[Presurgical evaluation of cerebral tumors with functional MRI]

To evaluate the capabilities and the limitations of motor functional magnetic resonance imaging (FMRI) in the presurgical planning of the cerebral tumors located in or near the motor homunculus and to correlate each type of activation with the histologic characteristics of each tumor.

FMRI was performed in 17 patients (14 adults and 3 children), without motor deficit, presenting with various intra cerebral tumors. Three FMRI activation paradigms were used, controlateral 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 non specific activations. In all cases, the histopathology of the tumor was known accurately.

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 non infiltrating 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 sometimes activated during the motor tasks. The task of the tongue was often artifacted, probably because of the head motion.

These preliminary results suggest that the histopathologic characteristics of a tumor and especially its microscopic structure plays a role, with others factors, on the motor functional area organization. In a small number of cases, the data obtained from the FMRI could be used intraoperatively, with a neuronavigation system.