Abstracts

Rationale: Atypical language dominance is common in patients with temporal lobe epilepsy. We examined the association of left temporal hypometabolism with laterality of fMRI activation in a language task. Methods: 30 patients with temporal lobe epilepsy [mean age 32.4 11.0 years (range 18-55); epilepsy onset 15.3 11.3 years (range 0.8-40); 22 left focus, 8 right focus], had FDG-PET using non-invasive cardiac input function. After MRI-based partial volume correction, regional glucose metabolism (CMRglc) was measured and asymmetry index, AI=2(L-R)/(L R), calculated. fMRI language dominance was assessed with an auditory definition decision paradigm at 3T. fMRI data were analyzed in SPM2 using ROIs from Wake Forest PickAtlas [Wernicke s Area (WA), Inferior Frontal Gyrus (IFG), Middle Frontal Gyrus (MFG)] and bootstrap Laterality Index, LI=(L-R/L R). Results: 19 patients had ipsilateral temporal hypometabolism; 3 of 4 patients with atypical language had abnormal FDG-PET. Increasing left mid-temporal hypometabolism correlated with decreased MFG LI (r=-0.41, p<0.05) and showed trends with WA LI (r=-0.37, p=0.055) and IFG LI (r= -0.31, p=0.099); these relationships became more significant after controlling for age of onset. Increasing hypometabolism was associated with fewer activated voxels in WA ipsilateral to the focus and more activated voxels contralaterally, but overall, activation amount in left WA was similar to subjects without left temporal hypometabolism (t=-1.39, p>0.10). Conclusions: We did not find evidence of impaired BOLD response in hypometabolic cortex. Decreased laterality in the presence of increased hypometabolism likely reflects disrupted left temporal lobe function. Regional hypometabolism may explain why some patients with MTS and normal MRI show atypical language.