Optimization of cortico-cortical spectral response analysis parameters for seizure onset zone localization

While cortico-cortical spectral responses (CCSRs) have shown potential for seizure onset zone (SOZ) localization, it is unclear which features of the CCSR are most localizing, limiting their use as potential biomarkers of the SOZ.

Single-pulse electrical stimulation (SPES) was performed during intracranial EEG (sEEG and ECoG) monitoring in 27 patients, and CCSRs were calculated. We quantified significant increases and decreases in the CCSR and then segmented the CCSRs into 11 time-frequency zones (TFZs). We compared brain regions with the most significant responses in each TFZ to the hypothesized SOZ to determine the localization potential of individual TFZs.

We found that the contacts having the strongest responses in the TFZ spanning the high gamma frequency band (50-250 Hz) and the N2 time interval (50-500 ms) were more related to the SOZ than other TFZs.

These findings suggest that changes in high gamma power 50-500 ms following SPES hold the greatest SOZ localizing potential and may be optimal parameters for investigating the CCSR for biomarkers of the SOZ.

Optimal interpretation of CCSRs may lead to improved SOZ localization and more favorable treatment outcomes for those with drug-resistant epilepsy.