needle emg 2

7/30/2019 Needle EMG 2

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Needle Electromyography Study

Jong Seok Bae

Department of NeurologyInje University College of Medicine

2007


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ContentsContents

1. Recording technique

2. Waveform identification & analysis

- During resting- During activation : minimal/moderate/maximal

3. Interpretation


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Needle electrodesNeedle electrodes


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Needle electrodes (Cont.)Needle electrodes (Cont.)

Fewer1.2 times morePhases

Less sharpSharper & less painfulSharpness

Less, hence noiserElectrical stability

Constant even after

repeated use

Variable after

repeated use

Recording area

MUAP

DecreasedIncreasedSensitivity for

recording spontaneousactivity

Smaller2-3 times largerPickup surface

Concentric needleMonopolar needle

Polyphasic MUPs (%)

turns

DurationArea

Amplitude

1.5 times higher

1.2 times more

1.2 times larger1.5 times larger

1.5-2 times larger

Fewer

Fewer

ShorterSmaller

Smaller


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Needle EMG techniqueNeedle EMG technique

1. Explanation of the

procedure & discomforts2. Preparation for relaxed &

comfortable position3. Needle insertion through

the skin briskly with onequick thrust into themuscle.

4. Verification of the needlelocation

5. Sampling four differentquadrants from insertionsite at various depths.

6. Deeper insertion along the

same axis (corridor)


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Insertional

activityNormal-Normal insertional

activity

Abnormal-Increased

insertional activity

-Decreasedinsertional activity

Voluntary

activityNormal-Normal recruitment-Full interference

Abnormal-Reduced recruitment-Early recruitment

-Moderate / discreteinterference

Spontaneous

activityNormal-End plate noise-End plate potential

Abnormal-Fibrillation-PSW

-CRD-Fasciculation-Myokymia-Myotonia

Simplified step of clinical needle EMGSimplified step of clinical needle EMG


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Insertional & spontaneous

activity: muscle activity at rest


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Information provided by abnormal spontaneous

activities

Information provided by abnormal spontaneous

activities

1. Distribution of abnormal spontaneous activity Localization of disease

2. Type of spontaneous activity

Association of specific disease3. Degree or amount of spontaneous activity

Severity of disease


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Generators of spontaneous activityGenerators of spontaneous activity

Abnormal muscle fiberpotentals

- Fibrillation- Positive sharp wave

- Complex repetitive discharge

- Myotonic discharge

Abnormal motor unit potential

- Fasciculation potentials- Doublets, triplets, &

multiplets

- Myokymic discharges

- Neuromyotonic discharges

- Cramps

- Rest tremor


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Analysis of spontaneous activityAnalysis of spontaneous activity


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Insertional activityInsertional activity

Increased vs decreased insertional activity


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Spontaneous activity: end plate noiseSpontaneous activity: end plate noise

Irregular (hissing)Firing pattern

20-40 HzFiring rate

-Stability

Sea shell, hissing soundSound on loudspeaker

Miniature endplate potential(monophasic negative)

Source generator /morphology


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Spontaneous activity: end plate spikeSpontaneous activity: end plate spike

Irregular (sputtering)Firing pattern

5-500 HzFiring rate

StableStability

Sputtering like fat in a fryingpan

Sound on loudspeaker

Muscle fiber initiated byterminal axonal twig(brief spike, diphasic, usuallyinitial negative)



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Spontaneous activity: normalSpontaneous activity: normal

End plate noise vs endplate spike


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Fibrillation potentialsFibrillation potentials

RegularFiring pattern

Denervation hypersensitivityMechanism

0.5-10 Hz

(occasionally up to 30Hz)

Firing rate

StableStability

Rain on a tin roof or tick-tock

of a clock

Sound on loud

speaker

Muscle fiber (brief spike,diphasic, initial positive)



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Fibrillation potentials (Cont.)Fibrillation potentials (Cont.)


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Positive sharp wavesPositive sharp waves

Denervation hypersensitivityMechanism

RegularFiring pattern

0.5-10 Hz

(occasionally up to 30Hz)

Firing rate

StableStability

Dull pops, rain on a tin roof, or

tick-tock of a clock

Sound on loud

speaker

Muscle fiber (diphasic, initialpositive, slow negative)



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Positive sharp waves (Cont.)Positive sharp waves (Cont.)


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Grading of abnormal spontaneous potentialsGrading of abnormal spontaneous potentials

Full interference pattern of potentials+4

Many potentials in all areas+3

Moderate number of potentials in three or more areas+2

Persistent single trains of potentials (>2-3 seconds) in

at least two areas

+1

None present0


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Pitfalls in fibrillation & PSWPitfalls in fibrillation & PSW

Absence of fibrillation or PSW even in denervation process- Insufficient time (< 2~4 weeks)

- Primary demyelinating neuropathy without secondary axonaldegeneration- Too low temperature or poor circulation of muscle- Severe atrophy or degeneration of muscle- Reinnervation already in progress

Presence of fibrillation or PSW in a substantial number ofasymptomatic subjects- Intrinsic foot muscles: 6%~29% of normal subjects- Lumbar paraspinal muscles: 15% of normal subjects

(30% in elder than 40 years old)

Fibrillation & PSW in these muscles are not necessarilyindicative of denervation process


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Myotonic dischargesMyotonic discharges

Waxing/waningFiring patternSpontaneous (constant)depolarization of muscle

membrane

Mechanism

20-150 HzFiring rate

Waxing/waning amplitudeStability

Reviving engine, dive bomberSound on loud

speaker

Muscle fiber (brief spike,

initial positive, or positivewave)

Source generator /

morphology


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Myotonic discharges (Cont.)Myotonic discharges (Cont.)


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Myotonic discharges (Cont.)Myotonic discharges (Cont.)


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Complex repetitive discharge (CRD)Complex repetitive discharge (CRD)

Perfectly regular (unlessoverdriven)Firing pattern

Ephatic activation of adjacentmuscle fibers

Mechanism

5-100 HzFiring rate

Usually stable; may change indiscrete jumpsStability

Machine motor boat, motorcycle

Sound on loudspeaker

Multiple muscle fibers time

linked together

Source generator /

morphology


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Complex repetitive discharge (CRD) (Cont.)Complex repetitive discharge (CRD) (Cont.)


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Complex repetitive discharge (CRD) (Cont.)Complex repetitive discharge (CRD) (Cont.)


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Fasciculation potentialsFasciculation potentials

IrregularFiring pattern

Ephatic firing of MUPsMechanism

Low (0.1-10 Hz)Firing rate

StableStability

Corn poppingSound on loud

speaker

Motor unit (motor neuron/axon)



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Benign vs malignant fasciculationBenign vs malignant fasciculation

Distinguishing benign from malignantfasciculations on a clinical basis is nearlyimpossible

Benign are not associated with muscle weakness,

wasting, or any abnormalities of reflexes. Benign tend to fire faster and to affect the

same site repetitively


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Doublets, triplets, & multipletsDoublets, triplets, & multiplets

Bursts of twos, threes, or afew potentials

Firing pattern

Hyperexcitable motor neuronMechanism

Variable (1-50 Hz)Firing rate

Usually stable; may change innumber of potentials

Stability

Horse trottingSound on loudspeaker

Motor unit (motor neuron/axon)Source generator /morphology


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Doublets, triplets, & multiplets (Cont.)Doublets, triplets, & multiplets (Cont.)


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Myokymic dischargesMyokymic discharges

Ephatic firing of MUPMechanism

Bursting of the sameindividual motor unit potential

Firing pattern

1-5 Hz (interburst)

5-60 Hz (intraburst)

Firing rate

Usually stable; number ofpotentials may change withinthe burst

Stability

Marching soldiersSound on loudspeaker

Motor unit (motor neuron/

axon)

Source generator /

morphology


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Disorders commonly associated with myokymicDisorders commonly associated with myokymic


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Disorders commonly associated with myokymic

discharges

Disorders commonly associated with myokymic

discharges

Radiation injury (usually brachial plexopathy)

Guillain-Barre syndrome (facial)

Multiple sclerosis (facial)

Pontine tumors (facial)

Hypocalcemia

Timber rattlesnake envenomization

And occasionally seen in

- Gullian-Barre syndrome (limbs)

- Chronic inflammatory demyelinating polyneuropathy

- Nerve entrapments

- Radiculopathy


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Neuromyotonic dischargesNeuromyotonic discharges

WaningFiring pattern

Very high (150-250 Hz)Firing rate

Decrementing amplitudeStability

PingingSound on loud

speaker

Motor unit (motor neuron/axon)


N i di h (C )


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Neuromyotonic discharges (Cont.)Neuromyotonic discharges (Cont.)

Disorders commonly associated withDisorders commonly associated with


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Disorders commonly associated with

neuromyotnia

Disorders commonly associated with

neuromyotnia

Isaacss syndorme

Familial continuous muscle fiber activity syndrome

And occasionally seen in

- SMA

- Peripheral neuropathy

- Tetany

- Artificially induced ischemia or electrical stimulation /tapping of nerve

Spectrum of abnormal spontaneous activitySpectrum of abnormal spontaneous activity


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Spectrum of abnormal spontaneous activity

generated in motor nerve/neuron

Spectrum of abnormal spontaneous activity

generated in motor nerve/neuron


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Voluntary activity: muscle

activity at contraction

M t it (MU) t f MUPM t it (MU) g t f MUP


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Motor unit (MU) as a generator of MUPMotor unit (MU) as a generator of MUP

The basic element of the PNS

Defined as an individual motor neuron, its axon, &associated NMJ & muscles fibers.

MU size = number and diameters of MFs in the MU

The number and size of MUs vary among differentmuscles

M ths of MUPMyths of MUP


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Myths of MUPMyths of MUP

MUP dose NOTrepresent the electrical activity of thewhole MU

MU size may NOTbe proportionate to the relative size ofthe MUP

Measured parameters of MUPs are affected by the type ofneedle electrodes

Myths of MUP (Cont )Myths of MUP (Cont )


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Myths of MUP (Cont.)Myths of MUP (Cont.)

Needle electroderecording surface

Anteriorhorn cell Peripheral

nervemuscle

MUP analysisMUP analysis


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MUP analysisMUP analysis

1. Minimal contraction: wave form analysis of

MUP

2. Moderate contraction: Firing pattern analysisof MUP

3. Maximal contraction: Interference pattern ofMUP

Limitation of routine EMG & need forLimitation of routine EMG & need for


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quantitative methodquantitative method

Subjective analysis

Inter examiner variance Paucity of objective

criteria for abnormality

Equivocal results inminimally affected case

Difficulty in assessmentof progression

Objective analysis

Minimize observer bias Precise interpretation of

the findings

Comparison of resultsacross time, individuals,laboratories andmethodologies

Statistical analysis

Recognition of genuine near field MUPRecognition of genuine near-field MUP


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Recognition of genuine near-field MUPRecognition of genuine near-field MUP

Genuine near-field MUPs can be recognized by their sharp,crisp sound and short rise time (usually < 500 sec)

Manual methodManual method


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amplitude

duration

3 phases

Typical MUP measurementTypical MUP measurement


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: Waveform analysis: Waveform analysis

AmplitudeAmplitudef l i


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150 V~3 mV (CN) vs 500 V~5mV(MN)

Peak to peak measurement Amplitude only reflects not thenumber of MFs in MU but those fewfibers nearest to the needle

It increases as- The needle moves closer to theMU

- The number of MFs in a MUincreases

- The diameter of MFs increase- The better synchronized the

firing

DurationDurationW f l i


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Typical MUP duration is between 5-

15 msec The time from the initial deflectionfrom baseline to the time the MUPreturns to baseline

The number of MFs within a MU Also significantly affected by

distant muscle fibers

The most important MUP parameter

in differentiation betweenmyopathy and denervation process

DurationW f l i

DurationW f l i


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Potentials from 2-15 muscle fibers summate to give duration(within a 2.5mm from the needle)

Rise time & major spikeW f l i

Rise time & major spike: Waveform analysis


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Major spike : the largest positive-to-negative component of MUP

Rise time : the time from themaximum negative peak to themaximum positive peak thatprecedes it

It reflects the distance betweenthe recording tip of electrode anddepolarized muscle fiber

It is essential for the recognitionof genuine near-field MUP

It occurs when the major spike risetime is < 0.5 msec, indicatingproper needle placement.

PhasesW f l i

Phases: Waveform analysis


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Polyphasia

- Normally, 3 or rarely 4 phases

- Can easily be calculated by adding 1 to the number ofbaseline crossings of the MUP

- Measure of synchrony

- Nonspecific measure

- Increased polyphasia in up to 5-10% of potentials isconsidered normal





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Serrations (turns)- >50 V, Do not subsequently cross the baseline.

- Increased polyphasia and serrations have similarmeanings

Satellite potentials (linked potentials, parasite potentials)- Seen in early reinnervation- By collateral spouts from adjacent intact MUs- Time locked potentials- Becomes an additional phase or serration


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MU structural remodeling: Waveform analysis

MU structural remodeling: Waveform analysis


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Normal

Neuropathy

Myopathy

High-amplitude long-duration(HALD) MUPs: Waveform analysis

High-amplitude long-duration(HALD) MUPs: Waveform analysis


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Amyotrophic lateral sclerosis, spinal muscular atrophy,chronic myelopathy involving anterior horn cells,radiculopathy, chronic peripheral neuropathy, chronic

mononeuropathy, IBM

Diseases(common)

Chronic denervationDiseases(essential)

Chronic denervationSignificance

Large MU territory; type groupingGenerator

HALD MUPs with reduced recruitmentKey findingsNo special sound characteristicSound

>15HzFrequency

>5mV with monopolar and >3mV with concentric needleAmplitude

>17ms; >20ms in polyphasic MUPsDurationAny deflectionInitial deflection

HALD monophasic or diphasic MUAs, often with HALDpolyphasic MUPs

Shape

Small-amplitude short-duration(SASD) MUPs: Waveform analysis

Small-amplitude short-duration(SASD) MUPs: Waveform analysis


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: Waveform analysisy

Myotonic dystrophy, MG, LEMS, botulism, periodicparalysis

Diseases(common)

MyopathyDiseases(essential)

Myopathy and neuromuscular transmission disordersSignificance

Either histological or physiological functional loss ofrandom of muscle fibers

Generator

SASD MUPs with early recruitmentKey findings

Sharp rasping scratchy sound from newspaper rubbingbetween two fingers or needle on a cracked old 78gramophone slow-play record

Sound

Early recruitmentFrequency

50-300uV with monopolar and 25-200uV with concentricneedle

Amplitude0.5-4ms; up to 6ms in small-polyphasic MUPsDuration

Any deflectionInitial deflection

SASD monophasic or diphasic MUPs, often with manySASD polyphasic MUPs

Shape

Diseases with mixed SASD MUPs and HALD MUAPs: Waveform analysis

Diseases with mixed SASD MUPs and HALD MUAPs: Waveform analysis


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yy

Inclusion body myopathy (IBM)Myopathy

1. Rapidly progressing motor neuron diseases2. Spinal muscular atrophy

3. HMSN type II

Anterior horn cellsdiseases

Diseases in which this potential is commonly observed:

Bimodal distribution of MUP in myopathy: Waveform analysis

Bimodal distribution of MUP in myopathy: Waveform analysis


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yy

Stability: Waveform analysis

Stability: Waveform analysis


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y

1. Rapidly progressing axonal degeneration2. Reinnervation following nerve injury

Diseases in which thispotential is commonly

observed:

1. Myasthenia gravis

2. LEMS3. Botulism

Neuromuscular

transmission disorders:

Diseases with MUPs with varying amplitude

Activation / recruitmentActivation / recruitment


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Activation

- Ability to fire MUs faster- Central process

Recruitment- Ability to add MUs as firing rate

Both decreased activation and recruitment may bepresent in the same patient

Physiologic aspect of muscle force generationPhysiologic aspect of muscle force generation


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Frequency modulation

- MU firing

Recruitment

- Additive activation of

the other MUs

Size principle

- Type1 MU type2 MU

- Low threshold, small size

Measurement: Firing pattern analysis



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Manual method from 500msec epoch

Iterdischarge interval (IDI)

Firing rate (Hz) = 1000/IDI

Recruitment ratio

Rate of fastest MUP / No. of MUPs

Cf. Onset frequency, Recruitment frequency




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Firing rate

= 1000/IDI

= 1000/154

= 6.5Hz

IDI = 154 msec


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Recruitment ratio Rule of five: Firing pattern analysis



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10 Hz < 10 Hz

> 10 Hz




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Recruitment ratio

= 14/3 = 4.7

Recruitment ratio

= 16/2 = 8

MU Remodeling with recruitment: Firing pattern analysis

MU Remodeling with recruitment: Firing pattern analysis


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Normal

10 days

3-4 weeks

2-4 months

After 6 months

Reduced recruitment: Firing pattern analysis

Reduced recruitment: Firing pattern analysis


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Early recruitment: Firing pattern analysis

Early recruitment: Firing pattern analysis


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Subjective assessment at maximal effort: Interference pattern analysis

Subjective assessment at maximal effort: Interference pattern analysis


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Reduced recruitment & discrete interference: Interference pattern analysis

Reduced recruitment & discrete interference: Interference pattern analysis


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Early recruitment & full interference: Interference pattern analysis

Early recruitment & full interference: Interference pattern analysis


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Characteristic needle EMG pattern: Interpretation

Characteristic needle EMG pattern: Interpretation


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Inactivemyopathic

Activemyopathic

Chronic

(inactive)neuropathic

Active

(subacute orongoing)neuropathic

No

Profuse

No or little

Profuse

Fibrillation &PSW

SASD MUPwith lesspolyphasic MUP

SASD MUP;markedlypolyphasic

HALD MUP

with relativelyunremarkablepolyphasic MUP

Markedly

polyphasic,normalamplitude &duration

MUP

Normal orexcessive

Normal orexcessive

Greatly

reduced; rapidfiring

Moderately or

highly reduced

Interference

Minimalmyopathy

Profusemyopathy

Reinnervation,

type grouping

Axonal

degeneration

Pathology

Benigncongenitalmyopathy

PM, alcoholicmyopathy, IBM

SMA,

Kugelberg-Welander dz.CIDP, CMT1

Nerve injury,

ALS, Werdnig-Hoffman dz.Axonalneuropathy,plexopathy

Typicaldiseases

Take home messageTake home message


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No single parameter identifies a target muscle as

myopathic, neuropathic, or associated with anNMJ disorder

cf. Myotonia, duration of MUP

Rather, specific patterns of abnormalities inmorphology and firing pattern of spontaneous orvoluntary activity reflect the specific disorder

needle emg 2

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