Source localization of high-frequency activity in tripolar electroencephalography of patients with epilepsy

Christopher Toole; Iris E Martinez-Juárez; John N Gaitanis; Andrew Blum; Sridhar Sunderam; Lei Ding; John DiCecco; Walter G Besio

doi:10.1016/j.yebeh.2019.106519

Source localization of high-frequency activity in tripolar electroencephalography of patients with epilepsy

Epilepsy Behav. 2019 Dec;101(Pt A):106519. doi: 10.1016/j.yebeh.2019.106519. Epub 2019 Nov 6.

Authors

Christopher Toole¹, Iris E Martinez-Juárez², John N Gaitanis³, Andrew Blum³, Sridhar Sunderam⁴, Lei Ding⁵, John DiCecco⁶, Walter G Besio⁷

Affiliations

¹ Interdisciplinary Neuroscience Program, University of Rhode Island, Kingston, RI, USA.
² Epilepsy Clinic and Clinical Epileptology Fellowship, National Autonomous University of Mexico and Mexico's National Institute of Neurology and Neurosurgery MVS, Mexico City, Mexico.
³ Rhode Island Hospital, Providence, RI, USA.
⁴ Department of Biomedical Engineering, University of Kentucky, Lexington, KY, USA.
⁵ Stephenson School of Biomedical Engineering, University of Oklahoma, Norman, OK, USA.
⁶ Interdisciplinary Neuroscience Program, University of Rhode Island, Kingston, RI, USA; Department of Electrical, Computer, and Biomedical Engineering, University of Rhode Island, Kingston, RI, USA.
⁷ Interdisciplinary Neuroscience Program, University of Rhode Island, Kingston, RI, USA; Department of Electrical, Computer, and Biomedical Engineering, University of Rhode Island, Kingston, RI, USA. Electronic address: besio@uri.edu.

PMID: 31706168
DOI: 10.1016/j.yebeh.2019.106519

Abstract

Objective: The objective of the study was to localize sources of interictal high-frequency activity (HFA), from tripolar electroencephalography (tEEG), in patient-specific, realistic head models.

Methods: Concurrent electroencephalogram (EEG) and tEEG were recorded from nine patients undergoing video-EEG, of which eight had seizures during the recordings and the other had epileptic activity. Patient-specific, realistic boundary element head models were generated from the patient's magnetic resonance images (MRIs). Forward and inverse modeling was performed to localize the HFA to cortical surfaces.

Results: In the present study, performed on nine patients with epilepsy, HFA observed in the tEEG was localized to the surface of subject-specific, realistic, cortical models, and found to occur almost exclusively in the seizure onset zone (SOZ)/irritative zone (IZ).

Significance: High-frequency oscillations (HFOs) have been studied as precise biomarkers of the SOZ in epilepsy and have resulted in good therapeutic effect in surgical candidates. Knowing where the sources of these highly focal events are located in the brain can help with diagnosis. High-frequency oscillations are not commonly observed in noninvasive EEG recordings, and invasive electrocorticography (ECoG) is usually required to detect them. However, tEEG, i.e., EEG recorded on the scalp with tripolar concentric ring electrodes (TCREs), has been found to detect narrowband HFA from high gamma (approximately 80 Hz) to almost 400 Hz that correlates with SOZ diagnosis. Thus, source localization of HFA in tEEG may help clinicians identify brain regions of the epileptic zone. At the least, the tEEG HFA localization may help determine where to perform intracranial recordings used for precise diagnosis.

Keywords: Electroencephalography; Epilepsy; High-frequency oscillations; Source localization; Tripolar concentric ring electrode.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Brain / diagnostic imaging
Brain / physiopathology*
Brain / surgery
Brain Mapping / methods
Electrocorticography
Electroencephalography
Epilepsy / diagnosis*
Epilepsy / diagnostic imaging
Epilepsy / physiopathology
Humans
Magnetic Resonance Imaging
Male
Middle Aged
Seizures / diagnosis*
Seizures / diagnostic imaging
Seizures / physiopathology