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BR 3rd Ed > Ch 5 - EDX: EMG > Flashcards

Ch 5 - EDX: EMG Flashcards

1
Q

What does needle EMG assess?

A

Nerve and muscle function:

  • Insertional activity
  • Resting activity
  • Voluntary recruitment
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2
Q

What does insertional activity represent?

A

Discharge potentials mech evoked by disrupting muscle cell mem w/ needle

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3
Q

When is increased insertional activity seen?

A

Neuropathic and myopathic conditions

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4
Q

When is decreased insertional activity seen?

A

Muscle atrophy

Muscle ischemia d/t vascular occlusion or compartment synd

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5
Q

What is normal duration of insertional activity?

A

300 ms

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6
Q

What waveforms can be produced with needle placement near NMJ?

A

MEEP and EPP

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7
Q

What are miniature end plate potentials (MEPP)?

A

Normal spontaneous exocytosis of individual quanta of Ach traveling across NMJ

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8
Q

Describe the morphology, amp, duration and rate of miniature end plate potentials (MEPP)?

A

Negative monophasic
Amp 10-50 uV
Duration 0.5-1.0 ms
Rate 150 Hz

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9
Q

What are end plate potentials (EPP)?

A

Endplate spikes d/t release of ACh provoked by needle irritation of muscle fiber or sync of several MEPPs

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10
Q

What are end plate potentials (EPP) the result of?

A

Propagated single muscle fiber AP

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11
Q

What is the hallmark sign of end plate potentials (EPP)?

A

Irregularity and negative deflection

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12
Q

Describe the morphology, amp, duration and rate of of end plate potentials (EPP)?

A

Neg biphasic morphology
Amp <1000uV (mV)
Duration 2.0-4.0ms
Rate 50-100Hz

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13
Q

Describe the sound of end plate potentials (EPP)?

A

Sputtering fat in a frying pan

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14
Q

Describe the sound of miniature end plate potentials (MEPP)?

A

Sea shell murmur

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15
Q

Where are ABN spontaneous activity generated from?

A 
Muscle fiber
motor unit (neural source)
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16
Q

What is a fibrillation potential (FIB)?

A

Spon firing AP origninating from denervated single muscle fibers 2/2 uncontrolled ACh release

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17
Q

What the hallmark sign of a fibrillation potential (FIB)?

A

Regularity of firing

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18
Q

What is a positive sharp wave (PSW)?

A

Needle recording of an AP of a single muscle fiber

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19
Q

What inhibits the display of neg deflection of the waveform of a PSW?

A

Propagation to but not past needle tip

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20
Q

Describe the initial deflection, duration and amp of a FIB.

A

Initial deflection: Positive (biphasic)
Duration: 1-5 ms
Early Amp: >300 uV
Late Amp: <25 uV

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21
Q

Describe the initial deflection, duration and amp of a PSW.

A

Initial deflection: Positive (biphasic)
Duration: 10-30 ms
Amp: <1 mV

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22
Q

Describe the sound of a FIB.

A

Rain on a tin roof

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23
Q

Describe the sound of a PSW.

A

Dull thud or chug

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24
Q

What are Complex repetitive discharges (CRDs)?

A

Polyphasic/serrated AP originating from a principal pacemaker, initiating a group of single muscle fibers to fire near synchrony

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25
Q

How is current spread in CRDs?

A

Ephaptic transmission

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26
Q

What is the hallmark sign for CRDs?

A

Regular interval b/w each discharge and within each discharge

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27
Q

Describe the sound of CRDs

A

Motor boat

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28
Q

What are myotonic discharges?

A

Biphasic single muscle fiber AP triggered by needle movement, percussion or voluntary contraction

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29
Q

What causes myotonic discharges?

A

Alteration of ion channels in muscle membrane

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30
Q

What is the hallmark sign of myotonic discharges?

A

Smooth change in rate and amplitude

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31
Q

What medication can cause myotonic discharges?

A

Propanolol

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32
Q

Describe the sound of myotonic discharges

A

Dive bomber

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33
Q

What are Fasciculations?

A

Spon discharges originating from any portion of a single motor unit and result in intermittent muscle fiber contraction

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34
Q

When are Fasciculations considered pathological?

A

If associated with FIB or PSWs

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35
Q

What is the hallmark sign of Fasciculations?

A

Irregular firing motor unit

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36
Q

What are Myokymic discharges?

A

Groups of MUAPs firing repetitively

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37
Q

Describe clinical myokymia

A

Slow continuous muscle fiber contractions. Rippling appearance of overlying skin.

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38
Q

What is the hallmark of Myokymia?

A

Semiregularity b/w each discharge and w/in each discharge

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39
Q

Describe the sound of Myokymia

A

Marching soldiers

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40
Q

What are etiologies of facial Myokymia?

A

MS
Brainstem neoplasm
Polyradiculopathy
Bell’s palsy

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41
Q

What are etiologies of extremity Myokymia?

A

Radiation plexopathy
Compression neuropathy
Rattlesnake venom

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42
Q

What are Neuromyotonic discharges?

A

Discharges originating from motor axons

43
Q

What are Neuromyotonic discharges classically seen in?

A

Neuromytonia (Isaac’s syndrome)

44
Q

What is Neuromytonia (Isaac’s syndrome)?

A

Disorder w/ continuous muscle fiber activity resulting in muscle rippling and stiffness secondary to irritable nerves

45
Q

What is the progressive decrement of waveform in Neuromytonic discharge due to?

A

Individual muscle fiber fatigue and drop off

46
Q

Describe the sound of Neuromyotonic discharges.

A

Tornado-like

47
Q

What are Cramp discharges?

A

Involuntary repetitive firing of MUAP’s in a large area of muscle

48
Q

What are artifact potentials?

A

Waveforms that obscure neurophysiologic signals

49
Q

What is exertional activity?

A

Voluntary muscle fiber activity electrically recorded as a MUAP

50
Q

What is a Motor Unity Action Potential (MUAP)?

A

Compound action potential from muscle fibers belonging to a single motor unit

51
Q

How is MUAP amplitude measured?

A

Most positive to most negative peak

52
Q

How can MUAP amplitude be increased or decreased?

A

Inc: reinnervation process
Dec: loss of muscle fibers
Variable: NMJ d/o

53
Q

What is a normal MUAP amplitude?

A

1 mV

54
Q

What is the Rise time of a MUAP?

A

Time it takes a MUAP to go from baseline to peak of negative wave

55
Q

What a normal Rise time of a MUAP?

A

<500 us

56
Q

What does the duration of a MUAP represent?

A

of muscle fibers w/in a motor unit

57
Q

How is the duration of a MUAP measured?

A

Waveforms inital departure from baseline to its final return

58
Q

How can the duration of a MUAP change?

A

Inc: motor unit territory inc from collateral sprouting
Dec: loss of muscle fibers

59
Q

What is the normal duration of a MUAP?

A

5-15 ms

60
Q

What are turns or serrations of MUAP?

A

Changes in direction of the waveform that do not cross the baseline

61
Q

What do phases of MUAP represent?

A

Synch of muscle fiber AP firing

62
Q

How are phases of MUAP calculated?

A

of baseline crossings +1

63
Q

What is considered polyphasicity of MUAP?

A

5 or > crossings

64
Q

What causes Long duration, large amplitude polyphasic potentials (LDLA)?

A

Denervation and reinnervation from collateral sprouting

referred to as neuropathic potentials

65
Q

What causes short duration, small amplitude polyphasic potentials (SDSA)?

A

Drop out or dysfunction of muscle fibers

referred to as myopathic potentials

66
Q

What disorders are short duration, small amplitude polyphasic potentials (SDSA) seen in?

A

Myopathic diseases
NMJ disorders
Severe neuropathic injury l/t nascent motor unit potentials

67
Q

What are unstable potentials?

A

Variation of MUAP’s amp, duration and slope.

68
Q

What disorders are unstable potentials MC seen in?

A

NMJ d/o which cause irregular blocking of discharges

69
Q

What are satellite potentials?

A

Small potentials seen in early reinnervation

70
Q

What is a Doublet/multiple potentials?

A

2 or > MUAPs firing recurrently and together in semi-rhythmic fashion

71
Q

What disorders are Doublet/multiple potentials seen in?

A 
Ischemia
Hyperventilation
Tetany
Motor neuron d/o
Metabolic dz
72
Q

What are Giant potentials?

A

Extremely large MUAPs (> 5 mV)

73
Q

What disorder are Giant potentials seen in?

A

Poliomyelitis

74
Q

What is Recruitment?

A

Ability to add successive motor units to inc the force of contraction

75
Q

What is the rule of 5’s in normal MUAP recruitment?

A

Onset freq of first MUAP begins at 5 Hz

When firing of 1st MUAP reaches 10 Hz, a 2nd MUAP starts at 5Hz

When 1st MUAP at rate of 15 Hz, 2nd should be at 10Hz and 3rd at 5 Hz

76
Q

What is Early recruitment?

A

ABN early firing of many MUAPs with mild contraction

77
Q

What conditions are Early recruitment seen in?

A

Myopathic conditions that result in loss of muscle fibers and some NMJ d/o

78
Q

What is Reduced recruitment?

A

Firing of only a few MUAPs with even maximal contraction

79
Q

What conditions are Reduced recruitment seen in?

A

Neuropathic conditions

Severe myopathies

80
Q

What is the Firing rate (FR) of recruitment?

A

of times a MUAP fires/second expressed in Hz

81
Q

What is the recruitment frequency (RF)?

A

Firing rate of 1st MUAP when the 2nd MUAP begins to fire

82
Q

What is the normal recruitment frequency (RF)?

A

<20 Hz

>20 Hz: neuropathic process

83
Q

What is the recruitment interval (RI)?

A

Interspike interval (in ms) b/w two discharges of the same MUAP when a 2nd MUAP begins to fire

84
Q

What is the normal recruitment interval (RI)?

A

~100 ms

85
Q

Describe the recruitment interval and frequency in neuropathy.

A

Dec interval

Inc frequency

86
Q

Describe the recruitment interval and frequency in myopathy.

A

Inc interval

Dec frequency

87
Q

Etiology of FIBs and PSWs

A

Nerve: anterior horn cell dz, radiculopathy, plexopathy, peripheral neuropathy, mononeuropathy

NMJ: Myasthenia gravis, botulism

Muscle: Muscular dystrophy, polymyositis, dermatomyositis, hyperkalemic periodic paralysis, acid maltase deficiency

88
Q

Etiology of Complex Repetitive Discharges (CRDs).

A

Nerve: anterior horn cell dz, chronic radiculopathy, peripheral neuropathy,

Muscle: Muscular dystrophy, polymyositis, dermatomyositis, limb-girdle dystrophy, myxedema

Normal variant

89
Q

Etiology of Myotonic discharges.

A

Nerve: chronic radiculopathy, peripheral neuropathy

Muscle: Muscular dystrophy, myotonia congenita, paramyotonia, polymyositis, dermatomyositis, hyperkalemic periodic paralysis, acid maltase deficiency

90
Q

Etiology of Fasciculations

A

Nerve: Anterior horn cell disease, tetany, Creutzfeldt-Jakob syndrome, radiculopathy, mononeuropathy

Metabolic: Thyrotoxicosis, tetany

Normal variant

91
Q

Etiology of neuromyotonic discharges

A

Nerve: Anterior horn cell disease, tetany

Toxins: Anticholinesterase

92
Q

Etiology of cramp discharges

A 
Salt depletion
Uremia
Pregnancy
Myxedema
Polonged muscle contraction
Myotonia congenita
Myotonic dystrophy
Stiff-man’s syndrome
93
Q

Etiology of artifact potentials

A 
EMG instrument
Printer
Unshielded power cords
Electrical outlets
Fluorescent lights
Pacemaker
94
Q

How is Recruitment ratio calculated?

A

Dividing FR of the 1st MUAP by # of different MUAPs on the screen

95
Q

What is a normal Recruitment ratio?

A

<10

96
Q

What is the interference pattern?

A

Qualitative or quantitative description of the sequential appearance of MUAPs

97
Q

What is the interference pattern composed of?

A

Recruitment plus activation

98
Q

What is Activation?

A

Ability of a motor unit to fire faster to produce a greater contractile force

99
Q

How can activation be decreased?

A

CNS diseases
Pain
Hysteria

100
Q

What is a complete pattern?

A

No individual MUAPs can be seen. A full screen represents four to five MUAPs

101
Q

What is a reduced pattern?

A

Some MUAPs are identified on the screen during a full contraction

102
Q

What is a discrete pattern?

A

Each MUAP can be identified on the screen during a full contraction

103
Q

What is a single unit pattern?

A

One MUAP is identified on the screen during a full contraction

BR 3rd Ed (92 decks)

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