Graeme Clark Collection

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End date: 1997 × Start date: 1992 × Type: Conference Item × Subject: cochlear implant × Subject: otolaryngology × Subject: safety studies ×

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Now showing 1 - 4 of 4
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    Electrophonically driven single unit responses of the anteroventral cochlear nucleus in cat [Abstract]
    Morrison, N. A. ; Brown, M. ; Clark, Graeme M. ( 1996)
    Electrical stimulation of the cochlea results in both direct and electrophonic excitation of auditory nerve fibres. It has been proposed that electrophonic stimulation results from the creation of a mechanical disturbance on the basilar membrane which has properties similar those resulting from acoustic stimuli. Auditory nerve compound action potential (CAP) forward masking studies1 show the level of frequency specific electrophonic stimulation is highly correlated with the spectral energy of the electrical stimulus waveform. The level of spectral energy in pulsatile biphasic electrical stimuli decreases toward low frequencies suggesting the level of electrophonic stimulation will be diminished in the low frequency region of the cochlea.
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    The histological and physiological effects of the auditory brainstem prosthesis of the auditory pathway [Abstract]
    Lui, Xuguang ; McPhee, Greg. ; Seldon, H. Lee ; Clark, Graeme M. ( 1997)
    The cochlear implant can successfully rehabilitate the majority of profoundly deaf patients. However, some of them cannot benefit from the cochlear implant due to bilateral interruption of the auditory nerve, particularly from neurofibromatosis II. These patients can be stimulated directly with an auditory brainstem prosthesis on the cochlear nucleus. To examine the safety and the efficacy of this prosthesis, the cochlear nuclei of guinea pigs were implanted unilaterally with bipolar surface electrodes, and stimulated acutely using charge-balanced, biphasic current pulses at rates of 250, SOO or 1000 Hz and charge intensities of 1.8, 2.8, 3.5 or 7.1?C/phase/cm2.
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    Electrical stimulation of the auditory nerve in deaf kittens: effects on the spiral ganglion [Abstract]
    Shepherd, R. K. ; Matsushima, J ; Clark, Graeme M. ( 1992)
    Cochlear pathology following the administration of ototoxic drugs results in a widespread and rapid loss of sensory hair cells followed by a gradual degeneration of auditory nerve fibres and their cell bodies, the spiral ganglion. Recently, two studies have described increased spiral ganglion cell survival in the cochleas of deafened animals following chronic electrical stimulation of the auditory nerve (Hartshorn et al., 1991; Leake et al., ]991). If electrical stimulation is shown to have a trophic effect on degenerating auditory nerve fibres, these findings will significantly influence the preoperative management of cochlear implant patients. The aim of the present study was to corroborate these earlier reports and to evaluate the general tissue response of deafened cochleae in young animals following chronic electrical stimulation.
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    Multichannel cochlear implants in children: an overview of experimental and clinical results at the University of Melbourne [Opening Lecture]
    Shepherd, R. K. ; Dowell, R. C. ; Xu, S-A. ; McDermott, H. J. ; McKay, C. M. ; Clark, Graeme M. ( 1992)
    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 The University of Melbourne in association with Cochlear Pty Ltd, electrically stimulates selective regions of the auditory nerve using an array of 22 platinum (Pt) electrodes located in the scala tympani. Its development followed basic experimental studies and the development and evaluation of a prototype device in the 1970's. Following safety studies and a successful clinical trial, the Melbourne/Cochlear multichannel implant was approved for use in adults by the United States Food and Drug Administration (FDA) in 1985. More than 3000 patients throughout the world have since been implanted with this device, many being able to understand a significant amount of unfamiliar, connected speech without lipreading Following miniaturization of the implant, it became suitable for use with children. In 1990, after additional biological safety and clinical investigations, the FDA approved the use of the Melbourne/Cochlear multichannel implant for profoundly deaf children above the age of two years. And in 1991, the device received the medical device implantation approval certificate from the Japanese Government. The present paper presents an overview of our recent biological safety studies and clinical experience in children, and discusses the likely future development of these devices.