Epilepsy is defined as the tendency to have repeated seizures which start in the brain.  A seizure can also be triggered by other medical conditions such as a heart condition.  These will need to be ruled out first before a diagnosis of epilepsy is made.

A one off (non-epileptic) seizure is actually very common.  It can be triggered by extreme events, such as a serious head injury, high temperatures or binge drinking.  As many as one in 20 people will have a one-off seizure in their life.  It does not mean they have epilepsy.

No two people experience epilepsy in exactly the same way.  For one person, epilepsy can mean complete seizure control on medication, for another person it can mean uncontrolled and frequent seizures despite medication.

Epilepsy can affect anyone, irrespective of their age, gender or background, but it is more common in childhood and in later life.

Read our Epilepsy explained guide for more comprehensive information about epilepsy.

For those with epilepsy in later life, we also have our Epilepsy and later life publication.

What is a seizure?

A seizure is a sign of a temporary disruption to the brain’s electrical activity.  Billions of brain cells pass messages to each other and these affect what we say, do, sense and feel.  If there is excessive electrical activity in the brain, these messages get mixed up, and it can cause a seizure.

There are many different types of seizures.  What happens during a seizure depends on where in the brain the disturbance starts and how quickly it spreads, if it spreads at all. Seizures vary in how often they happen and the length of time they last.  Certain types of seizures can look quite obvious whereas others may pass unnoticed except to someone who knows the person well.  It is also possible that a seizure is only noticed by the person.

Many people will have only one type of seizure but it is not unusual to have more than one.  People with severe learning disabilities often have two or more types of seizure.

Some people will only ever have seizures when asleep, called sleep seizures, others when both awake and asleep.  Your GP, epilepsy specialist nurse or neurologist will be able to tell you what type of seizure you have.

You can learn more about sleep seizures, including how to detect sleep seizures, treatment, and safety, in our Sleep seizures publication.

Recovery from a seizure varies from person to person.  Some people need several hours, sometimes even days before they feel back to normal again.  The time immediately after a seizure is called the ‘post-ictal phase’.  Read our After a seizure publication for more information about recovery from seizures.

Seizures can also be triggered by other events, including extreme trauma, rather than physical reasons.  These are called dissociative seizures, also sometimes referred to as non-epileptic seizures or non-epileptic attack disorder.   For more information, download our factsheet on Dissociative seizures.

Types of seizure

There are many different types of seizures.  Seizures are generally divided into two main types:

  • Focal (also known as partial) seizures
  • Generalised seizures


Focal seizures

Focal seizures only affect one part of the brain.  These types of seizures can sometimes be caused by a head injury, stroke, meningitis, a tumour or developmental abnormalities. Depending on the function of the affected part of the brain, this will then determine the type of focal seizure.  They can either be seizures with full awareness or limited awareness.

Types of focal seizures are:

  • Focal aware seizures (also known as simple partial seizures)
  • Focal seizures with limited awareness (also known as complex partial seizures)
  • Focal to bilateral tonic-clonic seizures (also known as secondary generalised seizures)


Generalised onset seizures (also known as generalised seizures)

Generalised seizures affect the whole of the brain.  There will always be some loss of consciousness, even if for just a fraction of a second.

The most common types include:

  • Tonic-clonic seizures
  • Absence seizures
  • Atonic seizures
  • Tonic seizures
  • Myoclonic seizures

To find out more about the different types of seizures, read our Seizures explained publication.

For more detailed information about specific seizure types and epilepsy, we have the following publications:

Seizure triggers

Not every person has a seizure trigger, many people will have seizures for no obvious reason.  There are, however, certain events that can be seizure triggers for some people, these include:

  • Forgetting to take medication or taking it too late
  • Lack of sleep and tiredness
  • Drinking alcohol, particularly binge drinking
  • Taking recreational drugs
  • High caffeine consumption, including energy drinks
  • Hormonal changes, such as during monthly period, pregnancy or menopause
  • Feeling unwell, running a fever, pain
  • Extreme temperatures
  • Stress and anxiety, sometimes even boredom or excitement
  • Missing meals
  • Dehydration
  • Flashing or flickering lights, called photosensitive epilepsy, see below

Less than three percent of people with epilepsy are affected by photosensitivity making this a rare type of epilepsy contrary to popular belief.

If affected, flashing or flickering lights, sunlight reflecting on water, dappled sunlight seen through trees, as well as repetitive patterns can all trigger a seizure.

Flashing or flickering content of television programmes or films is the most common source for photosensitive seizures.  You will be tested for photosensitivity as part of your epilepsy diagnosis, and will be told whether you have photosensitive epilepsy or not.

To find out more about seizure triggers, check out our following publications:

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