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.
Highlights
High-frequency oscillations (HFO) are promising EEG biomarkers of epileptogenicity
Whether scalp HFO rates correlate with seizure frequency in drug-resistant focal epilepsy and whether a treatment response in terms of scalp HFO reduction can be observed with epilepsy surgery awaits confirmation
We have previously demonstrated that a low-noise amplifier (LNA) significantly enhances the signal-to-noise ratio (SNR) in the HFO spectral range, improving HFO detection in the intraoperative electrocorticography (ECoG) compared to a commercial device (CD)[19,20]
Summary
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. Invasive EEG recordings entail risks of morbidity that are only justified for selected epilepsy surgery candidates These considerations have instigated a shift of HFO research towards non-invasive recordings, towards the widely accessible scalp EEG, aiming to develop potential surrogates of invasive explorations and, valid tools of drug and disease monitoring relevant to a large number of patients affected by epilepsy. We prospectively recorded pre- and postsurgical scalp EEG in children with drug-resistant focal epilepsy undergoing epilepsy surgery and used the LNA to improve HFO detectability as well as an automated detector to ensure a prospective, bias-free definition of clinically relevant HFO. We hypothesized that scalp HFO rates would match seizure frequency, correspond to invasive HFO, and decrease after successful epilepsy surgery, constituting a valuable biomarker for surgical planning and a valid indicator of disease severity
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