What causes epilepsy?

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Unknown cause ('idiopathic epilepsy')

In many cases, no cause for the seizures can be found. The abnormal bursts of electrical activity in the brain occur 'out of the blue'. It is unclear why they start, or continue to occur. Genetic (hereditary) factors may play a part in some cases. People with idiopathic epilepsy usually have no other neurological (brain) condition. Medication to control seizures usually works well.

Symptomatic epilepsy

In some cases, an underlying brain condition or brain damage causes epilepsy. Some conditions are present at birth. Some conditions develop later in life. There are many such conditions. For example: a patch of scar tissue in a part of the brain, a head injury, stroke, cerebral palsy, some genetic syndromes, growths or tumours of the brain, previous infections of the brain such as meningitis, encephalitis, etc. The condition may 'irritate' the surrounding brain cells and trigger seizures.

Some underlying conditions may cause no other problems apart from seizures. In other cases, the underlying condition may cause other problems or disabilities in addition to the seizures.

These days, with more advanced scans and tests, a cause can be found for some cases previously thought to be idiopathic (unknown cause). For example, a small piece of scar tissue in the brain, or a small anomaly of some blood vessels inside the brain. These may now be found by modern brain scanning equipment which is more sophisticated than in the past.

What triggers a seizure?

There is often no apparent reason why a seizure occurs at one time and not another. However, some people with epilepsy find that certain 'triggers' make a seizure more likely. These are not the cause of epilepsy, but may trigger a seizure on some occasions. Possible triggers include:

Stress or anxiety.
Some medicines such as anti-depressants, anti-psychotic medication (by lowering the seizure threshold in the brain).
Lack of sleep or tiredness.
Irregular meals which nay cause a low blood sugar level.
Heavy drinking, or street drugs.
Flickering lights such as from strobe lighting or video games.
Menstruation (periods).
Illnesses which cause fever such as 'flu or other infections.