Cryptococcosis of the Brain
The Common Vein Copyright 2010
Definition
Cryptococcosis is an infection caused by Cryptococcus neoformans, an encapsulated budding yeast that is present worldwide in soil and dried pigeon droppings.
Infection occurs mainly in patients with impaired cell-mediated immunity. It is the most common, systemic, fungal infection in patients infected with HIV, and is also seen as a complication of lymphoma, corticosteroid therapy and immunosuppression following solid organ transplantation. Infections are initially acquired by inhalation; in the lung, the infection may remain localized, heal, or disseminate.
In the CNS, structurally, this infection can cause meningitis, mass deposits (cryptococcomas) that are a collection of consisting of these organisms with inflammatory cells and mucoid material. Dilated perivascular spaces can also develop when the Cryptococcus invades the parenchyma.
Clinically, patients will have symptoms of subacute / chronic meningitis: headache and fever are usually the first symptoms, which is later followed by changes in mental status changes, nausea, and vomiting and cranial nerve abnormalities.
Diagnosis is made by CSF culture, with positive staining of the organism with India Ink, and with serologic markers / positive cultures.
CT can be normal in almost half of the scans, since meningeal involvement is mild in most cases. Mass lesions (cryptococcomas) are seen in about 10% of cases, and are small, multiple, solid, enhancing peripheral parenchymal nodules, being hypo or isodense. MRI can also demonstrate the dilated perivascular spaces at times, which appear as hyperintense oval lesions in T2, smaller than 3 mm, but that are not specific, since they can appear in brain atrophy as well.
Patients are treated with fluconazole therapy, or amphotericin B for higher risk patients.