gms | German Medical Science

Objective: In this study we attempted the preoperative localization of subsystems of language areas to define a more precise description of the eloquent cortex using functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG).

Methods: MEG measurements were carried out with a 2x37 channel biomagnetic system (Magnes II, 4-D Neuroimaging). Localization was performed by 1-dipole fit or beamformer analysis. For fMRI we used a 1.5T MR scanner with echo planar imaging (Sonata, Siemens Medical Solutions) and a block paradigm with 180 measurements in 6 blocks (rest alternating with activation, 25 slices, 3mm thickness & resolution TR=2470, TE=60). 140 patients with tumors neighbouring language areas were examined. During measurement they had to perform verbal tasks. For the MEG measurements two paradigms were performed in each patient, while in fMRI four paradigms were used. Paradigms differ in the extent of grammatical effort and involvement of receptive and expressive language function.

Results: In the frontal lobe above the classical Broca area, three areas are constantly found across all subjects and language tasks. Depending on the kind of language task, certain areas are more accentuated than others inidcating a different role in language processing. One of these areas, the pars triangularis at the top of the gyrus frontalis inferior, seems to be related to grammatical processing. In the temporal lobe at least two areas can be distinguished: One in the sulcus supratemporalis and one at the end of the Sylvian fissure. These areas are in accordance with results found during cortical stimulation by Duffau.

Conclusions: Detailed knowledge about the language processing network allows safer resections and a better understanding of possible neurological dysfunction.