gms | German Medical Science

Objective: Lesions caused by brain tumors in eloquent brain areas may trigger functional reorganization of language processing. A common finding is enhanced language-associated activation in contralesional homolog brain structures. It remains to be clarified whether such activations support language processing or are maladaptive, leading to reduced transcallosal interhemispheric inhibition. The effect of tumor localization on functional reorganization also needs further investigation.

Method: Fourteen patients with left frontal, 22 patients with left temporoparietal primary glial tumors in eloquent brain areas but without any language or speech deficits and 23 healthy subjects were included in the study (mean age patients: 45.8 years, 21 male; mean age controls: 28.8 years, 14 male). Language performance was assessed using the Regensburger Verbal Fluency Test. All patients were at a percentile rank above 15. Functional magnetic imaging was done in a 3T Siemens Allegra Scanner. Patients performed covertly a verb generation task, with a covert phonological generation task (syllable reversal) served as the control condition. Data analysis was done by using SPM12 with the Marsbar toolbox and the Automated Anatomical Labeling Atlas for region of interest (ROI) definition and analysis. A laterality index was calculated by building the ratio of the difference between the number of left and right active voxels and the sum of those voxels. Only voxels in eloquent areas predefined by normalized ROIs were included in the analysis.

Results: With one exception, all patients showed left-hemispheric language lateralization. We found an increase in language-associated activation according to the verb generation task only in patients with left temporoparietal tumors compared to healthy controls in the right angular gyrus and the right posterior cingulate cortex. The magnitude of activation in the angular gyrus correlated positively with language performance in that patient group (r = .70; p < .001). The magnitude of right lateral language associated activation in the inferior frontal gyrus correlated negatively with language performance in patients with left frontal tumors (r = -.67; p = .009).

Conclusions: In patients with inferior frontal tumors, the contralesional increase of activation suggests a dysfunctional maladaptive process. Patients with temporoparietal tumors exhibit compensatory processes reflected in the positive correlation of language performance and enhanced activation in the angular gyrus.