Key findings. From Diagnostic Imaging: Head and Neck by H. Ric, Harnsberger

1. Paranasal sinus
mucocele
Imaging findings

2. due to mucus secretion into chronically obstructed sinus
accumulated secretions cause pressure necrosis of sinus walls
with bone erosion of inner sinus wall and new bone formation
> 90% frontal + ethmoidal

3. histologically indistinguishable
from polyps and retention cysts

4. opacified sinus
with mucoid or soft tissue density
hyperdense if low water or fungal colonization
bone expansion
bone may be focally absent
look for thin peripheral rim of expanded bone
nonenhancing
with extensive peripheral enhancement think of mucopyocele
with central enhancement favor neoplasm

5. bone CT may be sufficient if small mucocele
 look for cause of sinus obstruction
chronic inflammation
prior trauma, surgery
neoplasm
if large expansile lesion, perform CE MRI

6. DDX expansile sinus lesions
mucocele
most common expansile lesion of paranasal sinuses
sinonasal polyposis
alergic fungal rhinosinusitis
antrochoanal polyp
sinonasal neoplasm

7. Remember
most common paranasal sinus
expansile lesion