New classification proposals for epilepsy: A real advancement in the nosography of the disease?

Authors


  • Controversial Issues
    The following commentaries on the Shorvon and Berg/Scheffer articles in this issue, and the responses from Shorvon and Berg/Scheffer, were invited by the Editors-in-Chief

The classification of the epilepsies should be, as for any other clinical condition, a valid and reliable instrument for the benefit of different users. The practicing physician should find in the classification a tool for a correct management of the disease and for the interaction with others using the same language. In the hands of the health care provider, the classification should be useful in developing a comprehensive outline of the burden of the disease. The researcher should find in the classification a pragmatic instrument to investigate the causes, the pathogenic mechanisms, the treatment, and outcome of the disease. In this respect, the classification must fulfill differing and sometimes contrasting needs. The picture is complicated by our advancing knowledge and changes in the availability of diagnostic resources at the local level.

Several attempts have been made to update the classification of epilepsy and, at the same time, to adapt it to everyone’s needs. Any attempt at changing the previous classification inevitably faces a number of problems. The first and perhaps most important problem is an attempt to force cases—seen in real practice—into schematic categories that leave no room for disease variants and atypical pictures. Interestingly enough, after the first recognition of a given epilepsy syndrome, an increasing number of variants is inevitably reported in the literature. This “expansion” of the initial description may explain the loss of clear boundaries between, for example, focal and generalized seizures and between idiopathic and symptomatic epilepsies. A second problem is that the classification of a given case reflects not only the advancement of knowledge but also the quality and completeness of the diagnostic process in light of the available resources. A third problem is the need to link any new classification proposal to the preceding classifications—in order to preserve continuity and to monitor trends over time.

On this background, the new proposal by the International League Against Epilepsy (ILAE) Commission on Classification and Terminology (Berg et al., 2010; Berg & Scheffer, 2011) and the etiologic classification of epilepsy by Shorvon (2011) must be critically appraised. The new recommendations by the ILAE Commission for the classification of seizures and epilepsies represent an attempt to change the old terminology, in accordance with the technologic and scientific advances that have occurred in the last several years. The proposal highlights the obsolescence of the 1981 and 1989 seizure and epilepsy classifications and describes the new classification as a flexible multidimensional approach—a work in progress. The goals of this classification are to reflect our best knowledge, not to be arbitrary, and to “… serve the purpose of improving clinical practice and research on many levels.” However, in advancing this flexibility, the Commission has recommended that we no longer use such “sacred” terms as “idiopathic,”“symptomatic,” or “cryptogenic”—terms for which there is now consensus and perhaps a high inter-individual agreement. As a result, the new classification system seems to leave room for differing (and subjective) coding systems, which is contrary to the need to harmonize and simplify the categorization of a given case. In contrast, Shorvon’s etiologic classification focuses on causes which, in that author’s opinion, are the major determinants of the clinical course and outcome of the disease. He identifies four etiologic categories—idiopathic, symptomatic, provoked, and cryptogenic—which are discussed in light of the complexity of the underlying causal mechanisms. However, in attempting to preserve the old terminology, this classification fails to separate epilepsies with known genetic, structural, or metabolic origin from epilepsies of unknown cause. This failure could inevitably force the placement of a patient into one or the other category, even given the presence of a genuine uncertainty about the etiology of the disease. In addition, in this classification, there is no mention of the dichotomy, suggested by epidemiologists, between unprovoked seizures (a clear manifestation of epilepsy) and acute symptomatic (or provoked) seizures (intended as risk factors for, but not really a symptom of, epilepsy) (Beghi et al., 2010).

The terminology and classification of the epilepsies provide a framework for organizing and differentiating epileptic seizures and epilepsies. These two proposals are laudable because, from different perspectives, they attempt to overcome the problems posed by the changing knowledge of the causes and mechanisms of the disease and, at the same time, attempt to address the priorities of the classification users. Unfortunately, in their present formats, they cannot be reconciled because they are based on contrasting principles. Further work is thus needed before we accept one or the other proposal for practical use. In the meantime, formal procedures should be put in place to test the validity and reliability of these, or any new proposal, as compared to the existing “honored” classifications.

Disclosures

Pharmaceutical companies supporting studies (Janssen-Cilag, EISAI, Sanofi-Aventis, Sigma-Tau, UCB-Pharma, GSK) and supporting participation to scientific meetings (EISAI, Sanofi-Aventis, UCB-Pharma). I confirm that I have read the Journal’s position on issues involved in ethical publication and affirms that this report is consistent with those guidelines.

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