Localization of interictal delta and epileptiform EEG activity associated with focal epileptogenic brain lesions

The present study was aimed at investigating the accuracy of electric sourc e reconstruction in the presurgical evaluation of epilepsy patients. Sponta neous EEG activity of 14 patients with focal intracerebral epileptogenic le sions was analyzed by source reconstruction based on high-resolution EEG (6 4-channel system) and a boundary element method head model accounting for t he individual head anatomy. Equivalent dipole modeling was applied to focal delta and interictal epileptiform activity. The localization re suits were validated quantitatively by comparison with the sites of the structural le sions. In 6 of 9 patients with focal delta activity, the maximum of dipole concentration was closer than 10 mm to the nearest lesion margin and mostly at the border or within pathologically altered cortical tissue. In all 11 patients showing interictal epileptiform activity, the localization results were found in the same lobe as the lesion. In almost half of them, they we re closer than 10 mm to the lesion margin. Patients with larger distances ( 22-36 mm) mostly had hippocampal atrophy or sclerosis. Their dipole locatio ns did not appear in the affected hippocampus, but in the adjacent temporal neocortex. In conclusion, electric source reconstruction applied to both a bnormal slow and interictal epileptiform EEG activity seems to be a valuabl e additional noninvasive component in the multimodal presurgical evaluation of epilepsy patients. (C) 2001 Academic Press.