Identifying Otosclerosis with Aural Acoustical Tests of Absorbance, Group Delay, Acoustic Reflex Threshold, and Otoacoustic Emissions

Abstract

Background Otosclerosis is a progressive middle-ear disease that affects conductive transmission through the middle ear. Ear-canal acoustic tests may be useful in the diagnosis of conductive disorders. This study addressed the degree to which results from a battery of ear-canal tests, which include wideband reflectance, acoustic stapedius muscle reflex threshold (ASRT), and transient evoked otoacoustic emissions (TEOAEs), were effective in quantifying a risk of otosclerosis and in evaluating middle-ear function in ears after surgical intervention for otosclerosis. Purpose To evaluate the ability of the test battery to classify ears as normal or otosclerotic, measure the accuracy of reflectance in classifying ears as normal or otosclerotic, and evaluate the similarity of responses in normal ears compared with ears after surgical intervention for otosclerosis. Research Design A quasi-experimental cross-sectional study incorporating case control was used. Three groups were studied: one diagnosed with otosclerosis before corrective surgery, a group that received corrective surgery for otosclerosis, and a control group. Study Sample The test groups included 23 ears (13 right and 10 left) with normal hearing from 16 participants (4 male and 12 female), 12 ears (7 right and 5 left) diagnosed with otosclerosis from 9 participants (3 male and 6 female), and 13 ears (4 right and 9 left) after surgical intervention from 10 participants (2 male and 8 female). Data Collection and Analysis Participants received audiometric evaluations and clinical immittance testing. Experimental tests performed included ASRT tests with wideband reference signal (0.25–8 kHz), reflectance tests (0.25–8 kHz), which were parameterized by absorbance and group delay at ambient pressure and at swept tympanometric pressures, and TEOAE tests using chirp stimuli (1–8 kHz). ASRTs were measured in ipsilateral and contralateral conditions using tonal and broadband noise activators. Experimental ASRT tests were based on the difference in wideband-absorbed sound power before and after presenting the activator. Diagnostic accuracy to classify ears as otosclerotic or normal was quantified by the area under the receiver operating characteristic curve (AUC) for univariate and multivariate reflectance tests. The multivariate predictor used a small number of input reflectance variables, each having a large AUC, in a principal components analysis to create independent variables and followed by a logistic regression procedure to classify the test ears. Results Relative to the results in normal ears, diagnosed otosclerosis ears more frequently showed absent TEOAEs and ASRTs, reduced ambient absorbance at 4 kHz, and a different pattern of tympanometric absorbance and group delay (absorbance increased at 2.8 kHz at the positive-pressure tail and decreased at 0.7–1 kHz at the peak pressure, whereas group delay decreased at positive and negative-pressure tails from 0.35–0.7 kHz, and at 2.8–4 kHz at positive-pressure tail). Using a multivariate predictor with...

Measurement of Wideband Absorbance as a Test for Otosclerosis

“…For that reason, we decided to use a commercially available instrument (i.e., the popular Titan WBT Immittance System) and rely on typical test protocols to measure immittance-related quantities. Unlike some other similar studies [1,16,17,[36][37][38], we did not want to use dedicated systems made for research purposes. We wanted data for analyses to be easily obtained directly from the Titan system.…”

“…It is known that experimentally determined absorbance (as well as other similar measures) exhibit significant variability, both in normal hearing subjects [39] and in pathological ears [1]. This is due to natural inter-subject variability of ear acoustic properties [22] and random measurement errors of diverse origin [23,24,26].…”

“…Assessment of the effectiveness of various tests for otosclerosis based on immittance measures has been the subject of a number of studies [1,10,14,15,19,36,[40][41][42]. Authors have considered: (i) ambient pressure or peak pressure absorbance average in selected bands (typically 200-2000 Hz) [1]; (ii) resonance frequency (or frequency at π/2 phase shift) of the middle ear admittance [11,14]; and (iii) the group delay of energy reflectance [1,39]. It has been found that all of them have limited effectiveness, and do not provide adequate sensitivity and specificity for otosclerosis testing.…”

“…Otosclerosis manifests in abnormal growth of the ossicular bones and bony fixation of the anterior stapes plate leading to stiffening of the chain. Its typical clinical symptoms are, among other things, progressive conductive or mixed hearing loss, increased or absent acoustic stapedial reflex thresholds (ASRT), and lack of otoacoustic emissions [ 1 ]. A comprehensive description of cases of otosclerosis, its symptoms, development and consequences, and methods of surgical treatment can be found in [ 2 ].…”

“…Many investigations have confirmed that absorbance in otosclerotic ears is decreased compared to normal-hearing ears, especially in the low-frequency range [ 1 , 14 , 19 , 20 , 21 ]. The decrease is due to increased stiffness of the vibrating system which in turn gives rise to a decrease in low-frequency acoustic susceptance, and consequently an increase in reflection coefficient.…”