The relationship of magnetic source imaging to ictal electrocorticography in a neuronavigational workspace

Magnetic source imaging (MSI) registers magnetoencephalographic (MEG) activity to a three-dimensional MRI volume. State-of-the-art MSI allows concurrent whole head coverage, but is practically restricted to interictal recording. However, the purpose of the presurgical evaluation of epileptic patients, in which MSI is playing an increasing role, is the elucidation of the ictal epileptogenic focus. The manner in which interictal MSI activity relates to the ictal focus has not yet been adequately examined. To facilitate this analysis, we are developing techniques to precisely coregister MSI to the ictal onset zone as defined by extraoperative intracranial grid/strip monitoring. The neuronavigational workspace is a convenient area in which to precisely coregister these (and other) imaging and physiological data sets.