Cryptococcal leptomeningitis with basal ganglia involvement
The patient has a history of HIV/AIDS, with previous cryptococcal meningitis, presenting with a lowered level of consciousness and headache. CSF screening positive for cryptococcus.
In patients with severe immunosuppression, infection of the meninges diffuses into the cerebral parenchyma through the ependymal and subarachnoid spaces. This leads to the accumulation of fungus-rich mucinous exudates, expressed by dilation of the perivascular (Virchow-Robin) spaces. Such exudates can further evolve into mucinous cysts, with a predilection for the basal ganglia and periventricular regions.
In this case, there is a lesion in the basal ganglia that does not show contrast enhancement. There is, however, leptomeningeal enhancement, which is characteristic of cryptococcal leptomeningitis.