Unexpected inadequate speech intelligibility with cochlear implant (CI) in an 81-year-old female patient with progressive hearing loss.

Abstract

The patient complained of a slowly progressive bilateral hearing loss, which could not be treated with conventional hearing aids (HA) for more than 10 years. Our examination revealed a profound bilateral sensorineural hearing loss. Although right-sided low-frequency hearing residuals up to 35 dB HL at 0.25 kHz were present, right-sided HA resulted in a Monosyllabic speech of 0% at 65 dB SPL Otoacoustic emissions were not detectable. There were no absolute or relative contraindications to CI fitting. We performed right cochlear implantation via round window insertion without complications. All intraoperative objective audiological measurements (Electrically Evoked Compound Action Potentials (ECAP), Spread of Excitation), as well as the intraoperative position control of the CI electrode by X-ray were regular. At initial fitting, the ECAP threshold was 145 CL. Subsequently, ECAP threshold-based fitting was performed. Loudness scaling was only feasible in a broadband manner. Initially, however, no speech understanding was possible, only noise perception. With this unexpectedly poor result, the indication for electrically evoked brainstem potential measurement (eBERA) was given. This is an electrophysiological method to determine amplitudes and latencies of the auditory nerve response via a CI. Stimulus-correlated potentials were derivable in eBERA. However, both absolute and inter-peak latencies eJ5 and eJ3 were prolonged. This is evidence for an additional existing auditory neuropathy, which explains the poor performance with CI. At 17 months after unilateral CI fitting, the Monosyllabic speech at 65 dB SPL was 25% below the expected result.