Abstract Details

Title Real-Time & Passive Localization of the Epileptic Network based on Single-Pulse Electrical Stimulation: Correlation with the standard of care and surgical outcomes UPMC HBM Lab

Topic Epilepsy/Clinical Neurophysiology (EEG)

Presentation(s) S7 - Epilepsy and Clinical Neurophysiology (EEG) 1 (4:06 PM-4:18 PM)

Poster/Presentation
Number 004

Objective

To test viability of single pulse evoked potentials (SPEPs) as a biomarker of the epileptogenic zone (EZ).

Background

Drug-resistant epilepsy is often evaluated by intracranial EEG (icEEG) to localize the epileptic focus(1). The risks of icEEG increase with exposure time while also elucidating a surrogate marker of EZ, the seizure onset zone(2-6). Recent studies showed marked differences in SPEPs of physiological and pathological cortices(7, 8). Our study examines a novel SPEP-based metric, which is brief compared with the recording of seizures, suggesting it has significant clinical potential, if quantitatively validated.

Design/Methods We developed a metric, the connectivity index(CI), based on the number of evoked responses weighted by their distance from the stimulation site. This measure acted as a marker of the degree of post-synaptic excitability. The goal of the pilot matched case-control study is to compare the metric following EZ vs. non-EZ stimulations thus validating it for prospective applications.

Results Evoked responses from 3019 electrodes in 22 cases were analyzed. The CI of the EZ was higher than for control contacts (median normalized CIs 0.92 vs 0.18, p=0.0002). The evoked responses of EZ were seen at further distance than control (median normalized distance 0.96 vs. 0.62, p=0.0005). A higher non-EZ CI was observed in multifocal or poor outcome cases than in localized onsets (median CIs 0.5 vs 0.12, p = 0.04). Resection ratios of standard EZ and abnormally evoked pathologic 1-4 Hz volumes were higher in cases with good outcomes with a stronger absolute, and statistical trend, for the latter (median ratios in good outcome, 0.52 vs. 0.71 and p0.12 vs. p0.04).

Conclusions The results elucidate that CI may serve as an EZ marker while reducing the time and risk to patients in comparison with the standard of care and thus opens the door for prospective validation.

Authors/Disclosures
Tritan J. Plute PRESENTER	Mr. Plute has nothing to disclose.
Rafeed Alkawadri	No disclosure on file

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