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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
NCS Data Interpretation ## Footnote **If its a prob w/ “how fast”**
Myelin problem
26
NCS Data Interp. ## Footnote **If its a problem w/ SIZE (amplitude)**
Usually **AXON problem**
27
NCS Data Interpretation ## Footnote **Absolute vs. Relative values of patient**
Compare each relevant data point to **Normal** * **_Absolute_ values→ determined by research** * **_Relative_ values of patient→** Ipsilat an Contralat\*\*\*
28
NCS Data Interpretation ## Footnote **SLOW _speed_ of nerve impulse @ _only one location of nerve_==\>**
_Focal_ **demyelinating injury** of THAT nerve @ THAT location
29
NCS Data Interpretation ## Footnote **SLOW speed of a nerve impulse @ _MULTIPLE loc's_ of a nerve and/or _multiple nerves_==\>**
**_Widespread_** demyelinating disorder
30
NCS Data Interpretation ## Footnote **LOW _amplitude potential_ of nerve impulse @ ALL stimulation sites==\>**
Probable **destroying** of nerve **axons/muscle fibers\*\*\***
31
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
**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
Clinical Scenario #2:
Clinical Questions * Diff Dx? * L. C/S radiculopathy vs. L. CTS vs. L. plexopathy * Tx Focus? * Neck? * Wrist? * Shoulder?
33
Final 2 Outcomes of EDX:
ID **Location of insult** Determine **stage of tissue inflammation**
34
**GOLD STANDARD for assessing _Axonal Integrity_**
Electromyography **(EMG)**
35
EMG: ## Footnote **FACTS**
* 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
EMG (GOLD STANDARD for **axonal integrity)** ## Footnote **Examines 3 states of the muscle:**
1. @ Rest 2. W/ **MIN voluntary contraction** 3. **INC'ing effort** of voluntary contraction
37
EMG **Qualitative & Quantitative Data** ## Footnote **3 Assessments:**
1. Resting assessment 2. MINIMAL effort isometric muscle contraction 3. MOD→MAX isometric muscle contraction
38
EMG **Qualitative & Quantitative Data** ## Footnote **Resting Assessment** **Norm vs Abnorm**
* **NORMAL→** electrical _silence_ @ rest * **ABNORMAL→** presence of _spontaneous_ potentials * Fibrillation potentials (fibs) & Positive sharp waves (PSW) **most common\*\*\***
39
EMG: Resting Assessment ## Footnote **MOST COMMON ABNORMAL findings:** **2:**
Fibrillation potentials (fibs) Positive sharp waves (PSW)
40
EMG **Qualitative & Quantitative Data** ## Footnote **Minimal effort isometric contraction**
* 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
EMG **Qualitative & Quantitative Data** ## Footnote **MOD→MAX isometric muscle contraction**
* Observe **rate of MU recruitment** & **# of MUs recruited** * _Depends_ on **pt participation/motivation\*\*\* (obviously, probably doesn't feel good!!!)**
42
EMG **ABNORMAL _Resting Assessment_ Potential==\>**
FIBS/PSW\*\*\*
43
EMG **ABNORMAL _Resting Assessment_ Potential==\> FIBS/PSW**
* **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
EMG **MINIMAL EFFORT ISOMETRIC MUSCLE CONTRACTION** ## Footnote **_ABNORMAL_ MU AP (Action Potential) Ex.**
* 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
EMG: **MODERATE-MAXIMAL ISOMETRIC CONTRACTION** ## Footnote **_ABNORMAL_ Recruitment & Interference Pattern Ex.**
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
EMG Interpretation Ex.
see pics and NOTE COLORS!!!
47
Scenario 2 EDX Data ## Footnote **EMG + Interpration**
**Scenario 2 EDX Outcomes & Impression**
48
Scenario 2 EDX Outcomes & Impression
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
Clinical Scenario #3 ## Footnote **2 pts similar, but different as well**
BOTH pts present w/ **high clinical suspicion of _ulnar neuropathy_ @ elbow “cubital tunnel syndrome”** ## Footnote **BOTH ask “When am I going to get better?”**
50
Name the **6 Clinical Outcomes of EDX**
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
**Peripheral Nerve** Cell Components
* **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
What **heals faster?** ## Footnote **Myelin regen vs. Axon regen**
**Myelin** regeneration!!!
53
**Comparing Nerve Structure Repair** **REmyelination==\>**
4mm/day ea. segment
54
**Comparison of Nerve Structure Repair** **Axon regeneration==\>**
1mm/day **entire axon** ## Footnote **SLOOOOOOOOW\*\*\***
55
**Prognostic Value** of **EDX** ## Footnote **EDX _can ID_ presence of:** **3:**
1. Demyelination== **Excellent to Good prognosis** 2. Axon Degeneration== **Fair to Poor prognosis** 3. Axon reinnervation of mm fiber== **Recovery underway/Intervention successful**
56
**Prognostic Value** of **EDX** ## Footnote **EDX _can ID_ presence of:** **Demyelination**
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
**Prognostic Value** of **EDX** ## Footnote **EDX _can ID_ presence of:** **Axon Degeneration**
**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
**Prognostic Value** of **EDX** ## Footnote **EDX _can ID_ presence of:** **Axon Reinnervation of muscle fiber**
**Recovery underway/Intervention Successful** * Abnorm **shape, amplitude, & duration of MUs==\> mm fibers _reorganizing_ (GOOD THING!)** * **DECd amp @ all nerve sites**
59
KNOW THIS CHART!!!! ## Footnote **Demyelination == QUICKER recovery vs. Axon loss**
see chart!!!!!
60
Scenario 3A (baseball pitcher) EDX Findings Vs.
Scenario 3B (retired couch potato) EDX Findings
61
Scenario 3 EDX Outcomes, Impression, Management ## Footnote **SEE how they are _different_!!!!**
Note the diff's in severity of injury and treatment plans and prognoses!!!
62
**REVIEW: Clinical Implications of EDX** **6 Outcomes of EDX**
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
**REVIEW: Clinical Implications of EDX** **NCS _optimal for:_**
Optimal for **detecting _DEMYELINATION_\*\*\***
64
OPTIMAL for detecting **demyelination**
NCS
65
**REVIEW: Clinical Implications of EDX** **Optimal for detecting _AXON DAMAGE_ (WORSE prognosis)**
EMG
66
Optimal for detecting AXON damage
EMG
67
NCS optimal for detecting\_\_\_\_\_\_
Demyelination
68
EMG optimal for detecting \_\_\_\_\_\_\_
AXON DAMAGE (worse prognosis)
69
**REVIEW: Clinical Implications of EDX** **EDX Facts:**
* **VERY HIGH Sn & Sp @ detecting _UE compression neuropathies_ encountered by PTs\*\*\*** * Results can alter pt mgmt\*\*\*
70
Summary of EDX Influence ## Footnote **Did it work? and for what?**
see pics + highlights\*\*\*
71
Components of an **EDX Report:**
* 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
EDX Report ## Footnote **Impression of Findings tells you….**
Nerve(s) injured, Location, Axon/Myelin, Motor/Sensory, Chronicity\*, Severity\*
73
Role of PT in EDX
see pics
74
Prolonged F-wave
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

Differential Diagnosis & Med Screening (12 decks)

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