Tympanometry

What is Tympanometry?

Tympanometry is a simple and painless test that helps doctors check how well your middle ear is working. The middle ear is the part of the ear located behind the eardrum, and it plays a big role in hearing by transmitting sound vibrations to the inner ear. Tympanometry is commonly used to identify problems in this area, such as fluid buildup, eardrum perforations, or Eustachian tube dysfunction.

Tympanometry measures how your eardrum moves when air pressure changes in your ear canal. A healthy eardrum is flexible—it moves back and forth to transmit sound waves. If something affects the pressure in your middle ear or the mobility of the eardrum, it can interfere with hearing and cause discomfort. To learn more about how this test fits into a comprehensive hearing evaluation, check out our article on Understanding Audiograms.

How is Tympanometry Performed?

The test is quick and easy, usually taking just a few minutes. Here’s how it works:

1. Preparation: The doctor or audiologist will ask you to sit still and avoid talking or swallowing during the test, as these actions can affect the results.
   
   
2. Equipment: A small, soft probe is gently inserted into your ear canal. The probe creates a seal to prevent air from escaping.
   
   
3. Testing: The probe sends out a sound tone and adjusts the air pressure in your ear. As this happens, the device measures how your eardrum reacts to these changes, and records how much sound bounces back to the probe. 
   
   
4. Result Recording: The machine records the data and generates a tympanogram—a graph that shows how your eardrum moved in response to the pressure changes.

The process is entirely safe and painless. You may feel a slight pressure change in your ear, similar to what you experience during takeoff or landing in an airplane. The entire procedure is quick, typically taking only a few minutes for each ear. It is painless and suitable for patients of all ages, making it an essential tool in audiology and otolaryngology.

Why Do We Perform Tympanometry?

Tympanometry is performed for several reasons. It helps diagnose conditions that affect the middle ear and can contribute to hearing loss or discomfort.

• Hearing Loss: To determine if the cause is related to fluid, pressure, or structural problems in the middle ear.

• Ear Infections: To check for fluid buildup behind the eardrum, which is common in middle ear infections.

• Eustachian Tube Dysfunction: To assess whether the Eustachian tube, which helps equalize pressure in the ear, is working properly.

• Perforated Eardrum: To identify holes or tears in the eardrum.

• Chronic Ear Conditions: To monitor long-term issues, such as persistent fluid or scarring in the ear

• Patulous Eustachian Tube: A condition where the Eustachian tube stays abnormally open, causing symptoms like hearing your own voice too loudly (autophony) or your own breathing. Tympanometry can measure your eardrum moving with every nasal breath.

• Middle Ear Myoclonus: A rare condition involving involuntary contractions of the muscles in the middle ear, leading to clicking or thumping sounds. Tympanometry can help differentiate this from other ear disorders.

By identifying the underlying issues, tympanometry guides effective treatment plans and helps monitor the progress of ongoing treatments. It is particularly valuable for assessing the middle ear's health in children, who are more prone to ear infections.

Interpreting Tympanometry Results

Interpreting tympanometry results involves analyzing the tympanogram, a graph that displays the eardrum's movement in response to varying air pressures in the ear canal. Below is an example of what a normal tympanogram looks like. The shadowed box represents the range of normal for peak compliance and ear canal pressure (see explanations below).

The graph's shape and the values recorded can indicate different middle ear conditions. Understanding the axes and measurements on this graph is crucial for interpreting the results accurately.

1. X-Axis (horizontal axis): Ear Canal Air Pressure

• Representation: The x-axis on a tympanogram represents air pressure in the ear canal, measured in decapascals (daPa). The air pressure is adjusted with the test probe. 
  
  
• Normal Range: Typically, normal middle ear pressure ranges from -150 daPa to +50 daPa. A peak within this range suggests normal middle ear function.
  
  

2. Y-Axis (vertical axis): Compliance

• Representation: The y-axis represents compliance, which is the mobility of the eardrum and middle ear system, measured in milliliters (mL).
  
  
• Normal Range: For adults, normal compliance values range from 0.3 to 1.6 ml. Compliance peaks within this range indicate that the eardrum is moving properly in response to changes in air pressure.
  
  

3. Ear Canal Volume 

• Representation: Ear canal volume measures the space between the probe tip and the eardrum if intact or includes the middle ear space if there is a perforation.
  
  
• Normal Range: For adults, normal volumes ranges from 0.6 to 2.5 ml. Values outside this range can indicate issues such as a perforated eardrum (higher volume) or blockage (lower volume).

Types of Tympanometric Curves

Tympanometric curves, also known as tympanograms, are categorized into different types based on their shapes. These types include:

• Type A: This curve is characterized by a peak that occurs at normal pressure, indicating normal middle ear function.
  
  

• Type As (Shallow Curve):

  • The eardrum moves less than normal, but the middle ear pressure is normal.

  • Often indicates stiffness in the eardrum or middle ear bones, commonly caused by otosclerosis or scarring on the eardrum.

• Type Ad (Deep Curve):

  • The eardrum moves excessively, showing more mobility than normal.

  • Associated with a flaccid or overly flexible eardrum, often due to a healed perforation but with a very thin and flexible eardrum or disarticulation of the ossicles (tiny middle ear bones).

• Type B: This curve is flat or has no peak, which often suggests the presence of fluid in the middle ear or a perforated eardrum. The "volume" of the ear canal, another measure of tympanometry, will help distinguish between the two.
  
  

• Type C: This curve shows a peak at negative pressure, indicating eustachian tube dysfunction or the presence of negative pressure in the middle ear.

Understanding these curves is essential for accurately diagnosing and managing middle ear conditions. Each type of curve provides specific insights into the health of the middle ear, guiding appropriate treatment strategies.