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Ictal-onset localization through connectivity analysis of intracranial EEG signals in patients with refractory epilepsy

Pieter van Mierlo (UGent) , Evelien Carrette (UGent) , Hans Hallez (UGent) , Robrecht Raedt (UGent) , Alfred Meurs (UGent) , Stefaan Vandenberghe (UGent) , Dirk Van Roost (UGent) , Paul Boon (UGent) , Steven Staelens (UGent) and Kristl Vonck (UGent)
(2013) EPILEPSIA. 54(8). p.1409-1418
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Abstract
Purpose: Fifteen percent to 25% of patients with refractory epilepsy require invasive video-electroencephalography (EEG) monitoring (IVEM) to precisely delineate the ictal-onset zone. This delineation based on the recorded intracranial EEG (iEEG) signals occurs visually by the epileptologist and is therefore prone to human mistakes. The purpose of this study is to investigate whether effective connectivity analysis of intracranially recorded EEG during seizures provides an objective method to localize the ictal-onset zone. Methods: In this study data were analyzed from eight patients who underwent IVEM at Ghent University Hospital in Belgium. All patients had a focal ictal onset and were seizure-free following resective surgery. The effective connectivity pattern was calculated during the first 20s of ictal rhythmic iEEG activity. The out-degree, which is reflective of the number of outgoing connections, was calculated for each electrode contact for every single seizure during these 20s. The seizure specific out-degrees were summed per patient to obtain the total out-degree. The electrode contact with the highest total out-degree was considered indicative of localization of the ictal-onset zone. This result was compared to the conclusion of the visual analysis of the epileptologist and the resected brain region segmented from postoperative magnetic resonance imaging (MRI). Key findings: In all eight patients the electrode contact with the highest total out-degree was among the contacts identified by the epileptologist as the ictal onset. This contact, that we named the driver, always laid within the resected brain region. Furthermore, the patient-specific connectivity patterns were consistent over the majority of seizures. Significance: In this study we demonstrated the feasibility of correctly localizing the ictal-onset zone from iEEG recordings by using effective connectivity analysis during the first 20s of ictal rhythmic iEEG activity.
Keywords
EPILEPTOGENIC NETWORKS, PRESURGICAL EVALUATION, SEIZURE ONSET, DIRECTED TRANSFER-FUNCTION, TEMPORAL-LOBE EPILEPSY, Connectivity, Ictal-onset zone localization, Intracranial EEG, TIME, IDENTIFICATION, COHERENCE, SURGERY, PROPAGATION

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MLA
van Mierlo, Pieter, et al. “Ictal-Onset Localization through Connectivity Analysis of Intracranial EEG Signals in Patients with Refractory Epilepsy.” EPILEPSIA, vol. 54, no. 8, 2013, pp. 1409–18, doi:10.1111/epi.12206.
APA
van Mierlo, P., Carrette, E., Hallez, H., Raedt, R., Meurs, A., Vandenberghe, S., … Vonck, K. (2013). Ictal-onset localization through connectivity analysis of intracranial EEG signals in patients with refractory epilepsy. EPILEPSIA, 54(8), 1409–1418. https://doi.org/10.1111/epi.12206
Chicago author-date
Mierlo, Pieter van, Evelien Carrette, Hans Hallez, Robrecht Raedt, Alfred Meurs, Stefaan Vandenberghe, Dirk Van Roost, Paul Boon, Steven Staelens, and Kristl Vonck. 2013. “Ictal-Onset Localization through Connectivity Analysis of Intracranial EEG Signals in Patients with Refractory Epilepsy.” EPILEPSIA 54 (8): 1409–18. https://doi.org/10.1111/epi.12206.
Chicago author-date (all authors)
van Mierlo, Pieter, Evelien Carrette, Hans Hallez, Robrecht Raedt, Alfred Meurs, Stefaan Vandenberghe, Dirk Van Roost, Paul Boon, Steven Staelens, and Kristl Vonck. 2013. “Ictal-Onset Localization through Connectivity Analysis of Intracranial EEG Signals in Patients with Refractory Epilepsy.” EPILEPSIA 54 (8): 1409–1418. doi:10.1111/epi.12206.
Vancouver
1.
van Mierlo P, Carrette E, Hallez H, Raedt R, Meurs A, Vandenberghe S, et al. Ictal-onset localization through connectivity analysis of intracranial EEG signals in patients with refractory epilepsy. EPILEPSIA. 2013;54(8):1409–18.
IEEE
[1]
P. van Mierlo et al., “Ictal-onset localization through connectivity analysis of intracranial EEG signals in patients with refractory epilepsy,” EPILEPSIA, vol. 54, no. 8, pp. 1409–1418, 2013.
@article{3231722,
  abstract     = {{Purpose: Fifteen percent to 25% of patients with refractory epilepsy require invasive video-electroencephalography (EEG) monitoring (IVEM) to precisely delineate the ictal-onset zone. This delineation based on the recorded intracranial EEG (iEEG) signals occurs visually by the epileptologist and is therefore prone to human mistakes. The purpose of this study is to investigate whether effective connectivity analysis of intracranially recorded EEG during seizures provides an objective method to localize the ictal-onset zone.
Methods: In this study data were analyzed from eight patients who underwent IVEM at Ghent University Hospital in Belgium. All patients had a focal ictal onset and were seizure-free following resective surgery. The effective connectivity pattern was calculated during the first 20s of ictal rhythmic iEEG activity. The out-degree, which is reflective of the number of outgoing connections, was calculated for each electrode contact for every single seizure during these 20s. The seizure specific out-degrees were summed per patient to obtain the total out-degree. The electrode contact with the highest total out-degree was considered indicative of localization of the ictal-onset zone. This result was compared to the conclusion of the visual analysis of the epileptologist and the resected brain region segmented from postoperative magnetic resonance imaging (MRI).
Key findings: In all eight patients the electrode contact with the highest total out-degree was among the contacts identified by the epileptologist as the ictal onset. This contact, that we named the driver, always laid within the resected brain region. Furthermore, the patient-specific connectivity patterns were consistent over the majority of seizures.
Significance: In this study we demonstrated the feasibility of correctly localizing the ictal-onset zone from iEEG recordings by using effective connectivity analysis during the first 20s of ictal rhythmic iEEG activity.}},
  author       = {{van Mierlo, Pieter and Carrette, Evelien and Hallez, Hans and Raedt, Robrecht and Meurs, Alfred and Vandenberghe, Stefaan and Van Roost, Dirk and Boon, Paul and Staelens, Steven and Vonck, Kristl}},
  issn         = {{0013-9580}},
  journal      = {{EPILEPSIA}},
  keywords     = {{EPILEPTOGENIC NETWORKS,PRESURGICAL EVALUATION,SEIZURE ONSET,DIRECTED TRANSFER-FUNCTION,TEMPORAL-LOBE EPILEPSY,Connectivity,Ictal-onset zone localization,Intracranial EEG,TIME,IDENTIFICATION,COHERENCE,SURGERY,PROPAGATION}},
  language     = {{eng}},
  number       = {{8}},
  pages        = {{1409--1418}},
  title        = {{Ictal-onset localization through connectivity analysis of intracranial EEG signals in patients with refractory epilepsy}},
  url          = {{http://doi.org/10.1111/epi.12206}},
  volume       = {{54}},
  year         = {{2013}},
}

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