Results Of Cochlear Implantation In Children Nucleus Cochlear Implant Systems

Pediatric clinical trials with the Nucleus 22-channel cochlear implant began in 1986, and in 1990 the FDA approved this device for use in children. The children originally implanted with the Nucleus 22-channel system used the F0F1F2 feature extraction speech-processing strategy. Children implanted after 1989 were provided with the Multipeak (MPEAK) strategy, and the Spectral Peak (SPEAK) strategy was approved in 1994. Pediatric clinical trials for the Nucleus 24-channel device with the SPEAK strategy were initiated in April 1997, and FDA approval was granted in June 1998.

One of the first large-scale reports of pediatric performance with the Nucleus cochlear implant was presented by Staller et al.2 These investigators presented speech perception data from 80 children with the Nucleus 22-channel cochlear implant system who were tested as part of the FDA clinical trials. The mean age at onset of deafness was 2 years, 8 months, and the mean age at implantation was 9 years, 10 months for this group of children. The children's performance was classified by the highest category of speech perception achieved. Comparisons were made between their speech perception performance preimplant and again at 12 months postimplant. After 12 months of cochlear implant use, 63% of children showed significant improvements in the closed-set speech perception tasks and 46% of children demonstrated significant improvements on at least one open-set speech perception task. However, open-set speech abilities were still relatively modest. Similar word-recognition results were reported by Osberger et al.1 for 28 children. Their results demonstrated that the children's speech perception abilities improved significantly after implantation with the largest gains noted when stimuli were presented in the auditory-plus-visual modality (i.e., with visual and lipreading cues). Thus, most children tested with the early Nucleus cochlear implant processing strategies demonstrated at least some open-set word recognition and performance was generally good when both auditory and visual cues were available.

The introduction of newer-generation Nucleus processing strategies yielded greater speech perception benefits in children, just as in adults. Osberger et al.36 compared the performance of six children who used the F0F1F2 processing strategy with that of six children who used the MPEAK strategy. The children in each group were matched by age at onset of deafness and age at implantation. After 1 year of implant use, the children with the MPEAK device were significantly better at discriminating vowel height and consonant place of articulation cues on the Minimal Pairs Test. However, the two groups did not differ after 3 years of cochlear implant use. The authors concluded that children show an accelerated rate of learning with improved speech processing strategies. Similar improvements have been noted for children who switch from the MPEAK to the SPEAK processing strategies.8'12'37 Sehgal et al.12 compared word-recognition scores for children who switched from an earlier processing strategy with the SPEAK processing strategy. These investigators reported mean monosyllabic word recognition scores increased from 28% words correct with the earlier strategy to 58% words correct with the SPEAK strategy.

Clarion Cochlear Implant System

Pediatric clinical trials of the Clarion multichannel cochlear implant system began in 1995, and the device received FDA approval for use in children in 1997. Zimmerman-Phillips et al.38 summarized the initial results of the children's preoperative performance with hearing aids compared with their postoperative performance with the Clarion device. The mean age of the group of children implanted by 1996 was approximately 5 years (n = 124). Data were reported for children tested at 3 months postimplant (n = 60) and 6 months postimplant (n = 23). After only 3 months of device use, mean scores were higher than the preimplant performance, and many of the children demonstrated some open-set speech recognition. By 6 months postimplant, mean word-recognition scores were 23% for the PB-K and 38% for a test of word recognition in a sentence context, the Glendonald Auditory Screening Procedure (GASP).39 In a second study, Osberger et al.11 examined the performance of children implanted with the Clarion device after the age of 5 years who had at least 6 months of device experience (n = 30). The children were divided into two groups based on communication method. After 6 months of device use, children in the oral group correctly identified an average of 27% of the words on the PB-K. The average PB-K word score for children in the total communication group was 8% correct.

Med-El Cochlear Implant System

Pediatric FDA clinical trials for the Med-El device were initiated in 1998. To date, too few children in the United States have used their devices long enough to draw conclusions regarding the benefits to be received by these children.

Summary of Pediatric Results

Children with multichannel cochlear implants demonstrate significant improvements in closed-set speech discrimination and enhanced lipreading ability, and most obtain some open-set speech understanding with their devices. The rate of auditory skills development seems to be increasing as cochlear implant technology improves and cochlear implant candidacy is broadened to include younger children and children with more residual hearing. For example, early studies reported significant increases in the discrimination of nonsegmental speech cues after only 6 months of implant use. However, significant increases in the discrimination of vowel and consonant features were not evident until 1.5 years of cochlear implant experience and auditory-only open-set skills continued to improve long after this time period. More recent studies have shown that many children achieve open-set speech recognition within the first year of device use,10'11 but these skills still continue to develop over time.16'17'36'41'42 In fact, Miyamoto et al.41 noted continued improvements in spoken word recognition even after 5 years of multichannel cochlear implant use. These findings highlight the need to conduct longitudinal studies in order to determine the ultimate benefits of implant use in children.

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