Temporal lobe epilepsy with or without hippocampal sclerosis: Structural and functional connectivity using advanced MRI techniques

Abstract

Background and Purpose The aim of this study was to investigate the differences in structural connectivity based on diffusion tensor imaging (DTI) and functional connectivity based on arterial spin labeling (ASL) MRI between temporal lobe epilepsy (TLE) patients with and without hippocampal sclerosis (HS). Methods We enrolled 50 patients with TLE, including 25 patients with HS and 25 patients without HS, who underwent brain MRI, including DTI and ASL. We calculated the network parameters of structural connectivity based on DTI and functional connectivity based on ASL using a graph theoretical analysis. The parameters included global network measures (radius, diameter, characteristic path length, global efficiency, local efficiency, mean clustering coefficient, transitivity, assortative coefficient, and small‐worldness index) and a local network measure (betweenness centrality). Results The global and local network measures of structural connectivity were not different between TLE patients with and without HS. However, significant differences in functional connectivity existed between the two groups. The radius and diameter of the global network measures in the TLE patients with HS were significantly increased compared with those without HS (4.140 vs. 3.140, p = 0.045; 6.812 vs. 5.132, p = 0.049; respectively). No differences were detected between other global network measures of functional connectivity and local network measure. Conclusions Significant differences in global network measures of functional connectivity based on ASL existed between TLE patients with and without HS. These findings suggest that TLE patients with HS exhibit a more disconnected functional brain network than those without HS.

Advanced neuroimaging techniques in epilepsy

“…Abnormalities of structural and functional connectivity were shown to be more marked closer to the presumed seizure onset zone, consistent with the findings of the ENIGMA study [15]. A consistent finding was that functional connectivity parameters were more abnormal in those with TLE and hippocampal sclerosis than those without hippocampal sclerosis [16].…”

“…There is the inevitable caveat that not every structural abnormality is causally related to epilepsy [2]. In a systematic review of 275 patients in 16 studies, the overall extra yield was 31%, with particular yield of focal cortical dysplasia, hippocampal sclerosis and gliosis [3 && ]. In general, T2Ã sequences gave good yield.…”

Episodic memory network connectivity in temporal lobe epilepsy

“…RTLE with HS compared to those without HS showed functional disruption with bilateral temporal cortices and left insula, areas previously associated with better memory performance. 11 In TLE due to HS, structural MRI showed thalamic connectivity 66 differences and functional imaging using arterial spin labeling 67 showed differences in global network measures compared to those without HS suggesting a more disconnected functional brain network in people with TLE due to HS. No memory functional connectivity studies to date have described the memory network differences in TLE with and without HS.…”

Topological Abnormalities of Pallido-Thalamo-Cortical Circuit in Functional Brain Network of Patients With Nonchemotherapy With Non-small Cell Lung Cancer

“…An assortative network has highly connected nodes, which improves network resilience and reduces disruption loss ( 73 , 74 ). Therefore, this type of network facilitates the spread of information over the network ( 75 ). The index of network synchronization reflects the possibility of all the nodes fluctuate in the same wave pattern ( 47 , 76 ).…”