The Frozen Brain State of Cryptococcus gattii: A Globe-Trotting, Tropical, Neurotropic Fungus

Initially reported in tropical regions, Cryptococcus gattii infection is now diagnosed globally. Methods: case report; Literature review. Although initial reports described outbreaks of pulmonary and central nervous system (CNS) disease in tropical regions such as Australia and New Guinea, it is now clear that Cryptococcus gattii is a global, neurotropic pathogen. In contrast with C. neoformans, C. gattii patients are more likely to present with cryptococcomas in the brain and lungs and are often HIV negative. Imaging findings can mimick cancer leading to delays in diagnosis and definitive treatment. Some experts have speculated that the spread of C. gattii is due to climate change, newly recognized genotypes that cause disease in temperate zones (genotype VGII), international travel, and improved awareness among physicians and veterinarians. We emphasize neurocritical and neurosurgical management, because patients with CNS involvement often have high intracranial pressures (ICP). Cryptococcus gattii patients often have elevated ICP without 'red flag' radiographic signs of elevated ICP such as ventriculomegaly, cerebral edema, or effaced basal cisterns. Therefore, diagnosis of high ICP should be suspected based on clinical symptoms such as incapacitating headaches, progressive visual loss and associated papilledema, and then confirmed by measuring the opening pressure with lumbar puncture (LP). Cerebral intraparenchymal deposition of the large cryptococcal polysaccharide capsule and cryptococcal organisms causes poor brain compliance leading to a 'frozen brain state.' Mortality rates and clinical outcomes are significantly improved with early diagnosis, antifungal therapies, steroids, and aggressive management of elevated ICP including cerebrospinal fluid (CSF) diversion by serial LP's, external ventricular drains and CSF shunts. Following institution of antifungal therapy, about 10% of patients can worsen due to immune reconstitution inflammatory syndrome which responds to steroids. We recommend neurocritical and neurosurgical management of C. gattii patients with CNS involvement and elevated ICP. There is often poor correlation between elevated ICP and neuroimaging due to the frozen brain state.