Characterizing MEG-Unique Discharges: Are They Normal? Simultaneous 64-Channel EEG–MEG Data from Healthy Subjects
Abstract number :
1.557
Submission category :
3. Neurophysiology / 3D. MEG
Year :
2025
Submission ID :
1311
Source :
www.aesnet.org
Presentation date :
12/6/2025 12:00:00 AM
Published date :
Authors :
Presenting Author: Jiechuan Ren, MD – Beijing Tiantan Hospital, Capital Medical University
Chunqing Yang, BS – Beijing Tiantan Hospital, Capital Medical University
Guoping Ren, MD – Beijing Tiantan Hospital, Capital Medical University
Cai Yuan, MD – Beijing Tiantan Hospital, Capital Medical University
Shuxian Zhou, BS – Beijing Tiantan Hospital, Capital Medical University
Xiaoqiu Shao, MD – Beijing Tiantan Hospital, Capital Medical University
Zhimei Li, MD – Beijing Tiantan Hospital, Capital Medical University
Thandar Aung, MD – University of Pittsburgh Medical Center
Qun Wang, MD – Beijing Tiantan Hospital, Capital Medical University
Rationale: Unlike electroencephalography (EEG), there are no established criteria for normal variants in MEG, and interpretation largely relies on EEG-based patterns. With the increasing use of MEG in presurgical evaluation, so-called ‘MEG-unique discharges’ have been reported, typically localized to the perisylvian, supramarginal and perirolandic regions in patients with drug resistant epilepsy (DRE); however, their clinical significance remains uncertain. To clarify their nature and enhance MEG interpretation for surgical candidates, we investigated these variants in neurologically normal individuals.
Methods: Under IRB approval from Beijing Tiantan Hospital, we recruited a group of healthy subjects without structural brain abnormalities, neurological or psychiatric disorders, or severe systemic disease. In addition to T1 weighted MRI, simultaneous one hour EEG-MEG recordings were acquired using a 306-channel whole-head MEG system with 64-channel scalp EEG (MEGIN Neuromag TRIUX: 102 magnetometers, 204 gradiometers; sampling rate 2000 Hz). Following the criteria for MEG-unique normal variants described by Rampp et al. published in Journal of clinical neurophysiology 37(6): 518-536, two experienced neurophysiologists independently reviewed the EEG-MEG data. MEG discharges corresponding to known EEG normal variants were excluded. Discrepant waveforms were jointly reviewed and discarded if consensus was not reached. Using a single equivalent current dipole model, dipoles meeting the following criteria, goodness-of-fit >80%, reduced χ² < 2, confidence volume < 1000 mm³, and dipole moment between 100–500 nAm, were localized and classified based on their location: supramarginal gyrus (SMG group); insula and opercular regions (perisylvian group); precentral and postcentral gyri (perirolandic group); and basal and inferior temporal regions (basal temporal group). Figure 1 shows representative waveforms, contour maps, and MRI dipole localizations for each group.
Neurophysiology