Epilepsy Case Definition Updated

Summary and Comment |
May 6, 2014

Epilepsy Case Definition Updated

  1. Robert C. Knowlton, MD, MSPH

The International League Against Epilepsy has modified its definition with the goal of aligning with current practice.

  1. Robert C. Knowlton, MD, MSPH

The International League Against Epilepsy (ILAE) has updated the clinical definition of epilepsy, bringing the term “in concordance with common use.” In 2005, the condition was defined as two unprovoked seizures occurring more than 24 hours apart. With this update the definition now includes two additional circumstances in which epilepsy may be diagnosed: one unprovoked seizure plus a 60% or higher likelihood of additional seizures in the next 10 years (e.g., a patient who experiences a single seizure a month after having a stroke has a 60% or higher risk), or the presence of an epilepsy syndrome (e.g., a 13-year-old patient presenting with a first convulsive seizure who has an electroencephalogram consistent with juvenile myoclonic epilepsy). In addition, epilepsy may now be considered resolved if a patient has outgrown an age-dependent epilepsy syndrome or has gone 10 years without a seizure and has been off antiepileptic medications for at least 5 years. Previous definitions did not allow for epilepsy's resolution.

— Adapted from a Physician's First Watch article published April 15, 2014


This official report by the ILAE is an attempt to better characterize the difficult clinical definition of epilepsy. Making the diagnosis of epilepsy is certainly a common challenge that confronts all those who care for new-onset seizure patients. The diagnosis alone has very important life implications, and the decision to begin what could be indefinite treatment with antiseizure medication is nearly always difficult. Inclusion of patients with just one seizure but with the same relative risk for recurrent seizures as those who have had two seizures is reasonable. Assessing this risk is not easy in many instances. As the authors emphasize, “in the absence of clear information about recurrence risk, or even knowledge of such information, the default definition of two seizures applies.”

Less clear is why the term “resolved” was chosen to address the issue of when the definition of epilepsy may no longer apply, such as when a patient's seizure disorder appears to be in remission. This is an unwarranted new term to introduce, a term that the authors define as “…implies the person no longer has epilepsy, although it does not guarantee that it will not return” — which reflects precisely what is best understood by the term remission. Aside from this semantic misstep, the idea to clarify when epilepsy may no longer exist is helpful to both patients and physicians.

Editor Disclosures at Time of Publication

  • Disclosures for Robert C. Knowlton, MD, MSPH at time of publication Consultant / Advisory board Upsher-Smith Laboratories, Inc.; University of Alabama at Birmingham, Dept. of Neurology Speaker’s bureau Eisai Grant / Research support NIH-NINDS Leadership positions in professional societies Southern Epilepsy & EEG Society (Treasurer)


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