How fast does the brain recover after an epileptic seizure?

Abstract

The postictal state, an abnormal cerebral condition following a seizure until the return to the interictal baseline, is frequently overlooked, despite often exceeding ictal duration and significantly impacting patients' lives. This study analyzes stereo-EEG (SEEG) signal dynamics using permutation entropy to quantify recovery time (postictal alteration time - PAT) in focal epilepsy and its clinical correlations. The average PAT was 4.5 min, extending up to an hour and was highest in temporal epilepsy and hippocampal sclerosis. Correlating with age at seizure onset and at SEEG, PAT provides a solution for operationally defining the postictal state and guiding interventions.

Figure 1

Postictal state quantification in focal epilepsy. (A) Global complexity dynamics of cerebral electrical activity as measured by the stereo‐electroencephalography recording contacts and depicted after permutation entropy quantification. y axis – permutation entropy (PE) values, x axis – timeline in seconds. The vertical bars indicate the seizure onset, termination, and “come‐back point” (the point at which for 25 consecutive seconds the global PE value is in the 2SD interval of the preictal period). The interval between the seizure start and end is called “Ictal period,” and the interval between the seizure end and the “come‐back point” is the postictal alteration time (PAT). (B) Z‐scored global complexity dynamics in the postictal period as plotted from the global permutation entropy curves of all analyzed seizures and subgrouped according to the epileptogenic zone network (EZN). (C) Mean ± standard deviation of Z‐scored global complexity dynamics in the postictal period as plotted from the global permutation entropy curves of all analyzed seizures and subgrouped according to the EZN. (D) Comparison of the postictal alteration time in unilateral EZN versus bilateral EZN, unilateral left EZN versus unilateral right EZN, temporal versus extratemporal and between, temporal, frontal, parietal, and occipital seizures. (E) Percentage of seizures in which the postictal alteration time (PAT) was longer or shorter than the ictal duration (IC) according to the type of epileptogenic zone network. (F) Comparison of the postictal alteration time according to the histopathology exam result of the epilepsy surgery resection piece. FCD, focal cortical dysplasia; HS, hippocampal sclerosis; LEAT, long‐term epilepsy‐associated tumor. (G) Comparison of the postictal alteration time according to age groups.