HILTON HEAD—Recent updates to the definitions of epilepsy and epileptic seizure recommended by the International League Against Epilepsy (ILAE) have stirred controversy over their implications for diagnosis.
In 2005, the ILAE proposed a definition of epilepsy as a disorder of the brain characterized by an enduring tendency to have epileptic seizures and by the neurobiologic, cognitive, psychologic, and social consequences of this condition, explained Bassel W. Abou-Khalil, MD, Director of the Vanderbilt Epilepsy Monitoring Unit and Clinical Epilepsy Program at Vanderbilt University School of Medicine in Nashville. He spoke at the university’s 38th Annual Contemporary Clinical Neurology Symposium.
The revised definition of epilepsy published in 2014 redefined epilepsy as a disease. It also allowed for the diagnosis to be based on either at least two unprovoked seizures occurring more than 24 hours apart, or one unprovoked seizure with a probability of recurrence equal to the risk of recurrence after two seizures (ie, >60%).
There are two controversies over the new definition of epilepsy. The main one hinges on the notion that epilepsy could be diagnosed after only one epileptic seizure. “We have forever considered that it takes two seizures to call it epilepsy, and now it is being suggested that one seizure plus an enduring resolution is enough,” said Dr. Abou-Khalil.
The other controversy relates to defining epilepsy as a disease. For a long time, epilepsy has been referred to as a disorder to emphasize that it encompasses many diseases. However, the term disease is better understood by the public and better conveys the seriousness of epilepsy, and thus may attract greater financial support for epilepsy research.
The Resolution of Epilepsy
The ILAE also recommended a definition of when epilepsy is no longer present. “Epilepsy is considered to be resolved for individuals who have had an age-dependent epilepsy syndrome, but are now past the applicable age. For example, in patients with ‘benign epilepsy with centrotemporal spikes,’ we know that after puberty that condition goes away, so those people are no longer considered to have epilepsy,” Dr. Abou-Khalil explained. In addition, in patients who have remained seizure-free for the past 10 years with no seizure medication for at least five years, it can also be declared that epilepsy is no longer present, he added.
Changes to Epilepsy Classification
ILAE also proposed changes to epilepsy classification. Instead of “epilepsies and epileptic syndromes,” the group suggested distinct categories of “electroclinical syndromes,” “distinctive constellations,” “epilepsies attributed to and organized by structural-metabolic causes,” and “epilepsies of unknown cause,” said Dr. Abou-Khalil. In addition, idiopathic epilepsies, which are presumed to be genetic, are now called “genetic epilepsies,” cryptogenic epilepsies have been renamed “epilepsies of unknown cause,” and symptomatic epilepsies are now called “structural/metabolic epilepsies secondary to specific structural or metabolic lesions or conditions, but which do not fit a specific electroclinical pattern.”
With the new epilepsy classification, the ILAE commission tried to provide terminology and concepts that better reflect the current understanding of epilepsy while also striving for clarity and simplicity, “and so they got rid of terms that were confusing.”
In the classification of seizures, the word “partial” was replaced with the word “focal,” and the terms “simple” and “complex” were abandoned; therefore, a “simple partial seizure” became a “focal seizure without impairment of consciousness or awareness.” Likewise, a “complex partial seizure” became a “focal seizure with impairment of consciousness or awareness,” also called a “dyscognitive seizure.”
The term “secondarily generalized seizure” was replaced with “focal seizure evolving to a bilateral convulsive seizure (involving tonic, clonic, or tonic and clonic components).” The terminology for generalized seizure types was mostly maintained, but some seizure types were added. Examples include “absence seizures with special features” such as “myoclonic absence” and “eyelid myoclonia” in the category of absence seizures and “myoclonic atonic” as well as “myoclonic tonic” in the category of myoclonic seizures.
“The new classifications should be viewed as a guide to summarize current understanding about seizures and epilepsies,” said Dr. Abou-Khalil. Most importantly, he added, the classifications should be broad and flexible enough to incorporate new information as it develops. “The ILAE recommends that future classifications should be conceptualized as a flexible, multidimensional catalog of features for organizing information about different epilepsies or seizures as appropriate for drug development, clinical and basic research, and clinical practice,” he concluded.
—Linda Peckel