A study of drug-resistant childhood epilepsy testing the new ILAE criteria

PURPOSE To test the new ILAE definition of drug-resistant epilepsy in a cohort study. METHODS All children younger than 14 with two or more unprovoked seizures observed at our hospital between 1994 and 2008 were included. RESULTS Five hundred and eight patients were followed for an average of 90 months (range 24-168). The probabilities of achieving seizure freedom, according to the ILAE criteria, with the first, second, third and fourth and subsequent therapeutic regimens were 65%, 29%, 27% and 21%, respectively. In the cohort, 87 patients met the criteria for drug-resistant epilepsy, which represents 19% of the treated patients (n=459) and 17% of the overall sample. The probability of meeting the criteria for drug-resistant epilepsy was 11%, 11% and 13% at 2, 6 and 10 years respectively. Sixty two percent of drug resistant cases were younger than 4 years old, 73% had an associated developmental delay and/or motor deficit, 42% had an identifiable structural cause of epilepsy and 32% had a specific epileptic syndrome. For drug-resistant patients who tried additional therapeutic regimens, the probability of achieving a seizure-free state without further recurrences was 23% and 27% at three and five years, respectively. CONCLUSIONS Compared with more stringent criteria, the new ILAE criteria classify a greater number of patients with drug-resistant epilepsy. A significantly higher proportion of cases meeting this definition subsequently enter remission. A definition of drug-resistance that includes the additional criteria of failure of a third antiepileptic drug or high seizure frequency may better identify patients with truly drug-resistant epilepsy.