Graeme Clark Collection
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ItemContributing factors to improved speech perception in children using the nucleus 22-channel cochlear prosthesis( 1997)It has been established that use of multiple-channel intracochlear implants can significantly improve speech perception for postlinguistically deafened adults. In the development of the Nucleus 22-channel cochlear implant, there have been significant developments in speech processing strategies, providing additional benefits to speech perception for users. This has recently culminated in the release of the Speak speech processing strategy, developed from research at the University of Melbourne. The Speak strategy employs 20 programmable bandpass filters which are scanned at an adaptive rate, with the largest outputs of these filters presented to up to ten stimulation channels along the electrode array. Comparative studies of the Speak processing strategy (in the Nucleus Spectra-22 speech processor), with the previously-used Multipeak (Multipeak) speech processing strategy (in the Minisystem-22 speech processor), with profoundly deaf adult cochlear implant users have shown that the Speak processing strategy provides a significant benefit to adult users both in quiet situations and particularly in the presence of background noise. Since the first implantation of the Nucleus device in a profoundly hearing-impaired child in Melbourne in 1985, there has been a rapid growth in the number of children using this device. Studies of cochlear implant benefits for children using the Nucleus 22-channel cochlear implant have also shown that children can obtain significant benefits to speech perception, speech production and language, including open-set understanding of words and sentences using the cochlear implant alone. In evaluating contributing factors to speech perception benefits available for children, four specific factors are important to investigate: (1) earlier implantation -resulting from earlier detection of deafness; (2) improved hardware and surgical techniques -allowing implantation in infants; (3) improved speech processing, and (4) improved habilitation techniques. Results reported previously have been recorded primarily for children using the Multipeak strategy implemented in the MSP speech processor. While it is important to evaluate the factors which might contribute to improvements in speech perception benefits, an important question is the effect of improved speech processing strategy, since this will determine what is perceived through the device. Given that adult patients changing to the Spectra speech processor had also shown improved perception in noisy situations, and the fact that children are in general in noisy environments in the classroom setting for a large proportion of their day, it was of obvious interest to evaluate the potential for benefit in poor signal-to-noise ratios from use of the Speak processing strategy and from specific training in the ability to perceive in background noise. The study was aimed at evaluating whether children who were experienced in use of the Multipeak speech processing strategy would be able to changeover to the new Speak processing strategy, which provides a subjectively different output. Secondly, the study aimed to evaluate the benefits which might accrue to children from use of controlled habilitation in background noise.
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ItemSpeech perception results for children with implants with different levels of preoperative residual hearing( 1997)Objective: Many reports have established that hearing-impaired children using the Nucleus 22 channel cochlear implant may show both significant benefits to lipreading and significant scores on open-set words and sentences using electrical stimulation only. These findings have raised questions about whether severely or severely-to-profoundly deaf children should be candidates for cochlear implants. To study this question, postoperative results for implanted children with different levels of preoperative residual hearing were evaluated in terms of speech perception benefits. Study Design/Setting: A retrospective study of the first 117 children, sequentially, to undergo implantation in the Melbourne and Sydney Cochlear Implant Clinics was undertaken. All children had been assessed by and received their implants in a tertiary referral centre. Main Outcome Measures: To assess aided residual hearing, the children were grouped into four categories of hearing on the basis of their aided residual hearing thresholds measured preoperatively. To assess benefits, the scores of children on standard speech perception tests were reviewed. As different tests were used for children with different ages and language skills, children were grouped into categories according to the level of postoperative speech perception benefit. Results: The results showed that children in the higher categories of aided preoperative residual hearing showed significant scores on open-set word and sentence perception tests using the implant alone. For children in lower categories of aided residual hearing, results were variable within the groups. More than 90% of children with implants with aided residual hearing thresholds in the speech range above I kHz achieved open-set understanding of words and sentences. Conclusion: While the results of this preliminary study confirm previous findings of differential outcomes for children with different levels of preoperative residual hearing, they suggest that children with severe to profound hearing impairments should be considered for cochlear implantation.
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ItemSpeech perception in implanted children: influence of preoperative residual hearing on outcomes [Abstract]( 1998)Since the first child was implanted with the Nucleus 22-channel prosthesis in Melbourne in 1985, several thousand children world-wide have now benefitted from this technology. More effective paediatric assessment and management procedures have now been developed, allowing cochlear implants to be offered to children under the age of 2 years. Improvements in speech processing strategy have also been implemented in the Nucleus implant system, resulting in increased mean speech perception benefits for implanted adults. Although a range of performance on formal measures of hearing, speech or language has been reported for children using implants, results from the first decade of implant experience consistently show that significant benefits are available to children receiving their implant at an early age. Reported speech perception results for implanted children show that a considerable proportion (60%) of paediatric patients in the Melbourne and Sydney clinics are able to understand some open-set speech using electrical stimulation alone. These results, and the upward trend of mean speech perception benefits shown for postlinguistically deafened adults have raised questions as to whether severely, or severely-to-profoundly deaf children currently using hearing aids would in fact benefit more from a cochlear implant. To investigate the potential influence of the degree of preoperative residual hearing on postoperative speech perception, results for all implanted children in the Melbourne and Sydney cochlear implant programs were analysed. Results showed that as a group, children with higher levels of preoperative residual hearing were consistently more likely to achieve open-set speech perception benefits. Potential factors in this finding could be higher levels of ganglion cell survival or greater patterning of the auditory pathways using conventional hearing aids prior to implantation. Conversely, children with the least preoperative residual hearing were less predictable, with some children achieving open-set perception, and others showing more limited closed-set benefits to perception. For these children, it is likely that preoperative residual hearing is of less significance than other factors in outcomes.
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ItemThe progress of children using the multichannel cochlear implant in Melbourne( 1995)Multi-channel cochlear implantation in children began in Australia in 1985 and there are now close to 4000 profoundly deaf children and adolescents using the Australian implant system around the world. The aim of the implant procedure is to provide adequate hearing for speech and language development through auditory input. This contrasts with the situation for adults with acquired deafness where the cochlear implant aims to restore hearing for someone with well-developed auditory processing and language skills. As with adults, results vary over a wide range for children using the Multi-channel implant. Many factors have been suggested that may contribute to differences in speech perception for implanted children. In an attempt to better understand these factors, the speech perception results for children implanted in Melbourne were reviewed and subjected to statistical analysis. This has indicated that the amount of experience with the implant and the length of sensory deprivation are strongly correlated with perceptual results. This means that younger children are likely to perform better with an implant and that a number of years of experience are required for children to reach their full potential. The results have also indicated that educational placement and management play a crucial role in children reaching their potential. Overall, 60% of the children and adolescents in the study have reached a level of open-set speech understanding using the cochlear implant without lipreading.
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ItemPreoperative residual hearing as a predictor of postoperative speech scores for adult cochlear implant users [Abstract]( 1994)The development of multiple channel cochlear implants has been a significant advance in the rehabilitation of profound hearing loss. Speech perception benefits have been particularly evident for postlinguistically deafened adults, who as a group have shown not only supplementation of lipreading scores but also significant comprehension of words and sentences using an implant alone, without the aid of lipreading. In many cases, patients are able to use their implant for telephone conversation. Speech perception benefits for adult users have increased with advances in speech processing and improved means of habilitation. These improvements in open-set speech benefits for adult users have resulted in a steady increase in group mean scores and a reevaluation of selection criteria for cochlear implantation. In the initial development of cochlear implants, only those with little or no residual hearing were considered as candidates. Current selection criteria now include those with substantial residual hearing, who may score up to 40% in the best-aided condition on word and sentence speech perception tests. In order to provide realistic expectations for prospective cochlear implant patients, it is important to establish the relationship of many preimplant factors to postimplant speech perception benefits. For severely hearing impaired adults, the relationship between preoperative residual hearing, as measured by aided word and sentence speech perception test scores, and postoperative speech perception benefits is of significant interest. Analysis of data collected over a 15 year period for adult patients is presented. The rationale for conducting full speech perception assessments for all potential cochlear implant patients is stressed.
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ItemIssues in long-term management of children with cochlear implants and tactile devices [Abstract]( 1994)For many children with severe and profound hearing losses, conventional hearing aids are unable to provide sufficient amplification to ensure good oral communication and/or in the case of very young children, development of speech and language. Traditionally a number of these children have opted for the use of sign language alone or in Total Communication approaches as a primary means of communication. The advent of multiple channel cochlear implants for children and the continuing development of multiple channel speech processing tactile devices provide auditory approaches to resolving communication difficulties for these children. The successful use of such devices depends on a number of factors including the information provided through the aid; the ease of use, convenience and reliability of the aid; the individual communication needs of the child; and the habilitation and management program used with the device. Long-term data has shown that children continue to show increased speech perception benefits from improvements in speech processing and from further experience with these devices. Habilitation and management programs must therefore be geared to meet the changing needs of children as they progress and of families as children mature and face new challenges. Habilitation must address specific individual needs in speech perception and in speech production. For very young children, benefits of improved speech perception should have an impact on the development of speech and language, and habilitation and management must emphasise the need for language growth.
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ItemHabilitation issues in the management of children using the cochlear multiple-channel cochlear prosthesis(Wien, 1994)Since 1985, a significant proportion of patients seen in the Melbourne cochlear implant clinic have been children. The children represent a diverse population, with both congenital and acquired hearing-impairments, a wide-range of hearing levels pre-implant, and an age range from 2 years to 18 years. The habilitation programme developed for the overall group must be flexible enough to be tailored to the individual needs of each child, and to adapt to the changing needs of children as they progress. Long-term data shows that children are continuing to show improvements after 5-7 years of device use, particularly in their perception of open-set words and sentences. Habilitation programs must therefore be geared to the long-term needs of children and their families. Both speech perception and speech production need to be addressed in the specific content of the habilitation program for any individual child. In addition, for young children, the benefits of improved speech perception should have an impact on development of speech and language, and the focus of the programme for this age child will reflect this difference in emphasis. Specific materials and approaches will vary for very young children, school-age and teenage children. In addition, educational setting will have a bearing on the integration of listening and device use into the classroom environment.
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ItemEvaluation of direct and indirect benefits in the selection of cochlear implant candidates [Abstract]( 1998)The value of cochlear implants as an established clinical option for profoundly hearing-impaired adults and children has been supported by significant research results over a number of years which clearly established the benefits available (U.S. National Institutes of Health Consensus Statement 1995). Benefit has traditionally been considered as the impact of the cochlear implant procedure on hearing, and in the case of children, on the use of that hearing to develop speech and language. However, as a result of continuing research, improvements have been realised both in hardware and speech processing. As a direct consequence of these improvements, the mean open-set implant-alone speech perception scores for implanted adults have continued to increase. In response to the increased mean scores shown by adult cochlear implant users in quiet, perception tests in background noise are now being used as a direct measure of the potential benefits of cochlear implants available to severely-to-profoundly hearing-impaired candidates. In addition, consideration in candidature should also be given to indirect benefits, such as reduction in the stress. of listening and lipreading, improved performance at work, enhanced opportunity to maintain or in children to develop speech which is understandable to the general community, and the social effects of reducing the isolating effects of profound deafness. Measurement of indirect benefit can be combined with a costing study, enabling evaluation of the implant procedure from a cost-utility standpoint, and comparison of outcomes using other technologies such as hearing aids. The use of new approaches to candidature, including new measures of direct and indirect benefit is reported using data from the Melbourne cochlear implant program.
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ItemCurrent speech perception benefits for adults using the speak strategy with the nucleus 22-channel cochlear implant( 1997)Present day recipients of the Nucleus 22-channel cochlear implant make use of the SPEAK speech processing strategy in the Spectra 22 speech processor. Introduced in 1994, the SPEAK strategy is based upon research conducted at the University of Melbourne and the Bionic Ear Institute. This paper compares the pre-and post-operative speech perception abilities of adults who have used the SPEAK speech processing strategy since the 'start-up' of their cochlear implant system. Data was analysed from open-set sentence and word tests administered pre-operatively and at regular intervals postoperatively. Patients showed significant improvement in their ability to recognise speech, when listening with the cochlear implant without lipreading, within the first two weeks. Mean scores for open-set sentences were 15% preoperatively and 64% two weeks after initial programming.
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ItemSpeech perception in implanted children: effects of speech processing strategy and residual hearing(Mendoza Editor, 1997)The ability of implanted children to adapt to different speech processing strategies has been demonstrated for the Nucleus implant system. Children previously experienced with the Multipeak speech processing strategy. were able to gain significant improvements in consonant, word and sentence perception using the Speak speech processing strategy. suggesting some degree of neural plasticity in neural-auditory coding. Of 192 implanted children with different degrees of preoperative residual hearing, 65% were found to obtain significant scores on open-set speech materials using electrical stimulation alone. Those children with more residual hearing had a greater probability of achieving open-set understanding and at a minimum level, perceived high frequency consonant information which would not have been available through conventional hearing aids.