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 convul sive status epilepticus (SE) with intermittent seizures (intermittent SE) a s opposed to SE with; continuous seizure activity (continuous SE). A plausi ble 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 d uration to the differing mortalities of intermittent and continuous SE. Methods: Six hundred forty-five cases of prospectively identified convulsiv e SE were examined. Nonparametric statistical methods were used to compare continuous SE and intermittent SE variables. Multivariate logistic regressi on analyses were used to determine which factors were most highly associate d with mortality. Intermittent SE cases were analyzed to evaluate the relat ive contributions of ictal time versus SE duration to mortality. Results: Intermittent SE had a significantly lower mortality than continuou s SE (19.6 vs. 31.4%; p < 0.001) in adults but not in children. Intermitten t and continuous SE durations did not significantly differ in adult cases b ut did differ in pediatric cases. Ictal time was significantly shorter than SE duration for intermittent SE in both adults and children. After adjusti ng for age, etiology, and SE duration, SE type (continuous SE vs. intermitt ent 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 interm ittent 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 comp letely 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 cont inuous SE.