A pus-filled swelling in the brain caused by bacterial or fungal infection
- More common in males
- Intravenous drug abuse is a risk factor
- Age and Genetics are not significant factors
Brain abscesses are collections of pus. They are rare and, if left untreated, can be life-threatening. Pus may collect to form a single abscess or may form several abscesses in different parts of the brain. Brain tissue around the abscess or abscesses becomes compressed, and the brain itself may swell, increasing pressure inside the skull.
People who have impaired immunity, including those with HIV infection (see HIV infection and AIDS) and those having chemotherapy, are more likely to develop a brain abscess. The risk of a brain abscess is also higher in intravenous drug users than in other people because reused needles may be contaminated with infectious microorganisms. Men are twice as likely as women to develop a brain abscess.
What are the causes?
Most brain abscesses are caused by a bacterial infection that has spread to the brain from an infection in nearby tissues in the skull. For example, the infection may spread from a dental abscess or from an infection in the sinuses (see Sinusitis). If the skull is penetrated (see Head injuries), bacteria may enter the brain and cause infection. Bacterial infection can also be carried in the bloodstream to the brain from an infection in another part of the body, such as the lungs (see Pneumonia) or the heart (see Infective endocarditis). In a few cases, the source of the infection cannot be found. Occasionally, a brain abscess may be the result of a fungal infection or, particularly in people with HIV/AIDS, of the protozoal infection toxoplasmosis.
What are the symptoms?
The symptoms of a brain abscess may develop in a few days or gradually over a few weeks. They may include:
Nausea and vomiting.
Other symptoms, including speech and vision problems or weakness of one or more limbs, may develop depending on which part of the brain is affected. Without treatment, consciousness may be impaired and may lead to coma.
What might be done?
If your doctor suspects a brain abscess, you will be admitted to hospital immediately. The diagnosis can be confirmed by MRI or CT scanning of the head. You may have blood tests to identify the infecting organism and X-rays to look for its source.
Brain abscesses caused by bacterial infections are treated with high doses of antibiotics, given intravenously at first and then orally for about 6 weeks. If the abscess is large or causing considerable brain swelling, a small hole may be drilled through the skull under general anaesthesia to allow pus to drain. The pus is then analysed to identify the infecting organism. You may have corticosteroids to control swelling of the brain. Anticonvulsant drugs may be prescribed to reduce the risk of seizures. In severe cases, mechanical ventilation in an intensive therapy unit may be needed.
What is the prognosis?
Up to 8 in 10 people recover from a brain abscess if treatment is begun early. However, some have persistent problems, such as seizures, slurred speech, or weakness of a limb.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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