Abstracts

Rationale: An early age of epilepsy onset and length of epilepsy duration have been associated with cognitive dysfunction in patients with epilepsy. Furthermore, early age of epilepsy onset has been associated with structural changes in patients with temporal lobe epilepsy (TLE). The purpose of the present study is to evaluate the effect age of onset and duration of epilepsy on the cognitive networks involved in working memory and language of patients with frontal lobe epilepsy (FLE).Methods: We studied 48 FLE patients and 25 controls with two working memory and two language functional MRI (fMRI) paradigms using a 3 Tesla scanner. Activation maps for working memory and language task were built for each subject and compared in a second level analysis against control subjects using Statistic Parametric Mapping (SPM 5). We performed regression analysis for the effects of epilepsy duration and age of onset. Additionally, age of onset was further dichotomised into onset groups before and after the age of 13 to account for frontal lobe maturation. Neuropsychological measures of working memory and language were acquired for each subject outside the scanner. Results: FLE patients had a mean age of onset of 10 years, (range 2 to 31) and a mean epilepsy duration of 22 years (range 3 to 47). FLE patients showed decreased activation in working memory and language networks relative to controls. Longer duration of epilepsy was negatively correlated with activation within the fronto-parietal regions that constitute the working memory network and the left frontal regions involved in language tasks. Early age of onset was associated with a reduced network activity in the same regions relative to controls, whereas activation maps of patients with late onset were not different from controls. Performance on working memory and language tasks was not significantly different in patients with an early onset compared to those of late onset, but neuropsychological scores showed a trend towards poorer performance for those patients with longer epilepsy duration and early age of onset across all the tasks. Conclusions: Our data suggest that an early age of onset prior to crucial stages in brain maturation may have a greater effect on cognitive networks compared to patients with epilepsy onset after complete maturation of the frontal lobes.