Comparison of functional brain mapping by computer controled roboterized transcranial-magnet-stimulation and functional MRI

The knowledge of the exact localization of motor cortical areas can be crucial for neurosurgical therapy planning in patients suffering from processes near the central region. For the time beeing functional magnet resonance imaging (f-MRI, so called BOLD-sequences) can be regarded as the gold-standard for non-invasive localization of the functional areas of the brain. Yet in some cases this technique might be insufficient. We here present a novel technique designed for this task: The image-guided computer controled roboterized transcranial-magnet-stimulation (R-TMS). For R-TMS a roboter-arm moves a transcranial magnet-stimulation coil over the patients head. The movements follow a grid placed on a virtuall (MRI-)image of the central region. At each point of the grid a number of stimulating impulses is given and the resulting motor-response is recorded by electromyography of the concerned muscles (in our study M. Brachioradialis, thenar and hypothenar). The resulting data is projected on a surface map of the brain. A healthy probande and 6 consecutive patients suffering form tumors in or near the central region were examined by R-TMS and f-MRI (finger-tapping). The resulting Data of both techniques were compared. R-TMS examinations were feasible and provided high resolution functional maps of the central region. The data corresponded to the classical anatomical landmarks (hand notch and central gyrus). It also matched the results from the f-MRIs closely. In contrast to the f-MRI the motor-areas of single muscles or muscle groups could be clearly located and delineated from one another by R-TMS. R-TMS is a feasible method for functional imaging of the motor cortex. The resolution allows the identification of motor areas of individual muscle groups and is in so far superior to the conventional f-MRI. It might help neurosurgical and interventional therapy planning in patients suffering from processes in or near the central region of the cortex.