Cryptococcus neoformans is an encapsulated yeast found in temperate regions and present in soil with avian droppings. Its reservoir in nature has never been established clearly. Cryptococcal infection occurs by inhalation of fungal spores and disseminates via the blood stream. It rarely spreads by local extension to CNS. After exposure, extent of disease depends upon the host immunity. In immunocompetent patients, the disease is usually restricted to the lung. When the immune system fails, it may involve any organ like brain, meninges, skin, eyes and skeletal system. Cryptococcosis is rare in children. In adults it is predominantly seen in HIV infected individuals and rarely in non-HIV patients.

Cryptococci grows as foci in the brain but with minimal or no inflammatory response so that cystic clusters of fungi expand and displace the brain tissue without directly destroying it. Thus, patients usually present with headache, nausea, dizziness, low grade fever. With progression of the disease, it may involve the basilar meninges and brain substance itself leading to brain swelling and compression of cranial nerves which may be fatal. This chronic granulomatous meningitis may lead to impairment of CSF flow and cause hydrocephalus with raised intracranial pressure and deterioration and even dementia. Patients would then present with impairment of hearing, personality changes, papilledema, nuchal rigidity and raised ICT. In patients with AIDS, cryptococcal meningitis may develop with minimal or no signs referable to the CNS.