Invasive fungal sinusitis is a life-threatening infection in which fungal organisms penetrate beyond the sinus mucosa to invade bone, vascular structures, and adjacent tissues (orbit, brain). The acute invasive form most commonly occurs in immunosuppressed patients (uncontrolled diabetes/diabetic ketoacidosis, hematologic malignancy, bone marrow transplantation, prolonged neutropenia) and the most frequent causative organisms are Aspergillus and Mucorales (Rhizopus, Mucor) species. Mucormycosis is particularly characterized by vascular invasion and thrombosis — the angioinvasive property leads to rapid tissue necrosis. Mortality without treatment is 50-80%; emergent surgical debridement and aggressive antifungal therapy (amphotericin B) are required. Chronic invasive and granulomatous invasive forms have a slower course and can occur in immunocompetent individuals.
Age Range
30-80
Peak Age
55
Gender
Equal
Prevalence
Rare
In acute invasive fungal sinusitis, fungal spores reach the sinus mucosa via inhalation; because host defense mechanisms are insufficient in immunosuppressed patients, fungal organisms penetrate the mucosa and invade submucosal tissue, periosteum, and bone. Mucorales species demonstrate strong angioinvasive properties — fungal hyphae invade vessel walls causing arterial thrombosis and downstream tissue ischemia/necrosis. This vascular thrombosis and tissue necrosis is reflected on CT as non-enhancing (devitalized) mucosa and soft tissue; the lack of enhancement in necrotic tissue is a direct consequence of vascular occlusion. Aspergillus species can also be angioinvasive but progress more slowly than mucormycosis. Bone destruction results from both direct fungal invasion and osteonecrosis due to vascular compromise. Intracranial extension occurs via direct invasion (anterior cranial fossa) or perineural/perivascular spread.
Non-enhancement of the inferior or middle turbinate mucosa on contrast-enhanced CT is one of the pathognomonic findings of mucormycosis. Normal turbinate mucosa shows prominent enhancement due to its dense vascular network; absence of enhancement reflects vascular thrombosis and mucosal necrosis/devitalization due to fungal angioinvasion. It correlates clinically with black/necrotic turbinate mucosa on endoscopic examination. This finding can be detected even in early stages and is a critical radiologic finding that indicates emergent surgical debridement. Unilateral involvement is more common and comparative evaluation with the contralateral side strengthens the diagnosis.
Non-enhancement of the infected sinus mucosa is seen on contrast-enhanced CT. This finding is a direct result of fungal angioinvasion causing vascular thrombosis and tissue necrosis. The 'black turbinate sign' — non-enhancement of the inferior or middle turbinate on contrast CT — is a specific finding described in mucormycosis indicating mucosal necrosis/devitalization. The enhancement status of surrounding tissues should be comparatively evaluated. Non-enhancing areas can form sharp borders with viable, enhancing tissues. The absence of this finding does not exclude invasive fungal sinusitis — in early stages, the mucosa may still be viable.
Report Sentence
Non-enhancement of the left ethmoid sinus and middle turbinate mucosa is noted on contrast-enhanced CT (black turbinate sign), suggesting devitalized/necrotic tissue consistent with invasive fungal sinusitis.
Bone erosion and destruction in sinus walls is a critical CT finding of invasive fungal sinusitis. Bone destruction results from both direct fungal invasion and osteonecrosis due to vascular compromise. Most commonly affected areas: lamina papyracea (orbital extension), anterior cranial fossa floor (intracranial extension), sphenoid sinus wall (cavernous sinus, internal carotid artery), hard palate (oral cavity). On bone algorithm CT, areas of subtle erosion, cortical irregularity, and focal defects should be sought. The extent and direction of bone destruction are critically important for surgical planning and prognosis.
Report Sentence
Bone destruction is noted in the left maxillary sinus medial wall and lamina papyracea, consistent with invasive fungal sinusitis; orbital extension should be evaluated.
Contrast-enhanced MRI is superior to CT in evaluating intracranial extension of invasive fungal sinusitis. Cavernous sinus involvement appears on contrast T1 as abnormal enhancement or filling defect in the cavernous sinus, loss of lateral wall convexity, and sinus expansion. Encasement and narrowing (stenosis/occlusion) of the internal carotid artery by fungal tissue is evaluated by MR angiography — this finding is critical for stroke risk. Perineural spread may be traced along the foramen rotundum (V2) and foramen ovale (V3) and can reach Meckel's cave. Meningeal enhancement indicates leptomeningeal involvement, while dural thickening indicates pachymeningeal involvement.
Report Sentence
Abnormal enhancement and expansion of the left cavernous sinus is noted on contrast-enhanced MRI with signal changes around the left internal carotid artery suggesting fungal tissue encasement; consistent with intracranial extension of invasive fungal sinusitis.
In invasive fungal sinusitis, intrasinus fungal tissue and secretions show characteristic hypointense signal on T2-weighted sequences ('T2 blackout'). This low signal results from paramagnetic elements in fungal hyphae (iron, manganese, calcium), high protein content, and desiccated secretions. T2 hypointensity should not be confused with air — on T1 sequences, air produces no signal while fungal tissue shows low-intermediate signal. The signal difference between viable mucosa and necrotic/fungal tissue is the fundamental advantage of MRI in diagnosing invasive fungal sinusitis. T2 signal changes (edema) in orbital fat tissue indicate extrasinus extension of fungal invasion.
Report Sentence
Material showing markedly hypointense signal on MRI T2-weighted sequences is noted in the right ethmoid and sphenoid sinuses, suggesting fungal content (T2 blackout).
DWI (Diffusion-Weighted Imaging) provides multiple pieces of information in invasive fungal sinusitis. Purulent/necrotic material within the sinus shows restricted diffusion (high DWI, low ADC). Restricted diffusion is also seen in orbital or intracranial abscess formations. Acute ischemic changes in brain parenchyma (infarction due to vascular invasion/thrombosis) are detected early with DWI — this finding directly affects clinical outcome. ADC values can help differentiate fungal abscess (<0.6-0.8 × 10⁻³ mm²/s), bacterial abscess (<0.7 × 10⁻³ mm²/s), and tumor (0.8-1.2 × 10⁻³ mm²/s).
Report Sentence
An area of restricted diffusion is noted in the left frontal lobe on DWI, suggesting acute ischemic change due to vascular invasion/thrombosis.
Obliteration of perisinusoidal (periantral) fat planes on non-contrast CT is an early and important finding indicating extrasinus extension of fungal invasion. Normal periantral fat tissue (low density between -50 and -100 HU) is seen between sinus walls and surrounding muscles. Infiltration replaces these fat planes with soft tissue density (0-50 HU). Obliteration of the retroantral (pterygopalatine fossa) fat plane indicates the potential pathway for spread to the sphenoid sinus and middle cranial fossa. Premaxillary and buccal fat plane obliteration may also indicate anterior extension. This finding should suggest perimucosal/transmural invasion, unlike benign inflammatory sinusitis.
Report Sentence
Obliteration of the left retroantral (pterygopalatine fossa) fat planes is noted, suggesting extrasinus extension of invasive fungal sinusitis.
CT angiography evaluates vascular complications in invasive fungal sinusitis. Due to the angioinvasive property of mucormycosis, thrombosis, stenosis, or occlusion can develop in the internal carotid artery and its branches — this can lead to cerebral infarctions that may result in hemiplegia, aphasia, or death. Cavernous sinus thrombophlebitis causes venous drainage dysfunction and ophthalmoplegia. On CT angiography, irregular wall, focal narrowing, or occlusion of the internal carotid artery may be seen. Pseudoaneurysm formation has been reported particularly in sphenoid sinus involvement — carries life-threatening hemorrhage potential due to rupture risk.
Report Sentence
Focal narrowing and irregular wall contour of the left internal carotid artery cavernous segment is noted on CT angiography, suggesting vascular involvement due to invasive fungal sinusitis.
Criteria
Rapidly progressive sinusitis in <4 weeks in immunosuppressed patient. Clinical setting of neutropenia (<500/µL), DKA, hematologic malignancy, organ transplantation. Mucorales or Aspergillus most common. Mortality 50-80%.
Distinct Features
Bone destruction, mucosal non-enhancement (black turbinate sign), fat plane obliteration, rapid orbital/intracranial extension on CT. T2 hypointense fungal tissue, DWI restriction, cavernous sinus involvement on MRI.
Criteria
Slowly progressive invasive fungal infection lasting ≥12 weeks. In mildly immunosuppressed or immunocompetent individuals (diabetic, low-dose steroid users). Aspergillus most common. Mortality lower than acute form (20-30%).
Distinct Features
Single sinus opacification + slowly progressive bone erosion on CT, bone sclerosis may accompany. T2 hypointense material on MRI. Unlike acute form, slower extension but risk of vision loss with orbital apex involvement.
Criteria
Chronic granulomatous inflammation lasting years in immunocompetent individuals. Aspergillus flavus most common. Endemic in hot-dry climate regions such as Sudan, India, Pakistan. Symptoms of proptosis and orbital/nasal obstruction.
Distinct Features
Homogeneous soft tissue mass in sinus and nasal cavity, bone remodeling > destruction, orbital extension on CT. Markedly T2 hypointense signal on MRI (granulomatous tissue + paramagnetic elements). Non-caseating granulomas and fungal hyphae on histology.
Distinguishing Feature
Sinonasal SCC appears as a solid enhancing mass; mucosal non-enhancement (devitalized tissue) is expected in invasive fungal sinusitis. T2 signal is usually intermediate-high in SCC, while T2 blackout is characteristic in fungal tissue. Clinical context (immunosuppression) and disease course (fungal = days-weeks, malignancy = months) are distinguishing.
Distinguishing Feature
Sinonasal lymphoma appears as a homogeneously enhancing mass and although bone destruction occurs, vascular invasion/thrombosis is not typical. DWI shows marked restriction in lymphoma (very low ADC — high cellularity), while T2 blackout is prominent in fungal tissue. Midline destruction can be seen in NK/T-cell lymphoma.
Distinguishing Feature
GPA (Wegener) shows midline destruction (nasal septum, hard palate), sinus mucosal thickening, and bone erosion. However, vascular invasion/thrombosis and black turbinate sign are not expected in GPA. c-ANCA (PR3) positivity helps in diagnosis. Clinical setting expects autoimmune disease context rather than immunosuppression.
Distinguishing Feature
Fungus ball is non-invasive — no bone destruction (sclerotic bone remodeling may be present), mucosa enhances, fat planes are intact. Hyperdense calcified material in a single sinus on CT is characteristic. Invasive fungal sinusitis shows bone destruction, mucosal non-enhancement, and extrasinus extension.
Urgency
emergentManagement
surgicalBiopsy
NeededFollow-up
Acil cerrahi debridman + agresif antifungal tedavi (liposomal amfoterisin B). Seri BT/MRG ile hastalık progresyonu ve tedavi yanıtı takibi. İmmünsüpresyonun düzeltilmesi (nötrofil recovery, DKA tedavisi) kritiktir. Mortalite hâlâ yüksek (%30-50 tedavi ile).Acute invasive fungal sinusitis is a radiologic emergency. When diagnosis is suspected, contrast-enhanced CT and/or MRI should be immediately obtained, endoscopic biopsy taken, and confirmed with frozen section histopathology. Treatment: emergent extensive surgical debridement (complete removal of necrotic tissue — including orbital exenteration if necessary) + IV liposomal amphotericin B (mucormycosis) or voriconazole (aspergillosis). Correction of immunosuppression (G-CSF, insulin, steroid reduction) should be performed simultaneously. Treatment response and disease progression are monitored with serial imaging. Multidisciplinary approach is required (ENT, infectious diseases, neurosurgery, ophthalmology, radiology). Mortality rises to 50-80% with intracranial extension.
Invasive fungal sinusitis is a life-threatening condition requiring emergency surgical debridement and aggressive antifungal therapy. Mortality rate can reach 50-80%. Early diagnosis is critically important. Correction of immunosuppression is a cornerstone of treatment.