High-Gain Analysis of Postictal sEEG Suppression Identifies Otherwise Invisible Multifrequency Activity, Including Persisting Ictal Discharges

(1) Although the stereo-EEG appeared suppressed postictally, the combination of direct review at ultra-high gain and spectrographic analysis identified otherwise invisible low-power activity. (2) We found intermittent high-frequency oscillatory activity, early postictal sharp activity, as well as the first report of persistent ictal discharges under apparent suppression. (3) Unmasking this activity could help explain postictal seizure-like behaviors and would challenge how the onset of the postictal state is declared.