Acute sinusitis has considerable overlap in its constellation of signs and symptoms with URIs. One half to two thirds of patients with sinus symptoms seen in primary care are unlikely to have sinusitis (35). In 300 patients who presented with a URI, 19% had radiographic evidence of maxillary sinusitis, but had no symptoms of sinus infection (30). URIs are often precursors of sinusitis and at some point symptoms from each condition may overlap. Sinus inflammation from a URI without bacterial infection is also common. In a series of 60 children undergoing computerized tomography (CT) for non-sinus-related diagnoses, 47% had evidence of sinus inflammation with no clinical signs of sinusitis and with complete resolution following their viral illness (36).
Acute sinusitis tends to start with a URI that leads to sinus ostial obstruction. The signs and symptoms that increase the likelihood that the patient has acute sinusitis are a "double sickening" phenomenon whereby the patient seems to improve following the URI and then deteriorates, maxillary toothache, purulent nasal discharge, poor response to decongestants, and a history of discolored nasal discharge (37,38). Other authors have stressed that the symptoms need to persist longer than 1 wk to distinguish sinusitis from a URI (39). It should be pointed out that the commonly used sign of facial pain or swelling has low sensitivity for acute sinusitis (38).
Because sinusitis is most often a complication of upper respiratory viral infections, it follows the same seasonal pattern as colds. This produces a winter peak with more cases seen in those exposed to upper respiratory tract infections.
In children seen in a large health system, sinusitis is frequently found as a co-morbidity with otitis media. Nearly half of all children with sinusitis also had otitis media (40). Children are also more likely to have posterior ethmoidal and sphenoid inflammation while adults have mainly maxillary and anterior ethmoidal sinusitis (41). Some medical conditions may increase the risk for sinusitis. These include cystic fibrosis, asthma, immunosuppression, and allergic rhinitis (42). Cigarette smoking may also increase the risk of bacterial sinusitis during a cold because of reduced mucociliary clearance.
Sinus inflammation can be caused by viral, fungal, and bacterial infections as well as allergies. The majority of acute sinusitis is caused by viral infection. As indicated previously, many cases of the common cold have concomitant sinus inflammation. The inflammation associated with viral infections clears without additional therapy.
Bacterial superinfection of URIs is rare and occurs in only 0.5-1% of colds. Studies examining the treatment of sinusitis confirm that response rates to antibiotics are either small (43). When sinusitis is confirmed by CT scan, response rates to antibiotics are improved (44).
Cultures of material obtained from patients with sinusitis show that the most prevalent organisms are Streptococcus pneumoniae and, especially in smokers, H. influenzae. These two organisms are present in 70% of cases of bacterial acute sinusitis (45). When antibiotics are used for the treatment of bacterial sinusitis, selection of antibiotics should include sufficient coverage of these two organisms.
Antibiotics are commonly prescribed for adult patients who present with complaints consistent with acute sinusitis. The effectiveness of antibiotics is unclear. Three recent placebo-controlled, double-blind, randomized trials in general practice settings have yielded mixed results (43,44,46). Two of these trials showed no beneficial effect of antibiotics (43,46) while the third demonstrated a significant effect of penicillin and amoxycillin (44). The trial showing an effect used more stringent enrollment criteria than the other two, which are more consistent with those used in daily practice by primary care physicians. These data suggest that patients with more severe signs and symptoms may benefit from an antibiotic. If an antibiotic is to be used, some evidence with trimethoprim-sulfamethoxazole suggests that treatment of short duration (e.g., 3 d) is as effective as longer treatment (47). Further, narrow-spectrum agents seem as effective as broad-spectrum agents (48).
Antibiotics have some utility in treating acute sinusitis in patients with severe signs and symptoms. If antibiotics are to be used, short-course therapy with narrow-spectrum agents is recommended. The key to judicious use of antibiotics is to first make an accurate diagnosis of sinusitis rather than overtreating URIs.
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