Patterns of sinonasal obstruction vary, and distinguishing between them is useful for localizing the area of pathology and narrowing the differential diagnosis. 

Radiographic features

Babbel et al. described five patterns of sinonasal obstruction ¹, which are readily apparent on CT and widely used:

Infundibular pattern

• opacification of maxillary sinus

• obstruction of the ipsilateral maxillary ostium and infundibulum

• causes: mucosal swelling, sinonasal polyp, Haller cells

• may progress to silent sinus syndrome

Ostiomeatal unit pattern

• opacification of the ipsilateral maxillary sinus, frontal sinus, and anterior and middle ethmoid air cells

• obstruction of the middle meatus

• may be an incomplete pattern due to variable drainage pattern

• causes: mucosal swelling, turbinate hypertrophy, polyps, tumors/masses, concha bullosa, paradoxical middle turbinate, nasal septal deviation

Sphenoethmoidal recess pattern

• opacification of the ipsilateral sphenoid sinus +/- posterior ethmoid air cells

• obstruction of the sphenoethmoidal recess

Sinonasal polyposis pattern

• polypoid masses in the nasal cavity and paranasal sinuses

• bilateral maxillary infundibulum widening

• convex ethmoid air cell walls

• attenuation (change) the nasal septum and ethmoid air cell walls

• +/- infundibular, ostiomeatal, sphenoethmoidal recess patterns depending on secondary obstruction

Sporadic (unclassifiable) pattern

• all other patterns not attributable to obstruction or sinonasal polyposis

• post-surgical change is also included in this group

• causes: mucous retention cyst, mucocele