Graeme Clark Collection
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ItemHabilitation issues in the management of children using the cochlear multiple-channel cochlear prosthesis(Wien, 1994)Since 1985, a significant proportion of patients seen in the Melbourne cochlear implant clinic have been children. The children represent a diverse population, with both congenital and acquired hearing-impairments, a wide-range of hearing levels pre-implant, and an age range from 2 years to 18 years. The habilitation programme developed for the overall group must be flexible enough to be tailored to the individual needs of each child, and to adapt to the changing needs of children as they progress. Long-term data shows that children are continuing to show improvements after 5-7 years of device use, particularly in their perception of open-set words and sentences. Habilitation programs must therefore be geared to the long-term needs of children and their families. Both speech perception and speech production need to be addressed in the specific content of the habilitation program for any individual child. In addition, for young children, the benefits of improved speech perception should have an impact on development of speech and language, and the focus of the programme for this age child will reflect this difference in emphasis. Specific materials and approaches will vary for very young children, school-age and teenage children. In addition, educational setting will have a bearing on the integration of listening and device use into the classroom environment.
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ItemThree-dimensional reconstruction of the cochlea and temporal bone(Karger, 1993)In recent years, cochlear implantation has become an established method for the auditory rehabilitation of profoundly deaf patients and is used in ever more and younger patients. High-resolution computed tomography is performed routinely on all prospective cochlear implant patients and provides important information about cochlear or mastoid pathology that will enable the surgeon to select a side for operation and alert him to surgical obstacles he might encounter [1-4]. In analysing the CT films he must still try to form a three-dimensional image in his mind by looking through a large number of different pictures [5]. Consequently, to make it easier to understand, we applied our own image analysis system to produce three-dimensional reconstructions of temporal bones from CT scans[6]. We focused on the use of this method for the preoperative examination and surgical planning for cochlear implantation as well as for our research purposes. This system and the results are presented here.
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ItemThe University of Melbourne/Nucleus cochlear prosthesis( 1988)This is a review of research to develop the University of Melbourne/Nucleus cochlear prosthesis for patients with a profound-total hearing loss. A more complete review can be obtained in Clark et al. A prototype receiver-stimulator and multiple-electrode array developed at the University of Melbourne was first implanted in a postlingually deaf adult patient with a profound-total hearing loss on 1 August 1978. A speech processing strategy which could help this patient understand running speech, especially when combined with lipreading was developed in 1978 following initial psychophysical studies. A prototype wearable speech processor was fabricated in 1979, that could provide significant help for the first two patients in understanding running speech when used in combination with lipreading compared with lipreading alone, and it also enabled them to understand some running speech when using electrical stimulation alone. An implantable receiver-stimulator and wearable speech processor embodying the principles of the prototype devices were then produced for clinical trial by the Australian biomedical firm, Nucleus Ltd, and its subsidiaries, Cochlear Pty Ltd and Cochlear Corporation. This cochlear implant was initially clinically trialled on six patients at The Royal Victorian Eye & Ear Hospital in 1982, and shown to give similar results to those obtained with the prototype device. In view of these findings a clinical trial was carried out for a Premarket Approval Application to the US Food and Drug Administration (FDA), and extended to a number of centres in the US, Canada, and West Germany. This clinical trial confirmed that patients could understand running speech when electrical stimulation was combined with lipreading, and that some patients could also understand running speech when using electrical stimulation alone. Today, more than 600 patients world-wide are using cochlear implants developed from the research described in this paper.
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ItemSurgery for an improved multiple-channel cochlear implant( 1984)An improved multiple-channel cochlear implant has been developed. The titanium container with enclosed electronics, the receiver coil and the connector are embedded in medical-grade Silastic. The upper half of the implant has a diameter of 35 mm and a height of 4.5 mm. and the lower half a diameter of 23 mm and a height of.5 mm. The electrode array has also been designed to reduce the possibility of breakage due to repeated movements over many years. The surgery involves drilling a bed in the mastoid bone for the receiver-stimulator, and fixing the proximal electrode under the mastoid cortex. Gentle insertion of the electrode array through the round window and along the seala tympani is achieved with a specially designed microclaw.
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ItemInsertion study using new peri-modiolar electrode array designs [Abstract]( 1999)Intracochlear multi-channel cochlear implants have been shown to successfully provide auditory information for profoundly deaf patients by electrically stimulating discrete populations of auditory nerve fibers via a scala tympani (ST) electrode array. Histological and radiological examination of implanted human temporal bones showed that the current straight Nucleus® array is usually positioned against the outer wall of the ST. An electrode array close to the modiolus could be expected to reduce stimulation thresholds and result in a more localized neural excitation pattern.
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ItemBenefits of pre-curved electrode arrays for the Nucleus multichannel cochlear implant [Abstract]( 1998)The purpose of the study was to evaluate whether placement of an electrode closer to the modiolus would provide a more efficient interface with the auditory nerve. A pre-curved, banded 22-electrode array has been developed. Following comprehensive safety studies, the array was inserted in three adult patients. Detailed x-ray analyses have been conducted to specify the positions of the electrode bands. Psychophysical studies have been conducted, within each subject, using electrodes which lie at differing distances from the modiolus. These studies have shown that as the distance from the modiolus decreased, electrode threshold currents decreased and dynamic ranges increased. Thresholds were lower than in a comparison group of standard array users. Forward masking studies showed current spread to be more focused at the electrodes lying closer to the modiolus. Electrode discrimination was also better at electrodes closer to the modiolus. JND for loudness, expressed as a function of dynamic range also decreased in this condition. Thus, a preliminary profile of the parameters of interest, for an improved implant design, suggest that an array which lies closer to the modiolus can result in lower current requirements and a more localised pattern of neural excitation.
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ItemSpeech perception & indirect benefits for severely hearing impaired children using cochlear implants [Abstract]( 1998)The benefits to speech perception, speech production, communication, and quality of life were investigated for severely hearing impaired children using cochlear implants and hearing aids. For the youngest children, assessments of psychological status, and use of a battery of cognitive and language tests were important factors in determining performance benefits prior to the child developing speech. For older children, the effects of increased one-to-one oral habilitation, and systematic encouragement of parental involvement were also investigated. Results suggested that parental support for consistent device use was an important factor in producing outcomes. Children with residual hearing were more likely to achieve open-set perception. Each child was also assessed for changes in quality of life, through use of a standardized health utility instrument. Results from the group were collated, and teamed with a costing assessment for the procedure, which allowed a complete cost-utility analysis to be completed. Results suggested that indirect benefits, such as the effects on speech production, usual activities, lower concentration, and less distress were ranked as more important than changes to hearing in a number of the children. Costs per QALY were consistent with those reported in the literature, and suggested that the cochlear implant is highly cost-effective as a medical technology.
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ItemPeri-modiolar electrode arrays: a comparison of electrode position n the human temporal bone(Monduzzi Editore, 1997)This paper describes a radiologic evaluation of three types of peri-modiolar arrays, comparing their trajectory within the scala tympani with a standard Mini-22 electrode. All peri-modiolar arrays were found to lie closer to the modiolus for much of their insertion length compared with the standard array. While one design showed evidence for the potential of increased insertion trauma, two designs produced satisfactory results. Although further electrode development, temporal bone and histopathologic studies arE required, it would appear that the benefits of peri-modiolar electrode arrays will be realised clinically.
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ItemSiting the receiver-stimulator of the CI-24M model of the Cochlear Limited multiple-channel cochlear implant and fixation of its electrode array(Monduzzi Editore, 1997)The correct siting of the cochlear implant receiver-stimulator package is important. The package should not obtrude significantly above the surface of bone, and should be so that blows to the head do not in damage to the package, skull or brain. The cochlear implant electrode array must be fixed 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, with Dacron® mesh, platinum-iridium ties, or clips, has been in the region of the posterior root of the zygoma and the floor of the antrum. Our research studies demonstrate that a specially-designed collar around the array can be placed through the cochleostomy and provide the necessary locking to prevent retraction of the array. It has a ceramic surround to encourage union with neighbouring bone, and stress relief to reduce wire fracture at the point where the array leaves the cochlea.
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ItemSpeech perception results for implanted children with different levels of preoperative residual hearing [Abstract]( 1996)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 suggestions that severely or severely-to-profoundly deaf children might benefit more from a cochlear implant than conventional amplification.