27th June 2023

Cryptococcal meningitis

Cryptococcus is a genus of fungi. Cryptococcal infection is caused by either Cryptococcus neoformans or Cryptococcus gattii, with C. neoformans being found in pigeon droppings and is more widespread; it is found in tropical and subtropical areas. Cryptococcal meningitis chiefly affects patients with impaired cell-mediated immunity and, therefore, primarily affects patients with HIV- and a CD4+ T-cell count <100 cells/μL.

Presentations include:

• Head pain
• Neck stiffness
• Altered mental state
• Seizures
• Stroke
• Photophobia
• Nausea and vomiting
• Speech errors
• Focal neurological features
• Skin lesions

Imaging is not always positive in cryptococcal meningitis, however, MRI is more sensitive than CT. Common findings include:

• Leptomeningeal (e.g. pia/arachnoid mater) or dura mater thickening
• Focal parenchymal oedema
• Cryptococcoma
• Pseudocysts
• Dilation of the Virchow-Robin Space (VRS)

Diagnosis usually needs identification of Cryptococcus, involving:

• CSF sampling
  • India ink staining and microscopy
  • Culture
  • Cryptococcal antigen – detected with immunoassay, latex agglutination, or lateral flow assay
  • Beta-D-glucan – may be raised
• Serum
  • Cryptococcal antigen testing has comparable sensitivity to CSF

Management usually includes IV amphotericin V deoxycholate with oral flucytosine, followed by oral fluconazole. HAART should be postponed for around four weeks.