Objective: To demonstrate whether cortical activation within different cortical motor regions in neurosurgical patients varies with the degree of paresis induced by mass lesions near the central region.
Methods: A total of 110 patients with brain tumors infiltrating the central region and with varying degrees of paresis were investigated employing fMRI during the performance of hand motor tasks. The percent signal change between rest and activation was calculated for four cortical regions: primary motor cortex (M1), supplementary motor area, premotor area, and superior parietal lobule.
Results: Significant decreases in activation with increasing degrees of paresis were found in M1, whereas significant increases in activation were noted in secondary motor areas that were not affected by the tumor.
Conclusions: The signal loss in areas adjacent to tumor tissue may relate either to tumor-induced changes in cerebral hemodynamics or to a direct loss of cortical neurons resulting in a lesser degree of hemodynamic changes after motor activation. The increase in activation within secondary motor areas with increasing degrees of paresis supports the growing evidence of a practice- and lesion-dependent reorganization of the cortical motor system and the ability of the brain to modulate its excitatory output according to external demands.