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Ictal time-irreversible intracranial EEG signals as markers of the epileptogenic zone

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Schindler Kaspar, Rummel Christian, Andrzejak Ralph G., Goodfellow Marc, Zubler Frédéric, Abela Eugenio, Wiest Roland, Pollo Claudio, Steimer Andreas, Gast Heidemarie,
Project A Bayesian Inference Approach to Intracranial EEG Seizure Dynamics
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Original article (peer-reviewed)

Journal Clinical Neurophysiology
Volume (Issue) 127(9)
Page(s) 3051 - 3058
Title of proceedings Clinical Neurophysiology
DOI 10.1016/j.clinph.2016.07.001


OBJECTIVE: To show that time-irreversible EEG signals recorded with intracranial electrodes during seizures can serve as markers of the epileptogenic zone. METHODS: We use the recently developed method of mapping time series into directed horizontal graphs (dHVG). Each node of the dHVG represents a time point in the original intracranial EEG (iEEG) signal. Statistically significant differences between the distributions of the nodes' number of input and output connections are used to detect time-irreversible iEEG signals. RESULTS: In 31 of 32 seizure recordings we found time-irreversible iEEG signals. The maximally time-irreversible signals always occurred during seizures, with highest probability in the middle of the first seizure half. These signals spanned a large range of frequencies and amplitudes but were all characterized by saw-tooth like shaped components. Brain regions removed from patients who became post-surgically seizure-free generated significantly larger time-irreversibilities than regions removed from patients who still had seizures after surgery. CONCLUSIONS: Our results corroborate that ictal time-irreversible iEEG signals can indeed serve as markers of the epileptogenic zone and can be efficiently detected and quantified in a time-resolved manner by dHVG based methods. SIGNIFICANCE: Ictal time-irreversible EEG signals can help to improve pre-surgical evaluation in patients suffering from pharmaco-resistant epilepsies.