Pathogenesis

Acute Sinusitis

Four host factors determine the susceptibility to sinusitis, including patency of the ostia, ciliary function, quality of secretions, and local host immunity. Most commonly, a viral upper respiratory infection results in acute obstruction of one or more ostia. This blockage leads to reduced oxygen content and the development of mucosal edema and serum transudation within the sinus cavities. These alterations foster bacterial growth reduce ciliary movement and alter leukocyte function, eventuating in the signs and symptoms of acute bacterial sinusitis. The sinuses will usually return to normal either spontaneously or following antimicrobial therapy. Common conditions that predispose to sinusitis are listed in Table 1.

Cronic Sinusitis

Chronic sinusitis is characterized by persistent mucosal inflammation, with histological evidence of edema and a mixed cellular infiltrate (eosinophils and lymphocytes). The marked thickening of sinus tissue observed microscopically, macroscopically, and radio-graphically has given rise to the term "hyperplastic sinusitis." Nasal polyps, which are commonly identified in patients with chronic sinusitis, represent evaginations of sinus mucosa and are histologically identical to the tissue from which they originate. Although both aeroblic and anaerobic bacteria as well as fungi may be cultured from the sinus cavities of patients with chronic sinusitis, the true role of these organisms as infectious pathogens is unclear.

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