Technical refinements for validating functional MRI-based neuronavigation data by electrical stimulation during cortical language mapping

Preoperative functional neuroimaging techniques represent an appealing method to localize language areas in tumor surgery, but their reliability still needs to be confirmed by accurate comparison with more invasive but validated mapping techniques like intraoperative electrical cortical stimulation. Two patients harboring a glioma involving speech areas underwent mapping of language function by preoperative functional magnetic resonance imaging (fMRI), whose results were integrated into the neuronavigation device, and by intraoperative electrical stimulation mapping (ESM). The utilization of neuronavigation allowed us to estimate the degree of spatial correspondence between language areas detected by the two techniques. Language areas identified by functional magnetic resonance imaging on the cerebral cortex exposed during surgery corresponded to those identified by invasive mapping in both patients. It was possible to achieve a gross total tumor removal while respecting language areas in both cases, with no permanent postoperative phasic aggravation. The concordance of results between pre- and intra-operative mapping techniques in our patients indicates that preoperative fMRI language mapping may prove useful when planning the resection of intracerebral lesions in language areas. However, accurate neurofunctional imaging protocols and image analysis are crucial to obtain a preoperative language mapping that is in agreement with ESM findings.