A brain abscess is a pus-filled swelling in the brain caused by an infection. It is a rare and life-threatening condition.

A brain abscess usually occurs when bacteria or fungi enter the brain tissue.

Symptoms of a brain abscess include:

• headache – which is often severe and cannot be relieved by taking painkillers
• changes in mental state, such as appearing very confused
• weakness or paralysis on one side of the body
• a high temperature (fever) of or above 38C (100.4F)
• seizures (fits) 

What causes a brain abscess?

There are three main ways that 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.

Treating a brain abscess

A brain abscess is regarded as a medical emergency. This is because the swelling caused by the abscess can disrupt the blood and oxygen supply to the brain. There is also a risk that the abscess may burst (rupture). If left untreated, a brain abscess can cause permanent brain damage and can be fatal.

If you suspect that you or someone you know may have a brain abscess, call 999 for an ambulance.

A brain abscess is usually treated using a combination of antibiotics (or in some cases, antifungals) and surgery. The surgeon will usually open the skull and drain the pus from the abscess, or remove the abscess entirely.

The sooner the condition is diagnosed and treated, the lower the chance a person has of developing long-term complications.

Read more about treating a brain abscess.

Complications

Any damage to brain tissue can result in long-term complications, such as:

• brain damage – ranging from mild to severe
• epilepsy – where a person has repeated seizures (fits)

Read more about the complications of a brain abscess.

Who is affected

Brain abscesses tend to only be a significant problem in parts of the world where access to antibiotics is limited.

In England, brain abscesses are extremely rare. Most neurosurgeons (surgeons who specialise in the brain and nervous system) would only expect to treat around one to four cases per year. 

Brain abscesses can occur at any age, but most cases are reported in people aged 40 or younger. They are more common in men than women, though the reason for this is unclear.

Outlook

Because of advances in diagnostic and surgical techniques, the outlook for people with brain abscesses has improved dramatically. Around 70% of people will make a full recovery.

However, in around 10% of cases, a brain abscess may be fatal.