Sinonasal polyposis refers to the presence of multiple benign polyps in the nasal cavity and paranasal sinuses.

Epidemiology

Sinonasal polyposis is most commonly encountered in adults and rare in children. Polyps are the most common expansile lesions of the nasal cavity ⁸.

Associations

Conditions known to be associated with polyps include ¹⁰:

• infectious rhinosinusitis

• cystic fibrosis

• allergic fungal sinusitis

• asthma

• nickel exposure

• eosinophilic granulomatosis with polyangiitis

Clinical presentation

Clinical symptoms of sinonasal polyposis may include progressive nasal obstruction, rhinorrhea, facial pain, headache, anosmia, etc. ³. It can also cause a particular pattern of chronic sinusitis as a result of obstruction of the drainage pathways of the paranasal sinuses.

Pathology

Polyps are formed by the influx of fluid into the lamina propria of the sinonasal Schneiderian mucosa ^8,9.

Classification

The Meltzer grading system is a clinical grading system that is as follows ¹:

• grade 0: no visible polyposis

• grade 1: small polyps confined to the middle meatus

• grade 2: multiple polyps occupying the middle meatus

• grade 3: extending beyond the middle meatus

• grade 4: nasal cavity obstruction

Radiographic features

CT

• extensive mucosal polyps occupying and obliterating the nasal cavity and the paranasal sinuses

  • usually, they are hypodense but may be hyperdense due to increased protein content or fungal infection

• associated local benign bone remodeling or erosion (as opposed to a mucocele where the entire sinus is expanded ⁶)

  • enlargement of infundibula

  • attenuation of the ethmoid sinus walls and nasal septum

  • occasionally sparing the inferior nasal meatus

  • truncation of middle turbinate ⁴

• opacified ethmoid sinuses with convex lateral walls and gas-fluid levels

• a concurrent fungal sinus infection may be present

Complications

• osseous metaplasia ¹¹

• aspirin exacerbated respiratory disease (AERD)

Differential diagnosis

• sinonasal retention cyst

  • can be indistinguishable 

  • usually spares the nasal cavity

• allergic fungal sinusitis

  • commonly associated with polyps 

  • hyperdense central areas 

  • MRI may show low T1 and T2 signal

• granulomatosis with polyangiitis

  • centered in the nasal cavity