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Neuro 2 > Electrodiagnostic Testing > Flashcards

Electrodiagnostic Testing Flashcards

1
Q

What is electrodiagnostic testing used for? Who typically performs these tests?

A
  • Used to asses function and integrity of the PNS and the musculature it innervates
  • Performed by MD, PT, and other members of healthcare profession
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2
Q

What are the major purposes of nerve conduction velocity tests?

A

NCV – nerve conduction velocity
- Helps diagnose nerve damage or disease
- Measurement of how well electrical signals (Aps) travel up/down peripheral nerves
- Evaluates the peripheral nerve in its entirety

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3
Q

What are the major purposes of electromyography?

A

EMG – electromyography
- Determines myopathic involvement
- Measurement of how muscles respond to electrical signals (Aps) both during rest and with activity
- Looks at the muscle belly and neuromuscular junction

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4
Q

What information does NCV/EMG provide?

A
  • Time course of disease
  • Anatomic location of pathology
  • Nature of pathology
  • Distribution of pathology
  • Physiological status of lesion
  • Data for clinical/lab use
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5
Q

What nerves do we test? Why?

A

Large diameter myelinated nerves
Easier to zap and easier to measure due to myelin

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6
Q

In the motor nerve conduction testing portion of NCVs, what are CMAPs?

A
  • Compound Motor AP – measures amplitude of AP
    o Test is grabbing the last AP at the neuromuscular junction before it hits the muscle belly
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7
Q

In the sensory nerve conduction testing portion of NCVs, what are SNAPs?

A
  • Sensory nerve AP
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8
Q

In the motor and sensory conduction tests, what is latency?

A
  • Time in which AP travels from stimulator to electrode
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9
Q

In the motor and sensory conduction tests, what is conduction velocity and how is it determined?

A
  • Speed of AP
  • Length/(proximal latency – distal latency)
    o Proximal latency – elbow or knee
    o Distal latency – wrist or ankle
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10
Q

What is the difference between orthodromic and antidromic testing?

A
  • Orthodromic – stim distal and record proximal
    o Natural direction of sensory APs
  • Antidromic – stim in middle and have bidirectional AP
    o Opposite direction of sensory APs
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11
Q

When are F wave tests performed? How do they work?

A

F-wave
- Retrograde “rebound” motor impulse – travels full length of motor axon and back (rebounds at anterior horn)
- Used to evaluate proximal damage and demyelination (GBS, radiculopathy, peripheral neuropathies)

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12
Q

When are H-reflex tests performed? How do they work?

A

H-wave
- Used to evaluate radiculopathy
- Follows muscle stretch reflex arc – goes all the way to spinal cord
- Can help in evaluation of nerve root lesions and UPPER motor neuro lesions (spinal cord)

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13
Q

What are some of the basic interpretations that can be made within a NCV study? (3 definitions)

A
  • Amplitude – related to # of axons in nerve
  • Latency – marker in time, therefore most affected by demyelinating processes
  • Conduction velocity – speed, can be affected by both axonal loss and demyelination
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14
Q

What is the conduction velocity when large, fast-conducting fibers are lost?

A

moderate slowing

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15
Q

What is the conduction velocity during demyelination?

A

marked slowing

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16
Q

What types of pathology are EMGs most helpful in diagnosing?

A

Conditions that interfere with MUSCULAR CONTRACTION
- Diseases that affect the muscle (muscular dystrophies)
- Diseases that affect the neuromuscular junction (myasthenia gravis)
- Diffuse nerve disorders that cause peripheral neuropathies
- Disorders that affect the motor neurons (anterior horn cells) in the spinal cord (ALS, ruptured spinal disc)

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17
Q

Explain what a motor unit action potential is, and how its relevant to EMGs.

A
  • MUP – summed electrical activity of all muscle fibers activated within the motor unit
  • What is measured during an EMG
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18
Q

What is considered normal muscle activity surrounding insertional activity?

A
  • Normal – slight movement but then there should be silence while muscle is at rest
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19
Q

What does a decrease in normal insertional activity mean?

A

associated with loss of muscle fibers or metabolic disease

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20
Q

What does an increase in normal insertional activity mean?

A

associated with neuropathic or myopathic disorders

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21
Q

What does a prolonged insertional activity mean?

A

post-acute denervation, inflammatory muscle disorders, muscular dystrophy

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22
Q

What is considered normal versus abnormal muscle activity at rest?

A
  • Normal – silence at rest with the occasional movement as things fire
  • Abnormal – nothing moves at rest
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23
Q

What 3 things determine speed of AP?

A
  • diameter of axon
  • presence of myelin
  • amount of myelin
24
Q

What are limitations to electrodiagnostic testing?

A
  • easily affected by: age, temp, obesity, edema
  • must be diligent about electrode placement
25
Q

What is fibrillation associated with?

A

single muscle fiber that is degenerating
- suggests there is a LMN problem
- look like a mini EKG

26
Q

When are fibrillations seen?

A

2-3 weeks after an injury

27
Q

What is associated with fibrillations and are they always seen together?

A

positive sharp waves
- not always seen with fibrillation but often seen together

28
Q

What is a fasciculation? Normal or abnormal?

A
  • spontaneous, repetitive, twitch-like contraction of the examined muscle at rest
  • normal and abnormal
  • occurs at LMN
29
Q

What are complex repetitive discharge? What is a specific component that they have?

A
  • polyphasic high frequency waveforms that are fixed in amplitude and consistent with discharge rate
  • have an audio component
30
Q

When do we see complex repetitive discharge?

A

chronic pathologies
- chronic nerve entrapment
- Marie Charcot tooth

31
Q

What does myokymic muscle activity look like?

A

waves of contractions in groups

32
Q

What does myotonic muscle activity look like? What disorders are these present with?

A

all over the place contractions
- indicative of myotonic disease (rare genetic diseases characterized by muscle weakness and wasting)

33
Q

After an injury to MUP and the nerve has recovered, what will be seen on an EMG?

A

AP amplitudes are bigger and the waveforms are stretched out because 1 nerve has twice as many terminal axons as before

34
Q

nerve conduction velocity results with neuropraxia (ie: carpal tunnel)

A
  • increase latency and decreased conduction velocity
  • decreased amplitude of SNAP & CMAP if prolonged compression
35
Q

EMG results of neuropraxia (ie: carpal tunnel)

A

normal or show signs of denervation if prolonged

36
Q

nerve conduction velocity results of incomplete disruption axonotmesis

A
  • decreased amplitude of SNAP & CMAP
  • increased in distal segment latency with decreased conduction velocity
37
Q

nerve conduction velocity results of complete disruption axonotmesis

A
  • complete loss of motor and sensory response when proximal segment is stimulated
  • absence of CMAP & SNAP in distal segment
38
Q

EMG results of axonotmesis

A
  • prolonged insertional activity
  • fibrillation and positive sharp waves
  • polyphasic MUAPs, initially reduced recruitment that increases with time
39
Q

nerve conduction velocity results of neurotmesis

A
  • decreased amplitude of SNAP & CMAP
  • increased in distal segment latency with decreased conduction velocity
    (same as axonotmesis)
40
Q

EMG of neurotmesis

A
  • prolonged insertional activity
  • abnormal activity at rest (fibrillation, + sharp waves, fasiculations)
  • polyphasic MUAPs, initially reduced recruitment that increases with time
  • no voluntary activity
41
Q

carpal tunnel amplitude during nerve conduction

A

normal for CMAP and SNAP

42
Q

carpal tunnel latency during nerve conduction

A

goes up (increase time) no matter where you zap them
- should be really obvious when you zap them at the wrist

43
Q

carpal tunnel conduction velocity during nerve conduction

A
  • goes down because of the increase in latency
44
Q

What would you expect to see with EMG findings for carpal tunnel?

A

normal

45
Q

What is the expected result of a CMAP w/ diabetic neuropathy?

A
  • leads to decreased amplitude due to axon degeneration
46
Q

What is the expected result of a orthodromic SNAP w/ diabetic neuropathy?

A
  • see a decreased amplitude when the stem is placed in an area of sensory loss
  • will see normal conduction when the stem is placed above the area of sensory loss
47
Q

What will you see in the NCV study if the patient has lost 50% integrity of its nerve fibers?

A

the amplitude would decrease and increase in latency
- decrease in conduction velocity

48
Q

Why are EMGs less helpful in adding diagnostic value to diabetic neuropathies until later in the disease progression?

A

muscles aren’t affected until later on in the progression of the injury

49
Q

EMG results of diabetic neuropathy

A
    • fibrillation potentials
    • sharp waves
  • LE > UE
  • increased amplitude and duration of MUAP
50
Q

Nerve conduction velocity results of charcot marie tooth disease

A
  • uniform slowing of latency and reduction of conduction velocity
  • chronic - reduced amplitude
51
Q

When is an EMG helpful with charcot marie?

A

during the chronic stages

52
Q

EMG results of charcot marie

A
    • fibrillation
    • sharp waves
  • increased amplitude and duration of MUAP
53
Q

Nerve conduction results of guillan-barre

A
  • increased latency due to loss of myeline at points along axon
  • decreased amplitude b/c myeline insulates axon and when its gone the AP starts leaking out
54
Q

T/F: EMGs are not helpful in ruling in demyelinating disorders if in the acute phase

A

true

55
Q

nerve conduction test results of myopathies like muscular dystrophy

A

typically normal

56
Q

EMG results of myopathies like muscular dystrophy

A
  • early maximum recruitment
  • fibrilation, + sharp waves
  • decreased amplitude, duration MUAP; polyphasic

Neuro 2 (19 decks)

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