Scientific abstract Epilepsy affects over 60 millions of individuals worldwide. It is estimated that 30 to 40% of epilepsy patients have refractory epilepsy. Surgery may be offered to some patients who are refractory to medical therapy. While better seizure freedom rates are commonly achieved with comprehensive resective surgery, it may be associated with postoperative deficits depending on the area of resection. Pre-surgical evaluation often involves scalp EEG followed in some cases by intracranial monitoring techniques can help localizing seizure onset zone. These procedures are however are often very invasive and have potential for adverse events. High density EEG offers a potential non-invasive alternative to accurately localize epileptic onset zone in individual patients. To date, most high-density EEG studies focused on source reconstruction of scalp spike power [1] and did not take advantage of the high temporal resolution offered by EEG signals to explicitly study spike origin and propagation dynamics. Here we propose to use algorithms previously developed by our team to assess the cortical propagation of discrete EEG events such as sleep slow waves and spindles [2] to characterize the origins and propagation patterns of epileptic spikes captured using high-density EEG recordings. We plan to characterize reproducibility of origins and propagation patterns of epileptic spikes both at the scalp level and in source space, and compare the results obtained using high-density EEG to the ones obtained using intracranial recordings performed in the same patients. We will complement this study by directional connectivity assessments using Granger causality and Dynamic Causal Modeling. If successful, this approach will provide useful information to guide selective resection surgery in drug-refractory epileptic patients, potentially circumventing the need for invasive studies. 1

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We propose to apply traveling waves analyses previously validated for discrete EEG events such as sleep slow waves and spindles to characterize the origins and propagation pathways of epileptic spikes in patients with drug-refractory epilepsy. We will also investigate directional connectivity during epileptic spike activity using advanced EEG analyses techniques such as Granger Causality and Dynamic Causal Modeling, and compare source-reconstructed high density EEG results for all analyses to results obtained using intracranial recordings performed in the same subjects. If successful, this approach could provide useful information to guide selective epilepsy resection surgery, by guiding in which direction to orient resection approaches, and could potentially greatly improve the efficiency of such surgery without a need for more invasive strategies. 1

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
Small Research Grants (R03)
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Neuroscience and Ophthalmic Imaging Technologies Study Section (NOIT)
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Stewart, Randall R
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University of Wisconsin Madison
Schools of Medicine
United States
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