interwave/interpeak latencies (IWI/IPI)
the time between the different peaks in the waveform
normal ABR waveform
characterized by 5-7 vertex positive peaks between 1.4 to 8ms
wave I-V difference norm
3.6
wave I-III difference norm
2
wave III-V difference norm
1.8
wave I latency norm
1.6
wave III latency norm
3.7
wave V latency norm
5.6
what should you see in a normal hearing patient's ABR results when using a loud (70-80dBnHL) stimulus?
waves, I, III, and V with well-defined peaks
as the rate of the stimulus ___ the latency of the waveform peaks ___
increases; increases
interaural latency difference (ILDs)
the comparison between the latencies of wave V in the left and right ears
absolute latency
the time interval between the onset of the stimulus and a specific peak
a normal ABR ranges in amplitude from ___
0.1 to 1.0 microseconds
as the intensity of the stimulus ___ the latency fo the waveform peaks ___
increases; decreases
A click has an abrupt and rapid onset with a broad frequency response, which can elicit a ____
synchronous neural discharge
time locking
when the onset of the stimulus is connected with the onset of the computer alaysis sweep
The SNR is a function of the number of ___ that are averaged together
sweeps
in an SNR function, the number of sweeps needs to ___ so that the amplitude of the noise ___
increase; decreases
background noise is:
spontaneous and unrelated to the stimulus
the best chance to get the best ABR recording is when:
the patient is relaxed and quiet (reduces muscle artifact)
for ABRs, what transducer is preferred
inserts
because of the tubing length from the speaker to the EAC, inserts create a delay in the system causing a ___ delay in the absolute latencies of the waves
0.9ms
trigger pulse
marks the beginning of the recording epoch and is usually coupled to the onset of the stimulus
the click stimulus has an instantaneous onset and a brief duration of ___
100 microseconds
in order to determine an ABR response, it is necessary to distinguish a ___ response from the ___ background noise
low-amplitude response; high-amplitude
common mode rejection
anything different gets amplified
FSP averaging
a method of estimating background noise in which the variance of the aberaged response is compared to the variance of the amplitude of a single point at a given time in the waveform
where does excessive muscle artifact come from?
the jaw or neck
when recording an ABR, wave V latency can shift depending on ___. at ___, the change has a steeper slope but at ___ the shifts can be as much as ___ per 10dB increase
the intensity of the stimulus; lower intensities; 0.2 to 0.3ms
stimulus rates above 30 stimuli per second will ___ the latency of all peaks of the ABR and will ___ the amplitude of the earlier peaks
increase; decrease
where is the PAM?
8-12ms
ABR recordings do not appear to be affected by ___
sleep
The binaural response is not the same as summing the monaural responses because the binaural interaction component (BIC) reflects ___ and ___ differences between monaural and binaural stimulus conditions
amplitude; phase
ABRs are usually recorded by stimulating one ear and recording the waveform in response to that stimulation.
when using a tone burst stimulus, the ___ frequency stimuli elicit shorter latencies than the ___ frequency stimuli
high; low
allowig more ___ frequecies to be icluded in the ABR recording will increase interference from electrical and myogenic sources
low
patient factors that could affect ABR recording
age, medication, muscle artifact
recording factors that could affect ABR recording
electrode montage, filter settings, number of sweeps
stimulus factors
rate, frequency, intensity
one of the greatest technical challenges to overcome in the OR during auditory nerve tumors
noisy environment
patient symptoms that indicate good candidates for ABR
1. asymmetric HL
2. sudden-onset HL
3. unilateral tinnitus
4. dizziness
5. progressive HL
latency-intensity function
graphic representation of the wave V latency that can be helpful in identifying the type of hearing loss
the latency-intensity function for cochlear HL is ___ than that for people with normal hearing or retrocochlear HL
steeper
how can we increase the amplitude of wave I?
1. increase stimulus intensity
2. use a horizontal electrode montage between ears
3. decrease stimulus rate
4. comparing rarefaction and condensation clicks
5. use ECochG
how can we ensure that the ABR results correlate with other results?
test battery and cross-check
patients with ___ have normal OAEs and absent/grosslyabnormal ABRs
auditory neuropathy
the ABR is sensitive to problems in ___ and ____
the 8th nerve; the low to mid brainstem
when is masking recommended in ABR testing?
when there are significant threshold differences between the ears
when masking for a click stimulus, you must use a ___
broadband noise masker
ABR pros
1. provides information about neural function of lower auditory system
2. highly sensitive to identifying tumors of the auditory system
3. non-invasive
ABR cons
1. subjectivity in picking peaks
2. not sensitive to all central nervous system
3. cannot pick up differences in patients with peripheral hearing loss
ABR evaluation reports should include ___
any other test results that you performed
when sending an ABR report to the referring source you must include ___, ___, ___
1. test parameters used
2. latency values and hwere on the waveforms the peaks were marked
3. a copy of the ABR waveform
___ patients are the usual target of use of the ABR for otoneurological evaluation
adult
for a neurodiagnostic evaluation, you must include the patient's ___
absolute and interwave latencies
clinical ABR systems provide ___ and ___
a latency summary table; format for plotting