Ictal dipole source analysis based on a realistic scalp-skull-brain head model in localizing the epileptogenic zone

The objective of this study is to examine whether dipole modeling based on a realistic scalp-skull-brain head model (SSB/DT) is useful to localize the epileptogenic zone. Eight patients with surgically treated temporal lobe epilepsy were studied. Dipole locations and vector moments of ictal epileptiform activities were calculated by inverse solution methods. Accuracy of dipole locations were assessed by comparing with intracranial EEG. The patterns of ictal epileptiform activities were correlated with the dipole location and vector moment. Dipole locations of the peaks of ictal epileptiform activities estimated by SSB/DT showed good agreement with the epileptogenic foci determined by intracranial EEG. SSB/DT was able to discriminate between medial and lateral temporal epileptogenic foci. Two distinctive types of dipole vector moments, vertical and horizontal were noted. Vertical dipole vector moments corresponded to the medial temporal dipole source and horizontal dipole vector moments were corresponded to the lateral temporal dipole source. Useful clues to differentiate between medial and lateral temporal lobe epilepsy by the visual inspection of scalp EEG were found. SSB/DT is useful tool in the presurgical evaluation of patients with intractable epilepsy.