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87 Cards in this Set

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a far-field recording of neurologic activity of the VIII nerve and brainstem auditory pathways that occurs over the first 10 to 15 sec after a suitable sound stimulus has been delivered to the ear

Who discovered the ABR? When?

Don Jewett in the late 1960s

What about the first publication?

in 1971 written by Jewett and Wilson

ABR components


major peaks in the waveform

response latency

ABR atimulus

high-intensity transient acoustic signal


by Roman numerals

Waves I through Waves V

response latency

within a 5 to 6 ms period following the presentation of a high intensity stimulus

Generators of waves

Wave I: distal VIII nerve

Wave II: proximal (brainstem portion) of the VIII nerve

Later waves: have multiple generators within the auditory brainstem

What do peaks represent in ABR?

synchronous neural discharge from dipole generators located at various way stations along the auditory pathway

Where do waves I, II, and III arise?

from auditory pathways IPSILATERAL to the side of stimulation

Where does wave V arise?

it reflects activity in midbrain auditory structures CONTRALATERAL to the stimulus

What do latencies for later conponents depend on?

synaptic activity in major brainstem auditory centers

In pots with normal hearing, what is click evoked ABR mostly dependent on?

activation of the higher frequency (3 kHz) region of the cochlea

optimal ABR stimulus

brief duration (e.g., 0.1 ms) click because it enhances synchronous neural activity

tone burst stimuli are also effective in eliciting the ABR

yes yes yes yes yes

ABR stimulus rate

20/second or even faster is effective in evoking the ABR

As rate increase...

ABR latency increases

ABR amplitude decreases

Rate influences ABR latency more fore...

  • premature than term neonates
  • young children (under 18 mo) than older children
  • Older children (up to 13 yrs) than adults

As stimulus intensity increases...

response latency values decrease

response amplitude increases

When intensity is above 70 dB nHL

latency remains stable

amplitude continues to increase

ABR stimulus polarity





  • pressure wave in a negative direction
  • produced by movement of the transmitter diaphragm AWAY FROM the TM
  • activation of VII nerve caused by upward movement of BM secondary to rarefaction polarity stimulus
  • activates of DEPOLARIZES cochlear hair cells
  • creates shorter latencies and greater amplitude


  • positive electrical pulses
  • produced by movement of the transmitter diaphragm TOWARD the TM
  • may produce HYPERPOLARIZATION of hair cells


  • switching between condensation and rarefaction polarities at subsequent stimulus presentations
  • can produce out-of-phase responses (reduced amplitude and abnormal responses)

What are repetitions/sweeps used to?

to extract and enhance AERs from background neurologic activity

How many sweeps to use?

enough to produce an adequate SNR for confident ABR wave analysis (no more or no less)

minimally recorded ABR electrode placement

  • one electrode located either at the top of the head (vertex) or high in the midline on the forehead
  • another electrode located near the ear (earlobe) on the stimulated side
  • a ground (common) electrode can be located anywhere (low forehead most common)

ABR acquisition is detected within post-stimulus analysis time of....

15 ms

shorter or longer analysis times may be appropriate under certain test conditions

band-pass filter settings

  • 30 or 100
  • 1500 or 3000 Hz

high pass filter

  • as cutoff is increased from a low frequency (0.1 Hz) to higher frequency (500 Hz)
  • wave components (wave V) are reduced in amplitude and distortions in latency often are noted (poor morphology of waveforms)

low pass filter

  • decreasing cutoff frequency from a very high value (10,000 Hz) to 3000 Hz eliminated noise without distorting ABR latency and amplitude
  • ABR contains almost no spectral energy above 2 kHz

parameters for evaluating ABR

absolute latency

interwave latency intervals


know this for sure

ABR absolute latency is time between...

stimulus onset and the peak ABR waveforms

ABR absolute latency norms are recorded with a stimulus that is

a click stimulus of 75 dB above normal threshold

when should absolute latencies occur?

Wave I: 1.6 ms

Wave III: 3.7 ms

Wave V: 5.6 ms

absolute latency is great in ____ and shorter in ___



latencies of ABR waves increase as the stimulus ___


ABR latency-intensity function

ABR interwave latency

the time between peaks in the waveform

interwave latency times

Waves I-III and III-V: 2.0 ms

Waves I-V: 4.0 ms

What information is provided from interweave latency

about the auditory pathways

useful in the neuroldiagnostic ABR approach

I-III interwave latency reflects...

VIII nerve and lower brainstem auditory pathways

III-V interwave latency reflects...

brainstem activity

I-V interwave latency reflects...

a representation of overall activity from VIII nerve and the nuclei and tracts of the brainstem responsive to auditory stimuli

range of normal ABR amplitudes

between .1 to 1.0 microvolts

amplitudes will decrease as the stimulus intensity ____


the "area under the curve" represents

the total amount of neural energy contributing to the evoked response

What has been proposed as the "area under the curve"

alternative method of quantifying the response of an AMLR

How is under the curve measured

by examining amplitudes as a function of time

by marking the negative peak of one wave to the next negative peak in the waveform

can only be measured using both positive or both negative peaks

FFT can be performed on ABR waveforms


what does ABR spectral analysis allow?

the major frequencies within the AEP to be separated and analyzed after the waveform has been recorded

according to Hall, most energy in an ABR is (low/high) frequency


very little energy is contained above 2 kHz in an ABR waveform

other frequencies with prominent energy regions include

500 to 600 Hz

900 to 1100 Hz

Why is it important to consider FFT in spectral analysis

consider it when setting the high and low pass filters for an ABR recording in order to preserve as much as the ABR waveform as possible

What is the purpose of the FFT?

to demonstrate that most energy in an ABR is low in frequency, below 1500 Hz

Specifically, where is most energy found?

below 500 Hz (most concentrated around 30-40 Hz)

ABR spectral analysis

ABR Fsp values are used to determine what

the quality of the evoked response in relationship to the noise in the recording

What is the premise of Fsp values

the evoked potential to the auditory stimulus is rather constant (in amplitude, latency, and morphology) from presentation while is noise in recording is more random

ABR Fsp values represent...

a single point in the recording

gives the probability of the response actually being an ABR response

not ambient background activity

higher the Fsp

the better the ABR response can be considered

what Fsp values can be considered a response

value of 1 to 3

when is Fsp calculated?

for every 250 sweeps

ABR Fsp values can be used to limit...

the number sweeps needed to record an accurate ABR response at higher intensities

what can ABR Fsp be used to determine

when more averaging will not produce a response

ABR Fsp can reduce test time when using what?

the minimum number of sweeps when recording AEPs

ABR Fsp can be used to increase...

objectivity and limit the interpretive errors in clinical AER measurement

the response is not seriously affected by..

subject state of arousal (sleep)

most drugs, including sedatives and anesthetic agents

age influences on ABR

latency increases

  • under 18 months
  • over the age of 60 years

ABR and infants waveform

gender influences on ABR

females have

  • shorter latency values
  • larger amplitudes

clinical importance of gender influences

balance males and females when establishing normative data

body temperature influencing ABR

consider for patients with

  • infection (high temp) - latency decreased
  • coma, alcohol, anesthesia (low temp) - latency decreased
  • severe hypothermia - ABR disappears

ABR normal variations

for the neurodiagnostic application of ABR, the peripheral system is assumed to...

function properly and the retrocochlear system is examined

clinical applications of neurodiagnostic ABR

  • neurodiagnosis of VIII nerve or auditory brainstem dysfunction
  • monitoring VIII nerve and auditory brainstem status intraoperatively during surgery potentially auditory system
  • diagnosis of auditory neuropathy

neurodiagnostic ABR

click rate?

analysis time?

stimulus level?

slower click rate - 10 to 20 per sec

10 to 12 ms analysis time

70 to 100 dB HL stimulus levels

response parameters for neurodiagnostic ABR

  • electrode array (Cz/A1 and Cz/A2)
  • time window (15 ms)
  • delay (-3 ms)
  • low freq filter (30 Hz)
  • high freq filter (3 kHz)
  • sensitivity (50 uV)
  • repetitions (2k at max)

stimulus parameters for neurodiagnostic ABR

  • type (click)
  • duration (100 usec)
  • intensity (80 dB nHL)
  • polarity (rarefaction)
  • rate (11.4/sec)

When estimating hearing thresholds or auditory sensitivity, it is assumed

that the auditory pathways are intact

clinical applications for threshold ABR

  • newborn infant auditory screening
  • estimation of auditory sensitivity in infants and DTT children, including frequency specific information at audiometric frequencies

with advent of UNHS, ABR has assumed an essential role as...

an électrophysiologie technique for estimating auditory threshold in infants at risk for hearing loss

faster click rate for threshold ABR

longer analysis window for threshold ABR

30 to 70 per sec

20 to 25 ms

response parameters for threshold ABR

  • electrode array (Cz/A1 and Cz/A2)
  • time window (18 ms)
  • delay (-3 ms)
  • low freq filter (30 Hz)
  • high freq filter (3 kHz)
  • sensitivity (50 uV)
  • repetitions (2k at max)

stimulus parameters for threshold ABR

  • type (click or tone burst)
  • duration (100 usec)
  • intensity (80 dB nHL - then decreases in intensity)
  • polarity (rarefaction)
  • rate (31.4/sec at max)

clinical limitations for ABR

with click stimuli, the ABR only estimates hearing sensitivity int he 1000 to 4000 Hz region and now for lower frequencies (can also be evoked with frequency specific signals)

the ABR is not a test of hearing (evoked with simple acoustic signals and is generated mostly by onset neurons)

ABR provides no information on auditory function above the level of the brainstem (auditory cortex)