A tympanogram graphically represents middle ear function. This simple, non-invasive test measures eardrum movement in response to air pressure changes. It helps healthcare professionals identify various middle ear issues, such as fluid buildup or problems with the Eustachian tube.
Understanding the Basics of a Tympanogram
A tympanogram displays the eardrum’s mobility by plotting two key measurements. The horizontal axis (X-axis) represents air pressure within the ear canal, measured in decaPascals (daPa). Pressure typically ranges from -400 to +200 daPa during the test. The vertical axis (Y-axis) indicates the eardrum’s compliance or mobility, measured in milliliters (ml) or cubic centimeters (cm³).
Compliance reflects how easily the eardrum moves. The highest point on the graph, known as the peak, shows the pressure at which the eardrum is most compliant. For adults, normal middle ear pressure falls within -100 to +100 daPa, while normal compliance ranges from 0.3 to 1.5 ml. Children’s normal pressure values can extend from +50 to -200 daPa, with compliance between 0.2 and 1.6 cm³.
Common Tympanogram Shapes and Their Meanings
Different patterns on a tympanogram indicate distinct middle ear conditions. The most common shape, Type A, resembles an inverted V or a mountain peak centered around 0 daPa. This characteristic shape signifies normal middle ear function, where the eardrum and the tiny bones behind it are moving as expected. A Type A tympanogram suggests a healthy middle ear system without fluid or pressure imbalances.
In contrast, a Type B tympanogram appears as a flat line with no discernible peak. This indicates minimal to no eardrum movement in response to pressure changes. It often suggests middle ear fluid or a perforated eardrum, preventing normal vibration. A Type C tympanogram shows a peak shifted significantly towards the negative pressure side of the graph. This shift suggests negative pressure within the middle ear space.
Beyond these primary types, subtypes offer more specific information. A Type As tympanogram, similar to Type A but with a shallower peak, indicates reduced compliance and a stiff middle ear system. Conversely, a Type Ad tympanogram features an excessively high and deep peak, suggesting hypermobility of the eardrum. Each of these shapes provides a visual clue about the underlying state of the middle ear.
What Abnormal Results Can Indicate
Abnormal tympanogram shapes point to specific ear conditions. A flat Type B tympanogram indicates middle ear fluid, known as otitis media with effusion. If the ear canal volume is unusually large with a Type B tracing, it can suggest a perforated eardrum.
A Type C tympanogram, with its peak shifted into the negative pressure range, suggests Eustachian tube dysfunction. This can occur with upper respiratory illnesses or during early/resolving ear infections, as the Eustachian tube struggles to equalize pressure. The shallow peak of a Type As tympanogram indicates a stiff middle ear system. Conditions like otosclerosis (hardened middle ear bones) or myringosclerosis (eardrum scarring) can cause this reduced mobility.
A Type Ad tympanogram, displaying an exaggeratedly deep peak, points to excessive eardrum flexibility. This increased mobility can be a sign of ossicular chain discontinuity (disconnected middle ear bones). It may also indicate a particularly thin or flaccid eardrum. These interpretations help healthcare providers narrow down potential causes of ear symptoms.
Next Steps After Tympanometry
After a tympanometry test, especially if results are abnormal, further action is recommended. Consult a healthcare professional (audiologist or ENT specialist) for a comprehensive diagnosis. A tympanogram provides valuable information, but it is one component of a complete ear health assessment.
Additional diagnostic tests, such as a full hearing evaluation (audiometry) or a physical examination of the ear, may be performed to confirm findings or identify other contributing factors. Depending on the underlying condition indicated by the tympanogram, follow-up actions can vary. These may include monitoring the ear over time, prescribing medication, or recommending procedures like ventilation tube insertion or surgical intervention.