To determine the effect of cortico-cortical evoked potentials (CCEP) on intracranial EEG (iEEG) monitoring.

CCEPs are cerebral waveforms elicited by low frequency stimulation, typically when patients are on baseline doses of medications at the beginning or the end of monitoring. CCEPs obtained at the beginning have an unknown effect on the rest of the iEEG monitoring. In this study, we investigate the effect of CCEPs on duration and seizure recording of iEEG implantation.

We retrospectively reviewed patients with epilepsy who underwent iEEG monitoring with CCEPs during the first 24 hours of admission. We also selected a control group (matched for age, gender, baseline seizure frequency, duration of epilepsy, and seizure location). For all patients, we recorded the rate of anti-seizure medication wean, time to first seizure, duration of admission, total number of seizures, total number of clinical seizures, and focal to bilateral tonic-clonic seizures (FBTC) during admission.

We identified 13 patients who underwent CCEPs on admission and 13 controls. There were no differences in medication weaning (mean dose 57.1% baseline CCEP vs 64.0% controls, P=0.49), time to first seizure (74 hrs CCEPs vs 52 hrs controls, P=0.57), total clinical seizures (6.5 vs 4.9, P=0.486), FBTCS (0.46 vs 0.62, P=0.658) and duration of implantation (226.5 hrs vs 168 hrs, P=0.336). There was a trend towards increased total seizures (mean 38.7 vs 7.8, P=0.160) and subclinical seizures (32.2 vs 2.9, P=0.179). Eight (61.5%) of the CCEP patients had a seizure during CCEPs.

CCEP stimulation does not significantly affect the monitoring duration, time until first seizure, or total number of clinical seizures. The trend towards increased total seizures and subclinical seizures in patients who had CCEPs recorded at admission suggests a potential causal relationship; however, larger cohort sizes are needed to explore this relationship further.