Child/Adolescent Health

Tympanometric findings can indicate the probability of middle ear disease in children under age 3

Tympanometry can help clinicians diagnose middle ear effusion (MEE, fluid buildup) in young children, according to a new study. MEE is a component of middle ear infection and also often precedes, follows, or develops independently of middle ear infection. Traditionally, clinicians have diagnosed MEE using an otoscope, a magnifying lighted instrument that is inserted into the ear canal to visualize the ear drum. In infants and young children, however, visualizing the eardrum and interpreting the findings are often problematic.

In tympanometry, a multifunction probe is inserted into the ear canal. The instrument emits a sound signal, varies the air pressure in the canal, and records the level of sound reflected from the eardrum. As pressure is changed artificially from normal atmospheric pressure to either greater or lower pressure, the eardrum is stiffened, causing an increase in the amount of reflected sound. The tympanogram is the graphic tracing of changes in the level of reflected sound as the pressure is alternately raised and lowered. When the middle ear is normally filled with air, the changes in sound reflection are shown by corresponding changes in the graph. When the middle ear is filled with fluid, the eardrum is stiffened so that, irrespective of the changing pressure in the ear canal, the level of reflected sound remains more or less constant, and the tympanogram shows little change and appears "flat."

Previous clinical studies of tympanometry have mainly focused on pass/fail cutoffs for screening purposes. In this study, researchers compared tympanometric findings and otoscopic diagnoses by skilled otoscopists regarding the presence or absence of MEE in a diverse sample of 3,686 otherwise healthy children during their first 3 years of life.

For tympanograms generally, the lower their height and the flatter their appearance, the greater the probability of associated MEE; the probability was somewhat greater when peak pressure was negative rather than positive. For example, among children 6 months of age and older, effusion was diagnosed in only 2.7 percent of ears with tympanometric height of 0.6 mL or higher, but in 80.2 percent of ears with flat tympanograms. The findings for younger infants were similar, but less consistent. From their data, the researchers devised an algorithm for predicting the probability of MEE, depending on specific measured characteristics of the tympanogram. In children in both age groups, the tympanographic configurations most commonly encountered were associated with either a relatively low probability (less than 30 percent) or a relatively high probability (more than 70 percent) of the presence of MEE.

This algorithm performed equally well when applied to a separate group of children. This suggests that the researchers' approach to estimating the probability of MEE is generalizable to other unselected populations of young children. The study was supported in part by the Agency for Healthcare Research and Quality (HS07786).

More details are in "Tympanometric findings and the probability of middle-ear effusion in 3,686 infants and young children," by Clyde G. Smith, Jack L. Paradise, Diane L. Sabo, and others, in the July 2006 Pediatrics 118(1), pp. 1-13.

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