Brain abscess

Background
  • Caused by one of three methods:
    • Hematogenous spread (33%)
    • Contiguous infection from middle ear, sinus, teeth (33%)
    • Direct implantation by surgery or penetrating trauma (10%)
  • Microbiology
    • Streptococci in 50% of cases[1]
    • Anaerobes and Gram-negative rods are typical pathogens
    • Staph is involved with direct implantation cases

Clinical Features
  • Patients rarely appear acutely ill
  • Classic triad of headache, fever, AND focal neuro deficit is present in <33%
    • Headache is most common symptom (present in almost all cases)
    • Fever (~50% of patients)
  • Focal neuro symptoms or seizure (~33% of patients)
  • Neck stiffness (<50% of patients)
  • Signs of increased ICP: papilledema, vomiting, confusion, obtundation (50% of patients)

Differential Diagnosis

Intracranial Mass

Altered mental status and fever

Evaluation
Brain abscess on CT (arrows) with left hemiplegia.
Nocardia brain abscess on MRI. (A) T1-WI shows rim-enhancing lesion with associated edema in the right occipital lobe. (B) The dark signal on T2-WI and consistent thickness of the wall suggest a brain abscess.
  • Head CT with contrast
    • Ring enhancing lesion surrounding low-density center surrounded by white matter edema
    • Early in course ring may be less defined; CT may only show area of focal hypodensity
  • Blood cultures
  • Consider additional workup to evaluate for alternate etiologies/complications of underlying disease process

Management

Otogenic source

Sinogenic or odontogenic source

Penetrating trauma or neurosurgical procedures

Hematogenous source

No obvious source

Disposition
  • Neurosurgery consultation

References
  1. Somand D, Meurer W. Central Nervous System Infections. EMCNA 2009; 27: 89-100.
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