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MI Differential Diagnosis & Med Screening > Electromyography for Differential Diagnosis > Flashcards

Electromyography for Differential Diagnosis Flashcards

1
Q

What IS EMG?

Components broken down

A
  • Graphy→ measurement & analysis
  • Electro→ electrical properties and signals
  • Myo→ muscle*
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2
Q

3 Types of EMG:

A
  1. EMG Biofeedback
  2. Kinesiologic EMG
  3. Diagnostic EMG=> EDX***
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3
Q

Basic Definition:

EMG Biofeedback

A
  • Electrical detection of mm activation & provides qualitative info on status of muscle contraction
    • GOAL: reduce pain/spasm OR improve motor control & strength
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4
Q

Basic Definition:

Kinesiologic EMG

A
  • Fine wire intramuscular & surface electrodes
  • Analysis of activation of mm’s w/in postural tasks, functional mvmts, work, conditions, tx/training regimes
  • Think videogames!
    • Researchers, sport scientists, graphic artists, product designers*, rehab practitioners
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5
Q

Basic Definition:

Diagnostic EMG=> EDX*

A
  • Electrodiagnostic Examination
  • 1.Needle EMG & 2.Nerve Conduction Studies (NCS)
  • Analysis of depolarization of nerve & mm’s to determine functional integrity of NMSK system and Peripheral System
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6
Q

2 Components of EDX (Dx EMG)

A
  1. Needle EMG
  2. Nerve Conduction Studies (NCS)
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7
Q

EDX used in conjunction w/:

A
  • w/ Hx, clinical exam and other tests to establish definitive dx** in **peripheral neurologic and mm disorders
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8
Q

Medical Necessity of EDX

Pt Signs, Symptoms, & Hx that warrant EDX

A

See pics and common themes!!!

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9
Q

Medical Necessity of EDX

Common Medical Dx where EDX are Utilized:

A

see pics and note the differences and similarities in Dx’s !!!

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10
Q

EDX vs. Other Assessment Tools

How do they compare?

Looking @ Sn and Sp

A
  • Sn== our TRUE POSITIVE rate
    • opp would be False Negatives
  • SP== our TRUE NEGATIVE rate
    • opp would be False Positives
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11
Q

Ex. Clinical Scenario 1

A
  • Diff Dx?
    • B CTS vs peripheral polyneuropathy
  • More approp interventions to address recent exacerbation?
    • Tx hand dysf as per CPG
    • Education & referral to PCP for med mgmt
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12
Q

Clinical 1 and outcomes of EDX

A
  • Outcomes:
    • ID presence of nerve injury or mm disease
    • ID which nerves or muscles are damaged
    • Characterize lesion
      • Fiber type & severity
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13
Q

EDX Component

Nerve Conduction Studies

2 Functions:

A
  1. Measure how well a peripheral nerve can conduct an induced stimulus=> evoked potential
  2. Electrically stimulate/activate nerve @ various pts along superficial path of nerve & record output @ target organ
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14
Q

The second function of Nerve Conduction Studies is Electrically stimulate/activate nerve @ various pts along superficial path of nerve & record output @ target organ

More to this?

A
  • Target organ:
    • Muscle→ MOTOR nerve conduction study
    • Skin→ SENSORY nerve conduction study
    • ENTIRE nerve pathway→ Late responses (H-reflex & F-wave)
      • Stim nerve distally & record output of nerve→ cell body→ muscle
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15
Q

NCS: What does this look like?

Ex. EDX Component: NCS

Ex. Median Motor nerve

A

Median Motor Nerve

Recording from APB w/ stim @ wrist, elbow, axilla

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16
Q

EDX Component: NCS

Median f-wave vs. Tibial H-reflex

GOOGLE DIFFERENCE bw F-wave and H-reflex

A

see pics

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17
Q

F- Wave

A
  • Useful for evaluating conduction probs in prox region of nerve
  • One of several motor responses which may follow direct motor response evoked by electrical stim of peripheral motor or mixed nerves
  • Always preceded by a motor response
  • Best obtained in small foot and hand mm’s.
  • Helpful w/ presence of polyneuropathy
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18
Q

H-reflex

A
  • Can be accomplished w/ slow, long-duration stimuli w/ gradually inc’ing stim strength
  • Provide nerve conduction measurements along entire length of nerve
  • Can demo abnorms in neuropathies and radiculopathies
  • easily obtained in Soleus (w/ post tib nerve @ pop. fossa), FCR (w/ median nerve stim @ elbow), Quads (w/ femoral nerve stim)
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19
Q

NCS QUANTitative Data

3 MOST COMMONLY Used:

A
  1. Distal Latency→ Speed, Strength of nerves
  2. Conduction Velocity → How fast and distance traveled
  3. Amplitude→ How strong
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20
Q

NCS QUANTitative Data:

3 MOST COMMONLY Used:

Distal Latency (think speed, strength)

A
  • Time it takes for electrical signal to reach target tissue from the most distal pt of stimulation
    • Miliseconds (ms)
      • Onset latency (O)→ MNCS (motor), SNCS (sensory)
      • Peak latency (P)→ SNCS (sensory)
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21
Q

NCS QUANTitative Data:

3 MOST COMMONLY Used:

Conduction Velocity (think how fast + distance traveled)

A
  • Time it takes for electrical impulse to travel BETWEEN 2 given points along course of nerve
    • Meters per second (M/s)
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22
Q

NCS QUANTitative Data:

3 MOST COMMONLY Used:

Amplitude (think how Strong)

A
  • Measure of how many working axons are activated when nerve is electrically stim’d
    • Microvolts or milivolts (uV or mV)
    • Onset to peak (O→P)→ MNCS, SNCS
    • Peak to trough (P→T)→ SNCS
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23
Q

NCS QUANTitative Data:

3 MOST COMMONLY Used:

EXAMPLE CHART

A

see pics!!!

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24
Q

NCS Data Interpretation

What does Myelin do?

A

INC speed of nerve conduction!

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25
Q

NCS Data Interpretation

If its a prob w/ “how fast”

A

Myelin problem

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26
Q

NCS Data Interp.

If its a problem w/ SIZE (amplitude)

A

Usually AXON problem

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27
Q

NCS Data Interpretation

Absolute vs. Relative values of patient

A

Compare each relevant data point to Normal

  • Absolute values→ determined by research
  • Relative values of patient→ Ipsilat an Contralat***
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28
Q

NCS Data Interpretation

SLOW speed of nerve impulse @ only one location of nerve==>

A

Focal demyelinating injury of THAT nerve @ THAT location

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29
Q

NCS Data Interpretation

SLOW speed of a nerve impulse @ MULTIPLE loc’s of a nerve and/or multiple nerves==>

A

Widespread demyelinating disorder

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30
Q

NCS Data Interpretation

LOW amplitude potential of nerve impulse @ ALL stimulation sites==>

A

Probable destroying of nerve axons/muscle fibers***

31
Q

Scenario I EDX Data

  • B (R>L) median motor slow (prolonged) distal (wrist) latency
  • B (R>L) median sensory slow wrist latency
  • B (R>L) median sensory slow wrist to digit 3 & wrist to palm velocity
  • All other NCS & EMG performed Normal
A

Influence on Mgmt

  • Even though pt has established medical dx of DM, the condition has not grossly affected the function of the large nerve fibers (motor & sensory)
  • Tx of impaired median N. according to CPG should improve pts sx’s
  • EDX CTS severity classification inverse relationship w/ success of conservative Tx
  • Majority (58%) of hand sxs required EDX BEFORE initial CTR consultation***
32
Q

Clinical Scenario #2:

A

Clinical Questions

  • Diff Dx?
    • L. C/S radiculopathy vs. L. CTS vs. L. plexopathy
  • Tx Focus?
    • Neck?
    • Wrist?
    • Shoulder?
33
Q

Final 2 Outcomes of EDX:

A

ID Location of insult

Determine stage of tissue inflammation

34
Q

GOLD STANDARD for assessing Axonal Integrity

A

Electromyography (EMG)

35
Q

EMG:

FACTS

A
  • Det’s integrity of all components of a motor unit:
    • alpha motor neuron, AXON (EMG is gold-standard), all mm fibers innervated by that motor neuron
  • INVASIVE→ needled recording electrode inserted thru skin and fascia INTO various depths of mm
  • Needle acts as antenna, detecting electrical impulses of motor units & machine displays as waveforms
36
Q

EMG (GOLD STANDARD for axonal integrity)

Examines 3 states of the muscle:

A
  1. @ Rest
  2. W/ MIN voluntary contraction
  3. INC’ing effort of voluntary contraction
37
Q

EMG Qualitative & Quantitative Data

3 Assessments:

A
  1. Resting assessment
  2. MINIMAL effort isometric muscle contraction
  3. MOD→MAX isometric muscle contraction
38
Q

EMG Qualitative & Quantitative Data

Resting Assessment

Norm vs Abnorm

A
  • NORMAL→ electrical silence @ rest
  • ABNORMAL→ presence of spontaneous potentials
    • Fibrillation potentials (fibs) & Positive sharp waves (PSW) most common***
39
Q

EMG: Resting Assessment

MOST COMMON ABNORMAL findings:

2:

A

Fibrillation potentials (fibs)

Positive sharp waves (PSW)

40
Q

EMG Qualitative & Quantitative Data

Minimal effort isometric contraction

A
  • Analyze shape, amplitude & duration of >12 indiv. motor unit APs (MUAPs)
    • Normal parameters for motor unit shape, amp, duration
    • >30%* of MUs need to be abnormal in order to label mm as such
41
Q

EMG Qualitative & Quantitative Data

MOD→MAX isometric muscle contraction

A
  • Observe rate of MU recruitment & # of MUs recruited
    • Depends on pt participation/motivation*** (obviously, probably doesn’t feel good!!!)
42
Q

EMG ABNORMAL Resting Assessment Potential==>

A

FIBS/PSW***

43
Q

EMG ABNORMAL Resting Assessment Potential==> FIBS/PSW

A
  • Physiologically the SAME, but appear as diff waveforms
  • Caused by mm fiber denervation→ electrical discharge of mm fiber w/out input from nerve
  • Severity subjectively graded 1+ to 4+
44
Q

EMG MINIMAL EFFORT ISOMETRIC MUSCLE CONTRACTION

ABNORMAL MU AP (Action Potential) Ex.

A
  • SIZE of MUAP (motor unit action potential) DOES NOT match muscle effort
  • >30%* of MUAP observed in a mm have abnormal size, width, and/or shape
45
Q

EMG: MODERATE-MAXIMAL ISOMETRIC CONTRACTION

ABNORMAL Recruitment & Interference Pattern Ex.

A

Just same MU firing over and over, no recruitment of new MUs

  • Reduced recruitment
    • Initial MUAP are LG.
    • As effort inc’s, FEW/NO other MUAP activated, existing ones fire faster
46
Q

EMG Interpretation Ex.

A

see pics and NOTE COLORS!!!

47
Q

Scenario 2 EDX Data

EMG + Interpration

A

Scenario 2 EDX Outcomes & Impression

48
Q

Scenario 2 EDX Outcomes & Impression

A

Scenario 2 EDX Influence on Management:

  • Evidence of extensive injury to lateral cord of brachial plexus
    • Primary intervention→ anterior cervical triangle & shoulder
    • Communicte w/ referring phys. for imaging
    • Passive tx/preventative measures/edu. for post. neck & wrist
  • High agreement bw EDX & MRI for plexopathies***
  • EDX optimal test to localize, grade, & provide pathophysiologic info on brachial plexus lesions***
49
Q

Clinical Scenario #3

2 pts similar, but different as well

A

BOTH pts present w/ high clinical suspicion of ulnar neuropathy @ elbow “cubital tunnel syndrome”

BOTH ask “When am I going to get better?”

50
Q

Name the 6 Clinical Outcomes of EDX

A
  1. ID presence of nerve injury/mm disease
  2. ID which nerve(s) or muscle(s) are damaged
  3. Characterize the lesion
  4. ID the location of insult
  5. Determine the stage of tissue inflammation
  6. Estimate prognosis
    1. *Determine cellular components injured
51
Q

Peripheral Nerve Cell Components

A
  • Cell Body
    • Generate nerve impulse
      • Ant. horn cell
      • DRG
  • Connective Tissue
    • Protection
  • Myelin (Schwann Cells in PNS!!!)
    • Protection
    • INC speed of nerve impulse
  • Axon
    • Transmits nerve impulse
52
Q

What heals faster?

Myelin regen vs. Axon regen

A

Myelin regeneration!!!

53
Q

Comparing Nerve Structure Repair

REmyelination==>

A

4mm/day ea. segment

54
Q

Comparison of Nerve Structure Repair

Axon regeneration==>

A

1mm/day entire axon

SLOOOOOOOOW***

55
Q

Prognostic Value of EDX

EDX can ID presence of:

3:

A
  1. Demyelination== Excellent to Good prognosis
  2. Axon Degeneration== Fair to Poor prognosis
  3. Axon reinnervation of mm fiber== Recovery underway/Intervention successful
56
Q

Prognostic Value of EDX

EDX can ID presence of:

Demyelination

A

Excellent→Good prognosis for recovery

  • Local→ slowing @ one location
  • Diffuse→ slowing @ multiple locations and/or nerves
  • Conduction Block→ slowing w/ changes in amplitude (potentials STOP conducting)
57
Q

Prognostic Value of EDX

EDX can ID presence of:

Axon Degeneration

A

Fair→Poor prognosis for recovery

  • DECd amplitude @ all nerve sites
  • Spontaneous EMG potentials
  • LESS MUs w/ faster firing rates (you saw this, just keeps repeating over and over w/ same MU….no NEW recruitment!)
58
Q

Prognostic Value of EDX

EDX can ID presence of:

Axon Reinnervation of muscle fiber

A

Recovery underway/Intervention Successful

  • Abnorm shape, amplitude, & duration of MUs==> mm fibers reorganizing (GOOD THING!)
  • DECd amp @ all nerve sites
59
Q

KNOW THIS CHART!!!!

Demyelination == QUICKER recovery vs. Axon loss

A

see chart!!!!!

60
Q

Scenario 3A (baseball pitcher) EDX Findings

Vs.

A

Scenario 3B (retired couch potato) EDX Findings

61
Q

Scenario 3 EDX Outcomes, Impression, Management

SEE how they are different!!!!

A

Note the diff’s in severity of injury and treatment plans and prognoses!!!

62
Q

REVIEW: Clinical Implications of EDX

6 Outcomes of EDX

A
  1. ID presence of nerve injury/mm disease
  2. ID which nerve(s) or muscle(s) are damaged
  3. Characterize lesion
  4. ID the location of insult
  5. Determine the stage of tissue inflamm.
  6. Estimate prognosis
63
Q

REVIEW: Clinical Implications of EDX

NCS optimal for:

A

Optimal for detecting DEMYELINATION***

64
Q

OPTIMAL for detecting demyelination

A

NCS

65
Q

REVIEW: Clinical Implications of EDX

Optimal for detecting AXON DAMAGE (WORSE prognosis)

A

EMG

66
Q

Optimal for detecting AXON damage

A

EMG

67
Q

NCS optimal for detecting______

A

Demyelination

68
Q

EMG optimal for detecting _______

A

AXON DAMAGE (worse prognosis)

69
Q

REVIEW: Clinical Implications of EDX

EDX Facts:

A
  • VERY HIGH Sn & Sp @ detecting UE compression neuropathies encountered by PTs***
  • Results can alter pt mgmt***
70
Q

Summary of EDX Influence

Did it work? and for what?

A

see pics + highlights***

71
Q

Components of an EDX Report:

A
  • Pt demographic, reason for referral/Hx & clinical exam
  • NCS Data:
    • Numerical table format→ latency, amplitude, velocity
    • norm values
    • temperature
  • EMG Data:
    • Table format description→ spontaneous & volitional activity of ea. muscle
  • Summary of findings
  • Impression*
    • Nerve(s) injured, Location, Axon/Myelin, Motor/Sensory, Chronicity, Severity***
72
Q

EDX Report

Impression of Findings tells you….

A

Nerve(s) injured, Location, Axon/Myelin, Motor/Sensory, Chronicity*, Severity*

73
Q

Role of PT in EDX

A

see pics

74
Q

Prolonged F-wave

A

Prolonged F-wave latency consistent w/ demyelinating of the motor axon bw the stimulus site and the recording muscle

Ex. Demyelinating polyradiculoneuropathy or demyelination in other causes of radiculopathy

MI Differential Diagnosis & Med Screening (12 decks)

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