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Brain Abscess Clinical Presentation

  • Author: Itzhak Brook, MD, MSc; Chief Editor: Pranatharthi Haran Chandrasekar, MBBS, MD  more...
Updated: Oct 05, 2015


In about two thirds of patients, symptoms are present for 2 weeks or less. The clinical course ranges from indolent to fulminant.

Most symptoms are a result of the size and location of the space-occupying lesion or lesions.

The triad of fever, headache (often severe and on the side of the abscess), and focal neurologic deficit occurs in less than half of patients. The frequency of common symptoms and signs is as follows:[1]

  • Headache - 70%
  • Mental status changes (may indicate cerebral edema) - 65%
  • Focal neurologic deficits - 65%
  • Fever - 50%
  • Seizures - 25-35%
  • Nausea and vomiting - 40%
  • Nuchal rigidity - 25%
  • Papilledema - 25%

A suddenly worsening headache, followed by emerging signs of meningismus, is often associated with rupture of the abscess.



The clinical manifestations of brain abscess are initially nonspecific, which can lead to delay in diagnosis. Brain abscess usually manifests as symptoms of a space-occupying lesion. The symptoms and signs include the following:

  • Low-grade or high-grade fever
  • Persistent headache (often localized)
  • Drowsiness
  • Confusion
  • Stupor
  • General or focal seizures
  • Nausea and vomiting
  • Focal motor or sensory impairments
  • Papilledema
  • Ataxia
  • Hemiparesis
  • Neck stiffness

Localized neurologic signs are eventually found in most patients. The signs and/or symptoms are a direct function of the intracranial location of the abscess, as follows:

  • Cerebellar abscess - Nystagmus, ataxia, vomiting, and dysmetria
  • Brainstem abscess - Facial weakness, headache, fever, vomiting, dysphagia, and hemiparesis
  • Frontal abscess - Headache, inattention, drowsiness, mental status deterioration, motor speech disorder, hemiparesis with unilateral motor signs, and grand mal seizures
  • Temporal lobe abscess - Headache, ipsilateral aphasia (if in the dominant hemisphere), and visual defects
  • Occipital abscess- Neck rigidity

In the initial stages of the infection, an abscess can manifest as a nonspecific form of encephalitis accompanied by signs of increased intracranial pressure.

The headache associated with brain abscess can gradually develop or suddenly emerge and is often localized to the abscess' side. It is often severe and is not relieved by mild pain medications.

Papilledema may develop in older child and adults, and younger infants may exhibit bulging fontanels. This is a late expression of cerebral edema.

A ruptured brain abscess may produce purulent meningitis associated with signs of neurologic damage.

Vomiting commonly develops in association with increased intracranial pressure. Changes in mental status (lethargy progressing to coma) suggest severe cerebral edema.

Specific clinical symptoms are characteristic of some pathogens.



The microbial etiology depends on the patient's age, site of primary infection, and the patient's immune status.[14, 15]

Anaerobic and microaerophilic cocci and gram-negative and gram-positive anaerobic bacilli are the most important isolates. A significant number of brain abscesses are polymicrobic.[14, 15, 16, 17]

Oral flora anaerobes generally originate from infected ears and sinuses and abdominal anaerobes (Bacteroides fragilis group) reach the intracranial cavity through bacteremia.

The predominant organisms include the following:

  • Staphylococcus aureus, including methicillin-resistant [18]
  • Aerobic, anaerobic, and microaerophilic streptococci, including alpha-hemolytic streptococci and Streptococcus anginosus (milleri) group ( Streptococcus anginosus, Streptococcus constellatus, and Streptococcus intermedius)
  • Prevotella and Fusobacterium species and B fragilis
  • Enterobacteriaceae ( Klebsiella pneumoniae, Escherichia coli, and Proteus species)
  • Pseudomonas species
  • Other anaerobes (Veillonella, Eubacterium)

Less common causes include the following:

  • H influenzae
  • Streptococcus pneumoniae
  • Neisseria meningitidis
  • Haemophilus aphrophilus
  • Other Enterobacteriacae (Enterobacter species, Actinobacillus, actinomycetemcomitans, and Salmonella species)
  • Actinobacillus actinomycetemcomitans
  • Actinomyces
  • Nocardia asteroides
  • Mycobacterium species
  • Fungi (eg, Aspergillus, Candida, Cryptococcus, Mucorales, Coccidioides, Histoplasma capsulatum, Blastomyces dermatitidis, Bipolaris, Exophiala dermatitidis, Curvularia pallescense, Ochronosis gallopava, Ramichloridium mackenziei)
  • Protozoa (eg, Toxoplasma gondii, Entamoeba histolytica, Trypanosoma cruzi, Schistosoma, Paragonimus)
  • Helminths (eg, Taenia solium)
  • T gondii
  • Pseudallescheria boydii

The following organisms are associated with certain predisposing conditions:[19]

  • Sinus and dental infections - Aerobic and anaerobic streptococci, anaerobic gram-negative bacilli (eg, Prevotella, Porphyromonas, Bacteroides, Fusobacterium), microaerophilic streptococci (mainly Streptococcus milleri), Haemophillus, S aureus, Enterobacteriaceae) [16]
  • Ear infections (including mastoiditis) - Aerobic and anaerobic streptococci, anaerobic gram-negative bacilli, Haemophillus, Pseudomonas, and Enterobacteriaceae
  • Pulmonary infections - Aerobic and anaerobic streptococci, anaerobic gram-negative bacilli (eg, Prevotella, Porphyromonas, Bacteroides), Fusobacterium, Actinomyces, Nocardia [11]
  • Endocarditis - Alpha hemolytic streptococci, S aureus
  • Congenital heart disease - Aerobic and microaerophilic streptococci, S aureus
  • Liver abscess or diabetes mellitus (reported in Southeast Asia) - Klebsiella pneumoniae [20]
  • Penetrating trauma - S aureus, aerobic streptococci, Enterobacteriaceae, Clostridium
  • Neurosurgical procedures- S aureus, Pseudomonas, Enterobacter, Propionibacterium acnes [21]
  • Neonates - Citrobacter [22]
  • Urinary tract-Pseudomonas, Enterobacteriaceae, Enterobacter
  • Transplantation - Aspergillus, Candida, Cryptococcus, Mucorales, Nocardia, T gondii [10]
  • Immunocompromised - Aerobic gram-negative bacilli, T gondii, Nocardia asteroids, Listeria monocytogenes, Aspergillus, Cryptococcus, Coccidioides immitis, Candida, Mucorales [23, 24, 25]
  • HIV infection - T gondii, Mycobacterium, Cryptococcus, Nocardia, L monocytogenes [12]
  • Living, visiting, or immigrating from an endemic area: Taenia solium (causing cysticercosis), Schistosoma japonicum, Entamoeba histolytica, and Paragonimus species.

Al Masalma et al performed a 16S rDNA-based metagenomic analysis of cerebral abscesses and identified 80 distinct bacterial taxa, including 44 not previously described in brain abscess. Therefore, microbial flora of brain abscesses is far from being fully known and is differentially distributed depending on the abscess etiology. Further studies are warranted to determine the significance of the identification of the newly recovered bacteria associated within brain abscesses.[26]

Contributor Information and Disclosures

Itzhak Brook, MD, MSc Professor, Department of Pediatrics, Georgetown University School of Medicine

Itzhak Brook, MD, MSc is a member of the following medical societies: American Association for the Advancement of Science, American College of Physicians-American Society of Internal Medicine, American Medical Association, American Society for Microbiology, Association of Military Surgeons of the US, Infectious Diseases Society of America, International Immunocompromised Host Society, International Society for Infectious Diseases, Medical Society of the District of Columbia, New York Academy of Sciences, Pediatric Infectious Diseases Society, Society for Experimental Biology and Medicine, Society for Pediatric Research, Southern Medical Association, Society for Ear, Nose and Throat Advances in Children, American Federation for Clinical Research, Surgical Infection Society, Armed Forces Infectious Diseases Society

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Chief Editor

Pranatharthi Haran Chandrasekar, MBBS, MD Professor, Chief of Infectious Disease, Program Director of Infectious Disease Fellowship, Department of Internal Medicine, Wayne State University School of Medicine

Pranatharthi Haran Chandrasekar, MBBS, MD is a member of the following medical societies: American College of Physicians, American Society for Microbiology, International Immunocompromised Host Society, Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Additional Contributors

Jeffrey D Band, MD, FACP, FIDSA Professor of Medicine, Oakland University William Beaumont School of Medicine; Health System Chair, Healthcare Epidemiology and International Medicine, Beaumont Health System; Former Chief of Infectious Diseases, Beaumont Hospital; Clinical Professor of Medicine, Wayne State University School of Medicine

Disclosure: Nothing to disclose.

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CT scan of a brain abscess.
MRI of a brain abscess.
Brain abscess.
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