Stability of the Epileptogenic Index across seizures and the effects of sleep and withdrawal of anti-seizure medications.
7 affiliations
- 1Department of Biomedical Engineering, Tel Aviv University, Tel Aviv, Israel.
- 2EEG and Epilepsy Unit, Department of Neurology, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel.
- 3Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.
- 4Center for Advanced Imaging Innovation and Research (CAI2R), New York University Langone Medical Center, New York, New York, USA.
- 5Gray Faculty of Medical and Health Sciences, Tel Aviv University, Tel Aviv, Israel.
- 6Sagol Brain Institute, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel.
- 7Functional Neurosurgery Unit, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel.
Abstract
Objective
Epileptogenic Index (EI) is a promising index to evaluate the epileptogenicity of the brain tissue and is useful in planning epilepsy surgery. We aimed to evaluate whether EI maps are consistent across seizures within patients and whether EI-derived measures are affected by the vigilance state and anti-seizure medication (ASM) dose.Methods
We analyzed 127 stereoelectroencephalography (SEEG) seizures from 19 patients. EI was calculated in all seizures. Within-patient EI consistency was assessed using pairwise Spearman correlations between seizure-specific EI maps. To assess the effects of vigilance and ASM on EI consistency, we calculated a contact-level p_weighted EI score that combines the frequency of suprathreshold EI involvement and mean EI magnitude, separately across vigilance states and in a subset of patients with different ASM states.Results
Mean seizure-to-seizure EI correlations ranged from 0.11 to 0.81, indicating substantial variability in within-patient EI consistency. Seven patients showed high consistency (≥0.6) and four showed low consistency (≤0.3). At the contact level, no differences in p_weighted EI were found between wakefulness and sleep. In contrast, p_weighted EI was significantly higher during reduced ASM compared with full ASM doses.Significance
EI maps are not uniformly stable across seizures. ASM reduction may broaden or intensify EI-defined epileptogenic involvement, suggesting that ASM status should be considered when interpreting EI during SEEG evaluation. These findings are hypothesis-generating and require prospective validation to determine their clinical utility for surgical planning.Plain language summary
The Epileptogenic Index (EI) measures the involvement of a recorded brain area during a specific seizure. This study shows that EI patterns can vary significantly between different seizures in the same patient. While sleep states do not change these patterns, reducing a patient's anti-seizure medications increases EI values, making seizures appear to spread more broadly. These medication-induced changes must be carefully considered to accurately map the epileptic network for surgical decisions.
Related
- Epilepsy domain adapted large language models enhance epileptogenic zone prediction from seizure semiology
- Risk of orofacial clefts in offspring following maternal exposure to anti-seizure medications in a UK CPRD GOLD observational study
- Modulation of planarian seizure-like activity via antiseizure medications
- Pharmacokinetic changes and seizure outcomes in pregnant women taking second-generation antiseizure medications
- Diffusion MRI abnormalities localise the epileptogenic zone in paediatric drug-resistant epilepsy
BibTeX
@article{baron2026stability,
title = {{Stability of the Epileptogenic Index across seizures and the effects of sleep and withdrawal of anti-seizure medications.}},
author = {May Bar-On and Noam Ben-Eliezer and Noam Fallik and Lilac Goldstein and Guy Gurevitch and Ido Strauss and Inbal Maidan and Firas Fahoum},
journal = {Epilepsia open},
year = {2026},
month = oct,
doi = {10.1002/epi4.70351},
url = {https://europepmc.org/article/MED/42924597},
note = {CC BY-NC-ND},
}
RIS
TY - JOUR
TI - Stability of the Epileptogenic Index across seizures and the effects of sleep and withdrawal of anti-seizure medications.
AU - May Bar-On
AU - Noam Ben-Eliezer
AU - Noam Fallik
AU - Lilac Goldstein
AU - Guy Gurevitch
AU - Ido Strauss
AU - Inbal Maidan
AU - Firas Fahoum
PY - 2026
DA - 2026/10/23
JO - Epilepsia open
DO - 10.1002/epi4.70351
UR - https://europepmc.org/article/MED/42924597
AB - Objective Epileptogenic Index (EI) is a promising index to evaluate the epileptogenicity of the brain tissue and is useful in planning epilepsy surgery. We aimed to evaluate whether EI maps are consistent across seizures within patients and whether EI-derived measures are affected by the vigilance state and anti-seizure medication (ASM) dose.Methods We analyzed 127 stereoelectroencephalography (SEEG) seizures from 19 patients. EI was calculated in all seizures. Within-patient EI consistency was assessed using pairwise Spearman correlations between seizure-specific EI maps. To assess the effects of vigilance and ASM on EI consistency, we calculated a contact-level p_weighted EI score that combines the frequency of suprathreshold EI involvement and mean EI magnitude, separately across vigilance states and in a subset of patients with different ASM states.Results Mean seizure-to-seizure EI correlations ranged from 0.11 to 0.81, indicating substantial variability in within-patient EI consistency. Seven patients showed high consistency (≥0.6) and four showed low consistency (≤0.3). At the contact level, no differences in p_weighted EI were found between wakefulness and sleep. In contrast, p_weighted EI was significantly higher during reduced ASM compared with full ASM doses.Significance EI maps are not uniformly stable across seizures. ASM reduction may broaden or intensify EI-defined epileptogenic involvement, suggesting that ASM status should be considered when interpreting EI during SEEG evaluation. These findings are hypothesis-generating and require prospective validation to determine their clinical utility for surgical planning.Plain language summary The Epileptogenic Index (EI) measures the involvement of a recorded brain area during a specific seizure. This study shows that EI patterns can vary significantly between different seizures in the same patient. While sleep states do not change these patterns, reducing a patient's anti-seizure medications increases EI values, making seizures appear to spread more broadly. These medication-induced changes must be carefully considered to accurately map the epileptic network for surgical decisions.
SN - 2470-9239
ER -