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 after discharges (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. (c) 2021 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

Automated summary

The study on 29 patients with intractable partial epilepsy undergoing CCEP recording showed that CCEP is a safe procedure, especially when used under the established protocol. The incidence of clinical seizures varied significantly between stimulation of seizure onset zone and non-seizure onset zone, highlighting the importance of caution in stimulating SOZ.