Abstracts

Rationale: Functional Magnetic Resonance Imaging (fMRI) is used to assess language function in preoperative evaluation of patients with temporal lobe epilepsy (TLE). Atypical language lateralization seems to occur more often in these patients and may predict naming deficit after surgery. fMRI and WADA studies have shown that left TLE patients have higher rates of atypical language lateralization compared with right mesial temporal sclerosis (MTS) patients. We compared patterns of activation in the inferior frontal gyrus (Broca's area) in patients with TLE associated with left and right hippocampal sclerosis with a multitask language paradigm. Methods: Twenty patients with left (L) and 12 right (R) TLE due to hippocampal sclerosis (HS), and 22 healthy controls (C) underwent a fMRI study involving four language paradigms: word generation, visual confrontation naming, written sentence responsive naming, phonologic and semantic language decision. Patients and controls were 18 or older, had at least eight years of education, and were all right handed. In addition to fMRI, patients and controls underwent a psychometric evaluation of language functions that included phonemic and semantic verbal fluency, visual confrontation and responsive naming. Data were acquired using a 3T MRI scanner with compressed GRE EPI BOLD images, (40 ACPC oriented slices, 3.3mm isometric voxels, TR=4s, TE30ms/ FA90), and normalization to Talairach space. All 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 group ANOVA comparison (L x R x C) was performed with a significance level of p<0.05. Results: Patients and controls were comparable in terms of age (L 35.0; R 35.1; C 32.5), and education (L 10.8; R 10.5; and C 11.7yrs). R and L MTS patients had comparable age at epilepsy onset (L 10.3 vs. R 12.8), epilepsy duration (L 22.8 vs. R 22.5) and occurrence of an initial precipitating event (L 27% vs R 30%). On Psychometric language evaluation both right and left MTS patients performed significantly worse than controls, without statistically significant difference between L and R MTS groups in tests measuring verbal fluency (L51.8vs.R51.2vs.C64.2), confrontation naming (L54.8vs.R56.9vs.C66.9) and responsive naming (L18.2vs.R18.3vs.C20.1). Both L and R MTS groups showed decreased bold effect in the left inferior frontal gyrus only in the semantic and phonologic decision paradigms. We found no differences in left inferior frontal gyrus activation between L and R MTS patients in all paradigms. Conclusions: Patients with left and right MTS displayed decreased inferior left frontal gyrus activation on language paradigms, without a laterality effect. Factors related to disease process and, possibly treatment, other than lesion laterality or hemispheric dominance for language appear to play a role in these aspects of language dysfunction in these patient groups.