Tympanometry is a method of measuring the compliance of the tympanic membrane and is an indirect measure of middle-ear pressure. There are 3 main types of tympanogram curves:
Tympanometry showing a type A curve is normal.
Tympanometry showing a type B (flat) curve with normal canal volume has a very high positive predictive value for otitis media with effusion (OME). Type B (flat) curve can also represent tympanic membrane perforation but the canal volume measurement will be high.
Tympanometry showing a type C curve is often suggestive of eustachian tube dysfunction. In some cases, OME can present with a type C tympanogram.