Abstracts

Magnetoencephalography (MEG)/magnetic source imaging (MSI) is the only neuroimaging method to real-time measure neuronal activity non-invasively. MSI clinical application is receiving more attention. Presurgical functional brain mapping with MSI allows guidance during surgical decision-making and decreases the invasiveness of presurgical evaluation in epilepsy, brain tumor or cerebral vascular diseases. This report describes the patients tested and confirmed by invasive brain monitoring intraoperatively or with subdural grid placement, in the MSI Lab of Minnesota Epilepsy Group, PA and United Hospital at Saint Paul, Minnesota., Twenty-nine patients experienced both functional brain mapping with MSI (148-channel Magnes 2500 WH System, 4-D Neuroimaging, San Diego, CA) and invasive brain mapping (11 patients with intra-operative mapping, 18 with subdural electrode placement) in Minnesota Epilepsy Group between Dec 2004 and June 2006. Standard MSI protocols were applied for localization of language (word recognition task for receptive language mapping), somatosensory (pneumatic piston as stimuli), and primary motor cortex (voluntary finger tapping). The magnetic sources are modeled as a single equivalent dipole. The dipoles were superimposed onto the 3-dimensional SPGR MR images (1.4 mm slice thickness, no gap)., In the 29 patients, there were 8 patients with language mapping, 26 with motor mapping and 16 with somatosensory mapping. In the 51 brain function components, somtosensory and motor MSI dipoles were overlapped with the locations of invasive cortical mapping or located within 1 cm range from the sites of invasive cortical mapping; language MSI dipoles were located in the sulcus overlapped by cortical mapping on surface. There were no non-predicted neurological deficits after resective surgery in 28 patients. One patient did not experience resection due to the overlapping of motor cortex and epileptogenic focus., Functional brain mapping with MSI is an accurate tool to localize brain function for surgical planning. Using MSI information properly may reduce the number of invasive brain mapping procedures.,