title: Functional connectivity homogeneity correlates with duration of temporal lobe epilepsy.
abstract: Temporal lobe epilepsy (TLE) is often 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 patients with TLE as a group, compared to controls, and for patients with left and right TLE separately. The association of changes in network parameters with epilepsy duration was also evaluated. We found that CC, CS, and CD decreased in subjects with TLE compared to control subjects. Analyzed according to epilepsy duration, patients with TLE showed a progressive reduction in CD. In conclusion, we found that several network parameters decreased in patients with 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.
authors: Department of Neurology, Baylor College of Medicine, Houston, TX, USA; Neurology Care Line, Michael E DeBakey VA Medical Center, Houston, TX, USA. Electronic address: haneef@bcm.edu.
authors: Zulfi
authors: Z
authors: Haneef
authors: Department of Statistics, Rice University, Houston, TX, USA.
authors: Sharon
authors: S
authors: Chiang
authors: Department of Neurology, University of California, Los Angeles, CA, USA.
authors: Hsiang J
authors: HJ
authors: Yeh
authors: Department of Neurology, University of California, Los Angeles, CA, USA; Department of Neurobiology, Department of Psychiatry and Biobehavioral Sciences, and the Brain Research Institute, University of California, Los Angeles, CA, USA.
authors: Jerome
authors: J
authors: Engel
authors: Department of Neurology, University of California, Los Angeles, CA, USA.
authors: John M
authors: JM
authors: Stern
mesh_terms: D000328:Adult; D063132:Connectome / Q000379:methods*; D004833:Epilepsy, Temporal Lobe / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008032:Limbic System / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009415:Nerve Net / Q000503:physiopathology*; D013997:Time Factors; D055815:Young Adult
keywords: Epileptic networks; Functional connectivity; Hippocampal networks; Progressive changes; Temporal lobe epilepsy (TLE); fMRI