Cortico-cortical evoked potential by single-pulse electrical stimulation is a generally safe procedure.

Objective: Cortico-cortical evoked potential (CCEP) by single-pulse electrical stimulation (SPES) is useful to investigate effective connectivity and cortical excitability. We aimed to clarify the safety of CCEPs.
Methods: We retrospectively analyzed 29 consecutive patients with intractable partial epilepsy undergoing chronic subdural grid implantation and CCEP recording. Repetitive SPES (1 Hz) was systematically applied to a pair of adjacent electrodes over almost all electrodes. We evaluated the incidences of afterdischarges (ADs) and clinical seizures.
Results: Out of 1283 electrode pairs, ADs and clinical seizures were observed in 12 and 5 pairs (0.94% and 0.39%, per electrode pair) in 7 and 3 patients (23.3% and 10.0%, per patient), respectively. Of the 18-82 pairs per patient, ADs and clinical seizures were induced in 0-4 and 0-3 pairs, respectively. Stimulating 4 SOZ (seizure onset zone) (2.5%) and 8 non-SOZ pairs (0.75%) resulted in ADs. We observed clinical seizures in stimulating 4 SOZ (2.5%) and 1 non-SOZ pair (0.09%). The incidence of clinical seizures varied significantly between SOZ and non-SOZ stimulations (p = 0.001), while the difference in AD incidence tended towards significance (p = 0.058).
Conclusion: Although caution should be taken in stimulating SOZ, CCEP is a safe procedure for presurgical evaluation.
Significance: CCEP is safe under the established protocol.
Competing Interests: Declaration of Competing Interest Department of Epilepsy, Movement Disorders and Physiology (Kyoto University Graduate School of Medicine) is the Industry-Academic Collaboration Courses, supported by Eisai Co., Ltd., NIHON KOHDEN CORPORATION, Otsuka Pharmaceutical Co., and UCB Japan Co., Ltd.
(Copyright © 2021 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.)