Altered structural and functional thalamocortical networks in secondarily generalized extratemporal lobe seizures

Abstract

Structural and functional abnormalities in the thalamocortical network in primary generalized epilepsies or mesial temporal lobe epilepsy have recently been identified by voxel-wise analyses of neuroimaging. However, evidence is needed regarding the profiles of the thalamocortical network in patients with secondarily generalized seizures from focal neocortical sources. We used high-resolution T1-weighted, diffusion-tensor and resting-state functional MR imaging (rs-fMRI) to examine 16 patients with secondarily generalized extratemporal lobe seizures and 16 healthy controls. All the patients were medically effective and MRI-negative. Using whole brain voxel-based morphometry (VBM) to compare the patients with the normal controls, we observed significantly decreased gray matter (GM) density in the thalamus and 3 frontal gyri and significantly reduced white matter (WM) fractional anisotropy (FA) in the bilateral anterior corona radiata of the patients. Alterations in the thalamocortical functional connectivity with different cortices were identified by the rs-fMRI analysis seeding of the whole thalamus. The prefrontal gyri with the greatest functional connectivity were also traced by seeding a sub-thalamic region that is demarcated in an atlas, in which the thalamic parcellation is based on the WM connectivity to the cortices. This sub-thalamic region anatomically contains the mediodorsal thalamic nucleus where, concordantly, there was a significant decrease in thalamic GM density in the VBM study. In contrast to the negative correlation between the disease duration and reduced thalamic densities and subcortical FA values, the strength of the functional thalamocortical connectivity had a paradoxical correlation. Our results conclusively indicate that generalized seizures with a focal cortical source are associated with structural and functional alterations in the thalamocortical network.

Presurgical thalamocortical connectivity is associated with response to vagus nerve stimulation in children with intractable epilepsy

“…At the behavioural level, it has been suggested in a large systematic review of the literature that patients with generalized seizure semiologies are more likely to become seizure-free with VNS ( Englot et al, 2016 ). Various functional neuroimaging studies ( Ibrahim et al, 2014a , Peng and Hsin, 2017 ), as well as electrophysiological investigations ( Wolf and Beniczky, 2014 ) have conclusively implicated distinct thalamocortical circuitry in the generalization of seizure activities, including those related to the cingulate and insular cortices ( Peng and Hsin, 2017 ). Our findings provide a putative connectomics-informed explanation of clinical observations in this patient population.…”

Polygenic risk for five psychiatric disorders and cross-disorder and disorder-specific neural connectivity in two independent populations

“…In our study, the voxel-wise statistical results were corrected for multiple comparisons using the “AlphaSim” implemented in REST, based on the Monte Carlo simulation in AFNI ( Song et al, 2011 ). The AlphaSim algorithm implemented in REST is widely used to correct multiple comparisons in previous studies ( Fan et al, 2017 , Peng and Hsin, 2017 ). Since the subjects in our research were all healthy individuals, their differences may not have been significant enough to survive a more stringent correction.…”

Juvenile myoclonic epilepsy has hyper dynamic functional connectivity in the dorsolateral frontal cortex

“…In the last two decades resting-state functional magnetic resonance imaging (resting-state functional MRI) has emerged as a useful method to identify the neuropathological signatures for different subtypes of epilepsy ( Centeno and Carmichael, 2014 ; Chen et al, 2017 ; Gupta et al, 2017 ; Paldino et al, 2017 ; Peng and Hsin, 2017 ; Wang et al, 2017 ). For example, alterations in the default mode network (DMN) and thalamus were detected in childhood absence epilepsy ( Wang et al, 2017 ); The thalamus was shown to be impacted in patients suffering from generalized temporal lobe epilepsy ( Peng and Hsin, 2017 ), while the basal ganglia was strongly implicated in frontal lobe epilepsy ( Dong et al, 2016a , Dong et al, 2016b ). For patients with juvenile myoclonic epilepsy (JME) functional connectivity disturbances in both the thalamo-motor and thalamo-frontal networks were found ( Dong et al, 2016b ; Jiang et al, 2018 ).…”