TY - JOUR
T1 - The Concept of Effective Inflow
T2 - Application to Interictal Localization of the Epileptogenic Focus from iEEG
AU - Vlachos, Ioannis
AU - Krishnan, Balu
AU - Treiman, David M.
AU - Tsakalis, Konstantinos
AU - Kugiumtzis, Dimitris
AU - Iasemidis, Leon D.
N1 - Funding Information:
Manuscript received March 5, 2016; revised July 22, 2016 and October 20, 2016; accepted November 14, 2016. Date of publication December 1, 2016; date of current version August 18, 2017. This work was supported in part by the U.S. National Science Foundation under Grant ECCS-1102390 and in part by the Department of Defense under Grant PT090712. The majority of the iEEG data analyzed were generated by the support of NIH NS039687. Asterisk indicates corresponding author. ∗I. Vlachos is with the Mathematics and Statistics Program, Louisiana Tech University, Ruston, LA 71272 USA (e-mail: ivlachos@latech.edu). B. Krishnan is with Cleveland Clinic Epilepsy Center. D. M. Treiman is with the Laboratory for Translational Epilepsy Research, Barrow Neurological Institute. K. Tsakalis is with the Department of Electrical Engineering, Arizona State University. D. Kugiumtzis is with the Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki. L. D. Iasemidis is with the Biomedical Engineering Program, Louisiana Tech University. Digital Object Identifier 10.1109/TBME.2016.2633200
Publisher Copyright:
© 1964-2012 IEEE.
PY - 2017/9
Y1 - 2017/9
N2 - Goal: Accurate determination of the epileptogenic focus is of paramount diagnostic and therapeutic importance in epilepsy. The current gold standard for focus localization is from ictal (seizure) onset and thus requires the occurrence and recording of multiple typical seizures of a patient. Localization of the focus from seizure-free (interictal) periods remains a challenging problem, especially in the absence of interictal epileptiform activity. Methods: By exploring the concept of effective inflow, we developed a focus localization algorithm (FLA) based on directed connectivity between brain sites. Subsequently, using the measure of generalized partial directed coherence over a broad frequency band in FLA for the analysis of interictal periods from long-term (days) intracranial electroencephalographic signals, we identified the brain region that is the most frequent receiver of maximal effective inflow from other brain regions. Results: In six out of nine patients with temporal lobe epilepsy, the thus identified brain region was a statistically significant outlier (p < 0.01) and coincided with the clinically assessed epileptogenic focus. In the remaining three patients, the clinically assessed focus still exhibited the highest inflow, but it was not deemed an outlier (p > 0.01). Conclusions: These findings suggest that the epileptogenic focus is a region of intense influence from other regions interictally, possibly as a mechanism to keep it under control in seizure-free periods. Significance: The developed framework is expected to assist with the accurate epileptogenic focus localization, reduce hospital stay and healthcare cost, and provide guidance to treatment of epilepsy via resective surgery or neuromodulation.
AB - Goal: Accurate determination of the epileptogenic focus is of paramount diagnostic and therapeutic importance in epilepsy. The current gold standard for focus localization is from ictal (seizure) onset and thus requires the occurrence and recording of multiple typical seizures of a patient. Localization of the focus from seizure-free (interictal) periods remains a challenging problem, especially in the absence of interictal epileptiform activity. Methods: By exploring the concept of effective inflow, we developed a focus localization algorithm (FLA) based on directed connectivity between brain sites. Subsequently, using the measure of generalized partial directed coherence over a broad frequency band in FLA for the analysis of interictal periods from long-term (days) intracranial electroencephalographic signals, we identified the brain region that is the most frequent receiver of maximal effective inflow from other brain regions. Results: In six out of nine patients with temporal lobe epilepsy, the thus identified brain region was a statistically significant outlier (p < 0.01) and coincided with the clinically assessed epileptogenic focus. In the remaining three patients, the clinically assessed focus still exhibited the highest inflow, but it was not deemed an outlier (p > 0.01). Conclusions: These findings suggest that the epileptogenic focus is a region of intense influence from other regions interictally, possibly as a mechanism to keep it under control in seizure-free periods. Significance: The developed framework is expected to assist with the accurate epileptogenic focus localization, reduce hospital stay and healthcare cost, and provide guidance to treatment of epilepsy via resective surgery or neuromodulation.
KW - Epilepsy
KW - epileptogenic focus localization
KW - frequency-based connectivity analysis
KW - generalized partial directed coherence (GPDC)
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U2 - 10.1109/TBME.2016.2633200
DO - 10.1109/TBME.2016.2633200
M3 - Article
C2 - 28092511
AN - SCOPUS:85029863871
VL - 64
SP - 2241
EP - 2252
JO - IRE transactions on medical electronics
JF - IRE transactions on medical electronics
SN - 0018-9294
IS - 9
M1 - 7762148
ER -