When fMRI and neurosurgery go hand in hand: a case study on presurgical mapping of complex motor functions for supramarginal glioblastoma resection

Introduction The application of functional magnetic resonance imaging (fMRI) as a tool for the presurgical mapping of brain tumors has been often limited to language and motor domains. Here, we present the case of a 52-year-old right-handed woman diagnosed with a glioblastoma in the left inferior parietal lobule, extending from the supramarginal gyrus to the underlying white matter. A presurgical fMRI exam was used to target perilesional areas involved in praxis functions. Material/Methods Before surgery, the patient underwent a neuropsychological assessment including language, praxis, and executive functions. Three tasks were performed under fMRI (3T) to map cognitive and motor functions: 1) visual sentence completion; 2) right finger tapping; 3) manipulation, identification, and imaginary usage of objects. Tractotron as part of the BCB Toolkit (http://www. brainconnectivitybehaviour.eu/) was used to identify the tracts presumably affected by the lesion. Results The neuropsychological assessment revealed executive dysfunctions, mainly in inhibitory control, which impaired language performance; no praxis disorders emerged. The fMRI exam showed that the sentence completion task activated predominantly left visual, frontal, and temporal areas, including the frontal operculum, the posterior superior temporal gyrus, and the angular gyrus, but only a slight overlay with the tumor. Activations in both tasks 2-3 were detected in the central and post-central sulcus, extending toward the anterior and the medial borders of the lesion in the complex praxis task. The tracts that most likely (probability > 0.5) were disconnected were the superior longitudinal fasciculus (SLF) II (0.99) and III (1.00), the hand superior U tract (0.92), the arcuate anterior (0.86), and posterior (0.84) segment, and the corpus callosum (0.80). The patient underwent a left parietal craniotomy surgical procedure. Debulking and gross total resection of the tumor were performed aided by neuronavigation, microsurgery, ultrasound aspirator, and neurophysiological monitoring. Conclusion The outcomes of the resection mirrored the evidence of the presurgical mapping performed with fMRI: the patient did not show motor dysfunctions nor aphasia, although there was a high probability of disconnection of the arcuate fasciculus. On the contrary, mild apraxia and grasping deficits emerged, compatible with the involvement of perilesional areas in the complex motor task and the presumable disconnection of the SLFII, the SLFIII, and the hand superior tract. The present study stresses the effectiveness of fMRI as a tool for the presurgical mapping of complex cognitive functions such as higher-order motor abilities.