COVID-Associated Sinonasal Mucormycosis: Radiological Pathological Correlation and Prognostic Value of MR Imaging

Abstract

Purpose Our aim was to assess the sinonasal magnetic resonance imaging (MRI) features of acute invasive fungal rhinosinusitis (AIFRS) in coronavirus disease (COVID)-associated mucormycosis (CAM) and to correlate these with histopathology and patient outcome in terms of duration of hospital stay and survival at 10 weeks. Methods Twenty patients with histopathologically confirmed sinonasal CAM underwent MRI (including postcontrast T1-weighted and diffusion-weighted imaging). Histopathological findings (presence of coagulative necrosis, granulomatous reaction, and fungal burden) were recorded and all patients were followed up at 6 and 10 weeks. Statistical analysis was done using chi-square test and Fischer's exact test. Results Enhancement patterns seen in our subjects included homogeneous, heterogeneous, and lack of contrast enhancement (LOC), with LOC being the most common (65%). Diffusion restriction was found in 90% patients. Statistically significant correlation was found between LOC pattern and presence of coagulative necrosis ( p -value = 0.007), extent of fungal hyphae ( p -value = 0.047), and duration of hospital stay ( p -value = 0.004). Restricted diffusion was also seen to correlate with a high fungal load ( p -value = 0.007). Conclusion Our study describes the MRI findings of AIFRS in CAM and highlights the imaging features which may be surrogate markers for coagulative necrosis and fungal burden.

Keywords: MRI; coagulative necrosis; diffusion restriction; fungal load; lack of contrast enhancement.

Fig. 1

Magnetic resonance (MR) enhancement patterns in coronavirus disease (COVID)-associated mucormycosis (CAM).

Fig. 2

Coagulative necrosis in lack of contrast enhancement (LOC) and non-LOC lesions.

Fig. 3

( A – E ) Lack of contrast enhancement. Axial contrast-enhanced fat-saturated T1-weighted image ( A ) shows lack of contrast enhancement (LOC) in the soft tissue involving the left nasolacrimal region and anterior ethmoid air cells (white arrow) with preserved in-between bone (black arrow). The area of LOC shows predominantly hyperintense signal on T2-weighted image (white arrowhead in B ) and restricted diffusion on axial diffusion-weighted image (DWI) (double-headed arrow in C ), and corresponding apparent diffusion coefficient (ADC) map (curved arrow in D ). Histology shows coagulative necrotic background and broad aseptate hyphae with right angle branching of Mucor (black arrow in E ). Small fragments of hyphae (black arrow heads) are also seen (hematoxylin and eosin ×600).

Fig. 4

( A – E ) Homogeneous enhancement pattern. Axial contrast-enhanced fat-saturated T1-weighted image ( A ) shows homogeneous enhancement in the right sphenoid sinus (black arrow) and right cavernous sinus (black arrowhead). Left cavernous sinus is also bulky (white curved arrow). Isointense signal is seen in this region on T2-weighted image (white arrow and white arrowhead in B ) with restricted diffusion on axial diffusion-weighted image (DWI) image (white arrows in C ) and corresponding apparent diffusion coefficient (ADC) map (black arrows in D ). Bilateral internal carotid artery (ICA) flow voids are maintained (* in B ). Histology shows long ribbon-like septate hyphae with right angle branching (black arrowheads in E ) (+3 fungal load) in the background of acute inflammatory reaction (hematoxylin and eosin ×400).

Fig. 5

( A – E ) Heterogeneous enhancement pattern. Axial contrast-enhanced fat-saturated T1-weighted image ( A ) shows heterogeneous enhancement in the right maxillary sinus (white arrow) which shows predominantly hyperintense signal on T2-weighted image (white arrowhead in B ). The region does not depict any focus of restricted diffusion on corresponding diffusion-weighted image (DWI) ( C ) and apparent diffusion coefficient (ADC) map ( D ). Histology depicts epithelioid cell granuloma (black arrowhead) admixed with multinucleate giant cells and few fungal hyphae (+1 fungal load) (hematoxylin and eosin ×400).