Objective. To assess the long-term recurrence risks after a first unprovoked seizure in childhood.
Methods. In a prospective study, 407 children who presented with a first unprovoked seizure were then followed for a mean of 6.3 years from the time of first seizure.
Results. One hundred seventy-one children (42%) experienced subsequent seizures. The cumulative risk of seizure recurrence was 29%,37%,42%, and 44% at 1,2,5, and 8 years, respectively. The median time to recurrence was 5.7 months, with 53% of recurrences occurring within 6 months, 69% within 1 year, and 88% within 2 years. Only 5 recurrences (3%) occurred after 5 years. On multivariable analysis, risk factors for seizure recurrence included a remote symptomatic etiology, an abnormal electroencephalogram (EEG), a seizure occurring while asleep, a history of prior febrile seizures, and Todd's paresis. In cryptogenic cases, the risk factors were an abnormal EEG and an initial seizure during sleep. In remote symptomatic cases, risk factors were a history of prior febrile seizures and age of onset younger than 3 years. Risk factors for late recurrences (after 2 years) were etiology, an abnormal EEG, and prior febrile seizures in the overall group and an abnormal EEG in the cryptogenic group. These are similar to the risk factors for early recurrence.
Conclusions. The majority of children with a first unprovoked seizure will not have recurrences. Children with cryptogenic first seizures and a normal EEG whose initial seizure occurs while awake have a particularly favorable prognosis, with a 5-year recurrence risk of only 21%. Late recurrences do occur but are uncommon.
Major clinical risk factors for seizures in febrile children aged 6 to 60 months.