Many are confused by the difference between the terms "seizure" and "epilepsy." A seizure is an alteration of motor function, sensation, behavior or consciousness due to an abnormal electrical discharge in the brain. It is a specific event. Epilepsy traditionally is defined as the disorder characterized by having at least two unprovoked seizures at least 24 hours apart. Therefore, a person who has had just one seizure is not said to have epilepsy. But how often does one seizure lead to epilepsy? Prior research has shown that a single generalized tonic-clonic seizure with no known cause (negative history, exam, EEG and MRI) leads to a second seizure (epilepsy) in about one-third of cases. Now a study by Hesdorffer and colleagues in the journal, Epilepsia, 2009, volume 50, page 1102, examines how often an acute symptomatic seizure leads to epilepsy. An acute symptomatic seizure was defined in this article as a seizure occurring within one week of stroke, traumatic brain injury or infection. These are not the only conditions that produce acute symptomatic seizures, but these three are common conditions for which data are available to study. Among 262 individuals with an acute symptomatic seizure, 34 (only 13%) had a subsequent additional (unprovoked) seizure over the next ten years. Individuals who had first seizures more than a week after an acute brain injury (so-called unprovoked seizures) were more likely to later have another seizure. This paper makes a good case that an acute seizure within a week of a brain injury does not reflect an "enduring predisposition" to have seizures and should not be considered to be epilepsy.

On a related topic, people may choose to use the term "seizure disorder," perhaps to minimize stigma associated with the term “epilepsy.” Unfortunately, “seizure disorder” is not clearly defined and could refer to a single seizure - never to happen again - or epilepsy, with spontaneously recurrent seizures. The term is therefore unclear and medically imprecise.

Robert S. Fisher, M.D., Ph.D.
Editor-in-Chief