Differences in graph theory functional connectivity in left and right temporal lobe epilepsy

Chiang, Sharon; Stern, John M.; Engel, Jerome; Levin, Harvey S.; Haneef, Zulfi

doi:10.1016/j.eplepsyres.2014.09.023

Cited by 54 publications

(47 citation statements)

References 51 publications

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“…Differences based on TLE lateralization has previously been noted by us and others [10, 24, 45], and could suggest a possible difference in the pathophysiology of these conditions. It has been previously noted that there may be more prominent connectivity changes in left TLE compared to right TLE [10, 11, 46].…”

Section: Discussionsupporting

confidence: 59%

“…After registration to the MNI template image, functional connectivity was estimated between ten pairs of bilateral regions of interest of reported abnormality in TLE. These regions were chosen based on a priori knowledge, as these regions have consistently demonstrated both structural and functional changes in TLE, and included the anterior cingulate gyrus, caudate, fusiform gyrus, hippocampus, inferior orbitofrontal gyrus, insula, parahippocampus, posterior cingulate gyrus, superior temporal gyrus, and thalamus [23, 24]. The regions analyzed include regions identified consistently as having atrophy in patients with TLE [23] across different studies, and those that could be analyzed using the automated anatomic labeling (AAL) atlas.…”

Section: Methodsmentioning

confidence: 99%

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Functional connectivity homogeneity correlates with duration of temporal lobe epilepsy

Haneef

Chiang

Yeh

et al. 2015

Epilepsy & Behavior

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Temporal lobe epilepsy (TLE) often is associated with progressive changes to seizures, memory, and mood during its clinical course. However, the cerebral changes related to this progression are not well understood. Because the changes may be related to changes in brain networks, we used functional connectivity MRI (fcMRI) to determine whether brain network parameters relate to the duration of TLE. Graph theory based analysis of the sites of reported regions of TLE abnormality, was performed on resting state fMRI data in 48 subjects: 24 controls, 13 patients with left TLE, and 11 patients with right TLE. Various network parameters were analyzed including betweenness centrality (BC), clustering coefficient (CC), path length (PL), small-world index (SWI), global efficiency (GE), connectivity strength (CS), and connectivity diversity (CD). These were compared for TLE as a group, compared to controls, and for left and right TLE separately. Association of changes in network parameters with epilepsy duration was also evaluated. We found that CC, CS and CD were decreased in TLE, compared to control subjects. Analyzed according to epilepsy duration, TLE showed a progressive reduction in CD. In conclusion, we found that several network parameters were decreased in TLE compared to controls, which suggested reduced connectivity in TLE. Reduction in CD associated with epilepsy duration suggests a homogenization of connections over time in TLE, indicating a reduction of the normal repertoire of stronger and weaker connections to other brain regions.

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Section: Discussionsupporting

confidence: 59%

Section: Methodsmentioning

confidence: 99%

Functional connectivity homogeneity correlates with duration of temporal lobe epilepsy

Haneef

Chiang

Yeh

et al. 2015

Epilepsy & Behavior

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“…Due to distinct hemispheric organization, morphological and functional differences have been observed in left-sided TLE (LTLE) and right-sided TLE (RTLE)293031. If TLE is assumed to be a network disorder, then the question arises whether patients with RTLE and right-sided hippocampal sclerosis demonstrate different alterations of the connectome than patients with a left-sided one.…”

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confidence: 99%

“…If TLE is assumed to be a network disorder, then the question arises whether patients with RTLE and right-sided hippocampal sclerosis demonstrate different alterations of the connectome than patients with a left-sided one. Differences between patients with left- and right-sided hippocampal sclerosis are indicated by clinical symptomatology as well as in several imaging studies7831. Patients with LTLE demonstrate more severe deficits in verbal memory and language processing; patients with RTLE exhibit deficits in non-verbal, visual memory32.…”

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confidence: 99%

Insights into Intrinsic Brain Networks based on Graph Theory and PET in right- compared to left-sided Temporal Lobe Epilepsy

Vanicek

Hahn

Traub-Weidinger

et al. 2016

Sci Rep

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The human brain exhibits marked hemispheric differences, though it is not fully understood to what extent lateralization of the epileptic focus is relevant. Preoperative [18F]FDG-PET depicts lateralization of seizure focus in patients with temporal lobe epilepsy and reveals dysfunctional metabolic brain connectivity. The aim of the present study was to compare metabolic connectivity, inferred from inter-regional [18F]FDG PET uptake correlations, in right-sided (RTLE; n = 30) and left-sided TLE (LTLE; n = 32) with healthy controls (HC; n = 31) using graph theory based network analysis. Comparing LTLE and RTLE and patient groups separately to HC, we observed higher lobar connectivity weights in RTLE compared to LTLE for connections of the temporal and the parietal lobe of the contralateral hemisphere (CH). Moreover, especially in RTLE compared to LTLE higher local efficiency were found in the temporal cortices and other brain regions of the CH. The results of this investigation implicate altered metabolic networks in patients with TLE specific to the lateralization of seizure focus, and describe compensatory mechanisms especially in the CH of patients with RTLE. We propose that graph theoretical analysis of metabolic connectivity using [18F]FDG-PET offers an important additional modality to explore brain networks.

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“…This method has been also used to explore regions involved in the epileptogenic network in MTLE . A recent study by Chiang et al (2014) demonstrated reduced functional connectivity of the limbic structures ipsilateral to the presumed epileptic side, which was more pronounced in right TLE (Chiang et al, 2014). In left TLE, however, edge-wise and small-world topological changes were observed suggesting propensity towards re-organisation.…”

Section: Functional Connectivity Analysismentioning

confidence: 99%

The epileptogenic network: the relationship between resting state and pre-spike related perturbations

Faizo¹

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Mesial Temporal Lobe Epilepsy (MTLE) is the most common symptomatic focal epilepsy, with hippocampal sclerosis (HS) representing the most commonly occurring pathology linked to MTLE.In the past HS has been understood to represent a focal neuropathological alteration linked to the generation of seizures (i.e., the epileptic focus). However, the phenomenon that not all patients become seizure-free after surgical resection of the hippocampus has given rise to the concept that seizures and interictal epileptiform spikes and sharp waves (IES) captured by electroencephalography (EEG) in MTLE result from activity in a functionally connected epileptogenic network of brain regions. Large-scale network dynamics may thus be involved in the generation of IES and the temporal synchronisation of network structures may be an important factor in spike generation. Surgical outcome may be improved by broadening the focus from the identification of a single epileptogenic region to the characterisation of temporally synchronous epileptogenic networks associated with spikes.A common way to identify functional networks is to assess functional connectivity (FC) between spatially distinct brain regions. FC measures the degree of covariance between the activity in a specific brain region and other areas across the whole brain. The simultaneous acquisition of EEG and functional magnetic resonance imaging (fMRI) enables the identification of functional networks in which haemodynamic changes are time-locked to spikes. Nevertheless, whether this reflects the propagation of neural activity from a 'focus', or conversely the activation of a network linked to spike generation remains controversial. Delineation of functional connectivity patterns related to IES may be useful in shedding light on the mechanisms underlying their generation, and potentially of seizures in MTLE. Although the exact physiologic relationship between IES and seizures is not fully understood, there is a growing evidence to suggest that the neural network involved in generating IES is a reliable estimator of the network that generates seizures.My PhD aimed to explore the changes in brain network function that predispose the generation of IES using EEG-fMRI in patients with MTLE. I collected EEG-fMRI data from two groups of subjects: patients with MTLE and healthy controls. First, I examined MTLE patients to assess the presence of altered functional network connectivity identifiable immediately prior to the appearance of interictal spikes on EEG. A fundamental finding was the significant loss of bilateral hippocampal

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Differences in graph theory functional connectivity in left and right temporal lobe epilepsy

Cited by 54 publications

References 51 publications

Functional connectivity homogeneity correlates with duration of temporal lobe epilepsy

Functional connectivity homogeneity correlates with duration of temporal lobe epilepsy

Insights into Intrinsic Brain Networks based on Graph Theory and PET in right- compared to left-sided Temporal Lobe Epilepsy

The epileptogenic network: the relationship between resting state and pre-spike related perturbations

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