The Pre-Interictal Network State in Idiopathic Generalized Epilepsies.

Generalized spike wave discharges (GSWDs) are the typical electroencephalographic findings of Idiopathic Generalized Epilepsies (IGEs). These discharges are either interictal or ictal and recent evidence suggests differences in their pathogenesis. The aim of this study is to investigate, through functional connectivity analysis, the pre-interictal network state in IGEs, which precedes the formation of the interictal GSWDs. A high-density electroencephalogram (HD-EEG) was recorded in twenty-one patients with IGEs, and cortical connectivity was analyzed based on lagged coherence and individual anatomy. Graph theory analysis was used to estimate network features, assessed using the characteristic path length and clustering coefficient. The functional connectivity analysis identified two distinct networks during the pre-interictal state. These networks exhibited reversed connectivity attributes, reflecting synchronized activity at 3-4 Hz (delta2), and desynchronized activity at 8-10.5 Hz (alpha1). The delta2 network exhibited a statistically significant (p < 0.001) decrease in characteristic path length and an increase in the mean clustering coefficient. In contrast, the alpha1 network showed opposite trends in these features. The nodes influencing this state were primarily localized in the default mode network (DMN), dorsal attention network (DAN), visual network (VIS), and thalami. In conclusion, the coupling of two networks defined the pre-interictal state in IGEs. This state might be considered as a favorable condition for the generation of interictal GSWDs.

EEG Network Analysis in Epilepsy with Generalized Tonic-Clonic Seizures Alone.

Many contradictory theories regarding epileptogenesis in idiopathic generalized epilepsy have been proposed. This study aims to define the network that takes part in the formation of the spike-wave discharges in patients with generalized tonic-clonic seizures alone (GTCSa) and elucidate the network characteristics. Furthermore, we intend to define the most influential brain areas and clarify the connectivity pattern among them. The data were collected from 23 patients with GTCSa utilizing low-density electroencephalogram (EEG). The source localization of generalized spike-wave discharges (GSWDs) was conducted using the Standardized low-resolution brain electromagnetic tomography (sLORETA) methodology. Cortical connectivity was calculated utilizing the imaginary part of coherence. The network characteristics were investigated through small-world propensity and the integrated value of influence (IVI). Source localization analysis estimated that most sources of GSWDs were in the superior frontal gyrus and anterior cingulate. Graph theory analysis revealed that epileptic sources created a network that tended to be regularized during generalized spike-wave activity. The IVI analysis concluded that the most influential nodes were the left insular gyrus and the left inferior parietal gyrus at 3 and 4 Hz, respectively. In conclusion, some nodes acted mainly as generators of GSWDs and others as influential ones across the whole network.

Excessive supraventricular ectopic activity and future onset of atrial fibrillation in patients with cryptogenic stroke.

OBJECTIVES: Although evidence has shown the association of excessive supraventricular ectopic activity (ESVEA) with future development of atrial fibrillation (AF), this relationship is not yet fully understood. This study examines whether ESVEA can predict the future onset of AF, in patients presenting with cryptogenic stroke. MATERIALS AND METHODS: A retrospective cohort of 124 non-AF, consecutive patients, hospitalized for cryptogenic stroke between 2014 and 2015, was retrieved. 24-h inpatient monitoring with Holter was employed to reveal ESVEA, defined as the presence of more than 20 premature atrial complexes per hour (PACs/h) on average, or a more than 5 s duration of the longest supraventricular run (LSVR). After a median follow-up period of 5.2 years, the patients were examined for AF. RESULTS: From initial 124 patients, 12 died and one was lost during follow-up. For the total of 111 patients finally included, the median age was 56 years and 25.2% were females. The overall baseline median CHA2DS2-VASc score was 3. AF was found in 13 (11.71%) patients. Patients who were finally diagnosed with AF had a significantly higher number of PACs/h and a longer median LSVR duration at baseline (16.67 vs. 0.21, p < 0.001 and 3 vs. 0 s, p < 0.001, respectively). The presence of ESVEA was also significantly more frequent among AF patients (46.15%, 95%CI: 17.78%-74.22%) compared to non-AF ones (6.1%, 95%CI: 1.3%-10.7%, p < 0.001). CONCLUSIONS: Excessive atrial ectopy, detected with 24 h inpatient Holter monitoring, is a significant indicator of future development of AF in patients presenting originally with a cryptogenic stroke.