Downloaded from http://aim.bmj.com/ on June 17, 2017 - Published by group.bmj.com
euro athicPain:
A NewTheoryfor ChronicPain
of IntrinsicOrigin
Reprinted by kind permission of'Annals ofThe RoyalCollegeof Physiciansand Surgeonsof Canada"
Vol22, No. s, luly 1989p327330
Pourquoi I'acupuncture est-elleaccepteedans les pays
de I'Est, surtout pour le traitement de la douleur
chronique, maisnon dans I'Ouest?Le fait que le modus
operandi de I'acupuncture nbst pas pleinement
compris en est un; Ie caractdrc 4nitmatique de Ia
douleur chronique en est un autre. Dans son article,
I'auteur pr'sente
concept de la douleur
chronique et suggare de quelle faqon I'acupuncture
peut la soulager.
Les causes de la douleur chrcnique peuvent Ctre
extrinsdquesau systemenetveux (i.e.l6sion percistante
ou inflanmation), mais aussi intrinsiques suitu e one
hypersensibilit' (supercensitivite) clesstructu res atteintes
de neurcpathies ou cl'6nervationpartielle.
La douleur neurcpathique lrappe typiquement le
systememusculo squelettique et le spasme,ou Ie racourcissementmusculaire, est pattie intdgrante de ce type
de douleur Le spasme peut causer une douleur
lo.ali<de au mu>cle. mai, Ie .pacme ou le ra.ou^ ^,epeut aussi surchager
ment musculaire prolon*
nAcaniquenent les tendons et leurs attaches et
produire une douleur dans ces structuret
Ladouleur neuropathiqueest diffdrente de la douleur
nociceptiveou inflammatoireet son traitementaussi est
difl4rent (d6sensibilisationde la supersensibilhd).La
plupart des modes de traitement de ces douleu$,
comme la chaleut les massagesou l'4lectrostimulation
periphdriques dAsensibilisentpar stimulation t4flexede
la partie atteintq via son innetvation intacte.Ces modes
cle traitement sont toutefoispassifset Iimitds dans leur
portee; Ia stimulation cesse une fois leur application
termine6.Parcontnste, les techniqu espar piqArcs,dont
l'acupuncture,ont un r6sultatmeilleur et de plus longue
dur6e, parce que le traumatisme tissulairc quhlles
produisent peut cl6clanche4 par son courantl une
KEYWORDS:CHRONIC PAIN, NEUROPATHYSPON- source corporelle de bio1nergie curative. La l4sion
ACUPUNCTURE,
DECENERA- tissulairelibdre en plus le facteur de croissanced4riv4
DYLOSIS,
MUSCLE
5PASM,
des plaquettes qui peut favoriserla gu4rison.
TIVECHANCES,
OSIEOARIHRITIS.
for
Why is acupunctureacceptedin the East,especially
the treaiment of chronic pain, but not in the West?
One reasonis that the modusoperandiof acupuncture
is not fully understood;anotheris the enigmatrcnaiure
of chronic pain. This articleintroducesa new concept
of chronic pain, and suggestshow acupuncturemay
relieveit.
Chronicpain mayarisefrom sourcesthat areextrinsic
to Ihe ne.vou5cv\tFm,lor F\dmple.ontorng iniurv o'
inflammation),
but it can alsobe intrinsicand the result
(supersensitivity)
in neuro
of abnormalhypersensitivity
pathicor partiallydenervatedstructures.Neuropathic
pain iypicallyaffectsthe musculoskeletal
system,and a
pivotalcomponentof this type of pain is musclespasm
or shortening.
Spasmcancausepain localised
to muscle,
but sustainedmusclespasmor shorteningmechanically
overloadstendonsand their attachments,
and can produce pain in thesestructures.
Sinceneuropathicpain is differentfrom nociception
or intlammation,its treatmentis also disiinct (desenMost physicaltreatment
sitisationof supersensitivity).
for this type of pain,suchasheat,massage
or
modalities
transcutaneouselectrical nerve stimulation (TENS),
desensitiseby reflex stimulation ot the affected part via
its intact inneryation-Howeverthese modalitiesare
passiveand limited in scope.Stimulationends when
their applicationis terminated.ln contrast,injection
techniques,includingacupuncture,are more effective
and longlastinB,becausethe tissue injury that they
producecan unleashthe body'shealingsourceof bioenerSythroughthe cfrfent of injury.Tissueinjury also
releasesthe platelet'derivedgrowth factor (PDCF),
which can promotehealing.
emphasisesthe subjectivenature of pain, and recoS"The bane of pain is in the brain."The lnternational nisesitsexistence
in the absenceof a detectablephysical
"an
for rhe Siudy of Paindefinespain as
Association
Medicaldiagnosistradilionallypresumesthat painisa
unpleasantsensoryand emotionalexperienceassociated
with actualor potentialtissuedamage,or describedby signalof tissueinjury conveyedto the centralnervous
the patient in terms ol such damage."The definition system(CNS)via a healthyneryoussystem.Although
50
Downloaded from http://aim.bmj.com/ on June 17, 2017 - Published by group.bmj.com
pain may be Jinkedcalrsallyto tissueinj!ry, it need not
be so. Injury does not alwaysgeneratepain, nor does
pajn alwayssignalinjury.Also,when there is abnofmal
tunction in the nervoussystem,pain perceptioncan
d . p f o r n u n - - o \ r o u .i n p u t .a n d . p u | | o L \ p d r n' d evenarisefrom within the body.This articleinvokesthe
physiologyof the abnormalneural responsesthat can
occuf in neuropalhylo explain inlrnsic pain and 10
presenta rationaletor its treatment.
ludeto healing.
Alter injury, most people heal rapidly and become
pain lree.In sonre,pain pefsislsbeyondthe usualtime
for the healinSprocessand becomesinlfactable.This
chronic pain,or Wall'sthird phase,is likelyto occur if
. ongoingnociceptionand inflammation
. psychological{actors
sLrchasa somalisation
disordef,
depressionor operantlcarninBproccsses
a functionalor slructuraldisturbancesin the nervous
Wall saw pain as a feactionpattefnol thfec sequenlial
system.Ihese generallyoccur in the peripheralneF
behavioufalphascs:immediate,acule and chronic (1).
vous system(for example,perjpheralneuropathy),
Eachphasemayexisrindependenlly,
or in anycombinaand the term "neufopathicpain" is appliedto this
tion and proportionwith the others.
category.
Wallt immediatepha!e,or nociception,is the percep'
tron of a noxiousinput. Nociceptivesignalsare sent to
thc bfain via two main routes.One, the spino feticulo The normaJ physiologicalproperties of nerve and
thaJamlctracl, is evoutionarily primitive,has rnany muscle depend on inlact innenation to provide a
synaplicfeJays,
and endsal the lowef parlsoi lhe braln, regulatoryor trophic effect.Formerly,it was supposed
where it arousesthe emotions and switcheson the that the trophic factorwas lost with total denervation,
body'sresponseof "fight or flight'1lts effectsmay not leading to "denervationsupefsensitlvity"(2). More
diffuse into the consciousbrain.Forexample,nocicep- fecenlly,iL has bccn sholvn, lhal any measLrrelhal
tive perceptionmay not occur "in the heat of battle'i blocks the flow of motor impLlses,and deprivesthe
when thereare other pressingdistractions.
The second effectororgan of excitatoryinput for some time, can
lracl,the neo spinothalamic,
in that organ,and in
evolvedlater,and is morc cause"di5usesupersensitivity"
ellicient,fcq!irlng only threerelaysto reachthe sensory aslociatedspinal reflexes(3). With supersensitjviiy,
cortex that locaiesthe paln. Thus, pajn locationcan nerves and innervated structures become overly
occur beforeits realisation.
scnstive and reactabnorrnallyto stirnuli,accordingto
Nociceptionis usuallytransient,unlessthereis tis!ue Cannonand Rosenblueth's
law of denervation(2)l
"When in a series of efferent neurons a unit is
injury and damagedcellswith the releaseof allogenic
substance!(Jorexample,histamineand bradykinin)that
destroyed,
an increasedirritabilityto chemicalagents
induce inflammatorypain, or Walls acutephase.Anti'
delclops in the isolatedstructureor structures,the
effeclbcing marlmalin the pa|t directlydenervaled."
nflammatorydfugs havetheir applicationin this phase,
Cannon and Rosenbluethrecognisedfour types of
b!t the abatementof inflammationwith drugs can be
increasedsensitivity:the amplitude of responsesis
counterproductive/becauseinflarnmationis the pre
5l
Downloaded from http://aim.bmj.com/ on June 17, 2017 - Published by group.bmj.com
unchanged,
but theircourseis prolonged(superduration axonssend out sprouts,thus enlargingthe territoryof
invasion).
Contfactionoi lhese
of response);
the thresholdfor the stimulatingagentis the nrotor u nit (territorial
as
lowerthan normal (hyperexcitability);
lessen€dstimuli enlarBedmotor Lrnilsis seen in electromyography
"giantwavei".
lhat do not havc to exceeda threshold produce re
Similar abnormalitiesmay also occur in smooth
sponsesoi normalamplilude(lncfeased
susceptiblity);
and the ability of the tissuelo respondis augmented rnu!cle (7). When vascularsmooth muscle tone is
(ruperreaclivity).
I-his gives
Theyalsoshowedthalsupersensllivily increased,the result is vasoconstrictior].
can occur in many structuresof the body including neuropathicpain itscardinalfeat!re aflectedparlsafe
skeletalmuscle,smooth muscle,spinal neurons,sym- .older (as may be shown by thermography).When
pathcticgdnglia,adrenalgldnds,sweatglands,and brain lymphalic drainage is impaired,there can be oca
Thesecan be
cclls.Fu(llcrnofe, they showedthat denervatedstruc oedema(tfophicoedemaor tfophedema).
test
lurcs overrcacl lo many chcm c.rl and ph),scal inpLrls confifmcdby the peaud'orangeeffector matchstick
(B).Trophedemais non-pittingto digital pressufe,but
ncludingsireich and pfessufe.
Probablythe most crucialstrLrcture
lo developsuper when a blunt instrument,for example,lhe end of a
sensitivityis striatedmuscle.Apart from the pain and matchstickis used,the indentationproduceciis cleaF
tendernessthat mayo.cur if muscle(possiblyfrom the cLrland pefsrslstof minutesSupersensitivity
maylikewiseaffectnervefibres,which
nociceptors),
neuropathy
.omprcssionof superscnsitive
at every
ncreasesmuscletone (spasm)and concuffentrruscle mav becomesensitiveto chernicaltransmitters
leature point alongiheir lengih inliead of only at the tefminals
sho(cning.MLrsclcshortcnlngls a fLrndamental
p.rlnsyndromcsand maybe palpaled (7).Sproutingmayalsooccur in nerves,and denefvated
of musc!loskeletal
' u r o n \ T d ) , r '' p p l , o n l n r \ I o T o h P rl \ p p . o i n P n P \
as ropybandsin muscle.Thesebands,usunllypa n free,
(trigger
(4).
ncluding
panful
points)
aLrlonomicand sensorynerve fibres.Ihese
may become iender and
When muscle bands are fibrotic and painful, the porsibleshortcircuiLsbeiweensensoryand autonomi.
nervesmaycontribut€to reflexsympathclic
conditionis known astibromyositis,
fibrositis,or diifuse (vasomotor)
dystrophyor causalgicpain(7).
pain syndrorne(s).
myofascial
Discussionof other possiblemechanismsfor supef
Musclesho(eningp!ts mechanicalstress
on tendons
and their attachmcnts,and can generatecondilions sensitivity and abnormal impulse generation (for
s u c h a s l c n d o n i l i s ,l e n o s y n o v l l iasn d e p i c o n d y l i t i s .example,changesin ion channcls,membranecapac< r . r " n i n 8 - m L r .l' P r h .I
tance, voltagedependcnl channel gating, currentjoinl pressure,Lrpsetaljgnment,and causearthralgia. dcpcndcnt mcchanlsms,ephaptic transmissionand
the scopeof thlsarticle.Theywerethe
Mus.le shorteningln para-spinal
musclescancompress others)is oLrtside
and cJinicians,
in which
.rd s. spaceand narrowthe intervertebfal
foramina.The Iocusol a meetingol scienllsts
were
manvsyndfomescausedb), abnormaldischarges
nerveroot may then be irritatedthrough pressureof a
bulgingdi!c, or compressedafler it emerges.A vicious identified(7).
circe can thus arise:pressureon a nerve root causes
neuropathy,ncuropathyleads to pain and spasnrin
U r l r , e n o , . p p ro , - d r - t l a r rn a r " r * h o . e - o r t n u .
targetmuscles,includingparaspinalmuscles;spasmin
exirinsic to a normal nervous system,
paraspinalrnusclescompressesthe nerveroot. Often,
pain reliei is only possible lvhen spasms in both neuropathicpain may be the resultof an abnormally
nervoussystemdistortinBnon noxioLrs
stimuli
sensitrve
peripheraland pnr.rsplnal
musclesafe released.
nLo lalse pain alarms,and spuriouspain signalsmay
Ncuropalhyalso affeds the qrality of collagen.The
amounLol colltrgenin sofr and skeletaltissuesmav b-. occursponlaneously.
Pefipheralneuropathycan o.cur from many causes/
red!ced. Replacementcollagef has fewer cross-links
than norma matureco lagen(6).Be.ause but probablythe most common causeis mechanical
and is $reaker
in
irritation,especially
of the nerveroot (radicLrlopathy)
tenclons,ca(i
collrgcngivesthe strengthto igaments,
and mofpho
in
spondyosis (the strucluraldislnLeBfalion
lagcand bone,ne! ropathycanexpediteclegeneration
anclsurround
weight-bearing
and activitystfcssedpafls ol lhe body, logicalchangesin the intervertebraldisc
Becausespondylosisis a conseqLence
for exarrple,spondyl,rsls,
disco8enicdiseaseand o!leo- ing slrLrctLrres).
arthritis.Suchpfosalcalf iclionsare vielr,edas primary o l s e r r " n d t e d r n F L r o o d t hpr d r nr . T o e ' o m ' r o r I
individualr.
conditions,
but are mosl likelysecondarylo neLrropathy. middle-aged
Neuropathy,and muscle lpasm and shorteningcan
ln dencrvation,a musclecan become "twltchy" for
pain syndromesthat
manyreaion, (1. Evenat rest,when there is no Incom- accountfor manyrnusculoskeletal
ing signal,muscle fbres rnay generatespontaneous are now labelled with non descriptivenames otten
endingin'algia or itis,for examplc,mcLatafsalgia,
afthcontractions
or "fibrillations'lThismaybe the resultoi a
ralgla,or litcfal epicondylilis.
When muscleshoftening
malfunctionof thc sodium pump and changesin the
with neuropalhi.degradationol collasen,
electricalpropetiesof nrusclemembrane.Upon arrival s associated
of an incomingelectricsignal,releasedacetylcholine degenerativechangescan occLrr,for example,osteo
but may activale arthfllis. ll is also porsible thal other unpleasanl
mayact,not only al molor end-plates,
perceptionsnot classifiedas pain, such as tinnitus,
entiremuscleiibresat newlyformed cl!stersof recep
tors, or "hol spolr'l This abnormalresponsemay be vertigoand itch, may be explainedby Cannon'slaw.
acetylbecalrsethe amount of avaiLable
exaggerated,
Molof
un
ls
may
be
Jnay
be
reduced.
cholineeslefase
a b n o r m ayl . r g " . \ h c - n u { ' , l l . n ' T o o r u n i l Sincethe mechanismof neufopathlcpain is diffefent
irom nociceptionand inllammation,ils diaBnosisand
become denervated,the deprved iector may be
Diagnosisis
invadedby survivingaxonstrom adjacentunits.These treitment rcqLriredillefent approtrches.
52
Downloaded from http://aim.bmj.com/ on June 17, 2017 - Published by group.bmj.com
p l a s m a ( i n t e r s i i t i a fl l u i d ) a n d w o u l d o n l y s e e t h e p l a t e l e t
f a c i o r i n t h e p r e s e n c eo f i n j u r y , h e m o r r h a g e a n d b l o o d
coaguraron,
mainlyclinical,and can be confirmedby signsof neuropathy (tharare differentfrom the well-knownones of
ouiright denervation,such as absent reflexesand loss of
sensaiion).
Thesesubtlesignscan be found if the clinician knows where to look, and whai to look for (8).
and radiologicaltestsare unhelpfulin early
Laboratory
Treatmentof ne!ropalhicpain is alsodifferent.Superby the alleviationof
sensitivityrequiresdesensitisation
Nerveentrapments
areLrsually
obvious,and
neuropathy.
released,
therebyrestoringneryefuncmaybe surgically
tion. However,neural irritationand neuropathyoften
occurwithout entrapment,and surgeryis not indicated.
and alltheother
Lomohasshownthat sLrpersensitivity,
featuresof denervationin muscle,can be reversedby
Continuouselecstimulatingthe musclewith electricity.
trical stimulationsubstitutedfor the trophicfactorthat
is deminishedor absentin neuropathy(9).In a comparable manner,physicaltherapythat is usedto ireatmusculoskeletalachesand pain may be likenedto electrical
stimulation.
therapies,includAll physicaland counieFirritational
ing acupuncture,may achievetheir ef{ecr by reflexstimulation,sincethey are effectiveonly if the nerveto
the painful part is still intact.Their applicationexcites
iheirta€et
receptors(in skinand muscle)and stimulates
indirectly.For example,massageand focal pressure
activatetactile and pressurereceptorsiexercise,traction
and manipulationstimulatemusclespindlesand Colgi
organs;heat (including ultrasound)and cold act on
thermal receptors.Ihese stimuli are sensedby their
specificfeceptorsand relayedto the spina{cord.As with
the patellarreflex,stimulationreachesthe affeciedpart
via a reflex.It is the reflexresponsein efferentfibresto
the affectedstructurethat stimuiatesthe therapeutic
target.Evenacupunct!reis effectiveonly if the nerveto
the painfulpart is still functioning,and its effeFtcan be
blockedby a localanesthelic(10).
Unfortunately,
all externalforms of physicaltherapy
andwhen application
havea drawback.Theyarepassive,
ldeally,stimLrlation
should
is halted,stimulationceases.
which may be recruited
usethe body'sown bio-energy,
in the form of the "currentof injury",first describedby
Calvaniin 1792This curreni is teneratedwhen tissueis
includingacupuncture.
damaBedby injectiontechniques
Unlikeexternalformsof stimulation,needlesiimulation
penetratesinto muscle.Injufy potentialsihat are dis
cha€ed on needle inseflion can relax musclespasm
instantlyor within minutes.lt also inducesa sympath
olyticeffectthat spreadsthroughouithe body segmenl,
Painin muscles,
tendonsand
releasing
vasoconstriction.
joints caused by muscle tension is easedwhen the
and objective
shortenedmusclesare relaxed.Subjective
improvement (which can sometimes occur within
m n u r F \ ' d n b e I o n r " ' n e d f o r a \ d T p l F b v d - I n rr p d ' e
in joint range,and minor degreesof joint effusionmay
resolve.Endogenousopiates, now used to explain
acupunctufe,cannotacco!nt for all its effects(11).
Needlestimulationcan lastfor severaldaysunlil the
miniature wounds heal- Needlin6 may have another
to other forms ol localiheF
uniq!e benefitunavailable
apy.It deliversto the injured afea the platelet-derived
growth faclor (PDCF),which inducesdeoxyribonucleic
acid (DNA)synthesis
and stimulatescollagenlormation
(12).Body cells are normally exposedto a filtrate of
The neuropathy pain model has been proposed as an
hypothesis to explain chronic musculoskeletal pain
problems of obscure ofigin. lt enables many musculoskeletal pain syndromes to be grouped under one
etiologic classification(neuropathy). Like all models,
h o w e v e r ,t h i s o n e n e e d s r e f i n e m e n t .
It is probable that all forms of physicaltherapy act
t h r o u g h o n e c o m m o n m e c h a n i s m ( r e f l e xs t i m u l a t i o n ) .
These therapies soothe pain temporarily,but a needle
t e c h n i q u e i s m o r e e f f e c t i v e .l t s t i m u l a t e s t h r o u g h t h e
c u r r e n t o f i n j u r y , w h i c h m a y l a s t f o r d a y s .N e e d l i n g a l s o
r e l e a s e sg r o w t h { a c t o r s t h a t m a y p r o m o t e h e a l i n S . F o r
m e a n i n g f u l r e s u l t s , h o w e v e r ,a n y u n d e r l y i n g c a u s e o f
neuropathy must be eradicated.
tu C Chan Gunn
Visitingscient!stand consultant
Mu hi d iscipli nary PainCentre
Universityof WashingtonS.hoolof Medi.ine
53
Ad d ress fo I co r respo n d ence:
Cunn PainClini.
828 W Broad||ay
vancouver, 8.C. VsZ 1J8
1 WALLPD,On the relarionof injury to Pain,TheJohn l
bonica lecture, Pain 1979;6: 25Itj1.
2 C.{NNON WB and ROsENBLUETH
A, Ihe tupef-setsttvr.),
of denervatedstructures:A law of denerration. New York:
Ihe Mac Millan Ca.,1919.
3 SHARPLE55
SK,Supersensitivitylikephenomena in the
central nerwus system,FederationProc 1975;31(70):
199U2
4 TRAVELL
J and STMONSDC, Myofascialpain and
dysfunction.ln: The triggerpoint manual,Battimore:
Willians and Wilkins, lgu.
5 SOLAAE, Ireatmertof my(,fascialpainsyndrones, ln:
Advan.es in pain researchan.Jthenpy, vot. Z New York:
RavenPress, 1981i16785.
E C ,z r n o v e r o l
6 K L E I NL , D A W s O NM H a n d H E I P L K
.ollagen ln the adult nI after clenervation,J Bone loint
Surg 1977;59/': 1065-z
7 CULPW and OCHOA j, Abnormal nervesand muscte. at
inpulse Benerators,Ne|| York:Oxford Univercity Press,
1982.
I CUNN CC and MILBRANDTWE, far4, and srbrle i,anr ln
Iow back sprain, Spine l9ni 3:26781.
LoMo I, The role of actirny ih the.ontrolof metnbnne
and contra.tile prapetlies ot skeletalmuscle, ln: Ihesleff
5, ed. Motor inhetratian of nuscle, Ncw York:A.ademi.
' H A\ur \ , HA\(-' I I HlJnt drd\A.JKl
Peripheralafiercnt pathwayfot acupun.ture anatgesia.5ci
T ,I C O I . P I T TYSa n d C E R L A C H
1 l C H A P M A NC R ,B E N E D E TC
R, Naloxonefails to reversepain thrcshol<lselevatedby
ia rccansidere.l,Pai n
a.L pun.tLt re: Acupu ncture analSes
19a3;15:1629.
ROSSR and VOCELA, Ihe platelet-.lerive.lgrowth tactor,
Ce||1978;l1: 2B-1A
Downloaded from http://aim.bmj.com/ on June 17, 2017 - Published by group.bmj.com
Neuropathic pain: a new theory for chronic
pain of intrinsic origin
C Chan Gunn
Acupunct Med 1989 6: 50-53
doi: 10.1136/aim.6.2.50
Updated information and services can be found at:
http://aim.bmj.com/content/6/2/50
These include:
Email alerting
service
Receive free email alerts when new articles cite this article. Sign up in the
box at the top right corner of the online article.
Notes
To request permissions go to:
http://group.bmj.com/group/rights-licensing/permissions
To order reprints go to:
http://journals.bmj.com/cgi/reprintform
To subscribe to BMJ go to:
http://group.bmj.com/subscribe/