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Advanced diagnostics > Week 8 > Flashcards

Week 8 Flashcards

1
Q

What is the function of electrophysiological testing?

A

Assesses the function and

structural integrity of the peripheral nervous system and is an extension of the clinical exam

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2
Q

What are the components of electrophysiological testing?

A
  • Nerve conduction studies (NCS)

* Electromyography (EMG)

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3
Q

Electrophysiological testing provides information on the characterization of lesion, including what?

A
  • Localization of lesion in the peripheral nervous system
  • Type of nerve fibers involved: motor, sensory or mixed involvement
  • Components of nerve fibers injured: Axonal, demyelinating injury or both
  • Severity of injury can be assessed.
  • Prognosis can be estimated
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4
Q

How can we use electrophysiological testing to characterize the severity of an injury?

A

By frequently used published grading scales, specifically for median mononeuropathy at the wrist, and ulnar neuropathy at the elbow.

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5
Q

When can we determine the chronicity of an injury using electrophysiological testing?

A

If there is an axonal injury, we can determine chronicity, and give the referring provider information about prognosis.

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6
Q

Using electrophysiological testing, what is the use of serial studies?

A

Serial studies may quantify the effect of treatment and progression of healing in more severe or complex nerve injuries

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7
Q

What is electrophysiological testing also used for?

A

Assess for/diagnose myopathy and neuromuscular junction

disorders, such as myasthenia gravis

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8
Q

What type of information does electrophysiological testing provide?

A

It provides complimentary, yet different information, than imaging. It evaluates the physiological function of the nerve and muscle in real time.

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9
Q

Electrophysiological testing is not a stand alone procedure. What are the results of an electrophysiological testing taken in context with?

A

The results are taken in context with the clinical exam, and other diagnostic procedures or imaging.

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10
Q

What is electrophysiological testing highly sensitive towards?

A

Highly sensitive indicator of early nerve injury, and is highly localizing, capable of localizing lesions within 1-2 cm

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11
Q

When is the use of electrophysiological testing highly useful?

A

Clarifies clinical scenarios when one disorder mimics another

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12
Q

What is electrophysiological testing useful for?

A

• Identifies combined multi-site injury, avoiding missed
diagnoses
• Identifies more global neuromuscular injury with focal onset
• Provides longitudinal data for charting course, response to
therapy
• Detects dynamic and functional injury missed by MRI

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13
Q

How can electrophysiological testing be useful in a pt with severe nerve injury?

A

It can be helpful to track progress of healing nerves, managed either with or without surgery

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14
Q

What are the limitations of electrophysiological testing?

A

• Not all components of the peripheral nervous system are
assessed
• Only large myelinated nerve fibers (IA) assessed with Nerve Conduction studies: sensory and motor fibers
• Many nerves are not amenable to NCS
• Only Type I muscle fibers assessed with needle EMG
• Does not assess CNS, but it can assess for peripheral nerve lesions in pts with pre-existing CNS lesions

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15
Q

What types of nerves does electrophysiological testing NOT assess?

A

Temperature, pain fibers are not assessed (Type III)

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16
Q

What are the factors that can affect the conduction velocity of an axon?

A
  • Diameter of axon
  • Thickness of myelin
  • Internodal distance
  • Temperature
  • Age
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17
Q

How can we get an erroneous false positive in while electrophysiological testing?

A

The colder temperature in some parts of the body, can appear to have abnormal slow nerve conduction velocity

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18
Q

How can we evaluate for a lesion at the posterior primary rami using electrophysiological testing?

A

By assessing the paraspinal muscles with needle EMG. This is one of the primary ways to distinguish a radiculopathy from other conditions.

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19
Q

What is included in a motor unit?

A

One nerve fiber (axon) and all the muscle fibers it innervates. Ration may vary, with there being a 1:1 ratio in the face and 1:1000 in the leg muscles

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20
Q

How do we assess motor units with electrophysiological testing?

A

Motor units can be assessed with electromyography

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21
Q

What are the possible pathologies that can be found in the anterior horn cell with the use of electrophysiological testing?

A

Amyotrophic lateral sclerosis (ALS)

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22
Q

What are the possible pathologies that can be found in the nerve root with the use of electrophysiological testing?

A

Radiculopathy

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23
Q

What are the possible pathologies that can be found in the plexus with the use of electrophysiological testing?

A

Plexopathy

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24
Q

What are the possible pathologies that can be found in the peripheral nerve with the use of electrophysiological testing?

A

Mononeuropathy or polyneuropathy

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25
Q

What are the possible pathologies that can be found in the neuromuscular junction with the use of electrophysiological testing?

A

Myasthenia gravis

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26
Q

What are the possible pathologies that can be found in the muscles with the use of electrophysiological testing?

A

Myopathy

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27
Q

Part of the equipment used in electrophysiological testing is a pre-amplifier. What is the purpose of this?

A

We plug the electrodes into them, and it functions to convert very low amplitude biological potentials, to higher voltage copies, so they can be viewed

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28
Q

Part of the equipment used in electrophysiological testing is a stimulator. What is the purpose of this?

A

It is used during nerve conduction studies to deliver the stimulus, to trigger an action potential, which we’re then able to record, using electrodes plugged into the pre-amplifier

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29
Q

One of the components of electrophysiological testing is nerve conduction studies. What does this involve?

A

Recording and measurement of a compound nerve and
compound muscle action potential elicited in response to a single supramaximal electrical stimulus under standardized conditions

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30
Q

What can nerve conduction studies be used to assess?

A

Motor and sensory fibers assessed
• Motor nerve conduction study (MNCS)
• Sensory nerve conduction study (SNCS)

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31
Q

How is nerve conduction studies performed?

A

Nerve is artificially stimulated with an electrical current
which generates an action potential, using a stimulator which contains a cathode and an anode, and with electrical current flowing between the two poles, the cathode depolarizes the nerve, and the anode hyperpolarizes the nerve

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32
Q

What is an evoked potential and when is it recorded?

A

The recorded response obtained from a nerve conduction study. It is recorded as the electrical event, or the action potential passes under the recording and reference electrode

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33
Q

What is sensory nerve action potential (SNAP)?

A

The potential recorded from a sensory nerve

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34
Q

What are the different ways to get an evoked potential from the sensory nerve/different ways a SNAP can go?

A
  • Orthodromic: AP propagated in the same direction as physiologic conduction
  • Antidromic: AP propagated in opposite direction to physiologic conduction
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35
Q

What is a compound muscle action potential (CMAP)?

A

The potential recorded from a muscle

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36
Q

There are several evoked potential parameters in the NCS. What does the parameter: latency involve?

A

Time lapse from the stimulation to the response. (how fast the nerve is carry the signal from the delivery of the stimulus, until the potential reaches the recording electrode). This is measured in milliseconds.

  • Motor = distal motor latency = DML
  • Sensory = distal sensory latency = DSL
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37
Q

There are several evoked potential parameters in the NCS. What does the parameter: amplitude involve?

A

Sum total of all the fibers (nerve or muscle) recorded from baseline to peak. (how big of a response/trigger is created). It measures from baseline to peak

38
Q

What is the amplitude of a potential related to?

A

Information about the number of axons functioning/firing

39
Q

There are several evoked potential parameters in the NCS. What does the parameter: duration involve?

A

Initial deflection of the negative
phase to the return of the positive phase. (time period the potential occurs/how quickly the nerve is repolarizing). Should be the same under normal

40
Q

There are several evoked potential parameters in the NCS. What does the parameter: velocity(speed) involve?

A

The speed at which the potential carries its signal across the nerve, not the NMJ. Meters/second = m/sec

41
Q

True or False

Nerve conduction velocity (NCV) for the chemical event of a motor nerve cannot be calculated across the NMJ

A

True, Nerve conduction velocity (NCV) for the chemical event of a motor nerve cannot be calculated across the NMJ, therefore we can only calculate the NCV for segments proximal to the NMJ, and will be expressed as a latency only

42
Q

What are the steps to completing an orthodromic Sensory Nerve Conduction Study on the median nerve?

A

• Place recording electrode (black) over the median n proximal to the wrist
- Reference electrode (red) placed 2 cm proximally
- Ground – back of hand
• Measure distance from recording electrode to stimulator (cathode), 140 mm (14 cm)
• Stimulate Median n at the digital branches of D2
- Wrist DSL - latency in msec
- Amplitude of sensory nerve action potential (SNAP) in microvolts (uV)
• Stimulate Median n at the palm
- Palmar DSL
- Amplitude of SNAP
• Distance from palm to wrist stimulation sites: 7 cm
• Calculate velocity, SNCV palm to wrist

43
Q

On a chart depicting Sensory Nerve Conduction Study, what is usually on the x-axis?

A

Time in milliseconds

44
Q

On a chart depicting Sensory Nerve Conduction Study, what is usually on the y-axis?

A

Amplitude in microvolts

45
Q

In the typical data table seen in an EMG nerve conduction report, what is found at the top?

A

Nerve tested and recording location

46
Q

What is considered normal for the distal sensory latency fro the wrist, in regards to the median nerve?

A

Less than 3.6 millisecs

47
Q

What is normal amplitude of the median nerve at the palm?

A

Anything over 15 microvolts

48
Q

What are the steps to completing an orthodromic motor Nerve Conduction Study on the median nerve?

A

• Place recording electrode (black) on distally innervated muscle (for Median n, use APB)
- Reference electrode (red) placed 2 cm distally
- Ground – back of hand
• Measure distance from recording electrode to stimulator (cathode), DML = 80 mm (8 cm)
• Stimulate Median n at the wrist
- DML - latency in msec
- Amplitude of compound muscle action potential (CMAP) in millivolts (mV)
• Stimulate Median n at the elbow (cubital fossa)
- Elbow latency
- Amplitude of CMAP
• Measure distance from elbow to wrist stimulation sites
• Calculate velocity, MNCV Elbow to Wrist

49
Q

What are the components of temperature that affects nerve conduction studies?

A
  • Fingers should be higher than 31 degrees C
  • Toes should be higher than 29 degrees C
  • Cold slows NCV, warm increases NCV
50
Q

What are the components of age that affects nerve conduction studies?

A
  • Most nerves mature by 5 years (14 years)
  • Below 5 years, NCV is slower (charts for peds)
  • After age 40 years - mild slowing
  • After age 70 years - significant slowing
51
Q

What are the components of proximal vs. distal that affects nerve conduction studies?

A
  • NCV is faster in UE > LE, speeds get slower the more distal you go
  • Nerves are shorter, diameters larger in UEs
  • Temperature is higher in UEs
52
Q

What are the nerves in the UEs that are routinely evaluated with motor nerve conduction studies?

A
  • Median
  • Ulnar
  • Radial
  • Axillary
  • Musculocutaneous
  • Suprascapular
53
Q

What are the motor nerves in the LEs that are routinely evaluated with motor nerve conduction studies?

A
  • Tibial
  • Fibular (deep/superficial)
  • Femoral
  • Medial/lateral plantar
54
Q

What are the nerves in the UEs that are routinely evaluated with sensory nerve conduction studies?

A
  • Median
  • Ulnar
  • Superficial Radial
  • Medial Cutaneous N of Forearm (MABC)
  • Lateral Cutaneous N of Forearm (LABC)
  • Dorsal ulnar cutaneous nerve (DUC)
55
Q

What are the nerves in the LEs that are routinely evaluated with sensory nerve conduction studies?

A
  • Sural
  • Superficial fibular
  • Medial/lateral plantar nerves
  • Saphenous
56
Q

What is electromyography (EMG)?

A

Recording and study of insertional, spontaneous and
voluntary electrical activity of muscle using a needle
electrode

57
Q

In an electromyography (EMG), we evaluate each muscle under 3 different conditions. What are they?

A
  • Insertion
  • Rest
  • Voluntary Contraction to include both minimal, and maximal
58
Q

In an electromyography (EMG), what does the number of muscles studied depend on?

A

Depends on the suspected condition and findings as the test progresses

59
Q

____ is the most important assessment tool for suspected radiculopathy

A

Electromyography (needle EMG) is the most important assessment tool for suspected radiculopathy

60
Q

What is the biggest predictor of abnormalities on needle EMGs?

A

True weakness on a manual muscle test

61
Q

What should be the EMG presentation of a muscle at rest?

A

Muscle should be quiet/electrically silent

62
Q

What is electrical activity at rest suggestive of?

A

Muscle membrane instability, which most commonly occurs when the axonal supply to a muscle has been disrupted

63
Q

What can abnormal spontaneous activity seen in a muscle be attributed to?

A
  • Fibrillation potentials

* Positive sharp waves

64
Q

True or False

Needle EMG cannot detect demyelination

A

True, Needle EMG cannot detect demyelination

65
Q

What is the best study for detecting demyelination?

A

Nerve conduction study

66
Q

What type of nerves is tested with needle EMG?

A

Muscles and motor nerves

67
Q

What is muscle membrane instability usually indicative of?

A

Axonal pathology, and it often indicates the presence of acute denervation with ongoing
axonal injury

68
Q

What is a Motor Unit Action Potential?

A

Waveform produced by motor units with muscle activation

69
Q

What assessing a Motor Unit Action Potential, what are the variables that we look at?

A

Amplitude, duration, morphology, recruitment pattern, and interference pattern are assessed

70
Q

What does the deviation from normal in particular patterns of the Motor Unit Action Potential do?

A

Deviation from normal in particular patterns assists in the
characterization of neuromuscular pathology
• Often helps determine chronicity of injury
• Can provide information on nerve healing: reinnervation

71
Q

What is the firing rate of a motor unit?

A

Motor units fire at a rate of about 5-12 Hz

72
Q

When are additional motor units recruited Motor Unit Action Potential?

A

As force production increases, additional motor units are recruited (>10-12 Hz)

73
Q

What happens when there are no additional motor units to be recruited in a Motor Unit Action Potential?

A

If additional motor units aren’t available due to axonal injury, remaining motor units fire at much higher frequency: reduced recruitment

74
Q

On an EMG chart, what are the marks Ins Act, Fibs, Psw tell us?

A

It tells us how the muscle behaves at rest

75
Q

What does Ins Act, Fibs, and Psw stand for?

A
  • Ins Act: Insertional activity
  • Fibs: Fibrillation
  • Psw: Positive shock wave
76
Q

When there is an ongoing axonal injury, what is the presentation on the electromyography?

A

Presence of increased insertional activity (Ins Act), fibrillation potentials (Fibs) and
positive sharp waves (PSW)

77
Q

What does an abnormal amplitude on an electromyography show?

A

An abnormal amount shows an axonal injury, because amplitude shows the number of axons firing

78
Q

What does an abnormal/decreased velocity axon show?

A

A problem with the axon myelin

79
Q

What are the times that which an EMG reports electrical activity?

A
  • Insertional
  • Spontaneous (Rest) which should be quiet if not silent
  • Voluntary (Recruitment) at min and max threshold, including the amplitude(size), duration and shape
80
Q

What are the things that can result in an EMG at rest not being quiet/silent?

A
  • Muscle membrane instability
  • Axonal disruption
  • Acute denervation
81
Q

How long does it take for a radiculopathy to show up on a NCV/EMG?

A

About 4 weeks

82
Q

An EMG/NCV is more indicated for what type of presentations?

A

Mono-neuropathy, more than a Carpal Tunnel Syndrome

83
Q

What are the most common findings on a NCV?

A
  • Prolonged distal latency which is an indication of a focal demyelination
  • Decreased Amplitude which is an indication of an axonal Injury
  • Slowed NCV which is an indication of a small or longer- demyelination
84
Q

What are the most common findings on an EMG?

A
  • Increased insertional which is an indication of an ongoing axonal
  • Decreased Recruitment: motor units lost due to axonal injury
  • Polyphasic MUAP which is an indication of an older axonal injury, some recovery
85
Q

When should an EMG/NCS be requested?

A
  • When the diagnosis is unclear, despite a good clinical history and exam
  • When pathology is worth revealing and evidence dictates a different management strategy
86
Q

When should an EMG/NCS NOT be requested?

A
  • Not when the diagnosis is obvious unless you are concerned about a prognosis, or you desire to better identify a process/and or its severity- such as a neuropathy
  • Not unless a good history and clinical exam has been completed
  • Not unless the results are going yo change your management
  • Not for screening purposes
87
Q

What does a fMRI measure?

A

The amount of oxygen that is being consumed in the blood. It light up the areas of most active oxygen consumption

88
Q

What does BOLD in fMRI?

A

Blood Oxygen Level Dependent. The measure of oxygenation in the blood and is used by the fMRI

89
Q

What is a voxel?

A

A geographic region of the brain that might have a thousand axons in it, used by the fMRI

90
Q

What is fMRI used for in research PT?

A
  • Pain Mechanisms
  • Mechanism of Manual Therapy
  • Brain related tasks: memory, learning, fine motor control
91
Q

What is the clinical use of fMRI in PT?

A
  • Surgical planning

* Central nervous system pathology

Advanced diagnostics (8 decks)

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