How is chronic otitis media with effusion (ome) differentiated from acute otitis media (aom)

Definitions

Acute otitis media (AOM) is the most common infection diagnosed in the outpatient setting, with U.S. healthcare costs greater than $5 billion annually. AOM is defined as an infection of the middle-ear space with rapid onset of signs and symptoms (<48 hours) of inflammation, such as otalgia, fever, irritability, anorexia, vomiting, and otorrhea. Otoscopic findings include a yellow–red exudate behind the tympanic membrane (TM). The TM is often bulging, with loss of ossicular landmarks and decreased mobility of the TM. Unresponsive AOM is characterized by clinical signs and symptoms associated with otoscopic findings of inflammation that continue beyond 48 to 72 hours of therapy with an appropriate antimicrobial. Unresponsive AOM suggests continued active infection with persistence of the bacterial pathogen in the middle-ear space. However, prolonged symptoms associated with a concomitant viral infection may be misdiagnosed as an unresponsive infection when the AOM is actually resolving. Clinical judgment is required, with attention to the patient’s overall clinical status, if antibiotic use is to be limited appropriately.

Acute Otitis Media

Acute otitis media is the term used to describe acute infection and inflammation of the middle ear. Associated inflammation and edema of the eustachian tube mucosa appear to play key roles in the pathogenesis by impeding drainage of the middle ear fluid. In some children, anatomic or chronic physiologic abnormalities of the eustachian tube predispose to infection. The problem is commonly seen in conjunction with an acute upper respiratory tract infection, and its onset is often heralded by a secondary temperature spike one to several days after the onset of respiratory symptoms. The major offending organisms are bacterial respiratory pathogens. The most commonly isolated organisms and their relative frequency, shown inTable 24.1, demonstrate the rise of penicillin-resistantStreptococcus pneumoniae. NontypableHaemophilus influenzae is found to be causative in 70% to 75% of these cases. Increasing rates of β-lactamase positivity in these organisms, as well as the rising incidence of penicillin-non-susceptibleS. pneumoniae, has necessitated the use of high-dose amoxicillin and/or greater use of β-lactamase–resistant antibiotic regimens whenever this scenario is seen. Sulfa drugs may also be useful for therapy of community-acquired methicillin-resistantStaphylococcus aureus, which is becoming increasingly common.

In acute otitis media, the classic findings on inspection of the tympanic membrane are erythema and injection; bulging that obscures the malleus; thickening, often with a grayish-white or yellow hue, reflecting a purulent effusion; and reduced mobility (Fig. 24.24A). However, crying produces erythema of the eardrum, and thus tympanic erythema in a crying child is of little diagnostic value. The patient is usually febrile and, if old enough, typically complains of otalgia. However, in many cases, this “textbook picture” is not seen. This is probably due in part to time of presentation, the virulence of the particular pathogen, and host factors.

Accuracy in diagnosis necessitates meticulous inspection during otoscopy and knowledge of the various modes of presentation. The challenge to clinicians is that children may present at various points during time course of the infection. Children prior to a full infection may have fever of a few hours' duration and otalgia (or if very young, fever and irritability) yet have no abnormality on otoscopy. If reexamined the next day, many of these patients have clear evidence of acute otitis media. Some have erythema and bubbles or air/fluid or air/pus levels (a result of venting by the eustachian tube) without bulging and with nearly normal mobility of the eardrum (seeFig. 24.24B). In still other cases, the drum may be full and poorly mobile with cloudy fluid behind it but with minimal erythema (seeFig. 24.24C).

The recent guidelines from the American Academy of Pediatrics (AAP) and the American Academy of Family Practice emphasize the importance of visualizing the position of the tympanic membrane. Acute otitis media needs to be differentiated from otitis media with effusion. Although both diagnoses comprise a segment on the continuum of disease and inflammation, treatment implications vary. Otitis media with effusion does not represent an acute infection, and antibiotics should be avoided. Similarly, clinicians should not diagnose acute otitis media without the presence of a middle ear effusion, based on otoscopy or tympanometry. Moderate to severe bulging of the tympanic membrane or new onset of otorrhea not from otitis externa is diagnostic of the acute otitis media. The diagnosis may also be made with mild bulging and recent symptoms or redness of the tympanic membrane.

Acute Otitis Media

AOM is among the most common infectious diseases in young children. Almost all children experience at least one AOM episode during their early years2; by 6 months of age, 20% of children have had two or more AOM episodes and by 3 years of age 50% have had three or more episodes.29,30

The average global AOM incidence rate is estimated at 10.8 new episodes per 100 people per year.2 This rate ranges from an average of 3.6 in central Europe to an average of 43.4 for sub-Saharan West Africa and central Africa, reflecting that the burden of AOM varies with economic status (Fig. 15.3).2 Global AOM incidence rates are highest in children aged 1 to 4 years (61 new episodes per 100 children per year).2

Acute Otitis Media

Pathogenic bacteria can be isolated by standard culture techniques from middle-ear fluid in most documented AOM cases. Three pathogens predominate in AOM:Streptococcus pneumoniae (seeChapter 209), nontypeableHaemophilus influenzae (seeChapter 221), andMoraxella catarrhalis (seeChapter 223). The overall incidence of these organisms has changed with the use of the conjugate pneumococcal vaccine. Widespread use of the expanded serotype coverage 13-valent as compared with the 7-valent pneumococcal conjugate vaccine has further reduced the prevalence ofS. pneumoniae as a cause of AOM, particularly the virulent 19A serotype. Less common pathogens include group A streptococcus (seeChapter 210),Staphylococcus aureus (seeChapter 208.1), and Gram-negative organisms. Gram-negative organisms andS. aureus are found most commonly in neonates and very young infants who are hospitalized; in outpatient settings, the distribution of pathogens in these young infants is similar to that in older infants. Molecular techniques to identify nonculturable bacterial pathogens have suggested the importance of other bacterial species such asAlloiococcus otitidis.

Evidence of respiratory viruses also may be found in middle-ear exudates of children with AOM, either alone or, more commonly, in association with pathogenic bacteria. Of these viruses, rhinovirus and respiratory syncytial virus are found most often. AOM is a known complication of bronchiolitis; middle-ear aspirates in children with bronchiolitis regularly contain bacterial pathogens, suggesting that respiratory syncytial virus is rarely, if ever, the sole cause of their AOM. Using more precise measures of viable bacteria than standard culture techniques, such as polymerase chain reaction assays, a much higher rate of bacterial pathogens can be demonstrated. It remains uncertain whether viruses alone can cause AOM, or whether their role is limited to setting the stage for bacterial invasion, and perhaps also to amplifying the inflammatory process and interfering with resolution of the bacterial infection. Viral pathogens have a negative impact on eustachian tube function, can impair local immune function and increase bacterial adherence, and can change the pharmacokinetic dynamics, reducing the efficacy of antimicrobial medications.

Acute Otitis Media with Effusion

Acute OME occurs most frequently in infants. Redness with or without bulging of the tympanic membrane, fever, irritability, and pain are the hallmark signs and symptoms. An older child with acute OME has a red tympanic membrane and middle ear effusion, but may not have pain or fever. The middle ear effusion is generally purulent. Casselbrant and associates10 reported a cumulative incidence of acute OME of 43% in a study of 198 newborns followed monthly until the age of 2 years. In the Greater Boston Otitis Media Study Group, infants had an average of 1.2 and 1.1 episodes per year, with 46% of children having had 3 or more episodes by the age of 3 years.11

Recurrent AOM refers to frequent bouts of AOM. The child most likely has intercurrent, persistent (chronic) OME. The effusion becomes infected, and the child develops AOM. Recurrent AOM is an indication for surgical intervention (see later).

Epidemiology

Although AOM is a relatively minor infection, it continues to have a significant impact on health care providers, parents, and the economy. AOM is the most frequently diagnosed illness among children and most common reason for antibiotic prescriptions. Young children are at the greatest risk for development of AOM. By the end of the first year of life, 50% of children will have suffered from at least one episode of AOM. That number increases to at least 70% by age 3 years and to more than 90% by age 7 years. Between 1982 and 1990, office visits for AOM were on the rise, increasing by almost 60% to approximately 25 million visits per year. More recent estimates from 2000 show a decline to 16 million office visits for AOM each year. Despite this decline, AOM still accounts for an estimated $2 to $5 billion in direct health care costs with an additional $1 billion in indirect costs. Furthermore, some studies have suggested an increase in the rate of early onset AOM (younger than 12 months of age at first diagnosis), and an increase in the number of children suffering from repeated episodes of AOM (more than three episodes by age 6 years).

Pathogenesis

AOM usually is considered to be a bacterial infection because bacterial otopathogens are isolated from middle ear culture in 70% of cases.3 AOM usually is a coinfection, with a viral upper respiratory tract infection (URI) enhancing the ability of bacterial otopathogens from the nasopharynx to gain access to the middle ear. Respiratory tract viruses alone occasionally cause AOM (2% to 20%) as proved by tympanocentesis.4 Eustachian tube dysfunction (i.e., tympanometric measurement of negative pressure) occurs in 75% of children with a viral URI and is a major contributing factor to the development of bacterial AOM.5 Influenza A infection can suppress neutrophil function6 and macrophage recruitment, and it likely contributes to the high attack rate for AOM observed among children with influenza A infection.7 Viral URI in animal models and observed in children enhances the frequency and density of nasopharyngeal colonization with otopathogens.8–10 Fig. 29.1 synthesizes the important pathophysiologic mechanisms.

EPIDEMIOLOGY

Acute otitis media (AOM) is common in young children and is associated with upper respiratory tract infection.1 The immaturity of the immune system plays a major role in its development but other risk factors – such as male sex, lower age (peak age of incidence is between 6 and 18 months),2 family history and above all the early entry into day care3 – are well known. The frequency of AOM increases with allergy and passive smoking that modify the ciliated respiratory membrane. Esophageal reflux can also favor AOM by way of throat inflammation.4

What Not To Do:

Discussion

AOM is primarily a disease of children younger than 3 years of age, although AOM is not totally unexpected up to age 5. Age-related factors that directly cause AOM are the result of immature anatomy and immature immune systems coupled with excessive exposure to pathogens. The main reasons for AOM are not bacterial, although bacteria are the final ingredients. Bacterial AOM pathogens merely take advantage of the main cause of AOM (i.e., dysfunction of the middle ear–flushing mechanism, the eustachian tube). Eustachian tubes are dysfunctional to some degree in every young child but gradually become fully functional by age 5.

Most AOM is caused by a viral infection, and most patients do well regardless of the antibiotic chosen. Some 50% to 80% of cases of AOM will spontaneously clear without antibiotics. (Older children with infrequent AOM are more likely to experience spontaneous clearing, whereas more severe AOM or AOM occurring soon after a previous episode is less likely to clear spontaneously.) Because AOM usually occurs secondary to acute viral infections (respiratory syncytial virus, influenza, and rhinovirus), rapid initiation of antibiotic treatment may result in eradication or reduction of the susceptible organisms in both the middle-ear fluid and the nasopharynx, permitting the overgrowth of the nasopharyngeal flora organisms that are not susceptible to the drug. Because the predisposing condition (the viral infection causing ciliary and mucosal damage, plus overproduction of secretions) may still be present, a new infection of the middle ear may then take place with the newly selected resistant pathogen. Despite the increase in antimicrobial resistance of community-acquired Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis and the plethora of alternative antibiotics available, amoxicillin remains the drug of choice in the treatment of uncomplicated AOM.

Bullous myringitis is the result of acute bacterial infection of the tympanic membrane producing intraepithelial fluid collections. These patients present with bullae on the TM and can have severe pain. They respond well to anesthetic otic drops (Auralgan), oral antibiotics, corticosteroids, and analgesia.