Abstracts

Rationale: Abnormal oscillation of cortico-thalamic loop may contribute the pathogenesis of idiopathic generalized epilepsy (IGE). Recently, several neuroimaging studies using various methods have reported abnormal metabolism and minute structural changes of these regions in IGE patients. In this study, we investigated the possible role of diffusion-tensor imaging (DTI) as well as proton magnetic resonance spectroscopy (1H-MRS) in patients with IGE. Methods: Thirteen IGE patients (12 juvenile myoclonic epilepsies and one generalized tonic-clonic seizures on awakening) and 26 healthy controls were investigated. 1H-MRS measurement of NAA, choline (Cho), and creatinine (Cr) was done in thalamus, frontal and parietal cortex, anterior cingulate gyrus, and lenticular nucleus with quantitative multi-voxel method in two horizontal planes of mid-thalamus and just above corpus callosum level using a 3 T machine. DTI was made for trace-D, ADC, and FA using a same scanner and we executed the post-processing work, such as statistical parametric mapping (SPM). Results: Compared with normal control, NAA/Cr ratio of IGE patients was significantly decreased in the thalamus (1.76 vs. 1.57, p=0.001) and anterior cingulate gyrus (1.43 vs. 1.22, p=0.001). However, no significant difference between control and IGE patients was noted in frontal convexity (1.95 vs. 1.84, p=0.105), lenticular nucleus (1.55 vs. 1.42, p=0.091), and parietal cortex (2.09 vs. 1.99, p=0.207). ADC value of the patients increased over frontal convexity, especially around the anterior cingulate gyrus, but not in the thalami. Volumetry of bilateral thalami failed to show any significant difference. Conclusions: Along with thalamic dysfunction, there was also evidence of cortical dysfunction, especially in the frontal and anterior cingulate gyrus in this study, suggesting thalamo-cortical circuitry as a substrate of seizure generation in IGE patients