pathology

Last reviewed 01/2018

  • in otitis media there is an infection of the whole of the middle ear cleft, i.e. the Eustachian tube, tympanic cavity, attic, mastoid antrum and air cells.
  • colonization of nasopharynx with S. pneumoniae, H. influenzae, or M. catarrhalis predispose to otitis media (1)
  • this results in aspiration of infected inoculum through the eustachian tube into the middle ear space
  • aspiration is promoted by following mechanisms (1)
    • nasal obstruction that increases the positive pressure in the nasopharyngeal space
    • eustachian tube dysfunction that produces a negative pressure in the middle ear space
  • the mucous membrane is thus invaded by organisms which cause inflammation, oedema and exudate - pus is a later consequence of bacterial infection.
  • the Eustachian tube is closed by oedema and so prevents aeration and drainage
  • the drum bulges due to increased pressure from the pus
  • perforation of the tympanic membrane results, caused by necrosis. There is continual drainage of the ear until the infection resolves.

Reference: