Figure 1: In this HIV positive patient, there is a cluster of dilated perivascular spaces and pseudocysts with signal isointense to CSF on T1 (top row left), T2 (top row right) and FLAIR (middle row left). The medial most lesion demonstrated more heterogeneous signal with a solid enhancing component (middle row right) along the medial margin. The majority of these lesions in the basal ganglia demonstrate normal or increased diffusivity on DWI/ADC (bottom row), a common finding in many atypical infections.
- Opportunistic fungal infection (Cryptococcus neoformans)
- Strongest risk factor is T-cell dysfunction, thus most commonly seen in patients with HIV/AIDS
- Encapsulated, yeast-like fungus that is found in animal droppings
- Infection in the lung spreads through the perivascular spaces into the deep gray nuclei, midbrain, and cerebellum
- Signs and Symptoms
- Headache is most common
- Seizure, blurred vision, focal deficits
- Mortality rates approach 100% in the untreated population. This improves significantly with treatment to 15-30%.
- General features
- Most common finding is a non-specific meningitis
- A more specific finding is usually small gelatinous pseudocysts in the deep gray nuclei, cerebellum and white matter along the perivascular spaces
- Cryptococcoma may simulate a tumor in the cerebral or cerebellar parenchyma or brainstem
- Modality specific
- Dilated perivascular spaces and pseudocysts isointense to CSF
- Cryptococcoma: hypointense
- Dilated perivascular space isointense to CSF
- Pseudocysts will have hypointense ring surrounding a hyperintense center
- Cryptococcoma: hyperintense
- If immunocompetent may demonstrate low level enhancement
- Cryptococcoma demonstrate solid or rim enhancement
- Gelatinous pseudocyst
- T1 hypo, T2 hypointense ring surrounding a hyperintense center
- Imaging Recommendations
- Standard protocol MR (including DWI) with intravenous contrast
- Can be difficult to distinguish between tuberculous and toxoplasma infections, but in an AIDS patient with dilated perivascular spaces this should be at the top of your differential diagnosis. When in the form of a cryptococcoma, will mimic all other ring enhancing lesions.
For more information, please see the corresponding chapter in Radiopaedia, and the Cryptococcosis chapter within the Cerebral Infectious Diseases sub-volume in the Neurosurgical Atlas.
Contributor: Sean Dodson, MD
Gottumukkaa RV, et al. Imaging of the brain in the patients with human immunodeficiency virus infection. Top Magn Reson Imaging. 2014; 23(5)275-91.
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.
Thurnher MM, et al. Neuroimaging in the brain in HIV-1-infected patients. Neuroimaging Clin N Am. 2008; 18(1):93-117.
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