Brain abscess

Last reviewed: 5 Jan 2023
Last updated: 26 Jan 2021



History and exam

Key diagnostic factors

  • presence of risk factors
  • male sex
  • age <30 years
  • meningismus
  • headache
  • cranial nerve palsy
  • positive Kernig or Brudzinski sign
  • fever
  • increased head circumference (infants)
  • bulging fontanelles (infants)
More key diagnostic factors

Other diagnostic factors

  • neurological deficit
  • papilloedema
Other diagnostic factors

Risk factors

  • sinusitis
  • otitis media
  • dental procedure/infection
  • meningitis
  • recent neurosurgery
  • congenital heart disease
  • endocarditis
  • diverticular disease
  • hereditary haemorrhagic telangiectasia or arteriovenous malformation
  • diabetes mellitus
  • HIV or immunocompromise
  • intravenous drug use
  • chronic granulomatous disease
  • haemodialysis
  • birth prematurity
  • cystic fibrosis
More risk factors

Diagnostic investigations

1st investigations to order

  • FBC
  • serum erythrocyte sedimentation rate (ESR)
  • serum CRP
  • serum PT and PTT
  • blood culture
  • serum toxoplasma titre
  • MRI with contrast
  • CT head with and without contrast
  • ultrasound head (infants)
More 1st investigations to order

Investigations to consider

  • magnetic resonance spectroscopy (MRS)
  • lumbar puncture (LP) with cerebrospinal fluid (CSF) analysis
  • CT chest, abdomen, and pelvis
  • bone scan
  • mammogram
More investigations to consider

Treatment algorithm


presumed brain abscess


suspected or confirmed bacterial aetiology

confirmed fungal aetiology

suspected or confirmed parasitic aetiology

cryptogenic brain abscess



Walter A. Hall, MD, MBA


Department of Neurosurgery

SUNY Upstate Medical University




WAH is an author of a number of references cited in this topic.


Dr Walter A. Hall would like to gratefully acknowledge Dr Peter D. Kim, a previous contributor to this topic. PDK declares that he has no competing interests.

Peer reviewers

Stephen Haines, MD

Professor and Head

Department of Neurosurgery

University of Minnesota




SH and WAH were colleagues on a faculty of the University of Minnesota between 1991 and 1997 and again between 2004 and 2006. They have coauthored articles on neurosurgical infection.

Sabrina Ravaglia, MD, PhD

Staff Physician

Department of Neurological Sciences

Institute of Neurology C. Mondino




SR declares that she has no competing interests.

  • Brain abscess images
  • Differentials

    • Primary central nervous system neoplasm
    • Metastatic lesion
    • Recurrent tumour/radiation necrosis in a post-surgical patient
    More Differentials
  • Guidelines

    • Anaerobic infections (individual fields): central nervous system infections (brain abscess, subdural abscess, epidural abscess and bacterial meningitis)
    More Guidelines
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