Epilepsy Overview and Revised Classification of Seizures and Epilepsies

The classification of seizures, epilepsies, and epilepsy syndromes creates a framework for clinicians, researchers, and patients and their families. This classification has evolved over the years, and in 2017 the International League Against Epilepsy (ILAE) published an operational classification of seizures and epilepsies. Understanding this classification is important in the diagnosis, treatment, and understanding of seizures and epilepsies, including epilepsy incidence.

The 2017 ILAE classification system builds on newly formulated definitions of seizures and epilepsy. Seizure classification begins by determining whether the initial manifestations of the seizure are focal or generalized. If the onset of the seizure is missed or unclear, the seizure is of unknown onset. Focal seizures are classified according to the individual's level of awareness, the most prominent motor or nonmotor features of the seizure, and whether the focal seizure evolves to a bilateral tonic-clonic seizure. Similarly, generalized seizures are classified according to motor or nonmotor manifestations. Motor seizures are either tonic-clonic or other motor seizures. Nonmotor generalized seizures primarily refer to absence seizures. Similar to seizure classification, the epilepsies can be classified as focal or generalized. In addition, the new classification system recognizes two new categories: combined generalized and focal epilepsy and unknown epilepsy. The concept of an epilepsy syndrome has been introduced under the new classification system and refers to a cluster of features incorporating seizure types, EEG, imaging, and other features including genetics. The new classification system emphasizes the etiology of seizures and epilepsies.

The recent ILAE seizure and epilepsy classification system aims to create a framework to better classify seizures and the epilepsies. Universal adoption and implementation of this system will enable patients, their families, clinicians, and researchers to better define and treat the epilepsies. Incidence studies have not generally classified seizures and the epilepsies, and use of this classification system, which emphasizes etiology, will lead to a better understanding of epilepsy incidence.