Background:  A portion of children diagnosed with epilepsy will not respond to medication.  As a curative measure, clinicians might recommend to surgically remove the part of the brain believed to be causing seizures.  Potential surgical candidates are identified through an extensive pre-surgical evaluation, with the goal of localizing this region.  Electrical Source Imaging (ESI) is a non-invasive imaging technique proposed to complement current diagnostic tools, combining the computational analysis of Electroencephalogram (EEG) recordings and Magnetic Resonance Imaging (MRI) data.  Despite a growing body of research and the potential clinical value, there are few studies addressing the use of ESI within the pediatric population.  

Objective: To investigate the feasibility of Electrical Source Imaging (ESI) using low-density (LD) electrode coverage in assessing the ictal onset zone (IOZ) within children with medically refractory epilepsy.  Additionally, we aimed to compare ictal ESI findings to interictal LD-ESI, positron emission tomography (PET), and magnetoencephalography (MEG). 

Methods: This was a retrospective review of 20 patients from a district pediatric epilepsy center, between July 2014 - 2019.  ESI was conducted using the Curry 8 software from Compumedics Neuroscan, incorporating T1 Magnetic Resonance Imaging (MRI) scans and analysis of video Electroencephalogram (EEG) recordings.  Concordance was assessed using anatomical descriptions of resection margins and post-operative outcomes at 1 year as classified by the ILAE. 

Results: We found ictal ESI to correctly localize the epileptogenic zone in 5/7 patients with ESI localizations and focal resections, with all 5 being seizure free at 1 year.  Similarly, interictal ESI localized the epileptogenic zone in 5/6 patients with localizations and focal resections, with all 5 being seizure free at 1 year.  Additionally, we observed ictal ESI to be concordant to interictal ESI in 6/6 patients where both localizations were available.  Ictal ESI was concordant to 4/5 patients with MEG dipole clusters, while interictal ESI was concordant to 3/5 patients.

Significance: Our study is one of the first to report the feasibility of assessing the IOZ through LD-ESI within the pediatric population.  Additionally, we observe similar accuracy of ESI to other imaging techniques including MRI, MEG, and interictal ESI results.  These findings support the inclusion of LD-ESI within the pre-surgical evaluation of children and to supplement current diagnostic tools.

Keywords: Electrical Source Imaging, Ictal Onset Zone, Pediatric Epilepsy