Preoperative functional magnetic resonance tomography (fMRI) in patients with rolandic brain tumors: indication, investigation strategy, possibilities and limitations of clinical application

Preoperative functional magnetic resonance imaging (fMRI) localizes the primary motor and somatosensory cortex in relation to rolandic brain tumors and determines plastic cortical reorganization. Functional landmarks help to assess the indication for surgery and to plan for safer surgical procedures that protect the functional cortex during resection even when morphologic landmarks are no longer identifiable on anatomic images. Despite its successful application, preoperative fMRI has not yet reached the status of an established clinical diagnostic procedure since special stimulation systems, standardized fMRI protocols and medically approved software are still lacking. Following a brief review of the image display of the functional and morphologic anatomy, the different indications for preoperative fMRI in patients with rolandic brain tumors are presented. A robust preoperative protocol enables clinical MR units with magnetic field strengths of 1.0 Tesla or higher to perform reliable fMRI during contralateral hand movements. Optimized investigation strategies and stimulation modalities are proposed for patients with rolandic tumors distant from the cortical hand representation, for patients with preexisting sensorimotor deficits and for patients with poor compliance. Representative cases illustrate the clinical application. Possibilities and limitations of preoperative fMRI are presented and discussed. (orig.)