Interictal ECoG spikes as reflected in MEG

This study investigates the relationship between the sources of MEG interictal spikes and the distribution of spikes in invasive ECoG in a group of 38 epilepsy patients. An amplitude/surface area measure is defined to quantify ECoG spikes. It is found that all MEG spikes are associated with an ECoG spike that is, according to this measure, among the largest in each patient. For different brain regions considered the inter-hemispheric, tempero-lateral and central regions stand out. However, MEG may only see part of the often complex ECoG spike. In an accompanying simulation study it is shown that MEG as predicted from measured complex ECoG spikes resemble measured MEG and show similar shortcomings with respect to localization.