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Blastomycosis

Last Updated: October 1, 2018

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 (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 5-10% of cases of disseminated infections

Pathology

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

Clinical Features

  • Symptoms
    • Nonspecific
    • Headache, AMS, 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 or not 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

    • MR

      • T1WI
        • Hypo- or isointense

      • T2WI

        • Hyperintense

      • DWI

        • Typically normal diffusivity but may demonstrate central restriction

      • Contrast

        • Peripheral ring-like enhancement
        • Pachymeningeal enhancement

  • Imaging Recommendations

    • Standard protocol MR (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 endemic areas can help narrow your differential diagnosis.

Contributor: Sean Dodson, MD

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

References

Bariola JR, et al. Blastomycosis of the Central Nervous System: A Multicenter Review of Diagnosis and Treatment in the Modern Era. Clinical Infectious Disease. 2010; 50:797-804.

Fang W, et al. Imaging Manifestations of Blastomycosis: A Pulmonary Infection with Potential Dissemination. Radiographics. 2007; 27:641-55.

Rabelo NN, et al. Differential Diagnosis between Neoplastic and Non-Neoplastic Brain Lesions in Radiology. Arq Bras Neurocir. 2016. Doi: 10.1055/s-0035-1570362.

Starkey J, et al. MRI of CNS Fungal Infections: Review of Aspergillosis to Histoplasmosis and Everything in Between. Clin Neuroradiol. 2014; 24(3):217-30.

Stavraki C, et al. Cerebral Blastomycosis: Radiologic-Pathologic Correlation of Solitary CNS Blastomycosis Mass-Like Infection. J Clin Imaging Sci. 2015; 5:30.

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