We asked whether acute symptomatic status epilepticus (SE) increases the ri
sk for subsequent unprovoked seizure compared with less prolonged acute sym
ptomatic seizure. We also explored whether the risk of unprovoked seizure d
iffers by cause. We ascertained all first episodes of acute symptomatic sei
zure among residents of Rochester, Minnesota, through the Rochester Project
's records-linkage system. Information was collected on seizure duration, a
ge, sex, cause, and subsequent unprovoked seizure. At 10 years of follow-up
, the risk of unprovoked seizure was 41% for those with acute symptomatic s
eizure 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 seizu
res. Among patients with SE, the risk of unprovoked seizure was increased 1
8.8-fold for patients with anoxic encephalopathy, 7.1-fold for patients wit
h a structural cause, 3.6-fold for patients with a metabolic cause. The inc
reased 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.