Abstracts

Rationale: INTRODUCTION: Functional MRI allows preoperative brain mapping in patients with refractory epilepsy secondary to mesial temporal sclerosis (MTS). Atypical language lateralization occurs more often in left MTS patients. Although language difficulties are well recognized in left MTS patients, language impairment in patients with right MTS is still poorly understood. We compared fMRI brain activation patterns on language tasks in patients with temporal lobe epilepsy with right and left HS with a visual confrontation naming paradigm. Methods: METHODS: We studied 22 left (L) and 15 right (R) patients with epilepsy associated with right and left MTS, and 18 healthy controls (C). Patients and controls were 18 or older, had at least 8 years of education, and were all right handed. Patients and controls underwent a language battery test that included phonemic and semantic word list generation, confrontation naming (proper nouns, objects and verbs), responsive naming and comprehension tests. Patients underwent WADA testing that documented left hemisphere language dominance. Subjects underwent an fMRI study with a visual confrontation naming paradigm. Data were acquired using 3T MRI scanner with compressed GRE EPI BOLD images, (40ACPC oriented slices, 3.3mm isometric voxels, TR4s, TE30ms FA90), and normalization to MNI152 space. Paradigms were block designed, each with a five minutes' duration, and stimuli had balanced randomization. Data analysis was performed with FSL, with a nonparametric statistical inference approach, and motion correction. A between groups ANOVA comparison (patients leftXrightXcontrols) was performed with a significance level of p<0.05. Results: RESULTS: Patients and controls did not differ in terms of age (LMTS 34.0 +/- 8.9; RMTS 34.4 +/- 9.8; and C 32.5 +/-10.8yrs), and education (LMTS 10.7 +/- 2.0; RMTS 10.8 +/-2.0; and C 11.7 +/-2.1yrs). R and LMTS patients had comparable age at epilepsy onset (L 11.4 +/-6.7 vs. R 14.4 +/- 7.2yrs), epilepsy duration (L 23.0 +/-9.4 vs. R 20.1 +/-1.4 yrs) and history of an initial precipitating event (L50% vs. R73%). Both LMTS and RMTS performed worse than C in semantic fluency (fruit and supermarket items) and naming of proper nouns. RMTS patients performed worse than LMTS and controls in naming of verbs. On fMRI studies left and right MTS displayed increased BOLD effect in the right hemisphere on visual confrontation naming paradigms compared to C. There was no difference of BOLD effect patterns when we compared right and left MTS patients. Conclusions: CONCLUSIONS: Our findings indicate that language impairment and functional reorganization of language networks is not limited to dominant language hemisphere MTS, but it also occurs in non-dominant MTS. Rather than a lesion laterality effect, a more widespread disease effect appears to influence language function and reorganization in epilepsy associated with MTS. Factors related to disease process and, possibly treatment, other than lesion laterality or hemispheric dominance for language appears to play a role in these aspects of language dysfunction in these patient groups.