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What is a Seizure?

Last updated on 3rd May 2023

According to Epilepsy Research UK, there are more than 40 different types of seizures. While many people have seizures that can be treated and controlled, around 30% of people have uncontrolled seizures that don’t respond to any medication.

In the United Kingdom, between five and ten people in every 1,000 has epilepsy according to NICE. Any person’s lifetime risk of a single seizure is between 8% and 10%. However, there is a 3% risk of epilepsy after a person has a single seizure.

So, what is a seizure exactly? Let’s take a look.

What is a seizure?

A seizure is an uncontrolled, sudden electrical disturbance somewhere in the brain. A seizure can cause a change in a person’s movements, feelings, behaviour and level of consciousness.

When a person has two or more seizures that aren’t within a 24-hour period and there is no identifiable cause, a person is usually considered to have epilepsy.

Seizures can look very different and there are many different types. Many people consider seizures as a jerking of muscles and loss of consciousness; however, this is just one type of seizure called a tonic-clonic seizure.

The type of seizure is dependent upon which part of the brain is affected. Most will last from less than a minute up to a couple of minutes. When seizures last beyond five minutes, it’s considered to be an emergency situation.

There are many causes of seizures, including illnesses like meningitis, head injury and stroke. Lots of times, the seizure has no known cause.

Girl in hospital with meningitis

What are the types of seizures?

There are lots of different types of seizures and not all involve the body jerking that most people are familiar with. Let’s explore these different types.

Focal seizures with impaired awareness

With this type of seizure, there is a loss of consciousness or a change in consciousness. Some people report feeling as though they’re in a dream. They may seem awake to the external eye, but they could be staring into space and not responding as they normally would.

There might be repetitive movements like mouth movements, hand rubbing, walking in a circle or repeating particular words and phrases. A person who has this type of seizure may not be aware that it’s happened or might not remember what happened.

Focal seizures without loss of consciousness

These seizures affect how a person feels. Their emotions might be altered and things might look different to them. It might also affect the smell, taste, feel or sound of something. However, there is no loss of consciousness.

Some people describe suddenly feeling sad, happy or angry. Others might feel nausea or a general malaise. This type of focal seizure might also mean the person might have involuntary body movements and jerking. For example, their leg or arm might move of their own accord.

This seizure type can also make people feel dizzy and see flashes of light.

Given how these seizures present, they can be confused with other neurological problems like mental illness, narcolepsy or migraine.

Absence seizures

These used to be called petit mal seizures. They often occur in children and present as staring or subtle body movements like lip smacking or blinking. These typically occur for five to ten seconds but could happen multiple times a day.

Absence seizures can occur in clusters and there could be some loss of awareness.

Tonic seizures

This type of seizure causes the muscles to stiffen. A person might lose consciousness and fall. The seizures affect muscles in the arms, legs and back typically.

Atonic seizures

These are also known as ‘drop seizures’ and they cause a person to lose control of their muscles. They might suddenly fall down, collapse or drop their head.

Clonic seizures

This type of seizure is the one most people recognise. A clonic seizure presents as a rhythmic or repeated muscle jerking. The arms, face and neck of both sides of the body are usually affected.

Myoclonic seizures

These typically appear as brief twitches or jerks that appear suddenly in the legs and arms. There is usually no loss of consciousness.

Tonic-clonic seizures

This type of seizure used to be called a grand mal seizure. These are the most dramatic seizure types. They cause a sudden loss of consciousness accompanied by a stiffening of the body and jerking movements.

With tonic-clonic seizures, the person might bite their tongue and lose control of their bladder. The seizure can occur for several minutes.

What are the signs and symptoms of a seizure?

With seizures, there are a huge range of signs and symptoms ranging from mild to severe. The symptoms will vary depending on the seizure type.

Here are some possible signs and symptoms of a seizure:

  • Staring into space.
  • Temporary confusion.
  • Involuntary jerking movements of the legs and arms.
  • Loss of awareness or consciousness.
  • Emotional or cognitive symptoms like déjà vu, anxiety and fear.

Seizures are usually classed as focal or generalised depending on where the brain activity that causes them begins. They might be described as unknown onset seizures.

Staring into space as a symptom of a seizure

What causes seizures?

A person’s brain is always at work, even when you’re sleeping. The brain controls everything – breathing, heart rate, chemical process, your thoughts, and your ability to learn new skills. Lots of the things your brain controls are voluntary actions – like reading, for example. There are also many involuntary actions like your heartbeat and it is your neurons (the brain’s nerve cells) that control everything.

Neurons communicate with one another through chemicals called neurotransmitters. These trigger electrical activity and make certain cells more active or less active. When a brain is functioning well, these neurotransmitters are quick and effective at communication. Sometimes, though, neurons won’t work as they should and so the communication is interrupted. This is when a seizure occurs.

To put it simply, when a seizure happens there is abnormal and uncontrolled electrical activity in the brain between neurons or brain cells.

Besides epilepsy (the biggest cause of seizures), there are many reasons why seizures occur.

Here are some of the most frequent causes:

  • Glucose or sodium levels in the blood aren’t normal.
  • There is a brain infection like encephalitis or meningitis.
  • There has been a brain injury or head injury (this can even happen to infants as they pass through the birth canal).
  • Congenital defects in the brain.
  • Drug abuse (and drug or alcohol withdrawal).
  • Electric shock.
  • A high temperature.
  • Heat stroke.
  • Heart disease.
  • Poisoning.
  • Pre-eclampsia.
  • Stroke.
  • Kidney or liver failure.
  • Stings or bites.

Seizures can also be unprovoked – this means there isn’t an issue or underlying condition responsible for the seizure.

Seizure triggers

When people have epilepsy, there can be triggers for their seizures. They can also occur at random.

Here are some common triggers:

  • Certain hours of the day (waking up or when asleep).
  • Being sleep deprived.
  • Being unwell.
  • Flashing lights (photosensitive epilepsy).
  • Alcohol consumption.
  • Drugs.
  • Changes in hormones.
  • Changes in diet – Dehydration or a vitamin deficiency.
  • Certain foods e.g., caffeine.
  • Missed medications.
  • Certain medicines.

For some, triggers are very specific. This is called “reflex epilepsy”. Photosensitive epilepsy is one such example.

Sometimes it can be hard to know if anything triggered a seizure and patients are often advised to track their seizures in a diary.

What are the short-term effects of seizures?

Though a seizure itself is usually a matter of minutes, there can be some short-term effects. The period following a seizure is called the postictal phase. This can last seconds to days and it is believed to happen to allow the brain to recover from the seizure.

Here are some common symptoms that occur during the postictal phase:

  • Exhaustion.
  • Fear.
  • Confusion.
  • Agitation.
  • Anxiety.
  • Embarrassment or shame.
  • Not able to respond/slow in responding.
  • Loss of memory.
  • Sadness/depression.
  • Delirium.
  • Psychosis (rare).
  • Migraine or headache.
  • Loss of control of bladder or bowel.
  • Thirst.
  • Upset stomach or nausea.
  • Feeling weak or faint.
  • Sore muscles.

A person might also have injuries like head trauma if they fell, a bitten tongue, bruises and bone fractures.

Caffeine can be a trigger of a seizure

What are the long-term effects of seizures?

After the postictal phase and injuries have all but gone, there are some people who have long-term effects. If, for example, there was a significant fall during the seizure, the person might have serious injuries that have long-lasting effects.

There are also risks of choking and drowning if a seizure occurs in the bath or in a swimming pool, for example.

Seizures that last over 30 minutes can cause permanent damage to the brain. Depending on where the damage is will determine what the long-term effects are.

Who is more at risk of seizures?

There are many different risk factors for epilepsy and seizures.

Here are the most common:

  • Babies who are small for their age at birth.
  • Babies who suffer a seizure before they are one month old.
  • Babies born with a brain abnormality.
  • People who have brain bleeds.
  • People whose brains have abnormal blood vessels.
  • People who experience a loss of oxygen or serious brain injury.
  • People with a brain tumour.
  • People who develop brain infections like meningitis, encephalitis, abscesses, etc.
  • People who suffer from a stroke.
  • People with cerebral palsy.
  • People who have a developmental or intellectual disability.
  • People who suffer a head injury.
  • A family history of febrile convulsions (fever-related seizures) or epilepsy.
  • Someone who has Alzheimer’s disease or dementia (later stages of the illness).
  • Someone with ASD (autism spectrum disorder).
  • Someone with febrile seizures that are long.
  • Someone who experiences status epilepticus (repeated seizures or long seizure episodes).
  • People using illegal drugs like cocaine.

How are seizures diagnosed?

It can be hard to know that someone is having a seizure and doctors have a hard time diagnosing them too. While some types of seizures are easy to diagnose (tonic-clonic seizures, for example), other types aren’t so obvious. What’s more, a person’s doctor usually won’t observe the seizure as they’re not there when they occur.

If seizures are suspected, a doctor will try and determine whether or not a seizure occurred and what the cause was. If a specific medical condition (e.g., diabetes) caused the seizure, the person will need treating for that condition.

If a doctor suspects epilepsy, they will likely order tests and they might prescribe preventative medication. A doctor that specialises in brain disorders is called a neurologist.

Tests that might help diagnose seizures

There are lots of tests that neurologists use to help diagnose seizures. One such test is an EEG, which stands for electroencephalogram. This test is painless and it looks at the electrical patterns in the brain to spot any abnormalities.

Other tests might be:

  • A CT or CAT (computerised tomography) scan. This uses X-rays and computers to create highly detailed imagery of the brain.
  • An MRI (magnetic resonance imaging). This uses radio waves and magnetic fields to look at the brain with precision.

How are seizures treated?

Not everyone will need treatment for their seizures. A doctor will probably not initiate any sort of treatment until a person has had more than one seizure as they can be isolated incidents.

The goal of treatment for seizures is to prevent seizures with few side effects. Here are some ways seizures are treated.


Treating seizures often involves using anti-seizure medication. There are lots of different types and the goal will be to find a medicine that controls the seizures whilst not having side effects or as few as possible.

Side effects can include changes in mood, dizziness, fatigue and weight gain. Some more serious ones include bone marrow damage or liver damage.

Diet changes

It has been proved that a ketogenic diet can help control seizures. This is a diet that is low in carbohydrates and high in fat. It is challenging to follow this strict diet as there are limits on the types of foods you can eat. There are similar diets like the low G.I. (glycaemic index) diet and Atkins diet that can help too, but these aren’t as effective.

Surgical treatment

Surgery can sometimes be used to stop seizures but this is only possible if the seizures always happen in the same area of the brain. There are different types of surgery for epileptic treatment.

These include:

  • Lesionectomy/lobectomy – A surgeon will remove the part of the brain where seizures are originating.
  • Multiple subpial transection – A surgeon will cut some parts of the brain to prevent the seizures. This type of surgery is usually carried out when the part of the brain causing the seizures can’t be removed safely.
  • Corpus callosotomy – A surgeon will cut the connections between the two sides of the brain to treat seizures that start in one side and go to the other. However, seizures can still happen on the side of the brain where they’ve been occurring.
  • Hemispherectomy/hemispherotomy – A surgeon will remove half of the brain’s outer layer. This extreme surgery will only happen when nothing else is able to control the seizures and when the seizures only affect one side of the brain. A person might lose lots of their functional abilities afterwards but when children have this surgery, they are often able to recover the skills lost with rehabilitation.
  • Laser interstitial thermal therapy (thermal ablation) – This is a less invasive procedure that targets a specific part of the brain where the seizures originate. It destroys the cells causing the seizures.

Electrical stimulation

Another type of treatment is electrical stimulation. There are different types of electrical stimulation.

  • Vagus nerve stimulation involves a device implanted under the skin to stimulate the vagus nerve. This can send signals to the brain to prevent seizures. Some people might still take medicine at a lower dose.
  • Responsive neurostimulation involves a device implanted on the brain’s surface or within the tissue in the brain. The device detects seizure activity and then delivers electrical stimulation to the area to stop a seizure from happening.
  • Deep brain stimulation involves implanting electrodes in parts of the brain. These produce electrical impulses to regulate brain activity. The electrodes are attached to a device similar to a pacemaker that is placed in the chest. This controls the stimulation.
Surgery can be a treatment for a seizure

What to do during a seizure

If you happen to see someone having a seizure, you can do things to help. Witnessing a seizure can be scary but it’s important not to panic.

Here are some initial steps to take:

  • Only move the person if they are in danger e.g., near a road.
  • If they are on the ground, cushion their head to prevent injury.
  • Loosen clothing around the neck (e.g., tie or collar) to help breathing (it’s common for breathing to be shallow and lips to turn blue).
  • Put them into the recovery position when they have stopped fitting.
  • Reassure them until they have recovered.
  • Note the seizure start and finish time.
  • Don’t put anything into their mouth.

Calling for help

There are certain occasions when you might need to call an ambulance for a seizure.

You should call 999 if:

  • This is the first seizure the person has had.
  • The seizure is atypical for them – i.e., it lasts longer than normal or presents differently.
  • The seizure is longer than five minutes.
  • The person doesn’t come round fully or they have another seizure without having regained consciousness.
  • The person has injured themselves seriously during the seizure.

People who regularly have seizures (i.e., those with epilepsy) don’t always need to go to hospital whenever they have a seizure.

Some people might wear a bracelet or carry a special card to inform others that they have epilepsy.

Other things to do when someone is having a seizure

There are some things you can do that might be useful for a person and their doctor to know about the seizure.

Here are some things you might want to note:

  • What happened before the seizure and what were they doing?
  • Did they mention an odd taste or smell?
  • Did their mood change suddenly?
  • What made you notice the seizure? Did they fall? Make a noise? Roll their eyes? Turn their head? Have body movements?
  • Was there any warning of the seizure coming on?
  • Did they lose awareness or consciousness?
  • Did they become pale, blue or flushed?
  • Which parts (if any) twitched or jerked?
  • Did their breathing alter?
  • Did they mumble, fumble with their clothing, or wander around?
  • How long was the seizure?
  • Did they lose control of their bowel or bladder?
  • What were they like after the seizure had ended?
  • Did they sleep? How long for?

Final thoughts on ‘What is a seizure?’

Knowing what a seizure looks like and how to react in the event of someone having a seizure is useful to everyone. In the workplace, it’s useful to know about anyone who suffers from seizures so that there can be a care plan put into place.

Anyone who does suffer from seizures should ideally let people they work with know about their condition and what to do should they have a seizure in the workplace.

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About the author

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Louise Woffindin

Louise is a writer and translator from Sheffield. Before turning to writing, she worked as a secondary school language teacher. Outside of work, she is a keen runner and also enjoys reading and walking her dog Chaos.

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