Termination of seizure clusters is related to the duration of focal seizures

Abstract

SUMMARYObjective: Clustered seizures are characterized by shorter than usual interseizure intervals and pose increased morbidity risk. This study examines the characteristics of seizures that cluster, with special attention to the final seizure in a cluster. Methods: This is a retrospective analysis of long-term inpatient monitoring data from the EPILEPSIAE project. Patients underwent presurgical evaluation from 2002 to 2009. Seizure clusters were defined by the occurrence of at least two consecutive seizures with interseizure intervals of <4 h. Other definitions of seizure clustering were examined in a sensitivity analysis. Seizures were classified into three contextually defined groups: isolated seizures (not meeting clustering criteria), terminal seizure (last seizure in a cluster), and intracluster seizures (any other seizures within a cluster). Seizure characteristics were compared among the three groups in terms of duration, type (focal seizures remaining restricted to one hemisphere vs. evolving bilaterally), seizure origin, and localization concordance among pairs of consecutive seizures. Results: Among 92 subjects, 77 (83%) had at least one seizure cluster. The intracluster seizures were significantly shorter than the last seizure in a cluster (p = 0.011), whereas the last seizure in a cluster resembled the isolated seizures in terms of duration. Although focal only (unilateral), seizures were shorter than seizures that evolved bilaterally and there was no correlation between the seizure type and the seizure position in relation to a cluster (p = 0.762). Frontal and temporal lobe seizures were more likely to cluster compared with other localizations (p = 0.009). Seizure pairs that are part of a cluster were more likely to have a concordant origin than were isolated seizures. Results were similar for the 2 h definition of clustering, but not for the 8 h definition of clustering. Significance: We demonstrated that intracluster seizures are short relative to isolated seizures and terminal seizures. Frontal and temporal lobe seizures are more likely to cluster.

Bursts of seizures in long‐term recordings of human focal epilepsy

“…Ferastraoaru et al 4 reported that the duration of the last seizure within a cluster was longer, which suggested that a long seizure may be required to terminate ictal activity. We did not observe any significant difference between the last seizures in the burst compared to previous seizures.…”

“…A fundamental question is whether consecutive seizures occurring over a short window reflect a single epileptic process or multiple distinct events. One hypothesis is that multiple seizures occur when postictal inhibitory mechanisms do not prevail over the capacity for seizures to self‐trigger . In addition, it has also been suggested that there are seizure‐induced alterations that increase excitability, thereby promoting secondary attacks .…”

“…One hypothesis is that multiple seizures occur when postictal inhibitory mechanisms do not prevail over the capacity for seizures to selftrigger. 4 In addition, it has also been suggested that there are seizure-induced alterations that increase excitability, thereby promoting secondary attacks. 5 An alternative hypothesis is that interseizure intervals reflect scale-free dynamics, where there are correlations between intervals such that temporal clusters of seizures arise naturally.…”

Timing of seizure occurrence and response of medical staff in video-EEG monitoring for drug-resistant epilepsy

“…There were no previous studies in which all AEDs were discontinued before the VEEG admission. Interestingly, we and a number of other authors observed no complications related to discontinuation or dose reduction of AEDs [2,9,10,18,19,[21][22][23][24][25]. However, it is too early to conclude that we can discontinue all AEDs from our single series of VEEG monitoring.…”

“…Capturing one seizure may be enough to rule out non-epileptic seizures or to make a diagnosis of epilepsy, but is not regarded sufficient for presurgical evaluation. Many researchers have recommended that at least three seizures are required to properly locate the epileptic region [8,9,14,17,18]. Therefore, we investigated the times of occurrence of the first seizure and third seizure.…”