Graeme Clark Collection

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Subject: cochlear implants × Start date: 2000 × End date: 2001 × Author: DAHM, MARKUS ×

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    Surgical implications of perimodiolar cochlear implant electrode design: avoiding intracochlear damage and scala vestibuli insertion.
    Briggs, RJ ; Tykocinski, M ; Saunders, E ; Hellier, W ; Dahm, M ; Pyman, B ; Clark, GM (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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    Post mortem study of the intracochlear position of the nucleus standard 22 electrode array
    XU, JIN ; Dahm, M. C. ; Tykocinski, Michael. ; Shepherd, Robert K. ; Clark, Graeme M. ( 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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    Phase-contrast radiography: a new x-ray technique for cochlear implant research
    XU, JIN ; Stevenson, A. W. ; Gao, D. ; Dahm, M. ; Wilkins, S. W. ; Clark, Graeme M. (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.