Functional connectivity in patients with idiopathic generalized epilepsy - PubMed (original) (raw)

Functional connectivity in patients with idiopathic generalized epilepsy

Friederike Moeller et al. Epilepsia. 2011 Mar.

Abstract

Purpose: Idiopathic generalized epilepsy (IGE) is characterized by electroencephalography (EEG) recordings with generalized spike wave discharges (GSWDs) arising from normal background activity. Although GSWDs are the result of highly synchronized activity in the thalamocortical network, EEG without GSWDs is believed to represent normal brain activity. The aim of this study was to investigate whether thalamocortical interactions are altered even during GSWD-free EEG periods in patients with IGE.

Methods: A GSWD-related group analysis was performed in 12 IGE patients to define seeds in areas involved during GSWDs. EEG-functional magnetic resonance imaging (fMRI) datasets from 22 IGE patients without GSWDs during the investigation and 30 age-matched healthy controls were then selected to investigate functional connectivity in GSWD-related areas. Blood oxygen level dependent (BOLD) signal changes were extracted from seeds defined by the GSWD-related group analysis. The averaged time course within each seed was used to detect brain regions with BOLD signal correlated with the seed. Group differences between patients and controls were estimated.

Key findings: The GSWD-related group analysis showed BOLD activation in the thalamus, the frontomesial cortex, and the cerebellum and BOLD deactivation in default mode areas. For the connectivity analysis, eight seeds were placed bilaterally in the thalamus, mesial frontal cortex, precuneus, and cerebellum. The functional connectivity analysis of these seeds did not show clearly altered functional connectivity for patients versus controls.

Significance: The results underscore the paroxysmal nature of GSWDs: Although GSWDs are characterized by highly synchronized activity in the thalamocortical network, the functional connectivity in areas involved during GSWDs does not demonstrate abnormality in GSWD-free periods.

Wiley Periodicals, Inc. © 2011 International League Against Epilepsy.

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Figures

Figure 1

Figure 1

Results of the GSWD-related group analysis. Color-coded statistical t-score maps (corrected p < 0.05 for spatial extent) showing GSWD-related BOLD signal increases (coded in yellow and red) and decreases (coded in blue and white) in GSWD-related activations were detected in the thalamus, the mesial frontal cortex, and the cerebellum; decreases in BOLD signal were found in parietal areas and the precuneus. Epilepsia © ILAE

Figure 2

Figure 2

Group differences in seed-based connectivity between IGE patients and healthy controls. The seeds (shown in purple) are based on the GSWD-related group analysis (Fig. 1). Increased connectivity in IGE patients versus controls are displayed in yellow, decreased connectivity in IGE patients versus controls are shown in blue. t-maps are corrected p < 0.05 for spatial extent. Altered connectivity was found only for the left thalamic seed. Increased connectivity was detected in the white matter adjacent to the left lateral ventricle, and decreased connectivity was detected in the cerebellum in the nodule and right dentate nucleus adjacent to the fourth ventricle. Epilepsia © ILAE

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