Interaural Multiple Frequency Tympanometry Measures: Clinical Utility for Unilateral Conductive Hearing Loss

Abstract

Background: Tympanometry is a routine clinical measurement of the acoustic immittance of the ear as a function of ear canal air pressure. The 226 Hz tympanogram can provide clinical evidence for conditions such as a tympanic membrane perforation, Eustachian tube dysfunction, middle ear fluid, and ossicular discontinuity. Multiple frequency tympanometry using a range of probe tone frequencies from low to high has been shown to be more sensitive than a single probe tone tympanogram in distinguishing between mass- and stiffness-related middle ear pathologies (Colletti, 1975; Funasaka et al, 1984; Van Camp et al, 1986). Purpose: In this study we obtained normative measures of middle ear resonance by using multiple probe tone frequency tympanometry. Ninety percent ranges for middle ear resonance and for interaural differences were calculated. Research Design: In a mixed design, normative data were collected from both ears of male and female adults. Study Sample: Twelve male and 12 female adults with normal hearing and normal middle ear function participated in the study. Data Collection and Analysis: Multiple frequency tympanograms were recorded with a commercially available immittance instrument (GSI Tympstar) to obtain estimates of middle ear resonant frequency (RF) using ΔB, positive tail, and negative tail methods. Data were analyzed using three-way mixed analyses of variance with gender as a between-subject variable and ear and method as within-subject variables. T-tests were performed, using the Bonferroni adjustment, to determine significant differences between means. Results: Using the positive and negative tail methods, a wide range of approximately 500 Hz was found for middle ear resonance in adults with normal hearing and normal middle ear function. The difference in RF between an individual's ears is small with 90% ranges of approximately ±200 Hz, indicating that the right ear RF should be either 200 Hz higher or lower in frequency compared to the left ear. This was true for both negative and positive tail methods. Conclusion: Ninety percent ranges were calculated to determine the difference in middle ear resonance expected between an individual's ears. These ranges can provide critical normative values for determining how pathology in an ear with a unilateral conductive hearing loss is altering the mass or stiffness characteristics of the middle ear system.