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EMG > EMG > Flashcards

EMG Flashcards

1
Q

EMG provides

___ info about muscle

____ info about nerve

A
  • Direct info about muscle
  • Indirect info about nerve
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2
Q

name 5 clinical indications for EMG/NCS

A

Muscle weakness
Muscle atrophy
Numbness
Reduced reflexes
Neuropathic pain?

These only apply as indications if there is a specific question to be answered.. Don’t just order to verify what you already know
Extension of physical exam
Good for any objective neurological finding, less useful for subjective complaints

Pain not picked up on this exam (unless other neuro deficits) b/c needle EMG doesn’t test the small unmyelinated nerves

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3
Q

6 benefits from EMG

A

Establish correct diagnosis
Localize the lesion
Establish severity of lesion
Approximate timeline
Prognostic value
Assess therapeutic benefit of treatment`

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4
Q

3 precautions/contraindications for EMG/NCS

2 safety/risk considerations

A

Precautions/Contraindications
Anticoagulation (INR > 3.0*)
Bleeding disorders
Active infection

Safety/Risks
AICD is safe for needle portion of exam
Risk of pneumothorax/hematoma/nerve damage

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5
Q

in ____% of individuals, lung apex rises above the clavicle where it may be puncured laterally

A

20

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6
Q

which muscle places the patient at highest risk of PTX

A

SS

The supraspinatus muscle lies in the supraspinous fossa. Needle electromyographic examination of this muscle may be complicated by pneumothorax if sampling is near the midpoint where the supraspinous fossa is narrowest ( A). If the needle is placed deep above point A (area marked by *), there is a risk of pleural puncture. The muscle can be more safely sampled medially in the supraspinous fossa ( B).

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7
Q

What is the peripheral nervous system components hat make up that which is tested on EMG (5)

A

1.AH cell
2. DR ganglia
3. NMJ
4. muscle fiber
5. axon

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8
Q

Define a motor unit

A

Motor unit:
- one axon
- anterior horn cell
- all connected muscle fibers and neuromuscular junctions.

Motor neuron, neuromuscular junction, and muscle fiber

A nerve fiber action potential normally always results in depolarization of all the muscle fibers of the motor unit creating an electrical potential known as the motor unit action potential (MUAP)

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9
Q

what is wallerian degeneration:

A

degeneration of the nerve distal to the site of injury

Axon and myelin death = muscle atrophy and muscle membrane irritability (so spontaneous depolarizations can occur) and voluntary contractions can become uncoordinated

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10
Q

spontaneous recordings:

What location?

Fasciculation
Myokymia
Tetany
Cramp
Neuromyotonia

A

Motor neuron/axon

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11
Q

spontaneous recordings:

What location?

end plate sike

A

terminal axon

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12
Q

spontaneous recordings:

What location?

complex repetitive discharge

A

multiple muscle fibers

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13
Q

spontaneous recordings:

What location?

fibrillation
PSW
myotonia

A

single muscle fiber

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14
Q

spontaneous recordings:

What location?

end-plate noise

A

NMJ

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15
Q

Which needle?

less interference
more painful

A

concentric

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16
Q

which needle?

larger amplitude
more polyphasia

A

monopolar

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17
Q

which needle?

active electrode runs as a small wire through the needle center and the shaft serves as the reference electrode

A

concentric

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18
Q

which needle?

needle is Teflon coated (less painful). Additional electrode is needed as the reference electrode (G2). Insulated shaft, so less artifact.

A

monopolar

To Remember: ‘Mono’ = one so still need a second electrode to serve as the reference

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19
Q

which needle?

reference electrode (G2), whereas the active electrode (G1) runs as a very small wire through the center of the needle and is exposed at the needle tip, which is beveled.

recording field?

A

concentric

“teardrop” configuration

  • monopolar has much larger recording area
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20
Q

The more muscles you test, the more ____ the results are (more likely to find pathology).

A

sensitive

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21
Q

5 components to pay attention to during the EMG exam

A

Insertional activity
Muscle at rest
Muscle during gentle contraction
Recruitment
Interference pattern

  • Establish consistent sequence for EACH muscle so nothing is forgotten
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22
Q

EMG screen

_____ = vertical boxes

_____ = horizontal boxes

A

Gain = vertical boxes (200uV)

Sweep = horizontal boxes (10ms)

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23
Q

____ = intensity of signal

A

gain

24
Q

____ = time of signal

A

sweep

25
Q

what are the standard setings for EMG?

Sweep

Gain

A

Sweep
10ms/Division

Gain

50uV for spontaneous activity

100-500uV for motor unit analysis

26
Q

describe how each is measured in waveform analysis

amplitude:
duration:
Rise time
Negative deflection
positive deflection

A

Amplitude: peak to peak
Duration: baseline to baseline
Rise Time
Negative deflection (upward)
Positive deflection (downward)

27
Q

Technique for needle exam

  1. test ___ of the muscle
  2. Move from ___ to __ in each section
A

Represents brief burst of muscle fiber potentials thought due to shearing of muscle fibers
When withdraw to change quadrants, come back to just below the surface of skin and redirect the needle slightly. Then, move from shallow to deep with quick bursts of the needle.
Warn patient that you have to agitate the muscle.

28
Q

With each needle movement, normal insertional activity is brief and usually lasts _____.

Increased insertional activity can be seen in ____

A

300 ms or less

in both neuropathic and myopathic disorders

29
Q

Which of the following abnormal spontaneous activities is generated by a single muscle fiber?

Fasciculation potential
Myokymic potential
Neuromyotic potential
Myotonic potential
Cramp

A

d

30
Q

spontaneous activity generated by the muscle (4

A
  • fib potentials
  • PSW
  • myotonic discharges
  • CRDs
31
Q

Spontaneous activity generated by the nerve (6

A
  • myokymic discharges
  • cramps
  • neuromyotonic discharges
  • tremors
  • multiples (MUAPs, ie doublets, triplets)
  • *fasciculations (can be muscle or neve generated)
32
Q

myokymic discharge is often associated with ____

A

radiation plexopathy

33
Q

Which activity starts and stops abruptly?

A) fibrillation potential
B) positive sharp wave
C) complex repetitive discharge
D) Myotonic discharge
E) Myokymic discharge

A

c

34
Q

PSW fire at what freq?

regular?

A

0.5-10hz

yes

35
Q

PSW and fibs are graded on a scale of _____

A

Imply ongoing denervation
Present in many conditions
Graded on Scale 0-4
0 = none
1 = persistent single train of PSW in at least 2 areas
3 = moderate number in 3 or more areas
4 = full interference pattern of PSW

36
Q

CRDs

Indicates:

Firing frequency:

Start and stop ____

___ sound

A

Indicates chronic pathology
Firing frequency 10-100Hz
Start and stop abruptly
Same complex fires repetitively and quickly
Machine sound

37
Q

Myotonic discharges

  • fire freq:

seen clinically as:

sounds like _____

in _____ morphology

A

Firing frequency varies between 20 – 100Hz

Clinically seen as delayed relaxation after a strong contraction

Dive bomber sound or revving engine sound

In PSW or fib morphology

Can occur in many diseases

Induced my needle movement

38
Q

Myokymic discharge

Firing pattern:

sounds like:

A

Firing pattern = regular bursts of groups of motor units

Sounds like soldiers marching

39
Q

Neuromyotonia

sounds like:

____ firing pattern

Frequency:

A

Ping sound
Waning firing pattern
Very high frequency (150-250 Hz)

40
Q

The following are in order from lowest to highest of what?

fasciculations
doublets,triplets,multiplets
myokymia
cramps
neuromyotonia

A

frequency and number of potentials

41
Q

Endplate spikes:

Firing pattern:

occurs when?

Initial ______

sounds like:

A

Irregular, sporadic firing pattern

Occurs when needle tip is near an endplate zone

Initial negative deflection

Cracking, buzzing, sputtering sound

42
Q

endplate noise

sounds like:

A

‘Seashell’ sound

Theses areas are often painful for patient

43
Q

4 components to pay attn to on MUAP

A

Amplitude (height)
Duration (length)
Phases
Rise time

44
Q

___ refers to the waveform that is generated by voluntary contraction of the muscle during EMG testing

A

muap
(not SNAP or CMAP during nerve conduction)

Type of needle dictates normative values (amplitude, duration, phases)

45
Q

what happens with reinnervation and fiber group typing in neuropathic process

A

A large MUAP is recorded. In this case, a single active motor neuron is now innervating more muscle fibers. When it fires there will be more muscle fiber action potentials and thus a larger MUAP

46
Q

normal amplitudes

concentric needle:

monopolar:

A

Concentric needle < 4mV
Monopolar needle < 7mv

Varies greatly on needle position

47
Q

Of all MUAP parameters, amplitude is most dependent on _____. Only muscle fibers very close to the needle contribute to _______, as opposed to _____, wherein most muscle fibers contribute. Note change in amplitude as needle is moved to different locations within the same motor unit

A

needle position
amplitude
duration

48
Q

Concentric:

A

Concentric: < 10% MUAPs can be polyphasic
Monopolar: < 25% MUAPs can be polyphasic

Some muscles can have more polyphasic units (i.e. deltoid)

Represents desynchronized discharges

49
Q

normal duration:

Long duration means:

Short duration means:

A

Normal 5 – 15 msec

Long duration = asynchronous firing (i.e. reinnervation from neuropathic disease)

Short duration = due to fewer muscle fibers

50
Q

_____ The number of times the same motor unit fires per one second

A

firing frequency

Helps identify source of waveform
- regular vs irregular
- slow, fast, really fast

51
Q

how do you calculate firing frequency?

A

number of times MUAP fires per second.

calculated by dividing 1000 by the interspike interval

52
Q

increased force of muscle contraction is generated in 2 ways:

A
  1. Faster firing frequency (activation)
  2. Recruiting additional units (recruitment)
53
Q

____ is The orderly addition of motor units to increase the force of muscle contraction

A

recruitment

54
Q

two methods of recruitment analysis that can be used

A
  1. Noting firing frequency of first unit when 2nd unit is recruited (normal is around 5-10Hz)
  2. Recruitment Ratio
    * Normal = 5
    * Neuropathic > 8
    * Myopathic < 3
55
Q

recruitment ratio =

A

= Fasting Firing Frequency/total number of units

  1. Calculate frequency of the fastest firing unit: (in this case, the largest unit)
    6 boxes x 10ms = 60ms
    1 fire/60ms x (1000ms/1sec) = 17Hz
  2. 17Hz/4 = 4.25
  3. RR = 4.25

EMG (18 decks)

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