Effects of Bone Oscillator Coupling Method, Placement Location, and Occlusion on Bone-Conduction Auditory Steady-State Responses in Infants

Assessment of Interaural Attenuation in Infants and Young Children Using Bone-Conducted Auditory Brainstem Response

OBJECTIVES

In hearing assessment, the term interaural attenuation (IAA) is used to quantify the reduction in test signal intensity as it crosses from the side of the test ear to the nontest ear. In the auditory brainstem response (ABR) testing of infants and young children, the size of the IAA of bone-conducted (BC) stimuli is essential for the appropriate use of masking, which is needed for the accurate measurement of BC ABR thresholds. This study aimed to assess the IAA for BC ABR testing using 0.5 to 4 kHz narrowband (NB) CE-chirp LS stimuli in infants and toddlers with normal hearing from birth to three years of age and to examine the effects of age and frequency on IAA.

DESIGN

A total of 55 infants and toddlers with normal hearing participated in the study. They were categorized into three age groups: the young group (n = 31, infants from birth to 3 mo), middle-aged group (n = 13, infants aged 3-12 mo), and older group (n = 11, toddlers aged 12-36 mo). The participants underwent BC ABR threshold measurements for NB CE-chirp LS stimuli at 0.5 to 4 kHz. For each participant, one ear was randomly defined as the "test ear" and the other as the "nontest ear." BC ABR thresholds were measured under two conditions. In both conditions, traces were recorded from the channel ipsilateral to the test ear, whereas masking was delivered to the nontest ear. In condition A, the bone oscillator was placed on the mastoid of the test ear, whereas in condition B, the bone oscillator was placed on the mastoid contralateral to the test ear. The difference between the thresholds obtained under conditions A and B was calculated to assess IAA.

RESULTS

The means of IAA (and range) in the young age group for the frequencies 0.5, 1, 2, and 4 kHz were 5.38 (0-15) dB, 11.67 (0-30) dB, 21.15 (10-40) dB, and 23.53 (15-35) dB, respectively. Significant effects were observed for both age and frequency on BC IAA. BC IAA levels decreased with age from birth to 36 mo. In all age groups, smaller values were observed at lower frequencies and increased values were observed at higher frequencies.

CONCLUSIONS

BC IAA levels were both age and frequency dependent. The study found that the BC IAA values for lower stimulus frequencies were smaller than previously assumed, even in infants younger than 3 mo. These results suggest that masking should be applied in BC ABR threshold assessments for NB CE-chirp LS stimuli at 0.5, 1, and 2 kHz, even in young infants. Masking may not be necessary for testing at 4 kHz if a clear response is obtained at 15 dB normal-hearing level (nHL) in infants younger than 3 mo.

A pilot study to validate AMTAS in a specialist outpatient clinic at a public restructured hospital in Singapore

Background

The prevalence of age-related hearing loss is expected to increase with the ageing population in Singapore resulting in increased demand for pure tone audiometry (PTA). One way of meeting the increased demand for PTA is the Automated Method of Testing Auditory Sensitivity (AMTAS). Nonetheless, before AMTAS may be implemented, it is important to validate its results by comparing them against those of conventional PTA for the diverse Singaporean population.

Methods

100 participants were recruited from the Otorhinolaryngology clinic at a public hospital. PTA was conducted for participants via the conventional method and AMTAS. The hearing thresholds obtained via the two methods were then compared. A feedback questionnaire on the use of AMTAS was also completed by all participants.

Results

Air and bone conduction threshold results from 80 participants were analysed. The absolute mean difference in air conduction thresholds obtained via the two methods ranged from 3.30 to 9.62 dB. The absolute mean difference in bone conduction thresholds obtained via the two methods ranged from 8.16 to 9.38 dB. Most participants indicated that the machine was easy to use. Other feedback collected indicated that the AMTAS testing environment was noisy and that testing was fast.

Conclusion

This study finds that despite differences in hearing thresholds obtained via AMTAS and manual PTA, these differences are within the acceptable 10 dB test-retest variation. Nonetheless, existing issues related to the AMTAS software and noise levels in the testing environment will need to be addressed before it can be used in the clinic.

Contribution of bone conduction click-evoked auditory brainstem responses to diagnosis of hearing loss in infants in France

INTRODUCTION

Neonatal hearing screening in France involves confirmation by a childhood hearing expert centre in case of suspected hearing loss. Although click-evoked air-conduction auditory brainstem responses (AC-ABR) are the gold standard in France, there are no guidelines for bone-conduction ABRs (BC-ABR). The present study assessed the interest of associating click-evoked BC- and AC-ABRs for diagnostic confirmation in neonatal hearing screening.

MATERIALS AND METHODS

A retrospective study included 59 infant ears with conductive hearing loss referred to the centre of Lyon, France. Objective hearing thresholds were compared between click-evoked BC- and AC-ABRs on a method previously validated in a normal-hearing population.

RESULTS

There was a significant difference in mean threshold between AC-ABR (53.27±1.189 dBnHL) and BC-ABR (28.1±0.935 dBnHL) (P<0.001). AC thresholds ranged from 40 to 60 dBnHL while BC thresholds exceeded 40 dBnHL in only 9 ears.

CONCLUSION

Using BC-ABRs could reduce the false-positive rate in neonatal bilateral permanent hearing loss screening, in complement to AC-ABRs using the same stimulus. Click-evoked BC-ABR could be contributive whenever conductive hearing loss is suspected, in complement to AC-ABR, without unreasonably increasing examination time.

Effective Masking Levels for Bone Conduction Auditory Brainstem Response Stimuli in Infants and Adults with Normal Hearing

OBJECTIVE

The purpose of the present study was to investigate effective masking levels (EMLs) for bone conduction (BC) auditory brainstem response (ABR) testing in infants and adults. Early hearing detection and intervention programs aim to limit delays in identifying ear-specific type/degree of hearing loss in infants using the ABR. Ear-specific assessment poses challenges as sound delivered to one ear can travel across the skull and activate the contralateral cochlea. Wave V amplitude and latency measures ipsilateral and contralateral to the bone oscillator can be compared to isolate the test cochlea in some cases; however, when these findings are equivocal, clinical masking is required. This study aims to determine EMLs for ABRs elicited to 500- and 2000-Hz BC stimuli for normal-hearing infants (0 to 18 months) and adults.

DESIGN

Participants were 21 adults (18 to 54 years) and 24 infants (5 to 47 weeks) with normal hearing. BC 500- and 2000-Hz brief tonal stimuli at intensities approximating normal levels were presented via a B-71 oscillator (infants: 20 dB nHL at 500 Hz and 30 dB nHL at 2000 Hz; adults: 500 and 2000 Hz at 20 and 30 dB nHL, respectively). White noise masking was presented binaurally via ER-3A earphones (22 to 82 dB SPL; 10-dB steps). The lowest level of masking to eliminate a BC response was deemed the EML.

RESULTS

For stimuli presented at 20 dB nHL, adult mean (1 SD) EMLs for 500 and 2000 Hz were 65 (9) and 53 (6) dB SPL, respectively. Mean EMLs for infants were 80 (6) dB SPL for 500 Hz at 20 dB nHL and 64 (9) dB SPL for 2000 Hz at 30 dB nHL. Compared to adults, infants required approximately 13 dB more masking at 500 Hz but a similar amount of masking at 2000 Hz. Infants required 26 dB more masking at 500 versus 2000 Hz, whereas, adults required only 12 dB more masking.

CONCLUSIONS

Maximum binaural EMLs for infant BC responses elicited to 500 Hz at 20 dB nHL are 82 dB SPL, and for 2000 Hz at 30 and 40 dB nHL, respectively, are 72 and 82 dB SPL. Monaural masking levels for the nontest ear (assuming 10 dB of interaural attenuation) recommended clinically are as follows: (1) 500 Hz: 72 and 82 dB SPL at 20 and 30 dB nHL, respectively; and (2) 2000 Hz: 62, 72, and 82 dB SPL at 30, 40, and 50 dB nHL, respectively. Unsafe levels of white noise would be needed to effectively mask at greater stimulus levels.

Neonate auditory brainstem response repeatability with controlled force gauge bone-conducted stimulus delivery

OBJECTIVE

The feasibility and repeatability of neonate auditory brainstem responses (ABRs) with a controlled hand-held applied force gauge for bone-conducted stimulus delivery was examined.

DESIGN

A repeated measures test-retest design was employed.

STUDY SAMPLE

Participants were 27 healthy neonates. A 4000 Hz bone-conducted CE-Chirp octave band stimulus evoked the ABRs. Intra- and intertester conditions were employed with a prototype hand-held applied force gauge (Etymōtic Research) attached to the superior aspect of the bone vibrator. The bone vibrator was placed in a superoposterior auricular position and held manually. The force gauge displayed a desired coupling force via an LED light indicator.

RESULTS

Three sets of replicated ABRs were recorded from all neonates: initial test and retest with one tester (i.e. intratester 1 and 2) and final test with a second tester (i.e. intertester). No significant differences in intra- or intertester ABR wave V latencies or amplitudes were found (p > 0.05). Coefficients of reliability (Cronbach's α) were .95 and .43 for wave V latencies and amplitudes, respectively.

CONCLUSIONS

A hand-held applied force gauge may be a reliable means of delivering controlled bone-conducted stimuli in ABR assessments in neonates and infants.

Air and Bone Conduction Click and Tone-Burst Auditory Brainstem Thresholds Using Kalman Adaptive Processing in Nonsedated Normal-Hearing Infants

OBJECTIVES

To study normative thresholds and latencies for click and tone-burst auditory brainstem response (TB-ABR) for air and bone conduction in normal infants and those discharged from neonatal intensive care units, who passed newborn hearing screening and follow-up distortion product otoacoustic emission. An evoked potential system (Vivosonic Integrity) that incorporates Bluetooth electrical isolation and Kalman-weighted adaptive processing to improve signal to noise ratios was employed for this study. Results were compared with other published data.

DESIGN

One hundred forty-five infants who passed two-stage hearing screening with transient-evoked otoacoustic emission or automated auditory brainstem response were assessed with clicks at 70 dB nHL and threshold TB-ABR. Tone bursts at frequencies between 500 and 4000 Hz were used for air and bone conduction auditory brainstem response testing using a specified staircase threshold search to establish threshold levels and wave V peak latencies.

RESULTS

Median air conduction hearing thresholds using TB-ABR ranged from 0 to 20 dB nHL, depending on stimulus frequency. Median bone conduction thresholds were 10 dB nHL across all frequencies, and median air-bone gaps were 0 dB across all frequencies. There was no significant threshold difference between left and right ears and no significant relationship between thresholds and hearing loss risk factors, ethnicity, or gender. Older age was related to decreased latency for air conduction. Compared with previous studies, mean air conduction thresholds were found at slightly lower (better) levels, while bone conduction levels were better at 2000 Hz and higher at 500 Hz. Latency values were longer at 500 Hz than previous studies using other instrumentation. Sleep state did not affect air or bone conduction thresholds.

CONCLUSIONS

This study demonstrated slightly better wave V thresholds for air conduction than previous infant studies. The differences found in the present study, while statistically significant, were within the test step size of 10 dB. This suggests that threshold responses obtained using the Kalman weighting software were within the range of other published studies using traditional signal averaging, given step-size limitations. Thresholds were not adversely affected by variable sleep states.

Effective masking levels for bone conduction auditory steady state responses in infants and adults with normal hearing

OBJECTIVE

To obtain ear-specific bone conduction thresholds, masking of the nontest ear is often required. Bone conduction masking has not been formally investigated for infants assessed physiologically. The objective of this study was to determine effective masking levels (EMLs) for auditory steady state responses (ASSRs) elicited by bone-conducted stimuli in a group of normal-hearing infants and adults.

DESIGN

Participants were 15 infants younger than 6 mo and 15 adults, all with normal hearing. EML was defined as the lowest level of a binaural air-conducted masker that resulted in absent bone conduction ASSRs. Stimuli were single bone-conducted tones that were 100% amplitude modulated and 25% frequency modulated at 85 and 101 for 1000 and 4000 Hz, respectively. The stimuli were calibrated in dB HL (ANSI S3.6-1996) and expressed in dB HL or dB SL (dB relative to mean bone conduction ASSR thresholds reported in a previous study). The maskers were 1 and 4 kHz narrowband noise generated by a clinical audiometer. Unmasked and masked ASSRs were obtained for each participant. Real ear-to-coupler differences (RECDs) were also obtained for each participant and were used to convert masker dB SPL measured in the coupler to dB SPL in the individual ear canal.

RESULTS

Infant EMLs for ASSRs elicited to bone-conducted stimuli in dB HL were 6 to 7 dB higher and 8 to 10 dB lower for 1000 and 4000 Hz, respectively, compared with adults. When masker was adjusted for RECDs, infant EMLs were 12 dB higher at 1000 Hz and similar at 4000 Hz compared with adults. When the stimulus levels were corrected for the mean differences in ASSR bone conduction thresholds between infants and adults and the masker levels adjusted for RECDs, infants had lower EMLs at 1000 Hz and equal EMLs at 4000 Hz, in comparison to adults. Frequency- and level-dependent effects on ASSR amplitude due to masking were found and differed between infants and adults.

CONCLUSIONS

Our findings indicate that there are frequency- and level-dependent infant-adult differences in EMLs for bone conduction ASSRs and confirm that a 1000 Hz stimulus is 12 dB more effective for infants compared with adults. The following infant preliminary masking levels for bone conduction stimuli are recommended: (i) 1000 Hz: 48 and 58 dB SPL at 15 and 25 dB HL, respectively, and (ii) 4000 Hz: 40 and 45 dB SPL at 25 and 35 dB HL, respectively.

Multiple auditory steady state response thresholds to bone conduction stimuli in adults with normal and elevated thresholds

OBJECTIVE

Auditory steady state responses (ASSRs) to multiple air conduction (AC) stimuli modulated at ∼80 Hz have been shown to provide reasonable estimates of the behavioral audiogram. To distinguish the type of hearing loss (i.e., conductive, sensorineural, or mixed), bone conduction (BC) results are necessary. There are few BC-ASSR data, especially for individuals with hearing loss. The present studies aimed to (1) determine multiple ASSR thresholds to BC stimuli in adults with normal hearing, masker-simulated hearing loss, and sensorineural hearing loss (SNHL) and (2) determine how well BC-ASSR distinguishes normal versus elevated thresholds to BC stimuli in adults with normal hearing or SNHL.

DESIGN

Multiple ASSR and behavioral thresholds for BC stimuli were determined in two studies. Study A assessed 16 normal-hearing adults with relatively flat threshold elevations produced by 50, 60, and 70 dB SPL AC masking noise, as well as no masking. Study B assessed 10 adults with normal hearing and 40 adults with SNHL. In both studies, the multiple (500 to 4000 Hz) ASSR stimuli were modulated between 77 and 101 Hz and varied in intensity from 0 to 50 dB HL in 10-dB steps. Stimuli were presented using a B71 bone oscillator held on the temporal bone by an elastic band while participants relaxed or slept.

RESULTS

Study A: Correlations (r) between behavioral and ASSR thresholds for all conditions combined were 0.77, 0.87, 0.90, and 0.87 for 500, 1000, 2000, and 4000 Hz, respectively. ASSR minus behavioral threshold difference scores for all frequencies combined for the no-masker, 50, 60, and 70 dB SPL masker conditions were 14.3 ± 9.2, 12.1 ± 10.4, 12.7 ± 7.7, and 11.4 ± 8.1 dB, respectively. Study B: The difference scores for 500, 1000, 2000, and 4000 Hz were, on average, 15.7 ± 12.3, 10.3 ± 10.7, 9.7 ± 10.3, and 5.7 ± 7.9 dB, respectively, with correlations of 0.73, 0.84, 0.87, and 0.94 for the normal-hearing and SNHL groups combined. The ASSR minus behavioral difference scores were significantly larger for 500 Hz and significantly smaller for 4000 Hz compared with 1000 and 2000 Hz. Across all frequencies, the BC-ASSR correctly classified 89% of thresholds as "normal" or "elevated" (92% correct for 1000, 2000, and 4000 Hz).

CONCLUSIONS

The threshold difference scores and correlations in individuals with SNHL are similar to those in normal listeners with simulated SNHL. These difference scores are also similar to those shown by previous studies for the AC-ASSR in individuals with SNHL, at least for 1000 to 4000 Hz. The BC-ASSR provides a reasonably good estimate of BC behavioral threshold in adults, especially between 1000 and 4000 Hz. Further research is required in infants with hearing loss.

Bone-conducted hearing assessment with 80-Hz multiple auditory steady-state responses to brief tones in adults with normal hearing

OBJECTIVE

To investigate interactions (if any) in the bone-conduction auditory steady-state response (BC ASSR) between multiple brief tones presented simultaneously.

METHODS

500-, 1,000-, 2,000-, and 4,000-Hz brief tones, repeated at a rate of 77-101 Hz, were presented using a B-71 vibrator. BC ASSR thresholds and amplitudes at 50 dB nHL were measured in two conditions where the stimulus was either presented alone or together with other stimuli.

RESULTS

Significantly larger amplitudes in the single-stimulus condition were found at 50 dB nHL. However, there was no significant threshold difference between single- and multiple-stimulus conditions. The BC ASSR thresholds (means ± SD) at 500, 1,000, 2,000, and 4,000 Hz were 96.7 ± 9.7, 75.3 ± 11.5, 65.6 ± 7.4, and 57.8 ± 7.2 dB re 1 μN ppe, respectively.

CONCLUSION

Interactions occurred in the multiple-stimulus condition at high presentation levels, but not at threshold levels. The results of the present study imply that BC ASSR thresholds to multiple brief-tone stimuli can be assessed at the same time, at least in normal-hearing adults.

Binaural measurement of bone conduction click evoked otoacoustic emissions in adults and infants

Transient evoked otoacoustic emissions (TEOAEs) are usually evoked with air conduction (AC) stimuli. Only a few reports exist about OAEs where stimuli have been delivered using bone conduction (BC) by placing a bone conductor on the forehead or the mastoid. The aims of the present study were to improve the test performance of BC-TEOAEs by using a nonlinear stimulation protocol and to find out, whether this technique can be applied in newborn hearing screening. BC-TEOAEs were measured binaurally in ten normal hearing adults and in ten infants. For measurements in infants, miniaturized probes without loudspeakers were constructed to allow a complete insertion of the probe in the infant's ear canal. It could be shown that robust and valid BC-TEOAEs can be elicited using a nonlinear stimulation protocol. Findings in adults indicated that BC-TEOAEs can be measured with properties similar to AC-TEOAEs. However, mean BC-TEOAE levels were reduced by 0.8-3.7 dB depending on frequency. In view of test time, this is compensated by performing binaural recordings. Measurements in infants indicated that the screening performance of BC-TEOAEs and AC-TEOAEs may be comparable. Further studies have to investigate, whether BC-TEOAEs are more robust than AC-TEOAEs against small conductive hearing loss.

[Auditory steady-state responses--the state of art]

The auditory steady-state responses (ASSR) is quite a new method of electrophysiological threshold estimation with no clinical standards. It was the aim of this study to review practical and theoretical thesis of ASSR and mention recent recommendations and achievements of this technique. The most common application of ASSR is diagnosis of hearing loss in children together with ABR test. In this paper we mentioned information about influence of physiological factors (age, sex, state of arousal, handedness) and type of recording technique (electrodes placement, air and bone stimulation, occlusion effect, amplitude and frequency stimulation, multiple or single frequency stimulation, dichotic and monotic recording technique and type of hearing loss) on ASSR. We conclude that putting ASSR in clinical use as an standardized method it is necessary to do research with numerous groups of patients using the same equipment and parameters of tests.

Auditory steady-state responses to bone conduction stimuli in children with hearing loss

OBJECTIVE

The auditory steady-state response (ASSR) to air-conduction (AC) stimuli has been widely incorporated into audiological test-batteries for the pediatric population. The current understanding of ASSR to bone conduction (BC) stimuli, however, is more limited, especially in the case of infants and children. There are few reports on ASSR thresholds to BC stimuli in infants and young children, and none for infants or children with hearing loss. The objective of this study was to investigate BC ASSR thresholds in young children with normal hearing and various types and degrees of hearing loss.

METHODS

AC and BC ASSR thresholds are reported for 48 young children (mean age+/-SD=2.8+/-1.9 years; age range=0.25-11.5 years; 23 female). Hearing status was classified by assessing all children with a comprehensive test battery including tympanometry, diagnostic distortion-product otoacoustic emissions, click-evoked AC auditory brainstem response, AC and BC ASSR thresholds, and an otologic examination. The subjects were assigned to the categories normal hearing, conductive loss, and sensorineural loss (mild-to-moderate or severe-to-profound), for group analysis. AC and BC ASSR stimuli (carrier frequencies: 0.25-4 kHz; 67-95 Hz modulation rates; 100% amplitude and 10% frequency modulated) were presented using the GSI Audera system.

RESULTS

Minimum levels at which spurious BC ASSR occur were established in the group of children with severe-to-profound sensorineural hearing loss (25, 40, 60, 60 and 60 dB for 0.25, 0.5, 1, 2, and 4 kHz, respectively). Children with normal hearing presented mean (1 SD) BC ASSR thresholds of 19 (9), 18 (7), 16 (11), 24 (7), and 26 (8) dB HL at 0.25, 0.5, 1, 2, and 4 kHz, respectively. Significantly lower thresholds (p<0.0001) were obtained for 0.25, 0.5 and 1 kHz than for 2 and 4 kHz. At 0.25 kHz, 39% of thresholds were at the minimum level of spurious response occurrence. More than half (54%) of the BC thresholds in the group with mild-to-moderate sensorineural hearing loss were recorded at or above the minimum levels at which spurious response occurred. In children with conductive hearing loss, the average BC ASSR thresholds corresponded closely to those in the normal hearing group except at 1 kHz and revealed an air-bone gap.

CONCLUSIONS

Spurious bone conduction ASSR responses limit the intensity range for which the technique may be employed in infants and children, especially at lower frequencies. Consequently, the 0.25 kHz stimulus is not recommended for clinical use. In infants and young children, sensorineural hearing loss of a moderate or greater degree in the high frequencies (1-4 kHz), and of a mild or greater degree in the low frequencies (0.5 kHz), cannot be quantified using BC ASSR. This is due to the presence of the stimulus artifact. In cases of conductive hearing loss, BC ASSR can effectively quantify sensory hearing between 0.5 and 4 kHz, but interpretations must be made cautiously within the limitations of stimulus artifact occurrence across frequencies.