Mucocele
1. Definition: A mucocele is a chronic, expansile, mucus-filled cystic lesion of a paranasal sinus caused by obstruction of its natural drainage pathway. The mucosa continues to secrete mucus → trapped mucus expands → bony thinning, remodeling, and erosion → possible extension into orbit or cranial cavity. Mucoceles are benign but locally destructive.
2. Etiopathogenesis
Primary Mechanism: Obstruction of the sinus ostium → accumulation of mucous secretions → gradual expansion → bone resorption by pressure.
Etiological Factors
- Trauma: Previous facial or sinus trauma leading to scarring and ostial closure.
- Surgery: Previous Functional Endoscopic Sinus Surgery (FESS) with post-operative scarring.
- Inflammatory: Severe chronic rhinosinusitis with significant mucosal edema or large nasal polyps.
- Neoplasm: Benign or malignant tumors obstructing the ostium.
- Anatomical: Severe septal deviation or a large concha bullosa causing external compression.
Location
- Frontal Sinus (Most Common): 60-65% of cases. The narrow frontal ostium is easily obstructed.
- Ethmoid Sinus (Second Most Common): 20-25%.
- Maxillary and Sphenoid Sinuses: Less common.
Epithelium is respiratory, not squamous (→ not a cholesteatoma)
3. Classification
- Simple Mucocele: Contains sterile, thick, mucoid secretions.
- Infected Mucocele (Pyocele or Mucopyocele): The trapped secretions become secondarily infected, typically following an upper respiratory tract infection. This results in a clinical picture resembling an acute abscess, with rapid expansion and more severe symptoms.
4. Clinical Picture
Symptoms (Slow Expansion - Simple Mucocele)
- Frontal/Ethmoid Mucocele:
- Painless, slow-growing swelling in the superomedial orbital region (the corner of the eye near the nose).
- Proptosis (forward displacement of the eyeball), diplopia (double vision), or visual disturbances due to compression of the optic nerve or displacement of the globe.
- Dull, chronic headache/facial fullness. Restricted eye movements
- Sphenoid Mucocele:
- Severe, deep-seated headache (occipital or vertex).
- Cranial nerve palsies (especially III, IV, V, VI) due to compression in the cavernous sinus or superior orbital fissure.
- Visual loss (if the optic canal is compressed).
Signs (Infected Mucocele/Pyocele)
- Signs of acute infection: Fever, pain, redness, and tenderness over the swelling.
- Rapid onset of orbital signs (proptosis, ophthalmoplegia).
5. Paraclinical and Radiological Examinations
- CT scan (non-contrast): Gold Standard
- Classic Appearance: A homogeneous, non-enhancing, smoothly marginated, expanded, and opacified sinus.
- Bony Changes: Thinning and expansion (scalloping) of the sinus walls, or bony destruction where the mucocele has broken through (dehiscence), often into the orbit.
- Pyocele: May show rim enhancement, indicating an infected collection.
- MRI: MRI → if intracranial extension suspected