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Brain / Cerebral Abscess

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Brain abscess (or cerebral abscess) is an abscess caused by inflammation and collection of infected material (pus), coming from local (ear infection, dental abscess, infection of paranasal sinuses, infection of the mastoid air cells of the temporal bone, epidural abscess) or remote (lung, heart, kidney etc.) infectious sources, within the brain tissue. The infection may also be introduced through a skull fracture following a head trauma or surgical procedures. Brain abscess is usually associated with congenital heart disease in young children. It may occur at any age but is most frequent in the third decade of life.


  • Headache in 69-70 % of cases. Pain usually starts on the side of the abscess, and it may begin slowly or suddenly.
  • Fever in 45-53 % of cases
  • Seizures in 25-35 % of cases. A seizure may be the first sign of an abscess.
  • Nausea & vomiting in 40% of cases. Nausea and vomiting tend to occur as pressure builds inside the brain.
  • Changes in mental status occur in 65 percent of cases, and they may lead to:
    • confusion
    • drowsiness and lethargy
    • irritability
    • poor mental focus
    • poor responsiveness
    • slow thought processes
    • coma (possibly)

Neurologic difficulties affect 50–65 percent of people with brain abscesses.

  • These issues often follow a headache, appearing within days or weeks, and they can include:
    • muscle weakness
    • weakness or paralysis on one side of the body
    • speech problems, such as slurred speech
    • poor coordination

Other symptoms may include:

  • a stiff neck, back, or shoulders
  • blurred, double, or graying vision

In babies and young children, most of the symptoms are similar. However, the child may show other symptoms of a brain abscess. The soft spot on top of the baby’s head, called the fontanelle, may be swollen or bulging. Other symptoms in the child can include:

  • projectile vomiting
  • high-pitched crying
  • spasticity in the limbs

The symptoms of a brain abscess result from a combination of infection, brain tissue damage, and pressure on the brain, as the abscess grows to take up more space.

If the headache suddenly becomes worse, it may mean that the abscess has burst.

In two-thirds of cases, symptoms are present for as long as 2 weeks.


  • The source of the infection is often not found. However, the most common source is a lung infection. Less often, a heart infection is the cause.
  • A brain abscess is most likely to result from a bacterial or fungal infection in some part of the brain. Parasites can also cause an abscess.
    • When the bacteria, fungi, or parasites infect part of the brain, inflammation and swelling occur. In these cases, the abscess will consist of infected brain cells, active and dead white blood cells, and the organisms that cause the problem.
  • As the cells accumulate, a wall or membrane develops around the abscess. This helps to isolate the infection and keep it from spreading to healthy tissue.
  • If an abscess swells, it puts increasing pressure on surrounding brain tissue.
  • The skull is not flexible, and it cannot expand. The pressure from the abscess can block blood vessels, preventing oxygen from reaching the brain, and this results in damage or destruction of delicate brain tissue.

The most common infections known to cause brain abscesses are:

  • Endocarditis, an infection of the heart valve
  • Pneumonia, bronchiectasis, and other lung infections and conditions
  • Abdominal infections, such as peritonitis, an inflammation of the inner wall of the abdomen and pelvis
  • Cystitis, or inflammation of the bladder, and other pelvic infections

Brain infections are fairly uncommon as there is a protective network of blood vessels and cells that block certain components from the blood that flows to the brain, but allows others to pass through. However, sometimes, an infection can get through the blood-brain barrier. This can happen when inflammation damages the barrier, leading to gaps. This allows infection to enter the brain through one of these three main routes:

  • The blood from an infection in another part of the body
    • Between 9 and 43% of abscesses result from pathogens that traveled from another part of the body.
  • Spread from a nearby site inside of the skull, such as the ear or nose, such as otitis media, sinusitis, or mastoiditis.
    • An infection can spread from a nearby area, and this accounts for 14-58 % of brain abscesses.
  • Result from a traumatic injury or surgery, such as:
    • a blow to the head that causes a compound skull fracture, in which fragments of bone are pushed into the brain
    • the presence of a foreign body, such as a bullet, if someone does not remove it
    • a complication of surgery, in rare cases

What are the risk factors?

Nearly anyone can get a brain abscess, but certain groups of people are at a higher risk than others. Some diseases, disorders, and conditions that raise your risk include:

  • A person with a weakened immune system has a higher risk of developing a brain abscess from a blood-borne infection. A person may have a weakened immune system if they:
    • have a chronic disease, such as cancer
    • have a weakened immune system (such as HIV / AIDS)
    • are infants under the age of 6 months
    • are receiving corticosteroids (long-term steroid medication) or chemotherapy
    • have had an organ transplant and take immunosuppressant drugs to prevent organ rejection
    • congenital heart disease

Prognosis & Mortality

  • Fewer than 20,000 US cases per year
  • Studies show that 5-32 % of brain abscesses are fatal.
  • While death occurs in about 10% of cases, people do well about 70% of the time. This is a large improvement from the 1960s due to improved ability to image the head, more effective neurosurgery and more effective antibiotics.
  • In the past, a brain abscess was "invariably fatal," but researchers writing in 2014 that progress in diagnosis and treatment have significantly increased the chances of survival.
  • Between 1,500 & 2,500 cases occur each year in the United States. Brain abscesses are most likely to affect adult men aged under 30 years. Among children, they most commonly develop in those aged 4–7 years. Newborns are also at risk.
  • In most modern series, the mortality rate is typically less than 15%. Rupture of a brain abscess infrequently occurs and is associated with a high mortality rate (up to 80%). Significant morbidity, including seizures, persistent weakness, aphasia, or cognitive impairment, affects an estimated at 20-30% of survivors.
  • According to the Children’s Hospital of Wisconsin, infections from other parts of the body account for between 20-50 % of all brain abscess cases. Heart and lung infections are among the most common causes of brain abscesses. (Healthline – Brain Abscess Overview)

Complications of a brain abscess can include:

  • Reoccurring abscess – seek immediate medical advice if you think there's even a small chance your abscess has reoccurred; this is more common in people with a weakened immune system or cyanotic heart disease
  • Brain damage – mild to moderate brain damage often improves with time but severe brain damage is likely to be permanent; brain damage is more of a risk if diagnosis and treatment are delayed
  • Epilepsy – where a person has repeated seizures (fits)
  • Meningitis – a life-threatening infection of the protective membranes around the brain, which requires urgent treatment; this is more common in children

Resources & Additional Reading