Recent advances in the noninvasive detection of high-frequency oscillations in the human brain

Abstract

In recent decades, a significant body of evidence based on invasive clinical research has showed that high-frequency oscillations (HFOs) are a promising biomarker for localization of the seizure onset zone (SOZ), and therefore, have the potential to improve postsurgical outcomes in patients with epilepsy. Emerging clinical literature has demonstrated that HFOs can be recorded noninvasively using methods such as scalp electroencephalography (EEG) and magnetoencephalography (MEG). Not only are HFOs considered to be a useful biomarker of the SOZ, they also have the potential to gauge disease severity, monitor treatment, and evaluate prognostic outcomes. In this article, we review recent clinical research on noninvasively detected HFOs in the human brain, with a focus on epilepsy. Noninvasively detected scalp HFOs have been investigated in various types of epilepsy. HFOs have also been studied noninvasively in other pathologic brain disorders, such as migraine and autism. Herein, we discuss the challenges reported in noninvasive HFO studies, including the scarcity of MEG and high-density EEG equipment in clinical settings, low signal-to-noise ratio, lack of clinically approved automated detection methods, and the difficulty in differentiating between physiologic and pathologic HFOs. Additional studies on noninvasive recording methods for HFOs are needed, especially prospective multicenter studies. Further research is fundamental, and extensive work is needed before HFOs can routinely be assessed in clinical settings; however, the future appears promising.

Scalp HFO rates are higher for larger lesions

“…[9][10][11][12][13][14] Beyond their initial use for demarcating the seizure onset zone in focal lesional epilepsy and thus tailoring epilepsy surgery, [15][16][17][18][19][20] scalp HFO are currently investigated as potential biomarkers of epileptogenesis and treatment response. 21,22 The utility of scalp HFO as a biomarker in pediatric focal lesional epilepsy has been investigated in recent studies that corroborated a positive correlation of scalp HFO rates with (a) seizure risk at the presence of focal lesions, as in tuberous sclerosis, 23 and (b) seizure frequency, as a measure of disease severity, decreasing following successful surgical treatment. 9,10,24 Scalp HFO detectability has been shown to correlate with (a) patient age, with higher HFO rates in younger children, 25 (b) sleep stage, with higher HFO rates in N3 sleep.…”

Automatic Detection of High-Frequency Oscillations With Neuromorphic Spiking Neural Networks

“…Moreover, an accumulation of recent evidence suggests that HFO are also measurable by non-invasive scalp EEG (Andrade-Valenca et al, 2011;Boran et al, 2019c;Kuhnke et al, 2019;van Klink et al, 2019;Cserpan et al, 2021aCserpan et al, , 2022aTamilia et al, 2021;Noorlag et al, 2022). Therefore HFO are investigated as potential biomarkers to delineate the EZ but also to monitor disease severity and treatment response (Fan et al, 2020;Jacobs and Zijlmans, 2020).…”

Update on the Neuroimaging and Electroencephalographic Biomarkers of Epileptogenesis: A Literature Review

“…The appearance of rHFOSs in the injured cortex and around the adjacent injured cortex within 2 weeks from the initial insult in the LFPI model rats was reported to more likely develop spontaneous seizures later in life (20,44). Although HFOs are typically detected with invasive intracranial EEG, the advancements in scalp EEG monitoring equipment enable one to record HFOs on scalp EEG in human studies (53). In a cohort of children after a first unprovoked seizure, the presence of scalp ripples can predict the development of epilepsy (45).…”