The optic nerve, cavernous sinus, carotid artery, and sella turcica are adjacent to the sphenoid sinus. Tumors and infection in the sphenoid sinuses can progress to involve these structures. The enlarged turbinate can obstruct ventilation of the middle meatus and may cause sinusitis. Frontal recess cells can be variable in number and size. When present, they can impinge in the nasofrontal duct, leading to frontal sinusitis.
Septal deviation can predispose to sinusitis if the deviation narrows the middle meatus.
With long-standing deviation, atrophy of the middle turbinate and narrowing of the ostiomeatal complex is commonly seen. The sinuses are air-filled cavities with classical pseudostratified ciliated columnar epithelium interspersed with goblet cells. The cilia sweep mucus towards the ostial opening. Obstruction of sinus ostia may lead to mucous impaction and decreased oxygenation in the sinus cavities. During obstruction of the ostia, the pressure in the sinus cavity can decrease, which in turn causes the symptom of pain, particularly in the frontal region.