EMG Painful Limb

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    EMG NerveEMG Nerve

    Studies in PainStudies in Pain

    AmmarAGilani,MD,DABPNAmmarAGilani,MD,DABPNAssociateProfessorandStaffNeurologistAssociateProfessorandStaffNeurologist

    DepartmentofMedicine/NeurologyDepartmentofMedicine/NeurologyMcMasterUniversity/HamiltonHealthSciencesMcMasterUniversity/HamiltonHealthSciences

    Hamilton,ONHamilton,ON

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    PfizerPfizer

    AstraZenecaAstraZeneca

    AllerganAllergan

    PurduePurdue

    TevaNeurosciencesTevaNeurosciences

    Lilly/BoehringerIngelheimLilly/BoehringerIngelheim

    ayerayer

    ValeantValeant

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    BasicDescriptionofthelaboratoryproceduresBasicDescriptionofthelaboratoryprocedures

    NerveconductionstudiesNerveconductionstudies

    E ectromyograp yE ectromyograp y

    ElectrodiagnosticabnormalitiesinpainfulperipheralnerveElectrodiagnosticabnormalitiesinpainfulperipheralnerve

    diseasesdiseases

    Pitfalls/limitationsoftechniquePitfalls/limitationsoftechnique

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    SomatosensoryEvokedSomatosensoryEvoked

    o en a so en a s

    thePostthePostMRIera.MRIera.

    A.SSEP

    stimulation

    to

    the

    left

    A.

    SSEP

    stimulation

    to

    the

    left

    MediannerveMediannerve

    B.SSEPstimulation totheleftB.SSEPstimulation totheleft

    TibialnerveTibialnerve

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    EMG and Nerve ConductionEMG and Nerve ConductionStudiesStudies

    An

    extension

    o

    the

    Physical

    ExaminationAn

    extension

    o

    the

    Physical

    Examination Quantitatesnerveand/ormusclein urQuantitatesnerveand/ormusclein ur

    ProvidesUsefulDataRegardingNerveInjuryProvidesUsefulDataRegardingNerveInjury SiteSite TypeType SeveritySeverity

    ura onura on PrognosisPrognosis

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    Goals of EDX Testing

    Localization Severity

    NerveNMJ Anterior HornMuscle

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    erve on uct on tu es Studies

    of

    the

    waveforms

    generated

    in

    the

    .

    Motornerveconduction

    fromamuscleinnervatedbythatnerve.

    Sensorynerveconduction

    Stimulationamixed

    nerve

    while

    recording

    from

    a

    mixedorcutaneousnerve

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    LATENCY(DL)LATENCY(DL)IntervalbetweentheonsetofastimulusandtheonsetofaIntervalbetweentheonsetofastimulusandtheonsetofaresponseresponse

    ThemaximumvoltagedifferencebetweentwopointsThemaximumvoltagedifferencebetweentwopointsItisproportionaltothenumberandsizeofnervefibersthatareItisproportionaltothenumberandsizeofnervefibersthatare

    depolarized.depolarized.

    electricallyactiveelectricallyactive

    DURATIONDURATIONThetimefromonsettotermination.Thetimefromonsettotermination.

    .

    .MeasuresthedifferencesinconductionofthenervefibersMeasuresthedifferencesinconductionofthenervefibers

    CONDUCTION VELOCITY(CV)CONDUCTION VELOCITY(CV)ThespeedatwhichthenervefibersarecarryingtheelectricalThespeedatwhichthenervefibersarecarryingtheelectrical

    s mu us e ween wos es.s mu us e ween wos es.ComparisonofconductionbetweentwosegmentsofthesameComparisonofconductionbetweentwosegmentsofthesame

    nervecanlocalizealesion.nervecanlocalizealesion.

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    studies

    Sensory:typically

    antidromic

    Commonly

    examinednerves:

    Sural,ulnar,median,

    occas ona yra a

    orsuperficial

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    OnsetandpeakOnsetandpeaklatencieslatencies

    ConductionvelocityConductionvelocity determinedbydeterminedby

    velocityofaveryfewvelocityofaveryfewas ersas ers

    AmplitudeAmplitude determinedb thedeterminedb the

    numberoflargenumberoflargesensoryfiberssensoryfibersactivatedactivated

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    Motor Nerve Conductions

    Vital

    part

    of

    EDX

    as

    this

    importantforidentifyingdemyelination,compression

    Needtodoproximalanddistal

    studies

    to

    evaluate

    for

    conductionvelocit ,

    conductionblock,temporaldispersion

    , ,peroneal,

    tibial

    Lesscommon:radial,femoral,phrenic,spinalaccessory,facial

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    F-waves and H-reflex

    Usefulfor

    identifying

    proximalsegmental

    demyelination

    Canonly

    be

    done

    w enmotoramplitudeis>1mV

    epen en

    onpatientsheight

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    MotorFwavestudies roximalroots:

    Antidromic motor

    to

    the

    anterior

    horn

    of

    the

    spinal

    cord;

    orthodromically tothe

    muscle.

    . AprolongedasymmetricFwavessuggestaproximal

    rootlesion.

    Clinicalapplicationbestforplexopathy. Quiteprolongedindemyelination,AIDP,mild

    rolon ationinaxonalin ur .

    Lesssensitive

    than

    EMG

    for

    radiculopathy

    since

    only

    shortsegmentofnerveisdemyelinatedin.

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    Re lexloo : Orthodromicsensor andmotor Utilized

    to

    assess

    for

    radiculopathy

    of

    S1,

    *C6/7

    S1;Poplitealfossa,recordinMedialGastrocnemeus

    C6/7;Mediannerveatwrist,recordatFlexorCarpiRadialis

    ,

    ,

    ,

    sacralplexus,cord,S1motororsensoryroots. Onceabnormal,maynotnormalize;

    O tenabsent

    in

    polyneuropathy

    or

    >60

    years

    o

    age.

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    Needle Electrom o ra h : Techni uesNeedle Electrom o ra h : Techni ues

    NeedleelectrodeisinsertedintothemuscleNeedleelectrodeisinsertedintothemuscle Needleisdisposable,singleuseNeedleisdisposable,singleuse

    MultiplemusclesareaccessibleforexaminationMultiplemusclesareaccessibleforexamination

    CombinationofmusclestestedCombinationofmusclestested DependentuponclinicalquestionDependentuponclinicalquestion

    LevelofdiscomfortismildLevelofdiscomfortismild

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    NeedleElectromyography:DataNeedleElectromyography:Data

    InsertionalActivityInsertionalActivity

    SpontaneousActivitySpontaneousActivity

    MotorUnitConfi urationMotorUnitConfi uration

    MotorUnitRecruitmentMotorUnitRecruitment

    Inter erencePatternInter erencePattern

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    EMGFin ings

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    InsertionactivityInsertionactivityincreaseswithinafewdaysofmuscleincreaseswithinafewdaysofmuscledenervation,whereasdenervation,whereasabnormalspontaneousactivityabnormalspontaneousactivityta es2ta es24 3 wee sto eve op, epen ngont e stance4 3 wee sto eve op, epen ngont e stance

    betweenthenervelesionandthemusclebetweenthenervelesionandthemuscle

    norma spontaneousact v tyan ncrease nsert onnorma spontaneousact v tyan ncrease nsert on

    activityarenotpathognomonicofdenervation,mayoccuractivityarenotpathognomonicofdenervation,mayoccurincertaindisordersofmuscleortheneuromuscularincertaindisordersofmuscleortheneuromuscular

    junctionjunction

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    : ecru tment

    Whenamuscleisvoluntarilycontractedasinglemotorunitmayfire.

    Asthemuscleisfurthercontractedmoremotorunitsareaddedorrecruited.

    Normall recruitmentofadditionalmotorunitsoccursatrelativelylowlevelsofeffort

    IfthereisalossofMUAPswithanydiseaseprocessthen recruitmentisreduced.

    Lossof

    nerve

    axons

    ConductionblockattheneuromuscularjunctionSufficientlossofmusclefibers

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    The

    electromyographic

    findings

    may

    provide

    a

    guide

    to

    the

    time

    of

    The

    electromyographic

    findings

    may

    provide

    a

    guide

    to

    the

    time

    of

    onsetofthelesionandtoitschronicity,onsetofthelesionandtoitschronicity,

    apa en repor s a awr s rop as eve ope mme a e yapa en repor s a awr s rop as eve ope mme a e yafteranoperativeprocedureandneedleelectromyographyafteranoperativeprocedureandneedleelectromyographyperformedshortlythereafterrevealsabnormalspontaneousperformedshortlythereafterrevealsabnormalspontaneousactivit fibrillation otentialsand ositiveshar waves intheactivit fibrillation otentialsand ositiveshar waves intheextensormuscleofthewrist,itislikelythatthelesionisatleastextensormuscleofthewrist,itislikelythatthelesionisatleast223weeksoldandtherefore itprecededthesurgery.3weeksoldandtherefore itprecededthesurgery.

    ,, ,, ,,polyphasicmotorunitpotentialsindicatesthatthedenervationpolyphasicmotorunitpotentialsindicatesthatthedenervationoccurredseveralweeksormorebeforesurgerybecausesomeoccurredseveralweeksormorebeforesurgerybecausesomereinnervationhasoccurred.reinnervationhasoccurred.

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    MononeuropathyMononeuropathy

    PolyneuropathiesPolyneuropathies

    MultiplexMultiplex

    Radiculo athRadiculo ath

    TrigeminalMononeuropathyTrigeminalMononeuropathy

    (BlinkReflex(BlinkReflex))

    Plexopathy(BrachialPlexopathy(BrachialorLumbosacral)orLumbosacral)

    MyopathyMyopathy

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    AxonalAxonal Sensory+/Sensory+/ MotorMotor NormalCVNormalCV

    DemyelinatingDemye

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