Abstracts

Rationale: Tensor imaging has discovered the microstructural anomaly of brain not only in the patients with hippocampal sclerosis and focal cortical dysplasia but also in the patient with focal neocortical epilepsy and with nonvisible lesion in MRI. We used an objective image analysis method to quantify the relationship of diffusion tensor imaging (DTI) abnormalities in the major neural pathways with age of onset, duration of seizure and disease severity from the patients with chronic non-lesional epilepsy. Methods: Twenty-four patients and 29 age-matched healthy controls were studied. DTI and structural MRI scans were acquired. Individualized fiber-labeled MR imaging template was generated by transformation of template atlas to align with each subject s brain. Registration of interested regions that included major supratentorial pathways was made to estimate the values of fractional anisotrophy (FA) and apparent diffusion coefficient (ADC). The FA values and the ADC values of the delineated nerve tracts between the two groups were compared. Where the DTI parameters changed, the correlation with age of seizure onset, drug-resistance or disease duration was evaluated. Results: Increased ADC and decreased FA values were observed in all region-of-interests (ROIs) in our patients. The ADC in the sagittal stratum (SS) and the FA in the SS and posterior thalamic radiation (PTR) showed statistic differences (p < 0.01). Among the patient with onset before age of 10 years (n=12), the elevated ADC values in the splenium of corpus callosum (SCC), SS and anterior corona radiate (ACR); and the decreased FA values in the body of corpus callosum (BCC), cingulum (CGC), SS, uncinate fasciculus (UNC) and PTR were showed significantly. In the drug-resistant subgroup (n=10), the ADC increase was significantly in the SS and PTR; and the FA decrease was in the SS. Duration of epilepsy (n= 9, 10 years) was significantly related with ADC increase in the F, T, SS, UNC, ACR and PTR. The white matter alterations in the patients with later onset, shorter disease duration or good medical effect did not achieve statistical significance. Significant correlations were observed between diffusion parameter alterations and duration of disease in GCC, ACR, PTR and SS.Conclusions: We computed the two diffusion parameters using automated approaches to prevent differences from manual ROI setting. The significant correlation between diffusion parameter and clinical variable supports that pre-existing brain abnormality and progressive brain degeneration in patients with chronic and severe epilepsies.