Epilepsy is caused by a number of factors that affect the brain. The cause of epilepsy is sometimes genetic and sometimes acquired but often both factors play a role.
The causes vary according to the age of onset. Seizures are classified as symptomatic, in which the cause is known, or idiopathic, in which the cause is unknown. In approximately 60 to 75 percent of epilepsy cases, no specific cause of the seizures can be identified. In the remaining 25 to 40 percent, the causes include:
- Genetic causes
- Birth injury (e.g. lack of oxygen to the brain at birth)
- Developmental disorder (e.g. brain damage to the fetus during pregnancy)
- Brain trauma (e.g. from car accidents or sports injuries)
- Infection (e.g. meningitis, encephalitis, AIDS)
- Brain tumour
- Cerebral degenerative disorder (e.g. those associated with Alzheimer's Disease)
- Substance abuse
Is epilepsy hereditary?
Some types of epilepsy have a genetic basis. In certain epilepsies, one or more inherited genes may result in the disorder.
In other cases, an inherited neurologic disorder that involves structural or chemical abnormalities in the brain can increase the risk of seizures and lead to epilepsy.
Another factor associated with a genetic cause of epilepsy is an inherited susceptibility to seizures. Each individual has a seizure threshold that determines the level at which the brain will have a seizure. Some individuals inherit a lower threshold or lower resistance to seizures resulting in a greater risk of having seizures.
The risk of a child having unprovoked seizures is one to two percent in the general population and approximately six percent if a parent has epilepsy.
Reprinted in part from Living with Epilepsy (Epilepsy Education Series, Edmonton Epilepsy Association)