Progressive slowing of clonic phase predicts postictal generalized EEG suppression

Abstract

Objective: Postictal generalized electroencephalography (EEG) suppression (PGES) is a surrogate marker of sudden unexpected death in epilepsy (SUDEP).It is still unclear which ictal phenomena lead to prolonged PGES and increased risk of SUDEP. Semiology features of generalized convulsive seizure (GCS type 1) have been reported as a predictor of prolonged PGES. Progressive slowing of clonic phase (PSCP) has been observed in GCSs, with gradually increasing inhibitory periods interrupting the tonic contractions. We hypothesized that PSCP is associated with prolonged PGES. Methods:We analyzed 90 bilateral convulsive seizures in 50 consecutive patients (21 female; age: 11-62 years, median: 31 years) recruited to video-EEG monitoring. Five raters, blinded to all other data, independently assessed the presence of PSCP. PGES and seizure semiology were evaluated independently. We determined inter-rater agreement (IRA) for the presence of PSCP, and we evaluated its association, as well as that of other ictal features, with the occurrence of PGES, prolonged PGES (≥20 s) and very prolonged PGES (≥50 s) using multivariate logistic regression analysis. Results: We found substantial IRA for the presence of PSCP (percent agreement: 80%; beyond-chance agreement coefficient: .655). PSCP was an independent predictor of the occurrence of PGES and prolonged PGES (p < .001). All seizures with very prolonged PGES had PSCP. GCS type 1 was an independent predictor of occurrence of PGES (p = .02) and prolonged PGES (p = .03) but not of very prolonged PGES. Only half of the seizures with very prolonged PGES were GCS type 1.Significance: PSCP predicts prolonged PGES, emphasizing the importance of gradually increasing inhibitory phenomena at the end of the seizures. Our findings shed more light on the ictal phenomena leading to increased risk of SUDEP.These phenomena may provide basis for algorithms implemented into wearable devices for identifying GCS with increased risk of SUDEP.

Ambulatory seizure detection

“…Both biomarkers showed strong association with the presence and duration of a postictal EEG suppression (PGES), with the EMG-based algorithm predicting the presence of PGES longer than 20 s with an accuracy of 85% [42,43]. The presence of a progressive slowing of the clonic phase, which could be captures from 3D-acc, also correlated with the presence and duration of the PGES, as well as with the type of GTCS [44]. The above as well as other wearable sensors might also enable to infer from the duration of GTCS and postictal immobility, as well as the severity of postictal autonomic changes [45].…”

Energy Dynamics in Seizure Disorder: Reexamining the Sacred Disease

“…That the post-ictal milieu is functionally hyperpolarized goes a long way in explaining post-ictal generalized EEG suppression (PGES) and sudden unexplained death in epilepsy (SUDEP), two common phenomena associated with the post-ictal state for which medical science has no compelling explanation [260]. PGES, absence of normal EEG activity following seizures, is associated with immobility, respiratory depression, and alterations in consciousness [261][262][263][264][265]. ANS changes associated with seizures correlate with the appearance of PGES [266].…”