Cochlear implant safety studies [Abstract]

We have examined a number of safety issues associated with cochlear implantation in both adults and children and confirm that it is safe. The results of these studies may be summarized as follows: 1) The insertion of a free-fit scala tympani array into the human cochlea produces minimal damage to cochlear structures provided insertion is stopped at the point of first resistance. 2) Chronic intracochlear implantation and electrical stimulation using charge balanced biphasic current pulses does not result in neural degeneration or evoke an adverse tissue reaction within the cochlea. 3) The use of fascia to seal the implanted round window results in an effective barrier to the spread of infection into the cochlea. 4) Temporal bone studies have shown that the distance between the round window and the fossa incudis remains essentially unchanged from birth. Therefore, the fossa incudis provides a suitable fixation point for the electrode array in young children. This study also showed that the distance from the round window to the implanted receiver-stimulator undergoes significant change in children of up to two years of age. These children would require an expanding leadwire system. 5) Finally, long-term effects of cochlear implant surgery on skull growth have shown that this should not be a problem when implanting very young children. This work was supported by the NIH (NOI-NS-7-2342).