Graeme Clark Collection

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    Speech perception in implanted children: influence of preoperative residual hearing on outcomes [Abstract]
    Cowan, R. S. C. ; Barker, E. J. ; Pegg, P. ; Dettman, S. ; Rennie, M. ; Galvin, K. ; Meskin, T. ; Rance, G. ; Cody, K. ; Sarant, J. ; Larratt, M. ; Latus, K. ; HOLLOW, RODNEY ; Rehn, C. ; Dowell, R. C. ; Pyman, B. ; Gibson, W. P. R. ; Clark, Graeme M. ( 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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    Multichannel auditory brainstem implants: an Australian case study [Abstract]
    Hollow, Rod ; COWAN, ROBERT ; BRIGGS, ROBERT ; KAYE, ANDREW ; DOWELL, RICHARD ; Shaw, Stephanie ; Clarke, Graeme M. ( 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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    Current trends in speech perception performance in adult cochlear implant patients [Abstract]
    Hollow, Rod ; Plant, Kerrie ; Whitford, Lesley ; Skok, Marisa ; DOWELL, RICHARD ; Clark, Graeme M. ( 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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    Speech perception in people with a severe hearing loss: preliminary results [Abstract]
    Flynn, Mark C. ; Dowell, Richard C. ; Clark, Graeme M. ( 1996)
    Recent improvements in multichannel cochlear implants have led to improved speech perception for people with profound hearing impairments. Given this improvement, it has been suggested that some people with severe hearing impairments would be more successful with a cochlear implant than a hearing aid. Unfortunately little research exists to support the suitability of cochlear implants for these individuals. In order to determine this, a detailed investigation of the aided performance of people with severe hearing losses is being conducted at The University of Melbourne (School of Audiology). Severe hearing loss was defined as a pure tone average of greater than 60dBHL, but no worse that 100dBSPL in the better ear. At present, 15 participants have taken part in this study and their results will be discussed. Each participant took part in a standard audiometric assessment which included an audiogram, AB words, tympanometry with acoustic reflexes and an ABR. Each participant’s hearing aids were assessed to make sure that they were optimally aided. Following the hearing aid evaluation the participants took part in a series of traditional speech perception tests which included 24 consonant recognition, 11 vowel recognition, CNC words, CUNY sentences, and the Connected Speech Test (CSTv2). Other tests of speech perception were conducted which looked at the effects of different types of background noise, amounts of reverberation, rates of speech and amount of available context. The aim of this was to better simulate “real-life” listening conditions. Consequently, a range of results for both traditional assessments of speech perception and simulated listening conditions will be presented and compared.
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    Speech perception for hearing aid users versus cochlear implantees [Abstract]
    Flynn, Mark C. ; Dowell, Richard C. ; Clark, Graeme M. ( 1996)
    Abstract not available due to copyright.
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    Speech perception for children with different levels of residual hearing using the cochlear 22-channel cochlear prosthesis [Abstract[
    Cowan, R. S. C. ; Galvin, K. L. ; Barker, E. J. ; Del Dot, J. ; Sarant, J. Z. ; Dettman, S. ; Hollow, R. ; Herridge, S. ; Rance, G. ; Larratt, M. ; Skok, M. ; Dowell, R. C. ; Pyman, B. ; Gibson, W. P. R. ; Clark, Graeme M. ( 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.
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    Signal processing for multichannel cochlear implants: past, present and future [Abstract]
    DOWELL, RICHARD ; SELIGMAN, PETER ; MCDERMOTT, HUGH ; Whitford, Lesley ; BLAMEY, PETER ; Clark, Graeme M. ( 1994)
    Since the late 1970's, many groups have worked on developing effective signal processing for multichannel cochlear implants. The main aim of such schemes has been to provide the best possible speech perception for those using the device. Secondary aims of providing awareness and discrimination of environmental sounds and appreciation of music have also been considered. Early designs included some that attempted to simulate the normal cochlea. The application of such complex processing schemes was limited by the technology of the times. In some cases, researchers reverted to the use of single channel systems which could be controlled reliably with the existing technology. In other cases, as with the Australian implant, a simple multichannel processing scheme was devised that allowed a reliable implementation with available electronics. Over the next 15 years, largely due to the improvements in integrated circuit technology, the signal processors have slowly become more complex. Further psychophysical research has shown how additional information can be transferred effectively to implant users via electrical stimulation of the cochlea. This has lead to rapid improvement in the speech perception abilities of adults using cochlear implants. Some of the main developments in signal processing over the last 15 years will be discussed along with the latest speech perception results obtained with the new SPEAK processing scheme for the Australian 22-channel cochlear implant. Initial results for SPEAK show mean scores of 70% (equivalent to 85-90% phoneme scores) for open set monosyllabic word testing for experienced adult users. Although there remains a large range of performance for all users of cochlear implants, average speech perception scores for all implanted adults have also improved significantly with the developments in signal processing. It appears likely that multichannel cochlear implants will be a viable alternative for the treatment of severe hearing loss in the future.
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    Preoperative residual hearing as a predictor of postoperative speech scores for adult cochlear implant users [Abstract]
    COWAN, ROBERT ; HOLLOW, RODNEY ; DOWELL, RICHARD ; PYMAN, BRIAN ; Clark, Graeme M. ( 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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    Issues in long-term management of children with cochlear implants and tactile devices [Abstract]
    COWAN, ROBERT ; DOWELL, RICHARD ; Barker, Elizabeth ; GALVIN, KARYN ; DETTMAN, SHANI ; SARANT, JULIA ; RANCE, GARY ; Hollow, Rod ; BLAMEY, PETER ; Clark, Graeme M. ( 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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    Cochlear implants in children: unlimited potential? [Abstract]
    DOWELL, RICHARD ; Clark, Graeme M. ( 1994)
    Multichannel cochlear implants have been in use for adolescents for 8 years and for children for 6 years. Due to the substantial benefits obtained by postlinguistically deafened adults using multichannel implants, there was a degree of optimism about the potential benefits for profoundly hearing impaired children using these devices. It was speculated that children may adapt more quickly and learn to use information from implants more effectively than adults. On the other hand, there were cautionary predictions that there may be a "critical age", particularly for congenitally or early deafened children, that, once passed, would preclude effective use of auditory information from implants. This age was variously predicted to be anywhere from 2 to 12 years, based on neurophysiological, developmental or psychological arguments. With some years of experience with implanted children, it can now be said that neither the optimistic nor the more cautionary "critical age" predictions have been supported. As with many areas of clinical science, the situation appears to be far more complex than first thought. This paper will discuss the results obtained for 100 children using the multichannel cochlear implant in Sydney and Melbourne in terms of predictive factors, and the potential for the future application of multichannel cochlear implants in children. The results suggest that experience with implant, the number of years of auditory deprivation, the amount of preoperative residual hearing, and the postoperative educational environment may have a significant effect on speech perceptual abilities in implanted children. In addition, approximately 60% of all implanted children show significant open-set speech perception ability with auditory input alone. It is now possible for multichannel cochlear implants to provide auditory skills sufficient for young children to develop functionally normal speech and language through audition, provided consistent, long term habilitation is available.