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Epilepsy - what are the causes?

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Epilepsy - what are the causes?

Reviewed by Dr Dan Rutherford, GP

What causes epilepsy?

Epilepsy is caused by abnormal electric impulses in groups of nerve cells (neurons) found in the brain. For diagnostic purposes, epilepsy is divided into two main groups

Idiopathic epilepsy (From Greek idos = self.) In cases of this type, the cause is unknown. However, it is believed that attacks are caused by the lack of a particular group of chemical substances (the neurotransmitters) used to regulate the electric impulses in the brain.

There may be an hereditary (genetic) background, since epilepsy of the same type is often seen among relatives. Moreover, EEG irregularities similar to those of the patient are often seen among family members, even if they do not suffer from epilepsy - a kind of genetic mark. New research has shown that certain cases of idiopathic epilepsy are clearly hereditary, caused by chromosomal abnormality.

The patient has no other signs of neurological illness or mental defects. CT and MRI scans are normal.

Symptomatic epilepsy

Epilepsy of this type is caused by a known illness in the brain.

Epilepsy triggers

Numerous illnesses or types of brain damage can cause epilepsy. The following are the most common.

Developmental anomalies Damage occurring to the brain as it develops during the first three months of pregnancy. This can be revealed by modern MRI scans and causes many of the difficult-to-control cases in children. On the other hand, damage inflicted during delivery (cerebral palsy) is fairly uncommon.

Trauma to the skull

Unlike ordinary concussion, trauma can be so serious that the patient is admitted to a neuro-surgical ward. The possibility of epilepsy following trauma varies from 5 to 50 per cent, with the highest risk following a depressed skull fracture where the brain tissue has been partly damaged, or a gunshot wound to the head.

Blood clots (infarcts) and haemorrhages in the brain

About 10 per cent of all brain infarcts cause epilepsy.

Brain tumours

Especially slow-growing superficial tumours. Since these can be surgically removed, it is important to check for these if a patient develops epilepsy, especially if the attacks start in a limited part of the brain (focal attacks - consult the article on the types of attacks). The most important techniques are CT scans and MRI scans.

Encephalitis

Prolonged seizures and fever convulsions could induce brain damage.

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