White matter abnormalities in children and adolescents with temporal lobe epilepsy
ABSTRACT The widespread propagation of synchronized neuronal firing in seizure disorders may affect cortical and subcortical brain regions. Diffusion tensor imaging (DTI) can noninvasively quantify white matter integrity. The purpose of this study was to investigate the abnormal changes of white matter in children and adolescents with focal temporal lobe epilepsy (TLE) using DTI.
Eight patients with clinically diagnosed TLE and eight age- and sex-matched healthy controls were studied. DTI images were obtained with a 3-T magnetic resonance imaging scanner. The epileptic foci were localized with magnetoencephalography. Fractional anisotropy (FA), mean diffusivity (MD), parallel (λ(||)) and perpendicular (λ(⊥)) diffusivities in the genu of the corpus callosum, splenium of the corpus callosum (SCC), external capsule (EC), anterior limbs of the internal capsule (AIC), and the posterior limbs of the internal capsule (PIC) were calculated. The DTI parameters between patients and controls were statistically compared. Correlations of these DTI parameters of each selected structure with age of seizure onset and duration of epilepsy were analysed.
In comparison to controls, both patients' seizure ipsilateral and contralateral had significantly lower FA in the AIC; PIC and SCC and higher MD, λ(||) and λ(⊥) in the EC, AIC, PIC and SCC. The MD, λ(||) and λ(⊥) were significantly correlated with age of seizure onset in the EC and PIC. λ(||) was significantly correlated with the duration of epilepsy in the EC and PIC.
The results of the present study indicate that children and adolescents with TLE had significant abnormalities in the white matter in the hemisphere with seizure foci. Furthermore, these abnormalities may extend to the other brain hemisphere. The age of seizure onset and duration of epilepsy may be important factors in determining the extent of influence of children and adolescents TLE on white matter.
- SourceAvailable from: Ruibin Zhang
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- "Advances in the development and application of diffusion tensor imaging (DTI) have allowed for investigating the organization of human brain white matter (WM) (Hagmann et al., 2008; Iturria-Medina et al., 2008; Gong et al., 2009a). Numerous DTI studies of TLE have reported brain WM abnormalities in TLE according to DTI analysis, such as the external capsule, corpus callosum (Meng et al., 2010), fornix, cingulum (Concha et al., 2009), uncinate fasciculus, arcuate fasciculus (Lin et al., 2008), and inferior fronto-occipital fasciculus (McDonald et al., 2008a). Even though the widespread WM damage in TLE suggests disrupted structural integrity derived from a systemic disorder, few studies have investigated the disrupted WM organizations in TLE patients from a system level. "
ABSTRACT: Mesial temporal lobe epilepsy (mTLE) is the most common drug-refractory focal epilepsy in adults. Although previous functional and morphological studies have revealed the abnormalities in the brain networks of mTLE, the topological organization of the brain white matter (WM) networks in mTLE patients is still ambiguous. In this study, we constructed brain WM networks for 14 left mTLE patients and 22 age- and gender-matched normal controls using diffusion tensor tractography and estimated the alterations of network properties in the mTLE brain networks using graph theoretical analysis. We found that the networks for both the mTLE and the controls exhibited prominent small-world properties, suggesting a balanced topology of integration and segregation. However, the brain WM networks of mTLE showed significant increased characteristic path length but significant decreased global efficiency, which indicate disruption in the organization of the brain WM networks in mTLE. Moreover, we found significant between-group differences in the nodal properties in several brain regions, such as the left superior temporal gyrus, left hippocampus, the right occipital and right temporal cortices. The robustness analysis showed that the results were likely to be consistent for the networks constructed with different definitions of node and edge weight. Taken together, our findings may suggest an adverse effect of epileptic seizures on the organization of large-scale brain WM networks in mTLE.Neuroscience 09/2014; 279. DOI:10.1016/j.neuroscience.2014.08.040 · 3.33 Impact Factor
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- "Local ''macrostructural'' WM lesions have been shown not to be associated with cognitive impairment in chronic epilepsy (Jansen et al. 2008). Microstructural white matter abnormalities have also been found (Focke, Yogarajah, et al. 2008; Meng et al. 2010). Additionally, diffusion indices were found to be correlated with various cognitive scores (Riley et al. 2010). "
ABSTRACT: Patients with chronic epilepsy frequently display cognitive comorbidity and might have widespread network abnormalities outside the epileptic zone, which might affect a variety of cognitive functions and global intelligence. We aimed to study the role of white matter connectivity in cognitive comorbidity. Thirty-nine patients with nonsymptomatic localization-related epilepsy and varying degrees of cognitive impairment and 23 age-matched healthy controls were included. Whole brain white matter networks were constructed from fiber tractography. Weighted graph theoretical analysis was performed to study white matter network abnormalities associated with epilepsy and cognition. Patients with severe cognitive impairment showed lower clustering (a measure of brain network segregation) and higher path length (a measure of brain network integration) compared with the healthy controls and patients with little or no cognitive impairment, whereas whole brain white matter volume did not differ. Correlation analyses revealed that IQ and cognitive impairment were strongly associated with clustering and path lengths. This study revealed impaired white matter connectivity, associated with cognitive comorbidity in patients with chronic epilepsy. As whole brain white matter volumes were preserved in the patient group, our results suggest an important role for the network topology rather than volumetric changes, in epilepsy with cognitive decline.Cerebral Cortex 10/2011; 22(9):2139-47. DOI:10.1093/cercor/bhr298 · 8.67 Impact Factor
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ABSTRACT: Diffusion tensor imaging (DTI) is used increasingly to study white matter integrity in people with temporal lobe epilepsy (TLE). Most studies report fractional anisotropy (FA) decrease and mean diffusivity (MD) increase in multiple white matter regions. The disturbance of white matter integrity varies across studies and between regions. We aimed to obtain a more consistent estimate of white matter diffusion characteristics and relate these to the distance from the seizure focus. Studies comparing diffusion characteristics of people with epilepsy with those of healthy controls were systematically reviewed and quantified using random and mixed effects meta analysis. In addition to the overall meta-analysis, pooled FA and MD differences were determined per hemisphere and white matter category separately. We included 13 cross-sectional studies. The pooled FA difference for all white matter was -0.026 (95% confidence interval [CI] -0.033 to -0.019) and MD difference was 0.028 × 10(-3) mm(2)/s (95% CI 0.015-0.04). FA was reduced significantly in people with TLE compared with healthy controls in both ipsilateral (mean difference -0.03) and contralateral white matter (-0.02). MD was significantly increased ipsilaterally and contralaterally. MD differed significantly between white matter connected to the affected temporal lobe and remote white matter. The meta-analysis provides a better estimation of the true diffusion characteristics. White matter structural integrity in TLE is disturbed more severely in the ipsilateral than in the contralateral hemisphere, and tracts closely connected with the affected temporal lobe are most disturbed. The exact underlying mechanisms remain to be elucidated.Epilepsia 03/2012; 53(4):659-67. DOI:10.1111/j.1528-1167.2012.03426.x · 4.58 Impact Factor