Abstracts

Rationale: For epilepsy patients with malformation of cortical development (MCD), epileptiform activity may or may not be localized in proximity to the malformation. Such spatial relationship can have important influence in the surgical planning for intractable epilepsy patients with resectable seizure foci. Here we present two cases where the combination of Magnetoencephalograph (MEG) and Diffusion Tensor Imaging (DTI) contributes to the understanding of the relationship between the epileptogenic zone and the observed malformations. Methods: Data from two patients with MCD was reviewed. The first patient was a 10 year old male whose MRI revealed cortical dysplasia with open schizencephaly where the right frontal cortex was thickened (thickness of 9mm). There was a paucity of underlying subcortical white matter. The second patient was a 22 year old female with multiple periventricular nodular heterotopia (PNH) that showed up bilaterally. Her video EEG revealed the origin of seizures to be left hemispheric, broadly in the left temporo-parietal area. MEG-derived source estimates of interictal epileptiform activity were calculated as equivalent current dipoles (ECDs) and integrated onto a T2-weighted MRI image volume. Images were coregistered with the DTI b0 volume and visualized along with the DTI results using the DtiStudio software. This approach is recently developed in our lab and allows integrating MEG and DTI results into a common platform (paper submitted). Results: : For the first patient, DTI tractography showed a disrupted right corticospinal tract with some fiber tracts bending around his malformation both anteriorly and posteriorly. Clusters of MEG dipoles were localized inside and in the borders of the malformation overlapping with the bended corticospinal tract. In the second patient the MEG-derived dipoles were clustering in the left temporal area, far away from the lesions (PNH) in the same hemisphere. However, tractography (using the area defined by the dipoles as seed ROI) showed a tract connecting this area to distant lesions in the posterior horn of the left lateral ventricle (see Fig 1). In this case the integration of MEG and DTI provided an effective way to relate some of the structural malformations to the presence of distant epileptiform activity at the neocortical level. Conclusions: Combining MEG and DTI can help us better understand the relationship between the epileptogenic areas and the malformations for MCD patients.