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Free keywords:
Connectivity; Eepilepsy; Graph theory; MRI; Temporal lobe
Abstract:
Temporal lobe epilepsy (TLE) is the most frequent drug-resistant epilepsy in adults and commonly associated with variable
degrees of mesiotemporal atrophy on magnetic resonance imaging (MRI). Analyses of inter-regional connectivity have unveiled
disruptions in large-scale cortico-cortical networks; little is known about the topological organization of the mesiotemporal
lobe, the limbic subnetwork central to the disorder. We generated covariance networks based on high-resolution MRI surface-
shape descriptors of the hippocampus, entorhinal cortex, and amygdala in 134 TLE patients and 45 age- and sex-matched
controls. Graph-theoretical analysis revealed increased path length and clustering in patients, suggesting a shift toward a more
regularized arrangement;
fi
ndings were reproducible after split-half assessment and across 2 parcellation schemes. Analysis of
inter-regional correlations and module participation showed increased within-structure covariance, but decreases between
structures, particularly with regards to the hippocampus and amygdala. While higher clustering possibly re
fl
ects topological
consequences of axonal sprouting, decreases in interstructure covariance may be aconsequence of disconnection within limbic
circuitry. Preoperative network parameters, specifically the segregation of the ipsilateral hippocampus, predicted long-term
seizure freedom after surgery.
