Correlation between language organization and diffusion tensor abnormalities in refractory partial epilepsy.

PURPOSE

Atypical language organization is more frequently found in patients with refractory partial epilepsy than in healthy controls; however, the reasons for this are not well known. Here we assess the relation between language laterality index (LI) and white-matter tract changes.

METHODS

Nine patients with refractory partial epilepsy were assessed with a 3-T GE scanner. Functional magnetic resonance imaging (fMRI) of language and diffusion tensor imaging (DTI) were acquired. For the fMRI, a noun-verb generation task was performed, all images were motion corrected, and activated pixels in classic language areas were counted. The DTI images were acquired in six standard directions with an initial non-diffusion-weighted scan. The "average anisotropy" was determined in a region of interest in the frontal lobe, temporal lobe, and parietal lobe white matter. An asymmetry index (AI) was calculated for language and DTI. Atypical language lateralization was diagnosed if the lateralization index (LI)-language was smaller than 0.4.

RESULTS

Two of the nine patients had atypical language localization (LI-language, -0.6, and 0.3); both had left temporal DTI asymmetry (LI-DTI, -0.3 and -0.2). The remaining seven patients had typical language localization, and no marked DTI abnormalities. Asymmetry in temporal lobe DTI correlated with LI-language (r= 0.8; p = 0.006).

CONCLUSIONS

Atypical language lateralization in patients with partial epilepsy may be associated with white-matter tract abnormalities.