Epileptic encephalopathy with continuous spikes and waves during slow sleep is an age-related disorder characterized by the presence of interictal epileptiform discharges during at least >85% of sleep and cognitive deficits associated with this electroencephalography pattern. The pathophysiological mechanisms of continuous spikes and waves during slow sleep and neuropsychological deficits associated with this condition are still poorly understood. Here, we investigated the haemodynamic changes associated with epileptic activity using simultaneous acquisitions of electroencephalography and functional magnetic resonance imaging in 12 children with symptomatic and cryptogenic continuous spikes and waves during slow sleep. We compared the results of magnetic resonance to electric source analysis carried out using a distributed linear inverse solution at two time points of the averaged epileptic spike. All patients demonstrated highly significant spike-related positive (activations) and negative (deactivations) blood oxygenation-level-dependent changes (P < 0.05, family-wise error corrected). The activations involved bilateral perisylvian region and cingulate gyrus in all cases, bilateral frontal cortex in five, bilateral parietal cortex in one and thalamus in five cases. Electrical source analysis demonstrated a similar involvement of the perisylvian brain regions in all patients, independent of the area of spike generation. The spike-related deactivations were found in structures of the default mode network (precuneus, parietal cortex and medial frontal cortex) in all patients and in caudate nucleus in four. Group analyses emphasized the described individual differences. Despite aetiological heterogeneity, patients with continuous spikes and waves during slow sleep were characterized by activation of the similar neuronal network: perisylvian region, insula and cingulate gyrus. Comparison with the electrical source analysis results suggests that the activations correspond to both initiation and propagation pathways. The deactivations in structures of the default mode network are consistent with the concept of epileptiform activity impacting on normal brain function by inducing repetitive interruptions of neurophysiological function.
SUMMARYPurpose: West syndrome is a severe epileptic encephalopathy of infancy characterized by a poor developmental outcome and hypsarrhythmia. The pathogenesis of hypsarrhythmia is insufficiently understood. Methods: We investigated eight patients with infantile spasms and hypsarrhythmia (group I) and 8 children with complex partial seizures (group II) using simultaneous recordings of electroencephalogram (EEG) and functional MRI. Hemodynamic responses to epileptiform discharges and slow wave activity (EEG delta power) were analyzed separately. Results: In group I (mean age, 7.82 ± 2.87 months), interictal spikes within the hypsarrhythmia were associated with positive blood oxygenation leveldependent (BOLD) changes in the cerebral cortex (especially occipital areas). This was comparable with cortical positive BOLD responses in group II (mean age, 20.75 ± 12.52 months). Slow wave activity in group I correlated significantly with BOLD signal in voxels, which were localized in brainstem, thalamus, as well as different cortical areas. There was no association between BOLD effect and EEG delta power in group II. Moreover, as revealed by group analysis, group I differed from group II according to correlations between BOLD signal and slow wave activity in putamen and brainstem. Conclusions: This study demonstrates that multifocal interictal spikes and high-amplitude slow wave activity within the hypsarrhythmia are associated with the activation of different neuronal networks. Although spikes caused a cortical activation pattern similar to that in focal epilepsies, slow wave activity produced a hypsarrhythmia-specific activation in cortex and subcortical structures such as brainstem, thalamus, and putamen. KEY WORDS: West syndromeHypsarrhythmia -EEG-fMRI-Blood oxygenation level-dependent (BOLD) responses-Occipital cortex-Basal ganglia.
SUMMARYAtypical benign partial epilepsy (ABPE) is a subgroup among the idiopathic focal epilepsies of childhood. Aim of this study was to investigate neuronal networks underlying ABPE and compare the results with previous electroencephalography (EEG)-functional magnetic resonance imaging (fMRI) studies of related epilepsy syndromes. Ten patients with ABPE underwent simultaneous EEG-fMRI recording. In all 10 patients several types of interictal epileptiform discharges (IEDs) were recorded. Individual IED-associated blood oxygen level-dependent (BOLD) signal changes were analyzed in a single subject analysis for each IED type (33 studies). A group analysis was also performed to determine common BOLD signal changes across the patients. IED-associated BOLD signal changes were found in 31 studies. Focal BOLD signal changes concordant with the spike field (21 studies) and distant cortical and subcortical BOLD signal changes (31 studies) were detected. The group analysis revealed a thalamic activation. This study demonstrated that ABPE is characterized by patterns similar to studies in rolandic epilepsy (focal BOLD signal changes in the spike field) as well as patterns observed in continuous spikes and waves during slow sleep (CSWS) (distant BOLD signal changes in cortical and subcortical structures), thereby underscoring that idiopathic focal epilepsies of childhood form a spectrum of overlapping syndromes.
Summary Purpose Dravet syndrome (DS) or severe myoclonic epilepsy of infancy is an intractable epileptic encephalopathy of early childhood that is caused by a mutation in the SCN1A gene in most patients. The aim of this study was to identify a syndrome‐specific epileptic network underlying interictal epileptiform discharges (IEDs) in patients with DS. Methods Ten patients with the diagnosis of DS associated with mutations in the SCN1A gene were investigated using simultaneous recording of electroencephalography and functional magnetic resonance imaging ((EEG‐fMRI). Time series of IEDs were used as regressors for the statistical fMRI analysis. Key Findings In nine patients with DS, individual blood oxygenation level–dependent (BOLD) signal changes were seen. In three patients the thalamus was involved. Furthermore, regions of the default mode network were activated in seven patients. However, a common activation pattern associated with IEDs could not be detected. Significance The study demonstrates that, despite a common genetic etiology in DS, different neuronal networks underlie the individual IEDs.
In addition to the thalamocortical network, which is commonly found in idiopathic generalized epilepsies, GSW in patients with MAE are characterized by BOLD signal changes in brain structures associated with motor function. The results are in line with animal studies demonstrating that somatosensory cortex, putamen, and cerebellum are involved in the generation of myoclonic seizures. The involvement of these structures might predispose to the typical seizure semiology of myoclonic jerks observed in MAE.
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