Co-occurrence of high-frequency oscillations and delayed responses evoked by intracranial electrical stimulation in stereo-EEG studies

- First direct comparison of high-frequency oscillations and delayed responses using stereo-EEG.
- About 40% of the contacts exhibiting one biomarker also exhibit the other one.
- The biomarkers complement each other for seizure onset zone localization.

ObjectiveTo perform a side-by-side comparison of two epileptogenicity biomarkers, high frequency oscillations (HFOs) and delayed responses (DRs), as a result of single-pulse electrical stimulation.MethodsWe have recorded stimulation-evoked HFOs and DRs in 16 epileptic patients undergoing presurgical evaluation using the stereoelectroencephalographic method. To evaluate converging and complementary information provided by the biomarkers, we analyzed them individually and for logical “and”/“or” combinations between them. 3D maps of the biomarkers' distributions by recording location (inbound maps) and by stimulation location (outbound maps) were created to analyze their relationship with the epileptogenic structures.ResultsHFOs occur less frequently than DRs, by 18.7%, when counting by recording contacts, and more frequently, by 7.4%, when counting by stimulation contacts. 40.6% of the contacts exhibiting HFOs also exhibit DRs, and 44.1% of the contacts exhibiting DRs also exhibit HFOs. When combining biomarkers, there was a tradeoff between increased seizure onset zone (SOZ) sensitivity, from 21.3% to 73%, and decreased specificity, from 87.2% to 34.3%.ConclusionsThere is a moderate similarity in the information provided by the DRs and HFOs.SignificanceThe biomarkers complement each other, but there is a tradeoff between different metrics for SOZ localization.