ABSTRACT

Brain lesions may influence their border zones anatomically and functionally. Magnetic source imaging (MSI) can give information on the function of these areas by localizing sources of evoked and spontaneous brain activity. The inherent multisource problem of MSI recordings can be handled by using spatial average techniques, the dipole density plot and the current density plot. In clinical routine the localizing of the somatosensory motor cortex, and speech-related cortical areas is used for image-guided neurosurgery with neuronavigators. In subjects and patients, MSI results have been compared with the results of the functional magnetic resonance imaging (MRI). In the presurgical evaluation of epileptic patients the source localization of the spontaneous slow-wave activity can be an additional valuable tool by localizing the penumbra of the epileptogenic lesion, especially when the lesion is not visible in the MRI. In patients with multiple sclerosis it could be demonstrated that white matter lesions cause abnormal activity in adjacent neuronal areas. The penumbra associated with infarcts and transient ischemic attacks also can be localized. This was supported by comparisons of MSI results and those of the proton magnetic resonance spectroscopic imaging (1H MRSI) of N-acetyl and lactate in patients with brain infarcts and tumors.