COCHLEAR ELECTRODE REIMPLANTATION IN THE GUINEA-PIG

Cochlear implants are being applied to an ever widening patient population, including children in whom lifetime use of these devices is anticipated. Replacement of implants can be expected for reasons of device failure as well as future upgrading. This investigation was undertaken to examine the effect of cochlear electrode explantation and reimplantation on spiral ganglion cell survival. Guinea pigs with normal ears were initially implanted and either explanted or explanted and reimplanted (at 2 months) with a single wire ball-tip intracochlear electrode or a silastic carrier (each remaining for an additional 2 months). Little loss of hair cells or auditory nerve was observed across experimental groups and normal controls. Restricted basal turn cochlear and spiral ganglion cell loss was observed in a few animals in each group and was likely associated with mechanical damage from initial implantation. Likewise the scattered organ of Corti damage and hair cell loss observed was noted in only a few cochleae in each experimental group. Therefore, no significant differences in the average pathology across experimental groups and controls were observed. Thus, explantation or explantation with subsequent reimplantation does not appear to constitute an additional significant pathological risk compared to implantation alone.