To compare the use of EEG and neuroimaging to predict the epileptogenic foci in patients with favorable surgical outcomes.

Patients with refractory epilepsy typically undergo an extensive evaluation for presurgical workup, including surface and invasive EEG (iEEG), MRI, PET, and ictal and interictal SPECT, and neuropsychological testing.

Pediatric epilepsy surgery patients at Columbia University who were Engel class 1 or 2 at the 1-year follow-up were identified retrospectively. The ictal onset zone was localized using EEG and various diagnostic imaging modalities and were compared to the location of the resected epileptogenic cortex. Studies were defined as precisely localizing when they matched the resection area.

36 epilepsy surgery patients were included in this study. Pathology was available in 33 patients and showed 39% cortical dysplasia, 11% mesial sclerosis, 33% reactive inflammation or gliosis, and 6% tumor.

Ictal onset was precisely localized in 44% patients by surface EEG, and 76% by iEEG. The region containing the epileptogenic cortex was identified in 63% of patients by surface EEG, and 100% by iEEG. For neuroimaging, the epileptogenic foci were precisely localized in 30% of patients (MRI 31%, PET 33%, SPECT 38%). The region containing the epileptogenic cortex was identified in 50% of patients by MRI, 70% by PET, and 69% by SPECT. Brain MRI had the least localizing value with the most nonlocalizing studies (34%) followed by PET (15%), surface EEG (9%) and SPECT (6%).

In pediatric epilepsy, cortical malformation is the leading cause for epilepsy surgery and requires comprehensive evaluation. Each mode of evaluation may bring additional information for localization of epileptogenic cortex. SPECT and PET imaging contributes the localization in at least 20% of patients who may have normal anatomical imaging. This study highlights the value of PET and SPECT imaging in the presurgical workup in pediatric age group.