High-frequency oscillations (HFOs) can be spontaneously generated by seizure-onset and functionally-important areas. We determined if consideration of the spectral frequency bands of coupled slow-waves could distinguish between epileptogenic and physiological HFOs.We studied a consecutive series of 13 children with focal epilepsy who underwent extraoperative electrocorticography. We measured the occurrence rate of HFOs during slow-wave sleep at each electrode site. We subsequently determined the performance of HFO rate for localization of seizure-onset sites and undesirable detection of nonepileptic sensorimotor-visual sites defined by neurostimulation. We likewise determined the predictive performance of modulation index: MI(XHz)(YHz), reflecting the strength of coupling between amplitude of HFOsXHz and phase of slow-waveYHz. The predictive accuracy was quantified using the area under the curve (AUC) on receiver-operating characteristics analysis.Increase in HFO rate localized seizure-onset sites (AUC⩾0.72; p0.001), but also undesirably detected nonepileptic sensorimotor-visual sites (AUC⩾0.58; p0.001). Increase in MI(HFOs)(3-4Hz) also detected both seizure-onset (AUC⩾0.74; p0.001) and nonepileptic sensorimotor-visual sites (AUC⩾0.59; p0.001). Increase in subtraction-MIHFOs [defined as subtraction of MI(HFOs)(0.5-1Hz) from MI(HFOs)(3-4Hz)] localized seizure-onset sites (AUC⩾0.71; p0.001), but rather avoided detection of nonepileptic sensorimotor-visual sites (AUC⩽0.42; p0.001).Our data suggest that epileptogenic HFOs may be coupled with slow-wave3-4Hz more preferentially than slow-wave0.5-1Hz, whereas physiologic HFOs with slow-wave0.5-1Hz more preferentially than slow-wave3-4Hz during slow-wave sleep.Further studies in larger samples are warranted to determine if consideration of the spectral frequency bands of slow-waves coupled with HFOs can positively contribute to presurgical evaluation of patients with focal epilepsy.
