In most cases of epilepsy, a cause cannot be found. If there is an identifiable cause, it usually involves some form of brain damage.
The brain is a delicate mix of neurons (brain cells), electrical impulses and chemicals, known as neurotransmitters. Any damage has the potential to disrupt the workings of the brain and cause seizures.
There are three main categories of epilepsy:
- Symptomatic epilepsy – there is a known cause for a person’s epilepsy, such as a head injury.
- Idiopathic epilepsy – despite investigation, no apparent cause for epilepsy can be found.
- Cryptogenic epilepsy – like idiopathic epilepsy, no apparent cause can be found. However, there is strong evidence that this type of epilepsy may be the result of brain damage.
Causes of symptomatic epilepsy include:
- conditions that affect the structure of the brain, such as cerebral palsy
- drugs and alcohol misuse
- birth defects
- problems during birth which cause a baby to be deprived of oxygen, such as the umbilical cord getting twisted or compressed during labour
- infectious conditions that can damage the brain, such as meningitis
- head injuries
- brain tumours
In around 60% of cases, no cause of epilepsy is found. This may be because medical equipment is not advanced enough to spot some types of damage or because the epilepsy has a genetic cause.
Many researchers have suggested that small genetic changes in the brain could be the cause of epilepsy. Current research is looking for defects in certain genes that may affect electrical transmission in the brain.
While a number of studies have been carried out, no strong association has been found between any particular genes and the development of epilepsy.
Read more about genetics.
The term cryptogenic epilepsy is used when no definite cause for epilepsy can be found but there is strong evidence that symptoms are due to damage or disruption to the brain.
Evidence that suggests a person has cryptogenic epilepsy includes:
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Many people with epilepsy find certain circumstances or substances can trigger a seizure. These triggers include:
- lack of sleep
- alcohol, particularly binge drinking and during a hangover
- illegal drugs such as cocaine, amphetamines, ecstasy, and any opiate-based drugs such as heroin, methadone or codeine
- health conditions that cause a high temperature (fever)
- flashing lights (this is an uncommon trigger that affects only 5% of people with epilepsy, and is known as photosensitive epilepsy)
Some women may be more prone to seizures just before, during or after their period. This is because hormones released by the body during that time can affect chemicals in the brain, making seizures more likely.
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Most people with epilepsy have a seizure threshold. This is the point at which the brain’s natural resistance to seizures is passed, triggering a seizure.
People with a low seizure threshold have frequent seizures, whereas people with a high seizure threshold experience less frequent seizures and triggers will have less effect on them.