MR Imaging in Covid-19–Associated Invasive Fungal Sinusitis

We witnessed a sharp peak in the incidence of invasive fungal sinusitis, particularly mucormycosis, in patients with history of coronavirus disease 2019 (COVID-19) infection in India. Rhino-orbito-cerebral mucormycosis (ROCM) is a fulminant rapidly progressive disease. Early diagnosis significantly improves patient survival and outcomes. Hence, neuroimaging plays a very important role. We studied the magnetic resonance (MR) imaging manifestations of invasive fungal sinusitis and established an imaging protocol, which helps in early diagnosis of the disease per se as well as its complications. We evaluated the differences between COVID-19-associated and non-COVID-19-associated ROCM. We retrospectively analyzed the MR imaging manifestations of 91 histopathologically proven cases of post-COVID-19-invasive fungal sinusitis. We observed stage I disease limited to sinuses in 25.2%, stage II disease with intraorbital spread in 23%, and stage III disease with intracranial spread in 51.6% of our patients. Dural involvement was the commonest and earliest sign of stage III disease. Direct parenchymal invasion from the adjacent paranasal sinuses was the commonest pattern of cerebral involvement, involving basifrontal lobe (14.2%) followed by anteromedial temporal lobe (5.4%). We observed orbital and intracranial complications including subperiosteal orbital abscess (1%), cavernous sinus involvement (29.6%), angioinvasion (15.3%), perineural spread (9.8%), and osteomyelitis of skull base and craniofacial bones (45%). Contrary to non-COVID-19-associated ROCM, we did not observe any case with superior ophthalmic vein/dural venous sinus thrombosis or basilar artery angioinvasion in our study. In our study, stage III disease was most commonly due to direct parenchymal invasion into frontal and temporal lobes from the adjacent frontal and sphenoid sinuses, respectively. The commonest vascular complications in our study were cavernous sinus involvement followed by angioinvasion into the cavernous ICA leading to watershed infarcts.