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ECS > NCS instrumentation > Flashcards

NCS instrumentation Flashcards

1
Q

3 Variables

A

1.Intensity of stimulus voltage fixed (0-400N); Amperes (0-100)mA amount of current 2. Duration aka pulse width of stimulus (50-1000ms) 3. Rate of stimulus 1-50 stim/sec(Hz)

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2
Q

What do Pre Amp/Amplifiers do?

A

Convert low voltage signal to higher voltage copy

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3
Q

What does the Differential Amp do?

A

2 amps- measure diff b/w active and reference

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4
Q

Common Mode Signal

A

Seen in both amps (active and reference)

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5
Q

What is the Common Mode rejection ratio (CMRR)?

A

ability of amp to amplify desired signal while rejecting common mode signal; measured in decibals-clinical amplifiers >90Db

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6
Q

What does the HF/Low Pass filter do?

A

resistors filter out high frequency

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7
Q

What does the LF/High Pass filter do?

A

resistors filter out low frequency

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8
Q

What is recommended filter setting for motor studies?

A

LF- 2-10Hz; HF- 10KHz

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9
Q

What is recommended filter setting for sensory studies?

A

LF- 2-10Hz; HF- 2KHz

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10
Q

What is recommended filter setting for EMG?

A

LF- 20-30Hz; HF- 10KHz

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11
Q

What is effect if INCREASE LF filter?

A

DECREASE AMP and DECREASE LATENCY Stabilize baseline

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12
Q

What is effect if DECREASE LF filter?

A

INCREASE AMP and INCREASE LATENCY

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13
Q

What is effect if INCREASE HF filter?

A

INCREASE AMP and DECREASE LATENCY

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14
Q

What is effect if DECREASE HF filter?

A

DECREASE AMP and INCREASE LATENCY

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15
Q

What is typical sweep speed?

A

10ms/div = duration (entire screen) 100ms Set sweep speed at 100ms/div= duration of 1 second if have 10boxes across

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16
Q

What is CMAP?

A

summation of individual mm fiber action potentials

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17
Q

What is SNAP?

A

summation of individual sensory fiber action potentials

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18
Q

What do mixed studies test?

A

record largest sensory nerves (1a) afferent mm spindle, largest and most myelinated so usually affected 1st in demyelinating lesions

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19
Q

What does amplitude represent?

A

of fibers that depolarize

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20
Q

What does NCS duration represent?

A

measure of synchrony- extent that fibers depolarize at same time

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21
Q

What does conduction velocity measure?

A

speed of the fastest conducting fibers

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22
Q

How is motor conduction velocity measured?

A

calculated in proximal segment only! CV=distance/(prox lat-distal lat)

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23
Q

How is sensory conduction velocity measured?

A

calculated in proximal and distal segments distance/time

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24
Q

What temp should we maintain for NCS performed in UE and LEs?

A

UE-32 and LE >29

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25
Q

What is the effect of having decreased temp?

A

increased amp, duration, prolonged latency decreased CV

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26
Q

How does age variable affect CV?

A

decrease 1-2ms per decade past 20 years old

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27
Q

How does UE CV compare to LE CV?

A

UE CV is faster than LE CV

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28
Q

How does proximal CV compare to distal CV?

A

Faster proximal; closer to trunk/nutrition, larger diameter

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29
Q

How does segment size LONG vs SHORT studied affect calculations?

A

Measure a short segment, risk for more error, since small error has SIG effect on calculation

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30
Q

Describe a MUP morphology.

A

3 phases, amp-300-500uV, duration-<10-12ms

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31
Q

What does MUP EMG duration represent?

A

of mm fibers within motor unit. ‘pitch’ will increase as number of fibers and territory increases

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32
Q

What does a long duration MUP mean?

A

dull and thuddy, sign of chronic condition-motor unit remodeling

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33
Q

What does a Short duration MUAPs sound like?

A

‘crisp’

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34
Q

What does polyphasia represent?

A

measure of synchrony and axonal sprouting

35
Q

What does MUP amplitude affect?

A

Volume

36
Q

What does a unstable MUAP mean?

A

NMJ disorder or increased jitter

37
Q

MM fiber recruitment follows what rule normally?

A

Rule of 5s 1 MU at 5Hz; 2nd MU will come in at 10Hz

38
Q

How can you increase force?

A

Increase rate of fire (activation) or recruit more MUs

39
Q

What is recruitment ratio?

A

Rate of fastest firing MU/total number of MUs >10= decreased recruitment (neuro); <5=increased/early recruit (myopathic)

40
Q

What is decreased recruitment?

A

caused by LOSS OF MUAPs; conduction block or axonal loss, can’t bring enough soldiers to the fight

41
Q

What is increased/early recruitment?

A

caused by LOSS OF MM FIBERS; get lots of MUs fire to produce small amount of force

42
Q

Describe what chronic axonal loss MUs will look like.

A

large amp, long duration, polyphasic-reinnervated mms

43
Q

What would demyelination look like on EMG?

A

MUAP morphology-normal-C.B-decreased recruit (GBS and CTS)

44
Q

What would a myopathic MU look like?

A

decreased # of mm fibers- short duration low amp (BSAPP)

45
Q

How many mm fibers can contribute to a MUP?

A

at max 12

46
Q

How close to the needle tip do mm fibers have to be?

A

1-3mm

47
Q

How many MUPs in each mm can be analyzed?

A

@ least 12; 4 quadrants-3 probes each quadrant

48
Q

The mm fibers of 1 MU can be spread over oval x-sectional area of what size?

A

5mm

49
Q

How many MUs can be recorded from needle tip?

A

12-15

50
Q

A typical MU has how many phases?

A

3 phases

51
Q

What would increase duration of MUP?

A

increased phases and turns; axonal sprouting/regeneration

52
Q

Why would we have 0 MUPs?

A

No axons, complete CB, pain or lesion in CNS

53
Q

What happens to mm fibers when needle is briskly moved in mm?

A

Depolarize the mm and get insertional activity

54
Q

How long does normal insertional activity last?

A

<200-300ms

55
Q

What is increased insertional activity?

A

>200ms; usually with myotonic disorders

56
Q

What is decreased insertional activity?

A

mm damage/chronic denervation; if get resistance to needle insertion=poor prognosis since getting mm fibers turning into fibrotic tissue

57
Q

To observe spon activity settings are…

A

10ms sweep speed, 50mV/div

58
Q

What things can cause abnormal spon activity?

A

trauma, inflammation and denervation

59
Q

Fibs and PSWs are signs of what?

A

acute ‘active’ denervation/mm membrane instability

60
Q

Prejunctional

A

problem w/motor nerve terminal branch

61
Q

Postjunctional

A

lesion in mm fiber

62
Q

Any potential that fires <4-5Hz

A

is not under voluntary control

63
Q

What types of potential do you see that are MFAP/post

A

fibs, psws, myotonic, CRD

64
Q

What types of potential do you see that are MUAP/pre

A

fasiculation, myokymic, neuromytonia,cramps

65
Q

What causes a EPP/EPS?

A

needle touches axon terminal causing depolarization

66
Q

What is a unstable membrane potential cause by?

A

decrease in intracellular K+

67
Q

What are EMG characteristics of fibs?

A

+deflection, 3phases, amp: 30-800uV, duration<5ms, regular fire rate (post-junct), click, raindrop

68
Q

What are EMG characteristics of psws?

A

biphasic, duration 30-100ms

69
Q

How soon post injury should EMG be performed?

A

3wks/21 days

70
Q

What are EMG characteristics of EPS?

A

Irregular fire (pre), biphasic, -deflection, hiss/sputtering

71
Q

Why is it incorrect to refer to fibs/psws as denervation potentials?

A

Can see them in myopathic conditions

72
Q

What are EMG characteristics of Myotonic d/c?

A

+deflection, phases 2-3, duration 2-3ms, rate 50-100Hz, WAX AND WANE; dive bomber sound

73
Q

What are EMG characteristics of CRDs?

A

Pacemaker ephatic D/C=chronic pathology, phases-polyphasic, duration 10-15ms, amp 50-1000uV, regular fire rate- MACHINE

74
Q

What are EMG characteristics of myokymic d/c?

A

undulating/quivering skin, post radiation- same MUAP fires, burst, soldier marching

75
Q

What are EMG characteristics of neuromyotonia d/c?

A

WANING, AMP decreasing, highest freq- stiffness ‘Issac’s Syndrome’

76
Q

What is type of activity is in this picture?

A

CRDs

77
Q

What is type of activity is in this picture?

A

End plate spike

78
Q

What is type of activity is in this picture?

A

Fibrillations

79
Q

What is type of activity is in this picture?

A

Myotonic discharge

80
Q

What is type of activity is in this picture?

A

postive sharp waves

81
Q

What is type of activity is in this picture?

A

Neuromyotonia

82
Q

What is type of activity is in this picture?

A

Myokymic discharges

83
Q

What is type of activity is in this picture?

A

MEPPs

84
Q

Describe psudofacilitation regarding NCSs.

A

Amplitude increases but the area under waveform decreases. Not adding any new mm fibers to it; the mm fibers are just firing more synchronized.

ECS (13 decks)

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