Identifying otosclerosis with battery of aural acoustical tests of absorbance, group delay, reflex threshold, and chirp-evoked otoacoustic emissions

Abstract

This study evaluated the clinical utility in diagnosing otosclerosis with aural acoustical tests of absorbance, acoustic reflex threshold (ART), and otoacoustic emissions (OAEs) in 23 normal-hearing (NH) ears, 12 ears diagnosed with otosclerosis (OS), and 13 ears after surgical intervention (SU) for otosclerosis. Subjects received audiometric evaluations, and tests of ipsilateral/contralateral ART, pressure reflectance (0.25–8 kHz) parameterized by absorbance and group delay at ambient pressure and at swept tympanometric pressures, and chirp-evoked OAEs (1–8 kHz). ARTs were measured using tonal and broadband noise activators, based on differences in wideband absorbed sound power before and after activator presentation. For NH compared to OS ears, mean ambient absorbance was larger at 4 kHz; mean tympanometric absorbance had larger peak-to-tail differences at low and high frequencies. Probe-to-eardrum length was estimated using group delay at the frequency of the minimum absorbance above 2 kHz, and combined with acoustically estimated area to calculate wideband compensated admittance at the eardrum. Absorbance and compensated group delay revealed complementary information on middle-ear function. Typical OS and SU ear tests showed absent TEOAEs and ARTs, reduced absorbance in OS ears, and anomalous reflectance <1 kHz in SU ears. Other middle-ear conditions showed different patterns of test-battery responses. [Research supported by NIH.]