Controlled exploration of the effects of conductive hearing loss on wideband acoustic immittance in human cadaveric preparations

Abstract

Current clinical practice cannot distinguish, with any degree of certainty, the multiple pathologies that produce conductive hearing loss in patients with an intact tympanic membrane and a well-aerated middle ear without exploratory surgery. The lack of an effective non-surgical diagnostic procedure leads to unnecessary surgery and limits the accuracy of information available during pre-surgical consultations with the patient. A non-invasive measurement to determine the pathology responsible for a conductive hearing loss prior to surgery would be of great value. This work investigates the utility of wideband acoustic immittance (WAI), a non-invasive measure of middle-ear mobility, in the differential diagnosis of pathologies responsible for conductive hearing loss. We focus on determining whether power reflectance (PR), a derivative of WAI, is a possible solution to this problem. PR is a measure of the fraction of sound power reflected from the middle ear when a sound stimulus is presented to the ear canal. PR and other metrics of middle-ear performance (such as ossicular motion via laser Doppler vibrometry) were measured in well-controlled human temporal bone preparations with simulated pathologies. We report measurements before and after simulation of stapes fixation (n=8), malleus fixation (n=10), ossicular disarticulation (n=10), and superior canal dehiscence (n=8). Our results are consistent with the small set of previously published reflectance measurements made in temporal bones and patients. In this present study, these temporal bone experiments with different middle- and inner-ear pathologies were compared to the initial normal state by analyzing both WAI and ossicular motion, demonstrating that WAI can be a valuable tool in the diagnosis of conductive hearing loss.

Minimally invasive laser vibrometry (MIVIB) with a floating mass transducer – A new method for objective evaluation of the middle ear demonstrated on stapes fixation

“…The largest deviations were seen around the resonance frequency of 1 kHz. As previously reported by us (Merchant et al, 2016;Nakajima et al, 2005;Peacock et al, 2016), this work confirms that a fixation in the attic can be simulated by utilizing cement to fix the malleus or incus to the tegmen. MIVIB was able to show that this fixation led to a significant reduction in the absolute velocities of both the umbo and incus.…”

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

“…This finding suggests that absorbance measurements might be useful in improving the effects of corrective surgery for otosclerosis, although further research is needed to explore this idea. A relevant study of fixed stapes pathologies in human temporal bones is that of Merchant et al (2016), which positively assessed the use of WAI to diagnose the particular type of middle-ear pathology related to the presence of conductive hearing loss. A difference between this study using temporal bones with the present study using human participants was that the present study included a group of ears with normal hearing.…”

“…Thus, a test of middleear function other than an evoked OAE or ASR test is needed to better identify a risk of otosclerosis. The ambient reflectance test has the potential for absorbance to differentiate between conductive and sensorineural dysfunction, and differentiate between differing types of middle-ear pathology in human temporal bones (Feeney, Grant, et al, 2003;Merchant et al, 2016) and in patients with conductive impairments (Nakajima et al, 2012), but no data are available on pressurized forms of these tests in ears with otosclerosis. The present research examined the relative abilities of absorbance and group delay to classify ears as having otosclerosis or normal hearing.…”

Compensating for ear-canal acoustics when measuring otoacoustic emissions

“…However, at frequencies greater than 10 kHz, jRj changed with probe insertion depth more than expected based on retest measurements, and in some instances jRj exceeded 1, implying errors in the measurements or a violation of the assumptions. Values of jRj exceeding 1 at high frequencies were also reported in Souza et al (2014) for normal human ears, in Merchant et al (2016) for temporal bone preparations, and in Lewis and Easterday (2016) for measurements in ear simulators. Lewis and Easterday (2016) suggest that the sensitivity of jRj to probe placement at high frequencies may be due to the impedance mismatch created at the plane of the sound source in the ear canal.…”

“…7, solid lines). Maximal changes in L 2 of a few dB occur for f DP near 9-10 kHz (i.e., for f 2 > 10 kHz), where the estimated ear-canal reflectance depends on insertion depth and sometimes takes on unphysical values (e.g., jRj > 1, see also Souza et al, 2014;Lewis and Easterday, 2016;Merchant et al, 2016). At these higher frequencies, FPL-calibration is FIG.…”