NCS BASICS EXAM QUESTIONS AND
ANSWERS
How are the normal values for NCS's established? - Correct Answers -NCS's normal
values are based upon hundreds and even thousands of past studies. The values for
latency, amp, and cv are averaged to calculate a mean value (average) for each
parameter. Two standard deviations from the mean are used to define normal values.
Why is the accuracy of measurements so important when performing NCS's? - Correct
Answers -all stimulation and recording sites, particularly the associated distances
between the sites, must be consistent with the studies used to establish the Normal
values. A relatively minor change in the distance between a stimulus and recording
electrode results in a change in the distance between a stimulus and a recording
electrode results in a change of latency of the evoke response nd could cause studies
to be misinterpreted.
What test parameters are studies in motor nerve studies? - Correct Answers -Motor
nerve studies compare distal take-off latency, proximal amp., and conduction velocity to
normal values.
What parameters are studies in sensory studies? - Correct Answers -Sensory studies
compare peak latency and amplitude with normal values.
What parameters are studies in late responses? - Correct Answers -Late responses are
normally performed to compare only latencies.
patient tremor or other physical abnormalities - Correct Answers -abnormalities, such as
tremor, can affect test results.
patient callouses or edema at the stimulation or recording site - Correct Answers -
patient callouses or edema at the stimulation or recording site can affect test results.
patients over 60 years old - Correct Answers -patients over 60 years old can exhibit
reduced nerve amplitude and conduction velocity.
Describe nerve latency and explain how latency studies differ between motor nerve
studies and sensory nerve studies. - Correct Answers -Latency is the time delay
between the stimulus and the resulting evoked response as recorded a given distance
from the stimulus. In motor nerve studies, the latency is measured from the initiation of
the stimulus to the initial defection from the baseline at the beginning of the response,
which corresponds to the CMAP.
ANSWERS
How are the normal values for NCS's established? - Correct Answers -NCS's normal
values are based upon hundreds and even thousands of past studies. The values for
latency, amp, and cv are averaged to calculate a mean value (average) for each
parameter. Two standard deviations from the mean are used to define normal values.
Why is the accuracy of measurements so important when performing NCS's? - Correct
Answers -all stimulation and recording sites, particularly the associated distances
between the sites, must be consistent with the studies used to establish the Normal
values. A relatively minor change in the distance between a stimulus and recording
electrode results in a change in the distance between a stimulus and a recording
electrode results in a change of latency of the evoke response nd could cause studies
to be misinterpreted.
What test parameters are studies in motor nerve studies? - Correct Answers -Motor
nerve studies compare distal take-off latency, proximal amp., and conduction velocity to
normal values.
What parameters are studies in sensory studies? - Correct Answers -Sensory studies
compare peak latency and amplitude with normal values.
What parameters are studies in late responses? - Correct Answers -Late responses are
normally performed to compare only latencies.
patient tremor or other physical abnormalities - Correct Answers -abnormalities, such as
tremor, can affect test results.
patient callouses or edema at the stimulation or recording site - Correct Answers -
patient callouses or edema at the stimulation or recording site can affect test results.
patients over 60 years old - Correct Answers -patients over 60 years old can exhibit
reduced nerve amplitude and conduction velocity.
Describe nerve latency and explain how latency studies differ between motor nerve
studies and sensory nerve studies. - Correct Answers -Latency is the time delay
between the stimulus and the resulting evoked response as recorded a given distance
from the stimulus. In motor nerve studies, the latency is measured from the initiation of
the stimulus to the initial defection from the baseline at the beginning of the response,
which corresponds to the CMAP.
