Frequency and predictors of nonconvulsive seizures during continuous electroencephalographic monitoring in critically ill children

Objective: To determine the incidence, predictors, and timing of nonconvulsive seizures (NCSz) during continuous electroencephalographic monitoring (cEEG) in critically ill children. Methods: We identified critically ill children who underwent cEEG during a 4-year period. Multivariate logistic regression analysis was performed to determine variables associated with NCSz. Results: Among 117 monitored children, 44% had seizures on cEEG and 39% had NCSz. The majority of patients with seizures (75%) had purely NCSz, and 23% of patients had status epilepticus, which was purely nonconvulsive in 89% of cases. Seizures occurred immediately on cEEG initiation in 15%, within 1 hour in 50%, and within 24 hours in 80%. Those with clinical seizures prior to cEEG were more likely to have NCSz on cEEG (83%) than those without prior seizures (17%). On multivariate analysis, NCSz were associated with periodic lateralized epileptiform discharges and absence of background reactivity. Conclusions: Seizures, the majority being NCSz, are common during cEEG in critically ill children (seen in 44% of patients). Half are detected in the first hour of recording, whereas 20% are not detected until after more than 24 hours of recording. Nonconvulsive seizures are associated with periodic lateralized epileptiform discharges and absence of reactivity on cEEG. This study confirms the importance of prolonged cEEG for critically ill children as a means to detect NCSz.