Syndromic and etiological classification predicts seizure freedom in childhood and youth onset epilepsy: A population-based study from the Norwegian Mother, Father, and Child Cohort Study.

Objective: This study was undertaken to determine the proportion of individuals with childhood and youth onset epilepsy who attain seizure freedom across seizure types, epilepsy types, etiologies, and syndromes using the latest International League Against Epilepsy (ILAE) classifications. Secondary objectives were to identify predictors of seizure freedom, evaluate time to last seizure among those achieving it, and estimate prevalence of active epilepsy.

Methods: We used data from the Norwegian Mother, Father, and Child Cohort Study, a nationwide population-based cohort of ~114 000 children born 1999-2009. Pediatric epileptologists validated and classified epilepsy cases through medical record review. Analyses included 1044 individuals with ≥12 months of follow-up. Seizure freedom was ≥12 months without seizures, with or without antiseizure medication (ASM), at end of follow-up. Predictors of seizure freedom were assessed using log-binomial regression adjusted for follow-up. Time to last seizure was analyzed using Accelerated Failure Time models. Active epilepsy at any age was defined as seizures during the preceding 2 years and/or ASM use at that age; prevalence was calculated annually from ages 0 to 18 years.

Results: Median follow-up was 10.6 years. A total of 78% achieved seizure freedom. Predictors of reduced likelihood of seizure freedom included early (<2 years) or adolescent onset, multiple seizure types, status epilepticus, developmental comorbidities, and abnormal neurologic findings. Seizure freedom was most common in focal epilepsy (84%) and least in combined generalized and focal epilepsy (26%). It was highest for unknown etiology (89%) and lowest for structural (58%) and identified genetic etiologies (54%). Favorable outcomes were seen in self-limited focal epilepsies, childhood absence epilepsy, and self-limited infantile syndromes. Developmental and epileptic encephalopathies had lower rates. Among those seizure-free, median time to last seizure was 2.0 years. Prevalence peaked at age 11 years (490 per 100 000) and varied by syndrome.

Significance: This population-based study supports the prognostic value of syndrome- and etiology-based ILAE classifications in clinical care.