Health Encyclopedia

Brain abscess

Definition

A brain abscess is a mass of immune cells, pus, and other material due to 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. Inflammation develops in response. Infected brain cells, white blood cells, and live and dead microorganisms collect in a limited area of the brain. This area becomes enclosed by a membrane that forms around it 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 and the mass may put pressure on delicate brain tissue. Infected material can block the blood vessels of the brain.

The bacteria or fungi that cause a brain abscess common reach the brain through the blood. The source of the infectious organism is often not found. When identified, the most common source is a lung infection. Bacteria or fungi may also travel from a nearby infected area (for example, an ear infection) or be introduced into the body during an injury (such as a gun or knife wound) or surgery.

In children with congenital heart disease or defect, such as those born 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:

Right-to-left heart shunts
Chronic disease, such as cancer or Osler-Weber-Rendu syndrome
A weakened immune system (such as those seen in AIDS patients
Immunosuppressants (corticosteroids)

Symptoms

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

Headache
Stiff neck, shoulders, or back
Aching of neck, shoulders, or back
Vomiting
Changes in mental status
- Drowsiness
- Confusion
- Inattention
- Irritability
- Slow thought processes
- Decreasing responsiveness
- Eventual coma
Seizures
Fever and chills
Vision changes
Loss of muscle function
Decreased sensation
Decreased movement
Weakness
Decreased speech (aphasia)
Other language difficulties
Loss of coordination

Signs and tests

A neurological exam will usually reveal 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 infecting organism.

Treatment

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

Medication, not surgery, is recommended if you have:

Several abscesses (rare)
A small abscess (less than 2 cm)
An abscess deep within the brain
An abscess and meningitis
Shunts in the brain for hydrocephalus
An underlying disease that makes surgery dangerous

Antibiotics will be given. 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.

Anti-fungal medications may also be prescribed if the infection is likely caused by a fungus.

An abscess that is injuring brain tissue by pressing on it or a large abscess with a high degree of swelling around it can raise intracranial pressure to the point where immediate treatment is needed.

Surgery is needed if :

Pressure in the brain continues or gets worse
The size of the brain abscess does not decrease after medication
The brain abscess contains gas (produced by some types of bacteria)
The brain abscess might rupture

Surgery consists of opening and draining the abscess. Laboratory tests are often done to examine the fluid. This can help identify the infection-causing organism so that more appropriate antibiotics or anti-fungals can be prescribed. The specific surgical procedure 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 scan or MRI scan may be needed for a deep abscess. During this procedure, medications may be directly injected 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%. The earlier treatment is received, the better.

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

Complications

Meningitis, severe and life threatening
Epilepsy
Permanent neurologic losses (vision, speech, movement)
Recurrence of infection

Calling your health care provider

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

Prevention

The risk of developing a brain abscess may be reduced by treating any disorders that can cause them. Such treatment should include 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.

Review Date:10/16/2006
Reviewed By:J.A. Lee, M.D., Assistant Professor of Surgery, Columbia University Medical Center, New York, NY. Review provided by VeriMed Healthcare Network.

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