- Graeme Clark Collection
Graeme Clark Collection
Permanent URI for this collection
Search Results
Now showing
1 - 10 of 32
-
ItemResults in children using the 22 electrode cochlear implant [Abstract]Dawson, Pam W. ; Blamey, Peter J. ; Clark, Graeme M. ; Busby, P. A. ; Rowland, L.C. ; Dettman, S. J. ; Brown, A. M. ; Dowell, Richard C. ; Rickards, Field W. ; Alcantara, Joseph I. ( 1989)Abstract not available due to copyright.
-
ItemThe histopathology of the human temporal bone and auditory central nervous system following cochlear implantation in a patient: correlation with psychophysics and speech perception resultsClark, Graeme M. ; Shepherd, Robert K. ; Franz, Burkhard K.-H. ; Dowell, Richard C. ; Tong, Yit C. ; Blamey, Peter J. ; Webb, Robert L. ; Pyman, Brian C. ; McNaughton, Judy ; Bloom, David M. ; Kakulas, Byron A. ; Siejka, Stan ( 1988)Cochlear implantation has become a recognised surgical procedure for the management of a profound-total hearing loss, especially in patients who have previously had hearing before going deaf (postlingual deafness). Nevertheless, it is important for progress in the field that patients who have had a cochlear implant, bequeath their temporal bones for research. This will then make it possible to further assess the safety of the procedure, and the factors that are important for its effectiveness. Biological safety has been assessed in a number of studies on animals, in particular, the biocompatibility of the materials used (1,2), the histopathological effects of long-term implantation on the cochlea (3, 4, 5, 6, 7, 8), and the effects of chronic electrical stimulation on the viability of spiral ganglion cells (9, 10, 11, 12). In studying the temporal bones of deceased cochlear implant patients it is possible to help establish that the animal experimental results are applicable to Man. Surgical trauma has been most frequently evaluated by inserting electrodes into cadaver temporal bones. It is important, however, to examine bones that have been previously implanted surgically to ensure that the cadaver findings are applicable to operations on patients. The effectiveness of cochlear implantation can be studied by correlating the histopathological findings, the dendrite and spiral ganglion cell densities, in particular, with the psychophysical and speech perception results. Other benefits also accrue, for example, establishing the accuracy of preoperative X-rays and electrical stimulation of the promontory in predicting cochlear pathology and spiral ganglion cell numbers. For the above reasons it has been especially interesting to examine both the temporal bones and central nervous system from one of our patients (patient 13) who participated in the initial clinical trial of the Cochlear Proprietary Limited (a member of the Nucleus group) multiple-electrode cochlear prosthesis, and who died due to a myocardial infarction following coronary bypass surgery.
-
ItemThe University of Melbourne/Nucleus cochlear prosthesisClark, Graeme M. ; Blamey, P. J. ; Brown, A. M. ; Busby, P. A. ; Dowell, R. C. ; Franz, B. K-H. ; Millar, J. B. ; Pyman, B. C. ; Shepherd, R. K. ; Tong, Y. C. ; Webb, R. L. ; Brimacombe, J. A. ; Hirshorn, M. S. ; Kuzma, J. ; Mecklenburg, D. J. ; Money, D. K. ; Patrick, J. F. ; Seligman, P. M. ( 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.
-
ItemSpeech perception with cochlear implants and tactile aids [Abstract]Blamey, P. J. ; Clark, Graeme M. ; Dowell, R. C. ( 1988)Abstract not available due to copyright.
-
ItemRecent developments with the Nucleus 22-electrode cochlear implant: a new two formant speech coding strategy and its performance in background noiseFranz, Burkhard K-H. G. ; Dowell, Richard C. ; Clark, Graeme M. ; Seligman, Peter M. ; Patrick, James F. ( 1987)A clinical evaluation of speech processing strategies for the Nucleus 22-electrode cochlear implant showed improvements in understanding speech using the new F0F1F2 speech coding strategy instead of the F0F2 strategy. Significant improvement in closed-set speech recognition in the presence of background noise was an additional advantage of the new speech processing strategy.
-
ItemEvaluation of a two-formant speech-processing strategy for a multichannel cochlear prosthesisDowell, R. C. ; Seligman, P. M. ; Blamey, P. J. ; Clark, Graeme M. ( 1987)Initial results with the two-formant speech-processing strategy (F0FIF2) confirm the advantage of a multichannel cochlear prosthesis capable of stimulating at different sites within the cochlea. The successful presentation of two spectral components by varying the place of stimulation leads to the possibility of presenting further spectral information in this manner. Because virtually all multichannel implant patients demonstrate good "place" (electrode site) discrimination, these more refined coding strategies should lead to benefits for the majority of implantees. Already, with the F0FIF2 strategy, we have a system that appears to provide some effective auditory-alone communication ability for the average patient.
-
ItemA multiple-electrode intracochlear implant for childrenClark, Graeme M. ; Blamey, Peter J. ; Busby, Peter A. ; Dowell, Richard C. ; Franz, Burkhard K-H. ; Musgrave, Gaye Nicholls ; Nienhuys, Terry G. ; Pyman, Brian C. ; Roberts, Susan A. ; Tong, Yit C. ; Webb, Robert L. ; Kuzma, Januz A. ; Money, David K. ; Patrick, James F. ; Seligman, Peter M. ( 1987)A multiple-electrode intracochlear implant that provides 21 stimulus channels has been designed for use in young children. It is smaller than the adult version and has magnets to facilitate the attachment of the headset. It has been implanted in two children aged 5 and 10 years. The two children both lost hearing in their third year, when they were still learning language. Following implantation, it was possible to determine threshold and comfortable listening levels for each electrode pair. This was facilitated in the younger child by prior training in scaling visual and electrotactile stimuli. Both children are regular users of the implant, and a training and assessment program has been commenced.
-
ItemAudiological assessment of profoundly hearing-impaired childrenBusby, P. A. ; Dowell, R. C. ; Nienhuys, T. G. ; Clark, Graeme M. ( 1987)The design of an audiological assessment protocol for profoundly hearing-impaired children may be divided into three areas. First, accurate estimation of hearing loss includes the behavioral measures of unaided and aided thresholds and the objective measures of electrocochleography and auditory brain stem response. The reliability of these measures for the accurate diagnosis of a profound to total hearing loss is discussed. Second, speech perception includes the measure of perception in the audition alone, vision alone, and audition plus vision conditions. Test material should include speech features, words, and sentences. Factors influencing the choice of material are the developmental age of the child, the method of educational instruction, speech and language skills, and vocabulary limits. Third, psychophysical properties of residual auditory skills include measures such as frequency, intensity, and duration difference limens. These skills may be compared to those elicited through other sensory channels, such as visual and tactile. Other important factors that should be considered are the psychological well-being of the child and family, family motivations and expectations, and educational requirements.
-
ItemClinical results for postlingually deaf patients implanted with multichannel cochlear prosthesesBrown, A. M. ; Dowell, R. C. ; Clark, Graeme M. ( 1987)Clinical results for 24 patients using the Nucleus 22-channel cochlear prosthesis have shown the device to be successful in presenting amplitude, fundamental frequency, and second formant information to patients with acquired hearing loss. For all patients, this has meant a significant improvement in their communication ability when using lipreading and some ability to understand unknown speech without lipreading or contextual cues. Approximately 40% of patients are able to understand running speech in a limited fashion without lipreading, and this ability has been evaluated using the speech-tracking technique for a number of patients. Many patients are able to have limited conversations on the telephone without using a special code. Although the prosthesis has been designed with the presentation of speech signals in mind, recognition and discrimination of environmental sounds has also been very encouraging with patients scoring 70% to 80% correct for closed set environmental sound testing. Follow-up testing has indicated that the ability to understand open set speech without lipreading continues to improve up to at least 12 months postoperatively. Open set sentence test results improved from an average of 20% at 3 months to 40% at 12 months.
-
ItemAcoustic parameters measured by a formant-estimating speech processor for a multiple-channel cochlear implantBlamey, P. J. ; Dowell, R. C. ; Clark, Graeme M. ; Seligman, P. M. ( 1987)Abstract not available due to copyright.