Brain Abscess

A brain abscess is a dangerous collection of pus within the brain that requires urgent medical attention. This life-threatening infection can develop when bacteria or fungi invade brain tissue, causing swelling that puts pressure on the brain and disrupts its normal function.

Table of contents

• What is a brain abscess?
• How common are brain abscesses?
• Symptoms
• Causes and risk factors
• Diagnosis
• Treatment
• Complications
• Outlook and recovery

What is a brain abscess?

A brain abscess is a collection of pus and other materials that forms inside the brain. An infection usually causes the abscess to develop^[1]. You may also hear healthcare providers refer to it as a cerebral abscess^[1].

When an infection targets part of the brain, the body attempts to fight it through inflammation (swelling and irritation as the body tries to heal itself). As the immune system battles the infection, waste materials accumulate. This waste includes dead cells and bacteria or fungi. The body then forms tissue around this collection of pus to create an abscess^[1].

The abscess can swell and put pressure on the brain. This pressure can disrupt the blood and oxygen supply to brain tissue^[2]. A brain abscess is a medical emergency and can be life-threatening if left untreated^[1].

How common are brain abscesses?

Brain abscesses are not common. In the United States, an estimated 1,500 to 2,500 cases happen each year^[1]. Although the risk of developing a brain abscess is extremely low, it remains a serious, life-threatening condition that should be diagnosed and treated as soon as possible^[2].

Symptoms

The symptoms of a brain abscess may develop quickly or slowly over several days to a couple of weeks^[1]. Common symptoms include^[1][2]:

• Headache, which is often severe, located in a single section of the head, and cannot be relieved with painkillers
• Cognitive changes, such as confusion, irritability, or difficulty thinking or processing information
• Numbness, weakness, or paralysis in part of the body
• Changes in mental state
• Speech and language difficulty or slurred speech
• Vision changes, such as blurring, greying of vision, or double vision
• Fever and chills
• Seizures
• Nausea and vomiting
• Stiff neck
• Changes in personality or behavior

More than 75% of people with a brain abscess have a dull, achy headache. For many people, this is the only symptom. The pain usually is limited to the side of the brain where the abscess is, and the pain usually becomes worse until the abscess is treated^[13].

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, and seizures occurring in a person with no previous history of seizures^[2]. If you experience any of these symptoms, visit the emergency room immediately or call emergency services^[1].

Causes and risk factors

What causes a brain abscess?

A bacterial or fungal infection causes brain abscesses^[1]. The germs that cause a brain abscess can reach the brain through the blood, sinuses, an injury, or surgery^[1].

The most common bacteria that cause infection are Staphylococcus and Streptococcus^[1]. These are types of bacteria commonly found in the body.

There are three main ways a brain abscess can develop^[2]:

• An infection in another part of the skull, such as an ear infection, sinusitis (infection of the sinuses), 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 bloodstream
• Trauma, such as a 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. In at least 15% of cases, no source can be identified^[4][7].

Risk factors

You may be more at risk of developing a brain abscess if you^[1]:

• Have a condition that weakens your immune system, such as HIV or AIDS
• Have cancer
• Have a congenital heart disease (a heart defect present at birth)
• Take immunosuppressant medications, such as corticosteroids or chemotherapy
• Have received an organ transplant

Brain abscesses are also more common in people who have undergone recent neurosurgery or facial trauma^[6].

Diagnosis

Diagnosing a brain abscess can be challenging because the early symptoms are so general. For example, there are many causes of headaches that are far more common than brain abscess. For this reason, the diagnosis of brain abscess is often not made until about two weeks after symptoms first develop^[13].

A healthcare provider will diagnose a brain abscess after a neurological exam (a test that checks how well your brain and nervous system are working) and testing. This exam will show that you have increased pressure within your skull and, as a result, your brain is not functioning as expected^[1].

If a brain abscess is suspected, an initial assessment will be made based on your symptoms, medical history, and whether you have had a recent infection or a weakened immune system^[2].

To confirm a diagnosis, your provider will offer tests like^[1][2]:

• Blood tests, including blood culture and complete blood count, to check for an infection
• Imaging tests, such as MRI (magnetic resonance imaging) or CT scan (computed tomography). These provide detailed pictures of the inside of the brain, where an abscess often has a distinct appearance
• Electroencephalogram (EEG), which measures brain activity

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^[2]. A needle biopsy can identify the cause and type of infection to help your provider treat it^[1].

Treatment

A brain abscess is a medical emergency that requires immediate attention^[1]. Swelling caused by the abscess can disrupt the blood and oxygen supply to the brain. There is also a risk of the abscess bursting^[2]. You will need to stay in the hospital until the condition is stable^[4].

Treatment for a brain abscess usually involves a combination of medicines and surgery, depending on the size and number of brain abscesses^[11]. Treatment with antibiotics often begins before a diagnosis is confirmed to reduce the risk of complications^[2].

Medications

You will receive antibiotics or antifungal medications to treat the abscess. You will need to take antibiotics for at least four to eight weeks^[1]. All patients are generally treated with antibiotics for a minimum of 4 to 8 weeks^[10].

You may also need^[1]:

• Water pills to reduce fluid in your body
• Antiseizure medications for seizures
• Steroids to decrease swelling

In some cases, it may be possible to treat an abscess with medicine alone. Medicines are recommended over surgery if you have^[11]:

• Several abscesses
• A small abscess (less than 2.5 centimeters)
• An abscess deep inside the brain
• Meningitis (an infection of the protective membranes around the brain) as well as an abscess

Surgery

Surgery is needed if the abscess is larger than 2 centimeters, if increased pressure in the brain continues or gets worse, if the abscess does not get smaller after medicine, if the abscess contains gas, or if the abscess might break open^[4][11].

There are two surgical techniques for treating a brain abscess^[11]:

Simple aspiration involves using a CT scan to locate the abscess and then drilling a small hole, known as a “burr hole,” into the skull. The pus is drained and the hole sealed. A simple aspiration takes around an hour to complete^[11].

Craniotomy may be recommended if an abscess does not respond to aspiration or reoccurs at a later date. During a craniotomy, the surgeon removes a small piece of your skull bone to gain access to your brain. The abscess is then drained of pus or totally removed. The operation usually takes around 3 hours^[11].

Your surgeon will send a sample of the abscess fluid to a lab to determine what caused it. You will need to take antibiotics or antifungal medications when the lab identifies the cause after surgery^[1].

Complications

Brain abscess complications are life-threatening^[1]. They include^[1][2]:

• Brain swelling (cerebral edema)
• Abscess breaks open (rupture)
• Meningitis, a life-threatening infection of the protective membranes around the brain
• Brain damage, which can range from mild to severe. Mild to moderate brain damage often improves with time, but severe brain damage is likely to be permanent
• Recurring (returning) abscesses, which are more common in people with a weakened immune system or cyanotic heart disease
• Epilepsy, where a person has repeated seizures
• Coma

If left untreated, a brain abscess can cause permanent brain damage and could be fatal^[2]. If untreated, a brain abscess is almost always deadly^[4].

Outlook and recovery

With treatment, the death rate is about 10% to 30%. The earlier treatment is received, the better^[4]. Treating an abscess early leads to the best outcome^[1].

Some people may have long-term brain or nerve damage after a brain abscess or surgery^[4]. Brain damage is more of a risk if diagnosis and treatment are delayed^[2].

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^[11].

Most people need a further 6 to 12 weeks rest at home before they are fit enough to return to work or full-time education^[11].

After treatment for a brain abscess, you should avoid any contact sport where there is a risk of injury to the skull, such as boxing, rugby, or football^[11].