Display of the epileptogenic zone on the frontal cortical surface using dynamic voltage topography of ictal electrocorticographic discharges.

To evaluate the usefulness of computerized brain-surface dynamic voltage topography (DVT) of ictal electrocorticographic (ECoG) discharges to localize and identify epileptogenic areas, 3 patients with intractable frontal lobe epilepsy who underwent epilepsy surgery after chronic subdural electrode recording were assessed. Cortical surfaces and subdural electrodes were photographed during initial surgery to create an electrode map that could be superimposed onto a picture of the brain surface. DVT was performed by calculating sequential amplitudes of ictal ECoG discharges, which were then superimposed onto the cortical and electrode maps. In all cases, DVT clearly identified the ictal onset zone and the early propagation area on the operative field. DVT allowed recognition of spatial relationships between the epileptogenic area and structural abnormalities, functional cortex, and cortical veins; and was useful to decide on the resection area.