Altered gray matter volume in MRI-negative focal to bilateral tonic-clonic seizures

Mapping progressive damage epicenters in epilepsy with generalized tonic-clonic seizures by causal structural covariance network density (CaSCNd)

AIMS

Mapping progressive patterns of structural damage in epilepsies with idiopathic and secondarily generalized tonic-clonic seizures with causal structural covariance networks and multiple analysis strategies.

METHODS

Patients with idiopathic generalized tonic-clonic seizures (IGTCS) (n = 114) and secondarily generalized tonic-clonic seizures (SGTCS) (n = 125) were recruited. Morphometric parameter of gray matter volume was analyzed on structural MRI. Structural covariance network based on granger causality analysis (CaSCN) was performed on the cross-sectional morphometric data sorted by disease durations of patients. Seed-based CaSCN analysis was firstly carried out to map the progressive and influential patterns of damage to thalamus-related structures. A novel technique for voxel-based CaSCN density (CaSCNd) analysis was further proposed, enabling for identifying the epicenter of structural brain damage during the disease process.

RESULTS

The thalamus-associated CaSCNs demonstrated different patterns of progressive damage in two types of generalized tonic-clonic seizures. In IGTCS, the structural damage was predominantly driven from the thalamus, and expanded to the cortex, while in SGTCS, the damage was predominantly driven from the cortex, and expanded to the thalamus through the basal ganglia. CaSCNd analysis revealed that the IGTCS had an out-effect epicenter in the thalamus, whereas the SGTCS had equipotent in- and out-effects in the thalamus, cortex, and basal ganglia.

CONCLUSION

CaSCN revealed distinct damage patterns in the two types of GTCS, featuring with measurement of structural brain damage from the accumulating effect over a relatively long time period. Our work provided evidence for understanding network impairment mechanism underlying different GTCSs.

To explore the potential mechanisms of cognitive impairment in children with MRI-negative pharmacoresistant epilepsy due to focal cortical dysplasia: A pilot study from gray matter structure view

Objectives

To investigate the characteristics of brain structure in children with focal cortical dysplasia (FCD)-induced pharmacoresistant epilepsy, and explore the potential mechanisms of cognitive impairment from the view of gray matter alteration.

Methods

25 pharmacoresistant pediatric patients with pathologically confirmed focal cortical dysplasia (FCD), and 25 gender-matched healthy controls were included in this study. 3.0T MRI data and intelligence tests using the Wechsler Intelligence Scale for Children-Forth Edition (WISC-IV) were generated for all subjects. Voxel-based morphometry (VBM)-diffeomorphic anatomical registration through exponentiated lie algebra (DARTEL) and surface-based morphometry (SBM) analyses were performed to analyze gray matter volume and cortical structure. Two-sample t-tests were used to compare the differences in gray matter volume (P＜0.05, FWE) and cortical thickness (P＜0.001, FWE) between the two groups. Also, the Spearman rank correlation analyses were employed to determine the relationship between structural alterations and neuropsychological results.

Results

The WISC-IV scores of the FCD group were significantly lower than those of the HC group in terms of full-scale intelligence quotient (FSIQ), verbal comprehension index (VCI), perceptual reasoning index (PRI), working memory index (WMI), and processing speed index (PSI) (all P＜0.01). Compared with the HC group, in the FCD group, the gray matter volume (GMV) reduced significantly in the left cerebellum_8, cerebellum_Crus2, and bilateral thalamus (P＜0.05, FWE); the GMV increased in the bilateral medial frontal gyrus, right precuneus, and left inferior temporal gyrus (P＜0.05, FWE), and the cortical thickness increased in the bilateral frontal, parietal, and temporal areas (P＜0.001, FWE). Correlation analyses showed that the age of seizure onset had positive correlations with the WISC-IV scores significantly. Meanwhile, the cortex thicknesses of the left pars opercularis gyrus, left middle temporal gyrus, and right inferior temporal gyrus had negative correlations with the WISC-IV scores significantly.

Conclusion

FCD patients showed subtle structural abnormalities in multiple brain regions, with significant involvement of the primary visual cortex and language function cortex. And we also demonstrated a crucial correlation between gray matter structural alteration and cognitive impairment.

Altered spontaneous brain activity as a potential imaging biomarker for generalized and focal to bilateral tonic-clonic seizures: A resting-state fMRI study

OBJECTIVE

We aimed to determine whether alterations in spontaneous regional brain activity in those with generalized tonic-clonic seizures (GTCS) and focal to bilateral tonic-clonic seizures (FBTCS) and explore whether the alterations could be used as biomarkers to classify disease subtypes through support vector machine analysis (SVM).

METHODS

The fractional amplitude of low-frequency fluctuations (fALFF) and regional homogeneity (ReHo) from resting-state functional magnetic resonance imaging (rs-fMRI) data were extracted from 57 patients with GTCS, 35 patients with FBTCS, and 50 age-matched and sex-matched normal controls (NCs) using the DPARSF 5.0 toolbox. Between-group comparisons were adjusted for covariates (age, sex, and equipment). Correlation analyses between imaging biomarkers and the frequency or duration of seizure activity were calculated using partial correlations. The differential imaging indicators, age, and sex were considered as the discriminative features in the SVM to evaluate classification performance.

RESULTS

The patients with GTCS showed lower fALFF values (voxel p < 0.001, cluster p < 0.05, Gaussian random field corrected, GRF corrected) in the right postcentral gyrus and precentral gyrus and lower ReHo values (GRF corrected) in the middle temporal gyrus than the NCs. The patients with FBTCS showed higher fALFF (GRF corrected) values in the right postcentral and precentral gyrus and higher ReHo (GRF corrected) values in the right postcentral gyrus. Both fALFF (GRF corrected) and ReHo (GRF corrected) values were lower in the right postcentral gyrus and precentral gyrus in the GTCS group than in the FBTCS group. In patients with FBTCS, fALFF values in the right postcentral and precentral gyrus were positively correlated with duration (r = 0.655, p = 0.008, Bonferroni corrected) in the low-duration group, and ReHo values in the right postcentral gyrus were positively correlated with frequency (r = 0.486, p = 0.022, uncorrected) in the low-frequency group. SVM results showed receiver operating characteristic curves of 0.89, 0.87, and 0.76 for the classification between GTCS and NC, between FBTCS and NC, and GTCS and FBTCS, respectively.

SIGNIFICANCE

This study detected alterations in fALFF and ReHo in the postcentral gyrus and precentral gyrus in patients with GTCS and FBTCS, which might contribute to understanding the pathogenesis, disease classification, and clinical targeted therapy.

Neurovascular coupling changes in patients with magnetic resonance imaging negative focal epilepsy

Brain neuron activity is closely related to cerebral blood flow (CBF) changes. Alterations in the regional homogeneity (ReHo) and CBF occur in patients with magnetic resonance imaging negative focal epilepsy (FEP-MRI^-). However, the coupling alterations of ReHo and CBF in FEP-MRI^- remain unclear. The study aims to explore neurovascular coupling alterations and their clinical implication in FEP-MRI^-. We collected resting-state magnetic resonance imaging (MRI) data from 31 healthy controls (HCs) and 48 patients with FEP-MRI^-,including three-dimensional (3D) T1-weighted imaging, 3D arterial spin labeling (ASL) imaging,and resting-state functional MRI (rs-fMRI). The CBF and ReHo values were calculated from the ASL and rs-fMRI data, respectively. The CBF/ReHo ratio per voxel and whole-brain CBF-ReHo coupling were compared between the two groups. Correlation analysis involved the CBF/ReHo ratio and clinical indicators in FEP-MRI^-. Patients with FEP-MRI^- showed significantly increased cross-subject CBF-ReHo and global cross-voxel CBF-ReHo coupling. The CBF/ReHo ratio was higher in the bilateral orbitofrontal gyrus, right parietal lobe, and right middle frontal gyrus of patients with FEP-MRI^-. Nevertheless, this ratio was lower in the bilateral supplementary motor areas, the left middle and posterior cingulate gyrus, and the right central sulcus cover. The CBF/ReHo ratio was markedly correlated with cognitive function, memory, intelligence, and epilepsy duration in the above abnormal brain regions. CBF/ReHo ratio may be useful as an indicator of neuropathological mechanisms. These results support the hypothesis that CBF/ReHo ratio relates to the neuropathological mechanisms of FEP-MRI^-. Furthermore, it offers new perspectives for studying the mechanisms of MRI-negative epilepsy.

Structural and functional changes in drug-naïve benign childhood epilepsy with centrotemporal spikes and their associated gene expression profiles

Benign epilepsy with centrotemporal spikes (BECTS) is a common pediatric epilepsy syndrome that has been widely reported to show abnormal brain structure and function. However, the genetic mechanisms underlying structural and functional changes remain largely unknown. Based on the structural and resting-state functional magnetic resonance imaging data of 22 drug-naïve children with BECTS and 33 healthy controls, we conducted voxel-based morphology (VBM) and fractional amplitude of low-frequency fluctuation (fALFF) analyses to compare cortical morphology and spontaneous brain activity between the 2 groups. In combination with the Allen Human Brain Atlas, transcriptome-neuroimaging spatial correlation analyses were applied to explore gene expression profiles associated with gray matter volume (GMV) and fALFF changes in BECTS. VBM analysis demonstrated significantly increased GMV in the right brainstem and right middle cingulate gyrus in BECTS. Moreover, children with BECTS exhibited significantly increased fALFF in left temporal pole, while decreased fALFF in right thalamus and left precuneus. These brain structural and functional alterations were closely related to behavioral and cognitive deficits, and the fALFF-linked gene expression profiles were enriched in voltage-gated ion channel and synaptic activity as well as neuron projection. Our findings suggest that brain morphological and functional abnormalities in children with BECTS involve complex polygenic genetic mechanisms.

Brain functional and structural characteristics of patients with seizure recurrence following drug withdrawal

PURPOSE

We aimed to analyze the characteristics of brain function and microstructure linked to epilepsy relapse after drug withdrawal in patients with focal epilepsy.

METHODS

Resting-state functional magnetic resonance imaging and high-resolution T1-weighted images were acquired within 1 month prior to drug withdrawal from 15 patients who did not have epilepsy relapse (PER - group) and 16 patients who subsequently had epilepsy relapse (PER + group). Additionally, 23 healthy participants undergoing the same scanning protocol were included as controls. Fractional amplitude of low-frequency fluctuation (fALFF) and gray matter density (GMD) were compared among groups. Subgroup and correlation analyses were also performed.

RESULTS

There were no significant differences in fALFF between patient groups, but the PER + group showed lower GMD in the bilateral calcarine, left precuneus, and right superior temporal gyrus than the PER - group (Gaussian random field correction, voxel-level P < 0.001 and cluster-level P < 0.05). Both increased seizure number and polytherapy were associated with lower GMD; also, patients using other antiseizure medications showed lower GMD than those using only levetiracetam (Gaussian random field correction, voxel-level P < 0.001, and cluster-level P < 0.05). The active period and disease duration showed both positive and negative correlations with GMD, while the seizure-free period mainly showed positive correlations with GMD (uncorrected, P < 0.001).

CONCLUSION

Gray matter microstructure, but not local functional activity, showed distinct characteristics between patients with and without epilepsy relapse and may serve as a potential biomarker for predicting seizure recurrence upon drug withdrawal.

Changes in resting-state cerebral blood flow and its connectivity in patients with focal to bilateral tonic-clonic seizures

Arterial spin labeling (ASL) is an important tool for understanding cerebral perfusion in epilepsy patients. The aim of this study was to explore patterns of change in cerebral blood flow (CBF) and CBF connectivity in patients with focal to bilateral tonic-clonic seizures (FBTCS). High-resolution three-dimensional (3-D) T1-weighted and 3-D pseudo-continuous ASL magnetic resonance imaging (MRI) was collected from 32 patients with FBTCS and 16 healthy volunteers using a 3.0 T MRI scanner. Cerebral blood flow and its connectivity were compared between the FBTCS and control group. Correlation analysis was used to explore relationships of CBF and its connectivity changes with clinical parameters. Cerebral blood flow data of spatial standardization and normalization were used to improve statistical power. Patients with FBTCS exhibited increased CBF in the bilateral thalamus, caudate nucleus, olfactory cortex, and gyrus rectus, but decreased CBF in the bilateral supplementary motor areas (SMA) and middle cingulate cortex (MCC). Patients with FBTCS showed significant positive correlation between CBF and gray matter volume (GMV) in bilateral SMA and MCC. No significant correlations between CBF and clinical parameters were found among FBTCS patients. The anterior cingulate cortex (ACC) showed positive CBF connectivity with the bilateral SMA and MCC, and these CBF connectivity measures differed significantly between groups (cluster-level, FWE-corrected, P < 0.001). These findings suggest that patients with FBTCS have changes in cerebral CBF and CBF connectivity, which may relate to the underlying neuropathology of FBTCS.