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17 Cards in this Set
- Front
- Back
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Why is knowin rate of stimulation of SSEP important?
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stimulation rates more than 10 HZ could increase the latency and decrease the amplitude
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What is the normal rate of stimulation for SSEPs?
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4.7 HZ
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What is N5?
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the peripheral nerve at the elbow for median and ulnar, in interpretation it is primarily used as a control
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What is Erb's point?
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N9 2 cm above the mid-clavicular line
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What is N11?
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the dorsal column volley, only present in 75% of normals; represents the root entry zone
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What is N13?
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present in all normals represents the dorsal column/nucleus cuneatus
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What is N14?
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Only present in 15-20% of normals and represents the cervicomedullary junction
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Where are N11, N13, N14 read from?
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the montage if C5 or C7 to Fz
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What is N18?
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N18 represents a farfield potential that likely comes from the brainstem
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What is N20/P20?
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unclear exactly what generates this peak, but it represents the somatosensory cortex (either a thalamocortical relay or an average of 2 different generators)
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What is the effect of bilateral stimulation on SSEPs?
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It can enahnce the response particularly in the tibial nerve, subcortical, brainstem and cortex
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What should impedance be for electrodes in SSEP?
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less than 5 kilo ohms
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What does it mean if bilateral stimulation does not enhance the response?
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there could be difference in the conduction velocity within both the CNS & PNS from side to side
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What is normal gain/sensitivity set at for SSEPs?
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10 microvolts or 20 microvolts
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What is the filter set at for SSEPs?
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30-3000 hertz
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Why is it necessary to average 500-2000 stimuli?
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Establish reproducibility and well-displayed waveforms
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What does averaging do for the reponse in SSEPs?
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averaging will display information that is time-locked to the stimulus (in effect decreasing artifactual noise), also averaging should decrease any background artifact
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