Abstracts

Rationale: In children with temporal lobe epilepsy, DTI studies have shown decreased anisotropy ipsilateral as well as contralateral to the side of seizure onset. In the present study, we evaluated water diffusion changes in three major temporal lobe white matter tracts of children with temporal lobe epilepsy. In addition to fractional anisotropic index, we used other tensor indices which describe the water diffusion changes in terms of linear (Cl), planar (Cp), and spherical (Cs) geometric shapes. Methods: We selected 13 children (mean age: 10.9 years ± 6.3, range:1– 19 years, 8 females and 5 males) with temporal lobe epilepsy who showed left temporal lobe FDG hypometabolism with normal MRI findings. Twelve normal age-matched volunteers (mean age: 13 ± 3.4, range: 7 – 18 years, 7 females and 5 males) were used as controls. DTI images were acquired using a 3-Tesla GE MR Scanner and tensor calculation and tractography for uncinate (UNF), arcuate (ARF), inferior longitudinal fasciculus (ILF) and corticospinal tract (CST) of both hemispheres were performed using DTI Studio. (FA, Cp, Cl, and Cs) and their lateralization indices were calculated from the three eigenvalues (λ1, λ2, λ3). Duration of epilepsy (DUR) was calculated from the time of clinical seizure onset to the date of MRI acquisition. Statistical analysis involved repeated measures analysis of covariance (controlled for age) with group (patients, and controls) as the between-subject factor, and side (left and right) and tract (UNF, ILF, ARF, and CST) as within subject factors. Partial correlation (controlled for age) was performed between tensor parameters (FA, Cl, and Cs,) and their lateralization index of the affected side with DUR in all three temporal lobe tracts.Results: The mean values of the tensor parameters (FA, and Cs) in all four tracts (UNF, ARF, ILF and CST) in the affected left hemisphere of patients were significantly (p < 0.05) different from those of controls. The mean values of FA, were decreased and Cs were increased in the patient group compared to controls. In the patient group, Cs of the left UNF and ARF showed significant positive partial correlation (r = 0.632, p = 0.027, r = 0.601, p = 0.039, respectively) with DUR. LAT (Cs, FA) of left UNF also showed significant partial correlation (r = 0.788, p = 0.002, r = -0.601, p = 0.039, respectively) with DUR. Significant three way interaction (F = 4.9, p = 0.010) of Cs values showed reversal of normal left-right asymmetry in ARFConclusions: Our results suggest loss of anisotropy bilaterally in all three temporal lobe tracts and in corticospinal tract compared to controls. Our results further describe the effect of chronic seizure activity associated with progressive degenerative structural change in relation to loss of anisotropy in ipsilateral UNF and ARF. Reversal of normal left-right asymmetry in ARF suggests possibility of reorganization of language function to the contralateral right hemisphere. However, such language reorganization to the contralateral hemisphere needs to be further validated with tools such as fMRI or Wada test.