Synonyms: Purulent otitis media; Suppurative otitis media
Acute otitis media (AOM) is an infection of the middle ear space, defined by the presence of middle ear fluid, with rapid onset of signs and symptoms of acute inflammation, such as otalgia and fever. AOM is the illness which most commonly brings children to their physician (Bluestone and Klein 2007).
The middle ear space is a closed space located behind the tympanic membrane. Its only communication with the outside world is through the Eustachian tube, which connects the middle ear space to the nasopharynx. The normal middle ear space is filled with air, and the system is lined by respiratory mucosa. The anatomy of the Eustachian tube in infants and young children differs from that of adults, contributing to the increased incidence of AOM in this population.
In an infant, the Eustachian tube (ET) is shorter and lies at a more horizontal angle as compared to an adult. It reaches its adult length by the time a child is 7 years of age. The Eustachian tube equilibrates middle ear pressure and allows for drainage of middle ear. The ET is collapsed at rest, but intermittently opens through active movements of the jaw, such as yawning, or by actions such as swallowing, via contraction of the tensor veli palatini muscle. This allows for equilibration of pressure in the middle ear space with atmospheric pressure. Dysfunction of the ET can lead to AOM (Bluestone 2003).
The pathogenesis of AOM generally follows this sequence: An inciting factor, such as a viral upper respiratory infection or allergy, causes inflammation and edema of the respiratory mucosa of the nose, pharynx, and Eustachian tube. The Eustachian tube becomes obstructed, inhibiting drainage and pressure equilibration of the middle ear. Secretions accumulate in the middle ear, and the bacteria and viruses which colonize the respiratory tract enter and become trapped in the normally sterile middle ear. Microbial growth then occurs within the middle ear, causing a suppurative effusion, which leads to the signs and symptoms of an acute otitis media.
Risk factors for recurrent acute otitis media include male gender, genetic susceptibility, daycare attendance, pacifier use, lack of breastfeeding, and environmental pollution, including second hand tobacco smoke exposure. Peak incidence occurs between 6 and 18 months of age (Bluestone and Klein 2007).
Symptoms may range from mild to severe. Otalgia is the most common symptom of AOM, but in young children, the presentation may be vague and nonspecific, manifesting as irritability, poor sleep, poor appetite, and ear tugging. Other common symptoms include fever, nausea, vomiting, and diarrhea. If the tympanic membrane ruptures (or if there is a patent tympanostomy tube), purulent discharge may be seen. Since AOM is frequently triggered by upper respiratory infections, children with AOM will commonly exhibit signs such as congestion or rhinorrhea. Because of the fluid in the middle ear, AOM may be accompanied by a decrease in hearing acuity and, in some cases, balance problems or dizziness.
History and Physical Exam
Acute otitis media is a clinical diagnosis, and requires the presence of a middle ear effusion (MEE) and signs of infection and inflammation, with rapid onset. Physical exam with pneumatic otoscopy is the standard of care in making the diagnosis. Accurate diagnosis is critical, as it ensures appropriate therapy for those patients with AOM, while avoiding antibiotics in patients with otitis media with effusion, in whom antibiotics are unnecessary.
In acute otitis media, the tympanic membrane (TM) appears full or bulging, opaque, and with poor mobility. Erythema may or may not be present. Purulent otorrhea may be seen if the TM has ruptured. Pneumatic otoscopy is the primary tool used to evaluate the TM and the status of the middle ear.
In addition to a thorough exam of the ears, a complete head and neck examination is important, as it may identify conditions that predispose a child to acute otitis media. Facial features should be assessed as craniofacial abnormalities, such as Down Syndrome or Treacher-Collins Syndrome, are associated with an increased incidence of otitis media. The oral cavity should be inspected for either a bifid uvula or evidence of a submucous cleft palate. The patient’s voice may also provide additional insight – hypernasality indicates velopharyngeal insufficiency, and hyponasality may indicate either obstructing adenoids or nasal obstruction. Both can cause dysfunction of the Eustachian tube mechanism.
Tympanometry and Audiometry
Tympanometry can be a helpful adjunct in assessing middle ear status and TM function, particularly when otoscopic evaluation is either inconclusive or difficult to perform. A small probe which emits a tone is placed in the ear canal with an airtight seal. The tympanometer measures the acoustic energy of the reflected tone, and graphically represents the relationship of air pressure in the ear canal to the impedance of the tympanic membrane. A “flat” tympanogram with a small volume indicates a MEE, whereas a “flat” tympanogram with a large volume is indicative of a perforation or patent tympanostomy tube. It is important to note that tympanometry cannot make the diagnosis of AOM, but can only reveal the presence or absence of middle ear fluid. It cannot distinguish whether the fluid is infected or sterile. AOM, however, can be effectively ruled out with a normal tympanogram.
Fluid in the middle ear space can cause a mild to moderate conductive hearing loss, so abnormal audiometry can be seen in patients with AOM. However, again, this would only be indicative of the presence or absence of fluid, but would not give information regarding acuity or inflammation. Audiometry therefore does not contribute significantly to the diagnosis of AOM, nor does it help to distinguish AOM from OME.
As discussed above, it is important to distinguish acute otitis media from otitis media with effusion, in which no acute inflammation is present. Bullous myringitis must also be considered in the differential diagnosis. This entity represents an acute inflammation of the tympanic membrane itself. The TM is red and inflamed, with large bullae or blisters. This condition also causes intense otalgia and can cause otorrhea with rupture of the bullae; it is often, but not necessarily, associated with a severe acute otitis media. Other conditions, such as otitis externa, teething pain, tempormandibular joint problems, and pharyngitis, may present as otalgia. However, these should be easily distinguishable from AOM by history and physical examination.
Antibiotic prophylaxis, consisting of prolonged use of low-dose antimicrobials, has fallen out of favor, secondary to concerns regarding the development of resistant organisms, but can be effective and may be appropriate in select situations.
Environmental and lifestyle factors may be managed to decrease risk of acute otitis media. Promotion of breastfeeding in the first 6 months of life, as well as avoidance of passive tobacco smoke, bottle propping, and pacifier use may all decrease AOM risk. Daycare attendance is an often unavoidable risk factor for AOM. For children with significant atopy, allergy management may decrease the incidence of AOM.
The three most common pathogens responsible for AOM are Streptococcus pneumoniae, Haemophilus influenzae,andMoraxellacatarrhalis.Thepneumococcal conjugate and polysaccharide vaccines have shown efficacy in several large studies in decreasing the incidence of AOM (Black et al. 2000; Klein 2004). There is a vaccination for H. influenzae, type B; however, this subtype accounts foronly asmallpercentageof acute otitis media (Klein 2004). It should be noted, however, that althoughstudieshaveshownadecrease inepisodescaused by the specific serotypes covered by the pneumococcal conjugate vaccine (57%inone study), theoverall decrease in incidence of AOM episodes was only 6% and, in fact, a33%increase inAOMcaused by all other serotypes of S. pneumoniae was found (Eskola et al. 2001; Klein 2004). So it would appear that the vaccine may be changing the incidences of bacterial pathogens which cause AOM, but not the overall incidence. Respiratory viruses play an important role in the development of AOM; several studies have shown the efficacy of the influenza virus in decreasing influenza-associatedAOM(Heikkinen 2004).
Tympanostomy tubes have been shown to be effective in multiple clinical trials in decreasing episodes of recurrent acute otitis media (Casselbrant 2004). The tubes allow for equalization of pressure and drainage of the middle ear in the setting of poorly functioning Eustachian tubes.
In an effort to reduce antibiotic use and stem increasing bacterial resistance, observation without use of antibiotics is listed as an option for selected children with AOM in the guidelines published by the American Academy of Pediatrics and American Academy of Family Physicians in 2004 (AAP Subcommittee on AOM 2004). Children for whom this is an option are to be selected on the basis of diagnostic certainty, age, illness severity, and access to medical care.
Severe disease is defined as moderate to severe otalgia, fever with temperatures higher than 39C (102F) orally or 39.5C rectally, or a toxic-appearing child. Children younger than 6 months of age should be treated with antibiotics regardless of severity or diagnostic certainty. Children between 6 and 23 months, if the illness is nonsevere, may be observed if the diagnosis is uncertain, but if AOM is certain or severe, should be treated with antibiotics. Children 24 months or older may be watched if the diagnosis is uncertain or disease is nonsevere, but should be treated if AOM is severe.
According to the guidelines document published in 2004, high-dose amoxicillin is still the first line antibiotic treatment for nonsevere AOM, which provides coverage for S. pneumoniae, including resistant strains. For severe AOM the recommendation is amoxicillin and clavulanic acid, in order to broaden coverage to include H. influenzae and M. catarrhalis. Cephalosporins are considered first line treatment only for patients with penicillin allergies. Macrolides should be used in patients with allergies to both penicillins and cephalosporins. A 10-day treatment course is recommended, although symptoms should be reassessed after 2–3 days. Treatment failure is considered when there is persistence of symptoms after 48–72 h of antibiotic therapy; in this situation, antibiotic coverage should be broadened. If there is continued failure of response to antibiotics, a tympanocentesis should be considered to obtain middle ear fluid for culture, to help direct further antibiotic therapy.
The impact of decongestants and antihistamines on AOM therapy has been investigated, and there is no proven benefit.
Tympanocentesis is the insertion of a needle into the middle ear space to aspirate fluid and allow for drainage. Tympanocentesis can be both diagnostic and therapeutic: Cultures can be obtained to tailor antibiotic therapy, and the drainage of fluid can provide immediate relief of pressure and pain. However, it does not shorten the overall duration of effusion, nor does it lower the recurrence rate for AOM.
When medical treatments for recurrent AOM have failed, insertion of tympanostomy tubes may be considered. Recurrent AOM is usually defined as three or more episodes of AOM in 6 months or four or more episodes in 12 months. Several randomized controlled trials have found tympanostomy tube placement to be an effective treatment in preventing recurrent AOM (Rosenfeld and Bluestone 2003).
Adenoidectomy may be helpful in children who continue to have recurrent AOM after extrusion of tympanostomy tubes. Studies have shown the procedure to reduce OM incidence by 33% and to decrease the need for another set of tubes by 50% (Rosenfeld and Bluestone 2003). However, adenoidectomy is not recommended as an initial surgical procedure for children with recurrent AOM who have not previously had tubes, unless indicated for other reasons, such as nasal obstruction or chronic rhinosinusitis.
Studies evaluating the natural history of acute otitis media have shown that 61% of patients experience improvement of symptoms within 24 h without antibiotic therapy, and that 80% experience improvement by 48–72 h. No significant difference in suppurative complications of acute otitis media was noted in patients who received antibiotics as compared to those who did not (Rosenfeld and Kay 2003). Acute otitis media is the most common reason for antibiotic administration in children (AAP Subcommittee on AOM 2004). Fortunately, the incidence decreases after the first year of life, and AOM is much less common in children over the age of 6 years (Bluestone and Klein 2007).
Bluestone CD, Klein JO (2007) Otitis media in infants and children, 4th edn. BC Decker, Ontario
Bluestone CD (2003) Eustachian tube function and dysfunction. In: Rosenfeld RM, Bluestone CD (eds) Evidence based otitis media, 2nd edn. BC Decker, Ontario, pp 163–179
Casselbrant ML (2004) Ventilation tubes for recurrent acute otitis media. In: Alper CM, Bluestone CD et al (eds) Advanced therapy of otitis media. BC Decker, Ontario, pp 113–116
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Black S, Shinefield H, Fireman B et al (2000) Efficacy, safety and immunogenicity of heptavalent pneumococcal conjugate vaccine in children. Northern California Kaiser Permanente Vaccine Study Center Group. Pediatr Infect Dis J 19(3): 187–195
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