Ictal Symmetric Tonic Extension Posturing and Postictal Generalized EEG Suppression Arising From Sleep in Children With Epilepsy

BACKGROUND: The identification of a biomarker for sudden unexpected death in epilepsy (SUDEP) has the potential to save lives. Generalized convulsive seizures and postictal generalized suppression on electroencephalography (EEG) most often precede sudden unexpected death in epilepsy (SUDEP) and are potential biomarkers. We identify the EEG and seizure characteristics associated with postictal generalized EEG suppression in children with epilepsy. METHODS: Video EEGs were reviewed for seizure type, duration and semiology, and electrographic features. To identify predictors of postictal generalized EEG suppression, we identified 40 children with generalized convulsive seizures from a group of 399 patients who experienced an electroclinical seizure during video-EEG. Seventy-seven generalized convulsive seizures with and without postictal generalized EEG suppression were anayzed. RESULTS: Age of seizure onset was older in 19 children with postictal generalized EEG suppression (mean 6.8 years old, 95% CI [4.7-8.9]) than in 21 without postictal generalized EEG suppression (3.0 years old, [1.1-4.1], P = 0.041). Postictal generalized EEG suppression occurred significantly more often from sleep than awake (point of estimate 16.67; 95% CI [0.97-32.36], P < 0.038). Shorter duration of the clonic phase (-0.76; [-1.338,-0.133], P = 0.018) was significantly associated with postictal generalized EEG suppression. Ictal symmetric tonic extension posturing significantly increased the odds of postictal generalized EEG suppression (42.94; [18.77, 67.12], P = 0.001). All 15 generalized convulsive seizures with a terminal burst-suppression pattern were followed by postictal generalized EEG suppression in contrast to 19 of 62 generalized convulsive seizures without burst-suppression (15.32, P < 0.001). CONCLUSIONS: Ictal decerebrate-like symmetric tonic extension posturing with shorter clonic phase and a terminal burst-suppression pattern identify malignant generalized convulsive seizures, associated with postictal generalized EEG suppression and a potentially increased risk of sudden unexpected death in epilepsy.