A brain abscess is a pus-filled swelling in the brain caused by an infection. It is a rare and life threatening condition.
It happens when bacteria or fungi enter the brain tissue.
Symptoms of a brain abscess include:
There are three main ways that a brain abscess can develop:
Although in around 1 in 7 cases the source of the infection remains unknown.
Read more about the causes of 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 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 the treating a brain abscess.
Any damage to the tissue of the brain can result in long-term complications, such as:
Read more about the complications of a brain abscess.
Brain abscesses tend to only be significant problem in parts of the world where access to antibiotics is limited.
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. It is not clear why this should be the case.
Because of advances in diagnostic and surgical techniques, the outlook for people with brain abscesses has improved dramatically. Nowadays, deaths only occur in an estimated 1 in 10 of cases. Many people make a full recovery.
The symptoms of a brain abscess can develop quickly or slowly.
In around two-thirds of people, symptoms are present for two weeks or less before they escalate to the point where the person needs to be admitted to hospital.
Common symptoms include:
Any symptoms that suggest a problem with the brain and nervous system, such as slurred speech, muscle weakness or paralysis, or seizures occurring in a person who had no previous history of seizures should be treated as a medical emergency. Call for an ambulance or seek medical attention as soon as possible.
Any symptoms that suggest a worsening infection, such as fever and vomiting, should be reported to your doctor immediately. If your doctor is not available, contact your local emergency medical centre.
An abscess is a pus-filled swelling caused by infection with either bacteria or fungi.
The abscess is created by your immune system as a defence mechanism. If the immune system is unable to kill an infection, it will try to limit its spread. Your immune system will use healthy tissue to form a wall around the source of infection 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, which is a thick membrane that filters out impurities from blood before allowing it into your brain.
However, in some people, for reasons not always entirely clear, germs can get through these defences and infect the brain.
The three most common routes for germs to enter the brain are:
Though in around 1 in 7 cases no obvious cause for the infection can be found.
The causes of a brain abscess are explained in more detail below.
In up to a 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 1 in 4 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 responsible for 1 in 10 cases.
The most commonly reported causes include:
In rare cases, a brain abscess can develop as a complication of surgery.
An initial assessment will be made based on your physical symptoms and medical history, such as whether you have had a recent infection or a weakened immune system.
Blood tests will be carried out to check for the presence of infection. A high level of white blood cells in your blood indicates the presence of a serious infection.
If a brain abscess is suspected, the diagnosis can be confirmed using a brain scan.
A computerised tomography (CT) scan involves a series of X-rays taken of your body at different angles. This produces a detailed image of the inside of your body.
A CT scan can often detect the presence of the abscess and any associated swelling inside the brain.
A magnetic resonance imaging (MRI) scan uses strong magnetic fields and radio waves to produce a detailed image of the inside of your body.
A MRI scan can provide a more detailed image than a CT scan so is sometimes used if the results of the CT scan are inconclusive.
If an abscess is found, neurosurgeons (doctors who specialise in the treatment of the nervous system and brain) can use a CT scan to guide a needle to the site of the abscess and remove a sample of pus for further testing. This is known as CT-guided aspiration. The sample of pus should indicate the type of germ causing the abscess.
Treatment with broad-spectrum antibiotics will usually begin as soon as possible, even before a CT-guided aspiration is carried out, because it can be dangerous to wait for the results.
Broad-spectrum antibiotics can be used against a wide range of bacteria. They will be used before a specific diagnosis is made because there is a high chance they will be effective if the infection is caused by bacteria.
If the test reveals the abscess is caused by a fungus, the treatment plan can be changed and antifungal medication given.
Treatment for a brain abscess will depend on the size and number of brain abscesses present. A brain abscess is a medical emergency, so you will need treatment in hospital and will stay there until your condition is stable.
Surgery will be avoided if thought too risky or if an abscess is small and could be treated by medication alone.
Medication is recommended over surgery if you have:
You will 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 is usually necessary to drain the pus out of the abscess.
There are two surgical techniques for treating a brain abscess:
Simple aspiration involves using a CT scan to locate the abscess and then drills a small hole known as a burr hole into the skull. The pus is then drained through the hole and the hole 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 does not respond to aspiration or reoccurs at a later date.
During a craniotomy, the surgeon will shave a small section of your hair and then remove a small piece of your skull bone (a bone flap) to gain access to your brain.
The abscess will then be drained of pus or totally removed. A CT-guided localisation system may be used during the operation, which allows 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 the general anaesthetic (where you are put to sleep).
As with all surgery, a craniotomy carries risks, but serious complications are uncommon.
Possible complications of a craniotomy are:
The site of the cut (incision) in your skull can become infected, although this is uncommon. You are usually given antibiotics around the time of your operation to prevent infection.
Once your brain abscess has been treated, you will probably stay in hospital for several weeks so your body can be supported while you recover.
You will also receive a number of CT scans, to make sure the brain abscess has been completely removed.
Most people will then need a further 6 to 12 weeks rest at home before they are fit enough to return to work or full-time education.
After treatment for a brain abscess, avoid any contact sport where there is a risk of injury to the skull, such as boxing, rugby or football.
Possible complications of a brain abscess are outlined below.
Brain damage can range from mild through moderate to severe.
Mild brain damage can result in:
Moderate brain damage can result in:
Severe brain damage can result in:
Mild to moderate brain damage often improves with time. Severe brain damage is likely to be permanent.
Brain damage is more of a risk when the diagnosis of a brain abscess was delayed and treatment did not begin quickly enough. Brain abscesses can now be diagnosed very easily with a CT or MRI scan, so the risk of serious brain damage is now low.
A common complication of brain abscesses is epilepsy, a condition that causes repeated fits or seizures. Epilepsy is a long-term condition and symptoms can usually be controlled using medication.
Read more about the treatment of epilepsy.
In some cases, especially those involving children, a brain abscess can develop into bacterial meningitis, a life-threatening infection of the protective membranes that surround the brain.
Symptoms of meningitis include:
Someone with bacterial meningitis will require urgent treatment in hospital; usually an intensive care unit (ICU).
Antibiotics will be used to treat the underlying infection. These will be given intravenously (through a vein in the arm).
At the same time a person may also be given:
Read more about the treatment of meningitis.
Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.