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| Epilepsy - what are the causes? |
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Reviewed by Dr Dan Rutherford, GP
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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
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| Electroencephalography (EEG) can show where in the brain the
convulsions start. |
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(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.
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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.
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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.
Alcohol abuse
May cause epilepsy as a result of the cramps associated with
delirium tremens. In certain cases, an MRI scan reveals abnormalities in the
brain, but no evidence of neurological illness. Such cases are called
cryptogenic (from Greek: kryptos = hidden).
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Based on a text by Dr Jørgen Alving, consultant
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Last updated 03.08.2005
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