Spatiotemporal Propagation of Magnetographic Interictal Spikes in Patients with Temporal Lobe Epilepsy
Abstract number :
2.03
Submission category :
3. Neurophysiology / 3D. MEG
Year :
2022
Submission ID :
2205031
Source :
www.aesnet.org
Presentation date :
12/4/2022 12:00:00 PM
Published date :
Nov 22, 2022, 05:27 AM
Authors :
Daniel Zhou, MD, MS – University of Nebraska Medical Center; Noam Peled, PhD – Harvard Medical School; Olga Taraschenko, MD – University of Nebraska Medical Center; Callisto Cordray, BA – University of Nebraska Medical Center; Steven Stufflebeam, MD – Harvard Medical School; Valentina Gumenyuk, PhD – University of Nebraska Medical Center
Rationale: Magnetoencephalography (MEG) source localization of interictal epileptiform spikes into clusters by equivalent current dipole (ECD) is the current standard of analysis for patients with medically refractory focal epilepsy. There is growing evidence that the propagation of spikes can represent the pathway of the epileptogenic network. We report a novel tool that maps and visualizes the spatiotemporal propagation of spikes in patients with temporal lobe epilepsy as well as those with additional extratemporal dipoles on clinical MEG analysis.
Methods: Following a retrospective analysis of MEG recordings (Elekta NeuromagTM, Helsinki, Finland) in patients with refractory epilepsy, three patients with isolated clusters of ECDs localized to the temporal lobe (temporal) and three with more diffuse clusters of ECDs in the temporal lobe with extention into the adjacent insula or parietal cortex (temporal plus) were selected. Demographic, clinical, and EEG information of patients were extracted from medical records. MEG source localization was performed using the ECD and Multi-Modality Analysis and Visualization Tool (MMVT). The first approach allowed to localize the peak of ten selected spikes by the ECD standard method; the dipoles were accepted if goodness of fit (GOF) >75% and Q < 500nAM. The second tool implemented the open-source dSPM inverse imaging algorithm to examine the temporal and spatial dynamics of spike- activity across >10 ms from the onset of averaged source generated by 10 spikes.
Results: Spikes detected on MEG data in a patient with temporal cluster (Patient 1, Figure 1) and temporal plus cluster (Patient 2, Figure 2) were processed using the dSPM inverse solution, and the average of the brain sources associated with spikes was normalized and statistically evaluated against baseline with no epileptiform activity (Figures 1A, 2A). Clusters of dipoles from the ECD method were mapped to the left temporal lobe in Patient 1 (Figure 1B) and the left temporal lobe and insular cortex in Patient 2 (Figure 2B). Heat maps were generated of the onset (yellow) and propagation (red) of the activity associated with spikes of both patients (Figures 1C, 2C) with the shift from yellow to red representing propagation of the source averaged spikes over 10 ms. Patient 1 (temporal) had spike onset restricted to the left temporal lobe. Patient 2 (temporal plus) had propagation of spike-activity from the temporal lobe to the plus regions (insula or temporoparietal). Analysis of the other patients is in process.
Conclusions: The patient with epilepsy originating from the temporal lobe who had the temporal plus presentation identified on clinical MEG evaluation (ECD method) may have spread of the epileptic network to the extratemporal regions with true epileptogenic onset originating in the temporal lobe. We demonstrate a novel tool can be used for the precise characterization of the spatiotemporal propagation of interictal spikes, allowing for more superior localization of the epileptogenic zone compared to the approach currently used in standard clinical analysis.
Funding: Not applicable
Neurophysiology