Dynamics of convulsive seizure termination and postictal generalized EEG suppression

Abstract

It is not fully understood how seizures terminate and why some seizures are followed by a period of complete brain activity suppression, postictal generalized EEG suppression. This is clinically relevant as there is a potential association between postictal generalized EEG suppression, cardiorespiratory arrest and sudden death following a seizure. We combined human encephalographic seizure data with data of a computational model of seizures to elucidate the neuronal network dynamics underlying seizure termination and the postictal generalized EEG suppression state. A multi-unit computational neural mass model of epileptic seizure termination and postictal recovery was developed. The model provided three predictions that were validated in EEG recordings of 48 convulsive seizures from 48 subjects with refractory focal epilepsy (20 females, age range 15-61 years). The duration of ictal and postictal generalized EEG suppression periods in human EEG followed a gamma probability distribution indicative of a deterministic process (shape parameter 2.6 and 1.5, respectively) as predicted by the model. In the model and in humans, the time between two clonic bursts increased exponentially from the start of the clonic phase of the seizure. The terminal interclonic interval, calculated using the projected terminal value of the log-linear fit of the clonic frequency decrease was correlated with the presence and duration of postictal suppression. The projected terminal interclonic interval explained 41% of the variation in postictal generalized EEG suppression duration (P < 0.02). Conversely, postictal generalized EEG suppression duration explained 34% of the variation in the last interclonic interval duration. Our findings suggest that postictal generalized EEG suppression is a separate brain state and that seizure termination is a plastic and autonomous process, reflected in increased duration of interclonic intervals that determine the duration of postictal generalized EEG suppression.

Low-to-High Cross-Frequency Coupling in the Electrical Rhythms as Biomarker for Hyperexcitable Neuroglial Networks of the Brain

“…7). Following the work of Bauer et al [40], we also used the data to obtain a gamma distribution fit which showed that short SED durations had a distribution with α > 1 (6.3, Confidence Interval: 5.3-7.4), which is consistent with the analysis done in [35] on the in vivo data. Long SED durations had a gamma distribution with (Fig.…”

Postictal suppression and seizure durations: A patient‐specific, long‐term iEEG analysis

“…Mathematical modeling of postictal suppression suggests a deterministic process associated with longer interclonic intervals and reduced connectivity prior to seizure termination. 5 This agrees with the hypothesis that seizures follow a set pathway through brain states. 4,6 The postictal period is commonly characterized by a period of low energy that slowly returns to interictal norms (referred to here as postictal suppression).…”

“…Critical transition models assume that seizure onsets and offsets may not begin and end entirely as a result of random fluctuations in cortical activity or input, but rather that seizures follow a path that must be completed as the brain transitions to the interictal state. Mathematical modeling of postictal suppression suggests a deterministic process associated with longer interclonic intervals and reduced connectivity prior to seizure termination . This agrees with the hypothesis that seizures follow a set pathway through brain states…”

“…The postictal period is commonly characterized by a period of low energy that slowly returns to interictal norms (referred to here as postictal suppression) . Postictal suppression is often associated with specific clinical features such as immobility, impaired cognition, headache, and psychological depression .…”

“…4,6 The postictal period is commonly characterized by a period of low energy that slowly returns to interictal norms (referred to here as postictal suppression). 5,[7][8][9] Postictal suppression is often associated with specific clinical features such as immobility, impaired cognition, headache, and psychological depression. [10][11][12] There is a contentious link between postictal generalized suppression (PGES) and sudden unexpected death in epilepsy (SUDEP).…”