Abstract
BackgroundTemporal lobe epilepsy (TLE) is commonly refractory. Epilepsy surgery is an effective treatment strategy for refractory epilepsy, but patients with a history of focal to bilateral tonic-clonic seizures (FBTCS) have poor outcomes. Previous network studies on epilepsy have found that TLE and idiopathic generalized epilepsy with generalized tonic-clonic seizures (IGE-GTCS) showed altered global and nodal topological properties. Alertness deficits also were found in TLE. However, FBTCS is a common type of seizure in TLE, and the implications for alertness as well as the topological rearrangements associated with this seizure type are not well understood.MethodsWe obtained rs-fMRI data and collected the neuropsychological assessment data from 21 TLE patients with FBTCS (TLE- FBTCS), 18 TLE patients without FBTCS (TLE-non- FBTCS) and 22 controls, and constructed their respective functional brain networks. The topological properties were analyzed using the graph theoretical approach and correlations between altered topological properties and alertness were analyzed.ResultsWe found that TLE-FBTCS patients showed more serious impairment in alertness effect, intrinsic alertness and phasic alertness than the patients with TLE-non-FBTCS. They also showed significantly higher small-worldness, normalized clustering coefficient (γ) and a trend of higher global network efficiency (gE) compared to TLE-non-FBTCS patients. The gE showed a significant negative correlation with intrinsic alertness for TLE-non-FBTCS patients.ConclusionOur findings show different impairments in brain network information integration, segregation and alertness between the patients with TLE-FBTCS and TLE-non-FBTCS, demonstrating that impairments of the brain network may underlie the disruptions in alertness functions.
Highlights
Temporal lobe epilepsy (TLE) is commonly refractory
Demographic, clinical characteristic and alertness There were no significant differences in age, education years and gender levels between the TLE-focal to bilateral tonic-clonic seizures (FBTCS), TLEnon-FBTCS and healthy controls (HCs) groups
Altered global topology of functional network In our study, the results revealed that the brain functional networks for TLE-FBTCS, TLE-non-FBTCS, and HC showed a prominent small-world topological characteristic which was consistent with previous graph theoretical investigations on epilepsy [16, 17, 37]
Summary
Epilepsy surgery is an effective treatment strategy for refractory epilepsy, but patients with a history of focal to bilateral tonic-clonic seizures (FBTCS) have poor outcomes. Previous network studies on epilepsy have found that TLE and idiopathic generalized epilepsy with generalized tonic-clonic seizures (IGE-GTCS) showed altered global and nodal topological properties. A microstructural image study of patients without FBTCS found the integrity of the ipsilateral hippocampal-thalamic pathway impaired, whereas patients with FBTCS showed bilateral hippocampalthalamic pathway impairment. The patients with FBTCS exhibited greater impairment of the ipsilateral hippocampal-thalamic pathway than those without FBTCS [10]. In addition to the thalamus and hippocampus, the basal ganglia might take part in modulating generalized tonic-clonic seizures. More and more evidence suggest that basal ganglia, thalamus, hippocampus and cerebellum might play an important role in the propagation/control of TLE and modulation of FBTCS.
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