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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ItemSurgery(Singular Publishing, 1997)Cochlear implant surgery should be undertaken only after the cochlear implant team has established that the child is not achieving useful communication with a hearing aid. This can be difficult because of poor language development in deaf children in this age group or because the child is at a preverbal stage and too young for the use of formal assessment tests. The child's unaided and aided thresholds, however, are important for assessment, as are his or her communication skills. These need to be evaluated by an experienced paediatric audiologist.
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ItemPreoperative medical evaluation(Singular Publishing, 1997)The aim of the medical assessment of infants and children is to determine the cause, severity and duration of any hearing loss as well as the presence of any medical conditions that may influence their management with a cochlear implant. There should also be an initial assessment of the child's communication skills and the parental expectations for his or her education.
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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.
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ItemChronic middle ear disease and cochlear implantation( 1995)Profound or total hearing loss can occur in the setting of chronic suppurative otitis media (CSOM), either coincidentally or secondary to the disease process. Obviously, inserting a foreign body through a potentially infected field into a space that communicates intracranially presents a challenging management problem. This paper presents the experience from the Melbourne Cochlear Implant Clinic (CIC) in implanting patients with bilateral CSOM. This is certainly not a common problem, as there have been only 3 cases from 121 implanted adults. However, we feel that it is an important issue with potentially devastating consequences. In addition, there are many countries in which bilateral CSOM is a more common problem and cause of profound or total hearing loss.
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ItemSurgical considerations for the placement of the new Cochlear Pty Limited micro-multiple-channel cochlear implant for research studies( 1995)A new micro-receiver-stimulator for research studies on very young children as well as adults has been developed by Cochlear Pty Limited. The dimensions of the device are length 58 mm and width at front 18 mm. The width starts to increase 19 mm from the front, and the back section, which has the receiver coil and magnet, has a maximum diameter of 33 mm. The depth or thickness of the front portion of the electronic package is 5.7mm, and the remainder of the package 4.0 mm. The antenna section is 3.5 mm thick. The other dimensions of the front section of the electronic package are length 9.5 mm and width 13.7 mm. There is an angle of 160° between the titanium electronic package and the receiver coil. The dimensions of the receiver-stimulator were arrived at after anatomic studies on the temporal bones of children ranging in age from 2 to 11 months.
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ItemImplantation of the new nucleus C1-3 receiver stimulator and electrode array [Abstract]( 1997)There is an important need to fix the cochlear implant electrode array at a site close to the cochlea, so that the electrode will not slide out, or be subject to differential movement with growth changes. Fixation sites have been in the region of the posterior root of the zygoma and the floor of the antrum. Fixation has been by Dacron mesh ties platinum wire ties, or clips inserted with-special instruments. Biological cements have previously been tried but found to be toxic. The most ideal site is in the region of the cochleostomy.
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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.
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ItemSpeech perception in implanted children: effects of preoperative residual hearing and speech processing strategy [Abstract]( 1997)Since the first child was implanted with the Nucleus 22-channel cochlear prosthesis in Melbourne in 1985, the number of implanted children world-wide has rapidly expanded. Over this period, more effective paediatric assessment and management procedures have developed, allowing cochlear implants to be offered to children under the age of 2 years. In addition, a succession of improved speech processing strategies have been implemented in the Nucleus implant system, resulting in increased mean speech perception benefits for implanted adults. Research in the Melbourne and Sydney Cochlear Implant Clinics has also demonstrated that young children can adapt to and benefit from improved speech processing strategies such as the Speak strategy. 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 speech perception benefits to improve over time with advances in speech processing. 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 effect of the level 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 8 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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ItemImplantation of the new CI-24M Cochlear Limited receiver-stimulator and its electrode array(Monduzzi Editore, 1997)Cochlear Limited has released the new CI-24M model Nucleus 24 electrode cochlear implant system encompassing a series of new features. It offers the potential for improvements in hearing and cosmesis, as well as telemetry.