[When does post-ictal period start in temporal lobe epilepsy? A quantitative EEG perspective].

Area of Science:

• Neuroscience
• Epileptology
• Computational analysis

Background:

• Characterizing the post-ictal period in partial seizures using electroencephalography (EEG) is clinically challenging.
• Spectral and complex network analysis offer potential for precise definition of seizure phases and improved understanding of seizure dynamics.

Purpose of the Study:

• To investigate the utility of spectral and network analysis in defining the post-ictal period in temporal lobe epilepsy.
• To correlate EEG network properties with seizure termination and recovery phases.

Main Methods:

• Analysis of digital EEG recordings from 15 drug-resistant mesial temporal lobe epilepsy patients (32 seizures).
• Numerical analysis included spectral entropy, frequency bands, and network metrics (link density, modularity, cluster coefficient, average path length).
• Quantification of variations between post-ictal and pre-ictal periods.

Main Results:

• Cortical network link density increased during the post-ictal period of complex seizures.
• Spectral entropy decreased, primarily due to increased Delta band activity, during the post-ictal phase.
• These network changes peaked approximately one minute after seizure cessation.

Conclusions:

• An 'ending' mechanism, initiated during the ictal period and maximal in the post-ictal phase, explains the observed network changes.
• These findings suggest that the post-ictal period can be identified by maximal synchrony, characterized by high link density and low spectral entropy.
• This approach may aid in more accurately defining the start of the post-ictal period in epilepsy.