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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
