106 Suppurative Otitis Media—Acute
Otitis media is an inflammation of the mucosa of the middle ear cleft, the collective term for the eustachian tube, tympanic cavity, attic, aditus, antrum and mastoid air cells. The prefix, acute, sub-acute or chronic, relates to the duration of the condition with acute taken to imply a time period of up to 3 weeks, sub-acute as 3 weeks to 3 months, whereas chronic implies 3 months or more. Acute suppurative otitis media (ASOM) is an acute, pus-producing, usually bacterial, inflammatory process affecting the whole of the middle ear cleft.
ASOM is common and is most prevalent between the ages of 6 and 24 months with some series reporting at least one episode by the age of 2 years, in up to 80% of children. Boys are more prone than girls and the incidence falls steeply after the age of 5. There is evidence from the United States of a significant drop in incidence since the introduction of the polyvalent Streptococcus pneumoniae vaccine. Similar benefits have been found from the Hib vaccine (see Chapter 19, Epiglottis).
106.3 Associated Risk Factors
• Young age—often related to teething, which may increase saliva production and the risk of eustachian tube salivary reflux.
• Family history—more likely if one or both parents suffered similarly in childhood.
• Day care/nursery—the greater the number of children in the care facility, the greater the risk (if > 4 children).
• Breast-feeding—a minimum of 3 months of post-natal breast-feeding seems to provide some protection.
• Cigarette smoke exposure.
• Pacifier/dummy use—associated with a very slight increased risk—however, parenting benefits may outweigh the very slight risk of ASOM.
• Socioeconomic—correlation with deprivation, poverty and crowded housing.
• Race and ethnicity—some races seem to exhibit a particularly high risk of the condition—Native Americans, Canadian Inuits and Australian Aborigines.
Respiratory viruses and bacteria have been cultured from middle ear aspirations. The commonest bacteria are S. pneumoniae (40–50%), Haemophilus influenzae (30%) and Moraxella catarrhalis (10%). Group A streptococci are also found (2–10%). The commonest viruses are respiratory syncytial virus (RSV), adenovirus and influenza type A virus.
ASOM may occur as a primary infection, but more typically it will occur as a secondary infection after a viral upper respiratory tract infection (URTI). The URTI will lead to swelling and dysfunction of the eustachian tube. Infants have a short, wider and a more horizontally placed eustachian tube, which is more prone to dysfunction in the presence of nasopharyngeal inflammation. An effusion will follow and subsequent viral or bacterial infection can then arise. Pathogenic bacteria have been isolated from the nasopharynx in up to 97% of children with ASOM.
Bacteria can also enter the middle ear cleft via a perforated tympanic membrane or more rarely be blood-borne.