Magnetoencephalography-guided epilepsy surgery for children with intractable focal epilepsy: SickKids experience.

We introduced magnetoencephalography (MEG)-guided epilepsy surgery for children with intractable focal epilepsy at The Hospital for Sick Children (SickKids) in Toronto, Canada. Surgical candidacy and decisions on surgical procedure for children with intractable focal epilepsy are based on long-term scalp video EEG (VEEG) results, magnetic resonance imaging (MRI) findings, and the distribution of MEG spike sources. After multidisciplinary discussion at the seizure conference, for the patients requiring intracranial VEEG, custom-made subdural electrode grids are designed using three-dimensional MRI superimposed with MEG spike sources to cover the area of clustered MEG spike sources. At the first surgery, neurosurgeons use the intraoperative neuronavigation system to visualize the area of clustered spike dipoles and somatosensory evoked fields on MEG to place the subdural grid and depth electrodes. At the second surgery, the area of seizure onset and active interictal spike discharges on the intracranial VEEG recording, which usually correlates with the zone of clustered MEG spike sources, is resected. This combination leads to successful surgical outcome to control seizures in these challenging paediatric patients. MEG is a useful tool in children with intractable focal epilepsy to determine the surgical candidacy and focal cortical resection to stop seizures.