Graeme Clark Collection
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ItemHearing restoration with the multichannel auditory brainstem implant( 1997)Restoration of useful hearing is now possible in patients with bilateral acoustic neuromas by direct electrical stimulation of the cochlear nucleus. Our first experience with the Multichannel Auditory Brainstem Implant is reported. A forty four year old female with bilateral acoustic neuromas and a strong family history of Neurofibromatosis Type II presented with profound bilateral hearing impairment. Translabyrinthine removal of the right tumour was performed with placement of the Nucleus eight electrode Auditory Brainstem Implant. Intraoperative electrically evoked auditory brainstem response monitoring successfully confirmed placement over the cochlear nucleus. Postoperatively, auditory responses were obtained on stimulation of all electrodes with minimal non-auditory sensations. The patient now receives useful auditory sensations using the "SPEAK" speech processing strategy. Auditory brainstem Implantation should be considered for patients with Neurofibromatosis Type II in whom hearing preservation tumour removal is not possible.
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ItemThe effect of language ability and residual hearing on speech perception outcomes for older children using multichannel cochlear implants [Abstract]( 2002)Early-deafened teenagers or young adults have shown somewhat disappointing performance with cochlear implants in the past, however, in recent years a proportion of older children have demonstrated excellent speech perception performance. There is a great deal of variability in speech perception performance within this group. It is important to investigate the factors influencing performance so that adolescents and their families can make informed decisions regarding cochlear implant surgery. This study considered a number of possible predictive factors in a group of 25 children implanted in Melbourne between the ages of 8 and 18 years. Subjects completed open set speech perception testing using BKB sentences both pre-and postoperatively, and pre-operative language testing using the Peabody Picture Vocabulary Test. Data were collected regarding the type of hearing loss, age at implant, age at hearing aid fitting, audiometric details, and the pre-and post-operative communication mode. Multivariate analysis suggested that three factors were associated with postoperative speech perception performance. Results were improved for subjects with better pre-operative speech perception, better pre-operative language ability, and when the duration of profound hearing loss was shorter. These three factors accounted for 66% of the variance in this group. The results of this study suggest that children who have useful pre-implant speech perception, and higher age-equivalent scores on language measures, would be expected to do well with a cochlear implant. A shorter duration of profound hearing loss is also advantageous. Mean speech perception scores for the older group were not significantly different from younger children.
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ItemThe effects of post-implant habilitation on long-term outcomes for children using multichannel cochlear implants [Abstract]( 2002)Those working in the cochlear implant field advocate a regular habilitation program for young children receiving implants. Developing auditory skills and the incorporating these into general language development are considered to be key areas for such programs. Investigations of speech perception and language outcomes have demonstrated that the emphasis of spoken language development appears to enhance the results for implanted children. It remains difficult, however, to demonstrate the effect of habilitation as a separate factor and to determine how much individual attention is desirable for each child. This preliminary study considered the long term speech perception and language outcomes for two groups of children who received Nucleus cochlear implants in Melbourne. The first group (n = 17) was identified as receiving regular habilitation from the Melbourne Cochlear Implant Clinic over a four year post-operative period. A second group (n = 11) was identified as receiving very little regular habilitation over the post-operative period. Language and speech perception results for these two groups showed significant differences in performance on a wide range of measures. The group who received regular, formal habilitation demonstrated better performance on all measures. These groups included only congenitally, profoundly hearing- impaired children and did not differ significantly on mean age at implant or experience at the time of assessment. A more comprehensive study is needed to clarify these results on a larger group of children, and to control for additional confounding variables. Nonetheless, these results provide support for the incorporation of regular long-term habilitation into cochlear implant programs for children.
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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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ItemMultichannel auditory brainstem implants: an Australian case study [Abstract]( 1996)The multichannel Auditory Brainstem Implant (ABI) is an implantable device designed to restore a level of auditory perception in patients with bilateral acoustic neuromas, where the removal of the tumours is expected to result in a total loss of hearing. As with the cochlear implant, the ABI utilises an externally worn speech processor and headset, together with a surgically-placed receiver-stimulator and electrode array. The electrode array, developed through the collaboration of the House Ear Institute in the United States and Cochlear Corporation, consists of eight electrodes on a carrier, which is placed on the surface of the brainstem in the area of the cochlear nucleus.
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ItemCurrent trends in speech perception performance in adult cochlear implant patients [Abstract]( 1996)In 1994, Cochlear Pty. Ltd. (Now Cochlear Limited) released a new speech processor, the Spectra 22, for use with the Nucleus 22-channel cochlear implant. The Spectra 22 speech processor incorporates a new speech processing strategy called SPEAK, which is based upon research conducted by the University of Melbourne. This paper reports post-operative scores on open-set word and sentence materials for adult patients in the Melbourne Cochlear Implant Clinic who have been started up with the Spectra 22 speech processor.
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ItemComponents of a rehabilitation programme for young children using the multichannel cochlear implant(Whurr, 1996)Rehabilitation with young hearing-impaired children may be defined as a teaching; learning process where the role of the clinician is to facilitate acquisition of listening, speech and language in a normal developmental order. This is often referred to as habilitation. It differs from rehabilitation for adults, which is the process by which lost communication skills are reacquired. It is worth discussing the role of the cochlear implant as a tool in this process. For the adult with acquired hearing loss, the cochlear implant might be expected, in part, to facilitate rehabilitation by restoring the auditory sense. The aim is to facilitate speech reception and provide the adult with a speech feedback loop. For a child receiving the cochlear implant, the aims are more complex. The device needs to provide speech perception abilities to facilitate the development of the entire linguistic system, to develop a range of speech sounds, to enable speech monitoring via auditory feedback and to access shared knowledge of the world. (From Introduction)
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ItemSpeech perception for children with different levels of residual hearing using the cochlear 22-channel cochlear prosthesis [Abstract[( 1996)Over the past 10 years, since the implantation of the first children with the Nucleus 22-channel cochlear prosthesis in Melbourne, the number of profoundly deaf children using this implant system has rapidly expanded. Longer-term experience with implanted children has led to improvements in paediatric assessment and management. Speech processing strategies have also been improved, resulting in a series of increases in speech perception benefits. Results of comparative studies of Speak and Multipeak speech processing strategies have shown that open-set word and sentence scores for a group of thirteen children evaluated over a two year period showed an advantage with the Speak speech processing strategy. The increases were noted particularly in speech perception in poor signal-to-noise conditions. Analysis has shown that consonant perception was significantly increased, due to an improved place perception. Given current speech perception scores for implanted children, it has been suggested that severely-to-profoundly deaf children currently using hearing aids could in fact benefit more from a cochlear implant. Preliminary investigation of results for children in the Melbourne and Sydney cochlear implant programs has shown that children with higher levels of preoperative residual hearing as a group do score significantly on open-set word and sentence perception tests using the implant alone. In children with lower levels of residual hearing, results were variable across the group.