Entorhinal Cortex, Perirhinal Cortex Volume And Cognitive Impairment In Idiopathic Generalized Tonic-clonic Seizures

Purpose: According to the definition of the International League Against Epilepsy, idiopathic generalized epilepsy with generalized tonic-clonic seizures (IGE-GTCS) is characterized by no neuroradiological signs. However, several volumetric brain studies using magnetic resonance image (MRI) have presented some findings which suggested that patients with IGE might have some morphological abnormalities in some brain regions. And our previous study also demonstrated patients with IGE-GTCS had volume reductions in hippocampus which were correlated with some aspects of cognitive impairment, while amygdale and parahippocampal volume had not. The medial temporal lobe is composed of the hippocampus, amygdala, entorhinal, perirhinal, and parahippocampal cortices. They have close anatomical connections with each other, and correlated with cognitive function. This study aimed to compare the volume of entorhinal cortex and perirhinal cortex between patients with IGE-GTCS and healthy controls, and to investigate the relation between volume and clinical variables, cognitive function in patients with IGE-GTCS.Methods: The participants included thirty patients with IGE-GTCS (15 males and 15 females) and 32 age, gender, and education matched healthy controls (15 males and 17 females). All subjects were right-handed. The imagines were acquired on a 1.5 T GE Signa MR scanner and were processed on a Unix workstation (Silicon Graphics, Mountain View, CA, USA) with the software package Dr View 2.0. Entorhinal cortex and perirhinal cortex were manually traced on consecutive coronal 1-mm-thick slices from anterior to posterior, and with the corresponding sagittal and axial planes simultaneously presented as references. Volumes of entorhinal cortex and perirhinal cortex were calculated by the software automatically. Wechsler Adult Intelligence Scale-Revised in China (WAIS-RC) was adopted to valuate each participant. WAIS-RC provided scores for all its 11 subsets, as well as a verbal intelligence quotient (VIQ), a performance intelligence quotient (PIQ), and a full scale intelligence quotient (FSIQ). Kaufman factor scores were obtained by summing subset scores that loaded the individual factors: verbal comprehension (VC), perceptual organization (PO), freedom from distractibility (FD). Group differences for age, education were assessed using independent-samples T test, and gender difference was evaluated with theχ2 test. Statistical differences in the regional volume measures were analyzed using repeated measures multivariate analysis of covariance (MANCOVA) with ICV and age as covariates for each region. Pearson's partial correlation coefficients were calculated to examine the relationships between volume of entorhinal, perirhinal cortex and clinical variables, and volume of entorhinal, perirhinal cortex and scores of WAIS-RC. The significance level was set at p < 0.05.Results: In patients group, the mean volume of the left entorhinal cortex was (1.38±0.05) cm~3, the right was (1.56±0.06) cm~3, the mean volume of the left perirhinal cortex was (1.77±0.07) cm~3, the right was (1.80±0.08) cm~3. In controls, the mean volume of the left entorhinal cortex was (1.52±0.04) cm~3, the right was (1.61±0.05) cm~3, the mean volume of the left perirhinal cortex was (1.88±0.06) cm~3,the right was (1.79±0.04) cm~3. Compared with controls, patients with IGE-GTCS had no significantly decreased volumes either in entorhinal cortex or in perirhinal cortex. The right entorhinal cortex volume was significantly negatively correlated with total number of seizures(r=-0.49,p=0.01) and seizure frequency(r=-0.50,p=0.01). The right perirhinal cortex volume was significantly negatively correlated with seizure frequency(r=-0.42, p=0.03). There was no significant correlation between volume of entorhinal cortex, perirhinal cortex and cognitive impaired in patients with IGE-GTCS.Conclusions: Patients with IGE-GTCS had not volume alterations in entorhinal cortex and perirhinal cortex. The right entorhinal cortex volume was negatively correlated with total number of seizures and seizure frequency; the right perirhinal cortex volume was negatively correlated with seizure frequency. The cognitive impaired was not correlated with volume of entorhinal cortex and perirhinal cortex in patients with IGE-GTCS.