[Conservation of residual hearing after cochlear implantation]

Indications for cochlear implantation have been expanded to include severely hearing impaired adults and may increase the number of patients presenting with preoperative residual hearing. Conservation of residual hearing may allow better performance with an implant. However, conventional thought is that implantation destroys auditory structures involved in residual hearing. This study was undertaken to assess if there are general or surgical factors intervening in the conservation of residual hearing in a sample of multichannel implant recipients. A retrospective study on 50 adult cochlear recipients with preoperative residual hearing has been undertaken. Sixteen of 50 implanted subjects (32%) were found to have conserved their residual hearing. Among them, seven patients have clinically non-significant changes of hearing. Age, side of implantation, gender and etiology did not influence the outcome of residual hearing. Round window ossification, ossification of the cochlea, length of insertion, approach and site of insertion (scala tympani vs.scala vestibuli) were not found to be statistically significant between the population having lost and the population having conserved residual hearing. This study emphasizes the need to undertake a larger multicenter longitudinal study to determine the existence of factors related to the conservation of residual hearing.