gms | German Medical Science

Objective: The assessment of presurgical language laterality during presurgical fMRI in brain tumor patients is an important information in surgical planning. However, language laterality assessment is among other factors mostly dependent on the choice of fMRI language paradigm and as it is assumed the implementation of a language control condition to differentiate between essential and non-essential language-related processes. The aim of this study was to investigate how or if language laterality assessment is affected by a fMRI-language paradigm design using a linguistic control condition as well as how this interacts with brain tumor localisation.

Methods: In total 53 brain tumor patients were included in this analysis (26 frontal tumors, 14 anterior temporal tumors, 13 posterior temporal and inferior parietal lobe tumors). During preoperative fMRI patients performed covertly a verb generation task, while a covert phonological generation task (syllable reversal) served as the linguistic control condition. Data analysis was done by using SPM12 comprising realignment, coregistration and smoothing for preprocessing. Whole brain analysis was performed using the general linear model approach on individual level. Laterality indices (LIs) with and without control conditions application were calculated for the frontal, parietal and temporal lobe using the LI-toolbox implemented in SPM. Inner- and between group differences were assessed by using non-parametric t-tests.

Results: The application of a linguistic control condition led to significant higher LIs in the temporal lobe of patients with frontal (p=014) and anterior temporal tumors (p=001), which was not found in patients with posterior temporal/inferior parietal. Comparing this group with patients with anterior frontal tumors, the former group showed significant higher LIs the parietal lobe (p=.025) and the temporal lobe (p=.048) when a control condition was applied, and a lower LI in the frontal lobe when no control condition was applied (p=.017). LIs in patients with posterior temporal/inferior parietal were compared to frontal tumors higher in the parietal lobe with (p=.034) and without (p=.037) control condition as well as in the temporal lobe (p=.018) when a control condition was used.

Conclusion: This data suggests that laterality indices are strongly influenced by language paradigm design using linguistic control condition and by brain tumor localisation.