Tympanometry: an objective pressure test of middle ear function & health

So, what exactly is tympanometry and why do we perform it so frequently in our audiology clinic? To answer this, let's break it down by first outlining the basic structure and function of the ear.

Your Auditory System

Your ear has three main parts: the outer ear (pinna and external ear canal leading to the ear drum), the middle ear (an air filled cavity behind your ear drum which contains your tiny middle ear bones), and the inner ear (the balance apparatus, cochlea and VIII nerve). See Figure 1. below. The middle ear helps to transfer sound vibrations over to the cochlea via the malleus, incus and stapes bones. These tiny ossicle bones are arranged in such a way that they actually amplify the sound energy as it passes through. We can see the malleus bone when we look inside a patient's ear - it connects directly to the ear drum and protrudes out (see Figure 2).

Figure 1. The auditory system (Credit to Meybodi, ResearchGate)

Figure 2. Otoscopic view of tympanic membrane (ear drum) with malleus bone clearly visible

For sound to be heard clearly, your eardrum needs to be able to vibrate freely. This occurs most easily when the pressure in your middle ear is equal to the pressure in your ear canal (i.e outside atmospheric pressure). Middle ear pressure equalisation is maintained via the eustachian tube which links the middle ear cavity to the back of the throat. Under normal circumstances, the eustachian tube remains closed. It opens up briefly when we yawn, swallow, chew or blow our nose. You can often tell this has happened because your ears may "pop".

Enter Tympanometry: A Gentle Check-Up for Your Middle Ear

Tympanometry is a test that helps us assess the working condition of your ear drum, middle ear and the eustachian tube. It does this by measuring your ear's biomechanical response to sound under changing pressure conditions: does your ear system admit the sound energy through [and at what pressure]. The equipment used to perform this test is called a tympanometer - usually a small handheld device with a probe that sits in the ear. Contained within the probe tip is a tiny speaker, air pump and microphone.

Hand held tympanometer in action

What Happens During the Test?

The test is brief and doesn't cause any pain. You might feel a gentle pressure sensation in your ear for a few seconds, you may also hear the low level tone.

Here's what you can expect:

1. A small, soft rubber tip is gently placed in your ear canal, creating a seal.

2. You might hear a soft tone and feel a slight change in air pressure – that's the tympanometer running the test.

3. The device measures how your eardrum moves as the air pressure in your ear canal changes.

4. The results are displayed on a graph called a tympanogram (Figure 3.), which the audiologist can then interpret.

   
   

What Does the Tympanogram Tell Us?

The shape of the tympanogram gives us valuable information about your ear drum and middle ear. The following information is gathered:

• Eardrum movement: Is it moving normally, or is it stiff or overly compliant?

• Middle ear pressure: Is the pressure in your middle ear normal, too negative, or too positive?

• Ear Canal Volume: Is the volume of your ear canal within an expected range or is it abnormally large (indicating a perforation).

  
  
  
  

  

  Figure 3. Tympanogram showing different graphical result outcomes.

  
  

Why is Tympanometry Important?

This simple test can help us to identify potential conductive ear problems such as

• fluid/congestion behind the ear drum (in the middle ear)

• a tiny ear drum perforation

• problems with the ossicle bones in the middle ear

• eustachian tube dysfunction, causing negative middle ear pressure

  
  

Tympanometry, together with ear examination, a thorough history and diagnostic audiometry can help to identify a variety of ear and hearing disorders.

In Summary

Tympanometry is a quick, painless test that gives us a valuable and objective insight into the health of your middle ear system. However, it is not a test of hearing threshold and is therefore used in partnership with other audiological tests such as audiometry and otoscopy. It is frequently used by audiologists to help diagnose/rule out middle ear disorders. It's use in paediatric populations is especially common given the high prevalence of glue ear in children.

Tympanometry testing is offered as part of our full hearing assessment appointments here at Ear Care Specialists, Nottingham. Additionally, we can add this test to any of our appointments.

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