Dataset Information

Default mode network abnormalities in mesial temporal lobe epilepsy: a study combining fMRI and DTI.

ABSTRACT: Studies of in mesial temporal lobe epilepsy (mTLE) patients with hippocampal sclerosis (HS) have reported reductions in both functional and structural connectivity between hippocampal structures and adjacent brain regions. However, little is known about the connectivity among the default mode network (DMN) in mTLE. Here, we hypothesized that both functional and structural connectivity within the DMN were disturbed in mTLE. To test this hypothesis, functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) were applied to examine the DMN connectivity of 20 mTLE patients, and 20 gender- and age-matched healthy controls. Combining these two techniques, we explored the changes in functional (temporal correlation coefficient derived from fMRI) and structural (path length and connection density derived from DTI tractography) connectivity of the DMN. Compared to the controls, we found that both functional and structural connectivity were significantly decreased between the posterior cingulate cortex (PCC)/precuneus (PCUN) and bilateral mesial temporal lobes (mTLs) in patients. No significant between-group difference was found between the PCC/PCUN and medial prefrontal cortex (mPFC). In addition, functional connectivity was found to be correlated with structural connectivity in two pairwise regions, namely between the PCC/PCUN and bilateral mTLs, respectively. Our results suggest that the decreased functional connectivity within the DMN in mTLE may be a consequence of the decreased connection density underpinning the degeneration of structural connectivity.

SUBMITTER: Liao W

PROVIDER: S-EPMC6870458 | biostudies-literature | 2011 Jun

REPOSITORIES: biostudies-literature

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Default mode network abnormalities in mesial temporal lobe epilepsy: a study combining fMRI and DTI.

Liao Wei W Zhang Zhiqiang Z Pan Zhengyong Z Mantini Dante D Ding Jurong J Duan Xujun X Luo Cheng C Wang Zhengge Z Tan Qifu Q Lu Guangming G Chen Huafu H

Human brain mapping 20100609 6

Studies of in mesial temporal lobe epilepsy (mTLE) patients with hippocampal sclerosis (HS) have reported reductions in both functional and structural connectivity between hippocampal structures and adjacent brain regions. However, little is known about the connectivity among the default mode network (DMN) in mTLE. Here, we hypothesized that both functional and structural connectivity within the DMN were disturbed in mTLE. To test this hypothesis, functional magnetic resonance imaging (fMRI) and ...[more]

PMID: 20533558

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Project description:The epilepsies represent one of the most common neurological disorders. Mesial temporal lobe epilepsies (MTLE) are the most frequent form of partial epilepsies and display frequent resistance to anti-epileptic drugs thus representing a major health care problem. In TLE, the origin of seizure activity typically involves the hippocampal formation, which displays major neuropathological features, described with the term hippocampal sclerosis (HS). HS is the most frequent pathological substrate of refractory mesial temporal lobe epilepsy. Complex partial seizures (CPS) are the predominant seizure type associated with medial temporal lobe epilepsy. MTLE is commonly due to mesial temporal sclerosis (MTS). The biology underlying the epilepstic seizures and the transcriptome associated to the seizure in intractable medial temporal lobe epilepsy is ill understood. The aim of the study was to identify potential biomarkers that could identify epileptic seizure. Thus we performed transcriptome profiling of ten medial temporal lobe epilepsy cases which are resistant to the drug and underwent temporal lobectomy. The cases constitutes of patients with intractable complex partial seizure, treated medically and have undergone detailed presurgical evaluation and subjected to surgery for standard temporal lobectomy and amygdalo-hippocampectomy. The spiking areas identified after the electrocorticography will form the test tissues, which compared with the nonspiking areas removed during the surgery, from the same patient. This could probably form one of the appropriate controls, as test and control are from same patient, which eliminates the genome variations that could incur due to the comparison with the tissues from the another patient. Also this could get rid of expression changes due to the treatments undergone by the patient. We performed two color microarray wherein we labled seizure focus (spiking area) with Cy5 and non-seizure region tissues (non-spiking) with Cy3. As a strategy to test the possibility of potential diagnostic biomarkers we are intended to test the differentially regulated molecules in an independent set of epilepsy samples. Two color experiment

Project description:OBJECTIVES:Brain functional topology was investigated in patients with mesial temporal lobe epilepsy (mTLE) by means of graph theory measures in two differentially defined graphs. Measures of segregation, integration, and centrality were compared between subjects with mTLE and healthy controls (HC). METHODS:Eleven subjects with mTLE (age 36.5±10.9years) and 15 age-matched HC (age 36.8±14.0years) participated in this study. Both anatomically and functionally defined adjacency matrices were used to investigate the measures. Binary undirected graphs were constructed to study network segregation by calculating global clustering and modularity, and network integration by calculating local and global efficiency. Node degree and participation coefficient were also computed in order to investigate network hubs and their classification into provincial or connector hubs. Measures were investigated in a range of low to medium graph density. RESULTS:The group of patients presented lower global segregation than HC while showing higher global but lower local integration. They also failed to engage regions that comprise the default-mode network (DMN) as hubs such as bilateral medial frontal regions, PCC/precuneus complex, and right inferior parietal lobule, which were present in controls. Furthermore, the cerebellum in subjects with mTLE seemed to be playing a major role in the integration of their functional networks, which was evident through the engagement of cerebellar regions as connector hubs. CONCLUSIONS:Functional networks in subjects with mTLE presented both global and local abnormalities compared to healthy subjects. Specifically, there was significant separation between groups, with lower global segregation and slightly higher global integration observed in patients. This could be indicative of a network that is working as a whole instead of in segregated or specialized communities, which could translate into a less robust network and more prone to disruption in the group with epilepsy. Furthermore, functional irregularities were also observed in the group of patients in terms of the engagement of cerebellar regions as hubs while failing to engage DMN-related areas as major hubs in the network. The use of two differentially defined graphs synergistically contributed to findings.

Dataset Information

Default mode network abnormalities in mesial temporal lobe epilepsy: a study combining fMRI and DTI.

Publications

Default mode network abnormalities in mesial temporal lobe epilepsy: a study combining fMRI and DTI.

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