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28 Cards in this Set
- Front
- Back
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What are the three general techniques for recording auditory evoked potentials?
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1) electrocochleography
2) auditory brain stem response audiometry 3) cortical electrical response audiometry |
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What potentials are measured by ECoG?
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1) cochlear microphonic
2) summating 3) eighth nerve action potential |
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Is ECog affected by sedation or general anesthesia?
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NO
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Is ABR affected by basal narcosis or general anesthesia?
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NO
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Which form of electrical response audiometry can best be equated with clinical hearing?
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cortical electrical response audiometry
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Is cortical electrical response audiometry affected by sleep and sedation?
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YES
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What is the source of the cochlear microphonic?
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The hair-bearing surface of the hair cells. Its onset is immediate and it mimics the waveform of the acoustic stimulus.
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A reduction in microphonics is associated with a cochlear lesion or a retrocochlear lesion?
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cochlear lesion
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What is the source of the summating potential?
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hair cells - it is a direct current shift of the baseline of the recording
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What is the technique of separating the superimposed summation potential and eight nerve action potential?
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Increase the stimulus rate until the eight nerve action potential is refractory.
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What are three parameters used to describe an action potential?
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1) latency
2) amplitude 3) waveform |
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What are three clinical uses for electrocochleography?
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1) threshold testing
2) study of Meniere's Disease 3) study of acoustic neurinomas |
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What does a decrease in summating potential suggest for hearing impairment in MD?
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The decrease in summating potential indicates a loss of hair cells and may indicate the reversibility of hearing impairment in MD.
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What is the characteristic of the compound action potential in acoustic neuromas?
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much broader than normal
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In ABR's, which wave is the largest and most consistent observed at threshold?
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wave V
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What is unique about the auditory steady-state evoked potential?
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1) the amplitude and/or frequency of the continuous tone is not constant but modulated at rates between 3 and 200Hz
2) the evoked response follows the frequencfy of modulation instead of the frequency of the tone |
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What are some clinical uses of ABR?
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1) screening neonates
2) threshold testing of infants, young children, and malingerers 3) diagnosis of acoustic tumors 4) diagnosis of peripheral neuropathies and brain stem lesions 5) intraoperative monitoring 6) monitoring electrode placement of an ABI |
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What dB sensation level can be detected for >8KHz and <500Hz using ABR?
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30dB SL
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What dB sensation level can be detected for octave-wide mid-frequecy (1-6KHz)regions?
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10dB SL
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What is the best audiometric test for acoustic tumor detection?
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ABR
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What is the normal interaural difference in wave V latency?
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0-0.2millisec
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What is a recording method that bypasses the concern of wave V latencies caused by conductive hearing losses and severe cochlear losses.
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Compare the interaural difference of the I-V wave interval.
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Large tumors that press on the brain stem can cause what defect in ABR of the opposite ear?
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interval between waves III and V
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What is the normal interval between waves III and V?
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1.9 +- 0.1 milliseconds
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What is the smallest tumor that can be detected by ABR?
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1.0 cm
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What is the stacked ABR?
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1) narrow-band wave forms are obtained
2) these are time-shifted so that the peak latencies of wave B in each derived narrow-band coincide 3) these shifted waveforms are then added together |
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What is the purpose of stacked ABR?
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to increase sensitivity and specificity to the presence of small intracanalicular tumors
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What is a electrocochleography finding that suggests Meniere's Dz?
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An SP/AP ratio of 0.5 or greater. Some use 0.35 as criteria, but it may be better to be conservative.
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