Impairments of Thalamic Nuclei in Idiopathic Generalized Epilepsy Revealed by a Study Combining Morphological and Functional Connectivity MRI

Abstract

ObjectiveNeuroimaging evidence suggested that the thalamic nuclei may play different roles in the progress of idiopathic generalized epilepsy (IGE). This study aimed to demonstrate the alterations in morphometry and functional connectivity in the thalamic nuclei in IGE.MethodsFifty-two patients with IGE characterized by generalized tonic-clonic seizures and 67 healthy controls were involved in the study. The three-dimensional high-resolution T1-weighted MRI data were acquired for voxel-based morphometry (VBM) analysis, and resting-state blood-oxygenation level functional MRI data were acquired for functional connectivity analysis. The thalamic nuclei of bilateral medial dorsal nucleus (MDN) and pulvinar, as detected with decreased gray matter volumes in patients with IGE through VBM analysis, were selected as seed regions for functional connectivity analysis.ResultsDifferent alteration patterns were found in functional connectivity of the thalamic nuclei with decreased gray matter volumes in IGE. Seeding at the MDN, decreased connectivity in the bilateral orbital frontal cortex, caudate nucleus, putamen and amygdala were found in the patients (P<0.05 with correction). However, seeding at the pulvinar, no significant alteration of functional connectivity was found in the patients (P<0.05 with correction).ConclusionsSome specific impairment of thalamic nuclei in IGE was identified using morphological and functional connectivity MRI approaches. These findings may strongly support the different involvement of the thalamocortical networks in IGE.

Identifying Corticothalamic Network Epicenters in Patients with Idiopathic Generalized Epilepsy

“…4 Wang et al 8 identified abnormal thalamic nuclei in a group of patients with IGE by morphologic analysis, which provided the foundation for seed-based functional connectivity analysis. This revealed decreased connectivity between the medial dorsal nucleus and bilateral orbital frontal cortices, caudate nucleus, putamen, and amygdala.…”

“…3,4 Hemodynamic changes associated with GSWDs have been consistently observed in the thalamus and default mode areas. 5 Recently, corticothalamic interactions in generalized epilepsy have been characterized by morphometric covariance, 6 functional and anatomic connectivity, 7,8 and causal influence. 9 In particular, corticothalamic connections (parcellated through probabilistic tractography) showed abnormal functional connectivity in juvenile myoclonic epilepsy.…”

“…In addition to corticothalamic involvement in the pathophysiology of IGE, increasing evidence underscores the importance of the striatal system. 7,8,30 The striatum exerts an inhibitory effect on motor systems, 35 and its interaction with the motor and premotor cortices enables the smooth execution of voluntary movements. 36 Decreased control over the highly excitable network may also underlie the behavioral symptoms of seizures such as myoclonic jerks.…”

The epileptogenic network: the relationship between resting state and pre-spike related perturbations

“…A recent study showed disrupted SN in relation to inter-ictal spikes in children with focal (temporal and extra-temporal) intractable epilepsy (Ibrahim et al, 2014). In addition, it has been observed that thalamic deactivation is associated with inter-ictal discharges in generalised epilepsy (Wang et al, 2012b).…”

Intracranial Volume Estimation and Graph Theoretical Analysis of Brain Functional Connectivity Networks

“…Consequently, the first aim of the current study focused on evaluating subsampling protocols for manual estimation of ICV in the following four different subject categories: control pediatrics, control adults, pediatrics with epilepsy and adults with Alzheimer's disease. The choice of these groups were based on the importance of the ICV measure as a critical normalization factor whether the study is based on AD (Jack, Knopman et al 2012;Jack Jr, Knopman et al 2013;Westman, Aguilar et al 2013;Zhou, Goryawala et al 2014) or on epilepsy (Whitwell, Crum et al 2001;Wang, Zhang et al 2012;Winston, Cardoso et al 2013;Germeyan, Kalikhman et al 2014). …”