Epidemiology and Prevalence The highest prevalence is found in children aged 1 to 5 years, but after the age of 8 years, OME is much less frequent. 1, 2, 3 It has been estimated that 50 to 80% of 4-year-olds in Europe and the United States have been affected by OME at least once, 2, 4 and one study in the United Kingdom showed 5% of 5-year-olds to have persistent (at least 3 months) bilateral hearing impairment due to OME. 5 There are two age peaks for OME, the first by 2 years of age and the second by 4 to 5 years of age, with a prevalence of approximately 16 to 20%. 4 During the former peak, the OME can usually be related to an episode of AOM, whereas during the latter, it more often cannot. 6, 7, 8 There is a strong seasonal variation with the disease being more common during the winter months, when the incidences of viral infections and AOM are higher. 9 Though no causal connection has been proven, numerous studies have shown an association between OME and allergic rhinitis. 10 OME can develop after an episode of AOM, after a viral infection, or without a previous infection. It is a multifactorial disease depending on endogenous factors (e.g., age, genetics, immunology, anatomy) as well as exogenous factors (e.g., siblings, day care, season). 11 There are different theories as to how and why the middle ear fluid develops: The ex vacuo theory suggests that a dysfunctional Eustachian tube causes a low pressure in the middle ear, which in turn causes the middle ear mucosa to produce fluid. 12, 13 The inflammation theory suggests that the inflammatory changes that occur in the middle ear mucosa during a viral or bacterial infection lead to upregulation of mucin-producing genes and thus to a production of fluid. 14, 15 The biofilm theory suggests that it is bacterial biofilms in the middle ear that cause an inflammatory response, leading to the production of fluid. A biofilm is a bacterial community enclosed in a polymeric matrix. Bacteria within a biofilm differ from their planktonic counterparts in many ways. For example, they are less susceptible to antibiotics and do not grow in conventional cultures, which would explain why OME fluids are often culture negative. 16 Biofilms found in the middle ears of children receiving tympanostomy tubes for OME have been shown to contain ordinary AOM pathogens, such as Streptococcus pneumoniae and Haemophilus influenzae. 17 The adenoid often harbors biofilms, which could possibly, as discussed later, explain the beneficial effect of adenoidectomy in persistent cases of OME. Several risk factors for OME have been identified ( ▶ Table 8.1). Risk factor Possible mechanism Proven risk factors Heredity Anatomy, genetic susceptibility, immunological factors Siblings Increased exposure to viral infections Day-care attendance Increased exposure to viral infections AOM Residual effusion, biofilm formation Down’s syndrome Impaired opening of Eustachian tube, increased susceptibility to infections Cleft palate Impaired opening of Eustachian tube Ciliary dysfunction Increased risk for infections due to reduced clearing of debris Unclear risk factors Short period of breast-feeding Increased susceptibility to infections, earlier onset of AOM Passive smoking Increased risk for AOM Allergy Inflammatory changes in mucous membranes Gastroesophageal reflux Inflammatory changes in mucous membranes Abbreviation: AOM, acute otitis media. In twin studies, heredity has clearly been shown to play a role in the development of OME. 18, 19 The same is true for having siblings and attending day care. 20 Both these factors lead to an increased mixing with other children, resulting in an increased probability of contracting upper airway infections. AOM is also a risk/etiological factor for developing OME. 21 Other factors that have been discussed but have not been proved to have a causal connection with OME are artificial feeding or a short duration of breast-feeding, parental smoking, 22, 23 allergy, 24 and gastroesophageal reflux. 25 Children with Down’s syndrome almost universally suffer from OME from an early age. This OME is of a chronic nature and often persists to an older age than in healthy children. Another group of children who almost always suffer from OME are those with a cleft palate. This malformation affects the muscles that are engaged in opening the Eustachian tube, leaving the children particularly prone to OME. The symptoms associated with OME are often mild. The main complaint is of hearing loss, but young children often present with vague symptoms such as irritability, bad sleep, and a loud voice. An impairment of receptive and expressive language might occur during preschool years. However, older children with previous chronic OME do not differ in linguistic skills from age-matched children without a history of OME. 26 Older children may complain of a sense of fullness in their ears. Ear pain can be present, but is usually much milder than in AOM. Balance problems were long considered not to be associated with OME, but it now seems clear that some children with OME do have a vestibular dysfunction, as measured by electronystagmography and posturography. This dysfunction has been shown to improve after treatment of the OME with ventilation tubes. 27 The mechanism behind the vestibular dysfunction is so far unknown, but the following three different explanations have been suggested: Ionic transfer through the round window alters the composition of inner ear fluids. The fluid in the middle ear causes serous/toxic labyrinthitis. The negative pressure in the middle ear is transferred to the inner ear, causing redisposition of inner ear fluids. The diagnosis of OME requires inspection of the tympanic membrane and evaluation of its mobility. Otomicroscopy combined with evaluation of the tympanic membrane mobility gives the most accurate diagnosis, whereas otoscopy alone is associated with overdiagnosis as well as underdiagnosis. 28 The tympanic membrane is typically retracted, slightly thicker than normal, opaque, and with clearly visible blood vessels. The fluid behind the tympanic membrane can be either serous (yellow and clear) or mucoid (opaque; “glue ear”). Sometimes, a gas-fluid level or air bubbles can be seen through the tympanic membrane ( ▶ Fig. 8.1). Due to the fluid in the middle ear, the mobility of the tympanic membrane is reduced, which can be demonstrated by pneumatic investigation or by tympanometry. Tympanometry is an objective way of measuring the mobility of the tympanic membrane by sending a sound wave into the external ear canal and then assessing the amount of movement this sound wave causes to the tympanic membrane and middle ear structures. The typical tympanometry result for a child with OME is a type B or C tympanogram. Whereas, a normal type A tympanogram shows a curve with a narrow peak of approximately 0 mm Hg, a type B curve is flat, indicating no or very little movement of the tympanic membrane, and a type C curve has a peak below 0 mm Hg, indicating a negative middle ear pressure ( ▶ Fig. 8.2, ▶ Fig. 8.3). Tympanometry alone cannot be relied upon to select children for surgery, 29 and the hearing level should be assessed whenever there is a suspicion of hearing loss or when the OME condition has persisted for more than 3 months. After the age of 4 years, most children are able to perform regular audiometry, but age-adapted audiometry can be done by specially trained audiologists even in very young children. Screening audiometry at 20 dB is commonly used in children to assess that they hear at sound levels sufficient for speech development. Otoacoustic emissions are typically absent in OME due to the reduced transmission of sound waves in the middle ear. The typical audiometry result in a child with OME is a conductive hearing loss of 10 to 40 dB, often most prominent in low frequencies ( ▶ Fig. 8.4). The reason for the hearing loss is that energy is lost when sound waves pass from air to fluid, and the mobility of the ossicular chain is reduced. A summary of diagnostic methods and associated clinical findings can be found in ▶ Table 8.2. Fig. 8.1 Otitis media with effusion. Fig. 8.2 Type B tympanogram. Fig. 8.3 Type C1 tympanogram. Fig. 8.4 Audiogram from a 5-year-old boy with a cleft palate and otitis media with effusion. He has a functioning ventilation tube in the left ear. Diagnostic method Typical finding Otomicroscopy Retracted tympanic membrane, fluid in the middle ear Pneumatic otomicroscopy Reduced/absent mobility Tympanometry Type B or C tympanogram Audiometry Conductive hearing loss of 10–40 dB, especially low frequencies Otoacoustic emissions Absent The spontaneous resolution rate for middle ear effusions is very high, with 40% of cases resolving within 7 days, and 75 to 90% within 4 weeks. 30 The longer the fluid has persisted, the less likely it is to resolve spontaneously. 31 The fluid per se is not harmful to the middle ear, and there is no evidence that OME in itself increases the risk for cholesteatoma; however, a dysfunctional Eustachian tube is common to both conditions. In the case of cholesteatoma, the dysfunction causes low middle ear pressure that results in a retraction pocket and subsequent accumulation of squamous epithelium. There is no evidence that temporary hearing loss due to OME should cause persistent damage to a child’s linguistic skills, 26 although there is some evidence of an association between recurrent otitis media with tympanostomy tubes, and behavioral and learning difficulties in later childhood. 32 Treatment strategies for OME could be conservative, pharmacological, or surgical. 33 Two things decide what action should be taken in an otherwise healthy child with OME: The duration of the disease. The degree of symptoms (i.e., hearing loss). Thus, it is the hearing loss rather than the OME per se that calls for action.
8.3 Etiology and Risk Factors
8.3.1 Etiology
8.3.2 Risk Factors
8.4 Clinical Presentation
8.5 Clinical Findings
8.6 Natural History
8.7 Management
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