Objective Measures at Different Stages of Cochlear Implantation: A Data Analysis

Objectives: The aim of this literature review was to summarize the results of scientific publications on the use of objective electrophysiological methods at different stages of cochlear implantation. The following aspects were evaluated: usefulness of electrocochleography and auditory evoked brainstem response registration to electrical stimulation for candidates’ selection for cochlear implantation; application of neural response telemetry, auditory evoked brainstem response registration and contralateral stapedial muscle reflexes to electrical stimulation as well as intracochlear electrocochleography to acoustic stimulation during implantation; the use of these methods and cortical auditory evoked potentials at the post-surgery stage for monitoring the cochlear implantation outcomes and controlling the speech processor adjustment. Results: A search was conducted in PubMed and CINAHL databases up to August 2024 to locate articles related to the electrocochleography and auditory brainstem responses measured before, during and after cochlear implantation and cortical auditory evoked potentials – after cochlear implantation. The quality of studies was evaluated using the National Institute of Health (NIH) “Study Quality Assessment Tool for Case Series Studies”. A total 186 articles were included for the systematic review including 72 studies devoted to neural response telemetry, 29 – to electrically evoked auditory brainstem response registration, 41 – to intracochlear electrocochleography, 34 – to cortical auditory evoked responses in implanted patients and 10 – to contralateral stapedial muscle reflexes to electrical stimulation during and after cochlear implantation. Based on the analysis of the reviewed publications the optimal sets of objective measurements at different stages of cochlear implantation are recommended. Conclusions: The battery of the objective audiological methods provides the electrically evoked auditory nerve compound action potential threshold determination at different electrodes of cochlear implant which can be used for the precise speech processor mapping, including investigation of amplitude growth function, excitation summation, spread of excitation and recovery function. The intracochlear electrocochleography to acoustic stimulation provides real-time feedback intraoperatively and has a potential clinical value to monitor the status of hearing preservation. Additional information could be obtained with estimation of auditory evoked brainstem response thresholds to electrical stimulation before, during and after implantation. The invaluable information for the estimation of cochlear implantation effectiveness can be obtained by registration of cortical auditory evoked potentials to acoustic and electrical stimulation which is based on the analysis of the P1-N1-P2 complex.