Teaching NeuroImage: Cryptococcal brain pseudocysts in an immunocompetent patient

A 52-year-old man developed fever, meningismus, and decreasing level of consciousness over 2 days. On arrival he was minimally responsive to external stimuli and was profoundly rigid. There was no history of immunosuppression; however, he worked as a vacuum truck operator and reported exposure to chicken and pigeon feces in the weeks prior to his illness. CSF opening pressure was >30 cm of H₂O with a mild lymphocytic pleocytosis (239 × 10*6 cells/L) with protein at the upper limit of normal (0.45 mmol/L), and normal glucose (4.1 mmol/L). HIV serology was negative. ELISA and India ink stain were positive for cryptococcus. CSF cultures identified Cryptococcus neoformans var Gatti as the pathogenic species. Other infectious causes, including hepatitis B and C viruses, herpes simplex virus, mycobacterium tuberculosis, and other fungal sources, were all excluded. Brain MRI showed bilateral pseudocysts predominantly involving the basal ganglia, and post-gadolinium sequences showed little enhancement of the cysts or surrounding parenchyma (figure). The patient received IV amphotericin B and flucytosine for 3 weeks followed by maintenance therapy with fluconazole. A lumbar CSF drain was inserted to treat raised intracranial pressure. Serial chest x-rays performed to monitor for pulmonary disease or complications showed no evidence of cryptococcal pulmonary infection. At the time of discharge, the patient had only mild residual bilateral bradykinesia and rigidity.

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Figure CNS cryptococcosis: brain MRI findings

(A) Axial T2 sequence showing bilateral pseudocysts as hyperintensities (arrowheads) predominantly involving the basal ganglia. The pseudocysts are thick walled and septated with a proteinaceous content depicted by their relative hyperintensity compared to CSF. (B) Post-gadolinium MRI sequences showing little to no enhancement of the cysts or surrounding parenchyma.

This case highlights the potentially dramatic imaging appearance of cryptococcal meningoencephalitis. Post-gadolinium MRI sequences showed little to no enhancement of the cysts or surrounding parenchyma, a feature that differentiates this disorder from other inflammatory or malignant processes, which are usually associated with breakdown of local blood–brain barrier and uptake of gadolinium.^1–3 The case further demonstrates that early and aggressive management of severe cryptococcal meningoencephalitis can lead to a favorable outcome.