Fungal central nervous system infections: prevalence and diagnosis

Abstract

Fungal infections of the central nervous system (CNS) are rare but they pose a significant challenge. Their prevalence spans a wide array of hosts including immunosuppressed and immunocompetent individuals, patients undergoing neurosurgical procedures and those carrying implantable CNS devices. Cryptococcus neoformans and Aspergillus spp. remain the most common pathogens. Magnetic resonance imaging can help localize the lesions, but diagnosis is challenging since invasive procedures may be needed for the retrieval of tissue, especially in cases of fungal abscesses. Antigen and antibody tests are available and approved for use in the cerebrospinal fluid (CSF). PCR-based techniques are promising but they are not validated for use in the CSF. This review provides an overview on the differential diagnosis of the fungal CNS disease based on the host and the clinical syndrome and suggests the optimal use of diagnostic techniques. It also summarizes the emergence of Cryptococcus gatti and an unanticipated outbreak caused by Exserohilum rostratum.

Keywords::

• abscess
• cerebral
• fungal
• meningitis
• molds
• yeasts

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending or royalties.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Different patient groups have different susceptibility to specific fungi and understanding the different risk groups can assist in the differential diagnosis of cerebral mycoses.

• Knowledge of the local epidemiology and endemic nature of certain pathogens is important for diagnosis.

• New fungal pathogens cause human disease through a breach in the body's normal barriers, while the epidemiology of older fungal pathogens is also evolving.

• Antigen and antibody assays in the CSF are useful in diagnosing certain mycoses even when these include the brain parenchyma. Cryptococcal antigen CSF assay remains a traditional diagnostic tool. Histoplasma antigen and antibodies testing in the CSF have been well validated for diagnosis. Antibody detection is diagnostic for coccidioidal and paracoccidioidal disease.

• Molecular techniques are not validated for use in CSF samples in suspected cerebral mycoses.

• Imaging findings for cerebral mycoses are non-specific but newer techniques, such as diffusion-weighted imaging, magnetic resonance perfusion and magnetic resonance spectroscopy are helpful tools in the differential diagnosis of bacterial infections or tumors.