening effort using two versus one cochlear implant. The results provide objective evidence that reduced listening effort is a benefit that some individuals gain from bilateral cochlear implants.
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.
Subjective assessment of hearing ability in everyday life complements more objective forms of evaluation. A broad evaluation of the additional benefit provided to children by a second bilateral cochlear implant required such an assessment. As no paediatric tool provided detailed evaluation of performance in the areas of daily listening in which benefit was likely to be demonstrated, an adult questionnaire was adapted. Items of the Speech, Spatial and Qualities of Hearing Scale (SSQ) focused mainly, although not exclusively, on hearing functions requiring the binaural system. The adapted child, parent, and teacher versions of the SSQ retained the structure of rating listening performance in everyday scenarios across the domains of speech perception, spatial hearing, and other qualities of hearing. Modifications were minimized, although deletion of some items and wording changes were required, and some subdomains could not be included. Observation periods were introduced so that parents and teachers observe performance prior to providing ratings. The suggested minimum age is 11 years for the child version and 5 years for the parent and teacher versions. Instructions indicate interview-style administration in which interpretation of the described listening scenarios can be clarified and use of the ruler-style response format demonstrated. Researchers applying the SSQ for parents have reported higher performance ratings for bilateral over unilateral cochlear implants, particularly in the spatial hearing domain. Further research should provide evidence for the target age range, compare child and parent responses, and evaluate modifications for use with younger children.
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