Results of cochlear implantation (CI) vary significantly among different patients. This variability depends on the functional integrity of the auditory nerve and structures of central auditory system, the location of the electrode array, and the performance of the implanted electronic device. An outcome of CI surgery is typically assessed using a battery of tests. The limitations of speech perception tests highlight the need for more objective outcome measures. With the rising numbers of CI surgeries in recent years, as well as the expansion of candidacy to wider groups of pediatric population, there is a greater need to standardize and optimize the surgical and diagnostic procedures to ensure consistent and favorable outcomes. Modern methods of computerized tomography and magnetic resonance imaging provide information about the location of electrodes, but they are powerless in determining the functional status of neural elements, the performance of the device, and predicting the results of CI. The electrophysiological methods provide registration of responses from structures at various levels of the auditory pathway to acoustic and electrical stimulation. Despite the certain advantages the widely used in clinical practice Neural Response Telemetry provides information only about the functional integrity of the auditory nerve fibres, which limits its ability to assess the state of overlying structures and explain the pronounced intra- and interindividual differences in CI results. This information can be obtained by recording the potentials of the brain stem and auditory cortex to electrical stimulation (EABR, ECAEP) which can more effectively activate the central auditory pathway, providing auditory perception and enabling development of speech perception skills.

At the pre-operative stage, a transtympanic EABR could be used as an effective clinical procedure which can decrease the likelihood of placing a cochlear implant in a non-stimulable ear and may provide the clinician with a valuable tool for selection of the most appropriate ear for implantation. Additionally, the intra-operative implant-evoked EABR with the use of test electrode is recommended to identify the site of lesion in patients with auditory neuropathy spectrum disorders (presynaptic vs. postsynaptic).

In CI patients, using the implant electrode, we can measure ECochG signals directly within the cochlea. Intraoperative intracochlear monitoring of the cochlear response (cochlear microphonic) to acoustic stimulation during CI shows promise as a tool to assist with hearing preservation.

It is emphasized that the presence of the CAEP P₁-N₁-P₂ complex with amplification can serve as an indicator of speech determination at the level of the auditory cortex. In addition, the possibility of using CAEP recording to assess the effectiveness of CI is being considered, and a high degree of correlation between CAEP thresholds and hearing thresholds is noted

The electrophysiological provide the valuable information about the auditory pathway including cochlear hair cells, auditory nerve, brainstem and auditory cortex. Using different objective measures at different stages of CI we can identify the site of lesion (presynaptic vs. postsynaptic), the auditory nerve functional integrity and understand considerable variance in postoperative performance of CI users.