Rhinosinusitis (RS) refers to the presence of inflammation in the paranasal sinuses mucosa (i.e., the lining of the sinuses) and the contiguous mucosa of the nasal passages. When it is present for less than one month, the condition is termed acute rhinosinusitis. If the inflammation is present for more than 12 weeks, then chronic rhinosinusitis is present. If the duration is between 4 and 12 weeks, the rhinosinusitis should be considered subacute. Recently, chronic rhinosinusitis (CRS) has been further classified as CRS with nasal polyps and CRS without nasal polyps.
The causes of RS are diverse, and often it is not possible to precisely identify a specific cause.
Furthermore, RS may mimic other conditions, including isolated inflammation of the nasal lining (rhinitis). Precise diagnosis includes a detailed history, examination, specific testing and imaging studies, and serves as the foundation for appropriate treatment.
Video caption: This video segment shows the aspiration of pus from the left middle meatus—a marker of chronic rhinosinusitis
Rhinosinusitis has been classified based upon its duration:
- Acute rhinosinusitis: duration of less than 4 weeks
- Subacute rhinosinusitis (duration of 4-12 weeks)
- Chronic rhinosinusitis (duration of greater than 12 weeks)
- Acute exacerbation of chronic rhinosinusitis (exacerbation of chronic rhinosinusitis, with return to baseline symptoms after appropriate treatment)
The precise etiology of chronic rhinosinusitis (CRS) is unknown. In considering the possible causes of CRS, it is important that consider that CRS may not be a single disorder with a single cause. Instead, CRS may be a poorly characterized syndrome with multiple discrete causes. Unfortunately, science has not explained the exact cause of CRS.
Numerous causes for CRS have been proposed:
Some studies have shown that inhalant allergy seems to occur more commonly in patients with CRS than in the general population; thus, it has been proposed that allergy may be factor in the development of CRS.
In at least some patients with CRS, the presence of specific bacteria seems related to the status of the CRS. In this view, bacteria start and sustain the process of CRS.
Biofilms are complex, three-dimensional structures of living bacteria. They have been identified in approximately 25–33% of patients with CRS in some studies.
Cultures of sinus secretions from patients with CRS have grown fungus. Furthermore, it has been shown that the immune system of patients with CRS have a greater response when exposed to fungal proteins at least in the laboratory.
Patients with cystic fibrosis (CF), a hereditary condition that effects mostly the lungs, also develop significant CRS. CF and other genetic diseases may be causes of CRS.
The bone in the walls of the sinuses of patients with severe CRS undergoes a remodeling process that produces thicker, but abnormal bone. This finding, known as osteitis, suggests that changes in the bone may contribute to CRS.
Under normal circumstances, the lining of the sinuses is covered by a think blanket of mucus, which is propelled in a programmed fashion by cilia on the surface of the sinus lining. These cilia act as oars to move the mucus. Disruption of this activity leads to stagnation of the mucus, and eventually infection and CRS.
The ostiomeatal complex region is the common outflow channel for the anterior ethmoid, frontal and maxillary sinuses. Blockage of the OMC causes blockage of the “upstream” sinuses and CRS.
Certain species of Staphylococcus can secrete substances (known as exotoxins) that can directly stimulate the immune system to produce a strong inflammatory reaction and CRS.
ASA triad (also known as Sampter’s triad) is characterized by nasal polyps, asthma, and aspirin intolerance. In these patients, aspirin produces a skin reaction, asthma, and even a severe reaction that can be life threatening.
Churg-Straus Syndrome (also known as granulomatous vasculitis) results from a inflammation of blood vessels. Patients with this condition have severe asthma, sinusitis, and other related illnesses.
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