(VRS) will develop into bacterial infections in adults and 5 to 10% in children. Pathophysiology Biofilm bacterial infections may account for many cases of antibiotic-refractory chronic sinusitis. Biofilms are complex aggregates of extracellular matrix and interdependent microorganisms from multiple species, many of which may be difficult or impossible to isolate using standard clinical laboratory techniques. Bacteria found in biofilms have their antibiotic resistance increased up to 1000 times when compared to free-living bacteria of the same species. A recent study found that biofilms were present on the mucosa of 75% of people undergoing surgery for chronic sinusitis. Diagnosis Classification Sinusitis (or rhinosinusitis) is defined as an inflammation of the mucous membrane that lines the paranasal sinuses and is classified chronologically into several categories: Acute sinusitis – A new infection that may last up to four weeks and can be subdivided symptomatically into severe and nonsevere. Some use definitions up to 12 weeks. Recurrent acute sinusitis – Four or more full episodes of acute sinusitis that occur within one year Subacute sinusitis – An infection that lasts between four and 12 weeks, and represents a transition between acute and chronic infection. Chronic sinusitis – When the signs and symptoms last for more than 12 weeks. Acute exacerbation of chronic sinusitis – When the signs and symptoms of chronic sinusitis exacerbate, but return to baseline after treatment. Roughly 90% of adults have had sinusitis at some point in their lives. Acute Health care providers distinguish bacterial and viral sinusitis by watchful waiting. If a person has had sinusitis for fewer than 10 days without the symptoms becoming worse, then the infection is presumed to be viral. When symptoms last more than 10 days or get worse in that time, then the infection is considered bacterial sinusitis. Pain in the teeth and bad breath are also more indicative of bacterial disease. Imaging by either X-ray, CT or MRI is generally not recommended unless complications develop. Pain caused by sinusitis is sometimes confused for pain caused by pulpitis (toothache) of the maxillary teeth, and vice versa. Classically, the increased pain when tilting the head forwards separates sinusitis from pulpitis. For cases of maxillary sinusitis, limited field CBCT imaging, as compared to periapical radiographs, improves the ability to detect the teeth as the sources for sinusitis. A coronal CT picture may also be useful. Chronic For sinusitis lasting more than 12 weeks, a CT scan