2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 1 Development of Complex Curricula for Molecular Bionics and Infobionics Programs within a consortial* framework** Consortium leader PETER PAZMANY CATHOLIC UNIVERSITY Consortium members SEMMELWEIS UNIVERSITY, DIALOG CAMPUS PUBLISHER The Project has been realised with the support of the European Union and has beenco-financedbytheEuropean SocialFund*** **Molekuláris bionika és Infobionika Szakok tananyagának komplex fejlesztése konzorciumi keretben ***A projekt az Európai Unió támogatásával, az Európai Szociális Alap társfinanszírozásával valósul meg. PETER PAZMANY CATHOLIC UNIVERSITY SEMMELWEIS UNIVERSITY sote_logo.jpg dk_fejlec.gif INFOBLOKK 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 2 Peter PazmanyCatholicUniversity Facultyof InformationTechnology ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEM ELECTROMYOGRAPHY(EMG) www.itk.ppke.hu (Az ideg-és izom-rendszer elektrofiziológiaivizsgálómódszerei) RICHÁRD FIÁTHand GYÖRGY KARMOS Lecture11 (Elektromiográfia) ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 3 AIMS: In this lecture the student will become familiar with the methods of electromyography, the biological basics of the neuromuscular system, the technical basics of the EMG recording system and some examples of neuromuscular disorders that can be diagnosed with electromyography. Content: Definition, subdivision and importance of electromyography Biological basics• The structure of the skeletal muscle • The motor unit • The neuromuscular junction • Neuromuscular disorders Technical basics • Electrodes • Amplifiers • Recording techniques www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 4 DEFINITION: Electromyography(EMG) is the recording and analysis of the bioelectric activity of skeletal muscles. Clinical EMG is the electrodiagnostic method used for the examination of human peripheral nerves and muscles. It also includes nerve conduction studies (NCS) and reflex studies. Other used names for EMG: electrodiagnostic examination (EDX), electroneuromyographic examination (EMNG) www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 5 IMPORTANCE OF EMG Electromyographyisaneasymethod,thatcanbecarriedoutrelativelyfast,theresultsarereproducible,recordableandmorethanonemuscleandnervecanbeanalyzedatonce. SUBDIVISIONSOFEMG 1. Conventional (clinical) electromyography 2. Macroelectromyography 3. Scanning electromyography 4. Single fiber electromyography 5. Electrical stimulation and EMG– Nerve conduction study – Studies with two or three stimuli – Repetitive stimulation www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 6 SHORT HISTORY OF EMG Liddell and Sherrington (end of 1920s): Defined the motor unit. Adrian and Bronk (1929): Developed the concentric needle electrode and recorded first the sound of the electromyogram. Denny-Brown (1929): Recorded and described first the motor unit potential. Buchthal and Clemmens (1941): First electromyographic differentiation of neurogen and myogen muscle atrophies. They suggested the quantitative analysis of motor unit potentials. Golseth and Fizzell (1948): Developed the first EMG device for clinical use. Ekstedt and Stalberg (1960s): Developed the single fiber EMG method. Stalberg(1980s): Developed the macro EMG method. Stalbergand Antoni (1980s): Developed the scanning EMG method. www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 7 BIOLOGICAL BASICS www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 8 THE STRUCTURE OF THE SKELETAL MUSCLE Theskeletalorstriatedmusclesareresponsibleforthelocomotionofthebody.Therearemorethan600musclesinthehumanbody.Wellknownmusclesareforexamplethebicepsbrachiionthearm,thedeltoidonthebackorthequadricepsfemorisontheleg.Thegluteusmaximusorbuttockisthelargestandthestapediuslocatedinthemiddleearisthesmallestmuscleinourbody. Musclesareanchoredtothebonesbytendons.Theoutersheathofthemusclesiscalledepimysiumandcontainsthefascicles.Afascicleisabundleofmusclefibersboundedtogetherbytheconnectivetissueperisymium.Musclefibersaresurroundedbyendomysium:theyarethemusclecellswithlostofnuclei.Thesemusclecellscontainmyofibrilswhichcanbefurtherdividedintosarcomeres.Thesesarcomeresarecomposedoftheproteinsactinandmyosin,whicharemyofilamentsresponsibleforthecontractionofthemuscles.(Figure1.) ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 9 Figure1. Anatomyof the skeletalmuscle muscle.png ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 10 THE STRUCTURE OF THE SKELETAL MUSCLE Therearetwotypesofmusclefibers:typeI(slow-twitch)redandtypeII(fast-twitch)whitefibers.TypeIfiberscontainmoremyoglobine,theircontractionisslowercomparedtotypeIIfibers,butthecontractionholdsforlongerperiods.TypeIImusclefibersfatigueveryrapidlybuttheyaremorepowerfulthantypeIfibers.TypeIImusclefiberscanbesubdividedintotwosubgroups:typeIIaandtypeIIb.(Figure2.) Therearetwotypesofproprioceptivesensoryreceptorsintheskeletalmuscle:musclespindlesandGolgitendonorgans.Musclespindlesarelocatedinthebellyofthemuscleanddetectchangesinthelengthofthemuscle.Theyplayanimportantroleinthestretchreflex.Golgitendonorganscanbefoundinthetendonsnearatthebeginningofthemusclesandareanimportantpartofthetendonreflex.(Figure3.) ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu THE STRUCTURE OF THE SKELETAL MUSCLE 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 11 muscle_fibers_1.png Figure 2. Cross section of a muscle fascicle. The different muscle fiber types (I, IIaand IIb) are arranged in a mosaic pattern. Figure 3. Sensory receptors in the muscle: the muscle spindle and the Golgi tendon organ. muscle_spindle.png ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 12 PHISIOLOGY OF THE SKELETAL MUSCLE Musclefibersbehavesimilartoneurons:theyhaveasemipermeablemembraneandhaveanelectricpotentialdifferencebetweentheextracellularandintracellularregionsofthecell.Thisiscalledtherestingmembranepotentialandhasavalueofabout(-60–-80)mVdependingonthemuscle.Ifastimuluscomes(anactionpotentialreachestheaxonterminalofamotorneuronandacetylcholineisexocytosedattheneuromuscularjunction),thecelldepolarizesandthesocalledend-platepotentialemerges.Iftheend-platepotentialreachesathresholdvalue,thananactionpotentialisgeneratedwhichadvancesinbothdirectionsonthemusclecellmembraneandgetsintothetransversaltubularsystem.Calciumionswillbereleased,andaftercomplexbiochemicalmechanismsthemusclecontractionoccurs. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 13 THE MOTOR UNIT (MU) The motor unit is the smallest functional unit of the neuromuscular system that can be voluntarily activated. Parts of the motor unit are (Figure 4.): 1. the motor neuron in the ventral horn of the spinal cord 2. the axon of the motor neuron in the peripheral nerve 3. the muscle fibers innervated by the axonterminals of the motor neuron Muscle fibers that belong to the same motor unit are placed in a mosaic pattern, around them are fibers that are innervated by other motor units. (Figure 5.) Electrophysiological, biochemical and histological properties of muscle fibers innervated by the same motor unit are very similar. www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 14 www.itk.ppke.hu motor_unit.png Figure4. The Motor Unit ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 15 www.itk.ppke.hu Figure5.Musclefibersinnervatedbythreemotorneurons.(Thepartswiththesamecolorrepresentanindividualmotorunit)Musclefibersthatbelongtothesamemotorunitshowamosaicpatternandareintermingledamongfibersinnervatedbyothermotorunits. motor_unit_2.png ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 16 PROPERTIES OF THE MOTOR UNITS ThenumberofmusclefibersinnervatedbytheaxonofoneMUiscalledthe„innervationratio”.Therearedifferencesbetweenmotorunitsinthenumberofinnervatedmusclesfibers:musclesproducingfinemovements(likethemusclesofthedigits)havemotorunitsthatsendaxonterminalsjusttoafewmusclefibers(10-500fibersperMU).Ontheotherhandthemotorunitsofbiggermusclesproducinggrossmovementslikethequadricepsfemorisinnervateagreaternumberofmusclefibers(600-2000fibersperMU).Thediameterofmusclefibersinnervatedbyanordinarymotorunitisabout2-8mm. Therearedifferenttypeofmotorunits:theycanbeclassifiedbasedonseveralfactorslikephysiological,biochemicalandimmunohystochemical. Somaticmotorneuronswhichinnervatetheskeletalmusclescanbealphamotorneuronswithheavilymyelinated,fast-conductingaxons,thathavealargediameterandinnervatesthemusclefibersorgammamotorneuronswhichhavethinneraxonsandterminatesonmusclespindles. www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 17 RECRUITMENT OF MOTOR UNITS Thesizeofthemotorunitsvariesalsowithinthesamemuscle.Smallermotorunitshaveaxonswithsmallerdiameter,innervatelessandsmallermusclefibersthenbiggerones.Thesesmallmotorunitsactivateatfirstwhensomemovementiscarriedout,thebiggermotorunitsareactivatedduringgreatervoluntaryeffort.ThisphenomenoniscalledtheHenneman’ssizeprinciple. Themusclefibersthatbelongtothesamemotorunitarecontractingmoreorlessatthesametime.Aslightasynchronicitycanbeobservedduetothedifferentlengthoftheaxoncollateralsofthemotorneuron(becausethemusclefibersarenotatequaldistances),sotheactionpotentialreachesthemusclefibers(andtherecordingsurfacetoo)indifferenttimedelays(Figure18.). www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 18 THE NEUROMUSCULAR JUNCTION The neuromuscular junction is the place where the action potential of the neuron is transposed to the muscle fiber. When the action potential reaches the presynaptic motor nerve-ending (axon terminal of a motor neuron), vesicles of acetylcholine are released into the neuromuscular cleft. These activate receptors on the muscle membrane surface, which produce miniature end-plate potentials. When the temporal summation of a burst of end-plate potentials reaches a threshold, than a muscle fiber action potential is generated which advances in both directions on the membrane and gets into the transversal tubular system, calcium ions will be released, and after complex biochemical mechanisms muscle contraction occurs. (Figure 6.) ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 19 Figure6. The neuromuscularjuntion neuromuscatmenet.jpg ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 20 NEUROMUSCULAR DISORDERS There are four main groups of neuromuscular disorders: • Myopathies–These are the diseases of the muscle (Muscle dystrophies, Polymyositis, Myotonia congenita) • Neuropathies–These are diseases of motor neurons of the nervous system (Amyotrophic lateralsclerosis, Poliomyelitis) • Diseases of the nerve fibers –Caused by the lesion (structural damage) of the motor, sensory or mixed nerves, axonal damage or demyelinisation. • Disorders of the neuromuscular junction–Caused by the dysfunction of some structures located here (Myasthenia gravis, Eaton-Lambert syndrome,Botulism) www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 21 MYOPATHIES Myopathyisamusculardisease,wherethemusclefibersaredamagedordonotfunctionwellforsomereason.Itresultsinmuscleweakness.Commonsymptomscanbe:musclestiffness,crampsandspasm.Myopathiescanbeacquiredorinherited. Muscledystrophiesareagroupofinheritedmyopathies,wherethemusclecellsandtissuediesandthemusclesofthebodyareweakened.Mainsymptomsarepoorbalance,difficultyinwalking,respiratorydifficultyorlossofbladdercontrol.Thereisnoknowncureformuscledystrophies. Polymyositisisatypeofinflammatorymyopathy.Majorsymptomsarepain,muscleweakness,lossofmusclemassintheproximalmusculature. Myotoniacongenitaisageneticmyopathythataffectsskeletalmusclesandiscausedbyageneticmutationinvolvingthechloridechannelofmuscles.Delayedrelaxationofthemuscles,rigidity,hypertrophy,crampingandpainarethemajorsymptomsofthedisorder. www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 22 NEUROPATHIES Amyotrophiclateralsclerosis(ALS)isaneurodegenerativedisordercausedbythedegenerationofmotorneurons.Symptomsaremuscleweakness,atrophy,twitching,cramping,lossofspeechanddifficultyofswallowing.Thischronicdiseasecannotbecured.TheendstageofALSiscalled„lockedinsyndrome”.StephenHawkingisthebest-knownpersonlivingwithALS. Poliomyelitisorinfantileparalysis,isaviralinfectiousdiseasecausedbythepoliovirus.Thevirusentersthecentralnervoussystem,destroysthemotorneuronscausingfirstmuscleweaknessthenparalysis.Poliomyelitisisanacutediseaseandthereisnoknowncure,onlypreventionbyvaccination. www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 23 DISORDERS OF THE NEUROMUSCULAR JUNCTION Myastheniagravisisanautoimmunedisordercausedbyantibodiesthatblocktheacetylcholinereceptorsatthepostsynapticsiteoftheneuromuscularjunction.Symptomsaremuscleweaknessandfatigue.Musclesontheheadaremainlyaffected.Thetreatmentiswithmedicationbygivingthepatientcholinesteraseinhibitorsorimmunosuppresantsorbysurgicalremovalofthethymus.(Figure7.) Eaton-Lambertsyndromeisalsoanautoimmunediseasecausedbytheinhibitionofthevoltage-gatedcalciumchannelsonthepresynapticsiteoftheneuromuscularjunction.Thispreventsthereleaseofacetylcholinefromthepresynapticterminal,sonomusclecontractioncanevolve.Muscleweaknesscanbeobserved:theproximalpartsofthearmsandlegsaremainlyaffected.(Figure7.) www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 24 disease.png Figure 7. Myasthenia gravis -Antibodies block the acetylcholine receptors therefore acetylcholine can not bind to the receptors to generate muscle contraction(left side of the figure) Eaton-Lambert syndrome –The voltage-gated calcium channels are inhibited and thelack of calcium influx prevents the acetylcholine released from the vesicles(right side of the figure) ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 25 TECHNICAL BASICS OF EMG • Electrodes¦ Needle electrodes ¦ Surface electrodes ¦ Stimulating electrodes • Amplifiers • Recording techniques www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 26 NEEDLE ELECTRODES Theconcentricneedleelectrodeconsistsofastainlesssteelcannula,inwhichaninsulatedplatinum-iridiumwireisfixedbyepoxy.Theendoftheplatinumwireformstherecordingsurface(calleddifferentoractiveelectrode)andthecannulaservesasthereference.Aconcentricneedleelectrodewhichhasahemisphereradiusofabout0.5mm,canpick-upsignalsfromabout20musclefibers.UsedinclinicalEMG.(Figure8.A,Figure9.) Thebipolarelectrodesareconstructedfromastainlesssteelcannula,withtwoplatinumwiresisolatedfromeachother.Bipolarelectrodeshaveasmallerrecordingsurfacethanconcentricelectrodesthereforeithasagreaterselectivity.UsedinclinicalEMG.(Figure8.B,Figure10.) Monopolarelectrodesarestainlesssteelneedles,coatedwithTeflonexceptforthetipof1-3mm.Twomonopolarelectrodeshastobeconnectedtothedifferentialamplifieratonce.Canbeusedforstimulationorformeasuringthesensoryconductionvelocity.(Figure8.C) www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 27 NEEDLE ELECTRODES Multielectrodeshavesmallplatinumcontacts(usuallymorethan10)onthesideofthestainlesssteelcannula,whicharetheendingsoftheisolatedplatinumwiresinsidethecannula.Canbeusedforthemeasuringtheexpansionofthemotorunit.(Figure8.D) Singlefiberelectrodesconsistalsoofastainlesssteelcannula,withaplatinumwireinsideitwithamaximumof25micrometerindiameterandembeddedinepoxyresin.Thewireendsatthesideofthecannula,andisexposedabout3mmfromthetip.Canbeusedformeasuringthejitterandelectricalfiberdensityinsinglefiberelectromyography.Thesteelcannulaactsasthereferenceelectrode.Therecordingsurface(platinumcontact)picksupactivityfromwithinahemisphericalvolume300micrometerindiameter.Recordsonlyfrom1-3singlemusclefibersinnervatedbythesamemotorunit.(Figure8.E) www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 28 NEEDLE ELECTRODES Macroelectrodesaremodifiedsinglefiberelectrodes.Thestainlesssteelcannula(about0.5mmindiameter)isuninsulated15mmfromthetip.The25micrometerplatinumwireisexposedinasideport7.5mmproximaltothetip.Thecannulahastwofunctions:first,itservesastheindifferentelectrodewhenwerecordsinglefiberpotentialsandontheotherhanditworksasanactiveelectrode,whenrecordingthemusclefiberpotentialsneartheelectrode.Inthiscasetheindifferentelectrodeofthecannulaisaconventionalconcentricelectrode.Thesetypeofelectrodesareusedinmacroelectromyography.(Figure8.F) www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 29 www.itk.ppke.hu electrodes.png Figure 8. The tip of needle electrodes in two different views ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY bipolar_2.jpg monopolar_2.jpg 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 30 NEEDLE ELECTRODES www.itk.ppke.hu bipolar_1.jpg monopolar_1.jpg Figure 9. Concentric needle electrode Figure 10. Bipolar needle electrode ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 31 SURFACE ELECTRODES Surfaceelectrodesaremadefromsilver/silverchlorideortin/tinleadalloy.Thesetypeofelectrodesare1-6mmindiameter.Theyareusedwhenwewanttorecordmotorunitsthatdischargesynchronously.TheyareuselesswhenwewanttoestimatetheshapeanddurationofsingleMUpotentialsoranalyzingmusclesindeeperregions.Inaddition,thehighfrequencysignalsarelostduetothehighresistanceofthetissuebetweentheskinandtheelectrode.(Figure11.) Thepreparationofsurfaceelectrodeshasthefollowingway:firsttheskinofthesubjecthastobewipedwithalcoholtocleanthearea.Afterthataconductivegelorelectrolytepasteisusedtofurtherdecreasetheresistanceoftheskin.Atlasttheelectrodecanbefixedwithabandagetothemuscletopreventunnecessarymovementsduringmuscularefforts. Surfaceelectrodesareusedinpsychophysiologyorsportandergonomicstudies. www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 32 SURFACE ELECTRODES www.itk.ppke.hu IMG_0010.JPG IMG_0009.JPG Figure 11. Surface electrode ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 33 STIMULATING ELECTRODES Stimulatingelectrodescanbemonopolarneedleelectrodes,surfaceelectrodesorringelectrodes.Incaseofbipolarsurfaceelectrodeswithfixedinterelectrodedistancethedistancebetweentheanodeandcathodeisconstantwitharecommendeddistanceof23mm.Byplateelectrodestheanodeandcathodecanbeplacedinarbitrarydistancesfromeachother.Ringelectrodesareusedonthefingers.Theyareeasytoequip,butthedistancebetweentheanodeandcathodeisimportant.(Figure12.) GROUND ELECTRODES Duetosafetyissuesandtoreducestimulusartifactsthepatientsmustbegrounded.Thegroundelectrodehastobelargeandshouldhaveagoodcontactwiththeskin.Ifstimulationisused,thegroundingelectrodeshouldbeplacedbetweenthestimulationandrecordingelectrodes. www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 34 STIMULATING ELECTRODES www.itk.ppke.hu IMG_0005.JPG Figure 12. Stimulating electrode ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 35 ELECTRODE POTENTIAL Electrodesaretheweakestlinkwhenrecordingelectricalsignals,theyarethecauseofmostofthenoise.Electrodesaremadefrommetal,andwhenametalcontactsanelectrolyte(electricallyconductiveliquid),apotentialwillbedevelopingonthecontactsurface,calledtheelectrodepotential.Inthecaseofsurfaceelectrodestheelectrolyteistheelectrolytepasteorphysiologicalsalineandinthecaseofneedleelectrodesitistheliquoroftheconnectivetissue.Thevalueoftheelectrodepotentialdependsonthetypeofmetalthatbuildsuptheelectrode:itisintherangefromacouplemillivoltstoseveralhundredmillivolts.(foramoredetaileddescriptiononelectrodpotentialandotherpropertiesofelectrodesseeLecture5.) www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 36 AMPLIFIERS Adifferentialamplifierisusedinpracticeinelectromyography.Thishastwoinputs(e.g.twoneedleelectrodes:activeandindifferent),andamplifiesthepotentialdifferencebetweenthistwoinputs.Signalswithidenticalphaseatbothelectrodeswillnotbeamplified,becausethedifferenceofthistypeofsignalsiszero(commonmoderejectionratio).Thismeans,thatnoisesourcesthatarerecordedonbothofthetwoinputs(likethe50or60Hzfrequencyofpowerlines)areeliminated.Soitisveryimportant,thatbothoftheinputshavethesameresistance.Thereforetheresistanceofthetwoelectrodesmustbealsothesame.Incaseofbipolarelectrodesthisisnotaproblem,butwhenconcentricelectrodesareused,thesurfaceoftheactiveandindifferentelectrodesdiffer,sotheresistancevaluesarealsodifferentcausingagreaterprobabilityofperturbationpotentials.(Figure13.) www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 37 www.itk.ppke.hu dif_amp.png Figure 13. Differential amplifier in case of a bipolar arrangement. Noise sources recorded on both of the inputs are eliminated, only the potential difference between the two inputs remains. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 38 AMPLIFIERS Theinputresistanceoftheamplifierhastobesignificantlylarger,thantheresistanceoftheelectrode.Amplitudedistortionscanbeavoidedthisway.Inputresistanceisabove100M.inmodernsystems. Therecordedsignalsarebuiltupfromdifferentfrequencycomponents.Withfiltersanappropriatefrequencybandcanbechosentofilterouttheunnecessaryfrequencycomponents.Therearelow-pass,high-pass,band-passandband-stopfilters.Usuallyaband-passfilterfrombetween20Hzto10kHzisusedintheamplifiersusedinEMG. Aftertheamplificationtheanalogsignalisdigitized(sampledandquantized)withanA/Dconverterandstoredontheharddriveofacomputerforsubsequentanalysis. www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 39 RECORDING TECHNIQUES–ARTIFACTS IncaseofEMGartifactsareundesiredalterationintherecordedsignalsthatoriginatefromothersourcesthanthemusclesbeingstudied.Artifactscanbephysiologic,mechanicallyinducedorelectrical. Physiologicartifactsareforexamplewhentheheartpotentialisrecorded(ECG)orwhentheelectrodeisplacedoverapulsatingvessel.Theseappearintherecordingslikerhythmicsharpwaves.Sweatingcanproducehugeslowbaselinesways.(Figure14.) Mechanicallyinducedartifactscanoccurduringcableorelectrodemovement.Theseappearassingleormultiplesharpwaveformsbecauseoftheimpedancechanges.(Figure15.) Electricalartifactscancomefromelectromagneticnoisesourceslikethe50or60Hzpowerlinesorcellphones.(Figure16.) www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 40 www.itk.ppke.hu Figure 14. ECG artifact on an EMG recording. The artifact can be filtered out with a high-pass filter. ECG.png ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 41 www.itk.ppke.hu cable_movement.png Figure 15. Cable movement artifacts. An appropriate high-pass filter can help us remove the this type of signal alteration. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 42 www.itk.ppke.hu 50hz.png Figure 16. Electrical artifact originating from the 50 Hz power lines. The noisy signal is represented in two different time scales. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 43 RECORDING TECHNIQUES -ELECTRODE PLACEMENT Forinvasiverecordingstheneedleelectrodeisplaceddirectlyinthemusclebellyofthemuscleofinterest.Forsurfaceelectrodesthelocationsarenotsoobvious.Apreferredlocationisintheregionhalfwaybetweenthecenteroftheinnervationzoneandthefurthertendon.Electrodesshouldlieparalleltomusclefibersandtheinterelectrodedistanceshouldbebetween2to10mm.Incaseofbipolarrecordingsthecontactsshouldhavesimilarorthesamesizesandimpedances.Foroptimalrecordingsthebestanatomicalpositionsforsurfaceelectrodeshavebeeninvestigated. ForsurfaceEMGtheskinofthesubjecthastobecleanedwithanalcoholsoakedgauzetolowertheskinresistance.Ifnecessarytheskinshouldbealsoabradedlightlyorshaved.Conductivegelisusedbetweentheelectrodeandtheskintofurtherimprovethequalityoftherecordings.Theelectrodesarefixedtotheskinwitharubberpadandanelasticstrap.(Figure17.) ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 44 electrode placement.png Figure 17. ElectrodeplacementforsurfaceEMG recordings fromthegastrocnemiusmuscle ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 45 EMG METHODS • Conventional (clinical) electromyography • Macroelectromyography • Scanning electromyography • Single fiber electromyography www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 46 CONVENTIONAL (CLINICAL) ELECTROMYOGRAPHY Conventional electromyographic examination is done in three steps: 1. Recording and analysis of resting muscle activity 2. Recording and analysis of different properties of the motor unit potential during gentle contraction (minimal voluntary effort) 3. Analysis of the activity patterns during maximal voluntary contraction (increasing effort) ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 47 CONVENTIONAL(CLINICAL) EMG ConventionalorclinicalEMGisdonewiththeuseofsurfaceorneedleelectrodes,usuallywithconcentricneedleelectrodesormonopolarelectrodes.Theelectrodeisinsertedinacompletelyrelaxedmuscle,theinsertionactivityisrecordedandanalyzedwhetheritisnormal,decreasedorincreased.Afterthat,welookoutfortherestingactivity.Everymusclechosenforanalysishastobeexaminedindifferentneedlepositions,thatmeansthatthepositionanddepthoftheneedlemustbechangedseveraltimes. Afterthat,thepatienthastocontractthestudiedmuscleslightly.Duringtheslightcontractionthepropertiesofthemotorunitpotentials(MUP)canbeanalyzed.Theruleisthatconclusionscanbedrawnonlyfromtheaverageofatleast20differentMUPdata.Becauseofthesizeprinciple,onlythesmallermotorunitscanbeanalyzedthatway. AftertheMUPanalysis,thepatienthastodoamaximalcontraction,andtheemerginginterferencepatternisanalyzed. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 48 RESTING ACTIVITY Inhealthyindividualsusuallythereiselectricalsilenceinrelaxedmuscles,soelectricsignalsobservedduringoraftertheinsertionoftheelectrodeinrelaxedmusclescanmeanpathologicprocesses.Restingactivityhastwotypes:insertionalactivityandspontaneousactivity. Insertionalactivitycanbedividedintoharmactivityandendplateactivity: Harmactivityisduetothemechanicalinjuryofthemusclefiberswhentheneedleelectrodeisinsertedormoved.Itisahighfrequency(100-500Hz),lowamplitude(10-30microvolt)spiketrainlastingforseveralseconds. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 49 RESTING ACTIVITY Endplateactivity:theneedleelectrodeirritatestheintramuscularnerveendingbecausetheelectrodeisneartotheendplateoftherelaxedmuscle.Endplatenoise(low-amplitude,irregulardisturbancesofthebaseline,miniatureendplatepotentialactivitycausedbytherandomreleaseofvesiclesofacetylcholineattheneuromuscularjunction)andendplatepotentialcanbedistinguished. Spontaneousactivityhasmanyformslike: Fibrillationpotentials,Positivesharpwaves,Fasciculations,Myokymicdischarges,Myotonicdischarges,Complexrepetitivedischarges. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 50 MOTOR UNIT POTENTIAL (MUP) TheMUPisthesummationofactionpotentialsgeneratedbythedischargesofmusclefibersthatareinnervatedbyonemotorunit.Itcanbeanalyzedinminimalcontractionofthemuscle.Theneedleelectrodecanonlyrecordafractionoftheactionpotentialsgeneratedbymusclefibers.Itisthesummationpotentialof15-20musclefibersina0.5-1mmradius. Theactionpotentialofsinglemusclefibersisshortintime(2-3ms)andhasalowamplitude.Musclefibersinnervatedbythesamemotorunitarespreadinalldirections,andhavedifferentlengths.Thistwofactsmeansthatactionpotentialsfromindividualmusclefibersarrivesindifferenttimemomentstotherecordingsurface(temporaldispersion),becausethesignalhastorundifferentdistances.Thesummationoftheseactionpotentialsgeneratesthe10mslength,200-800microvoltMUP.(Figure18.)AnalysisoftheMUPisveryimportantindiagnostics,becauseimportantconclusionscanbedrawnfromthechangesofsomeofthepropertiesofthiswaveform. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 51 MUP.png Figure 18. Origin of the motor unit potential ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 52 Figure 19. Examples of motor unit potentials in surface EMG recordings. A –Recording from the biceps B –Recording from the hypothenar muscles (Recordings band-pass filtered with an analog filter from 20 Hz to 2000 Hz) MUP_example.png ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 53 Figure 20. Motor unit potentials displayed on different timescales MUP_expand.png ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 54 PROPERTIES OF THE MOTOR UNIT POTENTIAL Shape–Thenormalmotorunitpotentialistriphasic,thebeginningispositive,followedbyanegativepeakandendswithaslightpositivedeflection.TheshapeoftheMUPchangesafterchangingthepositionoftheneedle.Theshapeisinfluencedbyfactorslikethedistancebetweentheelectrodeandthemusclefibers,thespatialpositionofthedischargingfibers,thetemperatureofthemuscleorthetypeoftheelectrode.NodiagnosticconclusioncanbedrawnfromtheshapeoftheMUP. Duration–Itistheelapsedtimefromleavingbaselineandreturningtoitagain.Thevaluesarevaryingdependingonthemuscle,butinnormalmuscleitisbetween5-15ms.Themorebiggeristhemotorunitandthemoreactivemusclefibersareneartherecordingsurface,thelongeristheduration.Thedurationispathologicalwhenitdiffersfromthenormalvalueby20%.Influencingfactorsare:age,temperatureofthemuscle,tiredness.(Figure21.) ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 55 PROPERTIES OF THE MOTOR UNIT POTENTIAL Amplitude–Ismeasuredfrompeaktopeakorfromthenegativepeaktothebaseline.Themagnitudedependsonthenumberofmusclefibersneartherecordingsurface,andtheirspatialposition.Theactionpotentialofthe3-4nearestmusclefiberdeterminesthesizeoftheamplitude,soitcanvaryinthesamemuscleindifferentneedlepositions.Thevaluesarenotthesameindifferentmuscles,itisusually200-800microvoltsmeasuredfrompeaktopeak.Influencingfactors:age,typeoftheelectrode.(Figure21.) Risetime–Timeelapsedbetweenthefirstpositivepeakandthefollowingnegativepeak.Risetimeindicatesthedistancebetweentheactivemusclefibersandtherecordingsurfaceare.(Figure21.) Area-IntegratingtheareaundertheMUP.Theareaisdecreasinginmyopathycausedbymusclefiberdestruction. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 56 PROPERTIES OF THE MOTOR UNIT POTENTIAL Numberofphases–ThepartoftheMUPthatisplacedbetweenthecrossingoftwotimesthebaseline.Ifthepotentialcrossesthebaselineatleast4times,thanwecallitpoliphasicpotential.Itiscausedbythedesynchronicityofthemusclefiberactionpotentials.(Figure21.) Numberofturns-Changeofthepolarity,withoutcrossingthebaseline.Ifmorethan4polaritychangecanbenoticedonthepotential,thanitiscalledcomplex(orpoliphasic)potential.Itisalsocausedbythedesynchronicityofthemuscledischarges(temporaldispersion).Theconductionvelocityofaxonterminalsandmusclefiberssignificantlydiffers.(Figure21.) Stability-IfweassumethatthefactorsinfluencingtheshapeoftheMUPareconstant,thaninthenormalcasethedischargesofindividualmotorunitscomingaftereachothergenerateMUPsofthesameshapeandamplitude.ButduetosomeneuromusculardisorderstheMUPshapeand/oramplitudecanvary.Thisshape-changeiscalledjiggle. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 57 MUP_prop.png Figure 21. Propertiesof themotor unit potential ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 58 Figure 21. The change of the properties of motor unit potentials in pathological conditions emg_disease.png ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 59 ACTIVITY PATTERNS DURING MAXIMAL CONTRACTION Thestrengthofthemusclecontractiondependsonthenumberoftheactivemotorunitsandthedischargefrequencyofthese.Givenmorestrength(withincreasingeffort)moremotorunitswillbeactivated.Smallermotorunitsactivatefirst,thanthebiggeronesaccordingtothesizeprinciple.Thisactivationprocessiscalledrecruitment.Parallelwiththerecruitmentalsothedischargefrequencyofindividualmotorunitsalsoincreases(from6-10Hzto20Hz),thesynchronizationwillbeimproved. Innormalcasethesocalledinterferencepatterncanbeseen:thesinglemotorunitpotentialscannotbeseparatedfromeachother,theyareinterfering,sothebaselinecannotberecognized.Sotheinterferencepatternistheelectricalactivityrecordedduringincreasingvoluntaryeffort.(Figure22.,Figure23.,Figure24.,Figure25.) ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 60 interference_pattern.png Figure 22. The developmentof theinterferencepattern ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 61 Figure 23. Interferencepatternrecordedfromthebiceps ip_example1.png ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 62 Figure 24.Evolvedinterferencepatternduringincreasingeffortby alternatingthecontractionand relaxation. ip_example2.png ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 63 Figure 25. Interferencepatterns representedondifferenttime scales ip_example3.png ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 64 ACTIVITY PATTERNS DURING MAXIMAL CONTRACTION DuringfatiguetheamplitudeoftheMUPandalsothedischargefrequencyofthemotorunitsdecreases. Whenpartsofthebaselineremainvisibleandsomeindividualmotorunitscanstillbeidentifiedduringmaximumvoluntaryeffortthanwetalkabouta„reducedinterferencepattern”. Inperipheralneurogenlesionthereducedactivitypatterncanbeseen.Thenumberofmotorunitsisdecreased,sothereisreducedrecruitment.Toensurethenecessarystrength,thesurvivingmotorunitsdischargewithhigherfrequencies.Theindividualmotorunitpotentialscanbeseparatedandthebaselinecanberecognizedinsomepartsoftherecording. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 65 ANALYZING THE EMG DATA StepsofautomaticMUPanalysisgainedfromconcentricneedleelectrodes: • CollectingMUPswithaspecifiedamplitudethreshold •SortingtheseMUPsbasedontheirshapeandamplitude,clusteringandcomparingtheclusters • Searchingforaspecifiednumberofrepetitions • AveragingofpropertiesandstatisticalanalysisoftheidentifiedMUPs TheautomaticdecompositionanalysisisusedforsplittingtheinterferencepatternintoindividualMUPs,measuringandaveragingtheirpropertieswithastatisticalanalysisattheend. Theturn/amplitudeanalysisisalsoafastandpopularmethodforanalyzingtheinterferencepattern.Itmeasuresthenumberofturnsandtheaverageamplitudedifferencebetweentheturnsduring1secondintervalsinthecaseofacontractionwithagivenstrength. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 66 Figure 26. Another analysing method is the calculation of the frequency spectrum of the interference pattern. ip_spectrum.png ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 67 Figure 27. Filtering and rectifying the interference pattern can be the basis of many automatic processing algorithms. A few filtered and rectified sample EMG traces are represented on the figure. ip_analysis.png ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 68 Figure 28. Relationshipbetweenthecontractionforceand theEMG activity emg_force.png ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 69 FIELDS OF NONINVASIVE EMG APPLICATIONS • Surface Mechanomyogram • Neurology • Ergonomics • Exercise physiology • Movement and gait analysis • Rehabilitation medicine • Biofeedback • Control of prostheses ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 70 MACROELECTROMYOGRAPHY ItisaspecialEMGmethodsuitableforrecordingtheelectricalactivityoftheentiremotorunit.Itsclinicalimportanceisinthejudgmentofreinnervation.ThetechnicaldevelopmentwasdonebyStalberg. SinglefiberEMGandconventionalEMGcanrecordtheelectricactivityonlyfromafractionofmusclefibersinnervatedbythemotorunits.Thegoalofmacromyographywastoadevelopamethod,thatmakesitpossibletoselectmostofthemusclefibersinnervatedbyoneanalyzedmotorunitwithfilteringouttheactivityofadjacentmotorunits,sotherecordedpotentialwouldbegeneratedmostlyfromonemotorunit.Thegoalcanbeachievedwithamodifiedsinglefiberelectrodethathastworecordingsurfaces. Theelectrodemakesatwo-channelrecordingpossible.Withoneofthechannelswecanrecordthesignaloftheselectivesinglefiberelectrodeandwiththeotherchanneltheactivityofthenon-selectivemacrosurface. www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 71 MACROELECTROMYOGRAPHY Themacroelectrodeisdescribedinthetechnicalbasicssection(Figure8.F). Thebigrecordingsurfaceofthemacroelectrodereachesacrossthewholecross-sectionofthemotorunit,andmakespossibletherecordingofmanymusclefiberpotentials.Thelargeuninsulatedpartofthecannularesultsinashunteffectandbecauseofthis,thedistancefromtheneedlehassmallerinfluenceontheamplitudeoftherecordedmusclefiberpotential.Alargerecordingsurfaceandtheshunteffectmakesitpossible,withthehelpofaspecialaveragingtechnique,thatonlythepotentialsofasinglemotorunitwillberecorded.Thesinglefiberpotentialrecordedonthefirstchannelisthetrigger:itcontrolstheaveraging.Onthesecondchannelwecanseeanaverageactivity,whichiscorrelatedintimewiththefirstchannel,soitcomesfromthesamemotorunit.Thepotentialscomingfromtheothermotorunitsareasynchronouswiththetrigger,sotheyvanish. www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 72 MACROELECTROMYOGRAPHY Themacropotentialrepresentsthespatialandtemporalsummationoftheactionpotentialsoftheindividualmusclefibers.Theamplitudeandareaofthemacropotentialcangrowmanifoldaftercollateralreinnervation. Thecourseofmacromyographygoesthefollowingway: Themacroelectrodeisinsertedintothebellyofthemuscleperpendiculartothedirectionofthemusclefibers.Theconcentricelectrodethatactsasareferenceisinsertedsubcutaneouslyfarfromtheexaminedmuscle.Thepatientisaskedforagentlecontractionwithconstantforce.Afterthisthemacroelectrodeismovedintothemuscleuntilastablesinglefiberpotentialappears.Thananappropriatetriggerlevelischosenandtheaveragingisstarted.Theamplitudeandtheareaofthepotentialismeasured.Theendresultoftheanalysisisfromthemedianvalueofthemacropotentialdataof20differentmotorunits.Thefiberdensityisalsocalculatedineveryneedleposition. www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 73 SCANNING ELECTROMYOGRAPHY Amethodforstudyingtheelectrophysiologicalcross-sectionofthemotorunit,itwasdevelopedbyStalbergandAntoni.Scanningelectromyographycanshowthedistributionofpathologicalmalfunctionsacrosstheentirecross-sectionofthemotorunit.ThescanningEMGservesmainlyscientificpurposestostudythemorphologyofmotorunitsandthedistributionofEMGsignalsinsidethemotorunits. With scanning myographicrecordings we can tell: • The length of the cross-section of the motor unit • The fractions of the motor unit (significant electrical activity) • The number and length of the „silent” areas (minimal electrical activity) • Number and length of poliphasic and complex parts • Maximal duration and amplitude www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 74 SCANNING ELECTROMYOGRAPHY Inahealthymusclethecross-sectionofmotorunitsisbetween2and10mm.Throughoutthecross-section1-4motorunitfractionscanbeobserved,thenumberof„silent”areasislessthenone.Incaseofneuropathiesthemaximaldurationandamplitudeincreasestogetherwiththenumberoffractionsandpoliphasicsections.Myopathiesarecharacterisedwithanincreaseofthesilentareas,becauseofthedestructionofmusclefibers. Theexaminationbeginswiththeinsertionofaconcentricneedleelectrode(scanningelectrode)intotheexaminedmuscleandafterwardsitispulledoutin50micrometerstepswithacomputercontrolledmotorwhichisconnectedtoatriggerelectrode.Thetriggerelectrodeisasinglefiberelectrodeplaced20mmfromthescanningelectrode.Bothelectrodeshavetorecordsynchronousactivity,meaningtheyareinthesamemotorunit.Theelectricalactivityisrecordedateverystepuntilthescanningelectrodeispulledofthecross-sectionofthemotorunit.Thesizeoftheactivitydependsonthesizeoftherecordingsurfaceandthepositionofthemusclefibersaroundit. www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 75 SINGLE FIBER ELECTROMYOGRAPHY (SFEMG) TheSFEMGisaselectiveelectrophysiologicalmethodforrecordingtheactionpotentialsofsinglemusclefibers.ThemethodwasdevelopedbyEkstedt,StalbergandTrontelj.Physiologicalandmorphologicaldatacanbecollectedthiswayfromthemusclefibers,themotorendplateandtheaxonterminals.Inpractice,theSFEMGisusedforthemeasureofjitterandcalculationofelectricfiberdensity.Thejittertellsusaboutthefunctioningoftheneuromusculartransmission,thefiberdensityaboutthemuscletopographyinsidethemotorunit.TheSFEMGmakesalsopossiblethemeasurementoftheconductionvelocityofthemusclefiberactionpotentials,studyingthedischargepatternsortheusingofspecialaveragingtechniques(like„spiketriggering”usedinmacroEMGandscanningEMGmethods). TheselectivityofSFEMGisachievedwithaspecialneedleelectrode.Thesinglefiberelectrodeisdescribedinthetechnicalbasicssection(Figure8.E).Therecordedpotentialisbiphasic,hasanamplitudeof1-7mVandadurationof1ms. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 76 www.itk.ppke.hu SINGLE FIBER ELECTROMYOGRAPHY-JITTER Duringrepetitivestimulationoftheintramuscularaxonitcanbeobservedthatthelatencyofthemusclefiberactionpotentialrecordedwithasinglefiberneedleelectrodevariesfromdischargetodischarge.Duringminimalvoluntaryeffortwhentheneedleelectrodeisplacedbetweentwomusclefibersbelongingtothesamemotorunit,twopotentialsarerecorded.Duringrepetitivedischargingthedistancebetweenthetwoactionpotentialsalsochanges.Thetimebetweenthetwoactionpotentialsiscalledinterpotentialinterval(IPI).TheIPIresultsfromthedifferentdistancesthattheelectricimpulsehastoachievefromtheaxonalbifurcationtothemusclefiber.AvariabilityoftheIPIiscalledjitter.Thisvariabilitycomesfromthechangeoftheneuromusculartransmissiontime,thechangeoftheconductiontimeoftheaxonterminalandthemusclefiber. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 77 www.itk.ppke.hu SINGLE FIBER ELECTROMYOGRAPHY–JITTER Thejitterisincreasingindiseaseswiththedisordersoftheneuromusculartransmissionandinreinnervationprocesses.Myopathiescanaffectjitterinbothdirections:anincreasecanbeobservedindegeneratingorregeneratingmusclefibersandadecreaseiscausedbysplitmusclefibers. There are two ways for measuring the jitter: • Voluntary jitter study –Recording from two muscle fibers that belong to the same motor unit, with a voluntary contracted muscle. • Stimulation jitter study –Recording from one muscle fiber with repetitive stimulation of that muscle. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 78 www.itk.ppke.hu SINGLE FIBER ELECTROMYOGRAPHY–MEASURING THE FIBER DENSITY Theaverageofthenumberofpotentialsrecordedin20differentneedlepositionsgivestheelectricfiberdensityofagivenmuscle.Inaslightcontractionwithahealthymuscleone,twoorthreemusclefiberactionpotentialscanberecordedinoneneedleposition,soafiberdensityofahealthymuscleisaround1.5.Withageingandalsoinneuropathiesthisnumberisincreasing.Inmyopathiesthefiberdensitycanbehigherorlowercomperedtothenormalvalue. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 79 ELECTRIC STIMULATION AND EMG • Singlepulse studies -Nerve conduction measurement • Studies with two or three stimuli • Repetitive stimulation www.itk.ppke.hu ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 80 SINGLEPULSE STUDIES EMG studies that use single stimuli, cover the following areas: 1. Measuring the nerve conduction velocity of motor nerves: Stimulatingthe nerve, recording from the muscle and analyzingthe compoundmuscle action potential (CMAP)ormotor response (M-wave) 2.Measuring the nerve conduction velocity of sensory nerves: Stimulatingand recording from a nerve and analyzing the evoked sensory nerve action potential (SNAP) 3.Measuring the nerve conduction velocity of mixed nerves: Stimulatingand recording from a mixed nerve and analyzing the evoked mixed nerve action potential (MNAP) 4.Analysis of late waves 5.Motor unit number estimation (MUNE) ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 81 NERVE CONDUCTION STUDIES–STIMULATION PROPERTIES Percutaneous(surface)stimulationisusedwitharectangularwave(0.1–1msduration).Thebipolarstimulatingelectrodes(Figure12.)areplacedoverthenervetrunk.Boththeanodeandthecathodeareoverthenervebundle.Indeep-seatednervesormusclessurfacestimulationisnotpossible:inthiscasethestimulationiscarriedoutwithneedleelectrodes.Inmotorconductionstudiestherecordingelectrodeisplacedoverthebellyofthemuscle,whichcorrelateswiththeendplatezone.Recommendedfiltersettingsformotorconductionstudiesrangefrom10Hzto10kHzandforsensoryconductionstudiesfrom20Hzto2kHz. Supramaximalstimulationmeansthatthecurrentorvoltageintensityisslowlyincreaseduntiltherecordedpotentialisatitsmaximum.Thisintensityisusedinsupramaximalstimulations,whileinsubmaximalstimulationalowercurrentorvoltageintensityismaintained. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 82 MOTOR NERVE CONDUCTION STUDIES OneofthemostusedmethodsinclinicalEMG.Amotorormixednerveisstimulatedwithelectriccurrentattwoormoreplacesandthegeneratedresponsepotential(M-wave)isrecordedatthemostdistalmuscleinnervatedbythenerve.Thesemusclearecalledreferencemusclesoftherespectivenerve.Thenerveconductionvelocitycanbecalculatedbydividingthedistancebetweenthestimulationandrecordingelectrodewiththetimeelapsedfromthestimulationtotheresponsepotential.Howeverthesituationisnotsosimple. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 83 MOTOR NERVE CONDUCTION STUDIES Forelectricalstimulationthereisalwaysasupramaximalstimulusused,tostimulatealloftheaxonsinthenervefiber.Thiswaythebeginningoftheresponsebelongstothelatencyofthefastestconductingfibers.Thelatencyisthetimeelapsedfromthestimulustotheappearanceofthenegativedeflectionoftheresponsepotential. The latency consists of: 1. The „pure” conduction time 2. The terminalconduction time, where the axons are unmyelinated and the conduction speedis slower 3. The timeneeded for neurotransmission (slow process, 1ms) 4. The conductiontime of the muscle membrane (slow process, 6 m/s) ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 84 MOTOR NERVE CONDUCTION STUDIES Tomeasurethepureconductiontimethatisneededforcalculatingtheconductionvelocitywehavetoremovethefactors2.,3.and4.Thiscanbemanagedbystimulatingthenerveattwopointsandmeasuringthelatencyinbothcases.Becausethefactors2.,3.and4.havethesamevaluesincaseofbothofthestimulations,ifwesubtractthetwolatencies,wegetthetimeneededfortravelthedistancebetweenthetostimulationpoints.Afterthatwemeasurethedistancebetweenthetwostimulationpointsanddividethisvaluewiththeconductiontimetogetthe„pure”conductionvelocity.(Figure29.,Figure30.) Thedecreaseoftheconductionvelocitycanbeasignofnervelesion.AdecreaseoftheamplitudeoftheM-wavecanrefertothedamageofaxons. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 85 Figure 29. Measuringthemotor nerveconductionvelocity NCS.png ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 86 Figure 30. An example calculationof themotor nerve conduction speed (green –stimulation at the elbow, red –stimulation at the wrist ) NCS_example.png ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 87 MOTOR NERVE CONDUCTION STUDIES Factors influencing the conduction velocity and the parameters of the responsepotential: 1. Temperature: cooling down decreases the conduction velocity. 2. Age: in infants the conduction velocity is 50% slower than in adults and after 20 years the conduction velocity begins slowly decreasing. 3. Conduction speed of the lower extremities is 7-10 m/s slower compared to upper extremities. 4. Incorrect measurement of the distance between the stimulation points can cause huge errors in the end results. 5. With submaximal stimulation we can measure a longer latency, because slower conducting fibers can activate first in this case. 6. Other adjacent nerves can be stimulated accidentally due to wrong electrode placement or to a strong stimulus. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 88 SENSORY NERVE CONDUCTION STUDIES Two methodscan be used: 1. Orthodrom method: follows the physiological path of the conduction of the stimulus. The nerve is stimulated distally and the recording is done proximally. 2. Antidrom method: the nerve is stimulated proximally and the answer potential is recorded distally. This method is simpler and more advantageous forseveralreasons. Thelatencyofthesensorynervesareequaltothepureconductiontime,socalculatingtheconductionvelocityismuchsimplercomparedtothecalculationofthemotornerveconductionspeed,itneedsstimulationonlyatoneplace.Theconductionspeedofsensorynervesis4-10%fastercomparedtomotornerves. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 89 SENSORY NERVE CONDUCTION STUDIES Theconclusionsarethesameasbythemotornerves:decreaseintheconductionvelocityisasignofdemyelinisationandthedecreaseintheamplitudeoftheanswerpotentialistheresultofaxonaldamage. Theinfluencingfactorsarealsothesameasmentionedbythemotornerves. Incaseofmixednervessubmaximalstimulationisused,becausethethresholdofsensorynervesislowercomparedtomotornervesandsupramaximalstimulationwouldactivatethemotorfibersandthebiggeramplitudeoftheM-waveswouldhidetheresponsepotentialsofsensorynerves. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 90 LATE WAVES AfterstimulatingamotororamixednervebycertaincircumstancesnewresponsepotentialsemergeaftertheM-wave.Thesearecalledlateresponsesorlatewaves.Herearesomeexamples: F-wave–Bystimulatingthemotorormixednervesthestimulusreachesalsothemotorneuronsintheanteriorhornofthespinalcordbyantidromicpropagation.Theactionpotentialsofthesemotorneuronspropagatebacktothemusclesorthodromicallyandcausesadelayedcontraction.(Figure31.A) H-wave–Itisamonosynapticreflexresponseoriginatingfromthespinalcord,whichcanbeevokedbyelectricalstimulation.(Figure31.B) ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 91 F_H_wave.png Figure 31. A –The generation mechanism of the F-wave B –The generation mechanism of the H-wave ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 92 LATE WAVES A-wave–AppearsalwaysbetweentheM-andF-waveanddevelopsonlyifthesubmaximalstimulusstimulatesonlyoneaxonofanaxonpair.Thestimulusreachesthecollateralbranchantidromicallyandelicitsamuscularcontractionbyorthodromicpropagationontheotheraxon.(Figure32.A)Incaseofsupramaximalstimulationbothaxonsarestimulatedatthesametimeandthetwoantidromicallypropagatingsignalssuppresseachother.(Figure32.B) AnotherlatewaveistheBlink-reflex:agentlehitontheforeheadcausesthecontractionoftheorbicularisoculimuscle.Thereflexhastwocomponents:theearlyR1andthelateR2. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 93 Figure 32. A -The generation mechanism of the A-wave in case of submaximal stimulus B –The reason why the A-wave is absent when supramaximal stimulus is used A_wave.png ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 94 MOTOR UNIT NUMBER ESTIMATION (MUNE) Withtheincreaseofthestrengthofthestimuli,theamplitudeofthesummationpotentialalsoincreases.Everyincreaseintheamplitudecanindicatetheactivationofanewmotorunit.Thisisthegroundprincipleforcountingthenumberofmotorunitsofagivenmuscle.Theexaminationiscarriedoutwithsurfaceelectrodes.Thecathodeisplacedoverthemusclebellyandtheanodeoverthetendonofthemuscle.Thenerveinnervatingthemuscleisstimulatedwithasubthresholdstimulusincreasingtheintensitystepbystepuntilaresponseisobserved.Thismotorunitpotentialisrecordedandthestrengthofthestimulusisincrementeduntilahigheramplitudewaveappearsandthisnewsignalisrecordedtoo.Wefollowthisstrategyuntilnomoreamplitudeincreaseofthepotentialisobserved.Attheend,theamplitudeofthecompoundmuscleactionpotential(CMAP)isdividedbytheaveragedifferencebetweentheamplitudechangesmeasuredearlierandwegetanestimatetothenumberoffunctioningmotorunits. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 95 STUDIES WITH TWO OR THREE STIMULI Two major methods can be mentioned: • Measuringthe refractory periods of sensory nerves with two stimuli • Collisionstudies There aretwotypesof refractory period: • Absolute refractory period -the period immediately following a conditioning stimulus when the nerve cannot be stimulated no matter how great teststimulus is applied (duration 0.5-1 ms) • Relative refractory period -A period of a few milliseconds following the absolute refractory period during which the excitation threshold is raised and a much stronger test stimulus is required to initiate aresponse. (duration 3-5 ms) ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 96 STUDIES WITH TWO OR THREE STIMULI Measuringtherefractoryperiodofthesensorynervesisperformedwithapplyingtwosupramaximalstimulitothenerveandrecordingtheresponsepotentials.Thefirstistheconditioningstimulus,thesecondistheteststimulus.First,theamplitudeandlatencyofthepotentialthatemergedafterapplyingtheconditioningstimuliismeasured.Afterthis,withusingdoublestimulitheinterstimulusinterval(ISI)isincreasedstep-by-stepstartingfromzero.Theappearanceofalowamplitudetestpotentialwithanelongatedlatencyindicatestheendoftheabsoluterefractoryperiod.TheISIthatbelongstothisstimulationsetupisequaltothedurationoftheabsoluterefractoryperiod.FurtherincreasingtheISIuntiltheamplitudeandlatencyofthetestpotentialisthesameasthatoftheconditioningpotential,wegetthedurationoftherelativerefractoryperiod. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 97 STUDIES WITH TWO OR THREE STIMULI DuringthecollisionstudiesthenervesarestimulatedontwolocationsapplyingtwoorthreestimuliandchangingtheISIbetweenthestimulations.Thiswaytheproximallygeneratedandorthodromicallypropagatingactionpotentialcollideswiththedistallyevokedandantidromicallypropagatingpotentialandcanceleachotherout. With the collision method several examinations can be performed: • Measuring the refractory period of motor and mixed nerves • Eliminating the errors of motor conduction velocity measurment • Measuring the conduction velocity of the slowest conduncting motor fibers • Measuring the central latency of the F-wave ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 98 STUDIES WITH REPETITIVE STIMULATION Duringrepetitivestimulationasupramaximalstimulustrainwithdefinedfrequencyisappliedonthemotorandmixednervesandtheevokedmotorresponsesareanalyzed.Thismethodisimportantinthediagnosticsofdisordersrelatedtotheneuromuscularjunction.Therepetitivestimulationisusedwithsinglefibremyography. Intheexaminationsstimulustrainswith2-3Hzfrequencyconsistingof8-10stimuliareused.Thisisrepeatedseveraltimesandtheresponsesareanalysed,forexampletheamplitudeandtheareaofthefirstandthefifthresponseiscomparedtomeasurethedecrementum.Aftermaximalcontractionofthemuscleeithervoluntarywayorwith20-50Hzstimulation,therepetitivestimulationisrepeatedagainandtheresponsesarecomperedwiththedatacollectedbeforethecontractiontocheckforpostactivationfacilitation.Postactivationexhaustioncanbeexaminedwithrepeatedstimulationeveryminuteforfiveminutes. ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 99 RECOMMENDEDLITERATURE • Electromyography in Clinical Practice: A Case Study Approach; Bashar Katirji, 2007, Mosby • Electromyography: Physiology, Engineering, and Non-Invasive Applications; Roberto Merletti, Philip Parker, 2004, IEEE Press • Essentials of Electromoyograhy; Gary Kamen, David Gabriel, 2010, Human Kinetics • Easy EMG; Lyn Weiss, Julie Silver, Jay Weiss, 2004, Elsevier • More than 300 books related to EMG on http://www.amazon.com 41-cPvvKEeL._BO2,204,203,200_PIsitb-sticker-arrow-click,TopRight,35,-76_AA300_SH20_OU01_.jpg 41JbUqwhUtL._SL500_AA300_.jpg 512Og-TUgSL._BO2,204,203,200_PIsitb-sticker-arrow-click,TopRight,35,-76_AA300_SH20_OU01_.jpg 519c8Z+ooiL._BO2,204,203,200_PIsitb-sticker-arrow-click,TopRight,35,-76_AA300_SH20_OU01_.jpg ELECTROPHYSIOLOGICAL METHODS OF THE STUDY OF THE NERVOUS-AND NUSCULAR SYSTEMELECTROMYOGRAPHY www.itk.ppke.hu 2011.10.07.. TÁMOP –4.1.2-08/2/A/KMR-2009-0006 100 SAMPLE QUESTIONS What parts builds up a motor unit? What are the main properties of the motor unit potential? Whatis thegenerationmechanismof themotor unit potential? What means the size principle? How is the interference pattern generated? What type of electrodes are used in EMG? How is a differential amplifier working? What kind of disorders are examined with EMG? What are the main methods used in EMG? How can we measure the motor nerve conduction speed? What means the jitter and what means the jiggle? What kind of EMG examinations were mentioned related to stimulation?