A brain abscess is a pus-filled swelling in the brain. It usually occurs when bacteria or fungi enter the brain tissue after an infection or severe head injury.

Although the risk of developing a brain abscess is extremely low in England, it is a life-threatening condition and should be diagnosed and treated as soon as possible. 

Symptoms of a brain abscess

The symptoms of a brain abscess may develop quickly or slowly but can include:

  • headache – which is often severe, located in a single section of the head and can't be relieved with painkillers
  • changes in mental state – such as confusion or irritability
  • problems with nerve function – such as muscle weakness, slurred speech or paralysis on one side of the body
  • a high temperature (fever) of 38C (100.4F) or above 
  • seizures (fits)
  • nausea and vomiting
  • stiff neck
  • changes in vision – such as blurring, greying of vision or double vision (due to the abscess putting pressure on the optic nerve)

When to seek medical advice

Any symptoms that suggest a problem with the brain and nervous system should be treated as a medical emergency. These include:

  • slurred speech
  • muscle weakness or paralysis
  • seizures occurring in a person with no previous history of seizures

If you or someone you know experiences any of these symptoms, phone 999 immediately and ask for an ambulance.

Any symptoms that suggest a worsening infection, such as fever and vomiting, should be reported to your GP immediately.

If your GP isn't available, contact your local out-of-hours service or call NHS 111.

Causes of a brain abscess

There are three main ways a brain abscess can develop. These are:

  • an infection in another part of the skull – such as an ear infection, sinusitis or dental abscess, which can spread directly into the brain
  • an infection in another part of the body – for example, the infection that causes pneumonia spreading into the brain via the blood
  • trauma, such as a severe head injury – that cracks open the skull, allowing bacteria or fungi to enter the brain

However, in some cases, the source of the infection remains unknown.

Read more about the causes of a brain abscess.

Diagnosing a brain abscess

If a brain abscess is suspected, an initial assessment will be made based on your symptoms, medical history and whether you've had a recent infection or a weakened immune system.

Blood tests can also be carried out to check for an infection.

If you're referred to hospital for further tests, you may have either:

If an abscess is found, a procedure known as CT-guided aspiration may be used to remove a sample of pus for testing. This involves using a CT scan to guide a needle to the site of the abscess.

Treating a brain abscess

A brain abscess is regarded as a medical emergency. Swelling caused by the abscess can disrupt the blood and oxygen supply to the brain. There's also a risk of the abscess bursting (rupturing).

If left untreated, a brain abscess can cause permanent brain damage and could be fatal.

A brain abscess is usually treated using a combination of:

  • medication – either antibiotics or antifungals
  • surgery – either draining the pus through a hole in the skull (simple aspiration) or opening the skull and removing the abscess entirely (craniotomy)

Treatment with antibiotics often begins before a diagnosis is confirmed, to reduce the risk of complications.

Read more about treating a brain abscess.

Complications of a brain abscess

Complications of a brain abscess can include:

  • a reoccurring abscess – seek immediate medical advice if you think there's even a small chance your abscess has reoccurred; this is more common in people with a weakened immune system or cyanotic heart disease
  • brain damage – mild to moderate brain damage often improves with time but severe brain damage is likely to be permanent; brain damage is more of a risk if diagnosis and treatment are delayed
  • epilepsy – where a person has repeated seizures (fits)
  • meningitis – a life-threatening infection of the protective membranes around the brain, which requires urgent treatment; this is more common in children

Page last reviewed: 20/06/2016

Next review due: 01/12/2018