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EP TEST 2: ABR PARAMETERS PROTCOLS AND PROCEDURES
Terms in this set (90)
ECochg and ABR are onset responses. What does that mean?
The rapid onset of a transient stimulus generates a synchronous response
Stimulus content other than the onset contributes little or nothing to the response
T/F: Unfiltered clicks offer frequency specificity.
False; they cannot be used to completely define hearing sensitivity
____ msec click activates high frequency potion of the cochlea (1k to 6/8k Hz).
T/F: Apical regions of the cochlea are activated, but do not contribute to the click ABR.
Frequency specificity is directly (inversely) related to ___________.
There is generally a direct relationship between the duration of the response and duration of the stimulus. Give an example of this:
Faster, shorter latency response are best activated by fast, shorter onset stimuli
Efficiency of amplification is maximized by:
obtaining 1-3-6 goals for the frequency range of 500 Hz to 4k Hz
What is the default stimulus duration for many ABR systems:
T/F: Spectral characteristics are most important for neurodiagnostic purposes.
False; for audiologic assessment, but not so much for neurodiagnostic
When the rise time exceeds __ msec, early components become difficult to identify.
If r/f time is too long, the ABR response will be adversely affected
T/F: The click duration DOES have a marked influence on ABR latency and amplitude.
False, does not
Typically, there may be a ____ msec increase in latency for durations between 100 and 400 microseconds.
wide spectrum click passed through a set or series of filters to produce a transient stimulus.
Standard click followed with a second click with manipulation of the inter-stimulus interval
The second click generates a post-synaptic activity bc it is presented before nerve recovery of VIII from the initial stimulation
Derived waveform- waveforms are subtracted
Gaussian shaped impulses centered at 1k Hz. Absolute latencies are greater than for clicks
Designed mathematically to produce simultaneous displacement of the cochlear partition.
In theory, optimizing synchronization across a broad frequency region (more robust than clicks, encompasses energy above 2k Hz)
What type of ABR uses chirps?
What must the time window be when using chirps?
30 msec, bc the stimulus itself is 10 msec
What stimulus gives frequency specific information?
Over 90% os patients have a comparable PT behavioral threshold within ___ dB of the one obtained by tone burst ABR.
What must we be cautious of when using tone bursts?
rise/fall times bc it varies between frequencies and different
Where (at what frequency) are the most consistent r/f times seen?
Simultaneous stimulation and recording of the ABR and ALR by presenting trains of tone pips with an interval of 2.5 seconds between each train
Noise stimuli presentation can be when?
May be presented alone or in the presence of a click or TB
Use of noise stimuli:
to increase frequency specificity OR
to measure processing phenomenon (gap detection)
How is noise stimuli used for gap detection?
Noise burst presented to obtain an initial ABR, then a second noise burst is presented after a silent interval
If the gap is fully processed by the auditory mechanism, then the second ABR will be unchanged
What was developed by Manny Don at House El to be a more sensitive detector of small acoustic neuromas?
In stacked ABR, if all frequency bands are normally represented in the ABR, then adding them will result in an ABR that is equal in amplitude to what?
The original click evoked ABR
If a tumor is present, what is the result?
amplitude sum of the 5 ABRs will be smaller than original click evoked ABR
Nina Kraus and colleagues at NW studied ABR and FFR with ____________, investigating neural representation of speech processing using the stimulus /da/. Found to conventional ABR and a subsequent FFR (frequency following response) at 30 to 40 msec.
Others have used speech to investigate what?
the late cortical auditory potentials
Wave V latency increases by about ___ msec over the range from high intensity levels to threshold.
That is, from 5.5 to 7.5
Wave I latency
about 1.5 msec
Wave III latency
Wave V latency
Interpeak values for I-III
Interpeak values for III-V
Amplitude diminished for all waves an intensity is ________.
At high intensities, Wave V amplitude =
at low intensities =
amplitude ratio =
High intensity signals stimulate the ______ end of cochlea while lower intensity signals tend to activate the _____ areas. This apical shift can produce a 1 msec latency increase.
AS YOU DROP INTENSITY, LATENCY WILL
Latency-intensity change in newborns is in the range of ___ to ___ usec/dB.
30 to 40 (1000 usec = 1 msec)
Rates higher than ______ will generally cause an increase in latency and a decrease in amplitude.
T/F: Wave V amplitude shows less decrement with increasing rate.
Why is rate important with infants?
Fast rate helps us get things done more quickly
Obtain threshold for infants in much faster time frame
Waves I and V retain morphological integrity but II III and IV may become less identifiable or may even disappear at high stim rates of ____ to _____
80 to 100/sec
T/F: There is a direct relationship between maturity of the CNS and the effect of rate on the ABR.
T/F: You do not have to adjust rate for premature babies.
False; premature infants require
Abnormal latency shifts or disappearance of later waves at _______________ (rapid/slow) rates of stimulation may occur with various forms of neuropathy (MS, tumor, hypoxia, other CNS disease).
This may result from cumulative neural fatigue and incomplete recovery of the synaptic transmission process along the auditory pathways
Which polarity produces the shortest latencies?
data is inconsistent
Most consistent finding in the research is a shorter Wave I latency using __________ clicks, although the reverse may occur in some patients.
In which direction does a rarefaction click move the basilar membrane? Opposite for condensation.
Activation of the auditory fibers is caused primarily by upward movement of BM
What are two ways to achieve an alternating composite?
use alternating polarity OR
Collect data with each polarity and sum the two
______________ stimuli should be a part of your assessment to objectively define any potential air-bone gaps
T/F: placement of the bone oscillator does not affect stimulus intensity,.
False; some studies indicate a shorter Wave V latency for temporal bone placement over frontal or occipital lobes.
Inter-aural attenuation in neonates may be as much as ___ to ___ dB with the temporal bone site. Why is this?
25 to 35
It is not fully fused with other areas of the cranium (no direct route of transmission to the NTE cochlea
T/F: bone conduction testing is underutilized.
The maximum effective level of BC oscillators is _____ dB nHL.
Usually, an air conduction ABR requires ____ to ___ dB stimulus greater than the behavioral hearing threshold level.
15 to 20
The effective range for determining potential air-bone difference is rather small. How small?
55-20 or 30-40 dB
Another problem is the amount of stimulus related artifact when a mastoid placement is used for the electrode and a single polarity stimulus is used. What would be remedies for this?
earlobe placement for the inverting electrode and alternating polarity
T/F: Under use of bone conduction testing can be contributed to the fear of the masking dilimma.
The presence of a clear Wave I with a normal latency function from the ipsi electrode array is strong evidence that this event is not coming from the NTE. Remember that IA will be enhanced in neonates due to incomplete fusion
Binaural Wave V amplitude to monaural ratio:
1.5 to 2
T/F: there have been some reports of a lack of the normally expect ABR amplitude enhancement for binaural stimulation with various disorders of the CNS.
but there is controversy over the clinical use of binaural stimulation
T/F: Time window should be the same for Neurodiagnostics and estimation of threshold.
What things can cause Wave V to exceed 6 msec?
severe conductive impairment
stimulus level near threshold
sever aud brainstem dysfunction
What is the adjustment that the system automatically makes for inserts?
what should the length of the typical pre-stimulus?
10% of total epoch
In this case, your time window must be at least 15 msec in order not to reduce the available recording window (pre-stimulus is subtracted from total)
As analysis time increase, what happens to stimulus rate?
It decreases. they are inversely related
If the time window is 10 msec, the max rate is 100/sec
If the time window is 15 sec, the max rate is 67/sec.
What time window do we need for MS patients and why?
Shorter, to tax the system
Advantages of tiptrodes:
better Wave I
better ID of early components
Disadvantages of tiptrodes:
Manipulation (special cable)
cant run a horizontal array on adult and get a decent response
Typical recording montage for ABR:
Non-inverting- CZ (this gives greatest amplitude; but can also be put on FZ)
Inverting- ipsilateral earlobe (stimulated side)
What are some advantages of high forehead placement that might outweigh the amplitude enhancement of the vertex site?
brain or scalp injuries with bandages
Be careful with fontanel in neonates
What is the vertex/forehead to non cephalic called?
What is the tradeoff when using a non cephalic inverting electrode placement?
Wave V amplitude may actually be increased bc IV/V separation may occur
Could possibly be beneficial in threshold estimation
Sites for the ALGO:
nape of neck, either side or the neck or thorax (specifically the sternum)
What are the effects of a contralateral electrode array?
Amplitude of Wave I is larger which may provide advantage for ID of Wave I
Used with ECochg
T/F: the ABR response remains constant and time locked to the stimuli and noise is stationary and random.
Lower stimulation levels will generally require ______ (more or less) averaging time.
What do we use averaging for?
Enhancing embedded EP
If filter is manipulated from 100 Hz to 300 Hz, what happens to amplitude of the ABR?
If high pass is raised to 500?
DECREASES (especially Wave V
Wave V may possibly disappear
What can decreasing the low-pass filter do?
may actually eliminate noise and may enhance waveform analysis
ie., dropping from 10,000 to 3000 Hz
T/F: the typical ABR contains most energy above 2000 Hz.
False, the typical ABR contains little to no energy above 2000 Hz.
Dropping the filter below 2000, say to 1500, should have ________ (great or little) effect.
little; with the exception of slight increases in latency of Waves I, II, III, and V
Hall's recommended filter setting:
30 to 3000 Hz
Digital filtering is usually performed offline, meaning what?
after the response is acwuired
Items that MUST be selected when establishing a protocol:
the number of sweeps
start time relative to the presentation of the stimulus
electrode types and sites
Hall's Stimulus Parameter Protocol for ABR:
Duration: 0.1 MSEC (100 microseconds)
Rate: greater than 20/sec (eg., 27.3)
Intensity: Variable in dB nHL
Masking: Rarely needed
Hall's Acquisition Parameter Protocol for ABR:
Electrodes: NI- Fz, I- Ai, Ground- Fpz
Filters: HP 30, LP 3000
Analysis time: 15 msec
Prestimulus baseline: -1 ms
Sweeps (# of stim): Variable
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