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).

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

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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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