Robustness of MEG source imaging in pediatric patients with surgical cavities: A case series
5 affiliations
- 1McGill University, 845 Sherbrooke Street West, Montreal, Quebec, H3A 0G4, Canada; Montreal Neurological Institute and Hospital, 3801 University Street, Montreal, Quebec, H3A 2B4, Canada
- 2University of Calgary, 2500 University Drive NW, Calgary, Alberta, T2N 1N4, Canada
- 3McGill University, 845 Sherbrooke Street West, Montreal, Quebec, H3A 0G4, Canada; Department of Pediatric Neurology, Montreal Children's Hospital, McGill University Health Centers, 1001 Boulevard Décarie, Montréal, Québec, H4A 3H9, Canada
- 4Department of Pediatric Neurology, Montreal Children's Hospital, McGill University Health Centers, 1001 Boulevard Décarie, Montréal, Québec, H4A 3H9, Canada
- 5McGill University, 845 Sherbrooke Street West, Montreal, Quebec, H3A 0G4, Canada; Montreal Neurological Institute and Hospital, 3801 University Street, Montreal, Quebec, H3A 2B4, Canada; Department of Pathology, McGill University Health Centre, 1001 Boulevard Décarie, Montreal, Quebec, H4A 3J1, Canada
Abstract
Background: Magnetoencephalography (MEG) is used to localize the epileptogenic zone (EZ) in children with drug-resistant epilepsy (DRE) undergoing pre-surgical evaluation. However, its accuracy may be compromised in patients with cerebrospinal fluid (CSF)-filled surgical cavities from prior failed resections. Finite element method (FEM) head models of tissue geometry and biophysics may better account for altered anatomy than the commonly used spherical approximations, but the added value in real clinical cases remains unclear. Objective: We evaluated the impact of head model choice on MEG source imaging (MSI) in pediatric DRE patients with pre-existing surgical cavities undergoing reoperation. Methods: We retrospectively analysed interictal and ictal events from four patients (ages 9–18) with prior failed epilepsy surgery who underwent MEG before a second or third resection. Dynamic statistical parametric mapping (dSPM) was applied to all six activity datasets. Equivalent current dipole (ECD) estimation retained dipoles for the four interictal datasets; neither ictal dataset yielded dipoles meeting the goodness-of-fit threshold. Source imaging used conventional overlapping-spheres (OS), boundary element method (BEM), advanced 3-layer FEM (3L-FEM), and 4-layer FEM (4L-FEM, including cavities) head models. EZ estimates were compared in terms of volume, EZ-cavity centroid distances, overlap (DICE coefficients), and agreement with the subsequent resection zone (RZ). Results: Within each mapping approach, distances from dSPM centroids and dipole locations to the cavity differed across head models by less than 1 cm for all but one activity dataset. Pairwise dSPM source-centroid distances reached 1.84 cm, and pairwise dipole distances reached 4.39 cm in one participant's MEG session. OS and BEM dSPM estimates were typically larger in volume than FEM counterparts, with FEM providing more spatially restricted sources. In the seizure-free cases, the dSPM source imaging from 3 out of 4 epileptiform events overlapped with the subsequent RZ. Computationally, OS models were generated within seconds, BEM models in ∼7 min, whereas 4L-FEM required >20 min per head model. Conclusions: In this pediatric epilepsy case series with surgical cavities, MSI showed broad agreement across simple spherical and advanced realistic head models. These findings did not establish a consistent localization advantage of one head model over another. However, larger prospective cohorts with independent ground truths are needed to validate and generalize these findings across cavity types and EZ locations.
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BibTeX
@article{hill2026robustness,
title = {{Robustness of MEG source imaging in pediatric patients with surgical cavities: A case series}},
author = {Eleanor Hill and Jeremy T. Moreau and Erica Minato and Marc Lalancette and Elisabeth Simard-Tremblay and Bernard Rosenblatt and Jason Karamchandani and Marie-Christine Guiot and Sylvain Baillet and Roy W.R. Dudley},
journal = {NeuroImage: Reports},
year = {2026},
month = oct,
doi = {10.1016/j.ynirp.2026.100423},
url = {https://doi.org/10.1016/j.ynirp.2026.100423},
note = {CC BY},
}
RIS
TY - JOUR
TI - Robustness of MEG source imaging in pediatric patients with surgical cavities: A case series
AU - Eleanor Hill
AU - Jeremy T. Moreau
AU - Erica Minato
AU - Marc Lalancette
AU - Elisabeth Simard-Tremblay
AU - Bernard Rosenblatt
AU - Jason Karamchandani
AU - Marie-Christine Guiot
AU - Sylvain Baillet
AU - Roy W.R. Dudley
PY - 2026
DA - 2026/10/23
JO - NeuroImage: Reports
DO - 10.1016/j.ynirp.2026.100423
UR - https://doi.org/10.1016/j.ynirp.2026.100423
AB - Background: Magnetoencephalography (MEG) is used to localize the epileptogenic zone (EZ) in children with drug-resistant epilepsy (DRE) undergoing pre-surgical evaluation. However, its accuracy may be compromised in patients with cerebrospinal fluid (CSF)-filled surgical cavities from prior failed resections. Finite element method (FEM) head models of tissue geometry and biophysics may better account for altered anatomy than the commonly used spherical approximations, but the added value in real clinical cases remains unclear. Objective: We evaluated the impact of head model choice on MEG source imaging (MSI) in pediatric DRE patients with pre-existing surgical cavities undergoing reoperation. Methods: We retrospectively analysed interictal and ictal events from four patients (ages 9–18) with prior failed epilepsy surgery who underwent MEG before a second or third resection. Dynamic statistical parametric mapping (dSPM) was applied to all six activity datasets. Equivalent current dipole (ECD) estimation retained dipoles for the four interictal datasets; neither ictal dataset yielded dipoles meeting the goodness-of-fit threshold. Source imaging used conventional overlapping-spheres (OS), boundary element method (BEM), advanced 3-layer FEM (3L-FEM), and 4-layer FEM (4L-FEM, including cavities) head models. EZ estimates were compared in terms of volume, EZ-cavity centroid distances, overlap (DICE coefficients), and agreement with the subsequent resection zone (RZ). Results: Within each mapping approach, distances from dSPM centroids and dipole locations to the cavity differed across head models by less than 1 cm for all but one activity dataset. Pairwise dSPM source-centroid distances reached 1.84 cm, and pairwise dipole distances reached 4.39 cm in one participant's MEG session. OS and BEM dSPM estimates were typically larger in volume than FEM counterparts, with FEM providing more spatially restricted sources. In the seizure-free cases, the dSPM source imaging from 3 out of 4 epileptiform events overlapped with the subsequent RZ. Computationally, OS models were generated within seconds, BEM models in ∼7 min, whereas 4L-FEM required >20 min per head model. Conclusions: In this pediatric epilepsy case series with surgical cavities, MSI showed broad agreement across simple spherical and advanced realistic head models. These findings did not establish a consistent localization advantage of one head model over another. However, larger prospective cohorts with independent ground truths are needed to validate and generalize these findings across cavity types and EZ locations.
SN - 2666-9560
ER -