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1 2 SpinalCordStimulation Treatmentshouldbe undertakenaspartofa healthcareteam approach SpinalCordStimulation ItsRoleinManagingChronicDiseaseSymptoms Simon Thomson, MBBS, FRCA, FIPP, FFPMRCA Past President, International Neuromodulation Society, 2015Consultant in Pain Management and Neuromodulation, Basildon and Thurrock University Hospitals NHS FT, U.K. Aroundtheworldsome34,000patientsundergospinalcordstimulatorimplants eachyear.Firstusedtotreatpainin1967,spinalcordstimulation(SCS)delivers mildelectricalstimulationtonervesalongthespinalcolumn,modifyingnerve activitytominimizethesensationofpainreachingthebrain. Sincethetherapyfirstenteredroutineuseinthe1980s,advanceshave continuedthatenablemorecloselytailoringthetherapytoapatient’sindividual needs.Newerleaddesignsprovidemoreprecisecontroloftheelectricalfield andincreasinglysophisticateddevicesofferavarietyofstimulationparameters. Afurtheradvancehasbeentheawarenessthatpainreductioncanbeachieved withoutevokingperceptiblesensations. TheU.S.FoodandDrugAdministration(FDA)firstapprovedSCSin1989to relievechronicpainfromnervedamageinthetrunk,armsorlegs.Thetherapy nowaccountsforabout70%ofallneuromodulationtreatments.Thatnumberis expectedtogrowinordertomanageavarietyofchroniclong-termconditions. SCSisusedtotreatpainthatismostlyneuropathicinorigin,thatis,painthat arisesfromnervedamageanddoesnotserveaprotectivepurpose.Thenerve damagemayhaveoccurredduetoaccident,injury,ordisease.SCStherapyis mostcommonlyindicatedinneuropathicbackandlegpain,typicallyseenin 25%ofpatientsfollowingbacksurgery. IncreasinglySCSisusedtoavoidfutilebacksurgery.Thesecondcommonest indicationistotreatthepainassociatedwithcomplexregionalpainsyndrome. Thethirdisthepainassociatedwithperipheralneuropathicpaincausedby nervedamagebeyondthespineorbrain,forinstance,fromviralinfection, trauma,surgeryordiabetes. November2016 Otherkeyusesareinthepaincausedby ischaemia–acirculatorysystemproblem involvinganinsufficientsupplyof oxygenatedbloodtotissues–suchasin chroniccriticallimbischaemia,refractory anginaandsometreatment-resistant vasculitisdisordersthatresultfroman inflammationofbloodvessels. Apartfromneuropathicandischaemic pain,SCShasbeendemonstratedina numberofcasesofchronicvisceralpain, suchasinselectedpatientswithchronic abdominalorpelvicpain,forinstance,after majorabdominalorpelvicsurgery. SpinalCordStimulation’sBeneficial Function Intheseconditionsthenormalpainsensory andprocessingcircuitsofthespinalcord andbrainarealtered.StimulationwithSCS notonlyreducesabnormalpainsignals reachingthebrainbutalsorestoresthe normalpain-inhibitionpathwaysthatmay havebeenlost.Itdoesthisbyelicitingthe body’snaturalpain-reliefsubstances, chemicalneurotransmittersthatareused bynervestocommunicatewitheachother. www.neuromodulation.com 4 3 SpinalCordStimulation Thisnotonlyresultsinreducedpainbutalso,inthepresenceofischaemia, improvedmicrocirculation. Itisimportanttoappropriatelyselectpatientswhoarelikelytobenefitfrom SCStherapy.SCSdoesnotworkforallpatientswithalltypesofpain. Dependinguponthescientificstudies,50to70%ofpatientssuitableforSCS mayexperience50%reductionintheirreportedpainatfollow-up.Aneven higherproportionwillexperiencea30%painreduction.Long-term neuropathicpainhasamajorimpactuponmeasuresofhealth-relatedquality oflife.SCSinthesecircumstanceshasanimpressiveeffectonimproving qualityoflife. SCShasabettertrackrecordintreatingneuropathicbackandlegpainthan repeatbacksurgeryorcomprehensivepainmanagementalone. NotallhealthcaresystemsmayfundSCSforalltheconditionsmentioned, butthelevelofclinicalandcost-effectivenessevidencesupportsitsusefor neuropathicpainindications,andinsomehealtheconomies,forboth ischaemicandvisceralpainaswell. OptingforSpinalCordStimulation PatientswhoareconsideredforSCShavegenerallyhadchronicpainfor morethanayear.Chronicpainhasaphysicalandemotionalimpact,so generallythesuffererhascomplexneedsthatneedtobeevaluated.Firstthe correctmedicaldiagnosisandpainmechanismisunderstood,andthenthe psychologicalimpactisevaluated. Theideaistonotonlydetermineiftheyaregoodcandidatesbutalsoto supportthemthroughtheprocessofhealthimprovement.Thismight includelearningbetterpaincopingstyles,reducingdependencyonhabit formingmedicationandlearningtograduallyrestorephysicalfunction. Yourdoctormaywellbeassistedbyotherhealthcareprofessionalsworking withinthemultidisciplinaryteam.Theactualspinalcordstimulation procedureitselfmaybedonebypainspecialists,anesthesiologists, neurosurgeons,rehabilitationdoctors,orothertrainedspecialists. ImplantinganSCSdeviceisacomplexbutminimallyinvasiveprocedureand isbestcarriedoutbytrainedandexperiencedspecialists. NeuromodulationwithSCSStartswithaTrialPhase Implantingthestimulatorisatwo-stageprocess.Whilewatchingona monitor,thedoctorwillguideahollowneedleintotheepiduralspaceabove thespinalcanal.Throughthispassageway,oneormorethinleadsare threaded,eachcarryinganumberofsmallelectricalcontactsalongtheend. Theleadsareattachedtoapowersupplythatdeliversamildcurrent.With feedbackfromthepatient,thephysicianwilladjustthepositionofthe electrodesuntiltheareaofpainfeelscoveredbyatinglingsensationcalled Copyright2016 2 paraesthesia(thistechniqueiscalled topographicalmapping).Oncethe positionischosen,theleadissecuredin place.Othertechniquesmayrelyupon ananatomicaltargetbeingcoveredwith electricalcontactsconfirmedbyX-ray. Ratherthaninsertacylindricallead, someneurosurgeonsprefertodoasmall surgicalprocedureanddirectlyplacea paddle-typeelectrodewherestimulation willbedelivered. Usuallyatrialperiodisofferedandin mosthealtheconomies,reimbursement forapermanentsystemwillonlybe providedifanadequateresponsetothis trialperiodisachieved.Forinstance,a responseisgenerallyconsidered adequateifpainisreducedbyatleast 50%althoughimprovementinfunction andactivitylevelmayalsobea consideration. Thepatientspendsatrialperiodofabout sevendays(sometimeslesssometimes more)withanexternalpulsegenerator thatiscarriedonabeltorinapocket. Somehealthcarespecialistsare questioningthebenefitofaprolonged trialperiodiftheindicationand multidisciplinaryassessmentis supportivewithsatisfactoryon-tabletrial responsesfromthepatient. Theteamwillhaveexplainedhowtouse thestimulatordeviceandhowrelevant outcomeswillbeassessed.Usuallythe trialperiodiscarriedoutathome. Patientsreceiveahand-heldexternal controlunit.Thisallowsthemtoswitch betweenprogramsthroughoutthedayin ordertoobtaindesiredcoveragein differentpostures,suchassittingorlying down. Thereareafewprecautionsregarding whereandwhentouseactive stimulation,however.Itisnotadvisedto turnonstimulationwhileoperating heavyequipmentordriving. T-SCS11.16 6 5 SpinalCordStimulation PermanentImplantationistheSecondPhase Aftertryingthetherapyforaboutaweek,apatientwhohasexperienceda reductioninpainbyatleasthalfmaychoosetocontinuetreatmentwitha permanentsystem.Somepractitionerswillusetheexistingleadfromthe trialandotherswillhavepreviouslyremovedthatandwillinsertnewleads. ForpatientschoosingapermanentSCSoption,animplantablepower source,aroundthesizeofaman’swatchfaceisgenerallyimplantedunder theskin–eitherintheupperbuttock/back,upperchestwall,orabdominal area. ManagingtheSCSsystemtakessomeoversightandcommitmentonthe partofthepatient.Whiletheincisionmadeonthepatient’sbackusually healsafterseveraldays,surgicalpainfromtheimplantedpulsegeneratoror receivermaylastuptosixweeks.Patientsareadvisedtoavoidstretchingor twistingmotionsthatmaydisplacethesystem. WaystoPowertheElectricalStimulation Theimplantablepulsegenerator(IPG)containsthebattery,microprocessor andfeed-throughconnectionsallsealedwithinatitaniumcover.Thereare twodifferenttypesofimplantablepowersources,theprimarycell(nonrechargeable)andrechargeablebattery.Athirdtypeofdevicehasno batterybutcanbepoweredeitherbyinductionormegahertzfrequency fromcloselyappliedexternalpowersources. Primarycelldevicesareusuallylargerandlesscostlybutwillhavealimited durationoflifeexpectancy.Theyareunabletosupporttheenergydemands ofmanyofthenewersub-perceptionstimulationparameters.Howeverthey aresimplertouseandifusedatstandardratesmaylastuptofiveyears beforeneedingtobesurgicallyreplaced. Rechargeablebatteriesarechargedbyinductionwithachargingunit positionedovertheIPGforanhourortwoeveryfewdaysdependingupon useandpreferredprogramming.Arechargeabledevicecanlast,depending uponmanufacturer,between10and25years. FutureConsiderationsConcerningSCSTreatment Leaddesignscontinuetoevolveforenhancedfunction.Overthedecades leadcontactshaveincreasedfromonetofourtoeightand16electrical contacts.Theaimisnotonlytotreatmulti-sitepainbutalsotobeableto controltheelectricalfieldbettersothatpainreliefcancontinueformany yearstocomewithoutneedforarevisionprocedure. MRIexaminationsinmedicinehavebecomeincreasinglycommonplace. SomemanufacturershavecreatedSCSdevicesthatcannowbesafely presentduringanMRIaslongasmanufacturer’sguidanceisfollowed. http://www.neuromodulation.com/for-patients Copyright2016 3 Newsub-perceptionstimulation parameterscanresultinpainreduction withoutthepatient’sawarenessof stimulation.InconventionalSCS,the stimulationcreatestinglingsensations intheareaofpaincoveredcalled paraesthesiae.Aspractitionersgain experiencetheynotethatsome patientsprefertheparaesthesiaeand othersparaesthesiaefree.Some patients,iftheirdeviceallows,liketo togglebetweenthetwodepending upontheirpaincircumstances. MaximalbenefitfromSCSmaydepend upontheconstancyandconsistencyof thestimulation.Feedbacksystems usingabuilt-inaccelerometerallow automatictogglingbetweenpreset programmescorrespondingtoeach bodyposition. Anewmanufacturerhasthe technologytomeasurethespinalcord effectsofSCSandautomaticallyadjust thestrengthofitsstimulationtokeep thetherapeuticstimulationconstant. TheTherapy’sPotentialRisks, BenefitsandNewDirections Occasionallypatientsexperience devicecomplications,suchasa displacedlead,internallyfractured electrode,ordevicemalfunction.Major complications,however,arerare, althoughatworstcomplicationsofthe implantcanincludeparalysis,nerve injuryanddeath. Complicationratesshouldgenerallybe lowerinthehandsofanexperienced practitioner.Themedicalproblems mostoftenseenarebleedingatthe siteoftheimplant,orinfection.Insuch instances,removalofthedeviceand antibiotictreatmentaregenerally required.Infectionratescanbeaslow as1%,butmayriseto4%insome centres. T-SCS11.16 7 SpinalCordStimulation Mechanicalcomplicationssuchasleadmigrationarereducingdueto improvedtechnologyandskilledtechnique.Persistentpainatthelead anchorsiteandimplantablepulsegeneratorpocketareimportantin 20%ofpatientsandupto5%ofpatientsrequireapocketrevisionin ordertoachievebettercomfort. Long-termoutcomeswithSCSarevariable.Mostpatientscontinue withgoodpainreduction.Afewfindthattheirlong-termpain conditionresolves,butsomedeveloptolerancetotheeffectsof stimulation.Newsub-thresholdprogrammingmayrestorepainrelief insomeofthesecasesofstimulationtolerance.Otherpatientswill requireadditionaldiagnosisandpaintreatmentandsomewillneeda revisionoftheSCSprocedure. Inhealtheconomicsstudies,thecostofanSCSsystemhasbeen estimatedtopayforitselfwithinthreetofouryearswhencomparedto usualcare.Patientswhobenefithavefewermedicalvisits,reduced painkilleruse,improvedhealth-relatedqualityoflife,bettersleep quality,greateractivitylevels,andmaybemorelikelytoreturnto work. RapidadvanceshaveexpandedSCSoptions.Techniquestobetter controltheelectricalfieldwithmultiplecontactsandfeedbacksystems andsub-perceptionstimulationprogrammeshavebeenwelcome additions. Anew,FDA-approvedtargetforneurostimulationwithinthevertebral canal,meanwhile,isthedorsalrootganglion(DRG)–aneasily accessiblestructureattheedgeofthespinethatplaysakeyroleinthe developmentandmanagementofchronicpain.Recentadvanceshave allowedtargetedDRGstimulationforprecise,constantsubliminal stimulationforareasofpainthatinsomecaseshavebeenelusive. Thenetresultofallthesetechnologiesistoimprovelong-term outcomesatanaffordablecostinanever-widerrangeofpatients. Pleasenote:Thisinformationshouldnotbeusedasasubstitutefor medicaltreatmentandadvice.Alwaysconsultamedicalprofessional aboutanyhealth-relatedquestionsorconcerns. http://www.neuromodulation.com/for-patients Copyright2016 4 T-SCS11.16