Developmental changes in tympanometry: a case study.

The use of 226 Hz tympanometry in neonates and infants has been controversial due to the large number of false negative responses for middle ear pathology. A review of the literature highlights several anatomical differences between this population and that of the adult, which is not recognized during interpretation of their tympanograms. The aim of the study was to document tympanometric changes in a single child using 226 Hz, 1000 Hz and sweep frequency probe tones until she was 6.5 months old. Both 226 Hz and 1000 Hz tympanograms show a maturational change in middle ear resonance from a mass to a stiffness-dominated system, which was corroborated by sweep frequency probe tones. It is suggested that high-frequency probe tones were able to increase test sensitivity to the mechanics of the middle ear when it was mass-dominated, as in this infant. Due to the large intersubject variability reported in the literature, it is recommended that both high and conventional probe tone tympanograms are performed in infants under 6 months of age to increase diagnostic accuracy. Middle ear resonance can also be determined for each individual enabling more appropriate selection of probe tones for Y, B and G tympanometry.