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Brain Abscess

Last updated Aug. 6, 2018

Approved by: Krish Tangella MD, MBA, FCAP

Pus may get accumulated in the brain, due to an infection within the brain (infection of the layers covering the brain, called as meningitis), or it may spread from anatomic structures that are close to the brain, like from an ear infection, sinus infection, mastoid infection. A collection of pus inside the brain is termed as a Brain Abscess.

What are the other Names for this Condition? (Also known as/Synonyms)

  • Intracranial Abscess
  • Parenchymal Intracranial Abscess
  • Subdural Empyema

What is Brain Abscess? (Definition/Background Information)

  • A collection of pus inside the brain is termed as a Brain Abscess
  • Brain is covered by 3 different layers for protection. The upper and sturdiest layer is the ‘dura’. When pus is accumulated above this layer, it is known as an Epidural Abscess
  • When it occurs below this layer, it is known as Subdural Abscess. It is a serious condition that necessitates an emergency evaluation and treatment
  • Pus may get accumulated in the brain, due to an infection within the brain (infection of the layers covering the brain, called as meningitis), or it may spread from anatomic structures that are close to the brain, like from an ear infection, sinus infection, mastoid infection
  • A surgery or trauma to the brain may also result in Brain Abscess. It has also been observed that there is an association between Brain Abscess and congenital heart disease
  • A CT or MRI scan can indicate a Brain Abscess, which may be treated using antibiotics intravenously, or through surgical incision and drainage of abscess
  • However, a poor prognosis is associated with abscess that are multiple, deep, or if any associated neurological damage is observed

Who gets Brain Abscess? (Age and Sex Distribution)

  • Brain Abscess is normally seen in children and young adults, up to age 40 years. It is common during the first four decades of life
  • Men are affected more than woman

What are the Risk Factors for Brain Abscess? (Predisposing Factors)

The risk factors of Brain Abscess include:

  • Bacterial meningitis (infection of the layers of the brain) is a common predisposing factor. This was a more common factor, before suitable vaccines were available. Now, it is seen in children, who are not immunized against the bacterium Hemophilus influenza
  • Congenital heart disease
  • Dental cavities and sinus infection are important risk factors in adults
  • Immunocompromised conditions like AIDS, patients on chemotherapy for cancers, chronic prednisone treatment, are also risk factors for Brain Abscesses
  • If there is a brain trauma (that causes a break in the skin), the bacteria present on the skin (or in the environment) may find its way into the brain, resulting in a Brain Abscess
  • When there is infection of the heart valves (infective endocarditis), there is a possibility of this infection spreading to the brain, leading to a Brain Abscess. Intravenous drug abuse is a high risk factor in such a clinical scenario

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Brain Abscess? (Etiology)

  • Some of the most common bacterial pathogens causing Brain Abscess in children include Hemophilus influenza, Pneumococcus, and Enterobacter
  • In adults, bacteria like Staphylococcus, Streptococcus, Bacteroides, Prevotella, Fusobacterium, and Enterobacter, can cause Brain Abscess. Microorganisms, like Actinomyces and Nocardia, may also cause abscess in the brain
  • When there is a penetrating trauma to the head - bacteria, like Staphylococcus, Streptococcus, and Clostridium, can cause Brain Abscess
  • In intravenous drug abusers, bacteria present on the skin, like Staphylococcus epidermidis or Staphylococcus aureus, can enter the skin and infect the heart valves
  • In individuals with AIDS or any other immunocompromised state, Toxoplasma, Mycobaterium, and Nocardia, are the common bacterial pathogens observed to cause this brain condition
  • Fungal infections, like Cryptococcus and Aspergillus, may also result in Brain Abscess

What are the Signs and Symptoms of Brain Abscess?

Common signs and symptoms of a Brain Abscess include fever and chills, headaches, changes in mental status, nausea, and vomiting.

  • Seizures and neck stiffness may be seen in some patients
  • Focal motor and sensory neurological deficits, along with altered mental status are common
  • If the abscess is located in the cerebellum (small brain) - nystagmus (erratic movement of eyeball with gaze) along with a lack of balance and unsteady gait are seen
  • When the abscess is in the brainstem, facial muscles may weaken, and the patient may have difficulty in swallowing. Also, there may be a weakness and/or paralysis, affecting one half of the body (hemiparesis)
  • Abscesses in the back side of the brain (occipital lobe) are characterized by neck rigidity; whereas, abscess in the front part of the brain (frontal lobe) is frequently present with inattention, speech disorders, and seizures
  • If the abscess is in the temporal lobe (on the lower part of the brain), there may be visual defects and the patient may have difficulty speaking, reading, writing, recognizing the names of objects, or difficulty understanding what other people say

How is Brain Abscess Diagnosed?

Some of the common tools to diagnose a Brain Abscess include:

  • Physical examination with thorough medical history evaluation
  • Brain Abscess is diagnosed by CT scan of the head. An MRI brain scan provides a better image of the abscess
  • Complete blood count with differential count and ESR (erythrocyte sedimentation rate) may be elevated, indicating an infection
  • Culture studies to grow the organism are performed; blood cultures must be obtained, before starting any antibiotics course
  • Aspirate of the abscess is obtained via stereotactic CT guidance, or surgery and staining tests, such as:
    • Gram stain
    • Acid-fast stain (to diagnose Mycobacterium)
    • Modified acid-fast stain (for Nocardia)
    • Other stains, such as methenamine silver to diagnose fungi
  • Histopathological examination of the brain tissue may be performed - the specimen is examined under a microscope by a pathologist, to arrive at a definitive diagnosis
  • Special tests, like PCR (polymerase chain reaction) that help in delineating organisms, like Toxoplasma, and other serological tests may be required to pick up antibodies in parasitic diseases, like neurocysticercosis
  • A lumbar puncture (puncturing in the back to take out some brain fluid) is not recommended, when there is a Brain Abscess

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Brain Abscess?

Complications of Brain Abscess may include:

  • Permanent neurological damage
  • Paralysis of one half of the body
  • Cranial nerve palsies
  • Intelligence and development may be retarded
  • A possible sequel may be a seizure disorder

How is Brain Abscess Treated?

The treatment of Brain Abscess may involve:

  • Administration of intravenous antibiotics and surgical drainage of the abscess is the standard treatment provided
  • Long-term intravenous, antifungal treatment may be necessary, if fungal organisms are the causative agents, especially in immunocompromised patients

How can Brain Abscess be Prevented?

A key factor in preventing Brain Abscesses is to reduce the risks for this condition.

  • Immunization of children helps prevent meningitis
  • Prophylactic antibiotics may be given, prior to urological or dental procedures in those with congenital heart disease. Proper oral hygiene helps prevent dental infections
  • Sinus infections may be managed with decongestants and if it does not improve, then it must be managed with antibiotics
  • AIDS infection can be prevented by safe sexual practices and avoidance of sexually-promiscuous behavior
  • Avoiding hazardous lifestyle habits, like IV drug abuse, are beneficial in many ways

What is the Prognosis of Brain Abscess? (Outcomes/Resolutions)

  • Multiple Brain Abscesses and abscesses located deep within brain tissue are associated with bad prognosis
  • When the patient presents with coma or advanced neurological damage, it indicates an unfavorable prognosis. Also, typically the prognosis is not good in immunosuppressed patients
  • An early detection and treatment of Brain Abscess may yield a better prognosis

Additional and Relevant Useful Information for Brain Abscess:

  • Superficial abscess drainage involves the opening and draining of an abscess. An abscess is a collection of pus (observed with a swelling), occurring on any part of the body

The following article link will help you understand superficial abscess drainage surgical procedure:


What are some Useful Resources for Additional Information?

References and Information Sources used for the Article:

Helpful Peer-Reviewed Medical Articles:

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Sept. 29, 2014
Last updated: Aug. 6, 2018