Statistical properties of ABR amplitudes and latencies. Implications for computation of reference limits and relation to click phase

A method for statistical analysis and computation of reference limits for ABR latency and amplitude variables is presented. Condensation and rarefaction ABRs from 47 healthy controls aged 4-58 years were investigated. With respect to gaussianity of distributions, the square root transformation was superior to the logarithmic transformation for amplitudes, while the logarithmic transformation performed better for amplitude ratios. Wave V latency and the I-V interpeak latency were nearly normally distributed, while other latencies and inter-peak latencies displayed varying displacement from a normal distribution. Rarefaction ABR distributions were slightly closer to normality than were condensation ABRs. Amplitude vs. following amplitude and latency vs. amplitude correlation coefficients were larger for R than for C click ABRs; thus R clicks seem to evoke a better synchronized neural volley. Most of the correlation between amplitude and latency could be explained by the influence of age and sex. Hence, age and sex matched reference limits for ABR amplitudes, without correction for latency, seem to be adequate in practical clinical work.     

The choice of ABR click polarity and amplitude variables in multiple sclerosis patients.

Evoked brainstem responses (ABR) to 75 dB nHL condensation (C), rarefaction (R), and alternating (A = C+R) clicks were investigated in healthy subjects and in patients with multiple sclerosis. A new wave IV-V 'shape ratio' (SR IV-V) was most sensitive. SR IV-V correlated most strongly with clinical MS classification, and seemed to be rather specific for retrocochlear dysfunction. Wave IV-V amplitude was also more sensitive than the common IV-V amplitude ratio. The variability of latencies and interpeak latencies was lower in ABR to A clicks than in ABR to either R or to C clicks. In patients, fewer subcomponents were found in ABR to A than in ABR to R and C clicks. ABR to A clicks were on the average slightly more sensitive than either C or R click ABR. Our results suggest that both A-mode ABR and the 'dispersion' variable SR IV-V can be used without significant problems in the diagnosis of brainstem demyelination. A test protocol which requires ABR to both C and R clicks to be abnormal, will, however, be less sensitive, though probably more specific.     

Gender effects in auditory brainstem responses to air- and bone-conducted clicks in neonates.

Examinations of gender differences in auditory brainstem response (ABR) wave V latencies and thresholds to air- and bone-conducted clicks were undertaken with neonates. Two hundred and two full-term neonates participated (i.e., 103 males and 99 females). Wave V latency measures for air- and bone-conducted click stimuli of 30, 45, and 60 dB nHL and 15 and 30 dB nHL, respectively, and thresholds to air- and bone-conducted clicks were determined. Female newborns displayed statistically significant shorter wave V latencies than male newborns for air-conducted click stimuli (i.e., approximately 0.2-0.3 ms; P=.0016). There were no significant gender differences in wave V latencies to bone-conducted click stimuli (P=.11). With respect to ABR thresholds, no statistically significant differences were observed for either air-conducted clicks (P=.054) or bone-conducted clicks (P=.18). Educational objectives: As a result of this activity, the participant will be able to (1) describe gender differences in ABR wave V latencies and thresholds to air- and bone-conducted clicks with neonates and (2) summarize possible explanations for observed gender differences in ABR wave V latencies and thresholds to air- and bone-conducted clicks with neonates.     

Interaction of click polarity, stimulus level, and repetition rate on the auditory brainstem response

The present study investigated the interaction of click polarity (compression, rarefaction, alternating), repetition rate (2.3 and 9.2 clicks per second), and stimulus level (60, 75, and 90 dB nHL) on auditory brainstem responses. Two tracings (trials) were obtained for each condition using 45 normally hearing subjects. Although no systematic Wave I, III, or V latency or amplitude differences were observed among polarities or repetition rates at the three intensities, statistically significant differences were observed for the following conditions: (1) Wave III latency at 90 dB nHL was longer for the 9.2 repetition rate than for the 2.3 rate, and latencies for compression clicks were shorter than rarefaction clicks; (2) Wave V latencies at 75 dB nHL were longer with compression clicks than with rarefaction clicks; (3) mean Wave V latencies at 60 and 75 dB nHL were slightly longer for the 2.3 click rate than for the 9.2 rate; and (4) Wave V amplitudes at 90 dB nHL were larger for rarefaction clicks than for compression clicks. Because latency and amplitude differences were small and only found in a few conditions, the results indicate that polarity is not a significant variable in normally hearing subjects when using slow repetition rates (less than or equal to 10 clicks per second) at moderate to high intensities (60 to 90 dB nHL). Because repetition rates of less than 10 clicks per second increases examination time but does not improve wave morphology, rates of 10 per second or faster are recommended for gathering normative data. Absolute amplitudes showed considerable intersubject variability, especially for Waves I and III. Intrasubject variability (test-retest) also was substantial. These findings suggest that absolute amplitudes may be of little use for distinguishing normal from pathologic populations.     

Diagnostic implications of stimulus polarity effects on the auditory brainstem response

The purpose of this study was to determine whether clicks presented in rarefaction or condensation modes produce more accurate diagnostic information. Subjects were 20 consecutive patients who were seen at the Mayo Clinic for unilateral acoustic neuromas. The nontumor ear served as a control to minimize intersubject variability in the latencies. A standard audiologic evaluation was followed by an auditory brainstem response (ABR) test for which the stimuli were rarefaction and condensation clicks. Responses were analyzed for the presence of waves I, III, and V; absolute latencies of waves I, III, and V; interpeak intervals I-III, III-V, and I-V; and interaural latency difference for wave V. The results indicated that measures from both polarities were similar in this set of patients and that neither click polarity provided diagnostic advantages over the other. Recommendations are to collect ABRs to both click polarities individually to obtain the full complement of waves on which to base the diagnostic impression.     

Influence of stimulus polarity on far-field auditory-evoked electrical responses in the chick

The effects of inverting click phase on far-field peripheral and brainstem auditory-evoked responses (PBARs) were examined in 8 White Leghorn chicks of age 3 wks. Significant latency differences occurred in all major positive peaks (Pla, P2a peripheral; P3a central) in response to rarefaction vs condensation clicks of equal intensity, with condensation clicks producing the shortest latencies (latency differences: Pla = 0.374, P2a = 0.372 and P3a = 0.352 msec, p less than .001). The mean latency shift corresponds to an equivalent sine wave frequency of approximately 1360 c/s, a value close to the spectral peak energy of the click. No differences in interpeak latency values were found nor any significant amplitude effects.     

Effects of stimulus phase on the normal auditory brainstem response.

The purpose of this investigation was to determine the effects of stimulus phase on the latencies and morphology of the auditory brainstem response (ABR) of normal-hearing subjects. Although click stimuli produced equivalent ABR latencies for the rarefaction and condensation phases, the subtraction of the waveforms from the two phases yielded a difference potential. Tone pip stimuli produced polarity differences that were inversely related to stimulus frequency: the higher the frequency, the smaller the ABR latency differences between responses to rarefaction and condensation stimuli, and the smaller the difference potentials. Thus, whereas the latency of click-evoked ABR is dominated by high-frequency responses with equivalent latencies regardless of stimulus phase, low-frequency responses contribute to the overall morphology of the ABR that yields the phasic difference potential. The implications of these findings are discussed with reference to subjects with high-frequency hearing losses.     

The normative basis for click and frequency-specific BERA in high-risk infants

The use of brainstem electric response audiometry (BERA) for early detection of hearing loss is predicated upon large-sample normative data. Auditory brainstem response (ABR) thresholds for click and notch-masked tonepip stimuli were examined in 230 normal infants with no risk factors for hearing loss, tested under audiometrically ideal conditions at between 48 and 56 weeks post-conception. The ABR threshold distributions for clicks and tonepips differed considerably. Almost all infants had click thresholds consistent with normal hearing on adult criteria, whereas many appeared to have hearing loss at 500 Hz. ABR latencies for 70 dBnHL clicks were more variable than expected, even in infants with click thresholds of 30 dB or better. In males, wave V latency was about 0.2 ms larger than in females, but there was no such difference for wave I. For both sexes, there was a linear decrease in wave V latency with age at approximately 0.1 ms per month, but wave I latency was constant.     

Effects of click duration of the latency of the early evoked response

The effect of click duration on the latency of waves I, III, and V was investigated by testing 20 normal-hearing subjects at 60 dB HL using electric pulses of 25, 50, 100, 200, and 400 microseconds. Alternating condensation and rarefaction clicks were used. The results revealed similar and nonsignificant latency differences for the 25-, 50-, and 100-microseconds pulses. However, the 100 microseconds duration is preferred to the 25-microseconds pulse because the latter reduced the maximum measurable hearing loss by about 13 dB. The results also showed that latencies increased approximately 0.10 ms as duration increased from 100 to 200 microseconds and by 0.20 ms when duration increased from 100 to 400 microseconds. Although such differences by themselves are small, they can combine with other stimulus or recording variables to be clinically significant. Therefore, it is important to control click duration when normative data are generated. A second experiment was conducted to assess the interaction of polarity (condensation, rarefaction, and alternating) and pulse duration (100 and 400 microseconds) on the wave V latency. These data revealed no latency differences among polarities at either duration.     

A comparison of the effects of broadband masking noise on the auditory brainstem response in young and older adults

We examined the effects of ipsilateral-direct, continuous, broadband noise on auditory brainstem response (ABR) wave I and V latencies and amplitudes in young adult versus older adult humans. It was hypothesized that age might influence the effects of masking noise on ABR peak latencies and/or amplitudes, given the frequent complaint of older persons' ability to process speech in background noise. Young adults had hearing thresholds of 20 dB HL or better for the octave frequencies from 250 to 8,000 Hz. A subset of older study participants had thresholds of 20 dB HL or better across frequency, but others had thresholds up to 45 dB HL. All data were collected and analyzed with a Nicolet Bravo. An electrode was placed on the tympanic membrane (as well as on high forehead and contralateral mastoid), and a click level of 115 dB pSPL was used to maximize wave I amplitude. Masker conditions included a no-noise control and noise levels ranging from 20 to 70 dB effective masking, in 10 dB steps. With increasing noise level, both age groups showed minimal changes in wave I latency, but substantial increases in wave V latency and I-V interval. Peak amplitudes decreased with increasing noise level. Mean amplitudes were smaller for the older group, most notably for wave I. Mean peak latencies were greater in the older group, but the I-V interval was similar across age groups, as was the change in peak latencies and I-V interval across noise level. ABR parameters for the older adults with hearing meeting the 20-dB HL criterion at all frequencies (older-better) were compared to those who didn't meet this criterion (older-worse). Mean wave I latency was greater and wave V latency and I-V interval were smaller for the older-worse group at all noise levels. Mean wave I and V amplitudes were similar for the older-better and older-worse groups. In participants with normal or near-normal hearing, ABR changes with increasing age included small latency increases and a substantial reduction in wave I amplitude. The effects of ipsilateral-direct masking noise on the click-evoked ABR are similar for young and older adults.     

Development of low-frequency tone burst versus the click auditory brainstem response

Often ABR threshold testing employs clicks to assess high-frequency hearing, and low-frequency tone bursts to assess low-frequency sensitivity. While a maturation effect has been shown for click stimuli, similar data are lacking for low-frequency toneburst stimuli. Thus, 305 infants ranging in conceptional age (CA) from 33 weeks to 74 weeks were tested. Absolute latencies were measured for wave V at 55, 35, and 25 dB nHL in response to a click and for wave V500 in response to a 500 Hz tone burst. Major wave latency in response to 500 Hz tone bursts decreases with age and do not stabilize by 70 weeks CA. Likewise, waves III and V latencies in response to clicks decrease with age, as has been reported by others, and do not stabilize by 70 weeks CA. Wave I latency produced by clicks did not decrease with age, being mature by 33 weeks CA.     

Auditory brainstem responses to single-slope stimuli. The influence of steepness and polarity

Click polarity has little influence on brainstem potentials. We applied an auditory stimulus similar to a step function generated in a closed acoustic system. The influence of stimulus onset steepness (comprising rise time and intensity) on wave V latency and amplitude was investigated. A remarkable latency prolongation was observed for condensation (C) compared with rarefaction (R), if a sharp bend at the foot of the slope was avoided. The C latency lag was nearly the amount of rise time. The effect can be explained by cochlear travel time. Wave V amplitude for R slopes was significantly enhanced. At high intensity and short rise time, it reached twice the values found with C slopes, or with clicks of either polarity. Although the explanations found are not yet satisfactory, a clinical application in cochlear diagnosis is predictable.     

The effects of electrode montage on the amplitude of wave V in the auditory brainstem response to maximum length sequence stimuli

The use of maximum length sequence (MLS) stimuli to elicit an auditory brainstem response (ABR) has been limited, in part, by the observation that these stimuli reduce ABR wave amplitudes. This study recorded ABR waveforms from 14 normally hearing adults using MLS click stimuli (maximum stimulus rate = 250 clicks per second) at stimulus levels of 70, 60, 50, 40, 30 and 20 dB nHL, with a vertical and then an ipsilateral electrode montage. The vertical electrode montage produced significantly larger (p < 0.05) wave V amplitudes, with no change in wave V latencies (p > 0.05), at all stimulus levels. This result suggests a vertical electrode montage could be used to counter some of the loss in wave V amplitude observed when using MLS stimuli.     

Could Tailored Chirp Stimuli Benefit Measurement of the Supra-threshold Auditory Brainstem Wave-I Response?

Auditory brainstem responses (ABRs) to broadband clicks are strongly affected by dyssynchrony, or “latency dispersion”, of their frequency-specific cochlear contributions. Optimized chirp stimuli, designed to compensate for cochlear dispersion, can afford substantial increase in broadband ABR amplitudes, particularly for the prominent wave-V deflection. Reports on the smaller wave I, however, which may be useful for measuring cochlear synaptopathy, have been mixed. This study aimed to test previous claims that ABR latency dispersion differs between waves I and V, and between males and females, and thus that using wave- and/or sex-tailored chirps may provide more reliable wave-I benefit. Using the derived-band technique, we measured responses from frequency-restricted (one-octave-wide) cochlear regions to energy-matched click and chirp stimuli. The derived-band responses’ latencies were used to assess any wave- and/or sex-related dispersion differences across bands, and their amplitudes, to evaluate any within-band dispersion differences. Our results suggest that sex-related dispersion difference within the lowest-frequency cochlear regions (< 1 kHz), where dispersion is generally greatest, may be a predominant driver of the often-reported sex difference in broadband ABR amplitude. At the same time, they showed no systematic dispersion difference between waves I and V. Instead, they suggest that reduced chirp benefit on wave I may arise as a result of chirp-induced desynchronization of on- and off-frequency responses generated at the same cochlear places, and resultant reduction in response contributions from higher-frequency cochlear regions, to which wave I is thought to be particularly sensitive.

     

An analysis of auditory brainstem responses in infants

Acoustic brainstem responses (ABRs) were recorded from 148 infants from 4 to 60 weeks of age. 28 subjects returned to the laboratory 3 or more times for additional recordings. Filtered clicks of 1, 2, 4 and 8 kHz were presented at two intensities, 30 and 50 dB HL re the average threshold for a group of young adults. Responses to a broadband click, 50 dB nHL, were also recorded. The latencies of waves I, III and V were measured. Wave I latencies for the 8 kHz filtered click showed no change but those for lower frequencies decreased with age. The latency decreases with age were largest for wave V, and, among the filtered clicks, was largest for the responses to 1 kHz. Best-fitting curves were determined for latency vs. age for each filtered click and for the broadband click. Wave V —Wave I latency differences showed that the rostral conduction time for responses to the 8 kHz FC decreased with age and, for the 1 kHz filtered click (50 dB), remained constant. The early development of basal regions in the cochlea is viewed as insuring the delivery of a wide range of frequencies to rostral segments of the auditory system. The limiting feature of maturation is at rostral sites. The immature auditory system appears to be fully capable of transducing low frequency stimuli, but not high frequencies.     

Auditory brain stem responses in preterm infants: evidence of peripheral maturity

This study explored further the relationship between peripheral and central auditory maturation on the basis of the auditory brain stem response. Auditory brain stem responses were recorded in preterm infants and adults to rarefaction and condensation click stimuli transduced through insert Tubephones. Infant recordings presented a triphasic waveform preceding wave I similar to that of the cochlear receptor potentials seen with adults during electrocochleography. Wave I latency and amplitude were found to be equivalent to those of adult subjects. Moreover, neither latency nor amplitude variability among infant wave I responses was found to be any greater than adults. Latencies of waves III and V, however, exhibited the expected differences relative to the adult comparison group. When the indirect evidence of cochlear receptor potentials in the infant are viewed adjacent to the observations that their ABR wave I latency, amplitude, and variability were entirely consistent with those of young adults, the data lend strong support for peripheral auditory electromaturity. These data are discussed relative to previously published reports of prolonged wave I latency in the infant which was attributed either to middle ear effects or immaturity of the cochlea and first order VIIIth nerve neurons.     

The combined effects of forward masking by noise and high click rate on monaural and binaural human auditory nerve and brainstem potentials

OBJECTIVE: To study effects of forward masking and rapid stimulation on human monaurally- and binaurally-evoked brainstem potentials and suggest their relation to synaptic fatigue and recovery and to neuronal action potential refractoriness. METHODS: Auditory brainstem evoked potentials (ABEPs) were recorded from 12 normally- and symmetrically hearing adults, in response to each click (50 dB nHL, condensation and rarefaction) in a train of nine, with an inter-click interval of 11 ms, that followed a white noise burst of 100 ms duration (50 dB nHL). Sequences of white noise and click train were repeated at a rate of 2.89 s(-1). The interval between noise and first click in the train was 2, 11, 22, 44, 66 or 88 ms in different runs. ABEPs were averaged (8000 repetitions) using a dwell time of 25 micros/address/channel. The binaural interaction components (BICs) of ABEPs were derived and the single, centrally located equivalent dipoles of ABEP waves I and V and of the BIC major wave were estimated. RESULTS: The latencies of dipoles I and V of ABEP, their inter-dipole interval and the dipole magnitude of component V were significantly affected by the interval between noise and clicks and by the serial position of the click in the train. The latency and dipole magnitude of the major BIC component were significantly affected by the interval between noise and clicks. Interval from noise and the click's serial position in the train interacted to affect dipole V latency, dipole V magnitude, BIC latencies and the V-I inter-dipole latency difference. Most of the effects were fully apparent by the first few clicks in the train, and the trend (increase or decrease) was affected by the interval between noise and clicks. CONCLUSIONS: The changes in latency and magnitude of ABEP and BIC components with advancing position in the click train and the interactions of click position in the train with the intervals from noise indicate an interaction of fatigue and recovery, compatible with synaptic depletion and replenishing, respectively. With the 2 ms interval between noise and the first click in the train, neuronal action potential refractoriness may also be involved.     

Effect of click polarity on ABR threshold

This study investigated the effects of click polarity on threshold detectability (threshold level in dB SL) of the auditory brain stem response (ABR). ABRs were obtained from 10 normally hearing adult subjects in response to rarefaction and condensation clicks presented from 0 to 10 dB SL in 2 dB steps. An objective response signal-to-noise estimator, known as Fsp, was the dependent variable. ABR detectability functions (Fsp by dB SL) were not significantly influenced by click polarity. Conclusions can only be drawn for normally hearing adults. For this population, click polarity does not affect threshold detection with the ABR.     

Effect of click spectrum and polarity on round window N1N2 response in the rat

The effect of the duration of click stimuli on the compound action potential recorded from the round window in the rat and the effect of low-pass filtering of short click sounds were studied. Thus the intensity functions of the round window N1 potential have a two-segment course and there is a difference in the response to rarefaction and condensation clicks, depending upon the content of low-frequency components in the click stimulus. The intensity function of the rat's response to broadband clicks does not show the same two-segment course as has been reported in experiments in other animals, and there is little difference between the response to condensation clicks and that to rarefaction clicks in this animal. However, when the duration of the click is increased or when broadband clicks are subjected to low-pass filtering, the intensity functions in response to condensation clicks do show a change in course, while the response to rarefaction clicks remains essentially unchanged. A similar change in the response to a broadband click can be induced by adding a low-pass-filtered click to the broadband click. The response to such a combination is not only a linear summation of the neural response to the individual components of the stimuli and the cochlear microphonics, but the low-frequency components that are added also affect the response to the broadband click, mainly by reducing the amplitude of the response.     

健康成年人高通噪声掩蔽听性脑干反应研究

目的 研究健康成年人高通噪声掩蔽听性脑干反应(又称为耳蜗积水掩蔽分析程序,the cochlear hydrops analysis masking procedure,CHAMP)的特点,探讨CHAMP各参数在诊断膜迷路积水中的应用价值.方法 应用Bio-logic听性诱发电位系统对20名(40耳,其中男女各10名)耳科正常人记录由6种声信号所诱发的听性脑干反应(auditory brainstem response,ABR),包括:单独使用短声及截断点分别为8、4、2、1、0.5 kHz同侧高通滤过粉红噪声(high-pass masking pink noise)掩蔽下的短声信号.结果 高通滤过粉红噪声掩蔽下的短声所诱发的ABR V波潜伏期较短声ABR长,短声+8、4、2、1、0.5 kHz高通滤过粉红噪声的V波潜伏期延迟平均((x)±s,下同)分别为(0.30±0.18)、(0.97 ±0.43)、(1.65±0.64)、(3.21±0.56)、(4.66±0.37)ms.短声+0.5 kHz高通滤过粉红噪声诱发的ABR与短声ABR的复合振幅比为0.95 ±0.11.结论 对于膜迷路积水,CHAMP可能是一种很有前景的诊断方法,V波潜伏期延迟可作为判定CHAMP正常与否的标准,但复合振幅比的特异性有待进一步验证.

Abstract：

Objective To study the characteristic of the cochlear hydrops analysis masking procedure ( CHAMP) in normal adults, and to evaluate the diagnostic values of its parameters for logic auditory evoked potential system: clicks presented alone (unmasked condition) and clicks presented with ipsilateral pink noise high-pass filtered at 8 , 4, 2, 1, and 0. 5 kHz respectively. Results The wave V latency of ABR to the high-pass masking pink noise clicks were longer than ABR to clicks alone. The latency delays of wave V for clicks presented with ipsilateral pink noise high-pass filtered at 8 , 4, 2, 1, and 0.5 kHz compared to clicks alone were (0.30 ±0.18), (0.97 ±0.43), (1.65 ±0.64), (3.21 ±0.56),(4. 66 ± 0. 37 ) ms respectively. The complex amplitude ratio between ABR to click + 0. 5 kHz high-pass noise and click alone was 0.95 ±0.11. Conclusions CHAMP is a promising diagnostic method for membranous labyrinth hydrops, and the latency delay of wave V might be used as the normal criterion. The specificity of the complex amplitude ratio need furthur evaluation in clinical work.