A brain abscess is usually caused when bacteria such as staphylococci and streptococci infect part of the brain. In response to the infection, there is inflammation and death of some of the tissues in the brain. Fluid, destroyed tissue cells, white blood cells, and live and dead microorganisms collect and form a mass. This mass usually becomes enclosed by a membrane that forms around it.

The brain swells in response to the inflammation, and the mass may put pressure on the the brain. Infected material can block the blood vessels of the brain, further damaging brain tissues. The pressure within the brain rises, causing more damage and problems.

A brain abscess may result from other infections, such as an epidural abscess, chronic ear infection, chronic sinusitis, or mastoiditis. 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 may also introduce microorganisms into the brain, and the infection may occasionally occur after surgery on the brain or spinal cord. In about 10%-25% 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 throughout the body. Early symptoms are usually headache (about 50% of cases), muscle weakness, loss of sensation, or seizures.

People at higher risk include those with 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 drug abuse, chronic ear infections, chronic sinusitis, infections that spread bacteria to the bloodstream (bacteremia), and any condition that harms the immune system.

• 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 (occurs in less than 50% of people)
• Localized loss of nerve functions (focal neurologic deficits)
  • Vision changes
  • Muscle function/feeling loss
  • Decreased sensation (arm and leg on the same side of the body)
  • Decreased movement (arm and leg on the same side of the body)
  • Weakness of an area (arm and leg on the same side of the body)
  • Decreased speech (aphasia)
  • Loss of coordination

Note: Symptoms may develop gradually, over a period of 2 weeks, or they may develop suddenly. Once symptoms occur, they progressively worsen.

Additional symptoms that may be associated with this disease:

• Movement - dysfunctional
• Eyes, pupils different size

A physical examination will usually reveal increased intracranial pressure and problems with brain function. The problems will relate to the area of the brain where the abscess is located. The physician also may discover a possible source of the infection.

An eye examination may show loss of eye movement and swelling of the optic nerve (a sign of increased intracranial pressure).

• A CBC may indicate infection or inflammation.
• Blood cultures will reveal any bacteria in the bloodstream.
• A chest X-ray will reveal lung infections (one of the more common sources of infection).
• An EEG may be abnormal if seizures or focal neurologic deficits are present.
• A cranial CT scan or MRI of head shows the abscess and its exact location.

This disease may also alter the results of the following tests:

• CSF collection
• ADH

Cerebral abscess is a medical emergency! Intracranial pressure may become high enough to cause fatal brainstem herniation. Hospitalization is required until the condition is stabilized.

Life support (such as breathing and circulation assistance) may be required in some cases.

Medical management is advised for multiple abscesses, a small (less than 2 cm) abscess, an abscess deep within the brain, an abscess accompanied by meningitis, the presence of shunts in the brain (for hydrocephalus), or an underlying disease that makes surgery dangerous (debilitating disease).

Antimicrobials are given, initially through a vein, then by mouth. Between 2 and 6 weeks of medication are usually required. Broad-spectrum antibiotics are the most common antimicrobial prescribed. Multiple medications may be used together. Antifungal medications (or antiviral medications) may also be prescribed if fungal or viral infection is likely.

Osmotic diuretics such as urea or mannitol are used to reduce swelling of the brain. If mannitol is used, then one should consider surgery to evacuate the lesion and reduce the mass effect. Corticosteroids such as dexamethasone also might be used to reduce brain swelling, but their use is very controversial.

Surgery is indicated if there is persistent or progressive increase in intracranial pressure, if the mass does not reduce after use of antimicrobial medications, or if the mass contains gas (produced by some types of bacteria). It may also be needed if there are signs of impending rupture of the abscess into the ventricle.

Surgery consists of opening and draining the abscess and is usually accompanied by cultures of the fluid. This allows antimicrobial treatment to be adjusted so that it is specific to the causative microorganism. The specific surgical procedure depends on the size and depth of the mass. The entire mass may be removed (excised) if it is near the surface and completely encapsulated. A CT scan-guided needle aspiration may be needed for deep abscess. This may also include injecting antimicrobials directly into the mass.

If untreated, the disorder is uniformly fatal. The outcome is usually improved with the use of CT scans for accurate diagnosis and administration of broad-spectrum antimicrobials.

Death rate is around 10% with treatment. Neurologic changes may be chronic. Seizures or neurologic losses may occur after surgery. Infection may spread and cause severe life-threatening meningitis.

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

Go to the emergency room or call the local emergency number (such as 911) if symptoms occur. Cerebral abscess is a medical emergency!

Thorough treatment of causative disorders, including follow-up examination after treatment of infections, may reduce the risk of cerebral abscess.

Surgical repair of congenital disorders such as tetralogy of Fallot may reduce the risk of infections.

Preventive (prophylactic) antibiotics given for people with congenital or rheumatic heart disorders prior to dental or urologic procedures may reduce the risk.