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Aspergillosis

Last Updated: October 1, 2018

Open Table of Contents: Aspergillosis

Figure 1: In this patient, there are multiple, randomly distributed lesions scattered throughout bilateral cerebral hemispheres. The lesions demonstrate a ring pattern, or rim of peripheral restricted diffusion and central hypointense DWI signal (top row). The rim pattern of signal abnormality carries through on all sequences (middle row). On the SWI image (bottom row left), there is central hypointense signal which often corresponds to a combination of hemorrhage and fungal elements. As in most patients with aspergillosis, there is little to no peripheral enhancement (bottom row right).

Description

  • Saprophytic opportunistic infection

Pathology

  • Infection typically caused by Aspergillus fumigatus
  • Septate, branching hyphae that show dichotomous branching and irregular, non-parallel cell walls
  • Typically spreads hematogenously from the lungs
  • Produce elastase which leads to angioinvasion, microhemorrhage. Mycotic aneurysm formation common, with resulting subarachnoid hemorrhage
  • Fungal elements can also fill vessels, leading to occlusive thrombosis, embolism and infarction

Clinical Features

  • Symptoms
    • AMS, weakness, and seizures
  • Population

    • No age or gender predilection
    • Underlying pulmonary illnesses are common
  • Prognosis

    • Poor, with mortality rates near 100%

Imaging

  • General
    • Multiple lesions with infarction or hemorrhage in a random distribution
    • Predilection for perforating arteries - basal ganglia, thalamus and corpus callosum
      • Infarction of the corpus callosum is rare but suggests aspergillosis infection because thromboembolism and pyogenic abscesses are uncommon in this location
    • Meningitis and ventriculitis are common findings though often radiographically occult
  • CT

    • Not very specific
    • Ill-defined hypodense regions with variable mass effect and vasogenic edema
  • MR

    • T1WI
      • Ill-defined hypointense foci
    • T2WI

      • Intermediate to low peripheral signal with central hyperintensity
    • DWI

      • Ring pattern - often hypointense centrally with peripheral diffusion restriction
    • SWI

      • Hypointense signal corresponding to focal hemorrhage and fungal elements
      • Hemorrhage seen in 25% of patients
    • Contrast

      • None to weak peripheral
  • Imaging Recommendations

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

    • Given the wide variation in presentation (focal ring enhancing lesion, meningeal involvement, infarctions and hemorrhage), aspergillosis can be extremely difficult to accurately diagnose without the appropriate history. Knowing the patient’s immune status can help narrow the differential substantially.

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

Contributor: Sean Dodson, MD

DOI: https://doi.org/10.18791/nsatlas.v1.03.02.03

References

Almutairi BM, et al. Invasive Aspergillosis of the Brain: Radiologic-Pathologic Correlation. Radiographics. 2009; 29(2):375-79.

DeLone DR, et al. Disseminated Aspergillosis Involving the Brain: Distribution and Imaging Characteristics. AJNR. 1999; 20:1597-1604.

Miszkiel KA, et al. The spectrum of MRI findings in CNS Cryptococcosis in AIDS. Clin Radiol. 1996; 51(12):842-50.

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.

Tempkin AD, et al. Cerebral Aspergillosis: Radiologic and Pathologic Findings. Radiographics. 2006; 26(4):1239-42.

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