High frequency oscillations as markers of epileptogenic tissue-End of the party?

Clinical Neurophysiology. 2019. Vol. 130. No. 5. P. 624–626.

Fedele T., Ramantani G., Sarnthein J.

Over 20 years of enthusiastic research have served to establish high frequency oscillations (HFO) as a promising biomarker of epileptogenicity, both in animal models and in refractory focal epilepsy patients (Jacobs et al., 2010, 2012; Fedele et al., 2017b; Frauscher et al., 2017; Zijlmans et al., 2017; Gotman, 2018). Several studies have relied on higher interictal HFO occurrence rates to identify the seizure onset zone (SOZ), and thus to detect the epileptogenic tissue in patients undergoing presurgical workup or epilepsy surgery (Jacobs et al., 2010, 2012; Frauscher et al., 2017; Zijlmans et al., 2017). Latest reports showed that residual HFO after epilepsy surgery have the potential to predict poor seizure outcome in the individual patient (van’t Klooster et al., 2015), emphasizing the key role of post-resection ECoG for optimal seizure control (van’t Klooster et al., 2017). Classifying brain regions as ‘‘SOZ” and ‘‘non-SOZ” in a series of refractory focal epilepsy cohorts was guided by the notion that HFO generally present a strong correlation with epileptogenicity and are thus more frequently encountered in the SOZ. HFO rates in these studies were found to depend on several factors, e.g., antiepileptic drug combinations and their withdrawal during presurgical workup (Zijlmans et al., 2009), sleep homeostasis (von Ellenrieder et al., 2017), or localization in different regions throughout the brain (Guragain et al., 2018). Nevertheless, taken together, these studies provided converging evidence of the strong association of HFO with the epileptogenic zone (EZ) and paved the way towards the potential use of HFO, in a prospective way, to guide surgery planning in the individual patient (Fedele et al., 2017b).

 

Keywords: epilepsy, high frequency oscillations