Abstracts

Rationale:
A major source of disability for people with epilepsy (PWE) involves uncertainty surrounding seizure timing and severity. Although PWE often report that long seizure-free intervals are followed by more severe seizures, there is little experimental evidence supporting this observation. Here, using chronic intracranial electroencephalography (cEEG), we investigate the relationship between interseizure interval (ISI) and duration of the subsequent seizure, a marker for severity.
Method:
We performed a retrospective analysis of 14 subjects implanted with a responsive neurostimulation device (RNS System) that provides cEEG, including timestamps of electrographic seizures. We determined seizure durations for isolated seizures and for representative seizures from clusters determined through unsupervised methods. For each subject, the median ISI preceding long-duration seizures, defined as the top quintile of seizure durations, was compared with the median ISI preceding seizures with durations in the residual quintiles. In a group analysis, the mean seizure duration and the proportion of long-duration seizures were compared across ISI categories representing different lengths.
Results:
For 5 out of 14 subjects (36%), the median ISI preceding long-duration seizures was significantly greater than the median ISI preceding short-duration seizures. In the group analysis, when ISI was grouped by length, the proportion of long-duration seizures within the high ISI category was significantly higher than that of the low ISI category (p< 0.001).
Conclusion:
By leveraging cEEG and accounting for seizure clusters, we found that the likelihood of long-duration seizures positively correlates with ISI length, in a subset of individuals. These findings corroborate anecdotal clinical observations and support the existence of capacitor-like long memory processes governing the dynamics of focal seizures.
Funding:
:CTSI TL1 Fellowship Grant