The classification of epilepsy in ICD-11 is confusing because different levels of diagnosis are arranged in parallel, whereas causes and symptoms are lined up side by side. Three topics are required for a preliminary understanding of the origin of this confusion. The major revisions of epilepsy classification conducted by the International League Against Epilepsy (ILAE) were issued in 1989, 2010, and 2017. The classification of epilepsy adopted by ICD-11 was based on that revised by ILAE in 2010, which was not widely used because of user-unfriendliness in real-world practice and discarded before being generally accepted. The classification of epilepsy in ICD-11 was likely replaced by that based on the new version issued by ILAE in 2017. This paper provides preliminary knowledge to understand the background of the classification of epilepsy in ICD-11 and subsequently explain individual subitems included therein.
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