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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.
The symptoms of a brain abscess may develop quickly or slowly but can include:
Any symptoms that suggest a problem with the brain and nervous system should be treated as a medical emergency. These include:
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.
There are three main ways a brain abscess can develop. These are:
However, in some cases, the source of the infection remains unknown.
Read more about the causes of 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.
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:
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 can include:
A brain abscess is usually caused by infection with either bacteria or fungi.
If the immune system is unable to kill an infection, it will try to limit its spread by using healthy tissue to form an abscess, to stop the pus infecting other tissue.
Infections of the brain are rare because the body has evolved a number of defences to protect this vital organ. One of these is the blood-brain barrier, a thick membrane that filters out impurities from blood before allowing it into your brain.
However, in some cases, germs can get through these defences and infect the brain.
Although the exact location of the original infection can't always be identified, the most common sources are described below.
In up to half of cases, the brain abscess occurs as a complication of a nearby infection in the skull, such as:
This used to be a major cause of brain abscesses, but because of improved treatments for infections, a brain abscess is now a rare complication of these kinds of infection.
Infections spread through the blood are thought to account for around one in four cases of brain abscesses.
People with a weakened immune system have a higher risk of developing a brain abscess from a blood-borne infection. This is because their immune system may not be capable of fighting off the initial infection.
You may have a weakened immune system if you:
The most commonly reported infections and health conditions that may cause a brain abscess are:
Direct trauma to the skull can also lead to a brain abscess and is thought to be responsible for 1 in 10 cases.
The most commonly reported causes include:
In rare cases, a brain abscess can develop as a complication of neurosurgery.
Treatment for a brain abscess usually involves a combination of medication and surgery, depending on the size and number of brain abscesses.
A brain abscess is a medical emergency, so you'll need treatment in hospital until your condition is stable.
Treatment with medication often begins before a diagnosis is confirmed to reduce the risk of complications.
In some cases, it may be possible to treat an abscess with medication alone, or surgery may be too risky.
Medication is recommended over surgery if you have:
You'll normally be given antibiotics or antifungal medication through a drip, directly into a vein. Doctors will aim to treat the abscess and the original infection that caused it.
If the abscess is larger than 2cm, it's usually necessary to drain the pus out of the abscess. However, you'll still need a course of antibiotics after surgery.
There are two surgical techniques for treating a brain abscess:
Simple aspiration involves using a CT scan to locate the abscess, then drilling a small hole known as a "burr hole" into the skull. The pus is drained and the hole is sealed.
A simple aspiration takes around one hour to complete.
Open aspiration and excisions are usually carried out using a surgical procedure known as a craniotomy.
A craniotomy may be recommended if an abscess doesn't respond to aspiration or reoccurs at a later date.
During a craniotomy, the surgeon shaves a small section of your hair and removes a small piece of your skull bone (a bone flap) to gain access to your brain.
The abscess is then drained of pus or totally removed. CT-guidance may be used during the operation, to allow the surgeon to more accurately locate the exact position of the abscess.
Once the abscess has been treated, the bone is replaced. The operation usually takes around three hours, which includes recovery from general anaesthetic, where you're put to sleep.
As with all surgery, a craniotomy carries risks, but serious complications are uncommon.
Possible complications of a craniotomy may include:
The site of the cut (incision) in your skull can become infected, although this is uncommon. You're usually given antibiotics around the time of your operation to prevent infection.
Once your brain abscess has been treated, you'll probably stay in hospital for several weeks so your body can be supported while you recover.
You'll also receive a number of CT scans, to make sure the brain abscess has been completely removed.
Most people need a further six to 12 weeks rest at home before they're fit enough to return to work or full-time education.
After treatment for a brain abscess, avoid any contact sport where there's a risk of injury to the skull, such as boxing, rugby or football.
If you've had brain surgery and you hold a driving licence, you're legally required to inform the Driving and Vehicle Licensing Agency (DVLA).
It's likely that the DVLA will suspend your driving licence due to your increased risk of having an epileptic fit. Your licence will only be returned once your GP or surgeon confirms it's safe for you to drive.
For most people, this is likely to be 12 months after surgery with no seizures occurring.