Functionally equivalent ages and hearing levels of children with cochlear implants measured with pre-recorded stimuli

Three groups of children undertook an interactive computer-based closed-set test of the ability to identify pre-recorded spoken words presented acoustically. The test was completed by 31/39 children with profound hearing loss who had used the Nucleus Spectra-22 cochlear-implant system for at least one year (Group A); by 30 children with normal hearing (Group B); and by 22 children with severe-profound hearing loss who used acoustic hearing aids (Group C). Among the implanted children, those who were younger when implanted and who had used their devices for longer produced higher scores (multiple-r = 0.68). Logistic regression functions were fitted to the data from Group B to describe the relationship between performance and age, and to the data from Group C to describe the relationships between performance and average hearing level (AHL) and aided threshold. By use of the regression equations, the performance of each implanted child was converted into a functionally equivalent (FE) age, an FE AHL and an FE aided threshold. Despite high variability leading to wide confidence intervals, these transformations showed that: (1) mean FE age (3.4 years) lagged mean chronological age (7.4 years), but some implanted children performed within the range expected for children with normal hearing of the same age; (2) mean FE AHL was 94 dB compared with a mean pre-implant AHL of 117 dB; (3) mean FE aided threshold was 45 dB(A) compared with a mean pre-implant aided threshold of 99 dB(A). These results confirm that implantation of appropriate candidates leads to functionally better hearing than would be expected with acoustic hearing aids. The results also demonstrate that many implanted children can participate in interactive tests with pre-recorded speech, thus providing robust data for comparison with future performance.