Despite universal immunization of infants with pneumococcal vaccination, S pneumoniae still accounts for the most common bacterial isolate of AOM. Haemophilus influenzae type b (Hib) vaccination has had a minor impact on the incidence of AOM because the majority of cases of AOM are caused by non-typeable H influenzae.
The first stage of AOM is characterized by redness and inflammation. As pressure builds up in the middle ear, the tympanic membrane bulges out until a pressure necrosis forms. The formation of the pressure necrosis allows for the eardrum to perforate and release the mucopurulent material into the external ear canal. A dramatic relief of pain and resolution of the disease usually follow shortly after discharge. This whole process can take 12 hours in virulent infections or a few days in more mild infections.
- Symptoms – Children may be easily irritable with fever, earache, and a feeling of aural fullness due to inflammation. As the middle ear fills with pus, the pain increases and hearing decreases. Children with AOM may present with ear discharge (otorrhea) as the only symptom.
- Signs – Redness of tympanic membrane and swelling of upper portion (pars flaccida). The tympanic membrane may bulge laterally as the disease progresses to eventually form a pressure necrosis of the drum.
Younger children are more susceptible to AOM due to anatomical defects or immunologic deficiencies. Eustachian tube dysfunction is the most common anatomical abnormality causing ineffective clearing of bacteria from the middle ear and leading to increased susceptibility. Children with primary humoral immune deficiency (especially immunoglobulin G [IgG] subclasses) or HIV infection are prone to recurrent AOM as part of the spectrum of clinical manifestations.
Immunocompromised Patient Considerations: AOM may present with systemic sepsis and purulent ear discharge instead of more classic signs and symptoms.
Related topic: chronic otitis media