Tympanometry

Timothy C. Hain, MD Page last modified: December 31, 2007

Introduction

Tympanometry is a method of measuring the stiffness (or it's inverse, compliance) of the ear drum. It is a quick test that is part of most basic hearing assessments. A large amount of useful information about the middle ear can be gained in a short test. The tympanogram is a very simple procedure, that can be done by nearly anyone after about 5 minutes of training.

Methodology

Tympanometry involves measuring how much sound is reflected back while pressure is swept through the ear canal.

A typical tympanogram plots compliance for each ear (inverse stiffness), against pressure. If the eardrum is under no positive or negative pressure, it will have it's maximum compliance at 0. On the other hand, if it is under negative or positive pressure, the peak will move to the left or right.

Utility ot tympanometry:

Tympanometry is mainly useful to determine if there are problems with eardrum movement.

Perforation

One type is a hole in the eardrum (perforation). This can be spotted by noticing that the ear canal volume is excessive (ECV).

Flat tymp on the right side, in a person with perforation.

Stiff Ear Drums

Tympanometry also can detect abnormally stiff ear drums (often due to fluid behind them, scarring or otosclerosis), as well as abnormally floppy ear drums (called "hypercompliant"), usually due to excessive clearing of the ears.

On the test above, the left ear is flat. This indicates that the left ear drum is abnormally stiff.

Eustachian tube malfunction

A variant of tympanometry can be used to detect eustachian tube malfunction. Someone with a working eustachian tube should be able to move their negative or postive pressure tymp to 0 by swallowing or "popping" their ears.

Middle ear muscle testing

Finally, tympanometry can be used to detect abnormal contractions of the stapedius and tensor tympani muscles. This requires a machine that can run the tympanogram over 30 seconds, at a single frequency, looking for blips in the trace.

Rhythmic changes in impedance of the middle ear. Each bump was correlated with a high-pitched "tic" that can be heard from the outside, due to stapedius myoclonus.

An audio recording of his myoclonus can be heard by Clicking here