Plasticity of the motor cortex in patients with brain tumors and arteriovenous malformations: a functional MR study

Test the hypothesis about the potential role of functional MRI (fMRI) to evaluate the plasticity of the cortical motor areas in patients with brains tumors and brain arteriovenous malformations (AVMs) and measurement of the lesion-to-fMRI activation distance for predicting risk of new motor deficit after surgery.

This was a retrospective study. The present study population enrolled eight patients with motor cortex lesions. Cortical motor representations were mapped in these patients harboring tumor or AVMs occupying the region of primary motor cortex (M1). Five patients had known diagnosis of primary brain tumor including glioblastoma multiforme, (n = 1), diffuse astrocytoma (n = 2), dysembryoplastic neuroepithelial tumor (DNET) (n = 1) and unknown pathology (n = 1). Three patients had known diagnosis of brain AVMs. Three patients showed hemiparesis at the time of presentation. Focal/generalized seizure or headache was present in the remaining patients. Simple movements of both hands were performed Localization of the activation in the affected hemisphere was compared with that in the unaffected hemisphere and evaluated with respect to the normal M1 somatotopic organization. Distance between the location of the fMRI activation (M1) and margin of the lesion was recorded.

Cortical activation was found in two patterns: 1) functional displacement within affected M1 independent of the structural distortion induced by the tumor or AVMs (n = 7) and 2) presence of activation within the non-primary motor cortex without activation in the affected or unaffected M1 (n = 1).

Brain tumor or AVMs led to reorganization within the somatotopic affected M1 and can expand into non-primary motor cortex area. Distortion of the anatomy alone by the space-taking lesion did not influence the location of the reorganized cortex. No particular type of reorganization pattern could be predicted fMRI could be localized reorganized cortex and was found to be a useful tool to assess the lesion-to-activation distance for predicting risk of new motor deficit after surgery. The present study thus emphasizes the importance of considering additional fMRI with structural MRI to evaluate individual differences in cortical plasticity for treatment planning, particularly in the neurosurgical procedure.