Abstracts

The corpus callosum is the most important interhemispheric commissural connection. It is implicated in the interhemispheric propagation of epileptic activity. Axons in a rostral position connect the frontal lobes (FL), in the isthmus and splenial portion the temporal lobes (TL).
The aim of this study is to explore volume and diffusivity measures of the corpus callosum (CC) in patients with temporal (TLE) and frontal lobe epilepsies (FLE) in comparison to healthy subjects. We hypothesize that atrophy and diffusion changes of the CC in TLE and FLE will show distinct differences., Eighteen controls and 51 patients (27 TLE, 24 FLE) underwent Diffusion Weighted Imaging (DWI) and T1 volumetric scans on a 1.5T MRI. The CC was divided into 7 previously defined Witelson Regions (WR).Using in house developed software, the volume (cm3) on high-resolution T1-weighted scans was measured for each region and for the whole CC Volume, these were then corrected for smaller total brain volumes in patients with respect to control volumes. The apparent diffusion coefficients (ADCs, 10-5mm2s-1) for the entire CC and three areas of interest within WRs 2,4 and 6 were measured from the co-registered ADC map. Analysis comparing both syndromes, with respect to age of onset and duration of epilepsy was performed., 1. Volumes: The corpus callosum of TLE (5.8[plusmn]0.8 cm3) and FLE (6.1[plusmn]1.2cm3) patients is significantly smaller than controls (7.4[plusmn]0.8 cm3, p[lt]0.01). In TLE, only WR 6 showed a significant decrease in volume compared to controls (0.5[plusmn]0.9 cm3 vs 0.8[plusmn]0.1 cm3, p[lt]0.01). In FLE, only WR 1 was significantly smaller compared to controls (0.2[plusmn]0.08 cm3 vs. 0.3[plusmn]0.08 cm3, p[lt]0.01).
An early onset of epilepsy is seen with a greater loss in volume than a later onset in both TLE and FLE (p[lt]0.01).
2. ADCs: ADC values of the CC of TLE (119.5[plusmn]18.7 10-5mm2s-1) and FLE (130.0[plusmn]8.8 10-5mm2s-1) patients are significantly higher than controls (106.7[plusmn] 9.0 10-5mm2s-1). WR 6 in TLE shows an increase in ADC in comparison to controls (139.7[plusmn]43.6 10-5mm2s-1 vs. 109.3[plusmn]21.4 10-5mm2s-1, p[lt]0.01). In FLE, WR 2 shows an increase in ADC (135.2[plusmn]8.8 10-5mm2s-1 vs, 106.4[plusmn]29.3 10-5mm2s-1, p[lt]0.01). Diffusivity increases through out the first decade of disease duration. However, ADCs beyond the first decade remain elevated but do not increase further., Atrophy of the CC and increased diffusivity provide evidence of damage to commissural fibers in patients with TLE and FLE. This effect appears most prominent in regions of the CC connecting the homotopic cortical region contralateral to the respective epileptogenic zone.,