Background to Chronic Suppurative Otitis Media

These are conditions that affect the middle ear and the special sense of hearing.

The ear facilitates the collection, amplification and transfer of sound waves via the auditory receptor organs to the brain where they are translated into the sounds we hear.

It consists of three main parts:

The outer ear

The outer ear is comprised of the external pinna or auricle (the visible ear) and the outer ear canal (external auditory meatus). The outer ear is separated from the middle ear by the eardrum (tympanic membrane). The pinna collects and concentrates sound waves that are transmitted through the ear canal to the eardrum where the first stage of amplification takes place.

The middle ear

The middle ear is a small cavity in the skull which is lined by epithelial membrane and which connects via the Eustachian tube to the back of the nose. It lies in close proximity to the air cells of the mastoid process of the skull. The eardrum is connected to a smaller inner membrane by three small bones (ossicles) that form a link across the middle ear cavity. The middle ear is vented frequently by the act of swallowing and the pressure within is maintained at normal atmospheric pressure via the eustachian tube.

The inner ear

The inner ear contains the sensory hearing organ (the cochlea) and the balance organ (vestibule and semicircular canals). The auditory nerve conveys impulses from the auditory sensors of the cochlea to the brain where they are perceived as sound. A separate vestibular nerve carries impulses that control balance.

The middle ear is a common site of infection, particularly in relation to acute upper respiratory tract infection from ‘colds’ and throat infection. The enclosed nature of the middle ear cavity makes it an ideal location for bacterial proliferation particularly when blockage of the Eustachian tube prevents the normal venting process. The epithelial lining of the middle ear also produces secretion that can collect and fill the ear cavity if the normal drainage of the Eustachian tube is disturbed.

Amended February 2009