Interictal high frequency oscillations (HFOs) in patients with focal epilepsy and normal MRI

Abstract

Analysis of interictal HFOs during 5-10 min of sleep recording is a good tool to localize the SOZ in patients with epilepsy and normal MRI, and could potentially reduce the duration of chronic intracerebral EEG recordings.

Electrophysiological Biomarkers of Epilepsy

“…The link between the rates of fast ripple-frequency HFOs and SOZ was also confirmed [65,101,102], and from these studies evidence for the association of ripple-frequency HFOs and the SOZ in MTLE and neocortical epilepsies was obtained, although fast ripple-frequency HFOs appear more specific to the SOZ, particularly in MTLE [63]. In addition, HFOs were observed in epileptogenic tissue extending beyond areas of pathology in other lesional epilepsies [102], and another study found HFOs in the SOZ of magnetic resonance imaging (MRI)-negative patients [103], although histological analysis of resected tissue indicated gliosis and neuron loss in many of these patients.…”

Using ictal high-frequency oscillations (80–500Hz) to localize seizure onset zones in childhood absence epilepsy: A MEG study

“…A previous study that used intracranial depth stereo-EEG investigations reported that HFOs remained confined in the same area (possibly epileptogenic area) during interictal and ictal periods, whereas spikes were more widespread during seizures than interictal period [26]. HFO-generating regions identified SOZ with greater specificity and accuracy compared with that of the spike-generating regions [9,27]. Furthermore, some studies indicated that removal of the HFO-generating region predicted better surgical outcome [10][11][12][13].…”

Neuromagnetic high-frequency oscillations correlate with seizure severity in absence epilepsy

“…Compared with spikes, these HFOs seem more specific for SOZ and could be helpful in determining the EZ in the clinical practice of epilepsy surgery Weiss et al, 2013). In other studies, interictal HFOs obtained during sleep, but not those based on the record of an ictal event, were also found to provide reliable information regarding SOZ localization (Andrade-Valenca et al, 2012). Larger numbers of interictal HFOs indicate greater risk of seizure; thus interictal HFOs are a sign of seizure susceptibility (Zijlmans et al, 2011;Jacobs et al, 2012).…”