Paranasal sinuses rule 2 :Obstruction of maxillary sinus osteum

Maxillary sinus ostium is seen obstructing by mucosal thickening due to chronic infection or neoplasm

Ostiomeatal unit line drawing: inferior turbinate (1), middle turbinate (2), maxillary sinus (M), uncinate (U), ethmoidal bulla (B), frontal sinus (F), ethmoidal Infundibulum (INF), nasal septum (NS), and (*) middle meatus

§Coronal view demonstrating the blockage of the Ostiomeatal complex by a large conchae bullosa (CB). Important components of the Ostiomeatal complex that can be seen include the uncinate process (U) and maxillary sinus ostium (MO). The attachments of the middle turbinate (MT*) to the cribriform plate (cb) and of the uncinate process (U*) to the skull base can be appreciated. The fovea ethmoidal (fv) and crista galli (^) can also be seen.