Abstracts

Rationale: The lateral and medial aspect of the central and frontal cortex were studied by electrical stimulation in epilepsy surgery candidates in order to determine the topography and somatotopic distribution of areas harboring negative motor areas (NMA). NMA were defined as cortex whose electrical stimulation elicits inability to maintain or initiate voluntary movements. Methods: Results of electrical stimulation of the cortex were evaluated in a total of 120 patients in whom invasive electrodes were implanted for planning resective epilepsy surgery at the University of Munich Epilepsy Center. Exact localization of the placement of the subdural electrodes was defined by fusion of 3-dimensional reconstructed MRI and CT images in 12 patients and by analysis of plane skull X-rays in another 7 patients. Results: We obtained negative motor responses in a total of 129 electrodes covering the primary somatomotor and supplementary sensorimotor areas in 19 patients. Bilateral negative motor responses were more often elicited when stimulating the mesial frontal cortex whereas contralateral negative motor responses were more often elicited when stimulating the lateral central cortex (p<0.001, Chi2-Test). Bilateral negative motor responses elicited from the lateral cortex localized predominantly to the gyrus frontalis medius, contralateral negative motor responses to the precentral gyrus (p<0.05, Chi2-Test). Conclusions: Exact localization using 3-D fusion methods reveals negative motor areas widely distributed throughout the precentral gyrus and the mesial fronto-central cortex. Negative motor areas represent most likely areas involved in motor planning and show a somatotopic organization. The lateral NMA serves more contralateral motor planning whereas the mesial NMA bilateral movements.