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Coccidioidomycosis

Last Updated: October 1, 2018

Open Table of Contents: Coccidioidomycosis

Figure 1: A peripherally enhancing lesion along the ventral pons (top row left, top row right) demonstrates central restricted diffusion on DWI (bottom row left) and ADC (bottom row right), a finding more typically seen in infectious abscess than in tumor. When along the surface of the brain as in this case, coccidioidomycosis may mimic leptomeningeal carcinomatosis.

Figure 2: Axial (top row left, top row right) and coronal (bottom row left) contrast-enhanced T1 images demonstrate numerous tiny enhancing nodules along the basal cisterns and within and along the cerebellum reflecting the leptomeningeal disease and occasional parenchymal abscesses that are common with coccidiomycosis and can mimic small metastases. Axial FLAIR image (bottom row right) also shows the hyperintense local edema associated with small parenchymal cerebellar abscesses.

Figure 3: Axial T1 postcontrast images demonstrate prepontine cistern and medial left temporal enhancing coccidiomycosis involvement (top row left) and enhancing infectious tissue along the medial anterior left lobe, in the right posterior orbital gyrus and in the left basal ganglia (top row right) that can also be seen in dural-based and parenchymal metastatic disease. The parenchymal lesions also demonstrate nonspecific surrounding FLAIR hyperintense edema (bottom row left, bottom row right) that would also be typical of parenchymal metastatic disease.

Description

  • Coccidioides immitis is a dimorphic fungus endemic to the southwestern US and regions of Mexico and Central and South America
  • Primary infection occurs in the lungs after inhalation of airborne arthrospores
  • Up to 5% of patients develop disseminated disease with CNS involvement being the most frequent and severe manifestation

Pathology

  • Mycelial form known to grow in the soil and produces spores that become airborne with disturbance of the soil
  • Inhalation of the spores leads to pulmonary infection

Clinical Features

  • Signs and Symptoms
    • Headache, nausea, vomiting, and altered mental status with concurrent pulmonary symptoms, septic shock and fungemia
  • Age and Gender

    • No age or gender predilection
  • Prognosis

    • Mean survival time
      • Without treatment – 4 months
      • With treatment (amphotericin B) – 21 months

Imaging

  • General features
    • Most common presentation is meningitis with a propensity for the basal cisterns
    • Hydrocephalus, infarctions, vasculitis, parenchymal or parameningeal masses and abscesses, periventricular white matter abnormalities and spinal arachnoiditis
    • Important to perform spinal imaging because spinal involvement is common and may lead to change in management
  • Modality specific    

    • CT
      • Ill-defined areas of hypoattenuation with intermixed hemorrhage
      • Hydrocephalus, herniation
    • MR

      • T1WI
        • Ill-defined hypointense regions
      • T2WI

        • Ill-defined hyperintense regions with possible hypointense rim
      • DWI

        • Restriction along the wall of the abscess
      • SWI

        • Hypointense signal in the setting of hemorrhage
      • Contrast

        • Meningeal enhancement in the setting of meningitis
        • If cerebral parenchymal involvement, there will be variable enhancement
  • Imaging Recommendations

    • Standard protocol MR (including DWI) with intravenous contrast
  • Mimic

    • Similar to other infectious processes, when walled off will be difficult to distinguish from other ring enhancing lesions. However, when presented with basilar cistern involvement, coccidioidomycosis should be included in your differential with tuberculosis and other granulomatous processes such as sarcoidosis.

For more information, please see the corresponding chapter in Radiopaedia.

Contributor: Sean Dodson, MD

DOI: https://doi.org/10.18791/nsatlas.v1.03.02.11

References

Gupta NA, et al. Imaging Manifestations of Primary and Disseminated Coccidioidomycosis. Applied Radiology. Feb 2015; 9-21.

Lammering JC, et al. Imaging Spectrum of CNS Coccidioidomycosis: Prevalence and Significance of Concurrent Brain and Spinal Disease. AJR. 2013; 200:1334-46.

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.

Wrobel CJ, et al. MR Findings in Acute and Chronic Coccidioidomycosis Meningitis. AJNR. 1992; 13:1241-45.

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