This document discusses various parameters for auditory brainstem response (ABR) testing, including stimulus type, intensity, and presentation rate. It describes advantages and disadvantages of different transducer types (insert earphones, supra-aural earphones, bone vibrators) and stimulus types (clicks, tone bursts, chirps, speech). Factors that influence ABR waveforms like latency and amplitude are discussed in relation to stimulus intensity, frequency, duration, and envelope. Guidelines are provided for optimal application of different stimulus parameters in clinical ABR testing.

1. Chapter 5
Auditory Brainstem Response: Stimulus
Parameters
1

2. Insert earphones advantages
• Increased inter-aural attenuation
• Increased ambient noise reduction
• Reduced possibility of collapsing ear canals in infants
• Increased patient comfort
• More precise placement
• Flatter frequency response
2

3. Insert earphones advantages…
• Reduced transducer ringing,
In temporal waveform in response to transient stimulation
• Reduced stimulus artifact,
artifact with single polarity stimuli at supra-aural earphones at high
intensity levels(ECochG CM and wave I)
• Aural hygiene
• Sterile test conditions
• Option for TIPtrode use(ABR wave I) 3

4. 4

5. Disadvantage
Higher than intended sound pressure levels
• excessively high sound stimulation of the ear at maximum stimulus
intensity levels begin from moderate-to-high intensity
level
• a failure in detection of mild hearing loss and underestimation of
other degrees of hearing loss not a major factor in
routine ABR measurement
5

6. Supra-Aural Earphones
• Headband
• Collapsing of the ear canal
• No way to disinfect or sterilize
• Undesirable temporal and spectrum characteristics
6

7. Bone Vibrators
• Dd
7

8. Click stimulus
• click stimuli are most closely correlated with pure tone hearing
thresholds in the region of 2000 Hz to 4000 Hz.
• two reasons for the dominance of high frequency cochlear activation
for click-evoked ABRs
8

9. Chirp Click Stimulus
• Rapidly sweep of sound
• to produce simultaneous displacement maxima along the cochlear
partition by compensating for frequency-dependent traveling-time
differences
9

10. Traveling wave
• ABR wave V latency for stimulation in the region around 500 Hz is
about 5-ms longer than latency for 4000 Hz stimulation
10

11. Chirp Click Stimulus effects on ABR
• Shift in wave V latency
• Enhanced amplitude of the chirp-evoked ABR is
1) More confident identification
2) More accurate estimations of thresholds
3)Decreased test time required for recording ABRs
11

12. Larger amplitude of chrip evoked ABR ??
• Low to moderate intensity levels
How about High intensity levels?
• Intensity level ------ duration of chrip stimulus cochlear mechanics,
level dependent changes cochlear travelling waves, delays
12

13. • Level Specific Chrip (LS chrip ) ....based on Level Specific delay model
Chrip applications:
• Patients with HL
• Retrocochlear auditory dysfunction
• Bone conduction ABR
• ASSR
• Cortical evoked responses
13

14. Bone Conduction Click Stimulation
Historical Perspective
• Essential component of the test battery for auditory assessment of
infants and young children
• Contrary to expectations for adult subjects, latencies for ABR wave I,
wave III, and wave V were shorter by abut 0.30 to 0.45-ms for bone
conduction stimuli than for air-conduction stimuli.
• In the immature cochlea, responsiveness to low-frequency stimuli
develops initially in the basal regions
• the importance of bone oscillator placement on effective intensity
level, on ABR latency and, indeed, for successful measurement of
bone conduction ABRs
14

15. • low cutoff for the high pass filter (30 Hz) for successful bone
conduction ABR measurement
• Latencies varied as a function of: 1) air- versus bone-conduction
stimulation, 2) vibrator placements for bone conduction, and, as
expected, 3) age of the patient
• very unique latency versus placement pattern observed for the
neonates. For temporal bone placement, wave V latency was
markedly shorter than for the other two bone vibrator locations and
was slightly shorter than even the air-conduction latency values.
• inter-aural attenuation value of 0 dB in adults, 15 to 25 dB in 1-year-
old children, and as much as 25 to 35 dB in neonates
15

16. • On the average, bone conduction wave V latency was 0.5 -ms greater
than wave V for air conduction at equal sensation levels.
• The closest association between ABR versus behavioral threshold was
for a high frequency pure-tone average, the PTA2 (1000 + 2000 +
4000 Hz / 3).
• a clear difference in ABR thresholds for air- versus bone conduction in
newborn infants as a function of test time after birth. The age-related
difference in air conduction thresholds was highly significant, but
there was no difference in the bone conduction thresholds for the
two groups
16

17. Solving the Masking Dilemma
• wave I component observed from an electrode located on or near the
ear ipsilateral to the stimulus originates from the ipsilateral 8th
cranial nerve
• no peak corresponding to the ipsilateral wave I in the same latency
region in the contralateral waveform
17

18. Tone Burst versus Click Stimuli
• Tone burst stimuli presented via bone conduction used for frequency-
specific estimation
• the accuracy of frequency-specific estimation of cochlear status with bone
conduction tone burst stimuli
• ABR with frequency-specific bone-conduction stimuli was clinically feasible
for assessing inner-ear status in infancy and in older children, and that
results were comparable to behavioral bone-conduction thresholds
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19. Tone Burst versus Click Stimuli
• test time constraints
• decisions regarding management, including amplification
• clinical necessity of differentiating conductive versus sensory hearing
loss
• referral for medical consultation and possible management
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20. Effect of Age
• Same concern about newborn infants, particularly for lower tone
burst stimuli
• infants age 3 months or less
• calibration of BC transducers using an artificial mastoid
• ABR wave V with bone conduction stimulation ;of -10 to 10 dB nHL
and air conduction ABR thresholds ;20 to 40 dB nHL
• correction factors of 28 dB for a 500 Hz tone burst stimulus and 20 dB
for a 1000 Hz stimulus
20

21. Wrap Up on Bone Conduction Stimuli
reluctance of clinicians to adapt this approach
• The real maximum effective intensity level ;30-40 dB
• Electromagnetic energy radiating and stimulus artifacts
• the discrepancy between the most common frequency region for
conductive hearing loss versus the frequency region producing an
ABR
• Early papers cite the masking dilemma
21

22. Sensorineural Acuity Level (SAL) Test with ABR.
• ease of calibration and minimal or no contribution from the non-test
ear.
• reliable predictor of bone-conduction threshold
• The SAL approach has also been used with the ASSR
22

23. Importance of Frequency-Specific Stimulation
• The frequency specificity of a stimulus is indirectly related to duration
• A direct relationship between duration of a stimulus and duration of
response
• Diagnostic procedure after screening
• Hearing aid fitting
23

24. Introduction to Frequency-Specific ABR
Measurement
• estimation of auditory thresholds in infants and young children
• underestimate or overestimate sensory hearing loss
• click-evoked ABR + ABR for 500 Hz TB
• ABR minimally should be performed with tone burst stimuli at 500 Hz,
4000 Hz, and either 2000 Hz and/or 1000 Hz
• behavioral hearing testing in addition to other objective auditory
measures like aural immittance measures and otoacoustic emissions
(OAEs) 24

25. Tone Burst Stimuli advantaged
• clinically feasible
• Straightforward
• Brief test time
• available on all commercial evoked response systems
• low- to moderate-intensity levels can produce frequency-specific
• Appropriate envelopes and onset ramping in tone burst stimuli ;
adequate frequency-specificity
• Simple and quick recording 25

26. Clinical guidelines
2007Joint Committee on Infant Hearing
(JCIH,2007)
26

27. Tone Burst Chirp Stimuli.
• tone bursts are octave band stimuli centered around traditional
frequencies of 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz
• shorter latencies
• larger amplitudes over 50%
• shorter test time
• more accurate detection of wave V
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28. Speech Stimuli
• ABR and a frequency following response (FFR) with speech stimuli
• investigating the neural representation of speech processing at the
brainstem and for documenting neural plasticity with auditory training
• The 40-ms speech stimulus (/da/)
• insert earphones
• Alternating polarity
• Intensity level : 80 dB
• trains of four stimuli with
• interval of 12-ms
• Subjects are distracted during the ABR
28

29. Paired Clicks
• two closely spaced click stimuli
• delta t= time between the two from 4.0 ms down to only 0.1ms
• An action potential + excitatory post synaptic potentials (EPSPs)
• derived response = the waveform for pair of clicks- the waveform for
the first standard click
29

30. Filtered Clicks
• Not widespread clinical application
• Conventional wide-spectrum or broadband click is passed through a
series of filters
• produce transient stimuli with energy centered at desired
frequencies
30

31. Stimulus Offset ABR
• Two neuron types:
onset neurons and offset neurons
• ABR is thought to reflect synchronous firing of onset neurons.
For a click stimulus, with duration of 0.1 milliseconds, stimulus onset
and offset occur almost simultaneously
and identification of any offset contribution to the response is
impossible.
31

32. • are not as robust or as reliably
• Amplitude is 70 to 80% smaller with onset ABRs.
• threshold is about 10 to 20 dB higher
• The offset response is recorded with a longer duration stimulus of 10-
ms duration or longer to prevent overlapping with the invariable
onset response
32

33. Modulated Tones
• frequency-modulated and amplitude modulated stimuli
• These techniques theoretically : increase efficiency of ABR data
collection and reduce test time
• but clinical confirmation is lacking and the techniques are not
included in typical ABR protocol
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34. Stimulus Trains , TB trains
In ABR
• abrupt onset and
• brief duration of 4 or 5 cycles
• inter-stimulus intervals of 25-ms
In ALR
• rise/fall times of 8 to 30-ms
• relatively long plateau durations of 30 to 500-ms
• inter-stimulus intervals of approximately 2.5 seconds.
Trains of TB
• individual tone bursts at intervals of 25-ms serve as the stimuli for the ABR
• trains of tone bursts are presented with an interval of 2.5 seconds between each train
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35. Stimulus Trains advantage and disadvantage
• minimize test time
• reduction in the response amplitude
• prolongation of latency…………………………..MLS
35

36. Plops
• conventional clicks consisting of 100-μsec square wave pulses
• centered around 1000 Hz
• alternating, rarefaction, and condensation polarity
• Lack of the ringing
• added frequency components of a click
• greater absolute latency values for wave I, wave III, and wave V
• similar amplitude of wave V and inter-wave latencies
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37. Noise Stimuli
Goals:
• frequency specificity
• gap detection
• Temporal resolution
Parameters:
• Noise burst duration of > 15-ms
• Gap range of 0-ms to over 100-ms
37

38. • Changes in ABR wave V latency
• absence of an ABR
• A detectable ABR: as short as 8-ms
• Disappearing ABR : silent gap is a short as 4-ms
• sloping high frequency sensorineural hearing loss:
higher gap detection thresholds
• We need Longer silent gaps in both infants and
older adult
38

39. MASKING
• frequency response of the transducer
• broadband noise (BBN) is a good option for: broad-spectrum click
• narrow band masking noise for tone burst signal
39

40. Masking Not Always Needed in ABR
Measurement
• abnormal
• prolonged latency
• no wave I component
• Decrement of amplitudes
Profound Hl Normal hearing
95 35
40

41. When is Masking Needed in ABR
Measurement?
Failure
to recognize the abnormally delayed ABR as a crossover response could
lead to misinterpretation of
findings and underestimation of the degree of hearing impairment in
the poorer ear
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42. Does Masking Affect Auditory Evoked Responses
Arising from the Central Nervous System?
• Animal studies indicate that central masking is mediated in auditory
• regions in the caudal brain stem.
• no clear effect of central masking on the ABR
• Contralateral masking of the non-test ear less than 70 dB HL does not
produce consistent alterations in ABR latency or amplitude.
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43. DURATION of click stimulus
• Click duration have no marked influence on ABR latency or amplitude.
• no latency change for stimulus durations from 0.25 to 100-μsec.
• 0.2-ms prolongation in latency for durations from 100 to 400-μsec.
• specified click duration clinical ABR measurement
Factors:
• frequency content
• envelope of the rising portion of the stimulus
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44. DURATION of TB stimulus
• Typically defined in terms of the total number of cycles rather time
• tone burst duration :rise time, plateau, and fall time.
• “2-1-2 paradigm and “2-0-2 paradigm
44

45. Results of increasing rise time TB:
• slow wave component of the ABR
• Identification of earlier ABR waves is difficult when rise time exceeds
5-ms.
• reduction in the amount of neural units that fire synchronously
• traveling wave is slower, there is an increased contribution of the
more apical regions of the cochlea to the ABR
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46. Tone-Burst Envelopes
• The envelope of the tone burst
• What is the optimal stimuli?
• Frequency specificity
• Place specificity
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47. INTENSITY
Calibration of Transient Stimulus Intensity
• physical calibration(peRETSPL)
• biologic verification of stimulus intensity to achieve our clinic
normative data
47

48. New Directions in Calibration of Stimulus
Intensity
• Currently clinical in-the-ear documentation of click and tone burst
stimulus intensity is not uniformly available from manufacturers of
ABR systems.
• One manufacturer offers an innovative approach ;VivoCheck™
• verification of stimulus intensity
• also polarity.
• electromagnetic interference in the test environment
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49. Effect of Stimulus Intensity on ABR
• latencies of ABR waves decrease and amplitudes increase as stimulus
intensity increases.
• Latency of wave V decreases dramatically up to intensity levels of
about 70 to 75 dB nHL,
• amplitude of wave V steadily increases
• amplitude of ABR wave I also increases
49

50. Wave V Latency-Intensity Function
• more variability :in lower intensity
• up to approximately 60 dB nHL : 0.50 or 0.60-ms /10 dB
• from 60 to 95 dB nHL: 0.10 to 0.20-ms/10 dB.
• At threshold levels:7.5 to 8.0-ms or greater
50

51. Effect of Stimulus Intensity on ABR Waveforms
• Amplitude:
In normal cases
Amplitude of wave V : 0.50-μV at high levels
wave I: 0.25 to 0.30-μV
V:I amplitude ratio of 1.50
Wave V can be detected in down to 10 dB
Wave I and III : about 25 to 35 dB nHL
• Maximum amplitude of any ABR wave V in
high intensity levels, rarely exceeds 1.0-μV. 51

52. Effect of Stimulus Intensity on ABR Waveforms
• Latency:
In normal cases
In 80 to 85 dB
wave I latency : 1.5-ms
wave III : 3.5-ms
wave V : 5.5-ms
In lower levels
• Inter-wave latency values : 2.0-ms
• I to V interval on the order of 4.0-ms 52

53. Intensity Effects for TB Stimuli.
• Low frequency TB
• High frequency TB
Latency wave V
Lower Intensity-----higher intensity
Higher
Lower
53

54. Physiological Explanations for the Latency-
Intensity Function
• high intensity levels activate the cochlea near the base.
• At the lowest intensity levels the portion of the cochlea representing
frequencies 1000 to 2000 Hz generates ABR
----------------------------------------------------------------------------------------------
1ms delay(8 – 5.5=2.5)
• faster excitatory postsynaptic potentials, or EPSPs
• Different neural generators of slow and fast components of ABR(Dual
component)
• Different kinds of primary fibers, low- and high-sensitivity
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55. RATE OF STIMULUS PRESENTATION
Factors contributing to decisions about rate of stimulus :
• 1) The clinical objective
• 2)Click versus tone burst stimulation
• 3) Interference from electrical artifact
• 4) Developmental age of pediatric patients
diagnostic purposes and bone conduction stimuli: Wave I ; rate up to
about 20 to 25 stimuli per second.
TB ABRs : Wave V; 37 per second or more are appropriate
55

56. Click Stimulus Rate in Normal Adults
• Rates up to approximately 20 to 30/second have little or no effect in
normal hearing adults and children age 18 months and older
• Not similar changes in I & V Amp
• Latency prolongations in all wave
Components(for wave I discrepancies)
• Constant inter-wave latencies
• waves II, III, and IV become less
Identifiable
56

57. Click Stimulus Rate in Infants and Young Children
greatest effect for wave V
incomplete myelinization and reduced synaptic efficiency
• premature
• Term neonates
• younger children under age 18 months
• older children
• older children up to age 13 years
• adults
57

58. Rate and Tone Burst Stimulation
• What is the general guideline for tone Burst ABR?
Slightly slower than those producing deterioration in response quality
and reliability
the range of 27.1/second up to 39.1/second
slow stimulus rate of 11.1/sec versus a faster stimulus rate of
39.1/sec???
58

59. Physiological Bases of Rate Effects
• increased rate on ABR latency versus amplitude
• 1. cumulative neural fatigue and adaptation and incomplete
• Recovery………………………………. not uniform adaptation for all neurons
• 2. dual nature of the ABR
Slow-component was relatively constant /waves I to V decreased in
amplitude.
Latency of each component increased with rate.
59

60. Rate-Related ABR Findings in Auditory
Pathology
• peripheral and central nervous system pathology, including 8th nerve
tumors, epidermoid tumor of the fourth ventricle, mixed central
nervous system diseases, multiple sclerosis ..
Observations: abnormal latency shifts or disappearance of later waves
Etiology: axon de-myelination or neuron synapse disorders
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61. POLARITY
Click Stimuli; 1) rarefaction polarity stimuli are recommended
enhanced amplitude
2) alternating polarity stimulation in bone conduction
minimize interference from stimulus-related artifact
TB
polarity tone burst stimuli are appropriate: researches
a single polarity tone burst stimulus of 500 Hz occasionally produces a
highly consistent periodic waveform with peaks of 1000 Hz
an alternating polarity stimulus appears to eliminate the periodic
waveform revealing a typical ABR
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62. 62

63. Normal adult Subjects
• shorter latency and larger amplitude with rarefaction
• Wave I latency is about 0.07-ms shorter for normal hearing
• decreased latency for wave I but not wave V with rarefaction
• WaveI-V inter-wave latency
• Amplitude of wave I can be larger for rarefaction
• Wave V-to-I amplitude ratio is reduced
63

64. Alternate or rarefaction ??
Advantages:
• physiology-based polarity reversal
• solution because the sequence of each stimulus polarity is not
important
Disadvantages:
• out-of-phase responses
• sometimes an artificially abnormal or absent response in a normal
subject
64

65. Clinical Recommendations
1. traditional approach is measurement replicable ABR
waveforms first for rarefaction polarity and then
condensation polarity
2. current evoked response systems can present stimuli with
alternating polarity…… and then to analyze separately the
waveforms for each of the polarities.
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66. Binaural stimulation
• relationship of the to binaural fusion and sound lateralization
• Originate: The caudal brainstem, specifically the olivary complex
• V amplitude is up to twice the monaural amplitude
66

67. Binaural difference characteristics:
• two positive (P1 and P2)
• two negative (N1 and N2) peaks
in the 4 to 6-ms region.
The major peak (negative)at a latency value slightly greater than for
ABR wave V.
• extremely modest amplitude
• No BD for wave I, wave II, and wave III
67

68. Physiological Basis of Binaural Interaction
The major anatomic regions :
medial nucleus of the trapezoid body
the lateral superior olive
medial superior olive
inferior colliculus.
The anatomic source of the ABR BI component within the brain stem is
unknown.
68

69. Summary
Selection of stimulus parameters directly influences ABR recordings
Cautious manipulation of stimulus parameters based on research
findings and clinical experience can make the differences!
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