Diagnosis:
Diffuse nasosinus polyposis.

Findings:
Diffuse multifocal mixed areas of increased and decreased signal on the T2-weighted images are noted. Notice how these masses have produced sphenoid sinus obstruction whose signal intensity is slightly higher and more homogeneous on the T2-weighted images than that of the masses themselves. The distribution and location of the masses and their mixed enhancement on contrast-enhanced MR is noteworthy. The findings are compatible with inflammatory polyposis of the nasal region, maxillary sinuses, and ethmoid sinus region.

Discussion:
Nasosinus Disease on MR

• Normal nasal cycle
o Mucoperiosteal T1 isointensity and T2 hyperintensity limited to the nasal septum, nasal cavity and ethmoid sinuses (< 2-3 mm mucosal thickness)
o Frontal, maxillary and sphenoid sinuses are spared
o Alternating fullness of right and left turbinates during day (frequent unilateral prominence, transient)

• True nasosinus inflammation:
o Isointense T1 and hyperintense T2 with frontal, maxillary or ethmoid sinus involvement (> 2-3 mm mucosal thickness)

• Mucus retention cyst or mucocele
o Serous type:
• Hypointense T1, hyperintense T2, homogeneous
o Mucoid type:
• Hyperintense T1, hyperintense T2, homogeneous
o Inspissated type:
• Hyperintense T1, hypointense T2

• Nasosinus polyp:
o Isointense T1 and hypointense center on T2, peripheral enhancement

• Squamous cell carcinoma or other malignancy:
o Mixed T1 intensity, intermediate T2 isointensity, inhomogeneous enhancement

• Rhinolith:
o Hypointense T1, hypointense T2

• Fungus ball/mycetoma:
o Intermediate T1, hypointense T2

Resources:
Pomeranz S J. Gamuts & Pearls in MRI - 2nd Edition. MRI-EFI Publications, Inc. 1993. p. 266