Epilepsy - Causes

Causes

Epileptic seizures are triggered by abnormalities in the brain that cause a group of nerve cells in the cerebral cortex (gray matter) to become activated simultaneously, emitting sudden and excessive bursts of electrical energy. A seizure's effect depends in part on the location in the brain where this electrical hyperactivity occurs. Effects range from brief moments of confusion to minor spasms to loss of consciousness. In most cases of epilepsy, the cause is unknown (also called idiopathic).

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Brain Chemistry Factors

Ion Channels. Sodium, potassium, and calcium act as ions in the brain. They produce electric charges that must fire regularly in order for a steady current to pass from one nerve cell in the brain to another. If the ion channels that carry them are genetically damaged, a chemical imbalance occurs. This can cause nerve signals to misfire, leading to seizures. Abnormalities in the ion channels are believed to be responsible for absence and many other generalized seizures.

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Neurotransmitters. Abnormalities may occur in neurotransmitters, the chemicals that act as messengers between nerve cells. Three neurotransmitters are of particular interest:

• Gamma aminobutyric acid (GABA), which helps prevent nerve cells from over-firing.
• Serotonin's role in epilepsy is also being studied. Serotonin is a brain chemical that is important for well-being and associated behaviors (such as eating, relaxation, and sleep). Imbalances in serotonin are also associated with depression.
• Acetylcholine is a neurotransmitter that is important for learning and memory.

Genetic Factors

Some types of epilepsy are inherited conditions where genetics play a factor. Generalized epilepsy seizure types appear to be more related to genetic influences than partial seizure epilepsies.

Injuries to the Brain

Head Trauma. Head injuries to adults can cause epilepsy in both adults and children, with the risk highest in severe head trauma. A first seizure related to the injury can occur years later, but only very rarely. People with mild head injuries, which involve loss of consciousness for fewer than 30 minutes, have only a slight risk that lasts up to 5 years after the injury.

Oxygen Deprivation. Cerebral palsy, and other disorders caused by lack of oxygen to the brain during birth, can cause seizures in newborns and infants.

Review Date: 01/28/2011
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org).