gms | German Medical Science

26. Jahrestagung der Deutschen Gesellschaft für Audiologie

Deutsche Gesellschaft für Audiologie e. V.

06.03. - 08.03.2024, Aalen

Time course of ECAP slope and loudness perception at different IPG values: A prospective study in 8 patients

Meeting Abstract

  • presenting/speaker Max Blümer - Universitätsklinikum Hamburg-Eppendorf, Klinik und Poliklinik für Hals-, Nasen- und Ohrenheilkunde, Hamburg, Germany
  • Konrad Schwarz - MED-EL Elektromedizinische Geräte GmbH, Innsbruck, Austria
  • Alexander Elsholz - Universitätsklinikum Hamburg-Eppendorf, Klinik und Poliklinik für Hals-, Nasen- und Ohrenheilkunde, Hamburg, Germany
  • Anne Schröder - MED-EL Elektromedizinische Geräte Deutschland GmbH, Starnberg, Germany
  • Mark Praetorius - Universitätsklinikum Hamburg-Eppendorf, Klinik und Poliklinik für Hals-, Nasen- und Ohrenheilkunde, Hamburg, Germany

Deutsche Gesellschaft für Audiologie e.V.. 26. Jahrestagung der Deutschen Gesellschaft für Audiologie. Aalen, 06.-08.03.2024. Düsseldorf: German Medical Science GMS Publishing House; 2024. Doc074

doi: 10.3205/24dga074, urn:nbn:de:0183-24dga0741

Published: March 5, 2024

© 2024 Blümer et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 License. See license information at http://creativecommons.org/licenses/by/4.0/.


Outline

Text

Introduction: ECAPs can be used to estimate cochlear health [1]. For this purpose, responses to stimuli with 30 µs IPG and 2.1 µs IPG are typically compared. Earlier studies have demonstrated a steeper ECAP slope for stimulations with 30 µs IPG compared to 2.1 µs [1]. Furthermore, loudness perception is increased when measuring ECAPs with 30µs IPG vs. 2.1µs with otherwise identical stimulation intensities [2]. Knowingly, post-op ECAP function and loudness perception change over time [3]. Both are evaluated in this study.

Methods: The stimulation comprised continuous, biphasic rectangular pulses (phase duration 40 µs) with alternating phases and steadily increasing amplitude (0–750 µA in 20 seconds). During each session, the IPG was varied: 30 µs/2.1 µs. The respective measurement of the paradigms was aborted at a stimulation intensity of 30 nC if the parameterization was not successful beforehand. Loudness perception was recorded in parallel using a continuous scaling procedure [scale 0–1]. Measurement time points were: 0 months (intra-op), 1 and 3 months post-op.

Results: The pooled median ECAP thresholds (eTHR) was decreasing intra-op vs. 3 months post-op for IPG 30 µs and for 2.1 µs. The median ECAP slope (eSLOPE) was increasing over time for 30 µs IPG and stable for 2.1 µs. For all cochlear regions, steeper median eSLOPEs were found for 30 µs IPG after 3 months compared to intra-op whereas median eSLOPEs were stable for 2.1 µs IPG.

Differences in median perception thresholds (pTHR) were found between 30 µs IPG vs. 2.1 µs at 1 and 3 months. For all regions and over time the median pTHR were stable. Maximum loudness was higher and maximum stimulation intensity was lower for 30 µs IPG vs 2.1 µs at 1 and 3 months. Whereas the maximum stimulation intensity was similar over all regions, loudness percept was highest in the apex > base > middle, for both IPG and keeping this order over time.

Discussion: Our results show the expected change over time for eTHR. Furthermore, an increase of eSLOPE for IPG 30 µs was observed. The louder percept for 30 µs vs. 2.1 µs is partly hidden by a reduced stimulation intensity necessary for ECAP parametrization. In the apex, loudness percept was found to be highest compared to other regions at same stimulation intensities. This is in good agreement with the steepest slopes indicating a higher number of recruited nerve fibres.


References

1.
Ramekers D, Versnel H, Strahl SB, Smeets EM, Klis SF, Grolman W. Auditory-nerve responses to varied inter-phase gap and phase duration of the electric pulse stimulus as predictors for neuronal degeneration. J Assoc Res Otolaryngol. 2014 Apr;15(2):187-202. DOI: 10.1007/s10162-013-0440-x External link
2.
Pieper SH, Brill S, Bahmer A. Loudness Perception and Dynamic Range Depending on Interphase Gaps of Biphasic Pulses in Cochlear Implants. Ear Hear. 2020 Sep/Oct;41(5):1251-7. DOI: 10.1097/AUD.0000000000000843 External link
3.
Lambriks L, van Hoof M, Debruyne J, Janssen M, Hof J, Hellingman K, Devocht E, George E. Toward neural health measurements for cochlear implantation: The relationship among electrode positioning, the electrically evoked action potential, impedances and behavioral stimulation levels. Front Neurol. 2023 Feb 9;14:1093265. DOI: 10.3389/fneur.2023.1093265 External link