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What is Epilepsy?

Many people will have a one-off seizure at some point in their lives, but not all seizures are due to epilepsy. Seizures can happen for many different reasons, such as diabetes or a heart condition. Epilepsy is different as it is a neurological condition where there is a tendency for people to have seizures that start in the brain.

It is the most common serious neurological condition in the UK and possibly the world. One in every 131 people in the UK has epilepsy. This means that there are at least 456,000 people with epilepsy in the UK . Epilepsy is more common in children and people over 65, but anyone can develop epilepsy; it happens in all ages, races and social classes. There are over 40 types of epilepsy, so just knowing that a person ‘has epilepsy’ tells you very little information about their epilepsy and the seizures that they have.

Causes of epilepsy

Anyone can develop epilepsy: it happens in all ages, races and social classes. Epilepsy is the symptom of an underlying cause but the reasons why some people develop it are not straightforward. There are many possible causes and the cause is not always found.

A person’s seizure threshold often plays a key role in whether they will develop epilepsy. The causes of epilepsy can be put into three main groups:
  • Idiopathic (primary) epilepsy
  • Symptomatic (secondary) epilepsy
  • Cryptogenic epilepsy
  • Idiopathic epilepsy

    This is when the epilepsy is likely to be due to a genetic tendency, that could have been inherited from one or both parents, and this genetic tendency makes epileptic seizures likely to happen.

    Symptomatic Epilepsy

    This is when 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, or a scar or tumour on the brain. Brain scans, such as Magnetic Resonance Imaging (MRI), may show the cause.

    Some symptomatic epilepsies may happen because of a genetic abnormality, such as Tuberous Sclerosis, which causes structural abnormalities in the brain and other organs.

    Cryptogenic Epilepsy

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

    What are seizure thresholds?

    A seizure threshold is our individual level of resistance to seizures. We all have a seizure threshold and any of us have 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 make up which can be passed from parent to child. Therefore the chance of you having seizures may depend on the seizure thresholds of both your parents.

    Low seizure thresholds

    If you have a low seizure threshold you are more likely to suddenly start having seizures for no obvious reason, than someone with a high seizure threshold.

    High seizure thresholds

    If you have a high seizure threshold this means your brain is more resistant to seizures and so you are less likely to have one. However, damage to the brain (for example from a severe head injury or an infection) could lower your seizure threshold; making you more likely to have a seizure.

    Are all seizures the same?

    There are different types of seizures and they can happen for many reasons. Some are caused by conditions such as low blood sugar (hypoglycaemia) or a change to the way the heart is working. Some look like epileptic seizures but have a different cause. These are called non-epileptic seizures.

    What epileptic seizures all have in common is that they are sudden, short-lived and cause a change in the person’s awareness of where they are, what they are doing, their behaviour or their feelings.

    Some very young children have 'febrile convulsions' (jerking movements) when they have a high temperature. These are not the same as epileptic seizures. On this page when we use the word ‘seizure’ we mean epileptic seizure.

    The brain and epileptic seizures

    The brain is made up of millions of nerve cells which control the way we think, move and feel. The nerve cells do this by passing electrical signals to each other. In some people, these signals suddenly get interrupted and this causes a seizure (sometimes called a ‘fit’ or ‘attack’). Epileptic seizures always start in the brain.

    The brain has many different functions. Mood, memory, movement, consciousness and our senses are all controlled by the brain and can be affected if a person has a seizure. Epileptic seizures can vary greatly from one person to another. Also see: causes of epilepsy.

    How epilepsy is described

    Doctors may describe epilepsy in two ways. Firstly they may describe the type of epilepsy, and secondly, the type of seizures.

    The type of epilepsy depends on the cause of the epilepsy. For example, in 'symptomatic epilepsy' there is a known cause (such as a brain injury) and 'idiopathic epilepsy' means that the epilepsy is usually genetic or inherited. The type of seizure depends on what happens to the person during the seizure. On this page we look at the types of seizures and not the types of epilepsy.

    Some facts about seizures

    There are many different types of epileptic seizure and how seizures affect one person can be different to how they affect someone else.

    Just knowing that someone has epilepsy does not tell you what their epilepsy is like, or what seizures they have.

    Calling seizures ‘major’ or ‘minor’ does not tell you what happens to the person during the seizure. The names of seizures used here describe what happens during the seizure.

    Some people have more than one type of seizure. How often seizures happen and how long they last is usually fairly constant for each person, although this can change.

    Not all seizures involve convulsions (jerking or shaking movements). Some people have seizures when they are awake, called 'awake seizures'. Some people have seizures while they are asleep, called 'asleep seizures' (or ‘nocturnal seizures’). The names 'awake' and 'asleep' do not explain what type of seizures they are, only when they happen.

    Most epileptic seizures happen suddenly without warning, last a short time (a few seconds or minutes) and stop by themselves.

    Injuries can happen during seizures, but most people do not hurt themselves and do not need to go to hospital or see a doctor.

    Seizures and the brain

    The brain has two halves called hemispheres. Each hemisphere has four parts called lobes. Each lobe is responsible for different things such as vision, speech and emotions.

    Types of seizure

    Seizures are divided into two main types: partial seizures and generalised seizures.

    Partial (or focal) seizures

    In partial seizures the seizure starts in, and affects, just part of the brain. The seizure might a larger part of one hemisphere or just a small area in one of the lobes. Partial seizures are sometimes called ‘focal’ seizures because the seizure affects just one area or 'focus'.

    What happens during the seizure depends on where in the brain the seizure happens and what that part of the brain normally does.

    Simple partial seizures

    In simple partial seizures (SPS) a small part of one of the lobes of the brain is affected. The person is conscious (aware and alert) and will usually know that something is happening.

    SPS in the frontal lobe might include:
  • a strange feeling like a ‘wave’ going through the head
  • stiffness or twitching in part of the body (such as an arm or hand).

    SPS in the temporal lobe might include:
  • a ‘rising’ feeling in the stomach or deja vu (feeling like you've 'been here before')
  • getting an unusual smell or taste
  • a sudden intense feeling of fear or joy.

    SPS in the parietal lobe might include:
  • a feeling of numbness or tingling
  • a sensation that an arm or leg feels bigger or smaller than they actually are.

    SPS in the occipital lobe might include:
  • visual disturbances such as coloured or flashing lights
  • hallucinations (where someone sees something that isn’t there).

    Some people find their SPS quite hard to put into words. During the seizure they may feel ‘strange’ but not able to describe the feeling. This can make the seizures quite upsetting.

    SPS are sometimes called ‘warnings’ or ‘auras’ because, for some people, a SPS develops into another type of seizure. Then the SPS is a warning that another seizure is going to happen (see secondarily generalised seizures below).

    Complex partial seizures

    Complex partial seizures (CPS) affect a bigger part of one hemipshere (side) of the brain than a SPS. The person’s consciousness is affected, they may be confused, and afterwards may have no memory of the seizure. They might be able to hear you, but might not fully understand what you have said or be able to respond to you. They might make strange or repetitive movements that have no purpose (called ‘automatisms’).

    CPS often happen in the temporal lobes ('temporal lobe epilepsy') but can happen in other parts of the brain.

    CPS in the temporal lobe might include:
  • picking up objects for no reason or fiddling with clothing
  • mumbling or making chewing or lip- smacking movements
  • talking 'nonsense' or muttering, or repeating words that don't make sense
  • wandering around in a confused way.

    These CPS may start with a SPS and last about two or three minutes. CPS in the frontal lobe might include:
  • making a loud cry or scream
  • making strange postures or movements such as cycling or kicking.

    These CPS usually last around 15 - 30 seconds.
    CPS in the occipital or parietal lobes are less common than temporal or frontal lobe CPS. Like the simple partial seizures, CPS in the occipital and parietal lobes can affect the person’s vision or senses. These CPS are also brief, lasting around 15 - 30 seconds.

    During a CPS the person is confused. They might wandering around, their behaviour may look strange, and they may not be aware of what they are doing. Because of this, they may not react to you as they would normally, and may not understand how you are behaving towards them. If you speak loudly to them, they may think that you are being aggressive and so they may react aggressively towards you.

    After the seizure, they might be confused for some time, sometimes called 'post-ictal' (after seizure) confusion. It might not be very easy to tell when the seizure has ended. The person might feel tired and want to rest.

    Secondarily generalised seizures

    Sometimes partial seizures spread from one hemisphere to both hemispheres of the brain. This is called a secondarily generalised seizure because it starts as a partial seizure and then becomes generalised. When this happens the person becomes unconscious and will usually have a tonic clonic seizure. If this happens very quickly, they may not be aware that it started as a partial seizure.

    Generalised seizures

    Generalised seizures affect both sides of the brain at once and can happen without warning. The person will be unconscious (except in myoclonic seizures), even if just for a couple of seconds. Afterwards they will not remember what happened during the seizure.

    Absences (sometimes called petit mal)

    Absences are more common in children than adults, and can happen very frequently. During an absence a person becomes unconscious for a short time. They may look blank and stare or their eyelids might flutter. They will not respond to what is happening around them. For example, if they are walking they may carry on walking, but will not be aware of what they are doing.

    During typical absences, the person becomes blank and unresponsive for a few seconds. Because the seizures are so brief, they may go unnoticed. Atypical absences often lasts a bit longer than typical absences. They often have some physical movement with them such as a brief head nod.

    Tonic seizures

    In a tonic seizure the person’s muscles suddenly become stiff. If they are standing they often fall, usually backwards, and may injure the back of their head. Tonic seizures tend to be very brief and happen without warning. People usually recover quickly.

    Atonic seizures

    In an atonic seizure (or 'drop attack') the person’s muscles suddenly relax, and they become floppy. If they are standing they often fall, usually forwards, and may injure themselves. Like tonic seizures, atonic seizures tend to be brief and happen without warning. People usually recover quickly.

    Myoclonic seizures

    Myoclonic means ‘muscle jerk’. Muscle jerks are not always due to epilepsy (for example, some people have them as they fall asleep). Myoclonic seizures are brief but can happen in clusters (many happening close together in time), and often happen shortly after waking.

    Although in myoclonic seizures the person is conscious, they are classified as generalised seizures. This is because they do not usually happen on their own but alongside other seizures (such as tonic clonic seizures).

    Tonic clonic (convulsive) seizures (sometimes called grand mal)

    These are the seizures most people think of as epilepsy.
    At the start of the seizure:
  • the person becomes unconscious
  • their body goes stiff and if they are standing up they usually fall backwards
  • they may cry out
  • they may bite their tongue or cheek.

    During the seizure:
  • they jerk and shake (convulse) as their muscles relax and tighten rhythmically
  • their breathing might be affected and become difficult or sound noisy
  • their skin may change colour; and become very pale or bluish
  • they may wet themselves.

    After the seizure (once the jerking stops):
  • their breathing and colour return to normal
  • they may feel tired, confused, have a headache and want to sleep.

    Clonic seizures

    Some people have convulsive seizures but their body does not go stiff at the start. These are called clonic seizures.

    Unclassifiable seizures

    Some seizures do not easily fit into the types of seizures explained above; they might have parts of different types of seizures in them or be unique to the person having them. These seizures may be called ‘unclassifiable’.

    Status epilepticus

    An individual's seizures usually last the same length of time each time they happen, and stop by themselves. However, sometimes seizures do not stop, or one seizure follows another without the person recovering in between. If this goes on for 30 minutes or more it is called status epilepticus, or ‘status’. Status can happen in any type of seizure and the person may need to see a doctor. However, status in a tonic clonic (convulsive) seizure is a medical emergency and the person will need medical help.


    Some people’s seizures are brought on or ‘triggered’ by certain situations. Triggers can differ from person to person and include lack of sleep, stress, alcohol and flickering lights (called photosensitive epilepsy). Knowing what triggers someone’s seizures means that they might be able to avoid these situations.


    Up to 70% of people could have their epilepsy controlled with anti-epileptic drugs (AEDs). AEDs aim to prevent seizures from happening, but don't cure epilepsy.

    Some people may not get full control of their epilepsy, even though they may have had the most suitable treatment for their type of seizures. There are other ways to treat epilepsy if a person doesn't respond well to AEDs, but they are not suitable for everyone.