eMedicine Specialties > Infectious Diseases > CNS Infections

Brain Abscess: Differential Diagnoses & Workup

Author: Itzhak Brook, MD, MSc, Professor, Department of Pediatrics, Georgetown University School of Medicine
Contributor Information and Disclosures

Updated: Jun 26, 2008

Differential Diagnoses

Cryptococcosis
Cysticercosis
Epidural Abscess
Meningitis

Other Problems to Be Considered

Infectious

Cranial osteomyelitis
Encephalitis
Epidural abscess
Mycotic aneurism
Subdural empyema
Suppurative thrombophlebitis

Noninfectious

Cerebral infarct
Hemorrhage
Headache, Migraine
Primary or metastatic tumor
Venous sinus thrombosis
Any other space-occupying CNS lesion

Workup

Laboratory Studies

  • Routine tests
    • CBC count with differential and platelet count
    • Erythrocyte sedimentation rate (ESR; elevated in up to two thirds of patients)
    • Serum C-reactive protein (CRP) or Westergren sedimentation rate
    • Serological tests for some pathogens (eg, serum immunoglobulin G antibodies, CSF polymerase chain reaction [PCR] for Toxoplasma)
    • Blood cultures (at least 2; preferably before antibiotic usage)
    • Moderate leukocytosis is present, and the ESR and CRP level are generally elevated. Serum sodium levels may be low because of inappropriate antidiuretic hormone production. Platelet counts may be high or low.
  • Cerebrospinal fluid17
    • A lumbar puncture is rarely warranted and is contraindicated if increased intracranial pressure is present because of the potential for CNS herniation and death. The results are usually unrewarding, consisting of an elevated protein level, pleocytosis with variable neutrophil count, a normal glucose level, and sterile cultures. A lumbar puncture is mostly of value to rule out other disease processes, especially bacterial meningitis. CT imaging prior to lumbar puncture is absolutely indicated upon the presence of any focal neurologic finding or papilledema.
    • The white blood cell count is generally high. It reaches 100,000/µL or higher when the abscess ruptures into the CSF. Many red blood cells are generally observed at that time, and the CSF lactic acid level is then elevated to more than 500 mg.
  • Abscess aspirate (obtained via stereotactic CT or surgery)2
    • Culture aspirates of abscesses for aerobic, anaerobic, and acid-fast organisms and fungi
    • Gram stain, acid-fast stain (for Mycobacterium), modified acid-fast stain (for Nocardia), and special fungal stains (eg, methenamine silver, mucicarmine)
    • Histopathological examination of the brain tissue

Imaging Studies

  • CT scanning has made other tests, such as angiography, ventriculography, pneumoencephalography, and radionuclide brain scanning, almost obsolete.
    • CT scanning, preferably with contrast administration, provides a rapid means of detecting the size, the number, and the location of abscesses, and it has become the mainstay of diagnosis and follow-up care. This method is used to confirm the diagnosis, to localize the lesion, and to monitor the progression after treatment. However, CT scan results can lag behind clinical findings.18
    • After the injection of a contrast material, CT scans characteristically show the brain abscess as a hypodense center with a peripheral uniform enhancement ring. Rarely, a well-organized abscess wall fails to generate such ring enhancement.
    • In the earlier cerebritis stages, CT scans show nodular enhancement with areas of low attenuation without enhancement. As the abscess forms, contrast enhancement is observed. After encapsulation, the contrast material cannot help differentiate the clear center and the CT scan is similar in appearance to those obtained during the early cerebritis stage.
  • Many authorities consider MRI to be the first diagnostic method in the diagnosis of brain abscess. It allows for accurate diagnosis and excellent follow-up of the lesions because of its superior sensitivity and specificity. Compared with CT scanning, MRI offers a better ability to detect cerebritis, greater contrast between cerebral edema and the brain, and earlier detection of satellite lesions and the spread of inflammation into the ventricles and subarachnoid space.
  • Contrast enhancement with gadolinium diethylenetriaminepentaacetic acid (a paramagnetic agent) helps differentiate the abscess, the enhancement ring, and the cerebral edema around the abscess. T1-weighted images enhance the abscess capsule, and T2-weighted images can demonstrate the edema zone around the abscess.19
  • Diffusion-weighted (magnetic resonance) imaging (DWI) can be used to differentiate between ring-enhancing lesions caused by brain abscess (hypertensive on DWI) from a malignant lesion (hypotensive on DWI).20
  • Since the advent of CT scanning and MRI, the case-fatality rate has decreased by 90%.

Other Tests

  • ECG occasionally reveals a focus of high voltage with slow activity. It is nonspecific and rarely of value in confirming the diagnosis. This is the least accurate procedure in the diagnostic evaluation.

Procedures

  • Biopsy of cerebral lesion
    • Hyphae and type of branching can assist in ion diagnosis of specific fungal infections.
    • In patients with toxoplasmosis, special immunochemical tests can be used to detect the organism or its antigens. A brain-touch technique using immunofluorescence monoclonal antibodies against the organism can also provide rapid diagnosis.

More on Brain Abscess

Overview: Brain Abscess
Differential Diagnoses & Workup: Brain Abscess
Treatment & Medication: Brain Abscess
Follow-up: Brain Abscess
Multimedia: Brain Abscess
References
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References

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Further Reading

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Keywords

brain abscess, abscess of the brain, brain disease, intra-cranial abscess, intracranial abscess, subdural empyema, extradural empyema, intracranial inflammation, intra-cranial inflammation, Staphylococcus aureus, S aureus, Streptococcus intermedius, S intermedius, Bacteroides, Prevotella, Pseudomonas, pseudomonal organisms, streptococci, anaerobic bacilli, anaerobic infection, Enterobacteriaceae

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Contributor Information and Disclosures

Author

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 Federation for Clinical Research, American Medical Association, American Society for Microbiology, Armed Forces Infectious Diseases Society, 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 Ear, Nose and Throat Advances in Children, Society for Experimental Biology and Medicine, Society for Pediatric Research, Southern Medical Association, and Surgical Infection Society
Disclosure: Nothing to disclose.

Medical Editor

Jeffrey D Band, MD, Clinical Professor of Medicine, Wayne State University School of Medicine; Director, Division of Infectious Diseases and International Medicine, William Beaumont Hospital Corporation
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.

Managing Editor

Ronald A Greenfield, MD, Professor, Department of Internal Medicine, Section of Infectious Diseases, University of Oklahoma College of Medicine
Ronald A Greenfield, MD is a member of the following medical societies: American College of Physicians, American Federation for Medical Research, American Society for Microbiology, Central Society for Clinical Research, Infectious Diseases Society of America, Medical Mycology Society of the Americas, Phi Beta Kappa, Southern Society for Clinical Investigation, and Southwestern Association of Clinical Microbiology
Disclosure: Pfizer Honoraria Speaking and teaching; Gilead Honoraria Speaking and teaching; Ortho McNeil Honoraria Speaking and teaching; Wyeth Honoraria Speaking and teaching; Abbott Honoraria Speaking and teaching; Astellas Honoraria Speaking and teaching; Cubicin  Speaking and teaching

CME Editor

Eleftherios Mylonakis, MD, Clinical and Research Fellow, Department of Internal Medicine, Division of Infectious Diseases, Massachusetts General Hospital
Eleftherios Mylonakis, MD is a member of the following medical societies: American Association for the Advancement of Science, American College of Physicians, American Society for Microbiology, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

Chief Editor

Burke A Cunha, MD, Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital
Burke A Cunha, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

 
 
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