Mucormycosis is caused by fungi that include Mucor, Rhizopus, and Absidia species. It is seen in diabetic and immunocompromised patients.
Fungal spores germinate to form angioinvasive hyphae that cause infarction of the surrounding tissue and invade the nasal mucosa.
The invaded tissue is non-enhancing on contrast-enhanced MRI and may show diffusion restriction. Non-infarcted sinusitis shows T1 post-contrast enhancement of the mucosa.
This sign is important for the early detection of mucormycosis so treatment may be initiated to reduce the chance of blindness and death which may occur within 2 weeks if left untreated.