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Brain Abscess

Symptoms, risk factors, and diagnosis of this neurological disorder.

What is a brain abscess?

A brain abscess is a serious infection of the brain. It occurs when bacteria get into the brain, multiply, and form a cluster. Normally, the brain shouldn’t have any bacteria. But they can make their way in from somewhere else in your body, or can travel in the blood. As the bacteria multiply, the infection grows and can cause damage and swelling in the brain tissue.

The symptoms of a brain abscess include headache, fever, nausea, fatigue, and neurological symptoms. These can be confused with a brain tumor, stroke, or autoimmune disease so seeing a specialist (neurologist) is crucial. A brain abscess can also lead to an infection in the spinal fluid, called meningitis.

A brain abscess can cause long-term neurological damage, including impaired physical movement, personality changes, and seizures. Anywhere from 5% to 32% of brain abscesses are fatal, according to the National Institutes of Health.

That's why it's important to be aware of the signs as early as possible and treat it as a medical emergency. A brain abscess can be hard to treat since antibiotics do not get into brain tissue easily.

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Most common symptoms

Pro Tip

Brain abscesses are extraordinarily rare. Sinus infections are relatively common. Your doctor can help sort these two apart—usually just from discussing your symptoms with you. —Dr. Brian Walcott

A brain abscess can create many different symptoms depending on what part of the brain is infected.

The most common symptoms are a headache and fever, and some people may also have nausea and/or vomiting. Because these can be symptoms of many illnesses, a brain abscess can be hard to detect at first. In two-thirds of cases, people have symptoms for as long as two weeks before they are diagnosed.

Most people with brain abscess will have a headache that is different from a typical headache. The headache usually gets worse with time. Neurological symptoms can also develop such as muscle weakness, paralysis on one side of the body, trouble speaking (like slurred speech), or poor coordination.

Many people with a brain abscess have seizures as the pressure builds in their brains. They may also experience a change in mental status, like becoming confused, feeling drowsy, being irritable, not being able to focus, not responding to others quickly, or even falling into a coma.

Main symptoms

Other symptoms you may have

  • Unable to flex the neck because the neck muscles are very stiff
  • Change in vision
  • Sense of disequilibrium (unsteadiness, imbalance, or vertigo)
  • Nausea and vomiting

Next steps

If you suspect you may have a brain abscess, go to the emergency room. A brain abscess is not common, but if you do have one, it has to be treated right away. Otherwise you could end up with serious neurological damage.

Tell the doctor if you have any risk factors like IV drug use, congenital heart disease, heart valve replacement, a recent dental procedure, or any condition that suppresses your immune system.

If you had recent brain surgery, you should contact your surgeon if you have a fever or a seizure, or feel any kind of weakness.

Brain abscess causes

Brain abscesses happen when bacteria get into your brain. It can be caused by many different types of bacteria. It is thought that once bacteria start to multiply and grow in the brain, it is difficult for the body to fight it because it is easy to “hide”’ from the immune system when inside of the brain.

More commonly, bacteria get into the brain through the bloodstream. Often this is from using intravenous drugs. It can also happen if an infection somewhere else in the body—like a heart valve—releases bacteria into the blood.

Very rarely, brain abscesses have happened after extensive dental work, when bacteria were accidentally let into the bloodstream.

Brain abscesses can also happen in people with an abnormal connection of arteries and veins in their lungs, called an arteriovenous malformation. This can be seen in a genetic condition called hereditary hemorrhagic telangiectasia, which is rare.

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Who is likely to develop a brain abscess?

Dr. Rx

Let your doctor know whether any of these apply to you: intravenous drug abuse, recent dental procedure, heart disease or heart valve replacement, genetic conditions that run in your family, personal history of cancer, and history of immunosuppression or chemotherapy. —Dr. Walcott

Several factors can increase your risk of developing a brain abscess:

  • Intravenous (IV) drug use
  • Recent brain surgery
  • Recent heart surgery, such as a heart valve replacement
  • Chronic sinus infections
  • Recent extensive dental work
  • Arteriovenous malformation (an abnormal connection of arteries and veins in your lung, in a rare genetic condition called hereditary hemorrhagic telangiectasia)
  • Having a weakened immune system (someone who has HIV, AIDS, cancer, another chronic illness, or is going through chemotherapy)
  • Recent blow to the head (can cause a compound skull fracture which can push bones into the brain)

Can a brain abscess be cured?

Pro Tip

Many people think that brain abscesses can be fixed, or “cleaned up,” with surgery. The goal of surgery is actually to sample the abscess to find out the specific type of bacteria that is growing and to remove whatever fluid can be removed through a needle. Antibiotics treat the remaining bacteria without the risk of damaging the surrounding brain tissue. —Dr. Walcott

A brain abscess is treatable if you start treatment early.

Your doctor will take a clinical history, probably do blood work, and order an MRI of your brain. If the MRI shows a lesion, you will have a surgical procedure called a “needle biopsy” to take a sample of tissue. This will confirm that you have a brain abscess and tell the doctors what strains of bacteria you have. Your doctor will also remove as much bacteria as possible with the needle.

Once your doctor knows the exact strains of bacteria, they will give you targeted antibiotics to treat any bacteria that are left. It can take weeks or longer to get rid of the infection. If the surgeon finds a more widespread infection, they may perform a brain surgery called a craniotomy to remove all the bacteria.

If your doctor thinks you have had seizures, you may be given anti-seizure medications. You will also have a follow-up MRI to track your response to treatment. If there is an underlying cause for the abscess, like a heart valve infection (infective endocarditis), you’ll also need to have that treated.

Follow up

After treatment, you’ll see an expert in infectious disease. They will make sure your antibiotics are working and figure out how long you’ll need follow-up treatment. You’ll also need to follow up with your neurosurgeon. If you were given anti-seizure drugs during treatment, you’ll need to follow up with a neurologist.

Preventative tips

Intravenous drug use is one of the most common causes of a brain abscess, and is completely preventable.

Additionally, ask your dentist if you need to take any preventative antibiotics around the time of dental procedures, especially if you have a history of a heart condition or an illness called hereditary hemorrhagic telangiectasia.

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