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Neuroanatomy and Physiology > Lecture 6 > Flashcards

Lecture 6 Flashcards

1
Q

What is electrodiagnostic testing?

A

Used to assess function and integrity of the PNS and the musculature it innervates

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2
Q

What are the 2 most common electrodiagnostic tests?

A
  • Electromyography (EMG)

- Nerve Conduction Velocity Studies (NCV)

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3
Q

Are EMG and NCV tests usually done together?

A

Normally yes, but they do provide different information

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4
Q

A NCV helps diagnose _____ damage or disease and is a measurement of how well electrical signals (APs) travel up/down _________ nerves.

A
  • nerve

- peripheral

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5
Q

A EMG determines __________ involvement, and is a measurement of how ________ responds to electrical signals (APs) both during rest and with activity.

A
  • myopathic

- muscle

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6
Q

Overall, what is the difference between an EMG and a NCV test?

A

NCV detects a problem with the nerve, whereas an EMG detects whether the muscle is working properly in response to the nerve’s stimulus.

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7
Q

The electrodiagnostic tests are in correlation and done after a ___________ and _____

A
  • physical exam

- PMHx (past medical history)

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8
Q

What can these electrodiagnostic tests help with in regards to neuropathic or neuromuscular disease?

A
  • time course of disease (acute vs chronic)
  • anatomical location of pathology
  • nature of pathology (axonal damage vs myelination, entrapment like carpal tunnel)
  • distribution (widespread or local)
  • physiological status of lesion (is PNS regenerating)
  • data for clinical/ lab research
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9
Q

What can NCV/EMG diagnose?

A
  • Motor Neuron Disease
  • Radiculopathy
  • Plexopathy
  • Neuromuscular Junction Disease
  • Muscle Disease
  • Ocular and Pharyngeal weakness
  • Neuropathy
  • Weakness in ICU
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10
Q

NERVE CONDUCTION VELOCITY STUDIES

A

NERVE CONDUCTION VELOCITY STUDIES

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11
Q

Strong AP have _______ messages, weak AP have ______ messages.

A
  • strong

- weak

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12
Q

What types of nerves does NCV tests look at?

A
  • look at large diameter, highly myelinated nerves

- median n., radial n., ulnar n., peroneal n., posterior tib n., sural n.

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13
Q

What are the two primary components of NCV tests?

A
  • motor NCV testing

- sensory NCV testing

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14
Q

Where is the recording electrode placed?

A

Over the muscle belly that is innervated by that nerve.

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15
Q

Where is the stimulator placed?

A

multiple places where nerve conduction would occur (armpit, elbow, wrist)

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16
Q

Do we care about a muscle twitch in NCV testing? Why?

A

No, nerve conduction tests are only looking at the peripheral nerve up until right before it innervates the muscle.

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17
Q

What do we care about in NCV testing instead of the muscle twitch?

A

Compound Motor Action Potential (CMAP)

-AP right before the muscle twitch occurs

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18
Q

What is the Compound Motor Action Potential a measure of?

A

the amplitude of the last AP (indicator of strength)

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19
Q

Why do we measure the amplitude of the AP at multiple sites (for example armpit, elbow, and wrist)?

A
  • The AP should generally be the same at all points, may see a little decrease.
  • We are concerned if we see the AP decreasing as it moves down.
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20
Q

What are two additional measurements we may look at when performing a NCV test other than amplitude?

A
  • latency (proximal and distal)

- conduction velocity (length/(proximal lat.-distal lat.))

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21
Q

What is latency?

What is it measured in?

A
  • Time it takes for the AP to travel from the point of stimulation to the recording electrodes
  • ms
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22
Q

What is conduction velocity?
What is it measured in?
How is it measured?

A
  • Also a reflection of the speed of AP
  • m/s
  • tape measure distance between point of stimulation and electrode and / by proximal latency-distal latency
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23
Q

What are the 2 things that impact latency and conduction velocity?

A
  • diameter of nerve

- myelin sheath

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24
Q
  • When conducting NCV tests, we want to aim for SUPRA-MAXIMAL stimulation, why is this?
  • How do we reach this point?
A
  • If we only provide a small electrical stimulation, we may be only recruiting half of the nerves and this could look like there is a reduction in the tests but we just didn’t wake the nerve up enough.
  • Gradually increasing stimulation until we see a peak of the amplitude (CMAP)
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25
Q

As we increase electrical stimulation, we will see an increase in the ______. Eventually we will see a leveling off of the amplitude of the CMAP, this will be the amount of electricity we use for the test.

A

-CMAP (compound motor AP)

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26
Q

When we are performing sensory NCV tests, what are we measuring instead of CMAP?

A

Sensory Nerve Action Potential (SNAP)

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27
Q

Are SNAPs or CMAPs larger in amplitude in general?

A

CMAP

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28
Q

What is the fallback of SNAP testing?

A
  • they tend to be more sensitive and liable to artifact

- artifact is a random recording you may see but isn’t indicative of anything

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29
Q

What is the positive of SNAP testing?

A

they are much more sensitive to mild or smaller lesions

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30
Q

What is an important concept with Sensory NCV testing?

A

concept of Orthodromically vs Antidromically

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31
Q

What is an orthodromic test?

A

testing the natural direction of sensory APs

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32
Q

What is an antidromic test?

A

testing the opposite direction of sensory APs

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33
Q

Which test is more common when testing sensory NCV, orthodromic or antidromic tests and why?

A

Antidromic

  • Examiner preference
  • Easier
  • Slight Higher Amplitude Responses
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34
Q

F wave and H-Reflex tests are both used to answer very _________ clinical questions.

A

specific

35
Q

The F waves are ________ “rebound” motor impulses that travel the full length of the motor axon and back.
The F wave tests are primarily used to evaluate _________ damage and demyelination.

A
  • retrograde

- proximal

36
Q

The H-Reflex is used to evaluate __________ and follows the muscle stretch reflex arc. This test can help in evaluating nerve ____ lesions and _______ motor neuron lesions. It is most common at the __ nerve root.

A
  • radiculopathy
  • root
  • UPPER
  • S1
37
Q

Basic Interpretations with NCV Studies

  • If we see changes in amplitude, that is related to the number of ________ in nerve.
  • If we see changes in latency (a marker of time), this is most affected by _____________ processes
  • If we see changes in conduction velocity (speed), this is affected by both ______ loss and ________.
A
  • axons
  • demyelinating
  • axon loss and demyelination
38
Q

If we are just seeing axonal loss, we will see a ________ loss in conduction velocity, when we have demyelination we will see a ___________ loss in conduction velocity.

A
  • moderate

- significant

39
Q

General Principles

  • Test both ________ and _______ nerve conduction
  • Test several __________ of the nerve
  • Test the ____________ side
  • Test __________ nerves
  • Interpret the results in context with the _____________ of the suspected disorder
A
  • sensory and motor
  • segments (motor)
  • contralateral for baseline
  • multiple
  • time course
40
Q

What are limitations of NCV testing?

A
  • easily affected by age, temp (cold = slower), obesity, edema
  • must be diligent about electrode placement
41
Q

ELECTROMYOGRAPHY (EMG)

A

ELECTROMYOGRAPHY (EMG)

42
Q

What does EMG test?

A

electrical activity of muscles

43
Q

EMG assists in diagnosis of conditions that interfere with muscular ___________.

A

contraction

  • diseases that affect the muscle (dystrophies)
  • diseases that affect the NM junction (myasthenia gravis)
  • diffuse nerve disorders that cause peripheral neuropathies
  • disorders that affect the motor neurons (anterior horn cells) in the spinal cord
44
Q

Where is EMG helpful?

A

gives additional diagnostic and prognostic info about the neuropathic conditions

45
Q

Is EMG an invasive test?

A

Yes, causes mild discomfort from needle inserted into muscle belly

46
Q

The display screen of an EMG has both __________ and _________ displays.

A
  • visual

- auditory

47
Q

What is the EMG procedure?

A
  • small wire like needle inserted into muscle belly
  • look at insertional activity
  • look at muscles at rest (fasciculations and fibrillations)
  • look at muscles when activated
48
Q

What is a motor unit?

A

cell body, dendrites of a motor neuron, the multiple axons, and the muscle fibers that it innervates

49
Q

What is a motor unit action potential (MUAP)?

Are all MUAPs alike?

A
  • summed electrical activity of all muscle fibers activated within a motor unit
  • No, can see variations in amplitude, duration, configuration. This is due to muscle fiber sizes and number of fibers.
50
Q

As the needle is inserted into the muscle belly, we have ________ activity, which is a burst of positive and negative spikes.

A
  • insertional (50-200ms)

- sounds like static

51
Q

_______ is golden when performing an EMG at rest

A

silence

52
Q

Healthy muscle at rest is generally electrically silent when the needle electrode is not moving. However there is normal ___________ activity that can be represented by what 3 terms?

A

-spontaneous

  • Motor End Plate Potential (MEPP)
  • End Plate Potential (EPP)
  • End Plate Spike (EPS)
53
Q
  • Is it a good thing when you see MEPP, EPP, and EPS?

- Where can this be important?

A
  • Yes, shows there is a portion of muscle that is innervated
  • things such as hysterical paralysis where there is nothing wrong neurologically to see there is some innervation occuring
54
Q

Abnormal Muscle Activity At Rest

  • Decrease in normal insertional activity is associated with loss of ____________ and has also been noted in ____________ disorders.
  • Increase in normal insertional activity is associated with ________ or ____________ disorders
  • Prolonged insertional activity can mean there is post acute ___________, __________ muscle disorders, or muscular ____________
A
  • muscle fibers, metabolic
  • neuropathic or myopathic
  • denervation, inflammatory, dystrophy
55
Q

Electrical activity other than MEPPs and EPPs in muscle at rest is indicative of what?

A

neuropathy or myopathy

56
Q

The most common abnormal electrical activity that is seen at rest is what?

A

fibrillation

57
Q

Fibrillation are __________ discharges that are usually ____ muscle fiber that can arise for several reasons.

A
  • spontaneous

- one

58
Q

Fibrillations are thought to be caused by an unstable muscle fiber ___________.

A

membrane

59
Q

Fibrillations are usually seen - weeks after an injury

Fibrillations can be due to both ________ and ___________ conditions.

A
  • 2 to 3 weeks

- myopathic and neuropathic

60
Q

What types of waves are closely associated with fibrillation?

A

positive sharp waves

61
Q

What are fasciculations?

A

spontaneous, repetitive, twitchlike contractions of the examined muscle at rest

62
Q

Are fasciculations indicative of pathologies?

What is a fasciculation akin to?

A
  • No, not necessarily

- twitch

63
Q

As opposed to fibrillations, fasciculations are more often than not associated with ___________ fibers.
Fasciculations occur - days after denervation.

A
  • multiple

- 2 to 3 days

64
Q

What is a very common time we see fasciculations?

A
  • disease involving alpha motor neurons

- also seen with chronic demyelnation

65
Q

What are 3 other uncommon abnormal activities we may see at rest?

A
  • complex repetitive discharge
  • myokymic
  • myotonic
66
Q

What is complex repetitive discharge?

A
  • spontaneous discharges of several different muscle fibers firing asynchronously but doing it at the same sequence every time
  • this results in a “machine gun” like sound on EMG
67
Q

Complex repititive discharge is generally seen with ________ conditions.

A

chronic

68
Q

What is myokymic?

A
  • groups of recurring spontaneous motor APs that fire in a repetitive burst pattern
  • results in a “marching soldier” like sound on EMG
69
Q

What is myotonic?

A
  • rhythmic discharges arising from spontaneous muscle fibers
  • amplitude and frequency constantly rise and fall
  • specifically related to myotonic diseases (rare)
70
Q

You can characterize the origin of EMG potentials as firing _____ or firing _________.

A
  • alone

- in groups

71
Q

Which of the EMG potentials are “firing alone”? (one motor unit)

A
  • end plate spikes
  • fibrillation
  • myotonic discharges
72
Q

Which of the EMG potentials are “firing in groups”? (multiple motor units)

A 
Adjacent muscle fibers
-complex repetitive discharge
-insertional activity
Motor Unit Potentials
-fasciculation potentials
-myokymic discharges
-neurotonic discharges
73
Q

If you need to produce a bigger muscle contraction you need to fire ____ muscle fibers and ________ APs.

A
  • more

- stronger

74
Q

Normally, our motor unit APs will be _________ or ___________.

A
  • biphasic or triphasic (moreso triphasic)

- biphasic and triphasic is how many turns in the EMG

75
Q

If we ever see more than 3 phases to an AP propogation, that is indicative to ________.

A

pathology

76
Q

The motor unit AP is a sum of ________ smaller APs because a motor unit innervates multiple __________, each has its own AP.

A
  • multiple

- muscle fibers

77
Q

The muscle fibers in a healthy muscle belly will contract ______, so the APs are happening at the _______.

A
  • in sync

- same time

78
Q

Temporal Course of MUAP Changes - Neurogenic

  • If 2 nerves are innervating a muscle belly and 1 of them stops, we will see ________ recruitment resulting in a worse contraction, but we will see an ________ in firing rate from the still intact nerve.
  • The intact nerve will start to _______ sprout to help the denervated muscle fibers 1 month after. These contractions may be _______ however, resulting in a _________ AP.
  • 2 months after we see that is is still ________ and longer spread out durations of the ____.
  • 6 months after we see that it goes back to normal __________ setup. The main difference is that the amplitude and duration are ________ than where we started, why?
A
  • reduced, increased
  • collaterally, out of sync, polyphasic
  • polyphasic, APs
  • triphasic, larger, because we have 1 nerve with 2x as many muscle fibers it has to innervate
79
Q

Polyphasic MUAP are indicative of ________ occuring.

A

neurogenesis

80
Q

Myopathic conditions occur when you see a ________ in the number of viable muscle fibers.

A

decrease

81
Q

Lower muscle fibers results in a lower _____.

A

MUAP

82
Q

The remaining available muscle fibers will _______ due to the myopathic conditon.

A

shrink

83
Q

MUAP is dependent on _____ and ____ of muscle fibers.

A

number and size

84
Q

MUAP amplitude and duration will _______ in response to decrease in number and size of muscle fibers. We will also see an _______ in the number of phases seen from the triphasic wave.

A
  • decrease

- increase

Neuroanatomy and Physiology (19 decks)

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