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Network Analysis of Foramen Ovale Electrode Recordings in Drug-resistant Temporal Lobe Epilepsy Patients
Published on: December 18, 2016
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Brain areas with epileptic high frequency oscillations are functionally isolated in MEG virtual electrode networks
Ida A Nissen1, Nicole E C van Klink2, Maeike Zijlmans3
1Department of Clinical Neurophysiology and MEG Center, Neuroscience Campus Amsterdam, VU University Medical Center, Postbus 7057, 1007 MB Amsterdam, The Netherlands.
Summary
The irritative zone in epilepsy, generating spikes and high-frequency oscillations, shows low network hub status. This suggests the irritative zone is functionally isolated within the epileptic network.
Area of Science:
- Neuroscience
- Epileptology
- Network Science
Background:
- Network hubs and epileptiform activity are linked to the epileptogenic zone.
- The irritative zone, generating interictal epileptiform activity, approximates the epileptogenic zone.
Purpose of the Study:
- To investigate the relationship between network hubs and the irritative zone in epilepsy.
- To understand the functional organization of the epileptic network during interictal periods.
Main Methods:
- Analysis of interictal resting-state MEG recordings from 12 epilepsy patients.
- Calculation of beamformer-based virtual electrodes around the irritative zone and in the contralateral hemisphere.
- Network analysis using minimum spanning tree and phase lag index (PLI) to determine betweenness centrality (hub status).
Main Results:
- Virtual electrodes near the irritative zone center exhibited low betweenness centrality and high PLI.
- Areas with high spike and high-frequency oscillation (HFO) counts showed low hub status.
- Node centrality increased with distance from brain areas exhibiting spikes and HFOs.
Conclusions:
- The irritative zone appears functionally isolated within the epileptic network during the interictal state.
- This finding supports a model where the core epileptic activity is segregated from major network hubs.
- A hypothesis of a remote pathological hub is proposed, potentially guiding surgical interventions.
