Introduction: This study investigates whether the middle frontal gyrus (MFG) can be used as an indicator for language hemispheric dominance in brain tumor patients using task-free resting state fMRI (rsfMRI). We hypothesize no significant difference in language lateralization between the MFG and Broca’s Area (BA) and that the MFG can serve as a simple and reliable means of measuring language laterality. Methods: 51 patients with glial neoplasms. Using rsfMRI, the MFG was compared to BA for voxel activation, language laterality index (LI) and the effect of tumor grade on LI. LI derived by rsfMRI and task-based fMRI was compared in a subset of 40 patients. Results: Voxel activations in the left MFG and left BA were positively correlated (r = 0.47, p<0.001). Positive correlations were seen between the LI of BA and LI of MFG regions (r = 0.56, p < 0.0005). 27/40 patients (67.5%) showed concordance of LI based on BA using rsfMRI with LI based on a language task. 30/40 patients (75%) showed concordance of LI based on the MFG using rsfMRI with LI based on a language task. Conclusion: MFG is comparable to BA in its ability to determine hemispheric dominance for language using rsfMRI. Our results suggest the addition of rsfMRI of MFG to the list of noninvasive modalities that could be used in glioma patients to evaluate hemispheric dominance of language prior to tumor resection. In patients who cannot participate in traditional task-based fMRI, rsfMRI offers a task-free alternate to presurgically map eloquent cortex.

Purpose The purpose of this study was to compare the deterministic and probabilistic tracking methods of diffusion tensor white matter fiber tractography in patients with brain tumors. Materials and Methods We identified 29 patients with left brain tumors <2 cm from the arcuate fasciculus who underwent pre-operative language fMRI and DTI. The arcuate fasciculus was reconstructed using a deterministic Fiber Assignment by Continuous Tracking (FACT) algorithm and a probabilistic method based on an extended Monte Carlo Random Walk algorithm. Tracking was controlled using two ROIs corresponding to Broca’s and Wernicke’s areas. Tracts in tumoraffected hemispheres were examined for extension between Broca’s and Wernicke’s areas, anterior-posterior length and volume, and compared with the normal contralateral tracts. Results Probabilistic tracts displayed more complete anterior extension to Broca’s area than did FACT tracts on the tumor-affected and normal sides (p < 0.0001). The median length ratio for tumor: normal sides was greater for probabilistic tracts than FACT tracts (p < 0.0001). The median tract volume ratio for tumor: normal sides was also greater for probabilistic tracts than FACT tracts (p = 0.01). Conclusion Probabilistic tractography reconstructs the arcuate fasciculus more completely and performs better through areas of tumor and/or edema. The FACT algorithm tends to underestimate the anterior-most fibers of the arcuate fasciculus, which are crossed by primary motor fibers.

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BACKGROUND AND PURPOSE The corticobulbar tract of the face and tongue, a critical white matter tract connecting the primary motor cortex and the pons, is rarely detected by deterministic DTI fiber tractography. Detection becomes even more difficult in the presence of a tumor. The purpose of this study was to compare identification of the corticobulbar tract by using deterministic and probabilistic tractography in patients with brain tumor. MATERIALS AND METHODS Fifty patients with brain tumor who underwent DTI were studied. Deterministic tractography was performed by using the fiber assignment by continuous tractography algorithm. Probabilistic tractography was performed by using a Monte Carlo simulation method. ROIs were drawn of the face and tongue motor homunculi and the pons in both hemispheres. RESULTS In all subjects, fiber assignment by continuous tractography was ineffectual in visualizing the entire course of the corticobulbar tract between the face and tongue motor cortices and the pons on either side. However, probabilistic tractography successfully visualized the corticobulbar tract from the face and tongue motor cortices in all patients on both sides. No significant difference (P < .08) was found between both sides in terms of the number of voxels or degree of connectivity. The fractional anisotropy of both the face and tongue was significantly lower on the tumor side (P < .03). When stratified by tumor type, primary-versus-metastatic tumors, no differences were observed between tracts in terms of the fractional anisotropy and connectivity values (P > .5). CONCLUSIONS Probabilistic tractography successfully reconstructs the face- and tongue-associated corticobulbar tracts from the lateral primary motor cortex to the pons in both hemispheres.

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BACKGROUND AND PURPOSE:The default mode network normally decreases in activity during externally directed tasks. Although default mode network connectivity is disrupted in numerous brain pathologies, default mode network deactivation has not been studied in patients with brain tumors. We investigated default mode network deactivation with language task-based fMRI by measuring the anticorrelation of a critical default mode network node, the posterior cingulate cortex, in patients with gliomas and controls; furthermore, we examined default mode network functional connectivity in these patients with task-based and resting-state fMRI. MATERIALS AND METHODS:In 10 healthy controls and 30 patients with gliomas, the posterior cingulate cortex was identified on task-based fMRI and was used as an ROI to create connectivity maps from task-based and resting-state fMRI data. We compared the average correlation in each default mode network region between patients and controls for each correlation map and stratified patients by tumor location, hemisphere, and grade.RESULTS: Patients with gliomas (P ¼ .001) and, in particular, patients with tumors near the posterior default mode network (P , .001) showed less posterior cingulate cortex anticorrelation in task-based fMRI than controls. Patients with both left-and righthemisphere tumors, as well as those with grade IV tumors, showed significantly lower posterior cingulate cortex anticorrelation than controls (P = .02, .03, and ,.001, respectively). Functional connectivity in each default mode network region was not significantly different between task-based and resting-state maps.CONCLUSIONS: Task-based fMRI showed impaired deactivation of the default mode network in patients with gliomas. The functional connectivity of the default mode network in both task-based and resting-state fMRI in patients with gliomas using the posterior cingulate cortex identified in task-based fMRI as an ROI for seed-based correlation analysis has strong overlap. ABBREVIATIONS: BOLD ¼ blood oxygen level-dependent; DMN ¼ default mode network; FC ¼ functional connectivity; IPL ¼ inferior parietal lobule; LIPL ¼ left inferior parietal lobule; mPFC ¼ medial prefrontal cortex; PCC ¼ posterior cingulate cortex; RIPL ¼ right inferior parietal lobule; rs-fMRI ¼ resting-state fMRI; tb-fMRI ¼ task-based fMRI

R esting-state functional MRI is a technique that allows for the generation of functional MRI data while the patient is at rest (1). This technique depicts low-frequency blood oxygenation level-dependent (BOLD) signal fluctuation in the brain at rest and extracts regions with highly correlated resting-state time courses to form larger-scale "resting-state networks" that correspond to known functional networks and anatomic areas, including visual, motor, and language pathways (2,3). Resting-state functional MRI offers substantial potential as a clinical tool for the treatment of patients with brain tumors. Compared with traditional paradigm-driven functional MRI, resting-state functional MRI obviates task compliance from patients who are functionally impaired, allows the parallel assessment of functional networks in place of serial assessment across lengthy imaging sessions (2), and has been shown to more accurately identify anatomic correlates of functional regions (4,5). Resting-state functional MRI has also been successfully piloted in periand intraoperative settings (6-8).BOLD functional MRI studies have shown that brain tumors exert local effects that reduce BOLD functional MRI activation, through a hypothesized uncoupling of tumor vascular responses and neural activity:

Brain tumors lead to modifications of brain networks. Graph theory plays an important role in clarifying the principles of brain connectivity. Our objective was to investigate network modifications related to tumor grade and location using resting-state functional magnetic resonance imaging (fMRI) and graph theory. We retrospectively studied 30 low-grade (LGG), 30 high-grade (HGG) left-hemispheric glioma patients and 20 healthy controls (HC) with rs-fMRI. Tumor location was labeled as: frontal, temporal, parietal, insular or occipital. We collected patients’ clinical data from records. We analyzed whole-brain and hemispheric networks in all patients and HC. Subsequently, we studied lobar networks in subgroups of patients divided by tumor location. Seven graph-theoretical metrics were calculated (FDR p < 0.05). Connectograms were computed for significant nodes. The two-tailed Student t-test or Mann–Whitney U-test (p < 0.05) were used to compare graph metrics and clinical data. The hemispheric network analysis showed increased ipsilateral connectivity for LGG (global efficiency p = 0.03) and decreased contralateral connectivity for HGG (degree/cost p = 0.028). Frontal and temporal tumors showed bilateral modifications; parietal and insular tumors showed only local effects. Temporal tumors led to a bilateral decrease in all graph metrics. Tumor grade and location influence the pattern of network reorganization. LGG may show more favorable network changes than HGG, reflecting fewer clinical deficits.