Localization of partial epilepsy using magnetic and electric measurements

Abstract

Dipole methods applied to brain electric and magnetic fields have made several significant advances in investigation of epilepsy and sensorimotor cortex. The magnetoencephalogram (MEG) and the MEG-electroencephalogram (EEG) combination have contributed substantially. The MEG-EEG combination has shown a mean accuracy of somatosensory evoked response (SER) localization of the central fissure similar to electrocorticography (ECoG), resolution of ambiguity in ECoG of alternative configurations of hand sensorimotor cortex, and resolution of ambiguity of the causes of the difference between EEG and ECoG map patterns. MEG has shown simple dipolar maps of the temporal lobe interictal spike, localization estimates with about 6 mm error, and spatial separation of propagating multiple sources. MEG and EEG have shown a new neocortical propagation pathway in the temporal lobe, noninvasive estimates of the area of the spike focus, and complementary detection sensitivity. Application of spatiotemporal multiple dipole modeling in the simplest field using MEG has given a realistic quantification of spike zones. MEG and EEG have shown simple dipolar patterns for seizure origin, suggesting focality of some frontal seizures, and appears to increase EEG utility. Improved accuracy may result from a combined methodology including MEG and EEG. Dipole methods have potential utility as a noninvasive diagnostic procedure in epilepsy.