Epidemiology of rhinosinusitis

Introduction:

Sinusitis is one of the most common infections presenting to a primary care physician. The incidence of sinusitis parallels that of common cold proving the fact that infections involving the paranasal sinuses starts first as infection of the mucosal lining of the nasal cavity (rhinitis). Sinusitis is actually diagnosed twice as common in women when compared to that of men. This sex preponderance is not clearly understood.

Risk factors involved in the development of rhinosinusitis:

1. Allergic rhinitis
2. Swiming
3. Nasal block
4. Immunodeficiency states
5. Cleft palate
6. Kartagener's syndrome
7. Young's syndrome
8. GERDS

Pathogenesis:

This involves the following key elements:

1. Narrowing of natural sinus ostia
2. Ciliary apparatus dysfunction
3. Viscous secretions which cannot be easily expelled by the mucociliary apparatus

Factors predisposing to obstruction of natural sinus ostia:

Mucosal swelling:

1. URI
2. Allergy
3. Cystic fibrosis
4. Immune disorders
5. Tobacco smoke

Mechanical obstruction to ostia:

1. Choanal atresia
2. Deviated nasal septum
3. Nasal polypi
4. F.B.
5. Tumors
6. Bulla ethmoidalis (enlarged)

Local insults:

1. Facial trauma
2. Swiming & diving
3. Nasal intubation
4. Prolonged use of nasal decongestants

Obstruction to the natural ostium of paranasal sinuses cause a transient increase in pressure within the sinus cavity. Since the cavity is closed to atmospheric air, the depleting oxygen cannot be replaced, thus the pressure inside the sinus cavity is lesser than that of atmospheric pressure. This leads to introduction of bacteria from the nasal cavity into the paranasal sinuses when the patient attempts to clear the nasal cavity either by blowing / sniffing. Studies have shown that when a patient is blowing the nose about 1ml of fluid refluxes into the sinus cavity. While the pressure inside the sinus cavity continues to decrease, the mucous glands within the sinus cavity continue to secrete.This results in excess fluid accumulation within the sinus cavity. Combined effects of oxygen depletion and overloading of fluid within the sinus cavity the mucociliary mechanism fails. For it to regain its normal activity the obstruction to the sinus ostium should clear and the oxygen supply within the environment of the sinus cavity should improve.

Viral rhinitis cause disturbance to the mucociliary mechanism because of its effect on the cilia. These viruses destroy the ciliary mechanism of the mucosal lining impeding the drainage. For normal drainage mechanism to resume the process of regeneration of nasal mucosa should start after cessation of the viral infection. Nasal douching in these patients using alkaline solutions will dilute the secretions. This dilution reduces the tenacity of the secretions making clearing of mucoid material by the cilia rather easy.