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Brain abscess

Definition

A brain abscess is a collection of pus, immune cells, and other material in the brain, usually from a bacterial or fungal infection.

Alternative Names

Abscess - brain; Cerebral abscess; CNS abscess

Causes, incidence, and risk factors

Brain abscesses commonly occur when bacteria or fungi infect part of the brain. Swelling and irritation (inflammation) develop in response to this infection. Infected brain cells, white blood cells, live and dead bacteria, and fungi collect in an area of the brain. Tissue forms around this area and creates a mass.

While this immune response can protect the brain by isolating the infection, it can also do more harm than good. The brain swells. Because the skull cannot expand, the mass may put pressure on delicate brain tissue. Infected material can block the blood vessels of the brain.

The germs that cause a brain abscess can reach the brain through the blood. The source of the infection is often not found. However, the most common source is a lung infection. Less often, a heart infection is the cause. Germs may also travel from a nearby infected area (for example, an ear infection or a tooth abscess) or enter the body during an injury (such as a gun or knife wound) or neurosurgery.

In children with congenital heart disease or a blood vessel birth defect, such as those with Tetralogy of Fallot, infections are more able to reach the brain from the intestines, teeth, or other body areas.

The following raise your risk of a brain abscess:

  • A weakened immune system (such as in AIDS patients)
  • Chronic disease, such as cancer 
  • Drugs that suppress the immune system (corticosteroids or chemotherapy)
  • Right-to-left heart shunts, usually the result of congenital heart disease

Symptoms

Symptoms may develop slowly, over a period of 2 weeks, or they may develop suddenly. They may include:

Signs and tests

A brain and nervous system (neurological) exam will usually show signs of increased intracranial pressure and problems with brain function.

Tests to diagnose a brain abscess may include:

A needle biopsy is usually performed to identify the cause of the infection.

Treatment

A brain abscess is a medical emergency. Pressure inside the skull may become high enough to be life threatening. You will need to stay in the hospital until the condition is stable. Some people may need life support.

Medication, not surgery, is recommended if you have:

  • Several abscesses (rare)
  • A small abscess (less than 2 cm)
  • An abscess deep in the brain
  • An abscess and meningitis
  • Shunts in the brain for hydrocephalus (in some cases the shunt may need to be removed temporarily or replaced)
  • Toxoplasma gondii infection in a person with HIV

Antibiotics will be prescribed. Antibiotics that work against a number of different bacteria (broad spectrum antibiotics) are most commonly used. You may be prescribed several different types of antibiotics to make sure treatment works.

Antifungal medications may also be prescribed if the infection is likely caused by a fungus.

Immediate treatment may be needed if an abscess is injuring brain tissue by pressing on it, or there is a large abscess with a large amount of swelling around that it is raising pressure in the brain.

Surgery is needed if :

  • Increased pressure in the brain continues or gets worse
  • The brain abscess does not get smaller after medication
  • The brain abscess contains gas (produced by some types of bacteria)
  • The brain abscess might break open (rupture)

Surgery consists of opening the skull, exposing the brain, and draining the abscess. Laboratory tests are often done to examine the fluid. This can help identify what is causing the infection, so that more appropriate antibiotics or antifungal drugs can be prescribed.

The surgical procedure used depends on the size and depth of the abscess. The entire abscess may be removed (excised) if it is near the surface and enclosed in a sac.

Needle aspiration guided by CT or MRI scan may be needed for a deep abscess. During this procedure, medications may be injected directly into the mass.

Certain diuretics and steroids may also be used to reduce swelling of the brain.

Expectations (prognosis)

If untreated, a brain abscess is almost always deadly. With treatment, the death rate is about 10 - 30%. The earlier treatment is received, the better.

Some patients may have long-term neurological problems after surgery.

Complications

  • Brain damage
  • Meningitis that is severe and life threatening
  • Return (recurrence) of infection
  • Seizures

Calling your health care provider

Go to a hospital emergency room or call the local emergency number (such as 911) if you have symptoms of a brain abscess.

Prevention

You can reduce the risk of developing a brain abscess by treating any disorders that can cause them. Have a follow-up examination after infections are treated.

Some people, including those with certain heart disorders, may receive antibiotics before dental or urological procedures to help reduce the risk of infection.

References

Nath A, Berger J. Brain abscess and parameningeal infections. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 421.

Tunkel AR. Brain abscess. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2009:chap 88.


Review Date: 10/6/2012
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.
The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
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