Abstracts

To define the role of Magnetoencephalography (MEG) in epilepsy surgery planning and predicting outcomes in children with medically intractable epilepsy. We retrospectively studied 17 children with medically intractable epilepsy due to cortical malformation (1), cortical dysplasia (7), tumor (3), trauma (2), post cerebral infarcts (1), and dual pathology (cortical dysplasia with mesial temporal sclerosis, 3) who underwent MEG before epilepsy surgery. We compared interictal MEG spike source characteristics, magnetic resonance imaging (MRI), ictal SPECT (if available), PET (if available), pathological findings and their long term surgical outcomes. MEG spike sources were found in proximity to the epileptogenic lesion in all patients. Most of them (15 of 17) have excellent long term outcomes (1-yr Engel I-12 patients, II- 3 patients). The remaining two, one has focal cortical dysplasia in the eloquent cortices which cannot be completely removed and underwent multiple subpia transection (MST) and remains class IV, the other has diffuse cortical dysplasia type IA and achieve class III outcome after large frontal lobectomy. Five patients are non-lesional extratemporal epilepsy without definitive localization from other investigations except MEG findings. MEG spike sources correlated with electrocorticograhic findings in all patients who underwent subdural grid evaluation before resections MEG is a very useful, non invasive diagnostic tool and not a redundant test. It can be very useful especially in non-lesional extratemporal epilepsy without any definitive localization from other noninvasive modality of investigations. It complements the conventional invasive EEG to better define the epileptogenic zone without increasing morbidity.