Source localization in refractory partial epilepsy

In this paper, 51 patients with refractory complex partial seizures (CPS) a nd intracranial structural abnormalities demonstrated with optimum MR (spac e-occupying: n=16; atrophic: n=32; dysplastic: n=3) were studied. Video-EEG monitoring showed CPS in all patients. In 13 patients, additional intracra nial EEG monitoring demonstrated hippocampal seizure onset in 12 and medial occipital ictal onset in 1 patient. Interictal and ictal dipole modeling u sing a spherical head model and realistic electrode coordinates were perfor med Spatiotemporal dipole mapping of interictal epileptic discharges reveal ed two distinct dipole patterns. Patients with lesions located in the media l temporal lobe (n=41) and medial occipital lobe (n=2) uniformly presented a dipole with an elevation of more than 15 degrees relative to the axial pl ane. Eight out of ten patients with extratemporal lesions and 1 patient wit h a pure neocortical temporal lesion had a less stable dipole with an eleva tion less than 15 degrees relative to the axial plane. Dipole modeling of e pochs of early ictal discharges revealed a striking correspondence with the interictal findings in individual patients. Ictal dipole modeling identifi ed the ictal onset zone correctly when compared with intracranial EEG recor dings from bilateral hippocampal depth electrodes in patients with medial t emporal seizure onset. Mapping of dipoles on MR images of individual patien ts facilitated clinical interpretation of the EEG data. Interictal and icta l dipole mapping provided additional and clinically relevant information an d may obviate the need for intracranial EEG studies in some surgical candid ates for refractory CPS.