Direct recording of electrically evoked cortical potentials from cochlear implants demonstrates feasibility and clinical relevance in pediatric users

Abstract

Intracochlear electrodes in cochlear implants (CIs) offer a novel method for recording auditory brain activity without external EEG equipment, addressing challenges in pediatric CI users. This study tested the feasibility of recording electrically evoked cortical auditory potentials (eCAEPs) directly via the CI system. Twenty children and three adults with bilateral Advanced Bionics CIs participated. A brief electrical stimulus was delivered to one CI, while the contralateral CI recorded responses using a basal electrode referenced to the case. Each session included stimulus and non-stimulus sweeps, with averaging over 600 ms revealing clear eCAEP patterns. All participants exhibited obligatory P1, N1, and P2 peaks within a test duration of under five minutes. The method showed good test-retest repeatability and expected latency shifts occurred with stimulus level adjustments. Compared to scalp recorded EEG, intracochlear recordings produced significantly larger amplitudes with similar latencies. Early implanted children displayed distinct eCAEP patterns, and better performing CI users had earlier P1 responses. This recording approach provides a robust, non-invasive tool for monitoring CI users, particularly young children, offering potential advancements in post-implantation assessment and intervention by eliminating external equipment while ensuring reliable recordings.

Keywords: Brain objective measure; Cortical auditory evoked potentials; Electrical stimulation; Intra-cochlear recordings; Pediatric; Scalp recordings.

Fig. 1

Shows the set up for Bilateral e-CAEP test configuration from the implant and the recording set up from a standard EP system. The red arrows indicate signals or data going in the software for processing, and the blue arrow indicate signals or data going out from the software.

Fig. 2

Shows the Sweep structure in each experimental trail. Each sweep contained to stages, the “null” stage where no stimulus was presented, and the “stim” stage where stimulus was presented.

Fig. 3

Illustrates the recording sequence as used in BEEP software, and its anticipated response for contralateral side (the recording and not stimulating side),

Fig. 4

Examples of eCAEP responses from 9 CI children. Responses were collected using the BEEP app. Each graph shows P1, N1, P2 components and is labeled with subject number. Details for those participants, including age and implant information, are shown in Table 1.

Fig. 5

eCAEPs recorded in three children, each stimulated via the right cochlear implant (CI). Recordings show contralateral (left, red) and ipsilateral (right, blue) to the stimulated CI. Note the prominent stimulus artifact in the ipsilateral recordings, which is not observed in the contralateral recordings. Details for participants S1–S23, including age and implant information, are shown in Table 1.

Fig. 6

Individual eCAEP for MCL and zero-intensity levels superimposed with the grand average (left side) of all 20 CI children. Note that the recording artifacts recorded at MCL and “null” current level are similar.

Fig. 7

P1 peak latencies of all 20 pediatric CI recipients in this study. Seventeen falls within normal range (red solid circles), one child showed early P1 latency (black solid circle) and the other two children longer P1 latencies (blue solid circles) as expected to their ages.

Fig. 8

Repeatability of eCAEP responses as in 6 individual children. The grand average recorded across 10 children is displayed in the mid of the figure. No statistical differences were found between the first and second eCAEP test. The blue plot is the first and red plot is the second as seen in the legend. Details for those participants, including age and implant information, are shown in Table 1.

Fig. 9

Test–retest repeatability within and between test sessions of eCAEP in two children with gap of number of months between them. Details of the participants S15 and S18 including age and implant information are shown in Table 1.

Fig. 10

Effect of stimulus level on eCAEP recorded directly from the CI of 6 children. Details for participants S6,S7,S14,S15,S16,S18, including age and implant information, are shown in Table 1.

Fig. 11

Comparison between the eCAEP as recorded via the CI and to the eCAEP recorded through scalp recorded electrodes and EEG system. Details for participants S10, S14-16, and S18 including age and implant information, are shown in Table 1.

Fig. 12

Grand average of eCAEP of children with maximal score of CAP superimposed on eCAEP of children with poorer CAP score.

Fig. 13

Box plot of the P1 peak latency in children with CAP score of 7 against a group of children using CI with poorer CAP score.

Fig. 14

An example of eCAEP of a pre-lingual children received CI early in life compared to two adults implanted at adults ages, post-lingual.