[Responsibility of the lateral geniculate nucleus in photosensitive epilepsy: dipole tracing method]

We studied the location of the electric generator of photoparoxysmal discharges using a scalp-skull-brain dipole tracing (DT) method. By this method, the location of epileptic discharges on each scalp EEG was calculated as an equivalent current dipole (ECD) in 8 cases of epilepsy who had photoparoxysmal discharges. We divided these cases into groups A and B (4 cases each), comprising of patients with and without visually-induced seizures, respectively. The ECDs of the 3 cases in group A corresponded to the small area adjacent to the lateral geniculate nucleus on MRI superimposed. On the other hand, the ECDs of all cases in group B located at the corpus callosum. This study suggests the pathways of epileptic discharges from the epileptic focus are different between two groups. It is supposed that neural activity of the lateral geniculate nucleus might be responsible for the generator mechanism of photoparoxysmal discharges which evokes photosensitive epilepsy.