Description
Sinonasal polyposis (SNP) refers to the formation of benign, non-cancerous, inflammatory growths within the nasal passages and sinuses. These polyps result from chronic inflammation in these areas.
Pathogenesis
The exact pathogenesis of SNP remains unclear, but it is generally accepted that they arise due to an abnormal response to inflammation, potentially triggered by a variety of conditions such as allergy, infection, and immune disorders.
Epidemiology, Risk Factors & Associations
SNP is a common disease with a reported prevalence ranging from 1 to 4% of the general population. It tends to affect individuals in their middle age (most commonly in the 40-60 age range), and is more prevalent in males than in females (approximately 2:1 ratio).
Associated conditions include:
- Asthma
- Allergic rhinitis
- Aspirin sensitivity
- Cystic fibrosis
Clinical Features
The main symptoms of sinonasal polyposis include:
- Nasal obstruction
- Runny nose
- Postnasal drip
- Decreased sense of smell
Complications
Chronic sinusitis and secondary bacterial infections can occur. Larger polyps can cause facial pain or headache and can even alter the shape of the face.
Pathological Features
Histologically, sinonasal polyps are characterised by oedematous stroma and infiltration with inflammatory cells, mainly eosinophils.
Radiological Features
General Features
- Polypoid soft tissue masses filling the nasal cavity and paranasal sinuses.
- Concurrent fungal sinusitis may be present.
CT
- Polyps appear as hypodense, soft-tissue masses which obliterate the nasal cavity. Hyperdensity suggests increased protein content or fungal infection.
- They may cause bone thinning but not bony destruction.
MRI
- Polyps are typically hypointense on T1-weighted images and hyperintense on T2-weighted images.
Diagnosis
The diagnosis is typically made based on clinical history, physical examination, nasal endoscopy, and imaging studies. Biopsy may be needed in atypical cases or for differential diagnosis.
Differential Diagnosis
Imaging-based
- Sinonasal retention cyst: May be indistinguishable
- Allergic fungal sinusitis: Commonly associated with polyps and asthma. Hyperdense central areas with hypodense mucosa on CT, with corresponding low T1 and high T2 mucosa on MRI.
- Antrochoanal polyp: Typically unilateral and extends from the maxillary sinus to the nasopharynx.
- Juvenile angiofibroma: Affects adolescent males and shows aggressive bone erosion on imaging.
- Inverted papilloma: Shows irregular bone remodelling or erosion on imaging.
Management
Management of sinonasal polyposis includes medical therapy with corticosteroids and surgery for those unresponsive to medical treatment. The type of surgery depends on the extent and location of the polyps.