High frequency oscillations mirror disease activity in patients with focal cortical dysplasia

Abstract

SUMMARYPurpose: The study analyzes the occurrence of high frequency oscillations in different types of focal cortical dysplasia in 22 patients with refractory epilepsy. High frequency oscillations are biomarkers for epileptic tissue, but it is unknown whether they can reflect increasingly dysplastic tissue changes as well as epileptic disease activity. Methods: High frequency oscillations (80-450 Hz) were visually marked by two independent reviewers in all channels of intracranial implanted grid, strips, and depth electrodes in patients with focal cortical dysplasia and refractory epilepsy. Rates of high frequency oscillations in patients with pathologically confirmed focal cortical dysplasia of Palmini type 1a and b were compared with those in type 2a and b. Key Findings: Patients with focal cortical dysplasia type 2 had significantly more seizures than those with type 1 (p < 0.001). Rates of high frequency oscillations were significantly higher in patients with focal cortical dysplasia type 2 versus type 1 (p < 0.001). In addition, it could be confirmed that rates of high frequency oscillations were significantly higher in presumed epileptogenic areas than outside (p < 0.001). Significance: Activity of high frequency oscillations mirrors the higher epileptogenicity of focal cortical dysplasia type 2 lesions compared to type 1 lesions. Therefore, rates of high frequency oscillations can reflect disease activity of a lesion. This has implications for the use of high frequency oscillations as biomarkers for epileptogenic areas, because a detailed analysis of their rates may be necessary to use high frequency oscillations as a predictive tool in epilepsy surgery.

High‐frequency oscillations: The state of clinical research

“…1,40,44 Whereas no difference was found between intracranial rates of HFOs in adults and children, 54 the rates of scalp HFOs were reported to be up to 100-fold higher in children compared to adults with epilepsy. 55 Higher HFO rates in the scalp EEG of young children are most likely due to a higher skull conductivity compared to adults.…”

“…HFO rates were higher in patients with focal cortical dysplasia type II lesions compared to type I lesions; usually type II lesions are more epileptogenic with an earlier onset of seizures as well as a higher seizure frequency. 54 …”

“…Consistent with the literature, patients with focal cortical dysplasia type II had significantly more seizures than those with type I. Interestingly, rates of HFOs were significantly higher in patients with focal cortical dysplasia type II versus type I, suggesting that the activity of HFOs mirrors disease activity. 54 …”

Residual fast ripples in the intraoperative corticogram predict epilepsy surgery outcome

“…Furthermore, post-resection data leave fewer patients with events, especially FRs. [30][31][32][33][34] We chose our primary outcome parameter to differentiate between absolute seizure freedom and Distribution mean event rate This low sensitivity could be explained by insufficient spatial sampling of FRs, particularly in deeper structures.…”

Targeting high frequency oscillations in epilepsy

“…Growing observations suggest that HFOs are highly specific for demarcating epileptogenic cortex. They are higher inside the seizure onset zone (SOZ) than control regions (Worrell et al, 2008), identify the SOZ with better specificity than spikes (Jacobs et al, 2010), correlate with disease severity (Kerber et al, 2013), and confer a better outcome if resected during epilepsy surgery than if left behind (for example, Jacobs et al, 2010). …”