ILAE Classification of Epilepsies: Its Applicability and Practical Value of Different Diagnostic Categories

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Abstract
The study was aimed at verifying the applicability of the ILAE classification and the appropriateness of the different diagnostic categories in a large series of patients with epilepsy observed by epilepsy centers. Data concerning 10,342 patients observed by a network of 14 epilepsy centers in the Lombardy region between June 1990 and June 1994 were collected by using a simple standard form and stored in a PC database. The diagnosis of epilepsy was assessed in 8,570 patients; the remaining 1,772 cases were excluded from the analysis as being affected by nonepileptic ictal events or by isolated or situation-related seizures, including febrile and neonatal convulsions. A definite syndromic diagnosis, according to the ILAE Classification criteria, was made in 7,332 (85.5%) of 8,570 cases. Atypical features were found in 995 (11.6%) cases, who were therefore classified as uncertain; 198 (2.3%) cases remained unclassified; and in the remaining 45 patients, the diagnosis was not properly codified. The seizure-control profile was found to be highly related to the syndromic diagnosis. The highest percentage of drug-resistant cases was found among patients with generalized symptomatic or cryptogenic syndromes (32.3%) and among cases with partial symptomatic epilepsy (19.8%), whereas virtually no drug-resistant cases were found among patients with idiopathic epilepsies. The ILAE classification was found satisfactory in the large majority of cases observed at tertiary centers; however, the appropriateness of its various items in identifying homogeneous subpopulations was uneven, being maximal for those syndromes defined by highly consistent electroclinical pictures. An early identification of the characteristic pictures of distinct epileptic syndromes appears to be a valuable prerequisite for diagnostic and therapeutic approaches.