Risk of unprovoked seizure after acute symptomatic seizure: effect of status epilepticus.

We asked whether acute symptomatic status epilepticus (SE) increases the risk for subsequent unprovoked seizure compared with less prolonged acute symptomatic seizure. We also explored whether the risk of unprovoked seizure differs by cause. We ascertained all first episodes of acute symptomatic seizure among residents of Rochester, Minnesota, through the Rochester Project's records-linkage system. Information was collected on seizure duration, age, sex, cause, and subsequent unprovoked seizure. At 10 years of follow-up, the risk of unprovoked seizure was 41% for those with acute symptomatic seizure with SE and 13% for those without SE. Controlling for age, sex, and cause, SE increased the risk for subsequent unprovoked seizure 3.3-fold (95% confidence interval, 1.8-6.1) compared with brief acute symptomatic seizures. Among patients with SE, the risk of unprovoked seizure was increased 18.8-fold for patients with anoxic encephalopathy, 7.1-fold for patients with a structural cause, 3.6-fold for patients with a metabolic cause. The increased risk for unprovoked seizure after SE compared with shorter seizures may be due to SE being a marker for severity of injury, damage caused by SE, or a biological substrate associated with the tendency to experience SE.