New Technique Locates Epilepsy Sources Other Methods Miss
Research by neurologists at Cincinnati Children’s finds that user-defined virtual sensor (UDvs) beamforming can pinpoint seizure onset zones (SOZ) beyond the temporal lobe. This new imaging technique locates SOZs that other methods fail to detect.
The results could improve surgical planning and positive outcomes for the 25% of patients with temporal lobe epilepsy (TLE) and temporal lobe plus epilepsy (TLE+) who continue to experience seizures after a temporal lobectomy. Children with TLE+ have a seizure onset zone that extends beyond the temporal lobe into other brain structures. These patients have a five-fold increased risk of seizures after epilepsy surgery.
Led by Jeffrey Tenney, MD, PhD, and Hansel Greiner, MD, with the Division of Neurology, the study was published in Epilepsia in December 2024.
A Solution for Locating Temporal Plus Epilepsy Sources
UDvs beamforming is a signal processing technique that enhances noninvasive magnetoencephalography (MEG) scans by more accurately pinpointing sources of neural activity within deep brain tissues.
In this study, MEG-based beamforming images were more effective than other methods at determining which patients would benefit from intracranial EEG (iEEG) monitoring before resection surgery.
The ability to distinguish between TLE and TLE+ before surgery is significant.
“This paradigm could preoperatively identify children with a TLE+ network who may benefit from iEEG prior to consideration of resection, and identify brain regions to be explored with iEEG,” study co-authors say.
The ability to identify and map a TLE+ network should lead to decreased failure rates in temporal lobe epilepsy surgery and improved seizure-free outcomes, the co-authors say.
Comparing Methods
The goal of this retrospective study was to determine whether a MEG virtual sensor approach was associated with a postoperative outcome and could make a presurgery distinction between TLE and TLE+.
Researchers looked at two related but independent methods:
- Novel UDvs beamforming, which relies on visual analysis by persons skilled at interpreting EEG/MEG and functional connectivity
- Graph theory—also called EC (eigenvector centrality)—which is computational and does not require skilled waveform interpretation
The study shows that UDvs beamforming is associated with a positive postsurgical outcome and presurgical epilepsy classification of TLE and TLE+.
Findings
- UDvs beamforming is highly sensitive at predicting interictal spikes—the abnormal electrical activity that occurs between seizures and is seen on iEEG. The identification of each abnormal location by UDvs increased the odds of seizures occurring after surgery by 22%.
- Typical connectivity-based MEG methods were not associated with surgical outcome.
- UDvs beamforming more precisely identifies TLE+. Each abnormal location identified increased the odds of TLE+ by 47%.
- MEG network analysis using EC showed a reasonable correlation with interictal spikes, but results were no better than MEG source analysis methods.
- Also, EC hubs were unrelated to postsurgical outcomes or TLE/TLE+ classification.
More Study Needed
Study authors say results support the use of UDvs in clinical practice as a complementary approach to enhance standard equivalent single dipole methods (a way to estimate the location of an electric source in the brain), such as ECD analysis.
“UDvs evaluation for patients with TLE or TLE+ syndromes could improve source localization across MEG centers,” co-authors say. Most MEG centers exclusively use single dipole analysis.
More study is needed to understand how UDvs beamforming could potentially improve surgical epilepsy planning.
(Published March 2025)
