Noninvasive Presurgical Neuromagnetic Mapping of Somatosensory Cortex

Abstract

Rapid presurgical neuromagnetic localization of the somatosensory cortex was performed successfully on five patients with a large-array biomagnetometer by a protocol called magnetic source imaging (MSI). Determination of the location of the central sulcus is important in assessing operative risk and determining the optimal operative approach to structural lesions in the vicinity of the motor strip. The use of magnetic resonance imaging anatomical methods and intraoperative visual identification can be imprecise, whereas invasive localization prolongs operative time, adds cost, and entails added risk. Until the recent development of large-array biomagnetometer systems, neuromagnetic localization of the central sulcus had been demonstrated in research but was so time consuming and laborious as to preclude routine clinical use. In this study, the validity of MSI localizations was confirmed intraoperatively by direct cortical recording of somatosensory evoked potentials and/or direct motor stimulation. Complete agreement was found between MSI and intraoperative mapping in locating the central sulcus. Objective confirmations considered together with the speed and reliability of the procedure and with the presurgical availability of the results suggests the potential utility of MSI for routine surgical planning.

Source distribution of neuromagnetic slow wave activity in schizophrenic and depressive patients

“…Although the statistical significance is too limited to allow explicit conclusions, the few and selective si anificant o c0rrelation coefficients may be considered a clue to a p.otel~tial relationship between deviant information processmg III distinct cortical regions-as indicated by focal slow wave abnormality-and psychopathology-as indicated by symptom scores. Although EEG findin£s of au£mented slow wave activity in neuropathology (Walt~r, 1936: Lewine andOrrison, 1995) and localization of sources of n~uromagnetic -2 'When symptom scores were correlated with delta dipole density in all 10 areas, only two coefficientS were significant, the correlation ofleft-temporal delta actil'ity and the combined P. (Vieth et al, 2000;Gallen et al, 1992Gallen et al, , 1993 suggest to relate abnormal slow wave activity to dysfunctional tissue, it is currently not known what distin£uishes 'normal' slow wave activity from the one with d~'sfunc tional significance. We proposed that focal slo~wave accentuation indicates 'dysfunctional' brain regions also in psychiatric disorders.…”

“…generated in a circumscribed brain region often appear in the vicinity of a structural lesion like cerebral infarct, contusion, local infection, tumor, epileptic foci or subdural hematoma (Tanaka et al, 1998;De longh et aI., 2001De longh et aI., , 2002Vieth et al, 1996Vieth et al, , 1998Vieth et al, , 2000Maller et aI., 2002;Gallen et al, 1992Gallen et al, , 1993Fernandez-Bouzas et aI., 1999). Being explained by metabolic or blood flow changes consequent upon the structural lesion, focal slow waves have been 1.…”

Abnormal slow wave mapping (ASWAM)—A tool for the investigation of abnormal slow wave activity in the human brain

“…If the neural generators are focally concentrated, slow wave rhythms appear in the vicinity of a structural lesion, that is, focal electromagnetic slow waves are generated in the surround of circumscribed lesions or neuronal tissue otherwise affected by pathology such as cerebral infarct, contusion, local infection, tumor, epileptic foci and subdural hematoma de Jongh et al, 2001ade Jongh et al, ,b, 2002de Jongh et al, , 2003Gallen et al, 1992Gallen et al, , 1993Tanaka et al, 1998;Vieth et al, 1998Vieth et al, , 1996Vieth et al, , 2001Walter, 1936). Furthermore, reduced levels of neurotransmitters (e.g.…”

Intraoperative validation of functional magnetic resonance imaging and cortical reorganization patterns in patients with brain tumors involving the primary motor cortex

“…Because MR systems are more likely to be available in many institutions, a better understanding and validation of fMR imaging will be more easily performed by neurosurgeons who treat tumors located close to or within eloquent areas. Regardless of the enthusiasm arising from fMR imaging techniques in the preoperative evaluation, neurosurgeons have to be aware that: 1) fMR imaging is an indirect indicator of cerebral activation, because it measures changes in regional cerebral blood flow (rCBF) and not neuronal activity itself, such as is accomplished by magnetoencephalography; [2,15,24,31] 2) changes in blood oxygenation are characterized by a spatial and temporal dispersion that may cause errors in the accurate localization of activated areas (such as nonparenchymal deoxyhemoglobin changes in intraparenchymal capillaries or sulcal veins); [24,51] and 3) emerging functional imaging techniques or new applications of these have to be evaluated and validated objectively with gold-standard brain mapping techniques that are still considered safe and accurate to avoid neurological deficits or postoperative deterioration in patients undergoing removal of central lesions. …”