What is a seizure?

Normally, the brain produces small electrical signals when the brain cells and nerves send messages to one another. A seizure or fit happens when ordinary brain activity is suddenly upset because electrical activity from one part of the brain has spread uncontrollably to other parts of the brain for a short time.

During a seizure, any of the brain’s normal functions, such as memory, consciousness (awareness of self and the surroundings), movement and sensations, can be temporarily lost or disturbed.

What causes seizures?

There are several things that can cause a seizure. These include:

  • epilepsy
  • stroke
  • a head injury
  • a brain tumour
  • an infection (e.g. meningitis, abscess)
  • drug abuse and overdoses
  • low salt levels in the blood
  • low blood sugar (hypoglycaemia)
  • fever (in children)
  • alcohol withdrawal.

Of the people who have a seizure for an unknown reason, about half will go on to have another seizure. In some people, a first seizure may later be diagnosed as epilepsy.

Someone who has had a seizure is more likely to have another seizure if they have a brain injury or other type of previous abnormality, like epilepsy. If someone has already had two seizures, there is an 80% chance that they will have more.

What are the different types of seizures?

Seizures are divided into two broad categories: partial seizure and generalised seizures.

Partial seizures

Partial seizures (also called focal seizures) involve only part of the brain. Some types of partial seizure do not cause reduced consciousness or awareness, but may cause twitching of a limb, or unusual tastes or sensations such as pins and needles. Other types of partial seizures do affect awareness, and the person having the seizure may have little or no memory of what happened. These seizures can cause confusion and automatic movements, such as fiddling with clothes, chewing, or wandering about, and the person may respond if spoken to.

Generalised seizures

Generalised seizures involve the whole brain and cause loss of consciousness. They can happen without warning, and the person having the seizure will have no memory of the event. There are several types of generalised seizures.

  • Tonic-clonic convulsive (grand mal) – To begin with, the muscles becomes rigid (the tonic phase) and the person may fall down or bite their tongue or cry out. Their muscles then relax and tighten rhythmically, (the clonic phase) their breathing may become laboured, and they may lose control of their bladder or bowel. After the seizure, they might feel tired and confused, and have a headache.
  • Tonic – There is general stiffening of the muscles without any jerking, and the person may fall to the ground. After the seizure, they usually recovery quickly.
  • Atonic (drop attacks) – The person suddenly loses muscle tone, causing them to fall. Recovery is usually fast.
  • Myoclonic – There is brief and abrupt jerking of one or more limbs.
  • Absence (petit mal) – The person (most often a child) experiences a brief interruption of consciousness and becomes unresponsive for several seconds. They may appear blank or staring, sometimes with a fluttering of the eyelids.

How are seizures treated?

When someone is having a seizure, it is important they are kept safe and placed in a position where they will not harm themselves.

To stop a seizure, drugs can be given through an intravenous cannula, sometimes as a continuous infusion.

If someone having a seizure needs help with their breathing, oxygen may be given through a mask, or in severe cases, a breathing tube may need to be inserted via their mouth into their airway and attached to a breathing machine.

What happens in Intensive Care?

If someone is having seizures and needs to be admitted to the Intensive Care Unit (ICU), they will be cared for by a team of doctors and nurses.

Exactly what is done will depend on their individual circumstances.

  • Their heart rate, blood pressure, oxygen saturation and temperature will be monitored and displayed on a bedside monitor.
  • Intravenous fluids and medications such as analgesics (pain killers), sedatives (to help with sleep) and antibiotics (for infections) may be given into a central venous catheter using infusion pumps.
  • If they need help with their breathing, they may have an endotracheal tube inserted to connect them to a ventilator.
  • If they are unable to eat or take tablets by mouth, they may have a nasogastric tube inserted.
  • An indwelling urinary catheter may be inserted to measure their urine output.
  • Their blood and urine will be regularly tested to check liver and kidney function, since this can be affected by drugs used to stop seizures.
  • An electroencephalogram (EEG) may be done if it is unclear whether they have actually had, or are still having, a seizure.
  • Other tests, such as a head CT scan or lumbar puncture, may need to be done to look for possible causes of the seizures. (See the Equipment page for more detail on the machines mentioned.)

How long someone with seizures needs to stay in the ICU will depend on their need for ongoing support and how they respond to treatment. Please ask the ICU nurses or doctors if you have any questions.

Useful links

Publication details

Seizures, version 2, July 2015. Reviewer: Clare Loveday, Nurse Manager, ICU Services, St George Hospital.


The information on this page is general in nature and cannot reflect individual patient variation. It reflects Australian intensive care practice, which may differ from that in other countries. It is intended as a supplement to the more specific information provided by the doctors and nurses caring for your loved one. ICNSW attests to the accuracy of the information contained here but takes no responsibility for how it may apply to an individual patient. Please refer to the full disclaimer.