Tag: language lateralization

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fMRI activation in the middle frontal gyrus as an indicator of hemispheric dominance for language in brain tumor patients: a comparison with Broca’s area

Functional imaging

Neuroradiology (2016) 58:513–520

Functional MRI (fMRI) can assess language lateralization in brain tumor patients; however, this can be limited if the primary language area—Broca’s area (BA)—is affected by the tumor. We hypothesized that the middle frontal gyrus (MFG) can be used as a clinical indicator of hemispheric dominance for language during presurgical workup.

Methods: Fifty-two right-handed subjects with solitary left hemispheric primary brain tumors were retrospectively studied. Subjects performed a verbal fluency task during fMRI. The MFG was compared to BA for fMRI voxel activation, language laterality index (LI), and the effect of tumor grade on the LI.

Results: Language fMRI (verbal fluency) activated more voxels in MFG than in BA (MFG=315, BA=216, p<0.001). Voxel activations in the left-hemispheric MFG and BA were positively correlated (r = 0.69, p < 0.001). Mean LI in the MFG was comparable to that in BA (MFG = 0.48, BA = 0.39, p = 0.06). LIs in MFG and BA were positively correlated (r = 0.62, p < 0.001). Subjects with high- grade tumors demonstrate lower language lateralization than those with low-grade tumors in both BA and MFG (p = 0.02, p = 0.02, respectively).

Conclusion: MFG is comparable to BA in its ability to indicate hemispheric dominance for language using a measure of verbal fluency and may be an adjunct measure in the clinical determination of language laterality for presurgical planning.

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Retrospective Analysis of Interobserver Spatial Variability in the Localization of Broca’s and Wernicke’s Areas Using Three Different fMRI Language Paradigms

Brocas'area

J Neuroimaging 2015;25:626-633

To determine interobserver spatial variability in language area localization using three commonly employed language tasks.

MATERIALS AND METHODS With institutional review board approval, 125 fMRI time series from 50 different clinical language cases were retrospectively reviewed by three blinded readers who selected 3- dimensional points representing the perceived center of Wernicke’s and Broca’s areas using three language tasks (semantic decision, SD; sentence comprehension, SC; and silent word generation, WG). Point dispersion values were then calculated using the perimeter of the 3-dimensional triangle defined by the three readers’ selections.

RESULTS After resolving interobserver laterality disagreements, there was no difference in spatial variability between the three tasks (P = .069). The SD task had the fewest interobserver laterality disagreements (P = .028) and the SC task had fewer failed localizations for Broca’s area (P = .050) and Wernicke’s area (P = .013).

CONCLUSION While there were no differences between interobserver spatial variability in language area localization between the three tasks, language task choice impacts the accuracy of fMRI language area identification because tasks vary in their rates of interobserver laterality disagreements and failed localizations. A combination of tasks including one with low laterality disagreements (eg, SD) and one with few failed localizations (eg, SC) may offer the best combination.

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