Sutton's law in epilepsy: because that is where the lesion is.

Successful epilepsy surgery requires unambiguous identification of the epileptogenic zone. This determination may be a challenge when the pre-surgical evaluation yields conflicting data. We evaluated an adult patient with a right insular mass, but a seizure semiology, interictal EEG, and ictal EEG, suggesting left temporal lobe epilepsy. Resection of the mass, a ganglioglioma, resulted in seizure freedom and disappearance of interictal left temporal lobe epileptiform discharges. This case illustrates the principle that in localization-related epilepsy, the money is usually in the mass.