Abstract
Introduction: Pre-surgical mapping is clinically essential in the surgical management of brain tumors to preserve functions. A common technique to localize eloquent areas is functional magnetic resonance imaging (fMRI). In tumors involving the peri-rolandic regions, the finger tapping task (FTT) is typically administered to delineate the functional activation of hand-knob area. However, its selectivity may be limited. Thus, here, a novel cue-induced fMRI task was tested, the visual-triggered finger movement task (VFMT), aimed at eliciting a more accurate functional cortical mapping of the hand region as compared with FTT.Method: Twenty patients with glioma in the peri-rolandic regions underwent pre-operative mapping performing both FTT and VFMT. The fMRI data were analyzed for surgical procedures. When the craniotomy allowed to expose the motor cortex, the correspondence with intraoperative direct electrical stimulation (DES) was evaluated through sensitivity and specificity (mean sites = 11) calculated as percentage of true-positive and true-negative rates, respectively.Results: Both at group level and at single-subject level, differences among the tasks emerged in the functional representation of the hand-knob. Compared with FTT, VFMT showed a well-localized activation within the hand motor area and a less widespread activation in associative regions. Intraoperative DES confirmed the greater specificity (97%) and sensitivity (100%) of the VFMT in determining motor eloquent areas.Conclusion: The study provides a novel, external-triggered fMRI task for pre-surgical motor mapping. Compared with the traditional FTT, the new VFMT may have potential implications in clinical fMRI and surgical management due to its focal identification of the hand-knob region and good correspondence to intraoperative DES.
Highlights
Pre-surgical mapping is clinically essential in the surgical management of brain tumors to preserve functions
In the light of these considerations, we developed a new task for pre-surgical motor mapping, the visual-triggered finger movement task (VFMT), with the aim of overcoming the weakness of finger tapping task (FTT)
FTT revealed a widespread network of activation involving areas not closely related to motor processing, whereas VFMT was able to elicit a more focal cluster of activation in M1 and other motor regions (i.e., SMA)
Summary
Pre-surgical mapping is clinically essential in the surgical management of brain tumors to preserve functions. In tumors involving the peri-rolandic regions, the finger tapping task (FTT) is typically administered to delineate the functional activation of hand-knob area. Preservation of motor function in brain tumor surgery involving the peri-rolandic regions is a challenge for neurosurgeons. Intraoperative neurophysiological monitoring (IOM) through direct electrical stimulation (DES) is commonly employed When this region is exposed, DES can be performed with a monopolar stimulation probe; otherwise, the positioning of a subdural strip electrode is required for continuous monitoring of motor evoked potentials (MEPs) during the resection [3]. Mass effects associated with brain tumors can distort these common relations; on the other hand, functional areas may be relocated to other brain regions, making anatomy-based localization of eloquent areas more challenging [5]
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