Volume Of Subcortical Structures And Cognitive Impairment In Idiopathic Generalized Tonic-clonic Seizures

Objective: Idiopathic generalized epilepsy with generalized tonic-clonic seizures only (IGE-GTCS) is one subtype of idiopathic generalized epilepsy (IGE),and its pathophysiology might be somewhat different from other subtypes. Functional studies (EEG, fMRI, MRS, and PET) suggest that striatum-thalamo–cortical network plays an important role in the pathophysiology of IGE. However, few studies have focused on IGE-GTCS to examine its morphological changes in the structures involved in this network, and have provided conflicting results. This study aimed to investigate volumetric changes of the thalamus, caudate, lentiform nucleus and anterior limb of the internal capsule (ALIC), as well as the relations between volume and cognitive impairment in patients with IGE-GTCS.Methods: The participants included thirty patients with IGE-GTCS (15 males and 15 females) and 32 healthy controls (15 males and 17 females). They were age, gender, and education matched. The patients were recruited from the Epilepsy Clinic of the Department of Neurology, First Affiliated Hospital of DaLian Medical University, and all patients fulfilled the criteria of IGE-GTCS according to the International League against Epilepsy. The imagines were acquired on a 1.5 T GE Signa MR scanner. With the software package Dr View 2.0, thalamus, caudate, lentiform nucleus and anterior limb of the internal capsule (ALIC) were manually traced on consecutive coronal 1-mm-thick slices, from anterior to posterior, with the corresponding sagittal and axial planes simultaneously presented as references to confirm the accuracy. Wechsler Adult Intelligence Scale—Revised in China (WAIS-RC) was administered to each participant on the same day of magnetic resonance imaging (MRI) scan. Group difference for age, education was assessed using independent-samples T test, and gender difference was evaluated withχ2 test. Statistical differences in the regional volume measures were analyzed using repeated measures multivariate analysis of covariance (MANCOVA). Pearson's partial correlation coefficients were calculated to examine the relationship between the volume of and clinical variables, and between volume and scores of WAIS-RC. The significance level was set at p < 0.05.Results: Compared with controls, patients with IGE-GTCS had no significant difference in the volume of thalamu(sF = 1.65, df = 56, p = 0.205), caudate(F = 0.15, df = 56, p = 0.700), lentiform (F = 1.18, df = 56, p = 0.282)and ALIC(F = 0.29, df = 56, p = 0.593). The right thalamic volume was significantly negatively correlated with total number of seizure (r=-0.399,p= 0.039). The volume of ALIC was significantly negatively correlated with total number of seizures(r=-0.400,p= 0.039) and seizure frequency(r=-0.408,p=0 .035). The thalamic volume was significantly positively correlated with WAIS's sub-score of comprehension, arithmetic, similarity, vocabulary, block-design, verbal comprehension, and perceptual organization and so on; the volume of anterior limb of internal capsule was significantly positively correlated with WAIS's sub-score of comprehension, arithmetic, vocabulary, block-design, and perceptual organization and so on.Conclusion: 1.Patients with IGE-GTCS had no significant volume reduction in thalamus, caudate, lentiform nucleus and ALIC compared with normal controls; 2. Right thalamus volume was related to total time of seizure and right ALIC volume with seizure frequency and total time of seizure; 3. Volume of the thalamus, ALIC were correlated with some aspects of cognitive impairment.