Updated Classification of Epileptic Seizures: Crystal Clear or Lost in Translation?

Abstract

Updated classification of epileptic seizures: Position paper of the International League Against Epilepsy

Beniczky S, Trinka E, Wirrell E, Abdulla F, Al Baradie R, Alonso Vanegas M, Auvin S, Singh MB, Blumenfeld H, Bogacz Fressola A, Caraballo R, Carreno M, Cendes F, Charway A, Cook M, Craiu D, Ezeala-Adikaibe B, Frauscher B, French J, Gule MV, Higurashi N, Ikeda A, Jansen FE, Jobst B, Kahane P, Kishk N, Khoo CS, Vinayan KP, Lagae L, Lim KS, Lizcano A, McGonigal A, Perez-Gosiengfiao KT, Ryvlin P, Specchio N, Sperling MR, Stefan H, Tatum W, Tripathi M, Yacubian EM, Wiebe S, Wilmshurst J, Zhou D, Cross JH. Epilepsia. 2025 Jun;66(6):1804-1823. doi: 10.1111/epi.18338. Epub 2025 Apr 23. PMID: 40264351; PMCID: PMC12169392.

The International League Against Epilepsy (ILAE) has updated the operational classification of epileptic seizures, building upon the framework established in 2017. This revision, informed by the implementation experience, involved a working group appointed by the ILAE Executive Committee. Comprising 37 members from all ILAE regions, the group utilized a modified Delphi process, requiring a consensus threshold of more than two-thirds for any proposal. Following public comments, the Executive Committee appointed seven additional experts to the revision task force to address and incorporate the issues raised, as appropriate. The updated classification maintains four main seizure classes: focal, generalized, unknown (whether focal or generalized), and unclassified. Taxonomic rules distinguish classifiers, which are considered to reflect biological classes and directly impact clinical management, from descriptors, which indicate other important seizure characteristics. Focal seizures and those of unknown origin are further classified by the patient's state of consciousness (impaired or preserved) during the seizure, defined operationally through clinical assessment of awareness and responsiveness. If the state of consciousness is undetermined, the seizure is classified under the parent term, that is, the main seizure class (focal seizure or seizure of unknown origin). Generalized seizures are grouped into absence seizures, generalized tonic-clonic seizures, and other generalized seizures, now including recognition of negative myoclonus as a seizure type. Seizures are described in the basic version as with or without observable manifestations, whereas an expanded version utilizes the chronological sequence of seizure semiology. This updated classification comprises four main classes and 21 seizure types. Special emphasis was placed on ensuring translatability into languages beyond English. Its aim is to establish a common language for all health care professionals involved in epilepsy care, from resource-limited areas to highly specialized centers, and to provide accessible terms for patients and caregivers.

Commentary

Picture the following scenario: you are a junior attending sitting in a multidisciplinary epilepsy surgery conference listening to your up-to-date fellow presenting the semiology of a patient with tingling in the left face spreading to the left hand without loss of contact with the environment. The use of the term “focal preserved consciousness seizure” catches you off guard anticipating instead the fairly recently coined term “focal aware seizure,” while your mentor and senior attending sitting in the back of the room wonders what happened to the old good “sensory aura,” and John Hughlings Jackson raises an eyebrow from his hanging portrait on the wall at the disregard of his eponymous march. What a tower of Babel!

Ιn life, taxonomy is not just semantics. How would your AI-operated smartphone accurately select your next favorite song if the infinite library of options was not broken down into genres? In science, that holds true furthermore. What would chemistry be without Dmitri Mendeleev's periodic table of elements or biology without Carolus Linnaeus’ botanical and zoological nomenclature? In epilepsy in particular, the devil is in the details. For example, the difference between the presence or absence of a seizure warning prior to the convulsion can determine the appropriateness of certain pharmacologic treatments and the candidacy for presurgical evaluation. In other words, it provides a gold standard of communication, a common glossary for clinical and research purposes.

Hence, for nearly six decades, the International League Against Epilepsy (ILAE) has developed and frequently revised its classification of seizures and, in parallel, that of neonatal seizures, epilepsies, and status epilepticus. The last classification though in 2017 ¹ was met with substantial skepticism by part of the epilepsy community.^2–4 This 2025 update ⁵ aims to address these criticisms. It maintains the four main seizure classes (focal, generalized, unknown, and unclassified) but distinguishes between classifiers (ie, key terms that guide syndromic diagnosis, treatment, and prognosis) and descriptors (ie, additional information that indirectly influences decision making). Moreover, the prior motor versus nonmotor dichotomy is replaced by observable versus nonobservable manifestations (to factor in noticeable signs that are not strictly speaking motor), and the term “consciousness” replaces the previous term “awareness” (to encompass also responsiveness to recall). Importantly, the chronological sequence of semiology is taken into account (foremost to facilitate surgical candidacy evaluation, as well as to differentiate seizure mimics and identify epilepsy syndromes with characteristic phenotypes such as migrating focal seizures in infancy or hypermotor-tonic-spasms in CDKL5 deficiency disorder). Additional changes include the omission of the term “onset” in the main seizure classes (to acknowledge the blurry topography of the generation and rapid engagement of cortical/subcortical structures in the ictal discharge), the incorporation of epileptic spasms as a semiological descriptor for other seizure types beyond the generalized ones (to acknowledge the possibility of their focal origin) and the recognition of negative myoclonus as a seizure type under the generalized category. ⁵

The 2025 update ⁵ is the product of a systematic and collective deliberation of experts in adult and pediatric epileptology representing all ILAE chapters, with the additional input from the public. It follows a strict methodology based on the Delphi process with the goal to meticulously amalgamate published evidence and real-world experience related to the 2017 edition applicability and feasibility, and remediate the salient points of contention with the goal to create a practical and universally acceptable classification. In that sense, it preserves the fundamental schematic but provides a relative simplification of the 2017 version (21 seizure types compared to 63 previously), abiding by standard terminology, without resorting to archaic terms or neologisms. It strikes a descent balance between a conceptual and a utilitarian approach that could serve researchers, a wide range of health care providers, and patients/caregivers alike, without disrupting continuity from the work already conducted. It has the advantage of broad translatability across different geographical regions and different practice settings. ⁵

On the other hand, some of the prior criticisms^2–4 still linger. Despite the addition of semiological evolution, anatomofunctional information remains scanty for surgical remediation purposes. The impact of external circumstances (eg, sleep-activated and reflex seizures) or age (eg, childhood vs juvenile absence seizures) may significantly affect treatment and prognosis. There are still different classifications for neonatal seizures and status epilepticus. But many of these unresolved issues are inherent to the nature of the disease, given the substantial overlap of similar semiological features (eg, epileptic spasms) in different epilepsy culprits, and the diverse semiological and electrographic expression of epilepsies with common underlying etiology (eg, tuberous sclerosis complex), creating inevitably an everlasting lumpers versus splitters controversy. ⁶ And one cannot disregard the divergent viewpoints of the various medical professionals. For example, from a management standpoint, a pharmacist would be more interested in a crude phenomenological dichotomy of epilepsy in focal versus generalized, while a neurosurgeon may not be appeased until its exact semiological localization at a sublobar level. ⁷ Formulating an ideal classification scheme is indeed a Herculean task; even within this working group, it took seven rounds to reach consensus plus a revision task force to incorporate public feedback! ⁵

As already acknowledged both by proponents and opponents of the 2017 ILAE edition,^2–4,6 although classification of seizures and epilepsies is fundamentally based on observation of semiology, in practice, it constitutes a constellation of phenomenology and paraclinical data. And if in the past, that predominantly included the electroencephalogram, nowadays one has to factor in sophisticated imaging and laboratory (foremost genetic testing) information. The ultimate goal of this conceptual framework is to conclude what type of epilepsy the patient has and, thus, define treatment and prognosis. As technology advances, it is likely that our understanding in the field will exponentially increase in parallel. So, is this the last iteration of seizure classification? Probably not. But, in the sense that it attempts to reconcile unresolved issues by broadly engaging stakeholders and incorporating new knowledge to create consensus, is it a step forward? Most certainly! Is it going to be universally adopted by the medical community around the globe? It remains to be determined! The preliminary feedback is mixed, both in terms of the timing to proceed with a new revision, as well as with its content. ⁸

At the end of the day, what matters the most is a mutual understanding towards a common and ever-evolving goal, that of a scientifically sound and clinically meaningful organizational system for seizures and epilepsies. ⁹ In our imaginary scenario, despite their disagreements and regardless of etymology, the members of the epilepsy surgery conference should be able to accurately characterize the patient's seizure and source of epilepsy, jointly define the best course of action, and respectfully learn from each other. And only then, the portrayed John Hughling Jackson's eyebrow should peacefully rest back on its laurels.