Abstracts

Rationale: While idiopathic generalized epilepsy has historically been considered to not be associated with structural abnormalities, recent advances in quantitative neuroimaging have revealed a variety of subtle structural changes. There have been numerous diffusion tensor imaging (DTI) studies highlighting extensive white matter abnormalities in temporal lobe epilepsy, it is unknown if similar findings will be observed in generalized epilepsy. The objective of this study was to assess the integrity of white matter tracts in patients with idiopathic generalized epilepsy. Methods: Fifteen patients (11 females, 4 males, mean age 22.1 years±5.0 years SD, range 17-32 years) with idiopathic generalized epilepsy and sixteen age-matched (9 females, 7 males, mean age 22.1 years±4.5 years SD, range 17-31 years) healthy volunteers were scanned at 1.5T using DTI with 2 mm isotropic resolution (9.5 min scan). Eight major white matter tracts including anterior limb of internal capsule, corticospinal tracts, genu of corpus callosum, splenium of corpus callosum, inferior fronto-occipital fasciculus, inferior longitudinal fasciculus, superior longitudinal fasciculus and uncinate fasciculus were identified using a deterministic streamline tractography method based on a priori knowledge of anatomy. Diffusion parameters were compared between groups for each tract. Furthermore, correlation between total lifetime seizures and diffusion parameters was investigated using Pearson’s correlation coefficient. Results: DTI demonstrated reduced FA in anterior limb of internal capsule (patient group: FA=0.48, control group: FA=0.50, p<0.01) and inferior fronto-occipital fasciculus (patient group: FA=0.52, control group: FA=0.53, p=0.042) and elevated MD in inferior longitudinal fasciculus (patient group: MD=0.84×10^-3mm²s^-1, control group: MD=0.81×10^-3mm²s^-1, p=0.036) and superior longitudinal fasciculus (patient group: MD=0.74×10^-3mm²s^-1, control group: MD=0.72×10^-3mm²s^-1, p<0.02) compared to control group. No correlation between the life time seizure and any DTI parameters of any of the tracts was found. Conclusions: DTI tractography demonstrates multiple white matter abnormalities in idiopathic generalized epilepsy patients. The lack of correlation with total seizures suggests that these white matter diffusion abnormalities are not a secondary consequence of seizures.