Abstracts

Rationale: Pharmacological activation procedures are used to increase occurrence of epileptic activity in presurgical evaluation of patients with focal epilepsy. It has been shown that etomidate triggers interictal spike activity recordable using formen ovale electrodes (Pastor et al., Epilepsia 2010) subdural grids and strips and magnetoencephalography (Stefan et al., Clin Neurophysiol 2010;121(8):1220-1226). Triggering of seizures was reported only in few cases (Pastor et al., Epilepsia 2010;51(4):602-609; Pastor et al., Neuropsychiatr Dis Treat 2008;4(1):305-309). Influence of etomidate on interictal epileptic ripple activity (80-250Hz) in invasive EEG, which was shown to highly correlate with the seizure inset zone, has not yet been investigated.Methods: Invasive EEG data from four patients undergoing etomidate activation during presurgical phase II evaluation with subdural strip electrodes were investigated retrospectively. A data interval from normal invasive EEG without, from right before and immediately after etomidate activation was bandpass filtered between 80-250Hz. Ripple activity exceeding noise and consisting of at least four cycles were manually selected in the invasive EEG channel showing the clearest pattern. Topography and frequency of ripples events were calculated and compared between intervals.Results: Invasive EEG data from four patients undergoing etomidate activation during presurgical phase II evaluation with subdural strip electrodes were investigated retrospectively. A data interval from normal invasive EEG without, from right before and immediately after etomidate activation was bandpass filtered between 80-250Hz. Ripple activity exceeding noise and consisting of at least four cycles were manually selected in the invasive EEG channel showing the clearest pattern. Topography and frequency of ripples events were calculated and compared between intervals.Conclusions: Etomidate activates epileptic ripple activity. If supported by larger studies, the procedure may be helpful in patients during presurgical invasive evaluation with few or no epileptic activity after prolonged recordings.