The implementation of electric source imaging and EEG/fMRI in presurgical evaluation of drug-resistant epilepsy

Epilepsy surgery is a secure and effective measure for Drug-Resistant Focal Epilepsy (DR-FE), however, it is currently underused. Precisely delineating the epileptogenic zone (EZ) is crucial for favorable outcomes. Technological advances have expanded the availability of two promising techniques such as Electric Source Imaging (ESI) and EEG/fMRI for presurgical epilepsy evaluation. These techniques primarily focus on studying epileptiform activity to localize irritative and EZ. They can also be exploited to study brain connectivity change across different situations. This study aims to implement ESI and EEG/fMRI in consecutive DR-FE patients, assess concordance with invasive techniques, and study post-surgery network rearrangements. Consecutive adult DR-FE patients admitted to an Epilepsy Monitoring Unit underwent pre-operative high-density EEG and EEG/fMRI. Concordance between ESI-EEG/fMRI and EZ was established in patients with defined EZ through sEEG or surgery. Partial concordance is also acknowledged. For ESI cortical connectivity (CC) and EEG/fMRI resting-state network (RSN), functional connectivity analyses are performed using graph-theory approaches. A cohort of 21 patients (mean age 32.7 years) was included, with EZ fully defined in 10, partially in 10, and not identified in 1. Six patients underwent surgery with positive outcomes. The 38% of patients had concordant ESI-EEG/fMRI results with EZ, 42% partially concordant, and 20% discordant. Regarding the accuracy of each techniques, in 33% of patients, both techniques were spatially concordant, with ESI exhibiting better performance in correctly localizing the lobe containing the EZ. In 38% of patients, only one technique was concordant, and in 19%, both techniques were discordant. Preliminary analysis showed widespread CC and RSN changes pre-and post-surgery, with decreased functional connectivity and network efficiency post-surgery.Improving patient referrals and organizational networks is essential to increase surgical candidates. Implementing advanced non-invasive techniques requires resource allocation, personnel training, and technical challenges. The complementary nature of non-invasive techniques seems to improve EZ delineation.