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Blastomycosis

Last Updated: June 30, 2021

Open Table of Contents: Blastomycosis

Figure 1: These images demonstrate a fairly classic appearance of parenchymal blastomycosis. There is a large, cystic lesion with smooth rim enhancement demonstrated before and after contrast (Top Row), normal diffusivity in the cavity on DWI/ADC (Middle Row), and a mild amount of surrounding vasogenic edema on T2/FLAIR imaging (Bottom Row). More commonly, these patients will present with meningitis (not presented here).

Figure 1: These images demonstrate a fairly classic appearance of parenchymal blastomycosis. There is a large, cystic lesion with smooth rim enhancement demonstrated before and after contrast (Top Row), normal diffusivity in the cavity on DWI/ADC (Middle Row), and a mild amount of surrounding vasogenic edema on T2/FLAIR imaging (Bottom Row). More commonly, these patients will present with meningitis (not presented here).

Description

  • Caused by the dimorphic fungus Blastomyces dermatitidis
  • Endemic to Ohio and the Mississippi River valley
  • Lung infection with hematogenous spread to the CNS in 5% to 10% of cases of disseminated infection

Pathology

  • Exists as a mold in the environment and a yeast at body temperatures

Clinical Features

  • Symptoms
    • Nonspecific
    • Headache, altered mental status, fever, vision changes, and seizures
  • Age
    • Highly variable
  • Gender
    • No gender predilection
  • Median survival
    • Depends on how early in the disease process management is started and whether the patient is immunocompromised

Imaging

  • General
    • Pachymeningeal (dura mater) enhancement and often lobulated enhancing mass lesions in the brain parenchyma
    • Most common manifestation is epidural or parenchymal abscess, with meningitis being the most common presentation
  • Modality specific
    • CT
      • Ill-defined areas or hypoattenuation
    • MRI
      • T1WI
        • Hypointense or isointense
      • T2WI
        • Hyperintense
      • DWI
        • Typically normal diffusivity but can demonstrate central restriction
      • Contrast
        • Peripheral ring-like enhancement
        • Pachymeningeal enhancement
  • Imaging recommendations
    • Standard protocol MRI (including DWI) with intravenous contrast
  • Mimic
    • Can mimic any of the ring-enhancing lesions and can present as a nonspecific meningitis; clinical history with travel to an area of endemicity can help narrow the differential diagnosis

Contributor: Sean Dodson, MD

DOI: https://doi.org/10.18791/nsatlas.v1.03.02.06

References

Bariola JR, Perry P, Pappas PG, et al. Blastomycosis of the central nervous system: a multicenter review of diagnosis and treatment in the modern era. Clin Infect Dis 2010;50:797–804. doi.org/10.1086/650579

Fang W, Washington L, Kumar N. Imaging manifestations of blastomycosis: a pulmonary infection with potential dissemination. Radiographics 2007;27:641–655. doi.org/10.1148/rg.273065122

Rabelo NN, Silveira Filho LJ, da Silva BNB, et al. Differential diagnosis between neoplastic and non-neoplastic brain lesions in radiology. Arq Bras Neurocir 2016;35:45–61. doi.org/10.1055/s-0035-1570362

Starkey J, Moritani T, Kirby P. MRI of CNS fungal infections: review of aspergillosis to histoplasmosis and everything in between. Clin Neuroradiol 2014;24:217–230. doi.org/10.1007/s00062-014-0305-7

Stavraki C, Narayan A, Voronel O. Cerebral blastomycosis: radiologic-pathologic correlation of solitary CNS blastomycosis mass-like infection. J Clin Imaging Sci 2015;5:30. doi.org/10.4103/2156-7514.157854

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