March 19, 2020
A 27-year-old man with nasal congestion and facial pain for 1 week; history of nasal polypectomy at 16 years of age
Allergic Fungal Rhinosinusitis with Intracranial Extension
- Background:
- Allergic fungal rhinosinusitis (AFRS) is an increasingly recognized disease found mainly in areas with high humidity, where mold counts are higher than other regions.
- Estimated to occur in 5–10% of patients affected by chronic rhinosinusitis
- Bent and Kuhn (1994) proposed 5 major diagnostic criteria for AFRS: type I hypersensitivity, nasal polyposis, characteristic CT findings, eosinophilic mucus without tissue invasion, and fungal presence in sinus contents.
- Total immunoglobulin E values are usually elevated in AFRS, with patients often presenting values of over 1000 U/mL (>2000 U/mL in this case). Patients may also present with peripheral blood eosinophilia.
- When positive, cultures from patients with AFRS most commonly grow dematiaceous fungi such as Bipolaris, Alternaria, Curvularia, or Aspergillus species. (In this case, cultures grew Aspergillus flavus.)
- Clinical Presentation:
- The typical patient with AFRS is a young (usually third decade), immunocompetent patient with unilateral or asymmetric involvement of the paranasal sinuses, carrying a history of atopy and nasal polyposis.
- Key Diagnostic Features:
- Unenhanced cross-sectional CT imaging findings include complete opacification with heterogeneous but predominantly hyperattenuating material in the lumen of the paranasal sinuses as characteristic features. Erosion of the sinus walls and orbitocranial expansion are not uncommon.
- MRI shows variable T1 appearance and a T2 central signal void (due to higher protein and low free-water content in eosinophilic mucin together with heavy metal deposition such as iron and manganese) surrounded by high peripheral signal of the inflamed mucosal lining, enhanced by intravenous gadolinium contrast.
- Differential Diagnoses:
- Acute or chronic invasive fungal sinusitis: Generally occurs in patients who are diabetic or immunocompromised; CT usually shows homogeneous opacification (iso/hypoattenuating in the acute form and iso/hyperattenuating in the chronic form).
- Chronic rhinosinusitis with fungal allergy: Markedly hyperintense T2WIs of the inflammatory mucosal disease favor this diagnosis. Hyperostosis of the sinus walls in chronic rhinosinusitis can also be seen, as opposed to the lytic change seen in AFRS.
- Fungal mycetoma: Unaccompanied by an immunologic response; less commonly cause bony erosion/expansion and is usually limited to a single sinus
- Sinus mucocele: Usually has a water-rich content with low T1 and high T2 signal intensity on MRI
- Sinonasal non-Hodgkin lymphoma (NHL): CT shows a more homogeneous soft tissue density lesion. A destructive paranasal sinus mass can also be seen but the presence of associated nasopharyngeal soft tissue and cervical lymphadenopathy points toward NHL.
- Treatment:
- Surgical removal of the fungal debris and allergic mucin to restore normal sinus drainage is the most effective way to treat AFRS.
- Additional surgeries may be required as disease recurrence is not uncommon.
- Immunotherapy and anti-inflammatory treatment may also be used to suppress the immune response.
- The role of antifungal therapy is not yet clearly established.
