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FMRI study of mesial temporal lobe epilepsy using amplitude of low-frequency fluctuation analysis.

ABSTRACT: Various functional imaging tools have been used to detect epileptic activity in the neural network underlying mesial temporal lobe epilepsy (mTLE). In the present fMRI study, a data-driven approach was employed to map interictal epileptic activity in mTLE patients by measuring the amplitude of low-frequency fluctuation (ALFF) of the blood oxygen level-dependent (BOLD) signal. Twenty-four left mTLE patients and 26 right mTLE patients were investigated by comparing with 25 healthy subjects. In the patients, the regions showing increased ALFF were consistently distributed in the mesial temporal lobe, thalamus, and a few of other cortical and subcortical structures composing a mesial temporal epilepsy network proposed previously, while the regions showing decreased ALFF were mostly located in the areas of so-called default-mode network. Data of simultaneous EEG-fMRI from a portion of the patients suggested that the increases in ALFF might be associated with the interictal epileptic activity. Individual analyses based on statistic parametric mapping revealed a moderate sensitivity and a fairly high specificity for the lateralization of unilateral mTLE. We conclude that the ALFF analysis may provide a useful tool in fMRI study of epilepsy.

SUBMITTER: Zhang Z

PROVIDER: S-EPMC6870704 | biostudies-literature | 2010 Dec

REPOSITORIES: biostudies-literature

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fMRI study of mesial temporal lobe epilepsy using amplitude of low-frequency fluctuation analysis.

Zhang Zhiqiang Z Lu Guangming G Zhong Yuan Y Tan Qifu Q Chen Huafu H Liao Wei W Tian Lei L Li Zhihao Z Shi Jixin J Liu Yijun Y

Human brain mapping 20100311 12

Various functional imaging tools have been used to detect epileptic activity in the neural network underlying mesial temporal lobe epilepsy (mTLE). In the present fMRI study, a data-driven approach was employed to map interictal epileptic activity in mTLE patients by measuring the amplitude of low-frequency fluctuation (ALFF) of the blood oxygen level-dependent (BOLD) signal. Twenty-four left mTLE patients and 26 right mTLE patients were investigated by comparing with 25 healthy subjects. In the ...[more]

PMID: 20225278

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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.

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

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FMRI study of mesial temporal lobe epilepsy using amplitude of low-frequency fluctuation analysis.

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fMRI study of mesial temporal lobe epilepsy using amplitude of low-frequency fluctuation analysis.

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