Objective: To evaluate the capabilities and the limitations of motor functional magnetic resonance imaging (fMRI) in the presurgical evaluation of the cerebral tumors located in or near the motor homunculus. To correlate each type of activation with the histologic characteristics of each tumor.
Materials and methods: fMRI was performed in 17 patients (14 adults and 3 children), without any motor deficit, presenting with various intracerebral tumors. Three fMRI activation paradigms were used: contralateral to the lesion: ballistic opposition of the fingers, flexion-extension of the foot and click of the tongue. Four patients, without motor deficit, with cerebral tumors far from the motor homunculus were used as control group to look for nonspecific activations. In all cases, the histopathology of the tumor was known accurately.
Results: In 11 patients with infiltrating tumors, the activated areas were clearly displaced. They were often intratumoral and scattered in correlation with the degree of infiltration. Two patients with noninfiltrating tumors (meningioma) showed extratumoral shift of the activated areas. Four patients presenting cerebral tumors far from the homunculus motor did not show intratumoral activation. The supplementary motor area and the ipsilateral primary motor cortex were also reproducibly activated during the motor tasks. The task of the tongue was often artifacted, probably because of the head motion.
Conclusions: These preliminary results suggest that the histopathologic characteristics of a tumor, and especially its microscopic structure, play a role in the organization of the motor functional area. In a small number of cases, fMRI could be used intraoperatively with a neuronavigation system.