CONSERVATION OF RESIDUAL HEARING WITH COCHLEAR IMPLANTATION

Hypothesis: The goals of this work were (a) to review the pre- and pos tsurgical auditory thresholds in a consecutive sample of cochlear impl ant recipients to determine the fate of residual hearing, and (b) to o btain preliminary indication of the value of a multicenter longitudina l study of residual hearing in implant patients. Background: Indicatio ns for cochlear implantation have been expanded to include severely he aring impaired (SHI) adults and may someday include SHI children. Impl antation of individuals with more residual hearing is a concern owing to the possible development of better devices that may make use of res idual hearing within the lifetime of implanted children if not that of adults. Preservation of residual hearing would be a desirable outcome of implant surgery; however, conventional thought is that implantatio n destroys any remaining hearing. This study was undertaken to assess if and how often conservation of hearing occurred after implantation i n a sample of multichannel implant recipients. Methods: Records of 50 profoundly hearing impaired consecutively implanted patients were exam ined for pre- and postsurgical audiometric results. Standard audiometr ic techniques were used for all testing procedures. Forty patients wer e considered to have some hearing conserved based on a response obtain ed at any one of the three speech frequencies prior to implantation. T he most recent postimplantation audiometric results were used providin g data from users with 1-41 months of use. Results: Twenty-one of 40 i mplanted subjects were found to have responses in at least one of the speech frequencies both pre- and postsurgery, with the majority of tho se displaying responses at all three frequencies. In this preliminary retrospective study, it did not appear that duration of cochlear impla nt use, sender, level of preoperative hearing, or length of electrode insertion were related to outcome. There were insufficient data to dra w conclusions on individual devices. Conclusions: Conservation of hear ing occurred in approximately half of the subjects reviewed. There is no indication of what factors contributed to the preservation of heari ng in those with postsurgical residual hearing or if that hearing is u sable. The study does suggest that a larger multicenter longitudinal s tudy would be of value to determine what factors may be related to con served hearing in implanted patients.