Developmental and Epileptic Encephalopathy (DEE) are a heterogeneous group of neurodevelopmental disorders linked to both epilepsy and its underlying etiology, independently of epileptiform activity. The creation of a database with retrospective follow-up of a large number of patients on a national scale will enable better knowledge of specific biomarkers, and thus a better classification and understanding of the natural evolution of DEE according to their etiology. This will enable better, more personalized therapeutic management of patients, depending on etiology and the presence or absence of these biomarkers. The investigators will also be able to draw up management recommendations, which are currently non-existent.