Graeme Clark Collection
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ItemSpeech perception benefits for children using the 22-channel Melbourne/cochlear hearing prosthesis [Abstract]( 1993)In 1985; the first child was implanted with the Cochlear 22-channel cochlear prosthesis at the University of Melbourne Royal Victorian Eye & Ear Hospital Cochlear Implant Clinic. There are now 42 children who have received the device in Melbourne. Analysis of patient details for these children show a very heterogeneous group, with a wide range in age, hearing thresholds, duration of deafness and aetiology. The major aetiologies found were either a congenital profound deafness.; or a hearing loss due to meningitis. In all but 3 cases, the children are using 15 or more electrodes in the array. Speech perception benefits have been analyzed according to a six-level hierarchical classification scheme. All of-the children achieved a minimum benefit of discrimination of suprasegmental information (Category 2), and 59% of the children achieved open-set understanding of unfamiliar speech material without the aid of lip-reading (Categories 5 & 6). Detailed analysis suggests that the majority of children achieving open-set speech perception benefits had more than one year of experience with their implant. and less than seven years of profound deafness prior to implantation.
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ItemFactors associated with open-set speech perception in children using the Cochlear multiple-channel prosthesis [Abstract]( 1993)Since 1985, nearly 100 children have received the 22-channel cochlear prosthesis from the Melbourne and Sydney cochlear implant clinics. These two clinics account for the bulk of casesin Australia, and have similar management philosophies and selection criteria. The patient population represents a variety of etiologies, and ranges in age from 2 - 18 years of age. Bothcongenital and postlinguistic hearing losses are included. In order to assess benefit to speech perception in such a diverse group, the children's results have been tabulated according to a six level hierarchical scale of speech perception achievement. The scale ranges from category I,detection of sound only, to category 6, which includes significant perception scores for open-setwords and sentences. Analysis of the results shows that the majority of the children are achieving open-set speech perception benefits, and that results continue to improve with additional experience with their devices. There are a number of contributing factors to these open-set speech� perception results which have impact both on selection issues and on habilitation with different age ranges �of patients.
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ItemFuture directions in the clinical application of multichannel cochlear prostheses [Abstract]( 1992)Three main areas of work at the University of Melbourne relating to the clinical application of multichannel cochlear prostheses will be discussed. Speech perception results for 40 children and adolescents implanted with the Nucleus multichannel device will be presented with an analysis of potentially predictive clinical factors. Overall results have shown that 60% of the children have developed useful open-set speech recognition ability without visual cues. Due to the improved speech perception for postlinguistically deafened adult cochlear implant patients, the multichannel implant has become a viable alternative for patients with some useful residual hearing. A "bimodal" speech processor which provides acoustic output for the residual hearing ear and electrical output for the cochlear implant will also be discussed. This device provides a flexible, programmable acoustic processor which can make use of feature coding aspects of the implant processing. The "bimodal" device has also addressed problems of incompatibility of the implant signal with the acoustic signal from conventional hearing aids. Results for the new "Spectral Maxima Speech Processor" (SMSP) will also be presented. The SMSP has shown improved speech perception performance in quiet and in noise when compared with the MSP (MULTIPEAK) system, currently in use with the Nucleus device. Results for four subjects with the SMSP showed mean scores of 57.4% for open-set monosyllabic words in quiet, and 78.7% for open-set sentences in a 10 dB signal-to-noise ratio
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ItemPreliminary speech perception results for children with the 22-electrode Melbourne / cochlear hearing prosthesis( 1992)The Cochlear 22-electrode cochlear prosthesis was first implanted in a child at the Cochlear Implant Clinic at the University of. Melbourne and Royal Victorian Eye & Ear Hospital in 1985. Since that time 42 children have received the device in Melbourne. Analysis of patient details shows that the majority of these children have a congenital as opposed to on acquired aetiology of hearing loss. In all but 3 cases, the children use 15 or more electrodes. In order to assist with evaluation of, benefits to speech perception across the very heterogeneous group of children, a six level hierarchical classification scheme for speech perception performance levels was created. All of the children achieved a minimum of Category 2 (discrimination of suprasegmental information). In total, 59 % of the children achieved Category 5 or 6 (open set recognition for unfamiliar materials). Analysis showed that the majority of these children had more than one year of experience. In contrast, the majority of children in Category 2 are those with less than one year of experience with the device.
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ItemImprovements in speech processing for the nucleus cochlear implant [Abstract]( 1992)The Nucleus Cochlear implant allows ~ variety of multiple channel speech processing strategies to be developed and trialled. The initial strategy first developed by the University of Melbourne presented the second formant frequency as place and voicing as rate of stimulation. The strategy was subsequently improved by presenting the first format on a place basis as well. Since that time the addition of more spectral information coded as place of stimulation and temporal information presented as variations in amplitude have resulted in better open-set CNC word and sentence scores for electrical stimulation alone. One of the improved strategies selects four pairs of electrodes from the 22 electrode array each glottal pulse to present the first and second formants as well as the output from two high Frequency band pass filters. The other strategy stimulates six of the 22 electrodes representing the six maximal outputs from 16 bandpass filters. The clinical results have shown that both the above strategies results in better open-set speech perception for electrical stimulation in quiet and in noise. 80 % scores have been obtained for open-sets of CNC words and 90 % for open-sets of words in sentences for some of the patients using the latter strategy.
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ItemPsychophysical studies with children using cochlear implants [Abstract]( 1992)Psychophysical studies were conducted on a heterogeneous group of 12 patients using, the Cochlear Nucleus cochlear implant. These patients became profoundly deaf early in life, prior to the full development of auditory and speech skills. The aim of the studies was to determine whether the basic hearing skills of these patients differ from those of patients who becamedeaf later in life. The mean age of, the patients at confirmation of the profound hearing loss was 22.3 months (range 6 to 45 months). The mean age of at the time of implantation as 14.8 years (range 5 to 24 years). The cause of deafness was meningitis for 7 patients, congenital Usher's syndrome for 3 patients and congenital unknown for 2 patients.
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ItemMultichannel cochlear implants in children: an overview of experimental and clinical results [Abstract]( 1991)During the last decade there has been great progress in the clinical management of profound, postlinguistically deafened adults through the use of multichannel cochlear implants. The device developed by Cochlear Pty. Ltd. in association with the University of Melbourne, electrically stimulates selective regions of the residual auditory nerve using an array of 22 Pt electrodes located within the scala tympani. A speech processing strategy has been developed to provide patients with both voice pitch, and first and second formant information. Following experimental safety studies and successful clinical trials, this device was approved for use in adults by the United States FDA in 1985. In 1990, following further miniaturization of the implant, the FDA approved the device for use in profoundly deafened children above the age of two years. The present paper presents an overview of our recent biological safety studies and clinical experience with cochlear implants in children, and discusses the likely future development of these devices. Our biological safety studies were designed to evaluate the safety and design requirements of cochlear implantation in children, and more recently has focussed on issues for implantation in very young children (< 2 years old). These studies included the measurement of growth in the human temporal bone and the development of lead wires that can accommodate such growth, the development of an electrode fixation technique close to the cochlea, the effect of cochlear implantation on skull growth, the effect of long-term electrical stimulation on the maturing auditory system and the stimulating electrodes, and the effect of middle ear infection on cochlear implantation. Our clinical experience is based on twenty-five children that have now been implanted in our clinic. They include (i) postlinguistically deafened children; (ii) congenitally or early-deafened young children; and (iii) congenitally or early deafened adolescents. Clinical testing has shown improvements in speech perception, speech production and language in all three groups. Postlinguistically deafened children show similar speech perception results to postlinguistically deafened adults. For the congenitally deaf, younger children tend to show better results than the adolescents. Significantly, these clinical results are consistent with results from 142 children obtained from clinics throughout the world. These experimental and clinical results support the use of cochlear implants in young children. Further clinical improvements can be expected in the future with advances in both hardware and speech processing strategies.