Fungal Infections of the Central Nervous System

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CNSfungal infections are rare. Host’s immune system and fungal virulence factors determine the development of these infections. Route of infection may be hematogenous dissemination from a distant focus such as lung, through direct implantation after trauma or secondary to the local extension from sinonasal, orbital, or spinal infections. Anticipation and aggressive diagnostic approach along with timely initiation of antifungal therapy remains the cornerstone in reducing morbidity and mortality.

Fungal meningitis is often caused by yeast organisms. Cerebrospinal Fluid (CSF) analysis remains the diagnostic gold standard. Neuroimaging helps to confirm suspected meningitis and rule out increased intracranial pressure before lumbar puncture. Leptomeningeal enhancement due to a fungal infection may be smooth or thick, nodular and irregular, long and continuous, poorly demarcated or asymmetric, and may extend into the base of the sulci in contrast to the typical thin, symmetric, linear, and discontinuous lepto-meningeal enhancement. Cryptococcus is most frequently identified causative agent, followed by Aspergillus and Candida. They appear as ill-defined intraparenchymal hypodense lesions on CT imaging. On T1Weighted imaging, fungal cerebritis appears as an iso- or hypo-intense area. T2 Weighted images and FLAIR (Fluid Attenuation Inversion Recovery) sequences show a hyper intense lesion. They typically present with restricted diffusion on diffusion weighted images.