What is Tympanometry?
Tympanometry is a diagnostic test used in audiology to evaluate the functioning of the middle ear. A tympanometer measures the eardrum’s movement and characteristics in response to air pressure changes, helping identify potential issues within the middle ear space. This test is useful in diagnosing conditions such as eustachian tube dysfunction (ETD), fluid accumulation, eardrum perforations, and abnormalities in the ossicular bones.
This page provides an in-depth look at tympanometry, detailing when and why the test is performed, the procedure and equipment used, and how to interpret the results. Understanding tympanometry’s role in comprehensive hearing assessments highlights its importance in diagnosing and managing middle ear problems.
When and Why Tympanometry is Performed
Diagnostic Contexts
Tympanometry is used in various diagnostic contexts, providing insights into the function and health of the middle ear. Whether part of a comprehensive tinnitus assessment, ACC or Veterans Affairs audiograms, or occasionally included in free hearing screenings, tympanometry can help pinpoint underlying middle ear issues.
- Comprehensive Tinnitus Assessment and Full Diagnostic Hearing Test
Tympanometry is a key component of a thorough tinnitus evaluation. It provides essential information about the middle ear’s condition and helps determine whether tinnitus is related to middle ear issues. - ACC (Accident Compensation Corporation) and Veterans Affairs Audiograms
This test is included in ACC and Veterans Affairs audiograms to help differentiate between sensorineural hearing loss and problems originating in the middle ear. It ensures that hearing loss is correctly attributed to noise exposure or middle ear conditions. - Occasionally Required in Free Hearing Screenings
Tympanometry can be added to free hearing tests when middle-ear hearing loss is found to diagnose specific middle-ear problems. It helps pinpoint issues such as fluid accumulation, ETD, eardrum perforations, or abnormalities in the ossicular chain.
Key Middle Ear Issues Identified
Tympanometry is occasionally used to help identify specific issues within the middle ear that may affect hearing. These problems, though not common in every assessment, can significantly impact hearing function when present. Middle ear issues that tympanometry can help detect include:
- Eustachian tube dysfunction (ETD)
- Fluid accumulation
- Eardrum perforations
- Abnormalities in the ossicular chain
- These can include stiffness or disconnection of the bones in the middle ear.
Procedure and Equipment
A tympanometer is a specialised device used to measure the functioning of the middle ear. There are two main types: large desk-based machines and handheld units.
Desk-based Tympanometer
These machines are typically used in clinical settings and offer comprehensive features. They provide detailed graphs and numerical data that can be analysed on a larger screen.
Handheld Tympanometer
These portable and convenient units are ideal for on-the-go assessments or smaller clinics. While they may have fewer features than desk-based machines, they still provide accurate and reliable results.
Tympanometry Procedure
- Pre-test Inspection for earwax
Before starting the test, the ear canal is checked for earwax blockage. This ensures that the test results are accurate and uninfluenced by obstructions. - Placement of a rubber tip in the ear canal
A soft rubber tip is gently inserted into the ear canal. This tip forms an airtight seal, which is necessary for the test to be effective. - Client experience
During the test, the client does not need to do anything. They will feel slight pressure changes in the ear and may hear a humming sound. This is normal and part of the process as the tympanometer measures the ear’s response to these pressure changes. - Reading and interpreting results on the machine
The tympanometer displays the results on its screen, showing a graph and numerical values for:
- Ear canal volume
- Indicates the size of the ear canal.
- Middle ear pressure
- Measures the ear canal air pressure which is equal to the middle ear air pressure, helping to identify issues like ETD.
- Compliance
- Shows the eardrum and middle ear bones’ flexibility, indicating conditions such as stiffness or floppiness in the middle ear structures.
- Ear canal volume
Interpreting Tympanometry Results
- The tympanometer produces a graph known as a tympanogram and numerical data to represent the middle ear’s condition measurements. This graph typically displays the relationship between air pressure in the ear canal and the mobility of the eardrum (compliance).
Significance of Various Measurements
- Ear Canal Volume
- What It Measures: Ear canal volume is usually expressed in cubic centimetres (cc).
- Significance: An average ear canal volume indicates an unobstructed ear canal and an intact eardrum. Abnormally high volumes can suggest a perforated eardrum, while shallow volumes might indicate an obstruction such as ear wax.
- Middle Ear Pressure
- What It Measures: The air pressure in the middle ear space, typically measured in daPa (decaPascals).
- Significance: Normal middle ear pressure falls within a specific range that indicates proper eustachian tube function. Negative pressure can suggest ETD, while positive pressure might indicate recent Valsalva equalisation (blowing into a pinched closed nose).
- Compliance of the middle ear system
- What It Measures: The flexibility or stiffness of the eardrum and ossicles, measured in cubic centimetres (cc) or millilitres (ml).
- Significance:
- Normal Compliance: Indicates a healthy and responsive middle ear system.
- Low Compliance: Suggests a stiff middle ear, possibly due to fluid, a thickened eardrum, or ossicular chain fixation.
- High Compliance: Indicates a very flexible or “floppy” eardrum, possibly due to a disarticulated ossicular chain or a very thin eardrum.
Understanding these measurements helps audiologists diagnose specific middle ear conditions, aiding in developing appropriate treatment plans.
Role in Comprehensive Hearing Assessments
How Tympanometry Complements Pure Tone Audiometry
Pure tone audiometry is a fundamental hearing test that measures a person’s ability to hear sounds at different pitches and volumes. Tympanometry complements this by providing additional information about the middle ear’s status. While pure tone audiometry assesses overall hearing ability, tympanometry focuses specifically on the functionality of the middle ear, which can significantly affect hearing.
Bone Conduction and Air Conduction Results
In pure tone audiometry, there are two key types of measurements: air conduction and bone conduction.
- Air Conduction: This pathway tests the entire hearing system, including the outer, middle, and inner ear.
- Bone Conduction: This pathway bypasses the outer and middle ear, directly stimulating the inner ear through vibrations.
If there is a significant difference between air conduction and bone conduction results, it suggests that there might be a problem in the middle ear (conductive hearing loss). Tympanometry helps to confirm this by providing specific data on middle ear function, thus identifying whether the issue lies in the middle ear or if the hearing loss is sensorineural (originating from the inner ear or auditory nerve).
Specific Middle Ear Pathologies
Tympanometry is particularly useful in diagnosing the following middle ear conditions:
- Eustachian tube dysfunction (ETD)
Tympanometry can identify abnormal pressure in the middle ear, which indicates ETD. This dysfunction can lead to discomfort, hearing loss, and a sensation of fullness in the ear. - Fluid in the middle ear (otitis media with effusion)
The presence of fluid in the middle ear affects the mobility of the eardrum, resulting in a flat tympanogram with reduced compliance. This condition is common in children and can lead to temporary hearing loss if untreated. - Eardrum Perforations
A perforated eardrum can be detected by measuring ear canal volume. A significantly higher than normal volume suggests a hole in the eardrum. - Ossicular Chain Abnormalities
Conditions such as ossicular chain fixation or disarticulation can affect middle ear compliance. Tympanometry helps to diagnose these issues by showing abnormally high or low compliance, indicating that the ossicles are either too stiff or too flexible.
Conclusion
Tympanometry plays a vital role in diagnosing and understanding middle ear health. By measuring how the eardrum responds to changes in air pressure, this test helps identify conditions such as Eustachian Tube Dysfunction, fluid accumulation, eardrum perforations, and ossicular chain abnormalities. Its ability to provide detailed information about middle ear function makes it an essential component of comprehensive hearing assessments, complementing other tests like pure tone audiometry.
Tympanometry offers valuable insights for individuals experiencing hearing issues that can lead to accurate diagnoses and effective treatment plans. If you are experiencing symptoms such as hearing loss, ear discomfort, or a sensation of fullness in the ears, it is essential to consult with a hearing professional. Early diagnosis and intervention can significantly improve your hearing health and overall quality of life.
