Sinusitis is one of the most commonly diagnosed ailments in clinical practice, yet criteria for its diagnosis may be variable and a standard treatment protocol is nonexistent. The majority of patients with acute sinusitis improve without any therapy or with over-the-counter remedies. The temptation to treat an upper respiratory infection with antimicrobials should be avoided, especially in light of increasing bacterial resistance profiles. An understanding of the anatomy, pathophysiology with predisposing factors, and common microbiology helps drive therapeutic decision making.

SINUS ANATOMY

The paranasal sinuses consist of paired maxillary, ethmoid, sphenoid, and frontal sinuses. The maxillary and ethmoid sinuses are present at birth and fully pneumatize during childhood. The paired sphenoid and frontal sinuses appear in childhood and continue to pneumatize into early adulthood in some cases. The maxillary, anterior ethmoid, and frontal sinuses drain into the osteomeatal complex (OMC). The OMC is a functional physiological unit comprising the ethmoid infundibulum, middle meatus, and surrounding structures. The OMC and its patency are the keys to normal sinus drainage and the maintenance of physiologic mucociliary clearance.

PATHOPHYSIOLOGY

Any anatomic anomaly, environmental exposure, or disease process, acute or chronic, that prevents the normal mucociliary clearance either by functional obstruction or by thickening of nasal secretions may result in pathogen overgrowth and sinusitis. Typically these processes or exposures affect not only the paranasal sinus mucosa but also the intranasal mucosa, prompting use of the term rhinosinusitis.