A common language of seizures and epilepsies: International League Against Epilepsy 2017 classifications.

Abstract

In 2017, an operational classification of seizures and a classification of epilepsies were adopted by the International League Against Epilepsy (ILAE).1, 2 Classification is a process of categorization by which objects, organisms, or ideas are established, differentiated and comprehended. However, we are far from a full comprehension of seizure physiology. The current ILAE classification system is thus based on clinical features rather than pathogenic mechanisms, with the rationale of providing a common language to facilitate the description of seizures. Even though this approach has been subject to criticism, it seems to be the most practical one to take until we have a better understanding of seizures.1 This operational classification is perfectly in line with the mission of the ILAE, which is to provide tools that are international, regardless of the level of expertise or access to technology of health care professionals. Thus the ILAE schematic divides seizures into three types: focal onset, generalized onset, and unknown onset.1 Focal onset seizures can be subdivided into retained- or impaired-awareness focal seizures. Both focal and generalized seizures can also be divided into motor and non-motor onset types according to the first prominent symptoms of the seizure. This more descriptive classification would probably also lower the barrier to discussion with patients and their families. The 2017 ILAE seizure classification is applicable to seizures from infancy to adulthood. It has led to substantial modifications compared to former ILAE seizure classifications. It is worth noting that certain seizure types can be categorized as more than one seizure onset group. Epileptic spasms, for example, which are more frequently observed during infancy and childhood, can be of focal, generalized, or unknown onset. Even though this will come as no surprise to most child neurologists, the current ILAE seizure classification fits notably better with our knowledge and clinical practice. In addition to seizure classification, the ILAE has published a classification of epilepsies that divides them according to three descriptive levels: seizure type, epilepsy type (four possible types: focal, generalized, combined generalized and focal, and unknown), and a third level that corresponds, when possible, to the diagnosis of an epilepsy syndrome.2 In addition to these three levels of epilepsy classification, two transversal evaluations should be considered: one related to etiology and the other to the presence of comorbidities. This should serve as a reminder to consider the underlying cause at each step of the diagnostic process, from the lowest level of classification (i.e. seizure type) to the highest level (i.e. an epilepsy syndrome).2 This is also a reminder that additional investigations are frequently needed during the diagnostic processes. In the 2017 ILAE epilepsy classification, six etiological subgroups have been defined: structural, genetic, infectious, metabolic, immune, and unknown.2 For some etiology, two subgroups can apply; in tuberous sclerosis complex, for example, a patient with epilepsy would be in both the structural and genetic subgroups. With regard to the second transversal evaluation (of comorbidities), the inclusion of this axis in the 2017 ILAE classification shows how important it is to keep in mind that epilepsy is more than a repetition of seizures.3 Some comorbidities are present at the beginning of epilepsy or even before.4 For certain comorbidities, such as intellectual disabilities, identification in clinical practice is relatively straightforward. For other, more subtle conditions, identification could be more difficult (e.g. the inattentive form of attention-deficit–hyperactivity disorder [ADHD]). ADHD is the most common psychiatric comorbidity in children with epilepsy and is observed in new onset epilepsies.5 Its accurate diagnosis and early management are important for academic achievement as well as quality of life in such patients. In addition to providing a common language and an up-to-date view of seizures and epilepsies, the 2017 ILAE classifications will serve as the basis for clinical practice and teaching, and result in improved management of children and adolescents with epilepsy.