A tympanogram is a medical test evaluating the middle ear and the mobility of the eardrum, or tympanic membrane. It measures how the eardrum responds to slight changes in air pressure. Receiving an “abnormal” result can be concerning, but it provides specific information about the middle ear system. This article clarifies what different abnormal results mean.
The Tympanogram Test Procedure
The tympanometry test is a quick process. An audiologist first looks into the ear canal with an otoscope to check for obstructions like significant earwax. After this check, a small probe with a soft tip is placed into the ear canal, creating an airtight seal. You may feel a slight pressure change, similar to ascending or descending in an airplane, and hear a low-pitched tone.
The device then varies the air pressure in the ear canal, causing the eardrum to move. The probe measures this movement and records the results on a graph called a tympanogram. The procedure lasts only a few seconds per ear and is not painful. Remaining still and avoiding talking or swallowing during the measurement period ensures an accurate reading.
Interpreting Abnormal Tympanogram Types
Tympanograms are categorized by the shape of the resulting graph. A normal result, or Type A, shows a distinct peak, indicating the eardrum and middle ear bones are moving correctly and middle ear pressure is normal. Abnormal results deviate from this shape and point to specific issues.
A Type B tympanogram appears as a flat line with little to no peak. This pattern means the eardrum is not moving, which suggests either fluid in the middle ear or a perforation in the eardrum. An audiologist can differentiate between these by looking at the ear canal volume measurement; a very large volume suggests a perforation.
A Type C result shows a peak shifted to the negative pressure side of the graph. This indicates the pressure in the middle ear is lower than in the ear canal, which pulls the eardrum inward. This is often caused by dysfunction of the Eustachian tube, the passageway connecting the throat to the middle ear.
A Type As tympanogram has a peak at the correct pressure but is much shallower than normal, suggesting the middle ear system has reduced mobility. In contrast, a Type Ad tympanogram shows an exceptionally high peak, indicating the system is overly flexible. This can point to a break in the chain of middle ear bones or a thinned eardrum.
Underlying Conditions Causing Abnormal Results
The different tympanogram types correspond to specific medical conditions affecting the middle ear. A Type B result is frequently caused by fluid in the middle ear, known as otitis media with effusion, especially in children. A hole in the eardrum can also produce a Type B result.
Eustachian tube dysfunction is the primary reason for a Type C result. When this tube fails to equalize air pressure properly, often due to allergies or a cold, it creates negative pressure in the middle ear.
A Type As result can be caused by conditions that stiffen the middle ear system. These include otosclerosis, which is abnormal bone growth in the middle ear, or myringosclerosis, which is scarring of the eardrum.
A Type Ad result is often caused by a break in the chain of middle ear bones, a condition called ossicular discontinuity. Head trauma is a potential cause of this condition.
Follow-Up and Management
An abnormal tympanogram is a diagnostic tool, not a final diagnosis. The results are interpreted alongside a physical examination and a hearing test (audiogram) to determine the cause of the issue. The next steps depend on these combined findings.
For some conditions, like fluid that may resolve on its own, a “watch-and-wait” approach with follow-up testing may be recommended. Other cases may prompt a referral to an Ear, Nose, and Throat (ENT) specialist. Treatment plans are tailored to the underlying cause and can range from medications, like nasal sprays for Eustachian tube function, to surgical procedures. For instance, chronic middle ear fluid might be addressed by inserting pressure equalization (PE) tubes. Discuss the results with a healthcare provider to understand the findings and recommended course of action.