Proposed classification: Syndromes with onset at variable ages

Members of the Nosology and Definitions Task Force of the ILAE have developed four position papers on syndrome definitions at various ages. The ILAE guideline process requires obtaining feedback and comments from its members on the proposed paper. These comments from our international community will be reviewed by the working group before finalizing the paper.

Please see the Draft: ILAE Classification and Definition of Epilepsy Syndromes with Onset at a Variable Age

The manuscript will be open for comments until 15 July 2021. Please use this survey to enter your comments and they will be published below.

Thank you for your help in this important effort of the ILAE.

See all four Proposed papers for Nosology and Definitions


12 June 2021

This is a complex paper, including a lot of valuable information on different clinical pictures. However, in the section of epilepsy syndromes of different etiologies, including some syndromes in which the only clear common basis is the electroclinical correlation (meaning ictal semiology related to location) with significant variations on natural history, prognosis and response to treatment (mostly related to very different possible etiologies) seems a bit confusing. On that line, every single putative epileptogenic zone/network could be presented as a syndrome...?

Patricia Braga

12 June 2021


Nensi Manusheva

12 June 2021

Comprehensive and well thought out.

Arun Swaminathan MD

9 June 2021

We have a few concerns regarding the chapter on “The progressive myoclonus epilepsies”.

The sentence: “The severity of the condition depending on the etiology.” is not fully correct since it is known that a marked phenotype variability may occur even in siblings carrying the same gene mutations (as in subjects with Unverricht-Lundborg disease). We suggest changing this sentence with “Phenotype severity usually depends from etiology but individual genetic background as well as unknown environmental factors may make a contribution.”

In the sub-chapter on “Unverricht-Lundborg disease”, authors state that “The EEG background may be normal at onset, but progressive slowing of the background appears over time”. We do not fully agree, since in some patients, background activity can keep stable during the course of the disease and may even appear more organized many years after disease onset (Ferlazzo et al. Epilepsy Res 2007; 73:219-27). The last sentence: “This condition is differentiated from other PME’s by notable dysarthria, dysphagia and tremor” is incorrect since it does not match literature data. Subjects with Unverricht-Lundborg disease are known to have a milder phenotype as compared to other PMEs. We suggest deleting this sentence.

In the subchapter on “Lafora Disease.” We suggest adding a sentence stating that “Peculiar EPM2B mutations are associated with milder phenotype, slower progression and longer survival”.

Edoardo Ferlazzo, Sara Gasparini, Umberto Aguglia

26 May 2021

Thank you to the authors for this paper. It summarizes important aspects for the different syndromes.

Nevertheless, I am a little bit confused by the term "onset at a variable age" since the authors include syndromes which do not have a variable age. A definition of the term is not given (e.g. in which age frame variable? How many years variable in a defined syndrome?). To summarize these syndromes and differentiate those from the other two papers you might use "syndromes with onset in youth and young adulthood."

Yvonne Weber

13 May 2021

Focal epilepsy of unknown cause (FEUC) or with its former name cryptogenic focal epilepsy is an under-investigated topic despite its remarkable frequency and importance for the patients who will face anxiety about their prognosis labeled as “unknown”.

About 40% of adult-onset epilepsies are diagnosed as FEUC, thus they constitute an important subgroup among all types of epilepsies [1, 2]. Therefore, I certainly believe that this ignored but frequent heading should not be neglected in this pioneering paper to promote well-designed prospective future researches on FEUC.

Our recent study emphasized that the initial diagnosis of FEUC always needs further diagnostic evaluation such as genetic testing, immunological studies, advanced imaging which might illuminate the underlying hidden etiology in only 6.6% of patients even in a tertiary center. We also conclude that when appropriately treated, FEUC has a benign subgroup with the favorable course, lower drug resistance and higher 5 years of terminal remission rates. Clinicians must be aware of the related factors regarding drug response and long-term remission in FEUC and enlighten the patients at the pretreatment phase to give an insight into their epilepsy and diminish the anxiety of having an unclarified diagnosis.

1) Berg AT, Berkovic SF, Brodie MJ, Buchhalter J, Cross JH, van Emde BW, Engel J, French J, Glauser TA, Mathern GW, Moshé SL, Nordli D, Plouin P, Scheffer IE (2010) Revised terminology and concepts for organization of seizures and epilepsies: report of the ILAE Commission on Classification and Terminology, 2005–2009. Epilepsia 51:676–685

2) Shorvon SD (2011) The etiologic classification of epilepsy. Epilepsia 52:1052–1057

3) Atalar AÇ, Vanlı‑Yavuz EN, Yılmaz E, Bebek N, Baykan B. Long‑term follow‑up of a large cohort with focal epilepsy of unknown cause: deciphering their clinical and prognostic characteristics Journal of Neurology 2020; 267: 838-847.

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