The influence of potentially limiting factors on paediatric outcomes following cochlear implantation.

OBJECTIVE: Children with isolated hearing impairment who have received cochlear implant at the optimal age mostly achieve remarkable results that are assessed by objective speech perception and production measurements. Different outcomes may be expected in case of conditions which may have a negative impact on postoperative performance. The aim of this study was to assess the influence of potentially limiting factors on postimplant outcomes. METHODS: Four groups of examinees (11 in total) were involved by the study: (A) four children with additional disabilities, (B) three children with cochlear malformation and/or ossification, (C) three reimplanted children, (D) a child with retrocochlear (cochlear nerve) pathology. Hearing, speech perception and production were examined by pure tone audiogram, speech audiogram, categories of auditory performance, speech intelligibility rating, listening progress profile, and monosyllabic trochee polysyllable test. Postoperative positive life changes were assessed by a questionnaire. RESULTS: Group A: perception skills better than expected, less satisfactory speech development. Group B: good sound perception, poor understanding. Group C: after reimplantation undisturbed conditions for continuation of optimal rehabilitation course. Group D: unsatisfactory results of pure tone hearing as well as speech perception and production. CONCLUSION: In spite of unfavourable conditions all examinees, except a child with retrocochlear pathology, were found to have a considerable benefit after cochlear implantation (with regard to obvious heterogeneity within each group). Evaluation of success, especially in children with multiple handicaps, also has to include subjective indicators of positive life changes, even those not directly associated with hearing.

Differences between electrically evoked compound action potential (ECAP) and behavioral measures in children with cochlear implants operated in the school age vs. operated in the first years of life.

OBJECTIVE: The aim of this study was to identify the differences in the NRT measures, behavioral measures, and their relationship between the group of congenitally deaf children operated in the first years of life and the group of children operated in the school age. METHODS: The study included 40 congenitally deaf children with cochlear implants divided into two groups. Group 1 was composed of 20 children (mean age at operation 2.3 years, range 1.4-4.6 years) and Group 2 was composed of 20 children (mean age at operation 11.3 years, range 7.0-17.1 years). The ECAP was recorded using the Nucleus 24 neural response telemetry (NRT) system. In each child, the responses were evoked by the apical, middle and basal electrodes. The analyzed parameters were: the ECAP threshold (T-NRT), N1P2 amplitude, N1 latency, slope of the amplitude growth function, response morphology, threshold (T-) level, maximum comfort (C-) level, dynamic range (DR), T-NRT as a percentage of the map DR, the correlation between the T-NRT and the T- and C-levels. The recordings of parameters were performed two years after implantations. RESULTS: The T-NRT, DR, T-NRT as a percentage of the map DR and the correlation between T-NRT and C-levels were significantly different between both groups of children. There were no statistically significant differences between the groups with respect to the amplitude, latency, slope and morphology recorded using the same electrodes. However, intragroup differences regarding NRT measures and behavioral measures with respect to the position of stimulating electrode were more prominent in Group 2 than in the Group 1. CONCLUSIONS: Results of this study have also found a great variability of NRT and MAP measures within and across patients in both groups of children, but it was still more pronounced in the group of school children. NRT profile across electrodes follows MAP profiles better in the Group 1 then in the Group 2. Overall findings of NRT and MAP measures are not consistent and unambiguous as we expected, but still suggest potential differences between results in children operated in first years of life, and those operated in school age.

Acoustic analysis of the speech of children with cochlear implants: a longitudinal study.

The aim of the study was to analyse the speech of the children with cochlear implants, and compare it with the speech of hearing controls. We focused on three categories of Croatian sounds: vowels (F1 and F2 frequencies), fricatives (noise frequencies of /s/ and /S/ ), and affricates (total duration and the pattern of stop-fricative components in /ts/ and /tS/ ). Eighteen implanted children, aged between 9;5 and 15;2 years participated in the study. All had been profoundly hearing impaired before implantation. Three recordings per child were made over a 20-month period. The hearing controls were matched for age and sex. Implanted children had a smaller and fronted vowel space, their /s/ and /S/ noise frequencies overlapped, affricates were longer, with a high proportion of incorrect productions and substitutions. With time, there was a small but steady overall improvement in all categories. Early intervention (rehabilitation and implantation) are crucial for good speech acquisition.

Speech perception of children with cochlear implants and children with traditional hearing aids.

The aim of the study was to analyse speech perception of children with cochlear implants (N = 29) and children fitted with traditional hearing aids (N = 20). One- and two-syllable words were presented auditorily in a forced choice minimal-pair discrimination task. The children repeated the word and pointed to the appropriate picture presented on computer screen. The words were minimal pairs with respect to voicing or place of articulation in stops and fricatives; among affricates the minimal pairs included the most frequently substituted fricatives and stops in addition to voicing and place of articulation. Vowel discrimination was tested in minimal pairs and in nonsense words differing only in the vowel. Unaided, all children were profoundly hearing impaired and were included in auditory-oral therapy (Verbotonal method). The smallest differences between the groups were found for stops and vowels, and the largest for fricatives and affricates. The implanted children were significantly more successful.