The aim of this study was to compare intracochlear-recorded cochlear microphonics (CM) responses to behavioral audiometry thresholds in young children, with congenital hearing loss, 2 to 5 years after cochlear implantation early in life. In addition, differences in speech and auditory outcomes were assessed among children with and without residual hearing.
The study was conducted at a tertiary, university-affiliated, pediatric medical center. CM responses by intracochlear electrocochleography technique were recorded from 102 implanted ears of 60 children and those responses correlated to behavioral audiometry thresholds at 0.125 to 2 kHz frequencies. All children had received Advanced Bionics cochlear implant with High Focus J1 or MidScala electrodes, along with extensive auditory rehabilitation before and after implantation, including the use of conventional hearing aids. Speech Spatial and Hearing Qualities, Category of Auditory Performance scale, and educational settings information were obtained for each participant. Those cochlear implantation (CI) outcomes were compared between children with or without residual CM responses.
Two distinctive CM responses patterns were found among the implanted children. Of all ears diagnosed with cochlear hearing loss (n = 88), only in 29 ears, clear CM responses were obtained. In all other ears, no CM responses were obtained at the maximum output levels. The CM responses were highly correlated with coefficients ranging from 0.7 to 0.83 for the audiometric behavioral thresholds at 0.125 to 2 kHz frequency range. Of all ears diagnosed with auditory neuropathy syndrome disorder (n = 14), eight ears had residual hearing and recordable CM postimplantation. The other six ears showed no recordable CM responses at maximum output levels for all tested frequencies. Those showed supposedly better CM responses than the behavioral audiometry threshold, however with poor correlations with tested frequency thresholds. Children with residual hearing showed significantly better auditory outcomes with CI, compared with those without residual hearing.
In children with congenital cochlear hearing loss, the objective CM intracochlear responses can reliably predict the residual audiometric threshold. However, in children with auditory neuropathy syndrome disorder, the CM thresholds did not match the behavioral audiometric responses. Postoperatively, children with recordable CM responses, showing preserved residual hearing, demonstrated better CI outcomes.