Abstracts

Presurgical evaluation in the management and treatment of patients with epilepsy has been aimed at identifying areas of epileptogenic potential. Magnetic Source Imaging (MSI) provides a noninvasive assessment of these pathological waveforms by identifying and localizing interictal spikes. Previously, this information was most accurately gained during the surgical phase through intracranial recordings with placement of SEA and/or intraoperative electrocorticography. This report will provide correlation of data in patients who have subsequently undergone both procedures during the course of their surgical treatment., 27 patients diagnosed with chronic epilepsy and/or brain tumor underwent presurgical evaluation with magnetoencephalography (MEG) at Minnesota Epilepsy Group, PA. Acquisition of MEG was performed at Minnesota Epilepsy Group, PA and United Hospital on a 148-channel Magnes 2500 WH System (4D-Neuroimaging Inc, San Diego, CA) between November 2004-April 2006. Spontaneous cerebral activity was recorded with the standard international 10-20 system EEG. Magnetic Sources were modeled as single equivalent dipoles. The dipoles were superimposed onto 3D-SPGR MR images. Subsequently surgical evaluation was performed at United Hospital and Children[apos]s Hospitals and Clinics Minnesota-St Paul, MN and included either SEA and/or intracranial electrocorticography to identify interictal activity and ictal onset., There were 15 females and 12 males aged 2 y.o. to 52 y.o. in this group of patients. 17 of 27 patients yielded fully concordant results between MSI and intracrainial recordings. In 7 cases there were limitations due to inability to provide intracranial sampling from all areas identified as interictally active on MSI. However, in these 7 cases, areas identified as interictally active by MSI were confirmed on intracrainial recordings and were included in areas of resection. In the remaining 3 patients intracranial recordings identified additional areas of interictal activity not demonstrated on MSI. It is noted in 2 of these patients this activity was only identified after significant reduction in antiepileptic drugs. The last patient was found to have frontal interictal activity on MSI; however, activity in the mesial temporal lobe had not been noted on MSI., MSI accurately identified areas of interictal activity. MSI information gained non-invasively during presurgical evaluation may lead to a reduction of invasive procedures, such as indwelling SEA, to identify areas of epiltogenesis.,