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Neuroradiology

E3027. Review of CNS Mycosis: Imaging Patterns, Clinical Syndromes and

Blanchard A,  Sawyer D,  Palacios E. Tulane University School of Medicine Department of Radiology, New Orleans, United States

Address correspondence to A. Blanchard (ablanch1@tulane.edu)

Background Information: CNS fungal infection is an uncommon but dangerous disease process that can be successfully treated given prompt diagnosis. Imaging plays a crucial role in the detection of infection, and can suggest the species of organism involved. Diagnosis of CNS mycosis can be challenging as fungal infections can mimic many other pathologies.

Educational Goals/Teaching Points: The goal of the exhibit is to familiarize the audience with common and uncommon radiologic presentations of CNS fungal infection. Radiologic-pathologic correlation are presented to explain the patterns of disease. An overview of the clinical syndromes and epidemiologic data of CNS mycoses are included as they are invaluable in constructing a germane differential diagnosis.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques: Fungal infection of the CNS can occur via multiple mechanisms, many of which are particular to a specific species. These findings can be correlated through imaging. Hematogenous spread is common, although the size of the particular organism determines its likely site of dissemination [1, 2]. Larger organisms tend to localize intraaxially, typically resulting in cerebritis or abscess, while invasion by smaller organisms manifests as extraaxial or disseminated disease. Aspergillus and Cryptococcus species are capable of seeding the CNS from the CSF, resulting in a variety of patterns of infection. A limited number of species invade the CNS secondarily through sinonasal infection. Vasculopathy also occurs, and can present as vasculitis, mycotic aneurysms, or septic embolic disease. MRI of the CNS is the preferred technique for evaluating fungal disease given its superior soft tissue contrast resolution. There is a wide range of nonspecific findings that are suggestive of fungal infection. Common features on MRI include diffusion restriction, which may be present at early stages, and diminished ring enhancement, which is seen in fungal infections due to an inadequate host immune response [3]. MR spectroscopy can also be useful in differentiating fungal from pyogenic abscesses [2].

Conclusion: The radiologic manifestations of CNS mycoses are determined by the pathogenesis of infection and organism virulence factors. The ability to recognize the findings suggestive of fungal infiltration is critical to ensuring prompt diagnosis and subsequent treatment. References: 1. Starkey J et al. MRI of CNS fungal infections: review of aspergillosis to histoplasmosis and everything in between. Clin Neuroradiol 2014; 24:217–230 2. Palacios E et al. Magnetic resonance imaging in fungal infections of the brain. Top Magn Reson Imaging 2014; 23:199–212 3. Mathur M et al. Fungal infections of the central nervous system. Neuroimaging Clin N Am 2012; 22:609–632