Epilepsy is a chronic neurological disorder in which the normal chemical and electrical activities between nerve cells in the brain (neurons) become disturbed. This disturbance causes the neurons to fire abnormally, causing seizures. In a seizure, many neurons fire at the same time, much faster than usual — up to 500 times a second. (1)
Epilepsy affects people of all ages, races, and ethnic backgrounds. According to the National Institute of Neurological Diseases and Stroke (NINDS), about 2.3 million adults and more than 450,000 children and adolescents in the United States have epilepsy.
People often think of epileptic seizures as causing muscle spasms or loss of consciousness, but some seizures can instead cause sudden emotions, sensations, or behaviors that may seem inappropriate and may not be initially recognized as caused by epilepsy.
Some people with epilepsy stare off into space or make strange sounds during a seizure. Some people may undress, laugh, or walk in circles. Depending on the part of the brain affected and the severity of the disturbance in the brain, epileptic seizures can range from relatively benign events that happen rarely to recurrent, disabling, life-threatening emergencies.
Regardless of the seizure type, a person generally must have had at least two “unprovoked” seizures at least 24 hours apart to be diagnosed with epilepsy. For a seizure to be unprovoked, it cannot have another known cause aside from the disturbed brain activities that are considered epilepsies.
In 2017, the International League Against Epilepsy (ILAE) released new epilepsy diagnostic guidelines. The ILAE is an international group of researchers and physicians whose guidelines are routinely used to assess individuals with seizures. When the group released their latest guidelines, some previously used terms from the ILAE 1989 guidelines became obsolete. This article uses the new clinical terminology. (2)
In discussing epilepsy, doctors often discuss seizure types, epilepsy types, and epilepsy syndromes.
Seizure type is classified based on the initial manifestation of the seizure as generalized, focal, or unknown, having to do with the extent of the seizure’s activity in the brain.
There are many types of seizures in each of these categories.
The symptoms of the seizures will vary depending on the part of the brain affected.
In generalized seizures, the abnormal neuronal activity spreads across both halves (“hemispheres”) of the brain. Generalized seizures have both motor (movement) and nonmotor (absence) symptoms.
People having a generalized seizure are generally not aware of their surroundings, so observers should try to be alert to the person’s safety.
Some types of generalized seizures include:
If you observe a person having an apparent seizure of any kind, do what you can to ensure the person’s safety, and make note of the time. Tonic-clonic seizures lasting more than five minutes are considered to be a medical emergency, and you should call 911 if you observe one. People having a tonic-clonic seizure may lose control of their bladder or bowels, and they will feel exhausted and sore in the period after their seizure (known as the “postictal” period).
About 60 percent of people with epilepsy have focal seizures. Focal seizures originate in one part of the brain and stay in just one hemisphere of the brain. (1)
Focal epilepsies are also known as “localization-related” epilepsies; they were previously referred to as “partial” epilepsies.
Many focal epilepsies have an “aura,” which are considered warning symptoms of an upcoming seizure. The person experiencing the aura is conscious.
As with generalized seizures, focal seizure symptoms are subdivided into motor (movement) and nonmotor (absence) symptoms. Because focal seizures only involve part of the brain, symptoms are often not as extensive as generalized seizures. Focal symptoms often involve only one side of the body instead of both.
Because some people with focal seizures may have awareness during their seizures, focal seizures are further classified by level of awareness: aware, impaired awareness, or unknown awareness.
The types of focal seizures, by level of awareness, are:
Some seizures start as a focal impaired awareness seizure and then progress to a generalized tonic-clonic seizure.
Remember, any tonic-clonic seizure lasting over five minutes should prompt a call to 911.
Generalized and Focal Seizures Some epilepsies include both focal and generalized seizures, particularly some of the syndromes of early childhood, such as Dravet syndrome and Lennox-Gastaut syndrome. Some seizures begin as a focal seizure and then spread to both sides of the brain to become a generalized tonic-clonic seizure, a characteristic that used to be called “secondarily generalized seizures,” but is now called “focal onset bilateral tonic-clonic seizures.”
Unknown if Generalized or Focal Seizures This term is used to describe epilepsies that seem like generalized seizures, even though they’re actually caused by a focal lesion of the brain. This seizure classification is also used for people who seem to have had a generalized seizure but whose diagnostic tests are inconclusive or unavailable.
The ILAE has stated that the terms “simple partial,” “complex partial,” and “secondarily generalized” were eliminated from the 2017 version because they were difficult to define pragmatically and were often used incorrectly. (2)
Doctors have described more than 30 different types of seizures. (1)
Epilepsies are often grouped by a complex set of characteristics that mark a type as a known “syndrome.” They are also sometimes described by their symptoms or by the part of the brain affected.
Hundreds of different epilepsy syndromes have been identified. (3)
Some epilepsies can co-occur with or lead to developmental delays. Other epilepsies have no effect on cognitive development.
Because different parts of the brain perform different functions, seizure activities in different parts can manifest differently.
For up to 60 percent of people with epilepsy, the cause is not known, even with a complete medical evaluation.
The 2017 ILAE classification lists six major categories of causes (known as “etiologies”) of epilepsy: genetic, structural, metabolic, immune, infectious, and unknown. (2) (The terms "idiopathic," "symptomatic," and "cryptogenic" were eliminated in 2010.) Sometimes combinations of these categories best describe the causes of seizures.
Causes of epilepsy are not the same as “triggers.” Seizure triggers don’t cause epilepsy, but they can lead to an epileptic seizure in someone who is already susceptible. Common seizure triggers include stress, sleep deprivation, dehydration or missing meals, and consumption or withdrawal from alcohol or drugs.
Epilepsies of childhood have a significant proportion of diagnoses where the cause is genetic, metabolic, or where the person was born with a structural problem with the brain. Epilepsy in adults is more likely to have been caused by structural changes acquired over time, like tumors or strokes.
A variety of tests are used to look for evidence of epilepsy and to rule out other possible causes of seizures.
One of the main tools used in the diagnosis of epilepsy is the electroencephalogram, or EEG. An EEG records the brain’s electrical activity and can reveal the abnormal electrical brain activity that causes epilepsy.
Sometimes brain imaging is done using MRI or computed tomography (CT) to look for structural abnormalities in the brain that may be causing seizures.
A person’s medical history also provides important clues to the underlying cause of seizures.
Not all seizures are caused by epilepsy. Acute neurological problems, such as a stroke or head injury, can also cause a seizure. Metabolic problems, such as hypoglycemia — a common side effect of insulin therapy — and drug intoxication, can sometimes cause seizures.
In infants and children, a high fever can cause seizures. And even stress, missing meals, or sleep deprivation can bring on seizures in some individuals.
Many of the same tests are used to diagnose nonepileptic seizures as are used to to diagnose epileptic seizures.
The first type of treatment usually offered for epilepsy is antiseizure medication, of which there are more than 20. Typically, antiseizure drugs are started at a low dose, and the dosage is gradually increased to find the proper dose for the person.
While close to half of people with epilepsy become seizure-free with drug therapy, side effects are common with epilepsy medication, often leading to a reduced quality of life.
Other possible treatments for epilepsy include brain surgery and implanted nerve stimulation devices.
From patient advocacy organizations to informational sites to social networks, there’s help and support out there for individuals with epilepsy and their families and caregivers.
The Epilepsy Foundation, for example, has comprehensive information about epilepsy and about living with epilepsy, including finding an epilepsy specialist.
MyEpilepsyTeam.com is an online social network, where people can ask questions or just get to know others living with similar challenges.