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 contra-lesional homolog brain structures. There are indications in literature that contra-lesional activation might reflect a compensatory or dysfunctional process depending on the tumor localization (Thiel et al. 2006). The reasons for this are still unclear but certainly must be caused by processes in the microstructure. According to tumor localization there is the finding that frontal tumor more often express the isocitrate dehydrogenase 1 (IDH1) mutation than tumors in other brain areas (Lai et al. 2011). This study investigates if there might be an interaction of tumor localization and the IDH1 mutation.

Method: 28 patients with left inferior frontal and 29 patients with left temporoparietal primary glial tumors in eloquent brain areas were included in the analysis. All tumors had to be in eloquent brain areas. Out of this group 19 patients with inferior frontal and 9 patients with temporoparietal tumors were analyzed to assess a possible relationship of IDH1 mutation and functional plasticity. Functional magnetic imaging was performed at a 3T Siemens Allegra Scanner. During the language fMRI paradigm subjects had to perform covertly a verb generation task. Data analysis was done by using SPM 12 including the Marsbar toolbox and the Automated Anatomical Labeling Atlas for region of interest (ROI) definition and analysis.

Results: We found an increase in activation in contra-lateral homologue areas in patients with tumors in left inferior frontal eloquent areas, while patients with tumors in left posterior eloquent areas did not show a significant increase in activation in the homologue posterior areas. Additionally we found that patients with IDH positive tumors showed significant more activation in inferior frontal contra-lesional areas than patients with IDH negative tumors. A logistic regression analysis showed a positive correlation of IDH1 mutation and increased activation in the left caudate nucleus, angular gyrus and hippocampal formation.

Conclusions: This preliminary data provides first indications for the correlation of molecular markers and hemodynamic processes associated with cognitive functions.