Normal and abnormal MEG activity in border zones of brain

Background. Brain lesions may influence their border zones by moving, compressing, infiltration, edema or by a mixture of all the above. Sources of evoked and spontaneous activity in border zones can be localized by the MEG. Methods. The inherent multisource problem can be handled by using spatial average techniques (Dipole-Density-Plot (DDP) and Current-Density-Plot (CDP)). The reliability was tested with structural lesions (tumors and infarctions). Results and Conclusions. The localizing of the somatosensory, the motor, and the auditory cortex and the speech related areas in relation to adjacent tumors, is used in clinical routine. The results will be fused into the neuronavigator for image guided neurosurgery. In the presurgical evaluation of epileptic patients the localization of the epileptogenic lesion is an additional valuable finding, especially when the lesion is not visible in the MRI. In the field of cerebrovascular accidents the penumbra can be localized in infarctions and TIAs. The feasibility to localize the penumbra by the MEG was demonstrated by our comparison of MEG results and those of the proton magnetic resonance spectroscopic imaging (H MRSI).