Does education play a role in language reorganization after surgery in drug refractory temporal lobe epilepsy: An fMRI based study?

Abstract

ObjectivesPatients with drug refractory epilepsy (DRE) and a high level of education may differ in their language recovery after surgery. Our aim was to determine whether there were differences in the extent of improvement and pattern of reorganization of language functions on functional magnetic resonance imaging (fMRI) after surgery to treat refractory temporal lobe epilepsy (TLE) between patients with more than 12 years of formal education versus those with a shorter period of regular schooling. MethodsAfter approval by an institutional ethics committee, 60 right-handed, adult patients of left TLE and 20 right-handed, healthy controls were recruited to the study. Multiple aspects of language (Repetition, Naming, Word fluency, Visual word and Comprehension reading) were tested using the Indian Aphasia Battery (IAB) in the Hindi language; fMRI was performed using a standardized Hindi language paradigm (lexical, semantic, syntactic and comprehension components) in both cases and controls, before and after an anterior temporal lobectomy (in cases) with a 1.5T MR Scanner. An array of performance tests of intelligence and the verbal adult intelligence scale (VAIS) were used to measure the Intelligence Quotient (IQ) in Left TLE (LTLE) patients before and after surgery. Language laterality was estimated using the laterality index (LI-toolbox-spm8). Cohen’s d test was performed to determine the effect sizes of the differences in the IAB scores, and Pearson’s correlation was applied between regional (IFG and STG) activation in controls and TLE patients with more than 12 years of schooling [higher educational status (HES subgroup)] and those with less than 12 years of schooling [lower educational status (LES subgroup)]. ResultsAt the baseline, clinical testing with IAB showed better scores in controls than in cases. Better scores were observed in subjects with higher levels of education than in those with lower levels of education. An improvement was observed in IQ scores in both the HES and LES groups after ATLR; significant worsening in the abstract ability subtest was noted in the LES group, whereas in the HES group there was an improvement. Blood-oxygen-level dependent (BOLD) activation during language tasks was observed in both cerebral hemispheres in the TLE cases, while it was observed in the traditional left hemispheric language areas in controls. Postoperatively, greater BOLD activation was observed in the left inferior frontal gyri (IFG, r=0.65*; p<0.05), middle frontal gyrus (MFG, r=0.77**; p<0.01) superior temporal gyri (STG, r=0.88* p<0.02) and angular gyrus (AG, r=0.73*; p<0.04) in HES compared to LES subjects. Similarly, LI showed left lateralization of the frontal (LIw=0.77 & 0.71) and temporal (LIw=0.74 & 0.5) regions in controls and the TLE group (post-surgery) compared to the pre-surgery group during language tasks. ConclusionsGreater improvement in language skills and BOLD activation in the left hemisphere in TLE-patients (after epilepsy surgery) with a high level of education was similar to that of healthy controls, implying that education has an effect on the functional reorganization/recovery of language areas.