What is the approach to investigating and treating fungal sinusitis?

Fungal Sinusitis Investigation and Treatment

Initial Clinical Assessment

Maintain a high index of suspicion for fungal sinusitis in immunocompromised patients presenting with fever, rhinorrhea, facial pain, or orbital symptoms, as acute invasive fungal sinusitis carries a 50-80% mortality rate and requires immediate diagnostic workup and treatment. 1

High-Risk Patient Populations

• Immunocompromised patients including those with neutropenia, hematologic malignancies, poorly controlled diabetes, HIV/AIDS, organ transplantation, or those on systemic steroids and chemotherapy are at highest risk for acute invasive fungal sinusitis 1, 2
• Atopic children with refractory sinus disease should raise suspicion for allergic fungal sinusitis 1
• Aspergillus and Mucoraceae species cause most invasive cases 1, 2

Critical Physical Examination Findings

• Nasal endoscopy is essential and may reveal pale mucosa progressing to ulceration and necrosis in invasive disease 1
• Painless nasal septal necrosis is the classical presentation of acute invasive fungal sinusitis 1
• Any patient with orbital swelling, pain, forehead swelling, or diplopia requires urgent evaluation for complications 3

Diagnostic Imaging Approach

First-Line Imaging: CT Without Contrast

CT of the paranasal sinuses without contrast is the optimal initial imaging modality for suspected fungal sinusitis, as it demonstrates hyperattenuation in involved sinuses, bony erosions, and infiltration of surrounding spaces. 1

Key CT Findings in Fungal Sinusitis

• Hyperattenuation within sinuses suggests fungal disease but is nonspecific 1
• Bone erosion and periantral fat infiltration have high specificity but limited sensitivity in early disease 1
• Seven-variable diagnostic model (infiltration of periantral fat, pterygopalatine fossa, nasolacrimal duct/lacrimal sac, bone dehiscence, septal ulceration, orbital involvement) with any 2 positive findings demonstrates 88% sensitivity and 100% specificity 1
• Emphysematous soft tissue in the nasal cavity is a specific sign of early invasive fungal sinusitis 1
• Unilateral lesions, nodular mucoperiosteal thickening, focal bone destruction, and dense intrasinus concretions are classic findings 1

MRI With Contrast for Specific Indications

MRI with contrast is indicated when evaluating for orbital or intracranial extension, differentiating inflammatory disease from malignancy, or when CT findings suggest invasive disease. 1

MRI Indications and Findings

• Skull base dehiscence with opacification 1
• Unilateral sinonasal opacification on CT requiring further characterization 1
• Suspected orbital or intracranial extension (MRI is more sensitive than CT for these complications) 1
• T2-weighted signal characteristics help differentiate: very low signal with fungal concretions (similar to air), high signal with bacterial inflammation, intermediate signal with neoplastic processes 1
• MRI assists in clarifying degree of orbital or intracranial extension in complicated sinusitis 1

Imaging Timing Considerations

• Perform imaging more than 2 weeks after upper respiratory infection and more than 4 weeks after acute bacterial sinusitis when evaluating chronic disease 1
• In suspected acute invasive fungal sinusitis, imaging should be performed immediately given the high mortality rate 1

Definitive Diagnosis

Biopsy with histopathologic identification of invasive fungi in sinonasal mucosa, vessels, and bone is the gold standard for definitive diagnosis of fungal sinusitis. 1

Diagnostic Procedures

• Nasal-sinus biopsy is essential for confirming fungal disease, determining if lesions are neoplastic, and identifying granulomatous disease 1
• Histopathology remains the gold standard despite advances in molecular testing 2
• Panfungal PCR is playing an increasingly larger role in diagnosis 2

Additional Laboratory Testing

• Fungal-specific IgE testing (skin test or in vitro blood test) for allergic fungal sinusitis 1
• Total serum IgE levels may be elevated in allergic fungal sinusitis 1
• Fungal culture provides additional supportive evidence 1
• Nasal cytology demonstrating eosinophils suggests allergic fungal sinusitis 1

Treatment Approach

Acute Invasive Fungal Sinusitis

Treatment requires immediate initiation of systemic antifungal therapy (liposomal amphotericin B empirically), aggressive surgical debridement, and reversal of immunosuppression. 1, 2

• Liposomal amphotericin B should be initiated empirically, then transitioned to targeted therapy when pathogen is identified 2
• Surgical debridement of necrotic tissue is essential for both diagnosis and treatment 1, 2
• Reversal of underlying immunosuppression is equally or more important than medical/surgical management 2
• Despite aggressive management, mortality approaches 50% 2

Allergic Fungal Sinusitis

Endoscopic sinus surgery must be combined with long-term medical therapy including oral and nasal corticosteroids, with consideration of immunotherapy and antifungal agents. 4

• Surgery alone is insufficient; requires long-term medical management 4
• Therapy aims to disrupt the inflammatory process and restore normal mucosal function 4
• Allergic fungal sinusitis in children is less responsive to treatment with higher recurrence rates compared to adults 1

Critical Pitfalls to Avoid

• Do not delay imaging or treatment in immunocompromised patients with sinonasal symptoms, as acute invasive fungal sinusitis progresses rapidly 1, 2
• Do not rely on standard radiographs, as they have poor sensitivity and are inadequate for fungal sinusitis evaluation 1
• Do not use MRI as first-line imaging due to lack of bony detail, though it is superior for evaluating complications 1
• Do not assume negative early CT excludes invasive disease, as bone erosion and fat infiltration have limited sensitivity in early phases 1
• Recognize that presenting symptoms are nonspecific (fever, rhinorrhea, diplopia) and overlap with acute bacterial rhinosinusitis 1