Graeme Clark Collection

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Type: Conference Paper × Author: Shepherd, Robert × Author: PYMAN, BRIAN ×

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    Peri-modiolar electrode arrays: a comparison of electrode position n the human temporal bone
    Shepherd, R. K. ; Treaba, C. G. ; Cohen, L. ; Pyman, B. ; Huigen, J. ; Xu, J. ; Clark, Graeme M. (Monduzzi Editore, 1997)
    This paper describes a radiologic evaluation of three types of peri-modiolar arrays, comparing their trajectory within the scala tympani with a standard Mini-22 electrode. All peri-modiolar arrays were found to lie closer to the modiolus for much of their insertion length compared with the standard array. While one design showed evidence for the potential of increased insertion trauma, two designs produced satisfactory results. Although further electrode development, temporal bone and histopathologic studies arE required, it would appear that the benefits of peri-modiolar electrode arrays will be realised clinically.
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    Histopathology following electrode insertion and chronic electrical stimulation
    Shepherd, R. K. ; Clark, Graeme M. ; Pyman, B. C. ; Webb, R. L. ; Murray, M. T. ; Houghton, M. E. (Raven Press, 1985)
    We have examined a number of safety issues associated with cochlear implants. This work has been primarily designed to evaluate the histopathological effects of intracochlear electrode implantation and chronic electrical stimulation. The results of these studies may be summarized as follows: 1) The insertion of the banded free-fit scala tympani array into human cadaver temporal bones produces minimal damage, occurring primarily to a localized region of the spiral ligament. This damage would not result in significant neural degeneration and thus, would not compromise the efficacy of the multiple channel device; 2) chronic intracochlear electrical stimulation for continuous periods of 500 to 2000 hours, using charge balanced biphasic current pulses developing charge densities of 18-32 }?C/cm2. geom./phase, does not adversely affect the spiral ganglion cell population; 3) labyrinthine infection severely reduces the viable spiral ganglion cell population; 4) the formation of new bone present in approximately half of the animals we have implanted --is not associated with electrical stimulation per se; 5) scanning electron microscope studies of electrodes subjected to long periods of intracochlear electrical stimulation reveals minimal platinum dissolution when compared with unstimulated control electrodes, and electrodes that have been stimulated for similar periods in inorganic saline.