Chronic rhinosinusitis without nasal polyps

The most difficult aspect of this disease is that it seems to be an endpoint (sinonasal inflammation) from many different causes, not a disease entity in and of itself. The main cause is thought to be anatomical obstruction of the osteomeatal complex (a common drainage pathway for several sinuses) leading to inadequate sinus drainage of mucus. Conditions that impair normal mucociliary clearance (the manner in which mucus is produced and characteristically moved out of the sinuses into the nasal cavity) are also implicated. They can be categorised into three overlapping groups:

• Genetic/physiological factors (e.g., cystic fibrosis/primary ciliary dyskinesia)

• Environmental factors (e.g., allergies, environmental pollutants, smoking)[5]Leland EM, Vohra V, Seal SM, et al. Environmental air pollution and chronic rhinosinusitis: a systematic review. Laryngoscope Investig Otolaryngol. 2022 Apr;7(2):349-60. https://www.doi.org/10.1002/lio2.774 http://www.ncbi.nlm.nih.gov/pubmed/35434330?tool=bestpractice.com

• Structural factors (e.g., severe mid-septal deviations).

The underlying aetiology of inflammation is unclear. Theories explaining the persistent inflammation include bacterial biofilms, mucosal response to fungal elements, or staphylococcal superantigens.[3]Orlandi RR, Kingdom TT, Smith TL, et al. International consensus statement on allergy and rhinology: rhinosinusitis 2021. Int Forum Allergy Rhinol. 2021 Mar;11(3):213-739. https://www.doi.org/10.1002/alr.22741 http://www.ncbi.nlm.nih.gov/pubmed/33236525?tool=bestpractice.com ​​ Microbiological aspects of acute and chronic rhinosinusitis are significantly different.[6]Drago L, Pignataro L, Torretta S. Microbiological aspects of acute and chronic pediatric rhinosinusitis. J Clin Med. 2019 Jan 28;8(2). https://www.doi.org/10.3390/jcm8020149 http://www.ncbi.nlm.nih.gov/pubmed/30696073?tool=bestpractice.com ​ In one series of 94 endoscopically guided ethmoid sinus cultures from 50 adults with chronic ethmoid sinusitis, the recovered organisms included Staphylococcus aureus (50%), gram-negative rods (20%), Haemophilus influenzae (4%), group A streptococcus (4%), Streptococcus pneumoniae (2%), and Corynebacterium diphtheriae (1%).[7]Doyle PW, Woodham JD. Evaluation of the microbiology of chronic ethmoid sinusitis. J Clin Microbiol. 1991 Nov;29(11):2396-400. http://www.ncbi.nlm.nih.gov/pubmed/1774242?tool=bestpractice.com Studies have shown a higher incidence of anaerobic and polymicrobial infections in patients with chronic rhinosinusitis compared with those with acute disease.[8]Shapiro ED, Milmoe GJ, Wald ER, et al. Bacteriology of the maxillary sinuses in patients with cystic fibrosis. J Infect Dis. 1982 Nov;146(5):589-93. http://www.ncbi.nlm.nih.gov/pubmed/6813383?tool=bestpractice.com

Osteomeatal complex (OMC) obstruction is thought to be the central issue in most cases. The current theory is that underlying factors (e.g., allergy, viral infections, or air pollutants) induce local inflammation in sinonasal mucosa causing mucosal surface swelling in the narrow OMC channels. This causes sinus outflow tract obstruction and impairs mucus clearance by respiratory cilia. Sinus secretions pool and thicken, and may have microorganisms. The exact role of microorganisms in chronic inflammation remains controversial. Patients with immunodeficiency may develop this condition from persistent infections. Anatomical abnormalities blocking the OMC (e.g., septal deviation, concha bullosa, abnormal bony cells, foreign bodies, craniofacial abnormalities) and scarring/trauma may play a role.