Detecting Functional Hubs of Ictogenic Networks

Authors: Frederic Zubler Heidemarie Gast Eugenio Abela Christian Rummel Martinus Hauf Roland Wiest Claudio Pollo Kaspar Schindler

Publish Date: 2014/05/21

Volume: 28, Issue: 2, Pages: 305-317

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Abstract

Quantitative EEG qEEG has modified our understanding of epileptic seizures shifting our view from the traditionally accepted hypersynchrony paradigm toward more complex models based on reorganization of functional networks However qEEG measurements are so far rarely considered during the clinical decisionmaking process To better understand the dynamics of intracranial EEG signals we examine a functional network derived from the quantification of information flow between intracranial EEG signals Using transfer entropy we analyzed 198 seizures from 27 patients undergoing presurgical evaluation for pharmacoresistant epilepsy During each seizure we considered for each network the in out and total “hubs” defined respectively as the time and the EEG channels with the maximal incoming outgoing or total bidirectional information flow In the majority of cases we found that the hubs occur around the middle of seizures and interestingly not at the beginning or end where the most dramatic EEG signal changes are found by visual inspection For the patients who then underwent surgery good postoperative clinical outcome was on average associated with a higher percentage of out or totalhubs located in the resected area for outhubs p = 001 for totalhubs p = 004 The location of inhubs showed no clear predictive value We conclude that the study of functional networks based on qEEG measurements may help to identify brain areas that are critical for seizure generation and are thus potential targets for focused therapeutic interventions

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