A brain abscess is a collection of pus, immune cells, and other material in the brain, caused by a bacterial or fungal infection.
Abscess - brain; Cerebral abscess; CNS abscess
Brain abscesses commonly occur when bacteria or fungi infect part of the brain. As a result, swelling and irritation (inflammation) develop. Infected brain cells, white blood cells, live and dead bacteria or fungi collect in an area of the brain. Tissue forms around this area and creates a mass or abscess.
The germs that cause a brain abscess can reach the brain through the blood. Or, they enter the brain directly, such as during brain surgery. In some cases, a brain abscess develops from an infection in the sinuses.
The source of the infection is often not found. However, the most common identified source is a lung infection. Less often, a heart infection is the cause.
The following raise your chance of developing a brain abscess:
Symptoms may develop slowly, over a period of several weeks, or they may develop suddenly. They may include:
A brain and nervous system (neurological) exam will usually show signs of increased pressure inside the skull and problems with brain function.
Tests to diagnose a brain abscess may include:
A needle biopsy is usually performed to identify the cause of the infection.
A brain abscess is a medical emergency. Pressure inside the skull may become high enough to be life threatening. You will need to stay in the hospital until the condition is stable. Some people may need life support.
Medicine such as an antibiotic, not surgery, is recommended if you have:
You may be prescribed several different types of antibiotics to make sure treatment works.
Antifungal medicines may also be prescribed if the infection is likely caused by a fungus.
Surgery is needed if:
Surgery consists of opening the skull, exposing the brain, and draining the abscess. Laboratory tests are often done to examine the fluid. This helps identify the cause of the infection, so that the right antibiotics or antifungal medicine can be prescribed.
Needle aspiration guided by CT or MRI scan may be needed for a deep abscess. During this procedure, medicines may be injected directly into the mass.
Certain diuretics (medicines that reduce fluid in the body, also called water pills) and steroids may also be used to reduce the swelling of the brain.
If untreated, a brain abscess is almost always deadly. With treatment, the death rate is about 10% to 30%. The earlier treatment is received, the better.
Some people may have long-term nervous system problems after a brain abscess or surgery.
Complications may include:
Go to a hospital emergency room or call 911 or the local emergency number if you have symptoms of a brain abscess.
You can reduce the risk of developing a brain abscess by getting treated for infections or health problems that can cause them.
Some people, including those with certain heart disorders, may receive antibiotics before dental or other procedures to help reduce the risk of infection.
Gea-Banacloche JC, Tunkel AR. Brain abscess. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 90.
Nath A, Berger JR. Brain abscess and parameningeal infections. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 385.
Reviewed By: Jatin M. Vyas, MD, PhD, Associate Professor in Medicine, Harvard Medical School; Associate in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.