Graeme Clark Collection
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ItemComparison of electrode position in the human cochlea using various perimodiolar electrode arrays( 2000)Objective: This study was conducted to evaluate the insertion properties and intracochlear trajectories of three perimodiolar electrode array designs and to compare these designs with the standard Cochlear /Melbourne array. Background: Advantages to be expected of a perimodiolar electrode array include both a reduction in stimulus thresholds and an increase in dynamic range, resulting in a more localized stimulation pattern of the spiral ganglion cells, reduced power consumption, and, therefore, longer speech processor battery life. Methods: The test arrays were implanted into human temporal bones. Image analysis was performed on a radiograph taken after the insertion. The cochleas were then histologically processed with the electrode array in situ, and the resulting sections were subsequently assessed for position of the electrode array as well as insertion-related intracochlear damage. Results: All perimodiolar electrode arrays were inserted deeper and showed trajectories that were generally closer to the modiolus compared with the standard electrode array. However, although the precurved array designs did not show significant insertion trauma, the method of insertion needed improvement. After insertion of the straight electrode array with positioner, signs of severe insertion trauma in the majority o fimplanted cochleas were found. Conclusions: Although it was possible to position the electrode arrays close to the modiolus, none of the three perimodiolar designs investigated fulfilled satisfactorily all three criteria of being easy, safe, and a traumatic to implant.
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ItemGeneralisation of tactile perceptual skills to new context following tactile-alone word recognition training with the Tickle Talker( 2000)Abstract not available due to copyright.
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ItemThe role phase-contrast imagining in intra-cochlear electrode development( 2000)In order to improve the design of intracochlear multichannel electrode arrays, it is fundamental that we have knowledge of the exact anatomical , position of the electrode within the scala of the cochlea. Currently, conventional skull radiography is still the mainstay of post-operative radiological assessment of electrode positioning. The present work investigates the use of phase-contrast radiography, a new x-ray modality, to provide improved imaging of the inner ear and the intracochlear electrode array in the human temporal bone (TB).
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ItemSafety studies and preliminary patient trails with a new perimodiolar electrode array( 2000)A new perimodiolar electrode array, the curly-with stylet (CwS), has been developed and undergone safety trials in human cadaver temporal bones. The array was developed as a result of animal and modelling studies which indicated that there are potential advantages in situating the electrode array in closer proximity to the neural elements. Preliminary studies with four patients in Melbourne implanted with a developmental pre-curved array had supported the predictions of lower current requirements and possibly more focussed spread of excitation.
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ItemWhat factors contribute to successful outcomes for children using cochlear implants( 2000)Long term speech perception data has been collected for 100 children using the Nucleus multichannel cochlear prosthesis in Melbourne. Scores on a number of different assessments are available at approximately six month intervals following implantation for these children. The group represents an unselected sample of cochlear implant users, as all children were included if they had sufficient developmental skills to perform formal speech perception tests. Information was also collected on each child regarding type of hearing loss, age of onset of profound hearing loss, duration of profound hearing loss, age at implantation, pre and post-implant communication mode, developmental delay, speech processing strategy and length of experience with implant use.
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ItemLatest results for adults & children using cochlear implants & future implications( 2000)The overall success of a cochlear implant procedure is most often quantified by assessing how well implantees can understand speech. This is because a primary aim of the application of cochlear implants is to improve communication, and it is relatively straightforward to obtain accurate measures of speech recognition. The quality of cochlear implant hearing is not well described by measuring an audiogram, as the detection of sound is similar across all implantees if the device is functioning correctly. A commonly used measure of speech understanding is the CID everyday sentence test where the number of correctly identified words within sentences is assessed. In the early days of cochlear implants, subjects could only recognize a few words without lipreading but the most recent results show average scores of 80% without lipreading for this sentence test, after 6 months of experience with the device.
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ItemHearing levels and speech perception prior to cochlear implantation - are they predictive of outcomes for adult implant users?( 2000)As the speech perception results obtained for adults using multichannel cochlear implants have improved, people with a wider range of hearing losses are now considering implantation. In the mid-1980s, most adults undergoing cochlear implantation had little or no residual hearing. This made selection and counselling relatively straightforward as any level of hearing obtained through use of the cochlear implant could be considered as a benefit in such cases. Most patients evaluated for implantation today have some degree of useful residual hearing, and may be reliant on this hearing to varying degrees in their everyday life. In essence, they have something to lose if their postoperative performance is poor. In counselling these patients, it would be most helpful to have reliable predictors of postoperative performance. A number of factors such as duration of profound hearing loss, congenital profound hearing loss, and certain aetiologies (eg, head injury) have shown significant links with outcomes in previous studies.
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ItemWhere to now? - Impact of New Technologies on use of cochlear implants( 2000)The history of cochlear implant use by adults and children with profound hearing loss although relatively short (20 some years), has been characterised by continual technological innovations which have enhanced the performance, packaging, and clinical use of these devices. In particular, the development of the Nucleus multiple channel cochlear implant has included a series of speech processing hardware and speech processing strategy, implemented by Cochlear Limited, and based on research findings that have resulted in an increase in mean speech perception benefits for adults and children.
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ItemHow much residual hearing is too much?( 2000)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 (U.S. National Institutes of Health Consensus Statement 1995). As a direct consequence of the level of benefits shown for cochlear implant users on measures of speech perception, research has focused on investigating whether severely hearing impaired adults and children would be suitable candidates for cochlear implantation. I n considering the candidature of any individual, both medical and audiological suitability are investigated. The primary concern is to establish to what degree the patient would benefit from use of the cochlear implant.