Functional neuroimaging abnormalities in idiopathic generalized epilepsy

Abstract

Magnetic resonance imaging (MRI) techniques have been used to quantitatively assess focal and network abnormalities. Idiopathic generalized epilepsy (IGE) is characterized by bilateral synchronous spike–wave discharges on electroencephalography (EEG) but normal clinical MRI. Dysfunctions involving the neocortex, particularly the prefrontal cortex, and thalamus likely contribute to seizure activity. To identify possible morphometric and functional differences in the brains of IGE patients and normal controls, we employed measures of thalamic volumes, cortical thickness, gray–white blurring, fractional anisotropy (FA) measures from diffusion tensor imaging (DTI) and fractional amplitude of low frequency fluctuations (fALFF) in thalamic subregions from resting state functional MRI. Data from 27 patients with IGE and 27 age- and sex-matched controls showed similar thalamic volumes, cortical thickness and gray–white contrast. There were no differences in FA values on DTI in tracts connecting the thalamus and prefrontal cortex. Functional analysis revealed decreased fALFF in the prefrontal cortex (PFC) subregion of the thalamus in patients with IGE. We provide minimum detectable effect sizes for each measure used in the study. Our analysis indicates that fMRI-based methods are more sensitive than quantitative structural techniques for characterizing brain abnormalities in IGE.

A diffusional kurtosis imaging study of idiopathic generalized epilepsy with unilateral interictal epileptiform discharges in children

“…Routine magnetic resonance imaging (MRI) is normal in IGE individuals [2]. However, quantitative neuroimaging methods have identified several regional abnormalities [3,4].…”

Towards prognostic biomarkers from BOLD fluctuations to differentiate a first epileptic seizure from new‐onset epilepsy

“…In this study, NOE patients also showed significantly elevated fALFF in all the subcortical and cortical brain regions for the slow‐3 subband relative to healthy controls. This observation includes the default mode network areas, which corresponds to the effects previously reported on idiopathic generalized epilepsy using the fALFF measure …”

“…An anatomic atlas that divides the brain into 70 regions based on the gyri and sulci was calculated . A number of studies using fMRI on epilepsy motivated us to define the regions of interest (ROIs), including the thalamus, hippocampus, temporal cortex, prefrontal cortex, precentral cortex, postcentral cortex, posterior cingulate cortex, inferior parietal cortex, precuneus, and occipital cortex …”

“…Several methods have been developed to examine the amplitudes of low‐frequency oscillations . In the current study, we use the fractional amplitude of low‐frequency fluctuations (fALFFs) as a measure of the strength of the low‐frequency oscillations, which is the ratio of the power spectrum of low‐frequency signals to that of the entire frequency range …”

“…19,20 In the current study, we use the fractional amplitude of low-frequency fluctuations (fALFFs) as a measure of the strength of the low-frequency oscillations, which is the ratio of the power spectrum of low-frequency signals to that of the entire frequency range. 9,18,21 In this study, we evaluated ReHo and fALFFs in restingstate functional MRI (fMRI) signals of subjects with a first seizure, patients diagnosed with new-onset epilepsy (NOE), and healthy controls as reference. The objective of the comparison is to determine whether these measures can differentiate subjects who had a first seizure from patients with NOE, which might eventually lead to biomarkers that are sensitive to seizure recurrence.…”