Predictors of Nonconvulsive Seizure and Their Effect on Short-term Outcome

Nonconvulsive seizures (NCSs) are common in critically ill adult patients with acute neurologic conditions. However, the effect of NCSs on patient outcome remains unclear. In this study, we aimed to determine the effect of NCSs on short-term outcome and to assess the clinical and EEG factors associated with NCSs.

We retrospectively identified 219 adult patients from the EEG reporting system who underwent continuous EEG (cEEG) monitoring between January 2018 and June 2018. Patients with anoxic brain injury were excluded from the study. Clinical, laboratory, and EEG data were reviewed to determine potentially predictive factors of NCSs. The impact of NCSs on in-hospital mortality, length of stay, and disability on discharge was measured; an modified Rankin scale of three or greater was considered disabled.

Of the 219 patients included in our study, a total of 14% (n = 31) had NCSs on continuous EEG, of which 42% (n = 13) had their first seizure discharge recorded during the first hour of continuous EEG monitoring. The presence of clinical seizures before continuous EEG (odds ratio = 1.787; 95% confidence interval = 1.197-2.667, P = 0.0045), history of epilepsy (odds ratio = 1.508; 95% confidence interval = 1.027-2.215, P = 0.035), and comatose state (29 vs. 16%; P = 0.0006) were associated with NCSs. Among EEG characteristics, the presence of interictal epileptiform discharges (P < 0.0001), lateralized rhythmic delta activity (P = 0.02), and lateralized periodic discharges (P < 0.0001) were associated with NCSs. Nonconvulsive seizures were significantly associated with longer in-hospital stay (23.68 ± 24.84 vs. 17.14 ± 20.52; P = 0.036) and disability on discharge (87% [n = 27] vs. 13% [n = 4], P = 0.02). However, there was no significant association between NCS and in-hospital mortality (9.6% [n = 3] vs. 10.6% [n = 20]; P = 0.1).

Nonconvulsive seizures are associated with longer in-hospital stay and disability on discharge but not with in-hospital mortality in adult patients.