What causes middle ear disease?

The overriding cause of middle ear disease is impairment of function of the eustachian tube. Effective function of the tube allows drainage of the middle ear and equalisation of pressure within the middle ear cavity. Blockage by mucus or inflammation of the membrane lining the tube prevents adequate drainage and results in retention of secretion within the middle ear cavity, which then becomes a medium for bacterial growth and proliferation. Reduced pressure within the middle ear cavity adds to the effect of encouraging bacterial spread through the eustachian tube.

Inflammation of the eustachian tube by common virus infections can result in dysfunction and thus encourages the conditions for secondary bacterial invasion.

In children the shape of the skull, the shorter length of the eustachian tube and different angle between the middle ear cavity and the throat predisposes to poor eustachian function. The immature immune system in childhood with the added frequency of upper respiratory infection also contributes to the increased incidence of middle ear infection in this age group.

A proportion of cases of acute otitis media will progress to the stage of chronic suppurative otitis media.

Other conditions may predispose to otitis media and chronic suppurative otitis media, particularly congenital abnormalities that alter the shape or structure of the skull and facial bones. Chronic suppurative otitis media is common in children with Down’s syndrome and in those with cleft palate.

Passive smoking has been implicated as a risk factor for increasing the incidence of otitis media in children.

Amended February 2009