Factors Affecting Sound-Source Localization in Children With Simultaneous or Sequential Bilateral Cochlear Implants.

OBJECTIVES: The study aimed to determine the effect of interimplant interval and onset of profound deafness on sound localization in children with bilateral cochlear implants, controlling for cochlear implant manufacturer, age, and time since second implant. DESIGN: The authors conducted a retrospective, observational study using routinely collected clinical data. Participants were 127 bilaterally implanted children aged 4 years or older, tested at least 12 mo post- second implant. Children used implants made by one of three manufacturers. Sixty-five children were simultaneously implanted, of whom 43% were congenitally, bilaterally profoundly deaf at 2 and 4 kHz and 57% had acquired or progressive hearing loss. Sixty-two were implanted sequentially (median interimplant interval = 58 mo, range 3-143 mo) of whom 77% had congenital and 23% acquired or progressive bilateral profound deafness at 2 and 4 kHz. Children participated in a sound-source localization test with stimuli presented in a random order from five loudspeakers at -60, -30, 0, +30, and +60 degrees azimuth. Stimuli were prerecorded female voices at randomly roved levels from 65 to 75 dB(A). Root mean square (RMS) errors were calculated. Localization data were analyzed via multivariable linear regression models, one applied to the whole group and the other to just the simultaneously implanted children. RESULTS: Mean RMS error was 25.4 degrees (SD = 12.5 degrees) with results ranging from perfect accuracy to chance level (0-62.7 degrees RMS error). Compared with simultaneous implantation, an interimplant interval was associated with worse localization by 1.7 degrees RMS error per year (p < 0.001). Compared with congenital deafness, each year with hearing thresholds better than 90 dB HL at 2 and 4 kHz bilaterally before implantation led to more accurate localization by 1.3 degrees RMS error (p < 0.005). Every year post-second implant led to better accuracy by 1.6 degrees RMS error (p < 0.05). Med-El was associated with more accurate localization than Cochlear by 5.8 degrees RMS error (p < 0.01) and with more accurate localization than Advanced Bionics by 9.2 degrees RMS error (p < 0.05). CONCLUSIONS: Interimplant interval and congenital profound hearing loss both led to worse accuracy in sound-source localization for children using bilateral cochlear implants. Interimplant delay should therefore be minimized for children with bilateral profound hearing loss. Children presenting with acquired or progressive hearing loss can be expected to localize better via bilateral cochlear implants than their congenitally deaf peers.

Preliminary assessment of the feasibility of using AB words to assess candidacy in adults.

BACKGROUND: Adult cochlear implant (CI) candidacy is assessed in part by the use of speech perception measures. In the United Kingdom the current cut-off point to fall within the CI candidacy range is a score of less than 50% on the BKB sentences presented in quiet (presented at 70 dBSPL). GOAL: The specific goal of this article was to review the benefit of adding the AB word test to the assessment test battery for candidacy. RESULTS: The AB word test scores showed good sensitivity and specificity when calculated based on both word and phoneme scores. The word score equivalent for 50% correct on the BKB sentences was 18.5% and it was 34.5% when the phoneme score was calculated; these scores are in line with those used in centres in Wales (15% AB word score). CONCLUSION: The goal of the British Cochlear Implant Group (BCIG) service evaluation was to determine if the pre-implant assessment measures are appropriate and set at the correct level for determining candidacy, the future analyses will determine whether the speech perception cut-off point for candidacy should be adjusted and whether other more challenging measures should be used in the candidacy evaluation.

The effect of early auditory experience on the spatial listening skills of children with bilateral cochlear implants.

OBJECTIVES: Both electrophysiological and behavioural studies suggest that auditory deprivation during the first months and years of life can impair listening skills. Electrophysiological studies indicate that 3½ years may be a critical age for the development of symmetrical cortical responses in children using bilateral cochlear implants. This study aimed to examine the effect of auditory experience during the first 3½ years of life on the behavioural spatial listening abilities of children using bilateral cochlear implants, with reference to normally hearing children. Data collected during research and routine clinical testing were pooled to compare the listening skills of children with bilateral cochlear implants and different periods of auditory deprivation. METHODS: Children aged 4-17 years with bilateral cochlear implants were classified into three groups. Children born profoundly deaf were in the congenital early bilateral group (received bilateral cochlear implants aged ≤3½ years, n=28) or congenital late bilateral group (received first implant aged ≤3½ years and second aged >3½ years, n=38). Children with some bilateral acoustic hearing until the age of 3½ years, who subsequently became profoundly deaf and received bilateral cochlear implants, were in the acquired/progressive group (n=16). There were 32 children in the normally hearing group. Children completed tests of sound-source localization and spatial release from masking (a measure of the ability to use both ears to understand speech in noise). RESULTS: The acquired/progressive group localized more accurately than both groups of congenitally deaf children (p<0.05). All three groups of children with cochlear implants showed similar spatial release from masking. The normally hearing group localized more accurately than all groups with bilateral cochlear implants and displayed more spatial release from masking than the congenitally deaf groups on average (p<0.05). CONCLUSION: Children with bilateral cochlear implants and early experience of acoustic hearing showed more accurate localization skills, on average, than children born profoundly deaf.

The cost and analysis of nonuse of cochlear implants.

OBJECTIVE: Analysis of the cost implications and reasons for nonuse of cochlear implants in an established cochlear implant unit. STUDY DESIGN: Clinical data were analyzed retrospectively to construct a table of cochlear implant use over time to identify nonuse and to suggest the reasons for this. SETTING: Yorkshire Cochlear Implant Service is a tertiary referral center. PATIENTS: Three hundred forty consecutively implanted patients from 1990 to 2005. MAIN OUTCOME MEASURES: Life table analysis showed that most children used their implant (p = 0.7 during 11 yr). However, 11 of 155 children and 2 of 185 adults became nonusers during the period of study. The 11 children stopped because of age at implant, educational placement, and family support. Two adults stopped because of psychological issues and inability to adapt to the signal. Surgical and implant costs have initial impact, with subsequent years' costs reflecting programming issues and maintenance. When considering nonuse, there are 2 effects: first, no more costs are incurred, and second, no more years of use are accumulated. Thus, nonuse reduces both costs and years. Costs of gaining a year of use as a function of time showed that there was little financial impact from the 11 children nonusers. As a ratio of "no nonuse" and observed "nonuse" in children, the ratio is 1.07 by 13 years of implantation (7%). The adult group was too few to analyze. CONCLUSION: The nonuse added 7% to the average cost. Retrospective audit identifies that patient selection by a multidisciplinary team is crucial to reducing nonuse.