Plasticity of the human motor cortex in patients with arteriovenous malformations: a functional MR imaging study

The capacity of the human brain to recover from damage has been explained on the basis of plasticity, according to which remaining areas assume functions that would normally have been performed by the damaged brain. Patients with cerebral arteriovenous malformations (AVMs) involving primary motor areas may present without significant neurologic deficits. We used functional MR imaging to investigate the organization of cortical motor areas in patients with AVMs.

Cortical motor hand and foot representations were mapped in nine right-handed patients harboring AVMs occupying the hand (n = 6) or foot (n = 3) region of the primary motor cortex (M1). None of the patients exhibited motor deficits. Simple movements of the hand and foot were performed. In eight patients, both right and left extremities were tested; in one patient, only the hand contralateral to the AVM was examined. Localization of activation in the affected hemisphere was compared with that in the unaffected hemisphere and evaluated with respect to the normal M1 somatotopic organization shown in earlier functional MR imaging investigations.

Cortical activation showed three patterns: 1) functional displacement within the affected M1 independent of the structural distortion induced by the AVM (n = 4), 2) presence of activation within the unaffected M1 ipsilateral to the moving extremity without activation in the affected M1 (n = 3), and 3) prominent activation in nonprimary motor areas without activation in either the affected or unaffected M1 (n = 2).

Preliminary evidence suggests that brain AVMs lead to reorganization within the somatotopic representation in M1 and to occasional abnormal expansion into nonprimary motor areas.