Assessing focal spiral ganglion neuron damage via electrically evoked compound action potentials II: Chronic degeneration
Wiebke S. Konerding - Department of Experimental Otology, Hannover Medical School (Role: Presenting Author)
 Julie G. Arenberg - Massachusetts Eye and Ear Infirmary, Harvard Medical School (Role: Co-Author)
 Andrej Kral - Department of Experimental Otology, Hannover Medical School, Cluster of Excellence ‘Hearing for All’ (Role: Co-Author)
 Peter Baumhoff - Department of Experimental Otology, Hannover Medical School (Role: Co-Author)
Objectives
Speech perception in CI users is likely influenced by heterogeneous degeneration of spiral ganglion neurons (SGN). However, the interpretation of human psychophysical and electrophysiological results is difficult, as reliable markers of locally restricted SGN damage are still missing. The aim of the study was to 1) assess the effect of chronic degeneration along the SGN, after focal micro lesions on electrical hearing and to 2) derive non-invasive, electrophysiological markers for the location and size of the SGN damage.
Methods
We used the guinea pig as animal model to quantify the change in electrically evoked compound action potential (eCAP) recordings 8-12 days after a ~500 µm degeneration of the SGN in the basal turn. Therefore, we compared 13 chronically lesioned ears to 8 intact, control ears for stimulation with a 6-contact CI, close to ‘ON’ and apical to ‘OFF’ the lesion. We used both the late N2P2 eCAP component to separate anodic-leading and cathodic-leading biphasic stimulation (monopolar mode) and the, clinically relevant, early N1P1 component to averaged polarities.
Results
The threshold, the maximal peak-to-peak amplitude and the threshold polarity effect (PE) were significantly distinct to those of healthy control ears. Thereby, only the threshold and a newly derived Max/Max-index were lesion specific: The chronic ears differed from the controls only for ‘ON’, but not for ‘OFF’ lesion stimulation. The Max/Max-index explained more than 60% of the variance in lesion size and was suitable to identify the contact closest to the lesion for all 10 ears with larger lesions. Reanalysing our acute micro-lesions, we revealed that the changes in Max/Max-index were specific to chronic degenerations.
Conclusion
We propose the Max/Max-index as a marker for locally restricted SGN degeneration that should be tested for its clinical applicability, using a multi-stage diagnostics, which can be performed without a priori knowledge on the presence/ or location of a lesion.
Supported by Hearing 4 All (DFG Exc. 2177), MHH-plus Foundation, and MedEl Company (Innsbruck).

Assessing focal spiral ganglion neuron damage via electrically evoked compound action potentials II: Chronic degeneration
**[Wiebke S. Konerding](mailto:konerding.wiebke@mh-hannover.de)** - Department of Experimental Otology, Hannover Medical School (Role: Presenting Author)
 [Julie G. Arenberg](mailto:jbierer@uw.edu) - Massachusetts Eye and Ear Infirmary, Harvard Medical School (Role: Co-Author)
 [Andrej Kral](mailto:kral.andrej@mh-hannover.de) - Department of Experimental Otology, Hannover Medical School, Cluster of Excellence ‘Hearing for All’ (Role: Co-Author)
 [Peter Baumhoff](mailto:baumhoff.peter@mh-hannover.de) - Department of Experimental Otology, Hannover Medical School (Role: Co-Author)
Objectives
Speech perception in CI users is likely influenced by heterogeneous degeneration of spiral ganglion neurons (SGN). However, the interpretation of human psychophysical and electrophysiological results is difficult, as reliable markers of locally restricted SGN damage are still missing. The aim of the study was to 1) assess the effect of chronic degeneration along the SGN, after focal micro lesions on electrical hearing and to 2) derive non-invasive, electrophysiological markers for the location and size of the SGN damage.
Methods
We used the guinea pig as animal model to quantify the change in electrically evoked compound action potential (eCAP) recordings 8-12 days after a ~500 µm degeneration of the SGN in the basal turn. Therefore, we compared 13 chronically lesioned ears to 8 intact, control ears for stimulation with a 6-contact CI, close to ‘ON’ and apical to ‘OFF’ the lesion. We used both the late N2P2 eCAP component to separate anodic-leading and cathodic-leading biphasic stimulation (monopolar mode) and the, clinically relevant, early N1P1 component to averaged polarities.
Results
The threshold, the maximal peak-to-peak amplitude and the threshold polarity effect (PE) were significantly distinct to those of healthy control ears. Thereby, only the threshold and a newly derived Max/Max-index were lesion specific: The chronic ears differed from the controls only for ‘ON’, but not for ‘OFF’ lesion stimulation. The Max/Max-index explained more than 60% of the variance in lesion size and was suitable to identify the contact closest to the lesion for all 10 ears with larger lesions. Reanalysing our acute micro-lesions, we revealed that the changes in Max/Max-index were specific to chronic degenerations.
Conclusion
We propose the Max/Max-index as a marker for locally restricted SGN degeneration that should be tested for its clinical applicability, using a multi-stage diagnostics, which can be performed without a priori knowledge on the presence/ or location of a lesion.
_Supported by Hearing 4 All (DFG Exc. 2177), MHH-plus Foundation, and MedEl Company (Innsbruck)._

Assessing focal spiral ganglion neuron damage via electrically evoked compound action potentials II: Chronic degeneration

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,