Cochlear implants: 100 pediatric case conversions from the body worn to the nucleus esprit 22 ear level speech processor.

OBJECTIVE: To assess performance of Nucleus 22 mini system pediatric users converted from the Spectra 22 body-worn to the ESPrit 22 ear-level speech processor using aided thresholds and speech discrimination measures before and after the conversion. STUDY DESIGN: Spectra 22 body-worn speech processor users were chosen using preselection criteria (stable map, ability to report on the quality of the signal, no device problems). The subjects underwent tuning, map conversion, fitting of the ESPrit 22, and aided soundfield threshold and speech discrimination testing. SUBJECTS: The first 100 consecutive conversions are analyzed in this study. Fifty children (50%) were female, and 50 (50%) were male. The average age at implantation was 4.6 years (median 4.3 years, range 1.7 to 11 years). The average age of fitting the ear level speech processor was 11.1 years (median 11 years, range 6.2 to 18.2 years). SETTING: Tertiary referral pediatric cochlear implant center in the United Kingdom. RESULTS: Of the 100 fittings attempted, all Spectra 22 maps could to be converted for use in the ESPrit 22. Of these 100 fittings, 44 were straightforward with no adjustment to map parameters being required, and 56 needed rate reductions and other map adjustments to achieve the conversion. The difference of the mean thresholds before and after the conversion did not exceed 2 dB across the frequencies studied (0.5-4 kHz). In 95% of the cases, the differences were less than 9 dB(A). With regard to speech discrimination testing, the mean threshold before the conversion was 53.4 dB and after the conversion 52.7 dB. Of the 100 conversions, only five children stopped using the ESPrit 22 despite fitting being achieved. CONCLUSION: Conversion from the Spectra 22 body worn to the ESPrit 22 ear level speech processor was found to be feasible in all the 100 cases studied. Only a minority (5%) of children chose not to use the ear level speech processor suggesting that children and parents were satisfied from the conversion.

Retrospective study of intra-operative testing with the Nucleus CI24M cochlear implant and use of the back-up device.

The combined use of integrity testing (IT) and impedance telemetry (ImTe) intra-operatively is evaluated. One hundred and fifty children implanted with the Nucleus device were studied. In 81% of patients, normal results were obtained on all electrodes from both ImTe and IT. In seven cases where the back-up device was used, the intra-operative analysis of the device and subsequent postoperative quality assurance testing did not always correlate. In conclusion, intra-operatively, only ImTe is needed to verify the function of the implant if all impedance values are normal. However, in the case of abnormal ImTe results, additional IT data provide valuable assistance with the decision of whether to leave the implant in place or to use the backup device.

Intra-operative recordings of electrically evoked auditory nerve action potentials in young children by use of neural response telemetry with the nucleus C124M cochlear implant.

The electrically evoked action potential (EAP) was recorded intra-operatively by use of neural response telemetry (NRT) on the Nucleus C124M cochlear implant. The aim of the present study was to investigate the EAP in young children immediately following implant surgery and whilst the children were still anaesthetized. The effect of data collection parameters on the reliability of the EAP was assessed and the relationships of the EAP findings to the intra-operative electrical auditory brainstem response (EABR) and early behavioural threshold levels (T-levels) were also investigated. The study data comprised intra-operative recordings in 60 children. Age at implantation was less than five years in 42 (70%) of the children. Aetiology of deafness was congenital in the majority of children (55, 92%), meningitic in four children and of unknown origin in one child. Optimum test parameters for the intra-operative EAP were an amplifier gain of 40 dB and a delay of 50 micros in order to minimize the effects of amplifier saturation due to stimulus artefact and to maximize the identification of the N1 component. An intra-operative protocol was established which involved recording four stimulus levels on each of the 22 electrodes of the electrode array, the range of stimulus levels being tailored towards the expected EAP thresholds and T-levels so as to identify response threshold. There was significant correlation between the intraoperative EAP thresholds and the early T-levels (Pearson's r = 0.93 ;p<0.01) when a correction factor was introduced based on a reliable behavioural measure of the threshold of electrical stimulation on electrode 10. The intra-operative EAP threshold, when combined with a limited amount of behavioural data, may therefore be used to predict the T-level with a useful degree of accuracy. This result is also supported by the significant correlation observed between the intra-operative thresholds of the EAP and EABR.

Assessment of aided ABR thresholds before cochlear implantation.

The Nottingham Paediatric Cochlear Implant Programme (NPCIP) specializes in the cochlear implantation of children under the age of 5 years. The initial stage in the pre-implant evaluation process is audiological assessment. In complex paediatric cases, behavioural audiological assessment may be difficult. In such cases, an objective measure to verify the aided hearing threshold is desirable. This study compares unaided and aided hearing thresholds, by both objective and behavioural techniques, in 20 children (aged <1-10 years). Objective data were collected from auditory brainstem responses (ABR) and behavioural thresholds were measured by use of developmental age-appropriate tests. When comparing the unaided ABR click threshold to the behavioural threshold (obtained from the average of 1-4 kHz warble tones) the ABR threshold was, on average, 9 dB lower (more sensitive). Using the same comparison for aided responses a difference of <5 dB was observed. Unaided ABR thresholds resulted in 35% of subjects responding to the click stimulation (when using a maximum stimulation level of 105 dB nHL), whereas introducing aided ABR measurement elicited positive results in 75% of subjects. The effect of the hearing aid on the stimulus was measured by use of a 2 cc coupler which was connected to a precision sound level meter, whose AC output was recorded onto digital audiotape. Analysis of the resultant output spectra in the frequency domain highlighted signal non-linearity and distortion when using high-intensity stimuli with moderate to high aid gains. In conclusion, aided ABR thresholds are valuable in the management of young children. However, when performing either ABR or behavioural aided hearing threshold measurements it is essential to be aware of the limitations of the hearing aid and the stimulus.

Audit of 5-year post-implantation routine integrity tests performed on paediatric cochlear implantees.

The Nottingham Paediatric Cochlear Implant Programme (NPCIP) specializes in the implantation of children under 5 years of age. Subsequent tuning of the device and identification of changes in device function for these young children, who may have additional disabilities, can often be challenging. Thus, an objective measure to assess the integrity of the device is desirable. This study compares the device function by both objective and behavioural techniques in 30 children (age at implantation 3-11 years) at five years post-implantation. All children were implanted with the Nucleus Mini 22 device. Objective data were collected from integrity testing (IT) which allowed examination of the functioning of the implant by measuring the electrical stimulus artefact. This does not require the child to give a behavioural response. A protocol for a five-year post-implantation IT is suggested which examines common ground, monopolar and bipolar modes of operation. Behavioural data in the form of threshold (T) and comfort (C) levels were obtained by use of developmental age-appropriate techniques at 5 years post-implantation. Results demonstrate that 43.3% of patients had no electrode faults, 23.3% had potential faults on both behavioural and integrity testing, 6.7% were difficult to assess in terms of defining electrode faults due to partial electrode insertions, 13.3% had potential faults on behavioural testing only and 13.3% of patients had potential faults on IT only. In conclusion, IT is valuable in the identification of faulty electrodes, especially in young children and those with additional disabilities. Implementation of the five-year routine IT affected the management of 30% of patients. This study demonstrates that objective and behavioural techniques are complementary procedures in the ongoing management of paediatric patients.

Early experience with the cochlear ESPrit ear-level speech processor in children.

The ESPrit ear-level speech processor has recently become available in the United Kingdom for use with the Nucleus CI24M multichannel cochlear implant. We report on the use of this ear-level processor with 6 children, ages 8 to 15 years. In this study, all patients were initially fitted with the SPrint body-worn processor, this being a prerequisite for programming the ESPrit. Five of the children were fitted successfully with the ESPrit and are using their devices consistently. The results show that patient experience with the ESPrit has been favorable, although there have been some device and programming difficulties. Aided threshold measures show that the ESPrit processor performs at least as well as the SPrint processor, with a trend toward improved aided thresholds for the ESPrit processor compared with the SPrint processor. Further study of the functional benefit of both of these devices may confirm these potential gains. The ESPrit device currently has a disadvantage for children in that it does not support FM radio hearing aid use. Finally, caution is advised in the fitting of the ESPrit in very young children or inexperienced listeners, because of difficulties in monitoring device function.

Analysis of records from an open-access audiology service.

Despite growing awareness of the importance of early detection of hearing problems in children, surveys undertaken in recent years have consistently demonstrated late detection. In an attempt to improve this, Nottingham Health Authority started an open-access child audiology service to cover the 1 million population of Nottinghamshire. The records of the first 2000 cases referred to the new centre have been analysed in terms of audiological outcome. The findings are presented in a form which offers useful guidelines for service planning elsewhere.