CT Imaging Features in Acute Invasive Fungal Rhinosinusitis- Recalling the Oblivion in the COVID Era

Abstract

Objective: Recent pandemic of COVID19 infection has witnessed a re-emergence of invasive fungal sinusitis especially of the Mucor species, which has been a rare entity in the pre covid era. Covid associated mucormycosis (CAM) is one of the dreaded and fatal complications which has surfaced up and early diagnosis is critical for management and survival .It is identified to affect both subset of patients, those with active COVID-19 infection and those who have recovered from the disease in the last 4-6 weeks. Imaging features suggestive of early invasion with supportive imaging examples and relevance of these findings in clinical decision making is presented.

Methods: This paper reviews the various imaging signs of early invasion in CAM A comprehensive checklist for clinically relevant and quick reporting is also presented.

Results: Emphysematous or ulcerative mucosal changes in the nasal cavity is an early imaging feature of CAM. Periantral soft tissue and soft tissue within the pterygopalatine fossa are important imaging signs to indicate extrasinus invasion. Disease within pterygopalatine fossa may lead to multidirectional spread and is an important check site. These findings are seen even in absence of bony erosions owing to the neurovascular spread of disease. Intra orbital and intracranial extensions were found to be fairly common and must be sought for.

Conclusion: The knowledge of early subtle signs of CAM on imaging can aid in prompt diagnosis of this fatal entity in the pertinent clinical setting. Imaging signs of spread of disease and delineation of its extent as inferred from CT imaging aids in prognosis and appropriate surgical management.

FIG. 1

Covid associated mucormycosis in three different patients. Axial bone window CT (a) and coronal soft tissue reformatted images (b,c) depict ulcerated mucosal lining involving vestibule and nasal septum (curved arrows in a), emphysematous nasal cavity mucosal thickening (short straight arrow in b) and necrotic left middle turbinate (notched arrow in c). Contralateral normal enhancing right middle turbinate is noted (long straight arrow).

FIG. 2

Covid associated mucormycosis in a 43 year old male patient 4 weeks after recovery from COVID 19. Axial contrast enhanced CT (a) shows ulcerated nasal septum mucosa (white circle). Ulcerative mucosal changes seen involving the nasopharynx (curved white arrow in b) in another patient with CAM with associated destruction of posterior wall of maxillary sinus as well as retroantral and masticator space involvement (straight white arrow in b).

FIG. 3

Covid associated mucormycosis in two patients with a history of prolonged use of steroids. Contrast-enhanced axial CT images depict different extent of periantral fat involvement. Mild left peri antral soft tissue (arrows in a) is seen in the first patient. Rim enhancing abscess in left pre antral soft tissue (star) with mild retro antral soft tissue (arrow in b) is seen in the second patient. Contralateral pre antral and retroantral fat is normal (notched arrows in b).

FIG. 4

Illustration (a) depicting the pterygopalatine fossa (PPF, inverted truncated cone) and routes of its multidirectional spread. Three different patients with CAM depicting multidirectional spread via PPF. Axial contrast enhanced computed tomography (CECT) image (b) depicts minimal soft tissue in left pterygopalatine fossa (curved black arrow in b), contralateral PPF is normal (straight black arrow). Axial and coronal CECT images in another patient (c,d) depict soft tissue contents within posterior nasal cavity extending via sphenopalatine foramen to PPF (notched white arrow in c), further extending into infratemporal fossa via pterygomaxillary fissure (curved black arrow in c). Spread to the orbit is seen via inferior orbital fissure (circular white arrow in c and d). Axial CECT image (e) reveals perineural extension of disease to middle cranial fossa via foramen rotundum (notched white arrow in e).

FIG. 5

A 50-year-old female with uncontrolled hyperglycaemia and CAM. Axial (a) and coronal reformatted (b) CT images demonstrate bony erosions of walls of bilateral maxillary sinuses (curved arrows), left zygomatic bone (notched arrow), left frontal bone (2 notched arrows), floor of bilateral orbits (Thin straight arrows) and hard palate (2 thin straight arrows).

FIG. 6

Two patients with CAM with orbital involvement.Coronal contrast enhanced CT of the first patient shows (a) infiltration of soft tissue into left nasolacrimal duct (black arrow), lacrimal sac and medial orbital quadrant (black star). The patient underwent left orbital exentration and pus filled lacrimal sac was found intra-operatively.In another post functional endoscpic sinus surgery (FESS) CAM patient and no perception of light in left eye, coronal CT images (b-d) show abscess in superomedial compartment of left orbit (black arrow in b) extending posteriorly to involve the optic nerve which shows thickening and rim enhancement (white arrow in c). Adjacent extraocular muscles are bulky (white stars in c). The disease extends to the orbital apex (curved black arrow in d). Intracranial extension is also depicted through the eroded cribriform plate (notched black arrows in b and c).

FIG. 7

Three different patients with CAM and globe involvement with complete loss of vision in right eye. Axial contrast enhanced CT images reveals proptosis of right eye with optic nerve stretching and conical deformity of posterior globe giving the “Guitar pick” sign (straight white arrow in a), choroid detachment (curved white arrow in b) and lens dislocation (black arrow in b) and heterogenously enhancing soft tissue involving the coats of the globe and extending into the globe (notched white arrow in c).

FIG. 8

Three different patients with CAM with intracranial involvement. Contrast enhanced CT axial images reveals heterogenous enhancing soft tissue thickening in right sided sinuses with extension into the right orbital apex (black arrow in a) with contiguous spread to the cavernous sinus and its thrombosis (straight white arrow in a), rim enhancing abscess in left frontal lobe (Curved black arrow in b) and infarct in territory of left middle cerebral artery (notched white arrow in c).

FIG. 9

A 43-year-old patient with CAM. Post contrast coronal (a) and axial MR images (b,c) depict enlarged left foramen rotundum and vidian canal (white arrowhead and white arrow in a respectively) with thickened and enhancing left maxillary (arrow in b) and vidian nerves (arrow in c). Normal contralateral foramina are depicted by red arrows in a. (Color version of figure is available online.)

FIG. 10

A 58-year- old diabetic with CAM; Coronal reformatted CT at bone (a) and soft tissue (b) windows demonstrate perineural spread of disease, seen as subtle widening of vidian canal (yellow arrow in a) and foramen rotundum (curved yellow arrow in a) with loss of juxtaforaminal fat pad (red arrow in b). Normal contralateral foramina are depicted by white arrows. Coronal reformatted (c) CT image in another case of CAM depicts widened and eroded right foramen ovale (white arrowhead in c). Note made of normal left foramen ovale (notched yellow arrow in c). (Color version of figure is available online.)