Brain abscess


Brain abscesses are caused by bacteria entering the bloodstream through a break in the skin. They usually form when there is an injury to the head, neck, face, or teeth.

This allows bacteria to enter the blood stream and travel to the brain. Once inside the brain, the bacteria multiply and cause swelling.

This causes pressure on nearby nerves and may lead to seizures.

Brain abscess is more likely to affect adult males under the age of 30. 

In children, they most often develop in those between 4 and 7 years old. Vaccination programs have reduced the incidence of brain abscesses in young children.

Brain Abscess Symptoms

Brain abscess symptoms include headache, fever, nausea, vomiting, stiff neck, confusion, seizures, loss of consciousness, coma, and death.

The most common cause of brain abscesses is bacterial infection. Other causes include fungal infections, trauma, tumors, and autoimmune diseases.

If the headache suddenly gets worse, the abscess may have burst.

In two-thirds of cases, symptoms last up to 2 weeks. On average, doctors diagnose the disease 8 days after the onset of symptoms.

The causes of brain abscess

Brain abscesses are caused by bacteria, fungi, or amoebae that enter the brain.

Brain abscesses are caused by bacteria, fungi, or amoebae that enter the brain. The most common cause is bacterial meningitis.

Brain abscesses can also be caused by tuberculosis or fungal infections of the sinuses or ear.

As the cells accumulate, a wall or membrane develops around the abscess. This isolates the infection and prevents it from spreading to healthy tissue.

If an abscess swells, it puts increasing pressure on surrounding brain tissue.

How the infection enters the brain

Brain infections are quite rare for several reasons.

One reason is the blood-brain barrier, a protective network of blood vessels and cells. It blocks certain components of blood flowing to the brain.

Sometimes an infection can cross the blood-brain barrier. This can happen when inflammation damages the barrier.

The infection enters the brain through three main routes.

It could:

  • by blood;
  • from a neighboring site, for example the ear;
  • result from traumatic injury or surgery

Infection from another area of ​​the body

If an infection occurs elsewhere in the body, infectious organisms can bypass the blood-brain barrier and enter and infect the brain.

Many bacterial brain abscesses arise from a lesion in the body. 

A person with a weakened immune system (for example caused by chemotherapy or an organ transplant) has a higher risk of developing a brain abscess as a result of a blood-borne infection.

The most common infections known to cause brain abscesses are:

  • endocarditis, an infection of the heart valve
  • pneumonia, bronchiectasis and other lung infections
  • an abdominal infection such as peritonitis,
  • cystitis or inflammation of the bladder.

Direct contagion

An untreated middle ear infection can lead to a brain abscess. If an infection starts inside the skull, for example in the nose or ear, it can spread to the brain.

Infections that can trigger a brain abscess include:

  • ear infection;
  • sinusitis;
  • mastoiditis, an infection of the bone behind the ear.

The location of the abscess may depend on the site and type of the original infection.

Direct trauma

A brain abscess can result from neurological surgery or brain injury.

An abscess can result from:

  • a blow to the head that causes a skull fracture,
  • a complication of surgery, in rare cases.

Diagnosis of brain abscess

To diagnose a brain abscess, the doctor will assess the signs and symptoms and review the patient’s medical history and recent movements.

Symptoms can be similar to those of other illnesses and conditions, so confirming a diagnosis can take time. The diagnosis will be easier if the doctor can determine exactly when the symptoms started and how they progressed.

Tests may include:

  • a blood test to check for high levels of white blood cells, which may indicate an infection
  • imaging scans, such as an MRI or CT scan,
  • biopsy which consists of taking a sample of pus for analysis.

The number of deaths from brain abscess has declined over the past decades, due to the increasingly common use of neuroimaging.

Brain abscess treatment

Treatment usually involves surgical drainage of the pus through an incision into the skull (craniotomy). Antibiotics should also be given intravenously to fight any infection that might have caused the abscess in the first place. After the infection is eliminated, a long-acting antibiotic may be given orally to help prevent future recurrences.

If tests show an infection is viral rather than bacterial, the doctor will change treatment accordingly.

The effectiveness of the treatment will depend on:

  • the size of the abscess
  • number of abscesses
  • the cause of the abscess
  • how the person is healthy


A person may need surgery if:

  • the pressure in the brain continues to rise
  • the abscess does not respond to medication
  • there is a risk that the abscess will burst

A craniotomy is a procedure in which the surgeon makes an opening in the skull.


A short course of high-dose corticosteroids can help with increased intracranial pressure and risk of complications, such as meningitis.

However, doctors do not routinely prescribe corticosteroids.

A doctor can prescribe anticonvulsants to prevent seizures. A person who has had a brain abscess may need to take anticonvulsants for up to 5 years.