Noninvasive high-frequency oscillations riding spikes delineates epileptogenic sources

Abstract

High-frequency oscillations (HFOs) are a promising biomarker for localizing epileptogenic brain and guiding successful neurosurgery. However, the utility and translation of noninvasive HFOs, although highly desirable, is impeded by the difficulty in differentiating pathological HFOs from nonepileptiform high-frequency activities and localizing the epileptic tissue using noninvasive scalp recordings, which are typically contaminated with high noise levels. Here, we show that the consistent concurrence of HFOs with epileptiform spikes (pHFOs) provides a tractable means to identify pathological HFOs automatically, and this in turn demarks an epileptiform spike subgroup with higher epileptic relevance than the other spikes in a cohort of 25 temporal epilepsy patients (including a total of 2,967 interictal spikes and 1,477 HFO events). We found significant morphological distinctions of HFOs and spikes in the presence/absence of this concurrent status. We also demonstrated that the proposed pHFO source imaging enhanced localization of epileptogenic tissue by 162% (∼5.36 mm) for concordance with surgical resection and by 186% (∼12.48 mm) with seizure-onset zone determined by invasive studies, compared to conventional spike imaging, and demonstrated superior congruence with the surgical outcomes. Strikingly, the performance of spike imaging was selectively boosted by the presence of spikes with pHFOs, especially in patients with multitype spikes. Our findings suggest that concurrent HFOs and spikes reciprocally discriminate pathological activities, providing a translational tool for noninvasive presurgical diagnosis and postsurgical evaluation in vulnerable patients.

Quantitative analysis of visually reviewed normal scalp EEG predicts seizure freedom following anterior temporal lobectomy

“…among the common quantitative measures studied using both scalp and intracranial EEG. [15][16][17][18][19][20][21] More recently, the investigation of high-frequency oscillations recorded on scalp EEG [22][23][24] and interictal spikes from combined scalp and intracranial EEG 25 have received significant interest in the study of outcome prognostication. However, the evaluation of interictal EEG without epileptiform activity or slowing, that is, visually classified normal EEG by an epileptologist, has received less attention.…”

BrainQuake: An Open-Source Python Toolbox for the Stereoelectroencephalography Spatiotemporal Analysis

“…The HFO subcategory, 80-250 Hz ripple component, is relatively more common than a higher frequency component (Wang et al, 2013). This frequency band can also take into account the spike activity, which is similar to a full-band signal (Roehri et al, 2017;Cai et al, 2021). Therefore, for the interictal data, we extracted the pathological activity by detecting the short-term abnormal energy enhancement in the 80-250 Hz band, providing an efficient indexation method through unified energy detection.…”

Characterizing Hippocampal Oscillatory Signatures Underlying Seizures in Temporal Lobe Epilepsy

“…Due to higher HFO instances in the ipsilateral hippocampus rather than the contralateral side can be used as a biomarker for the seizure focus ( Řehulka et al, 2019 ) path. Non-invasive tools have already been developed for better detection with minimal discomfort for people with TLE ( Cai et al, 2021 ). As such, not only can HFOs be used to predict the first spontaneous seizure (after latency), but they could also be used to predict the ongoing seizures throughout chronicity and their site of generation ( Table 1 summarizes the important studies which observed pathological HFOs either in the human and rodents).…”

“…The question about what latency constitutes and its role in developing TLE has been open for a long time. It is pressing even more now that we have better tools to assess the mechanisms underlying progression ( Cai et al, 2021 ). Insights about brain activity during the so-called “latent period” may lead to better targeting procedures for interventions in TLE, possibly through earlier therapeutic windows.…”