Functional MRI and intraoperative brain mapping to evaluate brain plasticity in patients with brain tumours and hemiparesis

Objective-To support the hypothesis about the potential compensatory role o f ipsilateral corticofugal pathways when the contralateral pathways are imp aired by brain tumours. Methods-Retrospective analysis was carried out on the results of functional MRI (fMRl) of a selected group of five paretic patients with Rolandic brai n tumours who exhibited an abnormally high ipsilateral/ contralateral ratio of activation-that is, movements of the paretic hand activated predominate ly the ipsilateral cortex. Brain activation was achieved with a flexion ext ension of the fingers. Statistical parametric activation was obtained using a t test and a threshold of p<0.001. These patients, candidates for tumour resection, also underwent cortical intraoperative stimulation that was cor related to the fMRI spatial data using three dimensional reconstructions of the brain. Three patients also had postoperative control fMRI. Results-The absence of fMRI activation of the primary sensorimotor cortex n ormally innervating the paretic hand for the threshold chosen, was correlat ed with completely negative cortical responses of the cortical hand area du ring the operation. The preoperative fMRI activation of these patients pred ominantly found in the ipsilateral frontal and primary sensorimotor cortice s could be related to the residual ipsilateral hand function. Postoperative ly, the fMRI activation returned to more classic patterns of activation, re flecting the consequences of therapy. Conclusion-In paretic patients with brain tumours, ipsilateral control coul d be implicated in the residual hand function, when the normal primary path ways are impaired. The possibility that functional tissue still remains in the peritumorous sensorimotor cortex even when the preoperative fMRI and th e cortical intraoperative stimulations are negative, should be taken into a ccount when planning the tumour resection and during the operation.