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Epilepsy is a spectrum of neurological disorders involving recurring seizures. It is also possible to have nonepileptic seizures – seizures that are not caused by an epileptic disorder. Epilepsy and seizures have many different causes.
Epilepsy is not contagious. When the cause of a person’s epilepsy is known, it is called symptomatic or secondary epilepsy. Epilepsy with unknown causes is referred to as idiopathic or cryptogenic epilepsy. Some epilepsy is inherited or due to a genetic mutation. In other cases, epilepsy is structural in origin, resulting from brain damage or abnormal brain development.
Causes of epilepsy are often linked to the person’s age at diagnosis. In infants who have seizures, the cause is usually genetic or due to brain damage that happened during pregnancy or birth. In children, the cause of epilepsy could be genetic or due to fever, infection, or brain tumor. In people over 35, most epilepsy is caused by brain damage resulting from a stroke.
Genetic causes of epilepsy
Genes are known to play a role in approximately 30 to 40 percent of epilepsy cases. About 4 percent of Americans will develop epilepsy at some point in their lives. Having a first-degree relative (parent, child, or sibling) makes you two to four times more likely to develop epilepsy. It is common for family members who have epilepsy to have different types from one another.
Many cases of epilepsy are caused by a gene mutation, usually on a gene responsible for the activity of neurons in the brain. However, many people with a genetic mutation will never have seizures or develop epilepsy – an indication that genes are not the only factor that plays a role. When a genetic mutation occurs, seizures may be the first indication of a larger set of problems.
Hereditary types of epilepsy include juvenile myoclonic epilepsy (JME), childhood absence epilepsy (CAE), generalized epilepsy with febrile seizures plus (GEFS+), photosensitive epilepsy, and focal seizures.
Some of the known genetic causes of epilepsy are: Angelman syndrome, Doose syndrome (myoclonic astatic epilepsy), Down syndrome, Lennox-Gastaut syndrome, and Panayiotopoulos syndrome (PS). Read more about other genetic causes of epilepsy.
There is an association between autism spectrum disorder (ASD) and epilepsy. Approximately one-third of people on the autism spectrum also have epilepsy. Certain genetic syndromes, including Rett’s, fragile X, Prader-Willi, and Angelman, are associated with both seizures and autism. In children on the spectrum, intellectual disability increases the risk for developing epilepsy. An estimated 20 percent of autistic children with intellectual disability develop epilepsy, while 8 percent of those without intellectual problems begin having seizures. No specific type of epilepsy or severity of seizure is associated with ASD. The relationship between autism and epilepsy is poorly understood.
Some scientists believe there may be a genetic component to all forms of epilepsy. In other words, a person who starts having seizures always had a greater genetic likelihood to do so. If this is the case, when seizures begin after a brain injury or other structural change, it may be due to both the injury or change and the person’s genetic predisposition to seizures. This theory might explain why a brain injury might that leads to epilepsy in one person might not cause epilepsy in another person.
Structural causes of epilepsy
Abnormalities in the structure or metabolism (chemical processes) of the brain can cause seizures, some of which are considered nonepileptic seizures. Structural problems may be congenital (present at birth) or caused later by brain tumors, traumatic brain injuries (TBI) including automobile crashes and violence, strokes, brain infections, or alcohol or drug abuse. In situations like these, normal brain structure is distorted or disrupted, resulting in abnormal brainwaves that trigger seizures.
Metabolic causes of epilepsy include extreme dehydration, prescribed or illegal drugs, or extremely high or low blood glucose, as in uncontrolled diabetes. Metabolic problems can deprive brain cells of the glucose they need for fuel, or lower levels of electrolytes such as sodium or potassium needed in order to function properly. The result is abnormal brainwaves that cause seizures. Inflammation, which may occur as a result of TBI or a chronic inflammatory condition such as lupus, can flood the brain with proteins that may trigger seizures.
Congenital brain damage may be caused by malnutrition, infection, trauma, or drug use during pregnancy, or it may be due to a genetic defect. Children who are born prematurely or deprived of oxygen during birth can develop brain damage that causes seizures. Many newborns outgrow their seizures after the first month, but a small number will have difficult-to-treat seizures that can be lifelong. Typically, 50 to 75 percent of children who have epilepsy will eventually achieve seizure remission. The chances for remission are higher if seizure frequency is low, seizures are well treated by anti-epileptic drugs (AEDs), and there are no underlying neurological problems.
Epilepsy with unknown causes
“Idiopathic” comes from Greek words meaning “a disease of its own kind,” and it simply means that doctors do not know the cause. Similarly, “cryptogenic” comes from Greek words meaning “hidden cause.” As many as 60 percent of all epilepsies are the result of unknown causes. Certain types of seizures may stem from a scar or irritation on the brain, but the scar is undetectable by an MRI. If your doctor cannot identify the source of your epilepsy, you will be diagnosed with idiopathic or cryptogenic epilepsy. As brain imaging techniques improve, more causes of seizures will be identified.
Is epilepsy inherited?
Yes and no. Certain genetic mutations that cause epilepsy are directly inherited, while some cases of epilepsy have no known genetic connection. However, some scientists believe that people who develop epilepsy always had a greater genetic predisposition for seizures. For instance, only 10 percent of people who suffer a traumatic brain injury (TBI) severe enough to require hospitalization develop epilepsy. Genes may be a risk factor that makes the difference between who develops seizures after a TBI and who does not.
If I have a seizure, do I have epilepsy?
Having one seizure does not mean that someone has epilepsy. In order to be diagnosed with epilepsy, a person must have had more than one seizure, and doctors must believe more seizures are likely. Some seizures are not related to epilepsy at all. Read more about how epilepsy is diagnosed.