Patient inclusion criteria:

• Diagnosis of developmental and epileptic encephalopathies
• Affiliation with, or beneficiary of, a social security scheme

Criteria for non-inclusion of patients:

• Opposition of the patient or his/her parents in the case of minors to the re-use of data for this study.
• Persons subject to a safeguard of justice measure

Inclusion criteria for controls:

• Patients who, as part of their routine health care, require an EEG examination
• Patients with sufficient follow-up to rule out a diagnosis of epilepsy, including developmental and epileptic encephalopathies
• Enrolled in or receiving social security benefits

Criteria for non-inclusion of controls :

• Patient with a neurological or extra-neurological disease that may have an impact on the child's neurological development and outcome
• Opposition of the patient or his/her parents to the re-use of data for this study
• Persons subject to a safeguard of justice measure

This composite outcome includes multiple diagnostic domains (Clinical, biological, radiological, genetic and electroencephalographic variables)

To identify patient subgroups, correlation analyses will be carried out to highlight any common clinical, biological, genetic, radiological and electroencephalographic findings.