Abstracts

The accurate identification of the epileptogenic lesion is a critical step in the presurgical evaluation of patients with tuberous sclerosis complex (TSC). Previous studies have indicated that agreement between ictal and interictal vEEG recordings, invasive recordings and MRI findings are associated with good postsurgical outcome. The purpose of our study was: first, to evaluate the individual and combined contribution of different modalities (EEG, MRI, invasive vEEG and MEG) to the identification of the epileptogenic tuber and; second, to test the contribution of MEG in those cases of initial disagreement between radiological and neurophysiological findings., In this retrospective study we studied 23 patients with TSC, and refractory epilepsy, who underwent brain surgery. In all the 23 cases surface EEG and MRI were available, with invasive vEEG and MEG data only available in 14 cases. The accuracy of each modality in the localization of the epileptogenic tubers was evaluated after reviewing the effects of surgery on seizure control., Taking into account the predictions based on the four independent procedures and the real surgical outcomes, the correct identification of the epileptogenic tuber was achieved in a similar proportion of cases by the four individual modalities (between 36% and 43%). Surface EEG was responsible of the highest percentage of incorrect predictions (39%) while MEG was only incorrect in 21% of the cases. In none of the 5 cases showing a complete agreement between the invasive vEEG and MEG estimates surgery produced unexpected outcomes. In all 4 cases of negative outcome where MEG data was available, the overlap between the ressected area and the MEG-derived epileptogenic zone was either partial (3 cases) or inexistent (1 case)., MEG should be considered always when standard radiological and neurophysiological findings do not lead to a complete agreement in the presurgical identification of the epileptogenic tuber.[table1],