Prospective population-based study of intermittent and continuous convulsive status epilepticus in Richmond, Virginia

Purpose: Previous work suggested that there is a lower mortality for convulsive status epilepticus (SE) with intermittent seizures (intermittent SE) as opposed to SE with; continuous seizure activity (continuous SE). A plausible hypothesis to explain this difference is that the shorter ictal time in intermittent SE is responsible for the lower mortality in this group. This study investigates the relative contributions of total ictal time and SE duration to the differing mortalities of intermittent and continuous SE. Methods: Six hundred forty-five cases of prospectively identified convulsive SE were examined. Nonparametric statistical methods were used to compare continuous SE and intermittent SE variables. Multivariate logistic regression analyses were used to determine which factors were most highly associated with mortality. Intermittent SE cases were analyzed to evaluate the relative contributions of ictal time versus SE duration to mortality. Results: Intermittent SE had a significantly lower mortality than continuous SE (19.6 vs. 31.4%; p < 0.001) in adults but not in children. Intermittent and continuous SE durations did not significantly differ in adult cases but did differ in pediatric cases. Ictal time was significantly shorter than SE duration for intermittent SE in both adults and children. After adjusting for age, etiology, and SE duration, SE type (continuous SE vs. intermittent SE) was shown to have an independent effect on mortality in adults, The relative risk of mortality for continuous SE was 1.79 times that of intermittent SE (p = 0.04). After controlling for SE duration, ictal time did not significantly affect mortality in adults. Conclusions: Intermittent and continuous convulsive SE were common in both pediatric and adult populations. Intermittent SE had a significantly lower mortality than did continuous SE. This difference in mortality was not completely explained by differences in SE duration, total ictal time, etiology, or age. Further research is needed to identify the factor(s) contributing to the significant difference in mortality between intermittent SE and continuous SE.