Epilepsy - Causes

Causes

The cause of a seizure is determined in about 28% of partial epilepsy patients. In the rest, however, epilepsy is deemed idiopathic, which means that the cause is unknown. The age of seizure onset can sometimes offer a clue. Idiopathic epilepsy is rare in children and young adults.

General Biologic Mechanisms Involved with Seizures

Epileptic seizures are triggered by abnormalities in the brain that cause a group of nerve cells in the cerebral cortex to become activated simultaneously, emitting sudden and excessive bursts of electrical energy. A seizure's effect depends 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.

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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.

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. GABA deficiencies are of particular interest to researchers in epilepsy. Researchers have recently discovered epilepsy-related genetic factors that regulate the GABA signaling system. The discovery is emphasizing the GABA's importance in the disease process.
• Serotonin's role in epilepsy is also being studied. Serotonin is a brain chemical that is important for well-being and associated behaviors (eating, relaxation, sleep). Imbalances in serotonin are also associated with depression. A 2005 study indicated that depression may be risk factor for epilepsy and that the two conditions may share common chemical pathways in the brain.
• Acetylcholine is a neurotransmitter that is important for learning and memory.