Epilepsy is a brain disorder that results in repeated seizures.
Nerve cells (neurons) normally communicate with each other through electrical impulses. During a seizure, these impulses become overactive, causing strange sensations, emotions, and behavior, or sometimes convulsions, muscle spasms, and loss of consciousness.
Epilepsy can be considered a "spectrum disorder" because of its different causes, different seizure types, its ability to vary in severity and impact from person to person, and its range of co-existing conditions. Some people may have convulsions(sudden onset of repetitive general contraction of muscles) and lose consciousness. Others may simply stop what they are doing, have a brief lapse of awareness, and stare into space for a short period. Some people have seizures very infrequently, while other people may experience hundreds of seizures each day. There also are many different types of epilepsy, resulting from a variety of causes. Recent adoption of the term “the epilepsies” underscores the diversity of types and causes.
In general, a person is not considered to have epilepsy until he or she has had two or more unprovoked seizures separated by at least 24 hours. In contrast, a provoked seizure is one caused by a known precipitating factor such as a high fever, nervous system infections, acute traumatic brain injury, or fluctuations in blood sugar or electrolyte levels.
Risk Factors for Epilepsy
Anyone can have epilepsy. It can start at any age. In the United States, it affects about one in 100 people. 40% of those people are children under age 18.
Each year, an estimated 150,000 people are diagnosed with epilepsy. Epilepsy affects both males and females of all races, ethnic backgrounds, and ages.
Epilepsy is not contagious and is not caused by mental illness or other mental problems. Many people with epilepsy have normal or above-average intelligence. However, seizures can cause brain damage, particularly if they are severe.
Cause of Epilepsy
Epilepsy is a disorder with many possible causes. Anything that disturbs the normal pattern of neuron activity, from illness to brain damage to abnormal brain development, can lead to seizures.
Epilepsy may develop because of an abnormality in brain wiring, an imbalance of nerve signaling chemicals called neurotransmitters, or some combination of these factors. One of the most-studied neurotransmitters that plays a role in epilepsy is GABA. (gamma-aminobutyric acid) which is an inhibitory neurotransmitter. Research on GABA has led to drugs that alter the amount of this neurotransmitter in the brain or change how the brain responds to it.
About half of all seizures (50%) have no known cause. However, in other cases, the seizures are clearly linked to infection, head trauma, or other identifiable problems.
Diagnosis of Epilepsy
Doctors have developed a number of different tests to determine whether a person has epilepsy and, if so, what kind of seizures the person has. In some cases, people may have symptoms that look very much like a seizure but in fact are nonepileptic events caused by other disorders. Even doctors may not be able to tell the difference between these disorders and epilepsy without close observation and intensive testing.
Such testing may include electroencephalogram (EEG) monitoring, a brain scan, or developmental, neurological, and behavioral tests.
Other Disorders Associated with Epilepsy
In many cases, epilepsy develops as a result of brain damage from other disorders. For example, stroke, head injury, encephalitis, alcoholism, and Alzheimer's disease frequently lead to epilepsy because they alter the normal workings of the brain.
Seizures may stop once these disorders are treated successfully. However, the odds of becoming seizure-free after the primary disorder is treated are uncertain and vary depending on the type of disorder, the brain region that is affected, and how much brain damage occurred prior to treatment.
Epilepsy is associated with a variety of developmental and metabolic disorders, including cerebral palsy and autism. Epilepsy is just one of a set of symptoms commonly found in people with these disorders.
Types of Seizures
Seizures are divided into two major categories – focal seizures and generalized seizures. However, there are many different types of seizures in each of these categories. In fact, doctors have described more than 30 different types of seizures.
Seizures That are Not Due to Epilepsy
While any seizure is cause for concern, having a seizure does not by itself mean a person has epilepsy.
The first seizure experienced by an individual, febrile seizures, nonepileptic events, and eclampsia are examples of seizures that may not be associated with epilepsy.
Types of Epilepsy
Just as there are many different kinds of seizures, there are many different kinds of epilepsy. Doctors have identified hundreds of different epilepsy syndromes -- disorders characterized by a specific set of symptoms that include epilepsy. Some of these syndromes appear to be hereditary. For other syndromes, the cause is unknown. Epilepsy syndromes are frequently described by their symptoms or by where in the brain they originate.
Types of epilepsy include:
- Absence seizures (Petit Mal)
- Frontal lobe epilepsy
- Neocortical epilepsy
- Temporal lobe epilepsy (TLE)
There are many other types of epilepsy, each with its own characteristic set of symptoms. Many of these, including Lennox-Gastaut syndrome and Rasmussen's encephalitis, begin in childhood. Seizure syndromes do not, however, always appear in childhood.
Epilepsy syndromes that are easily treated, do not seem to impair cognitive functions or development, and usually stop spontaneously are often described as benign. Benign epilepsy syndromes include benign infantile encephalopathy and benign neonatal convulsions.
Other syndromes, such as early myoclonic encephalopathy, include neurological and developmental problems. However, these problems may be caused by underlying neurodegenerative processes rather than by the seizures. Epilepsy syndromes in which the seizures and/or the person's cognitive abilities get worse over time are called progressive epilepsy.
Treatment of Epilepsy
The majority of those diagnosed with epilepsy have seizures that can be controlled with drug therapies and surgery. However, as much as 30 to 40 percent of people with epilepsy continue to have seizures because available treatments do not completely control their seizures (called intractable or medication resistant epilepsy).
While many forms of epilepsy require lifelong treatment to control the seizures, for some people the seizures eventually go away. The odds of becoming seizure-free are not as good for adults or for children with severe epilepsy syndromes, but it is possible that seizures may decrease or even stop over time. This is more likely if the epilepsy starts in childhood, has been well-controlled by medication, or if the person has had surgery to remove the brain focus of the abnormal cell firing.
Many people with epilepsy lead productive lives, but some will be severely impacted by their epilepsy. Medical and research advances in the past two decades have led to a better understanding of the epilepsies and seizures.
More than 20 different medications and a variety of dietary treatments and surgical techniques (including two devices) are now available and may provide good control of seizures.
Devices can modulate brain activity to decrease seizure frequency. Advance neuroimaging can identify brain abnormalities that give rise to seizures which can be cured by neurosurgery. Even dietary changes can effectively treat certain types of epilepsy.
Research on the underlying causes of the epilepsies, including identification of genes for some forms of epilepsy, has led to a greatly improved understanding of these disorders that may lead to more effective treatments or even to new ways of preventing epilepsy in the future.
Special Risks Associated with Epilepsy
Although most people with epilepsy lead full, active lives, they are at special risk for two life-threatening conditions: status epilepticus and sudden unexplained death in epilepsy (SUDEP).
Reference: The National Institute of Neurological Disorders and Stroke
Last updated May 2, 2017