Graeme Clark Collection
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ItemHow much residual hearing is too much?( 2000)The value of cochlear implants as an established clinical option for profoundly hearing-impaired adults and children has been supported by significant research results over a number of years (U.S. National Institutes of Health Consensus Statement 1995). As a direct consequence of the level of benefits shown for cochlear implant users on measures of speech perception, research has focused on investigating whether severely hearing impaired adults and children would be suitable candidates for cochlear implantation. I n considering the candidature of any individual, both medical and audiological suitability are investigated. The primary concern is to establish to what degree the patient would benefit from use of the cochlear implant.
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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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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.
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ItemSpeech perception benefits for implanted children with preoperative residual hearing [Abstract]( 1995)Since the implantation of the first children with the Nucleus 22-channel cochlear prosthesis in Melbourne in 1985, there has been rapid expansion in the number of implanted children world-wide. Improved surgical technique and experience in paediatric assessment and management have contributed to a trend to implant very young children. At the same time there has also been continuing development of improved speech processing strategies resulting in greater speech perception benefits.
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Item3D reconstruction of the temporal bone in cochlear implant surgery [Abstract]( 1991)High resolution CT-imaging is a routine part of the preoperative evaluation of prospective cochlear implant patients. We have used image analysis techniques to produce three-dimensional (3D) reconstruction of the temporal bone from serial CT-scans. These images have proved very useful in the examination of the temporal bone prior to implant surgery.
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ItemCriteria of suitability for cochlear implantation [Abstract]( [1990])In order to be considered for a cochlear implant, the person should have a profound bilateral hearing 1088, with little or no benefit from hearing aids. People with minimal open-set speech discrimination can be considered, with phoneme scores of up to 20% in the better ear, provided the ear to be implanted does not obtain significant open-set speech discrimination. Where there is any degree of benefit from hearing aids, even as an aid to lipreading, the poorer hearing ear is preferred for implantation. A team approach is necessary to detect and correct medical, learning and psychosocial problems. The CT scan has been designed to measure the patency of the cochlear spiral and detect any lesions of the internal auditory meatus, air cell system or emissary veins which could make for surgical difficulty. The electrical stimulation of the remaining auditory neurones by a needle on the promontory aims to confirm the responsiveness of the auditory nerve and should be performed on all candidates 12 years and older. There is a battery of assessments available but if the pulse cannot be detected before it reaches a current level producing pain the ear should not be implanted. The threshold and minimal gap detection tests have no prognostic value but the patient's observations about the percept produced by pulses of 50, 100 and 200pps are useful. There is a relationship between the ability to detect change in pulse rate and the postoperative CID sentence score. This may be used to choose a preferred ear and to give a guide to the possibility of a high or a low speech perception score. We believe the tests are an important part in gaining realistic expectations especially when the patient can listen to speech through a FO extraction speech processor attached to the needle.