Onset of intractability and its course over time: The Dutch study of epilepsy in childhood

Purpose: Intractability in epilepsy is difficult to define, and little is known about its onset, course, and duration. We investigated these aspects (as well as the occurrence of intractability) during long-term follow-up in patients with epilepsy, focusing on possible explanations for the variation in time of onset and duration of intractability. Methods: After diagnosis, 453 patients with childhoodonset epilepsy had a 5-year follow-up with regular visits and data collection. Ten years later they received a questionnaire with items concerning epilepsy, which was completed by 413 patients resulting in a mean follow-up of 15 years. Intractability during the first 5 years was compared with that in the last year of follow-up. Intractability was defined as having no 3-month remission during a 1-year period despite adequate medical treatment. Key Findings: At least 12.1% of the cohort had a period of intractability during the 15-year follow-up, and 8.5% were intractable in the final year. Of the patients with idiopathic etiology 4.3% had a period of intractability versus 17.0% for those with cryptogenic, and 22.6% for those with remote symptomatic etiology (p < 0.001). Other risk factors at baseline were younger age at first seizure, generalized cryptogenic/ symptomatic or localization-related symptomatic epilepsy, mental retardation Significance: There is a large unpredictable variation in time of onset, course, and duration of intractability, with a higher chance of final intractability after a poor course during the first 5 years of follow-up. The natural course of epilepsy probably best explains the variable course of intractability. The effect of medication seems to be minor.