Detection of High Frequency Oscillations with Teager Energy in an Animal Model of Limbic Epilepsy

Nelson, Ryan; Myers, Stephen M.; Simonotto, Jennifer; Furman, Michael D.; Spano, Mark L.; Norman, Wendy M.; Liu, Zhao; DeMarse, Thomas B.; Carney, Paul R.; Ditto, William L.

doi:10.1109/iembs.2006.259694

Cited by 17 publications

(8 citation statements)

References 17 publications

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“…To analyze HFOs over longer periods, an automatic detection of the oscillations would be necessary. Methods to detect distinct HFOs have been proposed (Staba et al., 2002; Nelson et al., 2006; Gardner et al., 2007), but we did not find them adequate for our requirements; an automatic detector should not only be able to detect HFOs within variable baselines, but also to distinguish between HFOs co‐occurring with spikes and those outside spikes. Visual analysis and manual marking of HFOs in this study had two advantages over automated methods.…”

Section: Discussionmentioning

confidence: 96%

High frequency oscillations (80–500 Hz) in the preictal period in patients with focal seizures

et al. 2009

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SUMMARYPurpose: Intracranial depth macroelectrode recordings from patients with focal seizures demonstrate interictal and ictal high frequency oscillations (HFOs, 80-500 Hz). These HFOs are more frequent in the seizure-onset zone (SOZ) and reported to be linked to seizure genesis. We evaluated whether HFO activity changes in a systematic way during the preictal period. Methods: Fifteen minutes of preictal intracranial electroencephalography (EEG) recordings were evaluated in seven consecutive patients with welldefined SOZ. EEG was filtered at 500 Hz and sampled at 2,000 Hz. Ripples (80-250 Hz) and fast ripples (250-500 Hz) were visually marked, and spectral analysis was performed in seizure-onset as well as nonseizure-onset channels. Linear regressions fitted to the power trends corresponding to intervals of 1, 5, and 15 min before the seizure onset was calculated. Results: Total rates of HFOs were significantly higher in the SOZ than outside. Preictal increases and decreases in HFO rates and band power could be detected in all patients, and they were not limited to the SOZs. These measures were very variable, and no systematic trends were observed when comparing patients or seizures in the same patient. Discussion: High frequencies in the range of 80-500 Hz are present during the preictal period and are more prominent in the SOZ. They do not change in a systematic way before seizure onset for the horizons we tested. The 80-500 Hz band may be used for the localization of seizure-onset areas but may be more difficult to use for seizure prediction purposes.

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Section: Discussionmentioning

confidence: 96%

High frequency oscillations (80–500 Hz) in the preictal period in patients with focal seizures

et al. 2009

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“…Given that HFOs are short oscillatory events that stand out from the baseline, a logical approach to identify them is applying an energy‐based detector. Automatic detection methods are being developed based on the comparison of the local energy of the signal with the whole EEG epoch (including HFOs or with marked baseline segments 11, 24, 64–67. When comparing the performance of these detectors, the behavior is similar in channels where HFOs are rare events that can be clearly distinguished from the surrounding background.…”

Section: How Can Hfos Be Visualized and Detected?mentioning

confidence: 99%

High‐frequency oscillations as a new biomarker in epilepsy

Zijlmans

Jiruška

Zelmann

et al. 2012

Annals of Neurology

431

363

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The discovery that electroencephalography (EEG) contains useful information at frequencies above the traditional 80Hz limit has had a profound impact on our understanding of brain function. In epilepsy, high-frequency oscillations (HFOs, >80Hz) have proven particularly important and useful. This literature review describes the morphology, clinical meaning, and pathophysiology of epileptic HFOs. To record HFOs, the intracranial EEG needs to be sampled at least at 2,000Hz. The oscillatory events can be visualized by applying a high-pass filter and increasing the time and amplitude scales, or EEG time-frequency maps can show the amount of high-frequency activity. HFOs appear excellent markers for the epileptogenic zone. In patients with focal epilepsy who can benefit from surgery, invasive EEG is often required to identify the epileptic cortex, but current information is sometimes inadequate. Removal of brain tissue generating HFOs has been related to better postsurgical outcome than removing the seizure onset zone, indicating that HFOs may mark cortex that needs to be removed to achieve seizure control. The pathophysiology of epileptic HFOs is challenging, probably involving populations of neurons firing asynchronously. They differ from physiological HFOs in not being paced by rhythmic inhibitory activity and in their possible origin from population spikes. Their link to the epileptogenic zone argues that their study will teach us much about the pathophysiology of epileptogenesis and ictogenesis. HFOs show promise for improving surgical outcome and accelerating intracranial EEG investigations. Their potential needs to be assessed by future research.

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“…As automatic detection programs are developed, longer time frames can be studied. 5, 38 We chose not to use automatic detection because it has not been validated enough (on our data) and because separation of HFOs with and without spikes by such methods is not possible yet. Second, the limited number of patients did not allow distinction between different kinds of epilepsies (different locations or etiologies) and medication types.…”

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High-frequency oscillations mirror disease activity in patients with epilepsy

Zijlmans

Jacobs²,

Zelmann³

et al. 2009

Neurology

219

175

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Objective-High-frequency oscillations (HFOs) can be recorded in epileptic patients with clinical intracranial EEG. HFOs have been associated with seizure genesis because they occur in the seizure focus and during seizure onset. HFOs are also found interictally, partly co-occurring with epileptic spikes. We studied how HFOs are influenced by antiepileptic medication and seizure occurrence, to improve understanding of the pathophysiology and clinical meaning of HFOs.Methods-Intracerebral depth EEG was partly sampled at 2,000 Hz in 42 patients with intractable focal epilepsy. Patients with five or more usable nights of recording were selected. A sample of slow-wave sleep from each night was analyzed, and HFOs (ripples: 80-250 Hz, fast ripples: 250-500 Hz) and spikes were identified on all artifact-free channels. The HFOs and spikes were compared before and after seizures with stable medication dose and during medication reduction with no intervening seizures.Results-Twelve patients with five to eight nights were included. After seizures, there was an increase in spikes, whereas HFO rates remained the same. Medication reduction was followed by an increase in HFO rates and mean duration.Conclusions-Contrary to spikes, high-frequency oscillations (HFOs) do not increase after seizures, but do so after medication reduction, similarly to seizures. This implies that spikes and HFOs have different pathophysiologic mechanisms and that HFOs are more tightly linked to seizures than spikes. HFOs seem to play an important role in seizure genesis and can be a useful clinical marker for disease activity.High-frequency oscillations (HFOs) in intracranial EEG have been associated with epileptogenesis and seizure genesis and have been studied in humans and rats. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] They have been divided into ripples (80 -250 Hz) and fast ripples (FRs; 250 -500 Hz). 13 Ripples have been considered more physiologic in nature because they have also been recorded in healthy animal brains, whereas FRs are more frequent in affected hippocampi. 3,6,[15][16][17][18][19][20] Address correspondence and reprint requests to Dr. Jean Gotman, Montreal Neurological Institute and Hospital, 3801 University St., Montreal, Quebec, Canada H3A 2B4, jean.gotman@mcgill.ca. Disclosure: J.G. was a major shareholder of Stellate. The other authors report no disclosures. AUTHOR CONTRIBUTIONS CIHR Author Manuscript CIHR Author Manuscript CIHR Author ManuscriptHowever, both ripples and FRs have been correlated with the seizure onset zone (SOZ). 7,11,21 HFOs were first recorded with microelectrodes but can also be recorded with clinically used macroelectrodes. 11,13,[21][22][23] HFOs have been associated with seizure genesis because their localization is related to the seizure focus and they occur at seizure onset 1,6,11,24 and with epileptogenesis, as HFOs occurred before spontaneous seizures in kainic acid-injected rats. 7 They may result from a γ-aminobuteric acid-mediated feedback imbalance or pathologic neuronal connecti...

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Detection of High Frequency Oscillations with Teager Energy in an Animal Model of Limbic Epilepsy

Cited by 17 publications

References 17 publications

High frequency oscillations (80–500 Hz) in the preictal period in patients with focal seizures

High frequency oscillations (80–500 Hz) in the preictal period in patients with focal seizures

High‐frequency oscillations as a new biomarker in epilepsy

High-frequency oscillations mirror disease activity in patients with epilepsy

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