1 Analytical Neurophysiology Lab, Montreal Neurological Institute and Hospital, McGill University, Montreal, Quebec, Canada; Multimodal Functional Imaging Lab, Biomedical Engineering Department, McGill University, Canada.
2 Multimodal Functional Imaging Lab, Biomedical Engineering Department, McGill University, Canada.
3 Montreal Neurological Institute and Hospital, McGill University, Montreal, Quebec, Canada.
4 Claudio Munari Epilepsy Center, Niguarda Hospital, Milan, Italy.
5 Department of Neuroscience (DINOGMI), University of Genoa, Italy; IRCCS, Child Neuropsychiatry Unit, Instituto Giannina Gaslini, Genoa, Italy.
6 Multimodal Functional Imaging Lab, Biomedical Engineering Department, McGill University, Canada; Montreal Neurological Institute and Hospital, McGill University, Montreal, Quebec, Canada; Multimodal Functional Imaging Lab, PERFORM Centre, Department of Physics, Concordia University, Montreal, QC, Canada.
7 Analytical Neurophysiology Lab, Montreal Neurological Institute and Hospital, McGill University, Montreal, Quebec, Canada; Department of Medicine, Queen's University, Kingston, ON, Canada. Electronic address: birgit.frauscher@mcgill.ca.

Fast oscillations >40 Hz localize the epileptogenic zone: An electrical source imaging study using high-density electroencephalography.

Clin Neurophysiol. 2020 Dec 22; 132(2):568-580

Authors: Avigdor T, Abdallah C, von Ellenrieder N, Hedrich T, Rubino A, Lo Russo G, Bernhardt B, Nobili L, Grova C, Frauscher B

Abstract

OBJECTIVE: Fast Oscillations (FO) >40 Hz are a promising biomarker of the epileptogenic zone (EZ). Evidence using scalp electroencephalography (EEG) remains scarce. We assessed if electrical source imaging of FO using 256-channel high-density EEG (HD-EEG) is useful for EZ identification.

METHODS: We analyzed HD-EEG recordings of 10 focal drug-resistant epilepsy patients with seizure-free postsurgical outcome. We marked FO candidate events at the time of epileptic spikes and verified them by screening for an isolated peak in the time-frequency plot. We performed electrical source imaging of spikes and FO within the Maximum Entropy of the Mean framework. Source localization maps were validated against the surgical cavity.

RESULTS: We identified FO in five out of 10 patients who had a superficial or intermediate deep generator. The maximum of the FO maps was localized inside the cavity in all patients (100%). Analysis with a reduced electrode coverage using the 10-10 and 10-20 system showed a decreased localization accuracy of 60% and 40% respectively.

CONCLUSIONS: FO recorded with HD-EEG localize the EZ. HD-EEG is better suited to detect and localize FO than conventional EEG approaches.

SIGNIFICANCE: This study acts as proof-of-concept that FO localization using 256-channel HD-EEG is a viable marker of the EZ.

PMID: 33450578 [PubMed - as supplied by publisher]