Focal epilepsy is associated with widespread alterations in structural brain connectivity, often present at the disease onset and related to learning disabilities. Whether ongoing seizure activity contributes to network pathology is a matter of debate. This study intends to measure the impact of seizures on structural connectivity on a local and on a global level. In children examined with intracerebral electrodes to evaluate whether a surgical cure can be proposed, we combine intracerebral stereotactic electroencephalography (EEG) recordings with diffusion weighted imaging of white matter fibers. On the local level, the study will quantify the number of deficient connections in the seizure onset zone. On a global level, the study will compare the white matter fibers of the left and right hemisphere to probe whether physiological language lateralization is preserved.