Authors :
Presenting Author: Irina Oane, MD PhD – University Emergency Hospital Bucharest
Andrei Barborica, PhD – University of Bucharest
Laurentiu Tofan, MD – University Emergency Hospital Bucharest
Stefana Obogeanu, MD – University Emergency Hospital Bucharest
Cristina Ghita, MD – University Emergency Hospital Bucharest
Constantin Pistol, PhD – University of Bucharest
Felicia Mihai, PhD – University of Bucharest
Ioana Mindruta, MD PhD – University Emergency Hospital Bucharest
Rationale:
In patients with focal drug-resistant epilepsy that undergo invasive stereo-electroencephalographic recordings, electrical cortical stimulations (ECS) are performed to map eloquent cortex and refine epileptogenic zone delineation by eliciting seizures. However, this recommendation is based on clinical observations, to this point no electrophysiologic quantification of the network activated by electrical stimulation induced seizure has been performed.
Methods:
We have reviewed the ECS performed in our center from 2018-2025 and selected patients in which habitual electro-clinical seizures were triggered by high-frequency stimulations with alternating polarity (43 Hz, 1 ms pulse-width, 5 seconds duration, 0.25-3 mA intensity) allowing us to monitor and analyze the electrographic responses during the stimulation as well. We compared ECS-seizure-network with spontaneous seizure epileptogenic network in terms of brain regions involved and fast activity they display at seizure onset.
Results:
We included 8 out of 90 patients explored during the selected interval presenting 13 electrically induced seizures (between 1 to 3 seizures per patient). All seizures were elicited from brain areas considered to be seizure onset zone following visual analysis of spontaneous ictal discharges. Time-frequency analysis of ECS-induced seizures identified spectral changes on each contact pair recorded during ECS and enabled a better classification of the epileptogenic areas compared to time-domain visual analysis owing to stimulation artifact (Fig. 1). Regions displaying fast activity at seizure onset during stimulation overlap the regions delineated as part of the epileptogenic zone during the spontaneous seizure.
Conclusions:
High-frequency ECS activate relevant areas of the epileptogenic network to induce a habitual seizure. Alternating polarity protocol facilitates signal analysis reliably identifying electrographic responses during stimulation such as slow-potential shifts and fast discharges, a marker of epileptogenicity.
Funding: none