Accuracy and spatial properties of distributed magnetic source imaging (dMSI) techniques in the investigation of focal epilepsy patients

Pellegrino, Giovanni; Hedrich, Tanguy; Porras-Bettancourt, Manuel; Lina, Jean‐Marc; Grova, Christophe; Kobayashi, Eliane

doi:10.1016/j.clinph.2019.03.019

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“…Final maps were thresholded at 50% of the maximum reconstructed intensity for both visualization and statistical purposes. We previously demonstrated that MEM source localization results provide maps with high contrast, therefore results on the spatial extent are relatively stable within a large range of detection threshold, as opposed to other standard source localization techniques [Chowdhury et al, 2018; Pellegrino et al, 2018; Pellegrino et al, 2019]. In order to assess the success or failure of the localization, we considered the surgical cavity as a reference.…”

Section: Methodsmentioning

confidence: 99%

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

Avigdor

Abdallah

Ellenrieder

et al. 2020

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CONFLICTS OF INTEREST:None of the authors has any conflict of interested related to the submitted work. P a g e | 3 Avigdor et al. | Fast oscillations localize the epileptogenic zone ABSTRACT (245/250) Fast Oscillations (FO) are a promising biomarker of the epileptogenic zone (EZ) in the intracranial electroencephalogram (EEG). Evidence using scalp EEG remains scarce. This is the first study that assesses if electrical source imaging of FO using 256-channel high-density EEG is feasible and useful for EZ identification. We analyzed high-density EEG recordings of 10 focal drug-resistant epilepsy patients with seizure-free postsurgical outcome (follow-up >2 years). We marked FO candidate events at the time of epileptic spikes and then verified them by screening for an isolated peak in the time-frequency plot. We performed electrical source imaging of FOs >40 Hz and spikes using the coherent Maximum Entropy of the Mean technique. Source localization maps were validated against the surgical cavity as approximation of the EZ. We identified FO events in 5 of the 10 patients. FOs were localizable in all 5 patients. The depth of the epileptic generator was either superficial or intermediate in all 5 patients with FO. The maximum of the FO maps was localized in the surgical cavity. We identified spikes in all 10 patients. Spikes were localized to the surgical cavity in 9 of 10 patients. In summary, FOs recorded with high-density EEG are able to localize the EZ. Our findings suggest that the presence of FOs co-localized with spikes points to a surface-close generator. These results can act as a proof of concept for future examination of FOs localization using scalp 256-channel high-density EEG as a viable marker of the EZ. Key words: high-density electroencephalography, epilepsy, maximum entropy of the mean, electrical source imaging, non-invasive localization P a g e | 4 Avigdor et al. | Fast oscillations localize the epileptogenic zone INTRODUCTION Epilepsy is a chronic condition characterized by recurrent seizures accompanied by negative impact on quality of life [Hinnell et al., 2010]. A significant number of 30% of patients with focal epilepsy are drug-resistant, and these numbers did not change over the past 30 years despite the development of multiple new antiepileptic drugs [Chen et al., 2018]. The therapy of choice for focal drug-resistant epilepsy is epilepsy surgery [Vakharia et al., 2018]. The aim of epilepsy surgery is to remove the epileptogenic zone (EZ) defined as the area of cortex that needs to be removed to achieve seizure freedom [Rosenow and Lüders, 2001]. In current praxis, the seizure-onset zone (SOZ) is used as the main proxy marker for the EZ. A sustained seizure-free condition is currently, however, obtained in only 50% of carefully selected patients [Krucoff et al., 2017; Mohan et al., 2018; West et al., 2019]. This is likely due to inaccurate localization of the EZ or a network involvement larger than initially expected [Englot, 2018]. This underlines the need to develop new markers and localiz...

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Section: Methodsmentioning

confidence: 99%