Incidence of childhood and youth epilepsy: A population‐based prospective cohort study utilizing current International League Against Epilepsy classifications for seizures, syndromes, and etiologies

OBJECTIVE: This study was undertaken to describe incidence and distribution of seizures, etiologies, and epilepsy syndromes in the general child and youth population, using the current International League Against Epilepsy (ILAE) classifications. METHODS: The study platform is the Norwegian Mother, Father, and Child Cohort Study (MoBa). Epilepsy cases were identified through registry linkages facilitated by Norway's universal health care system and mandatory reporting to the Norwegian Patient Registry. A standardized protocol guided medical record review, leading to validation of diagnoses and classification of seizures, epilepsy types, syndromes, and etiologies based on the latest ILAE criteria. RESULTS: MoBa included 111 365 participants aged 12-21 years by the end of follow-up on December 31, 2020. We identified 1053 children and youth with epilepsy (CYE). A defined epilepsy syndrome and/or identified etiology was found in 76% of CYE in this population-based study. Seizure types exhibited variation by age at onset. Focal epilepsies were predominant, occurring in 61% of CYE, whereas generalized epilepsies were identified in 24% of CYE. Standard clinical assessment identified etiology in 30% of CYE and in 55% with onset age < 2 years. Structural and identified genetic etiologies constituted 21% and 10%, respectively. Including presumed genetic and rare etiologies, 53% exhibited known etiology. A defined ILAE epilepsy syndrome was found in 53% of CYE. The cumulative incidence per 1000 children of the following ILAE epilepsy syndrome groups were as follows: self-limited epilepsies, 2.25; idiopathic generalized epilepsies, 1.75; and developmental and/or epileptic encephalopathies, 2.62. SIGNIFICANCE: Using the new ILAE classifications, this population-based childhood study provides incidences of seizures, epilepsies, and epilepsy syndromes. Half of epilepsy cases are classified as an ILAE epilepsy syndrome with its prognostic and therapeutic implications, but a substantial proportion of cases still have unknown etiology.