CNS mucormycosis

The Reversed
Halo Sign in Pulmonary Mucormycosis with cerebral dissemination in immunocompromised host.. +6 days HCT. Axial non-enhanced brain CT scan shows corticosubcortical hypoattenuation in the right frontal lobe which suggests a septic embolism, with a lineal hyperdensity that could indicate a minimal petechial haemorrhage (arrow).
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The Reversed
Halo Sign in Pulmonary Mucormycosis with cerebral dissemination in immunocompromised host.. +22 days HCT. Axial enhanced brain CT scan shows a brain abscess with enhanced peripheral rim and vasogenic oedema associated, which is causing mass effect and shift of midline structures.
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Radiopaedia • CC-by-nc-sa 3.0 • de

Rhinocerebral mucormycosis refers to an uncommon form of invasive fungal sinus infection.

Clinical presentation

The presentation can vary, ranging from exophthalmos, rhinorrhea, and ophthalmoplegia with loss of visual acuity and peripheral facial palsies occurring rarely .

Pathology

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, Rhizopus, and Absidia spp. The fungi themselves are ubiquitous, subsisting on decaying vegetation and diverse organic material . 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.

Risk groups
  • diabetics: especially those with poor control
  • immunocompromised states

Radiographic features

General

Can show varying degree of sinus opacification with most having a tumefactive nature. 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.

MRI

Reported signal characteristics on MRI of the sinuses and brain include:

  • T1: isointense lesions relative to brain in most cases (~80%)
  • T2:
    • variable with around 20% of patients showing high T2 signal
    • 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 

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 .  Complications associated with wider intracranial extension can be potentially fatal .

Complications
  • invasion:
    • orbital spread
    • intracranial extension
  • vascular thrombosis (from extension): including the cavernous sinus thrombosis 
  • subsequent infarction

See also

Siehe auch:
Assoziationen und Differentialdiagnosen zu Mukormykose des ZNS:
Pulmonary
mucormycosis
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