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87 Cards in this Set
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- Back
ABR |
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 |
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Who discovered the ABR? When? |
Don Jewett in the late 1960s |
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What about the first publication? |
in 1971 written by Jewett and Wilson |
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ABR components |
stimulus major peaks in the waveform response latency |
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ABR atimulus |
high-intensity transient acoustic signal |
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waveforms |
by Roman numerals Waves I through Waves V |
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response latency |
within a 5 to 6 ms period following the presentation of a high intensity stimulus |
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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 |
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What do peaks represent in ABR? |
synchronous neural discharge from dipole generators located at various way stations along the auditory pathway |
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Where do waves I, II, and III arise? |
from auditory pathways IPSILATERAL to the side of stimulation |
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Where does wave V arise? |
it reflects activity in midbrain auditory structures CONTRALATERAL to the stimulus |
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What do latencies for later conponents depend on? |
synaptic activity in major brainstem auditory centers |
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In pots with normal hearing, what is click evoked ABR mostly dependent on? |
activation of the higher frequency (3 kHz) region of the cochlea |
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optimal ABR stimulus |
brief duration (e.g., 0.1 ms) click because it enhances synchronous neural activity |
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tone burst stimuli are also effective in eliciting the ABR |
yes yes yes yes yes |
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ABR stimulus rate |
20/second or even faster is effective in evoking the ABR |
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As rate increase... |
ABR latency increases ABR amplitude decreases |
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Rate influences ABR latency more fore... |
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As stimulus intensity increases... |
response latency values decrease response amplitude increases |
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When intensity is above 70 dB nHL |
latency remains stable amplitude continues to increase |
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ABR stimulus polarity |
rarefaction condensation alternating |
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rarefaction |
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condensation |
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alternating |
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What are repetitions/sweeps used to? |
to extract and enhance AERs from background neurologic activity |
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How many sweeps to use? |
enough to produce an adequate SNR for confident ABR wave analysis (no more or no less) |
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minimally recorded ABR electrode placement |
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ABR acquisition is detected within post-stimulus analysis time of.... |
15 ms
shorter or longer analysis times may be appropriate under certain test conditions |
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band-pass filter settings |
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high pass filter |
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low pass filter |
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parameters for evaluating ABR |
absolute latency interwave latency intervals amplitude |
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know this for sure |
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ABR absolute latency is time between... |
stimulus onset and the peak ABR waveforms |
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ABR absolute latency norms are recorded with a stimulus that is |
a click stimulus of 75 dB above normal threshold |
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when should absolute latencies occur? |
Wave I: 1.6 ms Wave III: 3.7 ms Wave V: 5.6 ms |
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absolute latency is great in ____ and shorter in ___ |
newborns females |
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latencies of ABR waves increase as the stimulus ___ |
decreases |
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ABR latency-intensity function |
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ABR interwave latency |
the time between peaks in the waveform |
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interwave latency times |
Waves I-III and III-V: 2.0 ms Waves I-V: 4.0 ms |
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What information is provided from interweave latency |
about the auditory pathways
useful in the neuroldiagnostic ABR approach |
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I-III interwave latency reflects... |
VIII nerve and lower brainstem auditory pathways |
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III-V interwave latency reflects... |
brainstem activity |
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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 |
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range of normal ABR amplitudes |
between .1 to 1.0 microvolts |
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amplitudes will decrease as the stimulus intensity ____ |
decreases |
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the "area under the curve" represents |
the total amount of neural energy contributing to the evoked response |
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What has been proposed as the "area under the curve" |
alternative method of quantifying the response of an AMLR |
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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 |
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FFT can be performed on ABR waveforms |
yep |
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what does ABR spectral analysis allow? |
the major frequencies within the AEP to be separated and analyzed after the waveform has been recorded |
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according to Hall, most energy in an ABR is (low/high) frequency |
low
very little energy is contained above 2 kHz in an ABR waveform |
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other frequencies with prominent energy regions include |
500 to 600 Hz 900 to 1100 Hz |
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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 |
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What is the purpose of the FFT? |
to demonstrate that most energy in an ABR is low in frequency, below 1500 Hz |
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Specifically, where is most energy found? |
below 500 Hz (most concentrated around 30-40 Hz) |
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ABR spectral analysis |
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ABR Fsp values are used to determine what |
the quality of the evoked response in relationship to the noise in the recording |
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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 |
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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 |
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higher the Fsp |
the better the ABR response can be considered |
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what Fsp values can be considered a response |
value of 1 to 3 |
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when is Fsp calculated? |
for every 250 sweeps |
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ABR Fsp values can be used to limit... |
the number sweeps needed to record an accurate ABR response at higher intensities |
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what can ABR Fsp be used to determine |
when more averaging will not produce a response |
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ABR Fsp can reduce test time when using what? |
the minimum number of sweeps when recording AEPs |
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ABR Fsp can be used to increase... |
objectivity and limit the interpretive errors in clinical AER measurement |
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the response is not seriously affected by.. |
subject state of arousal (sleep)
most drugs, including sedatives and anesthetic agents |
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age influences on ABR |
latency increases
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ABR and infants waveform |
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gender influences on ABR |
females have
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clinical importance of gender influences |
balance males and females when establishing normative data |
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body temperature influencing ABR |
consider for patients with
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ABR normal variations |
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for the neurodiagnostic application of ABR, the peripheral system is assumed to... |
function properly and the retrocochlear system is examined |
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clinical applications of neurodiagnostic ABR |
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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 |
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response parameters for neurodiagnostic ABR |
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stimulus parameters for neurodiagnostic ABR |
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When estimating hearing thresholds or auditory sensitivity, it is assumed |
that the auditory pathways are intact |
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clinical applications for threshold ABR |
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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 |
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faster click rate for threshold ABR
longer analysis window for threshold ABR |
30 to 70 per sec
20 to 25 ms |
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response parameters for threshold ABR |
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stimulus parameters for threshold ABR |
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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) |