Delayed high-frequency suppression after automated single-pulse electrical stimulation identifies the seizure onset zone in patients with refractory epilepsy

Abstract

ObjectiveSingle-pulse electrical stimulation (SPES) of intracranial electrodes evokes responses that may help identify the seizure onset zone (SOZ); however, lack of automation and response variability has limited clinical adoption of this technique. We evaluated whether automated delivery of low-current SPES could evoke delayed high-frequency suppression (DHFS) of ongoing electrocorticography (ECoG) signals that, when combined with objective analytic techniques, may provide a reliable marker of this zone. MethodsLow-current SPES (1-ms, 3.5-mA biphasic pulses) was delivered to 652 electrodes across 10 patients undergoing ECoG for seizure focus localization. DHFS was measured by calculating the normalized trial-averaged time-frequency power (70–250 Hz) 0.4–1 sec post-stimulation. Electrodes that evoked suppression when stimulated or recorded suppression when stimulation was nearby were used to estimate the SOZ. ResultsThe estimated SOZ significantly identified the clinical SOZ in 6 of 10 patients (5 of 7 temporal foci) with a false-positive rate of 0–0.06. Stimulation required <2 h, was undetectable by patients, and did not induce seizures or after-discharges. ConclusionsWe show that DHFS provides accurate estimates of the clinical SOZ in patients with refractory epilepsy. SignificanceThis approach may increase the safety, speed, and reproducibility of SOZ identification while reducing cost, subjectivity, and patient discomfort.