What is epilepsy?
Most people who have found their way to this site probably already have a very good idea of what epilepsy is, but it’s still worth defining because it’s actually a bit of a coverall term for a huge range of brain conditions.
Medically speaking, doctors say that a person has epilepsy if they have at least two spontaneous seizures which happen more than 24 hours apart. This is important because a lot of healthy people can have one seizure and this does not mean that they have epilepsy.
Depending on which figures you read, it’s estimated that between about 50 and 70 million people in the world have epilepsy. It can affect people of all ages and genders, but certain types of epilepsy can be more common in particular groups of people.
What is a seizure?
Seizures can come in all shapes and sizes, but there are a few generalisations that can help us to understand what they are.
First – seizures happen when a part of the brain become over-active. Our brains work using electrical activity. This is usually very precisely controlled but, if that control fails, it can cause a seizure.
Second -seizures can involve some sort of uncontrollable change in body movement, loss of awareness or unusual sensations. These characteritics can be different and normally depend on what part of the brain is affected by the seizure.
These are very general ideas and in fact different types of seizures can be very, well, different. They can last for a few seconds or they can last for a long time. They can affect a small part of the brain or they can affect a big part of the brain. They can happen rarely or they can happen many times every day.
Usually seizures will stop by themselves within a few minutes. If seizures last for more than five minutes it is called ‘status epilepticus’ – this requires urgent medical attention to avoid possible brain damage. You can find more information about this from the charity Epilepsy Action.
What causes seizures?
When the brain is working normally, there is a delicate balance between opposing ‘excitatory’ and ‘inhibitory’ brain cells. Excitatory cells drive electrical activity and inhibitory cells reduce it. The balance between these two signals keeps brain activity within a normal, healthy range.
Sometimes, changes in the brain can cause this balance to shift in favour of the excitatory cells, leading to stronger than normal electrical activity. This can happen either if something happens to make excitation stronger, or to make inhibition weaker. If there is a big enough shift towards excitation then this can cause a seizure.
The actual reasons for this imbalance in brain activity can be very varied. The cause is often genetic, but other factors can include injury, infection or tumours in the brain. Drug and alcohol misuse can also lead to seizures.