Abstracts

The corpus callosum(CC) topologically connects to homotopic and heterotopic cortical regions of the brain. The posterior portions of CC are known to link the temporal lobes. In Temporal lobe epilepsy (TLE), seizures may propagate to the other hemisphere through the corpus callosum or anterior commissure. The diffusion tensor imaging (DTI) is a novel MR imaging technique to give microstructural data which cannot be obtained by conventional images. In DTI, anisotropy is influenced by density of fiber, neuroglial cell packing, degree of myelination, and individual fiber diameter, which are likely correlated with neuronal loss and gliosis. We observed the differences in Fractional Anisotropy (FA) and Apparent Diffusion Coefficient (ADC) at various areas of CC from Diffusion Tensor Imaging(DTI)., Eleven medically intractable TLE patients (2 MTLE, 9 neocortical TLE) who had seizure-free surgical outcome were compared to ten healthy controls. FA and ADC values were obtained from seven Witelson Regions (WRs) of CC. Region of Interests were outlined at the midline on the axial slices with covering the whole length of each WR. We visually analyzed the connections through each WR between hemispheres by tractography. We reviewed the clinical severity including duration of epilepsy, seizure frequency and frequency of secondary generalized seizures as well as bilaterality and Ictal propagation pattern on EEGs., In controls, FA value was higher at the genu (WR 2) and splenium (WR 7) than other WRs (p [lt]0.05). In TLE patients, FA values were decreased at rostrum (WR 1), genu (WR 2) (p [lt]0.05) as well as splenium (WR 7) compared controls (p[lt]0.01). The degree of FA abnormality was not related to the duration of epilepsy, seizure frequency or frequency of secondary generalized seizures. No statistically significant ADC changes were observed., Decreased FA value at rostrum, genu and splenium suggests that the pathologic change extends to corpus callosum in TLE patients. The prominent difference at splenium may reflect the specific damage of tapetum (white matter fiber tract to temporal lobe from CC), which is probably caused by Wallerian degeneration. Less prominent damage of the rostrum and genu could imply indirect spread via the uncinate fascicules and orbitofrontal regions from the temporal lobe to the contralateral hemisphere. This finding provides an additional evidence for diffuse white matter damage in TLE patients.[table1],