Aetiology

​Patient and environmental factors can increase a child’s risk of otitis media with effusion (OME). OME can occur shortly after acute otitis media or after a respiratory tract infection.[2]​ Preceding viral or bacterial infection is a risk factor for OME. Infection may cause inflammation of the nasopharynx and Eustachian tube.[10]​ Mucosal inflammation secondary to infection can lead to obstruction and dysfunction of the Eustachian tubes, thereby leading to fluid accumulation within the middle ear.[11]

The Eustachian tubes play an important role in maintaining the health and function of the middle ears. Specifically, the Eustachian tubes assist in pressure equalisation of the middle ear and mucociliary clearance.[11] Dysfunction of the Eustachian tubes can therefore increase the risk of OME.[12]​ In infants the Eustachian tube is shorter and more horizontal than in older children and adults, and is therefore less effective at clearing the contents of the middle ear.[13][14]​ Children have been found to be less able than adults to equalise negative middle ear pressure.[15]

Genes for immunoglobulin markers, cytokines, and mucin have been linked to an increased risk of OME.[16]​ Monozygotic twins have higher rates of concordant histories of otitis media compared with dizygotic twins.[17][18][19]

There is an association between allergy and OME, but there is currently no evidence of causation.[1]​ Children with OME have been found to have an increased prevalence of allergic rhinitis.[20]​ This may be secondary to allergy-related mucosal swelling and increased mucus production.[21]​ Data suggest that age is an effect modifier of the association between allergic rhinitis and OME. Specifically, there is a significant association between allergic rhinitis and OME in children aged 6 years and older. The same association is not found in children younger than 6 years.[22]

Tobacco smoking and exposure to second-hand tobacco smoke may increase the risk of OME. Proposed mechanisms include impaired mucociliary clearance of the Eustachian tubes and smoke-induced nasopharyngeal lymphoid hyperplasia.[23][24]​ In children, exposure to second-hand smoke is associated with higher odds of OME (and acute otitis media).​[25]

Chronic rhinosinusitis with and without nasal polyposis, paranasal sinus disease, and adenoid enlargement have all been associated with an increased risk of OME.[24][26][2]​​​[27]​ Adults presenting with OME, particularly if unilateral and persistent, should be assessed for nasopharyngeal carcinoma via endoscopy.[28]​ The rate of nasopharyngeal carcinoma as the cause of adult-onset OME has been found to be approximately 5% to 6%.[28][24] The mechanism of OME may be due to Eustachian tube orifice obstruction or Eustachian tube dysfunction secondary to infiltration of tubal musculature.[29]

Symptoms of gastro-oesophageal reflux disease (GORD) have been found more frequently in people with OME compared to those without OME.[30]​ Pepsin and Helicobacter pylori have also been found in middle ear effusions.[31][1]​ While there is an association, a causal relationship has not been established.[1] Furthermore, treating GORD has not been associated with an increased rate of resolution of OME.[32]

Daycare attendance is a risk factor for recurrent acute otitis media and OME.[33][10]​ This is likely related to increased exposure to viral pathogens, which cause upper respiratory tract infections. Low socioeconomic status has been associated with OME.[10] Male sex has been associated with an increased incidence of acute otitis media and persistent OME.[10][34]

Pathophysiology

​The pathophysiology of OME is multi-factorial, with genetic factors and endogenous irritants (e.g., smoking, pollution, allergy, and reflux from the Eustachian tube being proposed as contributing to inflammation of the middle ear.[16][23][24][21][35]

The middle ear comprises the middle ear cavity and the ossicles (the malleus, incus, and stapes), which are attached to the tympanic membrane. The conductive hearing loss associated with OME is caused by impaired transduction of sound waves in the middle ear due to the presence of fluid in the middle ear.[36]

In adults, a nasopharyngeal carcinoma may be the cause in approximately 5% to 6% of patients with OME.[28][24] The mechanism of OME in this scenario may be due to Eustachian tube orifice obstruction or Eustachian tube dysfunction secondary to infiltration of tubal musculature.[29]

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