Noninvasive localization plays an important role in accurate seizure localization for patients with medically refractory focal epilepsy.  ESI and has been shown to correlate well with surgical area of resection. We report the concordance between ESI and intracranial EEG in a cohort of 20 patients.

 To evaluate EEG source imaging (ESI) from standard long-term video-EEG recording in patients who underwent intracranial monitoring.

 Patients were selected who had ESI performed and  subsequent intracranial monitoring (ICM).  ESI and intracranial seizure onset zone (SOZ) were localized to sublobar regions, and concordance was determined for each ESI analysis.  Minimum (at least one ESI concordant) and complete (all ESI concordant) concordance was determined for each patient. Agreement between ESI and ICM in identifying multifocal SOZ was analyzed.

Twenty patients had a total of 56 ESI analyses, 32 ictal and 24 interictal. There was no significant difference in concordance between ictal (78%) and interictal (58%) analyses. However, when patients with multifocal SOZ were excluded, ictal analyses were significantly more concordant (83% vs 50%, p<0.05). Concordance was not significantly different between temporal (73%) and extratemporal SOZ (63%). Minimal concordance was seen in 95% of patients and complete concordance in 55%. There was no significant difference in minimal or complete concordance between patients with ictal and interictal discharges or patients with temporal and extratemporal SOZ.  

  EEG source imaging from prolonged EEG monitoring shows favorable concordance with SOZ identified by intracranial EEG. Ictal analyses were more likely than interictal to be concordant with ICM.  The majority of patients had all ictal analyses concordant with ICM, with a trend towards lower concordance for interictal analyses.