Cerebral abscess

Alternative names:

abscess - brain; brain abscess; CNS abscess

Definition:

A space-occupying lesion in the brain caused by an inflammation and a collection of infected material (pus) within the brain tissue.

Causes, incidence, and risk factors:

When microorganisms (usually bacteria such as staphylococci and streptococci) cause a localized infection in the brain, there is inflammation in response to the infection, with death (necrosis) of some of the tissues of the brain. Fluid, destroyed tissue cells, white blood cells, and live and dead microorganisms collect and form a mass. This mass usually becomes enclosed (encapsulated) by a lining (membrane) that forms at the edges of the fluid collection.

There is swelling within the brain in response to the inflammation, and the mass may put pressure on the structures of the brain. Infected material can close up (occlude) the vessels of the brain, further damaging brain tissues. The pressure within the brain (intracranial) rises causing more extensive damage and dysfunction.

Cerebral abscess may be a complication of epidural abscess. Chronic ear infection, chronic sinusitis, and mastoiditis are other initial sources of the infection that causes cerebral abscess. The infection may be caused by direct spread of the microorganisms through the bones of the skull and through the membranes covering the brain (meninges).

The infection may also spread through the blood vessels from distant locations in the body. Lung infections such as empyema or lung abscess are common sources. Other sources include infections of the teeth, skin, bone, or heart. Direct head injury (trauma) may also introduce microorganisms into the brain, and the infection may occasionally occur after surgery on the brain or spinal cord. In about 10% of cases, no original source of the infection can be identified.

Symptoms may develop gradually or suddenly. There is usually little or no sign of general infection in the body (systemic). Early symptoms are usually headache (about 50% of cases), neurologic losses (such as muscle weakness or loss of sensation), or seizures.

Risks include congenital heart diseases such as Tetralogy of Fallot and congenital blood vessel abnormalities of the lungs such as Osler-Weber-Rendu disease. These disorders carry a high risk of infection of the heart or lungs, which can then spread to the brain. Other risks include illicit (particularly intravenous) drug use, chronic ear infections, chronic sinusitis, infections that spread bacteria to the bloodstream (bacteremia), and any condition that reduces the functioning of the immune system.

Cerebral abscess occurs in approximately 1 out of 100,000 people. It may affect people of any age, race, or gender.