Natural history of treated childhood-onset epilepsy: prospective, long-term population-based study.

It is not well known how often drug resistance, a major clinical problem, occurs early or late in the course of epilepsy and how often epilepsy follows a continuous, remitting or relapsing-remitting pattern. To provide evidence if, in fact, different patterns of evolution of drug resistance and remission exist, a prospective, long-term population-based study of 144 patients followed on the average for 37.0 years (SD 7.1, median 40.0, range 11-42) since their first seizure before the age of 16 years was performed. At the end of follow-up, 67% of 144 patients were in terminal remission, on or off antiepileptic drugs. Early remission, starting within the first year of treatment, was seen in 45 patients (31%). In 23 (16%) of them, first remission continued, uninterrupted by relapse, to terminal remission. Late remission with a mean delay of 9 years was achieved by a further 72 patients (50%), including 46 (32%) patients who achieved terminal remission without any relapse and suggested, together with 23 patients, a remitting course. Following a relapse after early or late remission, 28 (19%) patients achieved terminal remission, suggesting a remitting-relapsing pattern. Altogether 20 patients (14%) did not re-enter remission, indicating a worsening course of epilepsy. Twenty-seven (19%) patients were drug-resistant from the start to the end of follow-up. In conclusion, half the patients with childhood-onset epilepsy will eventually enter terminal remission without relapse and a fifth after relapse. One-third will have a poor long-term outcome in terms of persistent seizures after remission or without any remission ever.