Objectives:
The use of objective measures in cochlear implant (CI) mapping, has greatly contributed to the refinement of the setting of audible and comfortable stimulation levels, which serve as the basis of the mapping process, especially in cases of infants and young children. In addition, objective measures can also confirm the integrity of the CI system. Current CI objective measures mainly reflect neural activity from the auditory nerve and brainstem site. An objective cortical CI measure that reflects directly central auditory activity is greatly needed, especially since it is closely related to CI outcomes in both children and adults. Recording the brain activity currently requires an external evoked potential (EP) system including scalp electrodes, rendering it impractical for widespread clinical use. This study aimed to assess the feasibility of recording Cortical Auditory Evoked Potentials (CAEPs) directly and solely through the cochlear implant in response to external acoustic stimulation in the non-implanted ear.
Design:
A total of 9 CI users (4 females and 5 males) participated, including 7 post-lingual adults (23-72 years), and two pediatric cases, one teenager (15 years), and one child (8 years) - both pre-lingual. All participants had a residual hearing in the ear contralateral to the ear with CI. CAEPs were recorded in the implanted ear in response to acoustic stimulation of the non-implanted ear, consisting of a brief tonal stimulus at comfortable listening levels. Recordings used an intracranial montage consisting of an intracochlear apical electrode (active) and one of the two (case and ring) extra-cochlear implanted electrodes serving as reference electrodes. The CI CAEPs were compared to a single-channel conventional CAEP recording obtained simultaneously via scalp electrodes (Fz-mastoid) using a standard EP system and an external trigger from the CI system. Statistical comparisons were made between the CI and the scalp recorded CAEPs and for differences between the CI CAEP measures acquired using the ring and the case as the reference electrode.
Results:
CAEPs recorded directly and solely through the CI were equivalent to the standard scalp recorded CAEP responses. CAEP responses acquired using the caseelectrode as the reference were highly correlated in terms of morphology, latencies, and amplitudes of the CAEP components. The CI CAEP latencies of the two pediatric cases were consistent with their normal developed age group and delayed relative to adult CAEP latencies, as expected.
Conclusions:
This study demonstrated the feasibility of recording long latency CAEPs directly and solely through CI in adults with residual hearing, in response to acoustic stimulation of the non-implanted ear. The CI CAEPs closely resembled the CAEPs recorded simultaneously by an external EP system and via scalp electrodes. The ability to record directly from the implant, without the need of an external recording system, presents an innovative method with many clinical and research implications.

**Objectives:**
The use of objective measures in cochlear implant (CI) mapping, has greatly contributed to the refinement of the setting of audible and comfortable stimulation levels, which serve as the basis of the mapping process, especially in cases of infants and young children. In addition, objective measures can also confirm the integrity of the CI system. Current CI objective measures mainly reflect neural activity from the auditory nerve and brainstem site. An objective cortical CI measure that reflects directly central auditory activity is greatly needed, especially since it is closely related to CI outcomes in both children and adults. Recording the brain activity currently requires an external evoked potential (EP) system including scalp electrodes, rendering it impractical for widespread clinical use. This study aimed to assess the feasibility of recording Cortical Auditory Evoked Potentials (CAEPs) directly and solely through the cochlear implant in response to external acoustic stimulation in the non-implanted ear.
**Design:**
A total of 9 CI users (4 females and 5 males) participated, including 7 post-lingual adults (23-72 years), and two pediatric cases, one teenager (15 years), and one child (8 years) - both pre-lingual. All participants had a residual hearing in the ear contralateral to the ear with CI. CAEPs were recorded in the implanted ear in response to acoustic stimulation of the non-implanted ear, consisting of a brief tonal stimulus at comfortable listening levels. Recordings used an intracranial montage consisting of an intracochlear apical electrode (active) and one of the two (**_case_** and **_ring_**) extra-cochlear implanted electrodes serving as reference electrodes. The CI CAEPs were compared to a single-channel conventional CAEP recording obtained simultaneously via scalp electrodes (Fz-mastoid) using a standard EP system and an external trigger from the CI system. Statistical comparisons were made between the CI and the scalp recorded CAEPs and for differences between the CI CAEP measures acquired using the **_ring_** and the **_case_** as the reference electrode.
**Results:**
CAEPs recorded directly and solely through the CI were equivalent to the standard scalp recorded CAEP responses. CAEP responses acquired using the **case**electrode as the reference were highly correlated in terms of morphology, latencies, and amplitudes of the CAEP components. The CI CAEP latencies of the two pediatric cases were consistent with their normal developed age group and delayed relative to adult CAEP latencies, as expected.
**Conclusions:**
This study demonstrated the feasibility of recording long latency CAEPs directly and solely through CI in adults with residual hearing, in response to acoustic stimulation of the non-implanted ear. The CI CAEPs closely resembled the CAEPs recorded simultaneously by an external EP system and via scalp electrodes. The ability to record directly from the implant, without the need of an external recording system, presents an innovative method with many clinical and research implications.

A Novel Brain Objective Measure: Auditory Cortical Potentials Recorded only by the CI- Neurophysiological and Clinical Correlates

It is with great pleasure and enthusiasm, that on behalf of the Cochlear Implant centers of the Radboud UMC in Nijmegen and Erasmus MC Sophia Children’s Hospital in Rotterdam to invite you to attend the 16th European Symposium on Pediatric Cochlear Implantation to Rotterdam, the Netherlands in 2023.

Yours sincerely, on behalf of the CI Centers at Radboud UMC and Erasmus MC,