Graeme Clark Collection
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ItemClinical results for profoundly deaf patients using the 22-elctrode cochlear prosthesis [Abstract]( 1987)The 22-electrode cochlear prosthesis developed in Australia by the University of Melbourne and Cochlear Pty. Limited has been in clinical use in Melbourne for five years. Results for 40 postlingually deaf adults have shown significant communication benefit for 90% of patients. Twenty patients (50%) have demonstrated the ability to understand conversational speech without lipreading or visual cues. No electronic or mechanical failures have been observed in any of the implanted devices. There have been no serious medical complications, but psychological disturbance has occurred in two cases. Experience with prelingually deaf adults has indicated that initial hearing responses for this group are not as good as for the postlingually deaf patients. However, improvement over time has been evident with consistent use of the device. Long-term benefit for these patients will depend to a large extent on motivational and social factors. Results for a small number of young deaf children have been encouraging. The age at onset of profound deafness, intelligence, educational management and family support are all important factors affecting the potential benefit of a cochlear implant for a child.
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ItemResults for the Nucleus multiple-electrode cochlear implant in two children [Abstract]( 1988)Two males, 9 years 10 months (CHILD 1) and 5 years 5 months (CHILD 2) at time of surgery, were implanted with the Nucleus multiple-electrode cochlear implant. Both patients were deafened as a result of meningitis in their third year. Assessments of speech perception, speech production and language skills were undertaken at regular intervals, pre and post operatively. For both patients in the audition alone condition, some speech perception post operative scores were significantly higher than pre operative scores and progressive improvements in scores over successive post operative data collection times were seen. Significant differences between the visual alone and auditory-visual condition scores were also observed for CHILD 1 post operatively. Speech production post operative scores were significantly higher than pre operative scores for both patients. The receptive vocabulary scores for both patients improved at a higher rate than that of age-matched normal children. The acquisition of expressive and receptive language skills for CHILD 2 was at a higher rate than that of age-matched children. Differences in the results between the two patients were seen, and this may be related to age and duration of deafness.
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ItemVentral cochlear nucleus and auditory nerve fibre responses to electrical stimulation of the cat cochlea [Abstract]( 1987)Discharge patterns of cat auditory nerve fibres and ventral cochlear nucleus neurones to constant-current biphasic pulses have been recorded. The study was carried out to determine the input-output characteristics of the neurones, for variations in the rate and intensity of electrical stimulation. Neural discharges were highly synchronized with the current pulses at suprathreshold stimulus intensities, and saturation discharge rates usually equalled stimulus pulse rates up to 800 pulses/s. The electrically-driven discharge patterns of ventral cochlear nucleus neurones exhibiting "primary-like" responses were similar to those recorded from electrically-stimulated auditory nerve fibres. Comparison of the neural responses to electrical and acoustic stimulation may help in the design of improved speech processors for cochlear implants. Field potential responses were depressed at high stimulus rates and charge densities, suggesting stimulus-induced reduction in neural excitability. The effects of stimulus parameter variations on field potentials may help in determining safety limits of the electrical stimulus.