Assessing Sensorineural Hearing Loss Using Various Transient-Evoked Otoacoustic Emission Stimulus Conditions

Abstract

Objectives: An important clinical application of transient-evoked otoacoustic emissions (TEOAEs) is to evaluate cochlear outer hair cell function for the purpose of detecting sensorineural hearing loss (SNHL). Double-evoked TEOAEs were measured using a chirp stimulus, in which the stimuli had an extended frequency range compared to clinical tests. The present study compared TEOAEs recorded using an unweighted stimulus presented at either ambient pressure or tympanometric peak pressure (TPP) in the ear canal and TEOAEs recorded using a power-weighted stimulus at ambient pressure. The unweighted stimulus had approximately constant incident pressure magnitude across frequency, and the power-weighted stimulus had approximately constant absorbed sound power across frequency. The objective of this study was to compare TEOAEs from 0.79 to 8 kHz using these three stimulus conditions in adults to assess test performance in classifying ears as having either normal hearing or SNHL.

Design: Measurements were completed on 87 adult participants. Eligible participants had either normal hearing (N = 40; M F = 16 24; mean age = 30 years) or SNHL (N = 47; M F = 20 27; mean age = 58 years), and normal middle ear function as defined by standard clinical criteria for 226-Hz tympanometry. Clinical audiometry, immittance, and an experimental wideband test battery, which included reflectance and TEOAE tests presented for 1-min durations, were completed for each ear on all participants. All tests were then repeated 1 to 2 months later. TEOAEs were measured by presenting the stimulus in the three stimulus conditions. TEOAE data were analyzed in each hearing group in terms of the half-octave-averaged signal to noise ratio (SNR) and the coherence synchrony measure (CSM) at frequencies between 1 and 8 kHz. The test-retest reliability of these measures was calculated. The area under the receiver operating characteristic curve (AUC) was measured at audiometric frequencies between 1 and 8 kHz to determine TEOAE test performance in distinguishing SNHL from normal hearing.

Results: Mean TEOAE SNR was ≥8.7 dB for normal-hearing ears and ≤6 dB for SNHL ears for all three stimulus conditions across all frequencies. Mean test-retest reliability of TEOAE SNR was ≤4.3 dB for both hearing groups across all frequencies, although it was generally less (≤3.5 dB) for lower frequencies (1 to 4 kHz). AUCs were between 0.85 and 0.94 for all three TEOAE conditions at all frequencies, except for the ambient TEOAE condition at 2 kHz (0.82) and for all TEOAE conditions at 5.7 kHz with AUCs between 0.78 and 0.81. Power-weighted TEOAE AUCs were significantly higher (p < 0.05) than ambient TEOAE AUCs at 2 and 2.8 kHz, as was the TPP TEOAE AUC at 2.8 kHz when using CSM as the classifier variable.

Conclusions: TEOAEs evaluated in an ambient condition, at TPP and in a power-weighted stimulus condition, had good test performance in identifying ears with SNHL based on SNR and CSM in the frequency range from 1 to 8 kHz and showed good test-retest reliability. Power-weighted TEOAEs showed the best test performance at 2 and 2.8 kHz. These findings are encouraging as a potential objective clinical tool to identify patients with cochlear hearing loss.

Figure 1

The wideband absorbance pattern (top) as a function of frequency for an adult ear with normal hearing. SPL and power levels (dB) across the spectrum as well as the total SPL are also illustrated (bottom).

Figure 2

The left panels are the time waveforms for the unweighted ambient chirp (top), unweighted chirp at TPP (middle), and power-weighted ambient chirp (bottom) in the same adult ear with normal hearing from Fig. 1. TPP was +15 daPa for this ear. The stimulus swept in time from 0.71 to 8 kHz in approximately 42 ms. The center panels are the sound exposure levels (SEL) for stimulus 1 (P₁, negative triangle) and stimulus 2 (P₂, positive triangle) as a function of frequency for the same three chirp conditions respectively (top, middle, and bottom). The total SEL for each chirp is displayed in the lower-right corner of the left panels. The right panels are the resulting TEOAE SNR (dB) (solid lower line) and CSM (solid upper line) for the same three chirp conditions respectively. The lower and upper dashed lines in each panel represent the critical SNR and CSM respectively, corresponding to a detection criterion at p=0.05.

Figure 3

Box and whisker plots for pure-tone threshold data from 1 to 8 kHz in dB HL obtained at the first valid session from the two test sessions for ears with normal hearing (light gray boxes; ≤20 dB HL) and SNHL (dark gray boxes; >20 dB HL). Each shaded box is an interquartile range (IQR) from the 25^th to 75^th percentiles. The horizontal line within each box is the median, while the filled stars represent the mean for the normal hearing group and SNHL group, respectively. Whiskers denote data within the lesser of ±1.5 times the IQR or the full data range, and any circles (normal hearing) or crosses (SNHL) that are beyond the whiskers represent outliers.

Figure 4

The model-based mean estimate (see Methods for details) of absolute test-retest reliability for pure-tone hearing thresholds from ears with normal hearing (filled stars) and SNHL (open circles). The error bars represent ±1 SE of the mean.

Figure 5

Box and whisker plots for the TEOAE SNR (top panel) and CSM (bottom panel) from data obtained at the first valid session of the two test sessions for ears with normal hearing (light gray boxes) and ears with SNHL (dark gray boxes) at each half-octave frequency for three TEOAE conditions: Ambient pressure (left), TPP (middle) and Power Weighted (right). For each panel the horizontal line within each box is the median, while the filled stars represent the mean for the normal hearing group and SNHL group, respectively. Whiskers denote data within the lesser of ±1.5 times the IQR or the full data range, and any circles (normal hearing) or crosses (SNHL) that are beyond the whiskers represent outliers.

Figure 6

The model-based mean estimate of TEOAE SNR (in dB, top panel) and CSM (bottom panel) at each half-octave frequency for ears with normal hearing (light gray) and SNHL (dark gray). Mean findings for the three TEOAE stimulus methods are plotted together at each frequency and staggered for clarity: Ambient (O), TPP (+), and Power Weighted (X). Error bars in both panels represent ±1 SE from the mean. Some data are slightly displaced horizontally to improve clarity.

Figure 7

The model-based mean estimate of absolute test-retest reliability for TEOAE SNR (top panel) and CSM (bottom panel) at each half-octave frequency for ears with normal hearing (filled stars) and SNHL (open circles). Data are separately plotted for each of three TEOAE stimulus methods: Ambient (left), TPP (middle), and Power Weighted (right). Error bars represent ±1 SE from the mean.

Figure 8

AUCs describe how well ears are classified as having normal hearing or having SNHL at each half-octave frequency based upon TEOAE SNR (left panel) and CSM (right panel) using three TEOAE stimulus methods: Ambient (O), TPP (+), and Power Weighted (X). The number of ears providing data at each frequency is shown in Table 1. Data represented are from the first valid test session from each ear in the dataset.

Figure 9

The distribution of TPP (of the downswept tympanogram) from the first valid session for all of the ears (normal hearing and SNHL).