Detectability of Fast Ripples (&gt;250 Hz) on the Scalp EEG: A Proof-of-Principle Study with Subdermal Electrodes

Pizzo, Francesca; Frauscher, Birgit; Ferrari-Marinho, Taíssa; Amiri, Mina; Dubeau, François; Gotman, Jean

doi:10.1007/s10548-016-0481-7

Cited by 43 publications

(31 citation statements)

References 39 publications

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“…67 Only very recently, the detection of HFOs > 250 Hz was attempted in a pilot study. 68 In this proof-of-principle study, it was shown that it might be feasible to record even frequencies > 250 Hz with scalp EEG; the rate of fast ripples was considerably lower than that of ripples. Table 1 provides an overview on the literature on HFO assessment in scalp EEG.…”

Section: Scalp Eegmentioning

confidence: 93%

High‐frequency oscillations: The state of clinical research

et al. 2017

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Summary Modern electroencephalographic (EEG) technology contributed to the appreciation that the EEG signal outside the classical Berger frequency band contains important information. In epilepsy, research of the past decade focused particularly on interictal high-frequency oscillations (HFOs) > 80 Hz. The first large application of HFOs was in the context of epilepsy surgery. This is now followed by other applications such as assessment of epilepsy severity and monitoring of antiepileptic therapy. This article reviews the evidence on the clinical use of HFOs in epilepsy with an emphasis on the latest developments. It highlights the growing literature on the association between HFOs and post-surgical seizure outcome. A recent meta-analysis confirmed a higher resection ratio for HFOs in seizure-free versus non–seizure-free patients. Residual HFOs in the postoperative electrocorticogram were shown to predict epilepsy surgery outcome better than preoperative HFO rates. The review further discusses the different attempts to separate physiological from epileptic HFOs, as this might increase the specificity of HFOs. As an example, analysis of sleep microstructure demonstrated a different coupling between HFOs inside and outside the epileptogenic zone. Moreover, there is increasing evidence that HFOs are useful to measure disease activity and assess treatment response using noninvasive EEG and magnetoencephalography. This approach is particularly promising in children, because they show high scalp HFO rates. HFO rates in West syndrome decrease after adrenocorticotropic hormone treatment. Presence of HFOs at the time of rolandic spikes correlates with seizure frequency. The time-consuming visual assessment of HFOs, which prevented their clinical application in the past, is now overcome by validated computer-assisted algorithms. HFO research has considerably advanced over the past decade, and use of noninvasive methods will make HFOs accessible to large numbers of patients. Prospective multicenter trials are awaited to gather information over long recording periods in large patient samples.

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Section: Scalp Eegmentioning

confidence: 93%

High‐frequency oscillations: The state of clinical research

et al. 2017

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“…[4][5][6][7] In contrast to ECoG, the identification of HFOs with noninvasive scalp electroencephalography (EEG) has proven more challenging. Although several studies have linked beta, gamma, and ripple activity to hypsarrhythmia 8 and epileptic spasms 9,10 in West syndrome, and to the seizure-onset zones in focal epilepsy, 11 it is only recently that fast ripples (FRs) have been identified with the use of subdermal scalp electrodes in adults with epilepsy, 12 and with the use of standard scalp electrodes in children with epilepsy. 13 Nevertheless, it has not yet been established that the visual identification and quantification of scalp HFOs is reliable.…”

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confidence: 99%

Interrater reliability in visual identification of interictal high‐frequency oscillations on electrocorticography and scalp EEG

Nariai

Bernardo

et al. 2018

Epilepsia Open

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SummaryHigh‐frequency oscillations (HFOs), including ripples (Rs) and fast ripples (FRs), are promising biomarkers of epileptogenesis, but their clinical utility is limited by the lack of a standardized approach to identification. We set out to determine whether electroencephalographers experienced in HFO analysis can reliably identify and quantify interictal HFOs. Two blinded raters independently reviewed 10 intraoperative electrocorticography (ECoG) samples from epilepsy surgery cases, and 10 scalp EEG samples from epilepsy monitoring unit evaluations. HFOs were visually marked using bandpass filters (R, 80–250 Hz; FR, 250–500 Hz) with a sampling frequency of 2,000 Hz. There was agreement as to the presence or absence of epileptiform discharges (EDs), Rs, and FRs, in 17, 18, and 18 cases, respectively. Interrater reliability (IRR) was favorable with κ = 0.70, 0.80, and 0.80, respectively, and similar for ECoG and scalp electroencephalography (EEG). Furthermore, interclass correlation for rates of Rs (0.99, 95% confidence interval [CI] 0.96–0.99) and FRs (0.77, 95% CI 0.41–0.91) were superior in comparison to EDs (0.37, 95% CI −0.60 to 0.75). Our data suggest that HFO identification and quantification are reliable among experienced electroencephalographers. Our findings support the reliability of utilizing HFO data in both research and clinical arenas.

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“…The recent demonstration that a custom low-noise amplifier increased FR-detection rates—and importantly—improved prediction of postoperative outcome is an encouraging development (Fedele et al, 2017). Further technological innovation is clearly needed, especially as it pertains to ongoing efforts to identify FR on scalp EEG (Pizzo et al, 2016). …”

Section: Discussionmentioning

confidence: 99%

Intraoperative fast ripples independently predict postsurgical epilepsy outcome: Comparison with other electrocorticographic phenomena

et al. 2017

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In the surgical management of epilepsy, the resection of cortex exhibiting interictal fast ripples (250–500 Hz) on electrocorticography has been linked to postoperative seizure-freedom. Although fast ripples appear to accurately identify the epileptogenic zone—the minimum tissue that must be removed at surgery to achieve seizure-freedom—it has not been established that fast ripples are a superior biomarker in comparison with multimodal presurgical neuroimaging and other electrocorticography abnormalities. Hence, in the prediction of postoperative seizure-freedom, we compared the value of fast ripples with other intraoperative electocorticography abnormalities including focal slowing, paroxysmal fast activity, intermittent spike discharges, continuous epileptiform discharges, focal attenuation, and intraoperative seizures, as well as complete resection of the lesion defined by MRI and other neuroimaging. In a cohort of 60 children with lesional epilepsy and median postsurgical follow-up exceeding 4 years, who underwent resective epilepsy surgery with intraoperative electrocorticography, we evaluated the extent to which removal of each intraoperative electrocorticography abnormality impacts time to first postoperative seizure using the Kaplan-Meier method and Cox proportional hazards regression. Secondly, we contrasted the predictive value of resection of each competing electrocorticography abnormality using standard test metrics (sensitivity, specificity, positive predictive value, and negative predictive value). In contrast with all other intraoperative electrocorticography abnormalities, fast ripples demonstrated the most favorable combination of positive predictive value (100%) and negative predictive value (76%) in the prediction of postoperative seizures. Among all candidate electrocorticography features, time to first postoperative seizure was most strongly associated with incomplete resection of fast ripples (hazard ratio = 19.8, p <0.001). In multivariate survival analyses, postoperative seizures were independently predicted by incomplete resection of cortex generating fast ripples (hazard ratio = 25.4, 95%CI 6.71 – 96.0, p < 0.001) and focal slowing (hazard ratio = 5.79, 95%CI 1.76 – 19.0, p = 0.004), even after adjustment for the impact of an otherwise complete resection. All children with incomplete resection of interictal FR-generating cortex exhibited postoperative seizures within six months. Notably, this cohort included many patients with large resections and thus limited opportunity to exhibit unresected fast ripples. Future study in a cohort with small resection volume, or a clinical trial in which resection margins are guided by fast ripple distribution, would likely yield a more precise estimate of the risk posed by unresected fast ripples. With a high detection rate during brief intraoperative electrocorticography and favorable positive and negative predictive value, interictal fast ripple characterization during surgery is a feasible and useful adjunct to standard methods for epilepsy surgery...

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Detectability of Fast Ripples (>250 Hz) on the Scalp EEG: A Proof-of-Principle Study with Subdermal Electrodes

Cited by 43 publications

References 39 publications

High‐frequency oscillations: The state of clinical research

High‐frequency oscillations: The state of clinical research

Interrater reliability in visual identification of interictal high‐frequency oscillations on electrocorticography and scalp EEG

Intraoperative fast ripples independently predict postsurgical epilepsy outcome: Comparison with other electrocorticographic phenomena

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