Abstracts

Presurgical evaluation in the management of brain tumor patients has been aimed at identifying eloquent areas of cortex as well as potential areas of epileptogenicity. Magnetic source imaging (MSI) provides a non-invasive assessment of somatosensory/motor function, language areas, as well as pathological waveforms. These include interictal spikes and sharp waves, and abnormal low frequency magnetic activity (ALFMA). Magnetoencephalography (MEG) provides the potential to map the abnormal tissue around the brain tumor to guide the boundaries of the resection margin. Five adult patients diagnosed with intra-axial brain tumors and epilepsy underwent presurgical evaluation at the 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 (4-D Neuroimaging Inc. CA.), between December 2004 to April 2005. Spontaneous cerebral activity was recorded with the standard international 10-20 system EEG. Magnetic sources were modeled as a single equivalent dipole. The dipoles were superimposed onto 3-D SPGR MR images. There were four females and one male, aged 27-53, in this group of patients. All patients presented with focal seizures (1 sensory/4 motor) with progression to complex partial seizures (CPS) with secondary generalization. All are maintained on AEDs (3 LEV, 1 PHT, 1 LEV/PHT). MEG demonstrated ALFMA in 3/5 patients. Their locations are at the peritumoral region within the area of edema. One patient was noted to have frequent spikes adjacent to the tumor. The size of the tumors varied from 2-cm to 6-cm in diameter. Histology was available in three patients, including two oligodendrogliomas (grade III) and one glioblastoma multiforme. Based on the limited number of patients in this initial study, we believe MEG localizes abnormal brain tissue that generates ALFMA as well as interictal discharges. This may guide surgical planning in the resection of brain tumor and the surrounding abnormal tissue. It is anticipated that additional patients[apos] data will be presented at AES.