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).
- 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
- Exists as a mold in the environment and a yeast at body temperatures
- Headache, AMS, fever, vision changes and seizures
- Median survival
- Depends on how early in the disease process management is started and whether or not the patient is immunocompromised
- 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
- Ill-defined areas or hypoattenuation
- Typically normal diffusivity but may demonstrate central restriction
- Peripheral ring-like enhancement
- Pachymeningeal enhancement
- Imaging Recommendations
- Standard protocol MR (including DWI) with intravenous contrast
- 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
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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