Etiology of active epilepsy in adults: A Latin American multicenter hospital-based study

Purpose Etiologic patterns of epilepsy in low- and middle-income countries (LMICs) remain insufficiently characterized. We aimed to describe the causes and clinical features of active epilepsy in adults from seven Latin American (LA) countries using the 2017 ILAE etiologic classification. Methods We performed a retrospective multicenter case series based on medical records from 12 tertiary hospitals in Argentina, Brazil, Chile, Colombia, Ecuador, Mexico, and Uruguay (2019–2023). Adults (≥16 years) with active epilepsy, defined as at least one seizure in the past five years or ongoing antiseizure medication (ASM) use, were included. Etiology was categorized using the 2017 ILAE classification. Results A total of 3033 patients were included (mean age 32 years; 53 % women). Most had focal-onset seizures (73.5 %), and 63 % showed epileptiform EEG abnormalities. Etiology was identified in 65 % of cases and remained unknown in 35 %. Structural etiologies predominated (47 %), followed by genetic (10.5 %), infectious (5.4 %), immune (1 %), metabolic/toxic (0.8 %), and neurodegenerative (0.3 %). The most frequent structural causes were hippocampal sclerosis (25.8 %), malformations of cortical development (24.8 %), and stroke (18.6 %). Neurocysticercosis accounted for 41.6 % of infectious cases but only 2.3 % of the entire cohort. Etiologic distribution varied across countries and age groups. Conclusions In this large Latin American case series, structural etiologies were the leading identified cause of active epilepsy, while one-third-of cases remained of unknown etiology. The relatively low prevalence of neurocysticercosis contrasts with classical assumptions and highlights the need for updated, region-specific data. Population-based and incident studies remain essential to better define etiologic determinants across Latin America.