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Of Cabbages and Kings: Some Considerations on Classifications, Diagnostic Schemes, Semiology, and Concepts

2003; Wiley; Volume: 44; Issue: 1 Linguagem: Inglês

10.1046/j.1528-1157.2003.09202_2.x

1528-1167

Peter Wolf,

Metabolism and Genetic Disorders

'The time has come,' the Walrus said, 'To talk of many things: Of shoes and ships and sealing-wax, of cabbages and kings, And why the sea is boiling hot, and whether pigs have wings.'Lewis Carroll, Through the Looking-Glass Discussions about classification of seizures, epilepsy and epilepsy syndromes have appeared in journals (1–8), and at many national and international meetings. A task force of the ILAE is working on the complex issues of classification, and the ongoing debate shows the high interest of the epilepsy community. At some times, this discussion seems confusing. Why is that so? Classifications are related to definitions, and it may therefore be useful first to define the meaning of "classification." This is not the same everywhere. Of three languages with a long tradition in scientific classifications, classification in French, according to Robert, means "action de distribuer par classes, par catégories; résultat de cette action: classement, division. Science de la classification: systématique, taxonomie."[Action of distributing by classes, by categories; result of this action: grouping, distribution. Science of classification: systematics, taxonomy]. Here, the usage of classification encompasses three distinct, well-defined meanings. In German, the second such language, Klassifikation has only one meaning and, unlike French, does not comprise the action of classifying (this would be called Klassifizierung or Klassifizieren). To quote Meyers, a much-used dictionary, Klassifikation means (my translation) "a systematic distribution or arrangement of, amongst others, terms, objects and phenomena in classes (groups) [and subclasses (subgroups) etc.] that are each characterized by distinct criteria." The English definition of "classification" is much less clear. According to the Oxford English Dictionary, classification signifies: (1.) The action of classifying or arranging in classes, according to common characteristics or affinities; assignment to the proper class; (2.) The result of classifying; a systematic distribution, allocation, or arrangement, in a class or classes; especially of things which form the subject matter of a science or of a methodical inquiry. The English definition of "classification" therefore comprises several ambiguous meanings. Definition includes creation of a classification system, assignment of a concept to a classification system, and assignment of an individual item to the appropriate class of an existing classification system. Most of these meanings are mixed up in the present discussion of Epilepsy classification, which leads to jumbled discussions of "shoes, ships, sealing-wax, cabbages and kings." We would perhaps benefit from a discussion using the more precise terms of French or German. Thus, what has been presented as a "semiological classification of epileptic seizures" by Lüders et al. (3,4) can in German not be called a Klassifikation at all (8), because it is not a taxonomic system. A different term is needed in German for such an arrangement (rather than "a classification"). However, English is the language in which this discussion must take place. Taxonomic, scientific classifications are not utilitarian. They are not written to be directly used by anybody, but to reflect the state of knowledge in a particular scientific field. Johns Hughlings Jackson compared a botanist's and a gardener's classification of plants. The botanist, like all scientists, needs a taxonomy; the gardener something to use in daily work. Jackson returned to this comparison in no less than five of the articles included in his Selected Writings (9), published between 1873 and 1888. He detailed his views in a chapter entitled "On Classification and on Methods of Investigation" from 1874, in which he says (I, 191f): "There are two ways of investigating diseases, and two kinds of classification corresponding thereto, the empirical and the scientific. The former is to be illustrated by the way in which a gardener classifies plants, the latter by the way in which a botanist classifies them. The former is, strictly speaking, only an arrangement. The gardener arranges his plants as they are fit for food, for ornament, etc. One of his classifications of ornamental plants is into trees, shrubs, and flowers. His object is the direct application of knowledge to utilitarian purposes. It is, so to speak, practical. The other kind of classification (the classification properly so-called) is rather for the better organization of existing knowledge, and for discovering the relations of new facts; its principles are methodical guides to further investigation. It is of great utilitarian value, but not directly." Unfortunately, the present epilepsy classification debate evidences very little of the terminological acumen displayed by Jackson. For example, Engel (10) pointed out clearly that Lüders et al. (3) had proposed not "a classification system, but rather a descriptive terminology of ictal events." The latter statement could be argued; rather, it is a kind of diagnostic guide for the bedside, an "arrangement" in Jackson's terms. But the argument then moves to a discussion of the "uses of a classification system for epilepsy," mixing scientific with utilitarian purposes, "cabbages with kings." Then a "pair of shoes" is added about the differentiation of limbic versus neocortical seizures, which has to do with the conceptualization of the seizure classification. The discussion then was topped with "sealing wax," i.e., a discussion of neonatal seizures, an issue unrelated to seizure semiology, pathophysiology, anatomy or diagnosis. Mention of neonatal seizures belongs in the age-relations section of the syndrome classification. Another example is a recent paper in this journal (7) that compares "cabbages with kings,"or a botanist's with a gardeners' classification, and finds that the latter one is more useful for the purposes of gardeners. This is obvious. We should reserve the term "classification" in epileptology to taxonomic systems, i.e., Jackson's "classifications properly so-called," and call other things something different. Criticism (11) can be directed at the ILAE Task Force's recently published proposal of a "diagnostic scheme for people with epileptic seizures and with epilepsy,"(12) but at least we did not call it a classification. The ILAE document (12) anticipates that a flexible and variable "approach to organization, categorization, and classification of seizure types will be devised for specific purposes." Properly speaking, this is a feature of a diagnostic arrangement, but not of a classification. You can have, in one system, either taxonomy or flexibility, but not both. Since we obviously need both a classification and diagnostic guides in different circumstances, each should be developed. The classification should be the backbone of the diagnostic schemes or guidelines. A classification should be as detailed and precise as is possible. Those who use it for a utilitarian purpose then need to decide how much of the available detail they need for their particular purpose. Is the current ILAE Classification of Epileptic Seizures (ICES) (13) suitable to serve as such a scientific backbone or do we need a new scheme? What really is wrong with the 1981 ICES? I believe that nothing fundamental is wrong concerning its taxonomic principles and system. Nevertheless, it is outdated. It also has a problem with the distinction of "simple" and "complex" focal seizures, depending upon the concept of consciousness. It calls "focal" seizures "partial." Furthermore, it inappropriately includes information about the interictal EEG that belongs in the syndrome classification. If a classification is outdated and imperfect, the usual response is to update and revise it. It is hard to understand why that has not yet been done, especially since the authors of the ICES (the crème de la crème of international epileptology of the time) expected a revision (13). The originators of the Classification developed it from the then novel technology of ictal video recordings. They knew that they had only a subset of seizure types on video. They also were aware that the 1981 ICES was mostly a framework, a "skeleton" which needed to be "fleshed out, and the nuances elaborated"(13). The novelty of the 1981 ICES was the approach to a seizure as an event unfolding over time, rather than a gestalt that is assessed after its completion. As a result, the classification was based upon the description of a sequence of signs and symptoms. It followed a semiological principle, by which every single sign and symptom is fully discerned and available for evaluation. At the time, we were fully aware of this change (14,15). When neurologists analyze seizures as they develop in time, we try to understand what brain phenomena are reflected in the development of the seizures. The more we understand, the more we will move from a mere semiological approach to a true semiology, i.e., an understanding of the significance of the signs and symptoms. This should be the ultimate scientific aim of our efforts at classifying seizures. The authors of the 1981 ICES were aware of this issue, but were constrained by the contemporary state of knowledge. They included some basic anatomical data in the "definition of terms" section of the ICES, and they designed the classification in a way that was open to such a development. This is perhaps the most important value of the old classification, and no newer proposal does the same. Today, our anatomical understanding of the seizure phenomena has greatly improved, not the least due to the progress achieved by sophisticated presurgical investigations to detect the anatomic substrates of seizures. We could in fact now begin to develop the ICES into a true Semiological Seizure Classification. For such a classification, the preliminary seizure descriptions of the ICES can be used, but need to become more systematic, detailed and precise. Terminology must be supplemented with descriptions of newly included seizure types such as hypermotor seizures (3), which are widely accepted today. Each description would then be followed by an indication of its anatomic significance, modified by the precision and reliability of our present knowledge about that type of seizure. Thus, the description of Jacksonian seizures could be followed by "Jacksonian seizures reflect seizure activity in the contralateral motor strip, according to the motor homunculus." Application of taxonomy can be problematic. For example, with tonic seizures, it may be difficult to distinguish focal from generalized seizures. In this case, the focal entry could read "Focal tonic seizures may remain strictly unilateral, involving a minor or major part of or the entire body half, but they may also extend bilaterally, more often in asymmetric than in symmetric fashion. In this case, differential diagnosis from generalized tonic seizures can be extremely difficult," supplemented by a corresponding entry in the section on generalized seizures. An anatomical clue does not necessarily disclose the localization of the seizure onset, but tells us only where there is seizure activity at the moment when the sign is observed: for example, "hypermotor seizures reflect seizure activity in the frontal lobes which, however, are often only secondarily involved." The detailed classification of seizures with psychic symptoms of the ICES should be retained, and again supplemented with semiological information, such as for seizures with fear or anxiety: "Fear as a direct symptom of an epileptic seizure is sudden in onset, mostly brief, usually unprovoked, and without defined object. It is often accompanied by autonomic signs such as pupil dilatation, pallor, flushing, piloerection or palpitation. It must be differentiated from fear as a reaction to a seizure or an aura. Primary ictal fear is strongly suggestive of an epileptic focus in the amygdalar nucleus or nuclei, more likely on the right." The inclusion of new seizure types can only benefit from, and should in fact pass through a rigorous procedure similar to the 1989 ICES where the Commission on Classification and Terminology reviewed videotaped seizures before acknowledging any type. Any revision of the syndrome classification would certainly require efforts similar to those formulating the 1985 Classification Proposal (16), in which every candidate syndrome at a three-day meeting was proposed by a presenter reviewing the literature, and then critically discussed. This would include new attempts at conceptualization, such as the recent proposal by Andermann and Berkovic (5). The kind of sifting a commission has to do when dealing with this part of the classification can be demonstrated by the differences between the "Guide bleu" of 1985 (17) and the Commission's document (16), both of which are based on the same meeting. This exercise needs to be done with the proposed syndrome diagnostic scheme (12). The distinction made by the 1989 ILAE Classification of Syndromes (18) between localization-related and generalized epilepsies has been questioned. This distinction probably is only of temporary use. "Generalized" has different meanings in the Seizure and the Syndrome Classification, and within each of them (19). The discussion of the regionality of both localization-related and "generalized" epilepsies (20) relates to this question, as well as more recent reflections upon the role of central nervous subsystems in "generalized" epilepsies (21). This is probably the direction in which the discussion will develop, eventually leading to an understanding that will supplant the need for a "generalized epilepsies and syndromes" category. Our current understanding of the pathophysiology and anatomy of "generalized" epilepsies is not yet adequate to replace this blurred concept by something more appropriate.