Updated ILAE Seizure Classification (2025)

Seizure Classes

Focal seizures are defined by the International League Against Epilepsy as arising within networks of a single cerebral hemisphere and may remain localized or subsequently become more widely distributed. 1
Generalized seizures are defined as seizures that rapidly involve both cerebral hemispheres and both sides of the body. 2

The ILAE classifies focal seizures according to the patient’s level of consciousness during the event: preserved consciousness (awareness and responsiveness maintained), impaired consciousness (awareness or responsiveness altered), or undetermined consciousness (state cannot be assessed). 3
Focal seizures can be further described by their onset type: motor onset (observable motor phenomena) or non‑motor onset (observable non‑motor phenomena). 1

Absence seizures are categorized as non‑motor generalized seizures. 2
Generalized tonic‑clonic seizures are identified as the classic convulsive seizure type. 3

Accurate seizure classification is essential for establishing etiologic diagnoses, selecting appropriate treatments, and providing reliable prognostic information. 1
The 2025 ILAE classification is operational and does not rely on fully elucidated fundamental mechanisms of epileptic seizures. 2