What is epilepsy?

Epilepsy is a medical condition that affects a person’s brain and nervous system. When a person has two unprovoked seizures or one unprovoked seizure with the likelihood of more, they are considered to have epilepsy. Epilepsy has been shown to have a significant impact on health-related quality of life, and this impact is directly related to the frequency of seizures.1

The severity of epilepsy varies a great deal between individuals; some have infrequent seizures that can be controlled with medication, dietary therapies, surgery, or neurostimulation devices. Others with epilepsy suffer many seizures a day that are not responsive to any current therapy, despite the best available care.

Epilepsy also has a very large economic cost. A study conducted in 1995 of the indirect and direct costs of epilepsy found that treatment costs for the then estimated 2.3 million people with epilepsy exceeded $12.5 billion. According to researchers, "Epilepsy is unique in the large proportion of costs that are productivity-related, justifying further investment in the development of effective interventions."2

Learn more about epilepsy and types of epilepsy syndromes.

What is a seizure?

A seizure happens when a person’s brain cells misfire, sending too many electrical signals at once. These uncontrolled signals can cause changes in a person’s awareness, movement, or sensation. Seizures are generally described in two major groups: primary generalized seizures and focal (also known as partial) seizures. The difference between these types is in how and where they begin.

  • Primary generalized seizures begin with a widespread electrical discharge that involves both sides of the brain at once. One type of generalized seizure is the tonic-clonic seizure. It is what most people think of when they think of a convulsive seizure and was known in the past as a grand mal seizure. During this type of seizure, a person loses consciousness, muscles stiffen, and jerking movements are seen. It usually lasts from 1 to 3 minutes and can take much longer for a person to recover.

  • A focal seizure occurs when an electrical disturbance takes place in a limited area of the brain. If the seizure stays small, a person may have a funny feeling for a few seconds, like a brief intense emotion or a strange sensation in the stomach. If the seizure spreads, a person may have small spells of confusion or abnormal behavior. Sometimes small movements, like lip-smacking or hand motions, may be seen by others, or there may be larger seizures with vocalizations or larger movements, or even falls. If the seizure spreads to the entire brain, a generalized or convulsive seizure may occur, as described above.

Learn more about seizures and types of seizures.


1. Leidy NK, Elixhauser A. Seizure frequency and the health-related quality of life of adults with epilepsy. Neurology. 1999 Jul 13;53(1): 162-6. Available online at https://www.ncbi.nlm.nih.gov/pubmed/?term=10408553. Last accessed May 26, 2016.

2. Begley CE, Famulari M. The Cost of Epilepsy in the United States: An Estimate from Population-Based Clinical and Survey Data. 2000 Mar; 41(3):342-51. Available at http://www.ncbi.nlm.nih.gov/pubmed/?term=Begley+famulari. Last accessed May 26, 2016.

Authored By: 
Epilepsy Foundation SUDEP Institute
Authored Date: