Graeme Clark Collection
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ItemSurgical implications of perimodiolar cochlear implant electrode design: avoiding intracochlear damage and scala vestibuli insertion.(Informa UK Limited, 2001-09)OBJECTIVE: To review the mechanisms and nature of intracochlear damage associated with cochlear implant electrode array insertion, in particular, the various perimodiolar electrode designs. Make recommendations regarding surgical techniques for the Nucleus Contour electrode to ensure correct position and minimal insertion trauma. BACKGROUND: The potential advantages of increased modiolar proximity of intracochlear multichannel electrode arrays are a reduction in stimulation thresholds, an increase in dynamic range and more localized neural excitation. This may improve speech perception and reduce power consumption. These advantages may be negated if increased intracochlear damage results from the method used to position the electrodes close to the modiolus. METHOD: A review of the University of Melbourne Department of Otolaryngology experience with temporal bone safety studies using the Nucleus standard straight electrode array and a variety of perimodiolar electrode array designs; comparison with temporal bone insertion studies from other centres and postmortem histopathology studies reported in the literature. Review of our initial clinical experience using the Nucleus Contour electrode array. RESULTS: The nature of intracochlear damage resulting from electrode insertion trauma ranges from minor, localized, spiral ligament tear to diffuse organ of Corti disruption and osseous spiral lamina fracture. The type of damage depends on the mechanical characteristics of the electrode array, the stiffness, curvature and size of the electrode in relation to the scala, and the surgical technique. The narrow, flexible, straight arrays are the least traumatic. Pre-curved or stiffer arrays are associated with an incidence of basilar membrane perforation. The cochleostomy must be correctly sited in relation to the round window to ensure scala tympani insertion. A cochleostomy anterior to the round window rather than inferior may lead to scala media or scala vestibuli insertion. CONCLUSION: Proximity of electrodes to the modiolus can be achieved without intracochlear damage provided the electrode array is a free fit within the scala, of appropriate size and shape, and accurate scala tympani insertion is performed.
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ItemComparison of electrode position in the human cochlea using various perimodiolar electrode arrays( 2000)Objective: This study was conducted to evaluate the insertion properties and intracochlear trajectories of three perimodiolar electrode array designs and to compare these designs with the standard Cochlear /Melbourne array. Background: Advantages to be expected of a perimodiolar electrode array include both a reduction in stimulus thresholds and an increase in dynamic range, resulting in a more localized stimulation pattern of the spiral ganglion cells, reduced power consumption, and, therefore, longer speech processor battery life. Methods: The test arrays were implanted into human temporal bones. Image analysis was performed on a radiograph taken after the insertion. The cochleas were then histologically processed with the electrode array in situ, and the resulting sections were subsequently assessed for position of the electrode array as well as insertion-related intracochlear damage. Results: All perimodiolar electrode arrays were inserted deeper and showed trajectories that were generally closer to the modiolus compared with the standard electrode array. However, although the precurved array designs did not show significant insertion trauma, the method of insertion needed improvement. After insertion of the straight electrode array with positioner, signs of severe insertion trauma in the majority o fimplanted cochleas were found. Conclusions: Although it was possible to position the electrode arrays close to the modiolus, none of the three perimodiolar designs investigated fulfilled satisfactorily all three criteria of being easy, safe, and a traumatic to implant.
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ItemPost mortem study of the intracochlear position of the nucleus standard 22 electrode array( 2000)The final position of an intracochlear cochlear implant electrode array can vary depending on the pathology, the insertion technique used and the type of electrode array used. The distance of the electrodes from the target neural elements and the presence of intracochlear fibrous tissue or new bone formation are believed to affect the performance of the device. A post mortem study was conducted to assess these factors.
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ItemThe role phase-contrast imagining in intra-cochlear electrode development( 2000)In order to improve the design of intracochlear multichannel electrode arrays, it is fundamental that we have knowledge of the exact anatomical , position of the electrode within the scala of the cochlea. Currently, conventional skull radiography is still the mainstay of post-operative radiological assessment of electrode positioning. The present work investigates the use of phase-contrast radiography, a new x-ray modality, to provide improved imaging of the inner ear and the intracochlear electrode array in the human temporal bone (TB).
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ItemPhase-contrast radiography: a new x-ray technique for cochlear implant research(Moduzzi Editore, 2000)This study examines the application of a new x-ray modality, phase contrast radiography, in temporal bone (TB) imaging. Preliminary results from TB samples have shown that phase-contrast imaging offers greater contrast for edge-type features and weakly absorbing soft-tissue resulting in improved visualization of anatomic details of inner ear and microelectrode structures. This is potentially valuable in the development of new electrode arrays for cochlear implants.
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ItemWhere to now? - Impact of New Technologies on use of cochlear implants( 2000)The history of cochlear implant use by adults and children with profound hearing loss although relatively short (20 some years), has been characterised by continual technological innovations which have enhanced the performance, packaging, and clinical use of these devices. In particular, the development of the Nucleus multiple channel cochlear implant has included a series of speech processing hardware and speech processing strategy, implemented by Cochlear Limited, and based on research findings that have resulted in an increase in mean speech perception benefits for adults and children.