Interictal high frequency oscillations (HFOs) in patients with focal epilepsy and normal MRI

Abstract High-frequency oscillations (HFO) are promising EEG biomarkers of epileptogenicity. While the evidence supporting their significance derives mainly from invasive recordings, recent studies have extended these observations to HFO recorded in the widely accessible scalp EEG. Here, we investigated whether scalp HFO in drug-resistant focal epilepsy correspond to epilepsy severity and how they are affected by surgical therapy. In eleven children with drug-resistant focal epilepsy that underwent epilepsy surgery, we prospectively recorded pre- and postsurgical scalp EEG with a custom-made low-noise amplifier (LNA). In four of these children, we also recorded intraoperative electrocorticography (ECoG). To detect clinically relevant HFO, we applied a previously validated automated detector. Scalp HFO rates showed a significant positive correlation with seizure frequency (R2 = 0.80, p < 0.001). Overall, scalp HFO rates were higher in patients with active epilepsy (19 recordings, p = 0.0066, PPV = 86%, NPV = 80%, accuracy = 84% CI [62% 94%]) and decreased following successful epilepsy surgery. The location of the highest HFO rates in scalp EEG matched the location of the highest HFO rates in ECoG. This study is the first step towards using non-invasively recorded scalp HFO to monitor disease severity in patients affected by epilepsy.

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Stereotyped high-frequency oscillations discriminate seizure onset zones and critical functional cortex in focal epilepsy

Brain ◽

10.1093/brain/awx374 ◽

2018 ◽

Vol 141 (3) ◽

pp. 713-730 ◽

Cited By ~ 24

Author(s):

Su Liu ◽

Candan Gurses ◽

Zhiyi Sha ◽

Michael M Quach ◽

Altay Sencer ◽

...

Keyword(s):

High Frequency ◽

Focal Epilepsy ◽

Machine Learning Techniques ◽

Seizure Onset ◽

Functional Regions ◽

Clinical Biomarkers ◽

High Frequency Oscillations ◽

Potential Association ◽

Waveform Similarity ◽

Seizure Onset Zones

Abstract High-frequency oscillations in local field potentials recorded with intracranial EEG are putative biomarkers of seizure onset zones in epileptic brain. However, localized 80–500 Hz oscillations can also be recorded from normal and non-epileptic cerebral structures. When defined only by rate or frequency, physiological high-frequency oscillations are indistinguishable from pathological ones, which limit their application in epilepsy presurgical planning. We hypothesized that pathological high-frequency oscillations occur in a repetitive fashion with a similar waveform morphology that specifically indicates seizure onset zones. We investigated the waveform patterns of automatically detected high-frequency oscillations in 13 epilepsy patients and five control subjects, with an average of 73 subdural and intracerebral electrodes recorded per patient. The repetitive oscillatory waveforms were identified by using a pipeline of unsupervised machine learning techniques and were then correlated with independently clinician-defined seizure onset zones. Consistently in all patients, the stereotypical high-frequency oscillations with the highest degree of waveform similarity were localized within the seizure onset zones only, whereas the channels generating high-frequency oscillations embedded in random waveforms were found in the functional regions independent from the epileptogenic locations. The repetitive waveform pattern was more evident in fast ripples compared to ripples, suggesting a potential association between waveform repetition and the underlying pathological network. Our findings provided a new tool for the interpretation of pathological high-frequency oscillations that can be efficiently applied to distinguish seizure onset zones from functionally important sites, which is a critical step towards the translation of these signature events into valid clinical biomarkers. 5721572971001 awx374media1 5721572971001

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Spike-related haemodynamic responses overlap with high frequency oscillations in patients with focal epilepsy

Brain ◽

10.1093/brain/awx383 ◽

2018 ◽

Vol 141 (3) ◽

pp. 731-743 ◽

Cited By ~ 10

Author(s):

Karina A González Otárula ◽

Hui Ming Khoo ◽

Nicolás von Ellenrieder ◽

Jeffery A Hall ◽

François Dubeau ◽

...

Keyword(s):

High Frequency ◽

Focal Epilepsy ◽

High Frequency Oscillations

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Ictal Occurrence of High-Frequency Oscillations Correlates With Seizure Severity in a Rat Model of Temporal Lobe Epilepsy

Frontiers in Human Neuroscience ◽

10.3389/fnhum.2021.624620 ◽

2021 ◽

Vol 15 ◽

Author(s):

Nadja Birk ◽

Jan Schönberger ◽

Karin Helene Somerlik-Fuchs ◽

Andreas Schulze-Bonhage ◽

Julia Jacobs

Keyword(s):

Temporal Lobe Epilepsy ◽

Temporal Lobe ◽

Rat Model ◽

High Frequency ◽

Focal Epilepsy ◽

Epileptic Activity ◽

Seizure Severity ◽

Chronic Epilepsy ◽

High Frequency Oscillations

High-frequency oscillations (HFOs, ripples 80–250 Hz, fast ripples 250–500 Hz) are biomarkers of epileptic tissue. They are most commonly observed over areas generating seizures and increase in occurrence during the ictal compared to the interictal period. It has been hypothesized that their rate correlates with the severity of epilepsy and seizure in affected individuals. In the present study, it was aimed to investigate whether the HFO count mirrors the observed behavioral seizure severity using a kainate rat model for temporal lobe epilepsy. Seizures were selected during the chronic epilepsy phase of this model and classified by behavioral severity according to the Racine scale. Seizures with Racine scale 5&6 were considered generalized and severe. HFOs were marked in 24 seizures during a preictal, ictal, and postictal EEG segment. The duration covered by the HFO during these different segments was analyzed and compared between mild and severe seizures. HFOs were significantly increased during ictal periods (p < 0.001) and significantly decreased during postictal periods (p < 0.03) compared to the ictal segment. Ictal ripples (p = 0.04) as well as fast ripples (p = 0.02) were significantly higher in severe seizures compared to mild seizures. The present study demonstrates that ictal HFO occurrence mirrors seizure severity in a chronic focal epilepsy model in rats. This is similar to recent observations in patients with refractory mesio-temporal lobe epilepsy. Moreover, postictal HFO decrease might reflect postictal inhibition of epileptic activity. Overall results provide additional evidence that HFOs can be used as biomarkers for measuring seizure severity in epilepsy.

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Epilepsy Surgery for Refractory Focal Epilepsy based on the Analysis of High Frequency Oscillations with Intracranial Electroencephalography : A Case Report

Japanese Journal of Neurosurgery ◽

10.7887/jcns.24.32 ◽

2015 ◽

Vol 24 (1) ◽

pp. 32-39

Author(s):

Akihiko Kondo ◽

Tomoyuki Akiyama ◽

Takashi Agari ◽

Makio Oka ◽

Yoshinori Kobayashi ◽

...

Keyword(s):

Case Report ◽

Epilepsy Surgery ◽

High Frequency ◽

Focal Epilepsy ◽

High Frequency Oscillations ◽

Intracranial Electroencephalography

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Ictal and interictal high frequency oscillations in patients with focal epilepsy

Clinical Neurophysiology ◽

10.1016/j.clinph.2010.09.021 ◽

2011 ◽

Vol 122 (4) ◽

pp. 664-671 ◽

Cited By ~ 114

Author(s):

Maeike Zijlmans ◽

Julia Jacobs ◽

Yusuf U. Kahn ◽

Rina Zelmann ◽

François Dubeau ◽

...

Keyword(s):

High Frequency ◽

Focal Epilepsy ◽

High Frequency Oscillations

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High-frequency oscillations detected in ECoG recordings correlate with cavernous malformation and seizure-free outcome in a child with focal epilepsy: A case report

Epilepsia Open ◽

10.1002/epi4.12056 ◽

2017 ◽

Vol 2 (2) ◽

pp. 267-272 ◽

Cited By ~ 3

Author(s):

Su Liu ◽

Michael M. Quach ◽

Daniel J. Curry ◽

Monika Ummat ◽

Elaine Seto ◽

...

Keyword(s):

Case Report ◽

High Frequency ◽

Cavernous Malformation ◽

Focal Epilepsy ◽

High Frequency Oscillations

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Pathologic substrates of focal epilepsy influence the generation of high-frequency oscillations

Epilepsia ◽

10.1111/epi.12940 ◽

2015 ◽

Vol 56 (4) ◽

pp. 592-598 ◽

Cited By ~ 41

Author(s):

Taissa Ferrari-Marinho ◽

Piero Perucca ◽

Kelvin Mok ◽

Andre Olivier ◽

Jeffery Hall ◽

...

Keyword(s):

High Frequency ◽

Focal Epilepsy ◽

High Frequency Oscillations

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Spatiotemporal patterns of high-frequency activity (80-170 Hz) in long-term intracranial EEG

10.1101/2020.03.26.999425 ◽

2020 ◽

Author(s):

Zhuying Chen ◽

David B. Grayden ◽

Anthony N. Burkitt ◽

Udaya Seneviratne ◽

Wendyl J. D’Souza ◽

...

Keyword(s):

Circadian Rhythms ◽

High Frequency ◽

Focal Epilepsy ◽

Patient Specific ◽

Intracranial Eeg ◽

Electrode Implantation ◽

High Frequency Oscillations ◽

Total Data ◽

High Frequency Activity

AbstractObjectiveTo assess the variability in the rates and locations of high-frequency activity (HFA) and epileptiform spikes after electrode implantation, and to examine the long-term patterns of HFA using ambulatory intracranial EEG (iEEG) recordings.MethodsContinuous iEEG recordings obtained over an average of 1.4 years from 15 patients with drug-resistant focal epilepsy were used in this study. HFA was defined as high-frequency events with amplitudes clearly larger than the background, which was automatically detected using a custom algorithm. High-frequency oscillations (HFOs) were also visually annotated by three neurologists in randomly sampled segments of the total data. The automatically detected HFA was compared with the visually marked HFOs. The variations of HFA rates were compared with spikes and seizures on patient-specific and electrode-specific bases.ResultsHFA was a more general event that encompassed HFOs manually annotated by different reviewers. HFA and spike rates had high amounts of intra- and inter-patient variability. The rates and locations of HFA and spikes took up to weeks to stabilize after electrode implantation in some patients. Both HFA and spike rates showed strong circadian rhythms in all patients and some also showed multiday cycles. Furthermore, the circadian patterns of HFA and spike rates had patient-specific correlations with seizures, which tended to vary across electrodes.ConclusionsAnalysis of HFA and epileptiform spikes should account for post-implantation variability. Like seizures, HFA and epileptiform spikes show circadian rhythms. However, the circadian profiles can vary spatially within patients and their correlations to seizures are patient-specific.

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