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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ItemIs age at cochlear implantation in children important? A 2-deoxyglucose study in cats.( 1997)Should one implant prelinguistically deaf children at the earliest possible age or is it better to wait a couple of years? In normally hearing kittens functional auditory development is completed, up to the level of the inferior colliculus (IC), by 30 days after birth (DAB) [1]. However, in deaf kittens stimulation with a cochlear implant can alter the IC map even at ages up to 120 DAB [2]. In normally hearing children the auditory brainstem response approximates the adult form by the age of 2 years. Studies of deaf children with cochlear implants have indicated that implantation by the age of 5-6 yields a high success rate. We implanted neonatally deafened kittens at different ages, stimulated them for long periods, then looked at the spread of 2-deoxyglucose (2-DG) in the IC. If age is a factor in plasticity in deaf cats, then the distribution of 2-DG uptake should vary with age at implantation.
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ItemEngineering(Singular Publishing, 1997)The last two decades have seen major advances in cochlear implants for profoundly deaf people. Implants are now used by severely to profoundly deaf adults and children in almost every phase of daily life. They have become an established treatment, and today's expectations for all aspects of the cochlear implant system are much greater than they were for the experimental devices of the early 1980s. Hardware designs have improved to meet clinical and research demands, technological developments have made the devices smaller and more reliable, and speech processing research has yielded a series of improvements in patient benefit.
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ItemThe Melbourne Cochlear Implant Clinic program(Singular Publishing, 1997)The Melbourne Cochlear Implant Clinic program involves a multidisciplinary clinical team, collaborating with those engaged in more fundamental research, and with the biomedical company Cochlear Limited. This chapter reflects the contributions of many professionals to managing children with cochlear implants.
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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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ItemIntroduction(Singular Publishing, 1997)From the time single-channel cochlear implants were first implanted in children in the early 1980s in Los Angeles (Laxford et al 1987) closely followed in 1985 by the multiple-channel cochlear implant in Melbourne (Clark et al 1987a, 1987b) there has been a considerable expansion in the work to apply the multiple-channel cochlear implant to infants and young children.
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ItemHistorical perspectives(Singular Publishing, 1997)Initial attempts to help profoundly deaf people understand speech by electrically stimulating the auditory nerve commenced in the 1950s and 1960s (Djourno & Eyrtes. 1957; Doyle. Doyle. &Turnbull. 1964; House. Berliner. Crary. Graham. Luckey. Norton. Selters. Tobin Urban & Wexler. 1976; Simmons. Monegeon. Lewis. & Huntington. 1964). The procedures were carried out on isolated patients. Raw or filtered speech was presented to the electrodes but no speech understanding was obtained.
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ItemEthical issues(Singular Publishing, 1997)The ethics of cochlear implantation in infants and children is an important issue which has received a lot of attention, in particular from the signing deaf community and their advocates. Many of the issues raised by the signing deaf community are in regard to human experimentation and are therefore ethical in nature. Others are concerned with whether it is natural to have a hearing loss, and this goes beyond the realm of ethics. This chapter examines cochlear implantation in children in light of generally accepted ethical principles.
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ItemEpilogue(Singular Publishing, 1997)Cochlear implantation in children has made considerable progress in the last decade, and it is now an established clinical procedure. Together with cochlear implants for adults, it could be said to have reached the stage of being a subdiscipline in otology. It is truly an interdisciplinary field where surgery, audiology, speech-language pathology, education, engineering, and the biological sciences continue to make essential contributions. Like any interdisciplinary field, the best patient management and future progress will occur when there is maximal exchange of information and expertise between these disciplines.