Career Center AES Connect

Abstracts

Respective Contribution of Ictal and Interictal Electrical Source Imaging to Epileptogenic Zone

Abstract number : 2.505
Submission category : 5. Neuro Imaging / 5B. Functional Imaging
Year : 2024
Submission ID : 1400
Source : www.aesnet.org
Presentation date : 12/8/2024 12:00:00 AM
Published date :

Authors :
Estelle RIKIR, MD, PhD – Hopital Universitaire de Bruxelles
Louis MAILLARD, MD, PhD – IMoPA Neuroscience, CNRS UMR 7365
chifaou ABDALLAH, MD, PhD – McGill University
Martine GAVARET, MD, PhD – Université Paris Cité, INSERM UMR 1266
Jean-Pierre VIGNAL, MD – CHRU Nancy, Neurology department
Sophie COLNAT-COULBOIS, MD, PhD – IMoPA Neuroscience, CNRS UMR 7365
Presenting Author: Laurent KOESSLER, PhD – IMoPA Neuroscience, CNRS UMR 7365


Rationale:

Pre-surgical evaluation of focal refractory epilepsy aims to localize and delineate the cortical region primarily involved in the generation of seizures i.e. the epileptogenic zone (EZ). During the last two decades, several studies have demonstrated the accuracy of non-invasive electromagnetic source imaging techniques and have assessed their clinical usefulness compared to standard pre-surgical evaluation. Interictal electrical source imaging (ESI) encompasses a risk of false localization due to complex relationships between irritative and epileptogenic networks. The purposes of our study were to prospectively evaluate and compare the respective contribution (sensitivity and specificity) of electrical source imaging derived from ictal and inter-ictal EEG discharges to localize the EZ using SEEG as the reference method. We further evaluated and compared ictal ESI results in different subgroups classified according to the morphology of the ictal pattern, the pres- ence or absence of a MRI lesion and the presumed etiology.

 



Methods:

We prospectively analyzed 54 of 78 enrolled patients undergoing pre-surgical investigation for refractory epilepsy. Ictal and inter-ictal ESI results were interpreted blinded to- and subse- quently compared with stereoelectroencephalography as a reference method. Anatomical concordance was assessed at a sub-lobar level. Sensitivity and specificity of ictal, inter-ictal and ictal plus inter-ictal ESI were calculated and compared according to the different subgroups.



Results:

Sensitivity and specificity of ictal, inter-ictal and ictal plus inter-ictal ESI were calculated and compared according to the different subgroups. Inter-ictal and ictal ESI sensitivity (84% and 75% respectively) and specificity (38% and 50% respectively) were not statistically different. Regarding the sensitivity, ictal ESI was never higher than inter-ictal ESI. Regarding the specificity, ictal ESI was higher than inter-ictal ESI in malformations of cortical development (MCD) (60% vs. 43%) and in MRI positive patients (49% vs. 30%). Within the ictal ESI analysis, we showed a higher specificity for ictal spikes (59%) and rhythmic discharges > 13 Hz (50%) than rhythmic discharges < 13 Hz (37%) and (ii) for MCD (60%) than in other etiologies (29%).



Conclusions:

This prospective study with a strictly uniform methodology does not show a better overall sensitivity and specificity of ictal compared to inter-ictal ESI but demonstrates the relevance of (i) a distinct inter-ictal and ictal analyses and (ii) a combined interpretation of both electrical source localizations. Inter-ictal analysis gave the highest sensitivity whereas ictal analysis gave the highest specificity. Inter-ictal ESI would be particularly interesting in MRI negative (supposed FCD) patients while ictal analy- sis would be considered primarily in (i) MCD patients and/ or with an MRI lesion, and, (ii) initial spike or rhythmic discharge > 13 Hz as ictal EEG pattern.

 



Funding:

Estelle Rikir was supported by a grant from the Medical Council of the CHU of Liège, Belgium.
This study was supported by the French Ministry of Health (PHRC 17-05, 2009).

 



Neuro Imaging