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.