MAGNETIC SOURCE LOCALIZATION AND MORPHOLOGICAL-CHANGES IN TEMPORAL-LOBE EPILEPSY - COMPARISON OF MEG EEG, ECOG AND VOLUMETRIC MRI IN PRESURGICAL EVALUATION OF OPERATED PATIENTS/

Is MEG source analysis able to precisely locate the primary focal epil eptic activity? 22 patients with pharmacoresistant temporal lobe epile psy were recorded during presurgical evaluation simultaneously with mu ltichannel MEG/EEG and invasive (subdural) electrodes to evaluate the increase of information gained by MEG concerning the localization of f ocal epileptic activity and lesions. With this systematic study it sho uld become clearer how often MEG can establish a diagnostic bridge bet ween function and morphology. In addition, MEG localization accuracy o f focal epileptic activity was to be validated empirically by invasive EEG recordings and postsurgical outcome. Spikes in the MEG were used for magnetic source localization, and the result was combined with mag netic resonance imaging (MRI). All patients definitly suffered from te mporal lobe epilepsy and revealed a structural abnormality in MRI. 17 patients with lesions in the temporal lobe were operated meanwhile and became markedly improved or seizure free. In 7 of 8 patients with a t umor and validated operation outcome, a very close correlation of the 3D-magnetic source localization and the border of the tumor in the bra in was found (distance less than 10 mm). In 8 of 9 patients with a tem poral/hippocampal atrophy and validated operation outcome, dipoles of epileptiform activity were located within the atrophic lobe. Therefore , it is concluded that magnetic source analysis provides 3D informatio n concerning spatial correlation of lesion and irritative zone in temp oral lobe epilepsy. This quantitative spatial relation may be very imp ortant for planning invasive recordings and selective surgical procedu res. For this purpose the quantification of focal epileptic activity i n extent and strength will be investigated additionally to the localiz ation. With the help of focus quantification the relation of localizat ion as well as distribution of trigger (PFA in the irritative zone) an d amplifier for seizure generation in the epileptogenic zone can be an alysed.