Comparative Analysis of Cortical Auditory Evoked Potential in Cochlear Implant Users

Abstract

Objectives:The primary goal of the study was to investigate electrical cortical auditory evoked potentials (eCAEPs) at maximum comfortable level (MCL) and 50% MCL on three cochlear implant (CI) electrodes and compare them with the acoustic CAEP (aCAEPs), in terms of the amplitude and latency of the P1-N1-P2 complex. This was achieved by comparing the eCAEP obtained with the method described and stimulating single electrodes, via the fitting software spanning the cochlear array and the aCAEP obtained using the HEARLab system at four speech tokens.Design: Twenty MED-EL (MED-EL Medical Electronics, Innsbruck, Austria) CI adult users were tested. CAEP recording with HEARLab System was performed with speech tokens /m/, /g/, /t/, and /s/ in free field, presented at 55 dB SPL. eCAEPs were recorded with an Evoked Potential device triggered from the MAX Programming Interface (MED-EL Medical Devices) with 70 msec electrical burst at 0.9 Hz at the apical (1), middle (6), and basal (10 or 11) CI electrode at their MCL and 50% MCL.Results: CAEP responses were recorded in 100% of the test subjects for the speech token /t/, 95% for the speech tokens /g/ and /s/, and 90% for the speech token /m/. For eCAEP recordings, in all subjects, it was possible to identify N1 and P2 peaks when stimulating the apical and middle electrodes. This incidence of detection decreased to an 85% chance of stimulation at 50% MCL on the same electrodes. A P1 peak was less evident for all electrodes. There was an overall increase in latency for stimulation at 50% MCL compared with MCL. There was a significant difference in the amplitude of adjacent peaks (P1-N1 and N1-P2) for 50% MCL compared with MCL. The mean of the maximum cross-correlation values were in the range of 0.63 to 0.68 for the four speech tokens. The distribution of the calculated time shift, where the maximum of the cross-correlation was found, was distributed between the speech tokens. The speech token /g/ had the highest number of valid cross-correlations, while the speech token /s/ had the lowest number. Conclusions:This study successfully compared aCAEP and eCAEP in CI users. Both acoustic and electrical P1-N1-P2 recordings obtained were clear and reliable, with good correlation. Latency increased with decreasing stimulation level, while amplitude decreased. eCAEP is potentially a better option to verify speech detection at the cortical level because it (1) uses direct stimulation and therefore creates less interference and delay of the sound processor and (2) creates more flexibility with the recording setup and stimulation setting. As such, eCAEP is an alternative method for CI optimization.

Cortical auditory evoked potential in cochlear implant users: An objective method to improve speech perception

“…It is also possible that CAEPs are affected by the bandwidth and duration of the stimulus. According to the HEARLab manual, /s/ has the stimulus duration of 50ms, /g/ 20 ms, /t/ 30 ms, and /m/ 30 ms. As reported by Tavora-Vieira et al ( 2021), the artifact of the HEARLab recordings starts from 0 ms onwards, and it is larger for the speech token /s/, probably due to the longer stimulus duration [43]. Nevertheless, clinicians might consider working with these CI users to gradually improve their acceptance to high frequencies sounds to see if a CAEP response can be elicited.…”

Single-Sided Deafness: Using Cortical Auditory Evoked Potential to Improve Cochlear Implant Fitting

“…Távora-Vieira et al (31) demonstrated that in experienced CI users with SSD, aided aCAEPs could be recorded successfully when the contralateral ear was masked. The results indicated that aCAEPs could potentially be used as a clinical tool to facilitate verification of MCLs in adults.…”

Electrically Evoked Auditory Late Responses as a Novel Method for Cochlear Implant Programming

“…It is difficult to determine whether different response patterns are due to neurophysiologic processing or the speech processor. Using direct electrical stimulus instead of acoustic stimulus eliminates these differences (12,13). Current studies have shown that eALR latency and amplitudes have good test-retest reliability in moderate to short-term (14,15).…”