Brain abscess

Injury	Disease	Nutrition	Poison

Symptoms	Surgery	Test	Special Topic

Amebic brain abscess

Brain abscess

Definition:

A brain abscess is a mass of immune cells, pus, and other material that can occur when the brain is infected by bacteria or fungus.

Alternative Names:
Abscess - brain; Cerebral abscess; CNS abscess
Causes, incidence, and risk factors:

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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 in response to the inflammation, and the mass may put pressure on delicate brain tissue.

Infected material can block the blood vessels of the brain, further damaging tissues by causing cell death and swelling of additional cells. Multiple abscesses are uncommon except in immunocompromised patients.

The bacteria or fungi can reach the brain through the blood, by traveling from a neighboring infected area, or by direct contamination from an injury or surgery. Most commonly, the infectious organism reaches the brain via the bloodstream. The source of the infectious organism is often not found. When identified, the most common source is a lung infection.

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 other sources (such as the intestines or teeth). Also, individuals with Osler-Weber-Rendu syndrome and similar conditions are prone to developing brain abscesses.

A brain abscess can develop by direct extension from an adjacent infected area. For example, infections of the middle ear and mastoid sinuses can spread to the brain.

A brain abscess can develop following a penetrating trauma through the skull, such as a gun or knife wound. This risk of infection is higher if fragments and dead tissue are left behind, and if antibiotic therapy is not started immediately. Surgery, especially when the air sinuses were opened or a foreign body was left in the brain (intracranial pressure monitor, stimulating electrode), can result in an infection.

Symptoms may develop gradually or suddenly. There may be little or no sign of general infection throughout the body. Early symptoms are usually headache, muscle weakness, visual changes, difficulty with balance or coordination, or seizures.

People at higher risk of developing a brain abscess include those with right-to-left heart shunts, a chronic debilitating illness like cancer, who are immunocompromised (such as AIDS patients) and those taking immunosuppressants (corticosteroids).