What is Epilepsy?

Epilepsy is a common but serious neurological condition where there is a tendency to have seizures that start in the brain. Not all seizures are due to epilepsy. Seizures can happen for many different reasons, such as diabetes or a heart condition. Here, when we use the term 'seizure' we mean epileptic seizure.
More than half a million people in the UK have epilepsy, which is around 1 in 100 people. Anyone can develop epilepsy: it happens in all ages, races and social classes. Epilepsy is most commonly diagnosed in children and people over 65. There are over 40 types of epilepsy, so just knowing that a person ‘has epilepsy’ does not tell you very much about their epilepsy and the type of seizures they have.

Causes of epilepsy
Epilepsy is due to an underlying cause but the cause can be complex. There are many possible causes and they may not always be found.
The causes of epilepsy can be put into three main groups: symptomatic, idiopathic, or cryptogenic epilepsy.

Symptomatic epilepsy
This is where there is a known cause for a person’s epilepsy such as a head injury, infections like meningitis, the brain not developing properly, a stroke, a scar or a tumour. A scan, such as Magnetic Resonance Imaging (MRI), may show the cause.
Some symptomatic epilepsy may happen because of a genetic condition such as Tuberous Sclerosis, which causes structural abnormalities in the brain and other organs.

Idiopathic epilepsy
This is when the epilepsy is likely to be due to a genetic tendency, which could have been inherited from one or both parents, or it may be from a change that happens in the person's genes before they are born.
Part of a genetic tendency to have seizures is called a seizure threshold.

Cryptogenic epilepsy
This is when the cause for a person's epilepsy has not yet been found, despite investigations.

What are seizure thresholds?
A person's seizure threshold often plays a key role in whether they will develop epilepsy. A seizure threshold is our individual level of resistance to seizures. We all have a seizure threshold and any one of us has the potential to have a seizure. However some people will be more likely to have a seizure than others.
Our seizure threshold is one part of our genetic makeup which can be passed from parent to child. So the chance of you having seizures may depend partly on whether either of your parents has epilepsy.
If you have a low seizure threshold, your brain is less resistant to seizures. So you are more likely to suddenly start having seizures for no obvious reason, than someone with a high seizure threshold.
If you have a high seizure threshold you are less likely to have a seizure. However, damage to the brain (for example from a severe head injury or an infection) could lower your seizure threshold; making a seizure more likely.