Predictors and course of medically intractable epilepsy in young children presenting before 36 months of age: A retrospective, population-based study

Purpose: To determine the prevalence and identify predictors of medical intractability in children presenting with epilepsy before 36 months of age, and to assess the effect of medical intractability on long-term mortality and intellectual function. Methods: Children with newly diagnosed epilepsy before 36 months between 1980 and 2009 while resident in Olmsted County, MN, were identified. Medical records were reviewed to collect epilepsy-specific variables and long-term outcome data. Medically intractable epilepsy was defined as either (1) seizure frequency greater than every 6 months at final follow-up and failure of two or more antiepileptic drugs for lack of efficacy, or (2) having undergone epilepsy surgery after failure to respond to two or more antiepileptic drugs. Key Findings: One hundred twenty-seven children with new-onset epilepsy were identified and followed for a median of 78 months. Medically intractable seizures occurred in 35%, and significant predictors on multivariate analysis were age ≤12 months at diagnosis (odds ratio [OR] 6.76, 95% confidence interval [CI] 2.00, 22.84, p = 0.002), developmental delay at initial diagnosis of epilepsy (OR 20.03, 95% CI 3.49, 114.83, p = 0.0008), neuroimaging abnormality (OR 6.48, 95% CI 1.96, 21.40, p = 0.002), and focal slowing on initial EEG (OR 5.33, 95% CI 1.14, 24.88, p = 0.03). Medical intractability occurred early in the course in most children, being seen in 61% by 1 year, and 93% by 5 years after initial diagnosis. Mortality was higher (20% vs. 0%, p < 0.001) and intellectual outcome poorer (p < 0.001) if epilepsy was medically intractable. Significance: One third of children presenting with epilepsy before 36 months will be medically intractable, and significant predictors are identified. Medically intractable epilepsy is associated with increased mortality risk and significant intellectual disability.