What is a classification essay?

Abstract

Schoolchildren occasionally are given an assignment called a "classification essay." Advice can be found on the web (Spinello, 2009) giving the characteristics of a good classification scheme. First, it arranges items into a relevant and constructive set of categories, not too many and not too few. Second, the classification should be based upon a consistent organizing theory. Third, the scheme should be illustrated with pertinent examples. The 1981 classification of types of seizures (Commission, 1981) partitioned seizures into a manageable number of categories, organized around clinical and electroencephalographic patterns. It had its flaws. Many seizures did not fit cleanly into the categories. Lines between partial and generalized seizures often were blurred, for example, in patients with multifocal and secondarily generalized seizures. Distinguishing simple from complex partial seizures required analyzing the patient's state of "consciousness," which could not easily be measured, if at all. The current proposal for classification of epileptic seizures and syndromes has emerged from more than 5 years of intense thought and debate. Classification of epilepsy syndromes has not changed substantially from the 1989 scheme (Commission, 1989). The classification of seizures has changed, and probably is an improvement over the 1981 system. However, the new seizure classification system presents some challenges of its own. Focal seizures are now a single category, with no specific subcategories. This seems too few. Describing focal seizures in the new system requires extensive free text. Supplying relevant free text requires expertize, and makes future research and comparisons difficult, as anyone knows who has tried to perform research on a free text database. Of course, free text entry is a superior approach to use of categories that are applied incorrectly by many users. I would have preferred a subcategorization that retained the simple and complex distinction, but based it upon measurable attributes, such as awareness, responsiveness, memory loss, and arrest or production of motor activity. Consciousness would not be a criterion. Retaining the distinction between simple and complex partial seizures would assist determination of whether seizures are disabling or nondisabling. Many antiepileptic drug or device trials now de facto use the concept of disabling seizures as part of the entry criteria. Retention of the complex partial category, defined by measurable attributes, also would be of use to those who are trying to relate the seizure type to advisable or inadvisable life activities. The second difficulty involves drawing lines between focal and generalized seizures, where a continuum exists. How rapidly does the seizure have to engage bilaterally distributed networks before it is considered generalized? How localized must the onset be and how asymmetric must the seizure be before a generalized seizure is demoted to being a focal seizure? How important are brief behaviors or electroencephalography (EEG) changes at the start of a seizure? Seizures associated with juvenile myoclonic epilepsy may be clonic, then tonic, and then clonic again. It may not be obvious where to draw these lines, even to expert epileptologists. Definitions and classification schemes do not necessarily require ease of use in their application, but ease of use is a welcome feature. The organizing principle of this classification scheme appears to be classification based upon data and on advances in neuroscience. In my view, this is to the good, since expert opinions about seizure pathophysiology have not always been based on evidence. The problem here is that data on seizure and epilepsy pathophysiology, although far advanced from 1981, are still uncertain. A classification based upon that science currently stands as a rather sparse scaffold. If the scaffold is conceptually sound, however, structure will be added, eventually to form a stable classification scheme for clinicians and researchers. The task force is to be congratulated and thanked for starting us in that direction. Dr. Fisher is supported by the Maslah Saul MD Chair, James and Carrie Anderson Epilepsy Research laboratory and the Susan Horngren Fund. I confirm that I have read the Journal's position on issues involved in ethical publication and affirm that this report is consistent with those guidelines. I have no conflicts of interest to disclose relevant to this publication.

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Affiliated Institutions

• Stanford University US

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