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Sinonasal mucormycosis refers to an uncommon form of invasive fungal sinus infection. Given its highly invasive nature, it can involve orbits and/or intracranial structures.
The presentation can vary, ranging from exophthalmos, rhinorrhea, and ophthalmoplegia with loss of visual acuity and peripheral facial palsies occurring rarely 4.
It originates in the paranasal sinuses and can frequently invade to orbital and cerebral regions. If detected and treated early, involvement can be limited to the nasal cavity and paranasal sinuses.
It is caused by fungi of order Mucorales which can include
- Mucor spp.
- Rhizopus spp.
- Absidia spp.
The fungi themselves are ubiquitous, subsisting on decaying vegetation and diverse organic material 12. Given the opportunity, fungal spores can invade the nasal mucosa (which are often not phagocytised due to poor immune response). They then germinate, forming angioinvasive hyphae that cause infarction of the involved tissue, giving in a “dry” gangrene appearance.
- diabetics: especially those with poor control 1-3
- immunocompromised states
Can show varying degrees of sinus opacification with most having a tumefactive nature 6. They generally demonstrate a rim of soft-tissue thickness along the paranasal sinuses. Complete sinus opacification, gas-fluid levels and obliteration of the nasopharyngeal tissue planes can also occur.
Reported signal characteristics on MRI of the sinuses and brain include:
- T1: isointense lesions relative to the brain in most cases (~80%) 5
- variable with around 20% of patients showing high T2 signal 5
- fungal elements themselves tend to have low signal on T2
- T1 C+ (Gd): the devitalised mucosa appears on contrast-enhanced MR imaging as contiguous foci of non-enhancing tissue, leading to the black turbinate sign 10,14
- DWI: increased signal intensity may be seen 14
Treatment and prognosis
The condition in general carries high morbidity. Management options include reversal of immunosuppression, systemic amphotericin B and surgical debridement in selected cases. Untreated cases can rapidly progress and can be aggressive 7,8. Complications associated with wider intracranial extension can be potentially fatal 9-11.
- vascular thrombosis (from extension): including the cavernous sinus thrombosis 10
- subsequent infarction