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Brain Abscess

Medically reviewed by Last updated on Jan 12, 2022.

What is a Brain Abscess?

Harvard Health Publishing

A brain abscess is a collection of pus enclosed in the brain tissue, caused by a bacterial or fungal infection. A brain abscess can develop as a complication of an infection, trauma or surgery. They are rare, although people with weakened immune systems (such as people with HIV or those who have received an organ transplant) are more likely to get a brain abscess. 

This type of infection usually begins in one of these ways: 

  • It spreads from a nearby site, such as a middle ear infection, sinus infection or dental abscess.  
  • Blood carries the infection from further away in the body to the brain.  
  • Infectious organisms enter the brain through a penetrating injury, such as a gunshot wound, or from neurosurgical procedures or facial trauma. 


Symptoms vary depending on the size and location of the abscess. 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. Aspirin and other pain medication do not relieve the pain. 

About half of the people with a brain abscess have a low-grade fever. Other symptoms may include nausea and vomiting, neck stiffness, seizures, personality changes and muscular weakness on one side of the body.


Diagnosing a brain abscess is not easy because the early symptoms are so general. For example, many things can cause headaches. For this reason, the diagnosis of brain abscess is usually delayed until about two weeks after symptoms first develop. In some cases, people with brain abscesses develop seizures or neurological changes, such as muscle weakness on one side of the body, before the diagnosis is made.  

If your doctor is concerned you have a brain abscess, he or she will ask about your medical and travel history to determine your risk of having certain infections. The doctor also will ask if you have any of the symptoms of brain abscess. If you do, he or she will ask when they started, how they've progressed, and whether you've had a recent infection or any trauma that could predispose you to a brain abscess. 

To diagnose a brain abscess, you will need diagnostic tests, such as computed tomography (CT) or magnetic resonance imaging (MRI) scans. These provide pictures of the inside of the brain. The abscess will appear as one or more spots. Blood and other body fluids may be studied to find the original source of the infection. If the diagnosis remains uncertain, a neurosurgeon can remove a piece of the brain abscess with a fine needle. 

Expected Duration

A brain abscess can grow very quickly, typically becoming fully formed within about two weeks. Your doctor will begin treatment immediately after you are diagnosed. Prompt medical attention is the key to relieving your symptoms more quickly and minimizing damage to your long-term health. Surgical drainage of the abscess is often necessary as well. 


Some brain abscesses are related to poor dental hygiene or complex sinus infections.  You should floss daily, brush your teeth properly and visit your dentist regularly. Treat sinus infections with decongestants. If symptoms of a sinus or dental infection persist, you may need an antibiotic.  

People with untreated HIV infection are at increased risk of brain abscess. Prevent HIV by practicing safe sex. If you have HIV, you substantially reduce your chance of developing a brain abscess by taking anti-viral medications regularly.


Treatment of a brain abscess typically requires a two-pronged approach:  

  • Treating the infection with antibiotics — If the specific type of bacterium is known, a targeted antibiotic is used; otherwise, broad-spectrum antibiotics are given to kill a large number of possible infectious agents. Antibiotics usually are continued for six weeks or more to make sure that the infection is eliminated. 
  • Draining or removing the abscess — If the abscess can be reached easily and there is little danger of damaging the brain, the abscess may be surgically removed. In other cases, the abscess is drained, either by cutting it or by inserting a needle.  

To confirm that the treatment was successful, you will be monitored by magnetic resonance imaging (MRI) or computed tomography (CT) scans to view the brain and abscess. If seizures are a problem you may need anticonvulsant medications, which may continue even after the abscess has been successfully treated.  

Treatment options

The following list of medications are in some way related to or used in the treatment of this condition.

When To Call A Professional

See your doctor if you experience a nearly constant headache that gets worse over several days or weeks. If you also have nausea, vomiting, seizures, personality changes or muscle weakness, seek emergency care. 


Without treatment, a brain abscess can be fatal. Most people with a brain abscess are treated successfully. Unfortunately, long-term neurological problems are common even after the abscess is removed and the infection is treated. For example, there may be lingering problems with body function, personality changes or seizures due to scarring or other damage to the brain. 

Additional Info

American Academy of Neurology (AAN)

Learn more about Brain Abscess

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Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.