Early-onset epilepsies are frequently associated with treatment resistance and complex phenotypes, including cognitive, motor, and behavioral comorbidities. Monogenetic causes play a central role, with approximately 30-40 % of cases being associated with pathogenic variants. Early genetic testing facilitates understanding of disease-specific pathomechanisms, supports prognostic assessment, and enables precision medicine approaches. 

1. What is the diagnostic yield of genetic testing in pediatric epilepsy syndromes and how long is the diagnostic delay?
2. Which genotype-phenotype-correlations can be identified, and which genotype and which clinical features are observed across groups?
3. How do genetic findings influence treatment decisions, clinical management and long-term outcomes in children with epilepsy syndromes?

A retrospective data collection and analysis was performed on a cohort of 765 patients, born between 1992 and 2024, who underwent genetic testing for epilepsy, developmental- and/or movement disorders and received care at the Department of Pediatric Neurology, University Hospital Heidelberg between 2015 and 2025. Data on demographic and clinical characteristics, genetic findings, and therapeutic implications were systematically extracted from medical records, genetic reports, and functional diagnostic findings using REDCap. Statistical analysis was conducted using R. 

A genetic diagnosis was identified in 39.6 % of the cohort. Early symptom or seizure onset, global developmental and movement disorders, and the presence of epilepsy – particularly combined generalized and focal forms – were associated with higher diagnostic yield. Genetic diagnosis was often established after a median delay of 1.8 years. In 38.9 % of genetically diagnosed cases, findings led to precision medicine-based therapeutic interventions. These results highlight the substantial clinical value of early genetic testing for treatment decision, clinical care and patient outcomes.