Graeme Clark Collection

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1984 - 1985 2
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Author: PYMAN, BRIAN × End date: 1986 × Start date: 1980 × Subject: cochlear implants ×

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    Surgery for an improved multiple-channel cochlear implant
    Clark, Graeme M. ; Pyman, Brian C. ; Webb, Robert L. ; Bailey, Quentin E. ; Shepherd, Robert K. ( 1984)
    An improved multiple-channel cochlear implant has been developed. The titanium container with enclosed electronics, the receiver coil and the connector are embedded in medical-grade Silastic. The upper half of the implant has a diameter of 35 mm and a height of 4.5 mm. and the lower half a diameter of 23 mm and a height of.5 mm. The electrode array has also been designed to reduce the possibility of breakage due to repeated movements over many years. The surgery involves drilling a bed in the mastoid bone for the receiver-stimulator, and fixing the proximal electrode under the mastoid cortex. Gentle insertion of the electrode array through the round window and along the seala tympani is achieved with a specially designed microclaw.
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    Selection of patients for multiple-channel cochlear implantation
    Brown, A. M. ; Dowell, R. C. ; Clark, Graeme M. ; Martin, L. F. A. ; Pyman, B. C. (Raven Press, 1985)
    Only profoundly, bilaterally deaf adults are considered for evaluation. It is necessary to determine that the patient's communication ability cannot be improved to any significant degree with conventional hearing aids currently available. Initial assessment consists of audiometry, hearing aid evaluation(s), otological and medical examination, and for patients with no recent experience with hearing aids, a hearing aid trial. Polytome x-rays of temporal bones is carried out to ensure that cochlea structures are not grossly abnormal. Electrical stimulation of the promontory is used to confirm the presence of residual auditory nerve fibers. Where there is an audiometric difference between ears, the poorer ear is chosen for implantation provided there are no other contraindications. Intensive counselling is carried out to enable patients to make a fully informed decision about implantation. Patients undergo a battery of speech discrimination and lipreading tests with their hearing aid after their hearing aid trial. This is to provide a baseline for comparison with postoperative results and to assess the benefit obtained from the hearing aid. Any significant improvement in test results when using a hearing aid over lipreading alone would be a contraindication for implantation. Medical assessment is carried out as for any major surgery, including pathology, respiratory function tests and cardiovascular assessment. Particular emphasis is placed on infection prevention immediately preoperatively and during surgery.