Causes and Diagnoses

Causes and Diagnoses of Middle Ear Infection (Otitis Media)

The cause of middle ear infections can be either bacteria or viruses, often after an upper respiratory infection or allergy causes inflammation of the nose, sinuses and throat.

When you have a cold or flu, mucus and swelling can block the eustachian tubes, the tubes that run from the middle ear to the back of the throat, causing fluid to back up in the middle ear. When the infection spreads to the fluid in the middle ear, you have otitis media, or a middle ear infection.

Diagnosing middle ear infections

In most cases, your physician can use an otoscope, a lighted device for viewing the inside of the ears, to determine if there is a middle ear infection. The eardrum may be bulging and have dilated blood vessels or infected liquid may be visible through the eardrum.

If further tests are needed, they may include:

  • Pneumatic otoscope: This otoscope can release a puff of air against the eardrum to see if it moves. Infected fluid will prevent it from moving.
  • Tympanometry: This test seals off the eardrum and adjusts air pressure to measure how much the eardrum moves.
  • Acoustic reflectometry: This test measures how well the eardrum absorbs or reflects sound emitted from a device. A healthy eardrum should reflect most of the sound.
  • Tympanocentesis: This test drains fluid from the middle ear to be tested in a lab to help in determining what type of medication will clear up the infection.