Introduction
What is epilepsy? Is it a disease or a disorder? Is it inherited? Can it be cured? If epilepsy is due to seizures, what is a seizure? These are some of the common questions asked by people newly diagnosed with epilepsy and their caregivers.
Although epilepsy has been around for thousands of years, these deceptively simple yet important questions are not easy to answer (although I did my best to do so in my first book, Epilepsy: 199 Answers). Even now, when I give a formal presentation on epilepsy for physicians, the first few slides that define seizures and epilepsy are always difficult to prepare.
A new operational definition has been created by an International League Against Epilepsy (ILAE) task force led by Robert Fisher, MD, Director, Stanford Epilepsy Center, Stanford, California, which does a pretty good job of addressing these thorny questions.
Conceptual Definitions of Seizure and Epilepsy
In 2005, the ILAE defined a seizure as "a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain." This definition is well accepted and poses few problems from a clinical or social point of view. It has not fundamentally strayed from John Hughlings Jackson's proposition in 1870 that "A convulsion is but a symptom, and implies only that there is an occasional, an excessive, and a disorderly discharge of nerve tissue on muscles."
However, the 2005 ILAE definition of epilepsy is more problematic: "Epilepsy is a disorder of the brain characterized by an enduring predisposition to generate epileptic seizures, and by the neurobiological, cognitive, psychological and social consequences of this condition. The definition of epilepsy requires the occurrence of at least one epileptic seizure."
In this definition, the diagnosis of epilepsy requires "at least one epileptic seizure." This definition is obviously flawed: The adjective "epileptic" is necessary to define the word "seizure," in order to define the original term "epilepsy," completing an uninformative circle. In a valiant effort to acknowledge the important implications of epilepsy, the definition also includes "neurobiological, cognitive, psychological and social consequences" -- everything but the kitchen sink. The modern definition of epilepsy also dictates that "provoked" seizures, such as those caused by alcohol withdrawal, hyponatremia, or drugs, do not constitute epilepsy.
The 2005 definition of epilepsy serves in most clinical scenarios, but fails in others. For example, if a child has a seizure when exposed to flashing lights and EEG reveals a photosensitive response, this child has reflex epilepsy. Is this not epilepsy because these seizures are "provoked?" Even if one eliminates the requirement for unprovoked seizures, does this child need two clinical seizures before the diagnosis is made?
Similarly, if an adolescent experiences a first convulsion after sleep deprivation and has typical bursts of 4-6 cycles per second, and polyspike and wave on the EEG, suggesting the distinct clinical syndrome of juvenile myoclonic epilepsy, is a second clinical seizure required for the diagnosis of epilepsy? A requirement for a second seizure before making the diagnosis might unnecessarily postpone treatment, exposing the individual to the risk for injury and social fallout from another seizure.
In another scenario, what about the boy with benign rolandic epilepsy who outgrows his seizures and is now 30 years old? Does this man still have epilepsy? The current definition of epilepsy as an "enduring condition" offers no option for eventually escaping the disease and its social repercussions.