Abstracts

Rationale: We aimed to characterize patterns of language activation assessed by fMRI in patients with focal epilepsy while considering seizure and demographic variables.Methods: 220 patients with focal epilepsy (mean age 21.9 years, range 4-57 years; 133 left focus, 87 right focus) performed an auditory description decision task using fMRI with 3T EPI BOLD techniques, analyzed using SPM2. Language activation patterns were characterized using region of interest laterality index: inferior frontal gyrus (IFG) and Wernicke s area (WA). Language dominance was deemed left, right, bilateral, or crossed based on the regional laterality indices (LI<0.20 atypical). We examined if atypical language was influenced by gender, age, handedness, age of seizure onset, and side of seizure focus.Results: Similar to previous studies, 25.5% (n=56) had atypical language dominance. Patients with atypical language were more likely to have seizure onset before age six (X²=6.825, p<0.01) and to be left handed (X²=12.25, p<0.0001). There were no differences in gender, age, or side of seizure focus between the atypical and typical language groups (p>0.05). The distribution of MRI type was different between patients with atypical and typical language (X²=17.8, p<0.01) with atypical patients more likely to have a vascular pathology (21.4% vs. 6.1%), while the typical patients were more likely to have normal MRI (32.9% vs. 21.4%). Six patterns of atypical language activation emerged. Three right dominant patterns accounted for 48.2% of the atypical group (23.2% had the pattern of right (R) IFG/ R WA, 12.5% had R IFG/ bilateral (B) WA, and 12.5% had B IFG/ R WA). Two patterns of crossed dominance accounted for 46.5% (28.6% had R IFG/ left (L) WA, 17.9% had L IFG/ R WA). The remaining 5.4% had a symmetrically bilateral pattern (B IFG/ B WA). The distribution of atypical language patterns differed with age of seizure onset (X