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SpinalCordStimulation
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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.
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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.
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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
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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.
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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.
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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.
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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.
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