Figure 2.

MEG modelling of epileptic spikes and SEEG localization of the seizure-onset zone in a patient with a lateralized spiking volume (Patient 13). Top left: Example of one prototypical spike recorded with MEG for one single channel of Patient 13. Top right: Topographic map of the magnetic field recorded for all MEG channels at the main peak of the prototypical spike. Bottom left: The MEG spiking volume determined with VIES (red volume) is shown on representative MRI slices. On the same slices, the SEEG electrodes showing clear signal changes at seizure-onset are shown in blue, and electrodes without clear ictal activity are in white. Bottom right: SEEG implantation scheme of Patient 13. The location of the penetrating points of intracranial electrodes is determined by co-registering the patient’s post-implantation MRI onto the cortical mesh extracted from the MRI. The MEG spiking volume projected onto the cortical surface is shown as a red area. SEEG electrodes showing clear signal changes at seizure-onset are shown in green and electrodes without ictal changes are shown in black. Notice that the spiking volume is lateralized but not focal and only partly co-extensive with the seizure-onset zone determined with SEEG (several lobes are included in the MEG spiking volume). Surgery was contraindicated for Patient 13 as the seizure-onset zone was considered as non-localized based on SEEG.