Patterns of functional magnetic resonance imaging activation in association with structural lesions in the rolandic region: a classification system

Object. Functional magnetic resonance (fMR) imaging of the motor cortex is a potentially powerful tool in the preoperative planning of surgical proced ures in and around the rolandic region. Little is known about the patterns of fMR imaging activation associated with various pathological lesions in t hat region or their relation to motor skills before surgical intervention. Methods. Twenty-two control volunteers and 44 patients whose pathologies in cluded arteriovenous malformations (AVMs; 16 patients), congenital cortical abnormalities (11 patients), and tumors (17 patients) were studied using f MR imaging and a hand motor task paradigm. Activation maps were constructed for each participant, and changes in position or amplitude of the motor ac tivation on the lesion side were compared with the activation pattern obtai ned in the contralateral hemisphere. A classification scheme of plasticity (Grades 1-6) based on interhemispheric pixel asymmetry and displacement of activation was used to compare maps between patients, and relative to hand motor dexterity and/or weakness. There was 89.4% interobserver agreement on classification of patterns of fM R imaging activation. Displacement of activation by mass effect was more li kely with tumors. Cortical malformations offer a much higher functional reo rganization than AVMs or tumors. High-grade plasticity is recruited to comp ensate for severe motor impairment. Conclusions. Pattern modification of fMR imaging activation can be systemat ized in a classification of motor cortex plasticity. This classification ha s shown good correlation among grading, brain lesions, and motor skills. Th is proposal of a classification scheme, in addition to facilitating data co llection and processing from different institutions, is well suited for com paring risks associated with surgical intervention and patterns of function al recovery in relation to preoperative fMR imaging categorization. Such st udies are underway at the authors' institution.