Utility of Electrical Source Imaging in Surface-Inaccessible Epileptic Foci: Focus on Basifrontal and Cingulate Epilepsies

Background: Epilepsy is a chronic disorder with nearly one-third of patients developing drug-resistant epilepsy (DRE). Accurate localization of the epileptogenic zone (EZ) is critical for successful epilepsy surgery, yet remains challenging in surface-inaccessible deep-seated epilepsies such as basifrontal and cingulate regions, which often limit accurate localization using conventional scalp electroencephalography (EEG). While magnetoencephalography (MEG) provides better spatial resolution, it is costly, less accessible, and limited for deep sources. Electrical source imaging (ESI), using scalp EEG and computational modeling, offers a cost-effective and widely available noninvasive alternative. Objective: To evaluate the clinical utility of ESI in localizing the EZ in basifrontal and cingulate epilepsies by correlating source localization with surgical resection and postoperative outcomes. Methods: This retrospective study included 29 patients with DRE who underwent epilepsy surgery at Amrita Institute of Medical Sciences, Kochi, Kerala, India (2014–2024). Inclusion criteria : Patients who underwent epilepsy surgery involving the basifrontal or cingulate cortex and at least 1-year follow-up. ESI was performed using equivalent current dipole (ECD) methods. Localization concordance with the resection cavity was assessed and correlated with surgical outcomes (Engel classification). Results: Favorable outcomes (Engel I–II) were observed in 62.1% of patients. ECD showed concordant localization with surgical resection cavity in 20 cases, with 80% achieving favorable outcomes. This association was statistically significant ( p = 0.010). ECD demonstrated high sensitivity (88.89%), specificity (63.64%), and overall accuracy (79.31%), with a strong odds ratio of 14.0 (95% confidence interval: 2.06–95.09), indicating a robust association with surgical success. Conclusion: ESI is a valuable noninvasive tool in presurgical evaluation in surface-inaccessible deep-seated epilepsies, showing significant predictive value for surgical outcomes and supporting its role in guiding epilepsy surgery. It serves as an effective and accessible alternative to MEG in challenging epilepsy cases. Publication History Article published online: 15 July 2026 © 2026. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/) Thieme Medical and Scientific Publishers Private Limited A-13A, Graphix Tower 1, 6th floor, Sector 62, Noida 201309, Uttar Pradesh, India