Ear infection, inner - Diagnosing middle ear infection

A middle ear infection (otitis media) can usually be diagnosed using an instrument called an otoscope.

An otoscope is a small handheld device that has a magnifying glass and a light source at the end. It is used to examine the ear. Using an otoscope, a doctor can detect certain signs that indicate fluid in the middle ear, which in turn may indicate an infection.

Signs of fluid in the middle ear can include the ear drum bulging, being an unusual colour (usually red or yellow) or having a cloudy appearance. In some cases, a hole may have developed in the eardrum (perforated ear drum) and there may be fluid in the ear canal (the tube between the outer ear and eardrum).

Some otoscopes can also be used to blow a small puff of air into the ear to check for any blockages in the middle ear, which could be a sign of an infection. If the Eustachian tube (the tube that connects the throat and middle ear) is clear, the eardrum will move slightly. If it is blocked, the eardrum will remain still.

Further tests

Further tests are normally only required if treatment is not working or complications develop. These tests will usually be carried out at your local ear, nose and throat (ENT) department.

Some of the tests that may be carried out are described below.

Tympanometry

Tympanometry is a test that measures how the ear drum reacts to changes in air pressure. A healthy ear drum should move easily if there is a change in air pressure. If your child's ear drum moves slowly or not at all, it usually suggests that there is fluid behind it.

During a tympanometry test, a probe is placed into your child's ear. The probe changes the air pressure at regular intervals while transmitting a sound into the ear. A measuring device is attached to the probe to record how the drum moves and how changes in air pressure affect this movement.

If the movement of the eardrum is restricted, it usually indicates that there is fluid in the middle ear.

Audiometry

Audiometry is a hearing test that uses a machine called an audiometer to produce sounds of different volume and frequency. This can help determine if your child has any hearing loss as a result of their condition.

During the test, your child listens to the sounds through headphones and they are asked to say when they can hear a sound and when they cannot.

Scans

On the very rare occasions where there is a possibility the infection has spread out of the middle ear and into the surrounding area, a computerised tomography (CT) scan or a magnetic resonance imaging (MRI) scan may be carried out.

A CT scan takes a series of X-rays and uses a computer to assemble the scans into a more detailed image, whereas an MRI scan uses strong magnetic fields and radio waves to produce images of the inside of the body.