Rev. bras. ortop. vol.49 número5

w w w . r b o . o r g . b r

Review

Article

Carpal

tunnel

syndrome

–

Part

I

(anatomy,

physiology,

etiology

and

diagnosis)

夽,夽夽

Michel

Chammas

_,

_Jorge

_Boretto

_,

_Lauren

_Marquardt

_Burmann

_,

_Renato

_Matta

_Ramos

_,

Francisco

Carlos

dos

Santos

Neto

_,

_Jefferson

_Braga

_Silva

a_{HandandUpper-LimbSurgeryService,PeripheralNerveSurgery,HospitalLapeyronie,UniversityHospitalCenter,Montpellier,France}

b_{HandSurgeryService,ItalianHospital,BuenosAires,Argentina}

c_{HandSurgeryService,HospitalSãoLucas,PontifíciaUniversidadeCatólicadoRioGrandedoSul(PUC-RS),PortoAlegre,RS,Brazil}

a

r

t

i

c

l

e

i

n

f

o

Articlehistory: Received10July2013 Accepted28August2013 Availableonline20August2014

Keywords: Carpaltunnel

syndrome/physiopathology Carpaltunnelsyndrome/etiology Carpaltunnelsyndrome/diagnosis Mediannerve

a

b

s

t

r

a

c

t

Carpaltunnelsyndrome(CTS)isdefinedbycompressionofthemediannerveinthewrist.It isthecommonestofthecompressivesyndromesanditsmostfrequentcauseisidiopathic. Eventhoughspontaneousregressionispossible,thegeneralruleisthatthesymptomswill worsen.Thediagnosisisprimarilyclinical,fromthesymptomsandprovocativetests. Elec-troneuromyographicexaminationmayberecommendedbeforetheoperationorincasesof occupationalillnesses.

©2014SociedadeBrasileiradeOrtopediaeTraumatologia.PublishedbyElsevierEditora Ltda.Allrightsreserved.

Síndrome

do

túnel

do

carpo

–

Parte

I

(anatomia,

fisiologia,

etiologia

e

diagnóstico)

Palavras-chave: Síndromedotúneldo carpo/fisiopatologia Síndromedotúneldo carpo/etiologia Síndromedotúneldo carpo/diagnóstico Nervomediano

r

e

s

u

m

o

Asíndromedotúneldocarpo(STC)édefinidapelacompressãodonervomedianonopunho. Éamaisfrequentedassíndromescompressivaseacausamaisfrequenteéaidiopática. Aindaqueasregressõesespontâneassejampossíveis,oagravamentodossintomaséaregra. Odiagnósticoé,acimadetudo,clínicopelossintomasetestesprovocativos.Umexame eletroneuromiográfico podeserrecomendado no pré-operatórioouem casodedoenc¸a laboral.

©2014SociedadeBrasileiradeOrtopediaeTraumatologia.PublicadoporElsevierEditora Ltda.Todososdireitosreservados.

夽

Pleasecitethisarticleas:ChammasM,BorettoJ,BurmannLM,RamosRM,dosSantosNetoFC,SilvaJB.Síndromedotúneldocarpo– ParteI(anatomia,fisiologia,etiologiaediagnóstico).RevBrasOrtop.2014;49(5):429–36.

夽夽

WorkdevelopedbyamultinationalteamattheHandandUpper-LimbSurgeryService,PeripheralNerveSurgery,HospitalLapeyronie (UniversityHospitalCenter),Montpellier,France,andattheHandSurgeryService,HospitalSãoLucas,PUC-RS,PortoAlegre,Brazil.

∗ _{Correspondingauthor.}

E-mail:jeffmao@terra.com.br(J.B.Silva). http://dx.doi.org/10.1016/j.rboe.2014.08.001

Introduction

Carpal tunnelsyndrome (CTS) isthe most frequentofthe compressivesyndromesandisdefinedbycompressionand/or tractionofthemediannerveatwristlevel.Itsfirstdescription isattributedtoPaget,1 _{whoreportedonacaseof} compres-sionofthemediannerveconsequenttoafractureofthedistal radius.In1913,MarieandFoix2_{publishedtheanatomicaland} histopathologicaldescriptionofanhourglass-shapedlesion ofthe mediannervewithneuroma, proximaltothe flexor retinaculum.Inthe1950s,studiesbyPhalen3_{establishedthe} principlesofCTS.

TheestimatedprevalenceofCTSamongthepopulationis between4%and5%,particularlyaffectingindividualsbetween 40 and 60 years ofage.4 _{In 2008, 127,269 individuals aged} 20yearsand overwereoperatedtotreatCTSin metropoli-tan France,representing an incidenceof2.7/1000(females: 3.6/1000;males:1.7/1000).5_{Thereweretwopeakfrequencies:} thefirstandhigherofthembetween45and59yearsofage (75%female);andthesecondbetween75and84years(64% female).

Anatomy

Limits

The carpal tunnel is a non-extendible osteofibrous tunnel definedasthespacelocatedbetweentheflexorretinaculum, whichformstheroof,andthecarpalsulcus,whichformsthe base.Itisdelimitedontheulnaredgebythehamatehook, pyramidalboneandpisiformbone,andontheradialedgeby thescaphoidbone,trapezoidboneandtendonoftheflexor carpiradialis(FCR)muscle.Thebaseisformedbythecapsule, andtheanteriorradiocarpalligamentscovertheunderlying portionsofthescaphoid,lunate,capitate,hamate,trapezium andtrapezoid.

Content

The median nerve is accompanied by four tendons from the superficial flexors of the fingers, four tendons from the deep flexors of the fingers and the long flexor of the thumb.Thelongflexorofthethumbisthemostradial ele-ment.

Atthetunnelentrance,themediannerveissituated dor-sallyinrelationtothelong palmarmuscle orbetweenthe FCRandthelongpalmarmuscle.Inneutralwristposition,the mediannerveisinfrontofthesuperficialflexoroftheindex finger,orbetweenthelongflexorofthethumbandthe superfi-cialflexoroftheindexfinger,orinfrontofthesuperficialflexor ofthemiddlefinger.Inthedistalpartofthetunnel,themedial nervedividesintosixbranches:themotororthenarbranch; threespecificpalmardigitalnerves(radialand ulnarofthe thumbandradialoftheindexfinger);andthecommon pal-mardigitalnervesofthesecondandthirdspaces.Thethenar branchpassesthroughaseparatetunnelbeforeenteringthe thenarmuscles,in56%ofthecases.

Anatomicalvariations

Anatomical variationsmay explainthevariationsin symp-tomsandgiverisetorisksofiatrogenicinjuries.

Anatomicalvariationsinthenerves

Abifidmediannervecausedbyhighdivisionisobservedin 1–3.3%ofthecasesandmaybeassociatedwithpersistenceof themedianarteryorwithanaccessorybranchofthe superfi-cialflexorofthethirdfinger.6_{Incasesofabifidmediannerve,} theradialportionisthemostimportantone.

Variationsofthemotorbranchofthemediannerve

Lanz7 _{foundfive typesof startingpoints and pathsof the} thenarbranch:theextraligamentousform,whichisthemost frequenttype(46%);thesubligamentousform(31%)andthe transligamentous form(23%). Kozin8 _{found that 4%of the} caseshadtwomotorbranchesthatcrossedtheflexor retinac-ulum.Thenervebundlesdestinedforthethenarbranchare locatedradiallytothemediannervein60%ofthecases, ante-riorlyin20%and centrally in18%.9 _{Sometimes,the thenar} branchpassesthrough atunnelbeforeenteringthe thenar muscles. These variations may explainthe variable motor impactincasesofseverecompressionofthemediannerve.9

Variationsofthepalmarcutaneousbranchofthemedian nerve

Thepalmarcutaneousbranchusuallybegins4–7cmabovethe wristcreaseandfollowsalongbesidethemediannervefor 1.6–2.5cm.Itthenentersatunnelformedbythefasciaatthe medialedgeoftheFCRandemerges0.8cmabovethewrist flexioncrease,toinnervatetheskinofthethenareminence. Thepalmarcutaneousbranchmaycrossthetransverse liga-mentofthecarpusormaygototheulnarsideofthemedian nerve.6

Intratunnelpositioningoftheulnarnerve

Itis extremelyrare tofindthe ulnar nerveinsidethe tun-nel.Thisabnormalitypresentsthecombinedsymptomsofthe medianandulnarnerves.6

Areasofthehandinnervatedbythemediannerve

Theareasensitizedbythemediannervecomprisesthepalmar faceofthethreeradialfingersandtheradialhalfofthering fin-ger;andonthedorsalface,thelasttwophalanxesofthefirst threefingersandtheradialhalfofthefourthfinger.Themore proximalthepalmarcutaneousbranchis,abovetheanterior ligament,thebetterthisexplainsthelackofparticipationin the symptomsofthethenarzone. Inrelationtothemotor plane,themediannerveclassicallyinnervatestheopposition muscles(shortabductorofthethumb,opponenspollicis mus-cleandsuperficialbundleoftheshortflexorofthethumb)and thefirsttwolumbricalmuscles.

Berretini’spalmarsensoryanastomosis

Thisanastomosis,whichisfoundin67–92%ofthecases,is situatedbelowthesuperficialpalmararchandisresponsible forthevariationsinthesensitizedareaattheleveloftheulnar edgeofthethirdandfourthfingersandtheradialedgeofthe fifthfinger,betweenthemedianandulnarnerves.10,11_In cer-taincases,thisanastomosisisimmediatelydistaltotheflexor retinaculum.12

RicheandCannieu’smotoranastomosis

Thisanastomosis,whichisobservedveryfrequently(77%to 100%),11_{isresponsibleforthedistributionoftheinnervation} ofthethenarmusclesbetweenthemedianandulnarnerves andtakesonavarietyofforms:

• The most classical form is a communicating branch

betweenthe thenarbranchofthe mediannerveandthe deepbranchoftheulnarnerve.

• Anastomosis atthe level ofthe adductormuscle ofthe

thumb.

• Anastomosis between the thenar branch and the deep

branchoftheulnarnerveatthelevelofthefirstlumbrical muscle.

• Anastomosisbetweenacollateralnerveofthethumband

thedeepbranchoftheulnarnerve.

• It shouldbenoted that theinnervationofthe lumbrical

musclesissuperimposedonthatofthedeepflexorsofthe fingers.

Martin-GrüberandMarinacci’smedianulnaranastomosis intheforearm

Anastomosesofthemediannervetotheulnarnerveinthe forearm were described byMartin and Grüber. Their inci-dencerangesfrom5to40%.13_{Theanastomosiscomesfrom} themediannerveoranteriorinterosseousnerve,oris situ-atedbetweenthe branchesthat innervate thedeep flexors ofthe fingers.14 _{Thisanastomosiscoexists mostfrequently} withananastomosisinthehand13_{andcontainsfibersthat} innervate the deep flexors ofthe fingers and the intrinsic muscles.11_{Thereiscontroversyregardingtheparticipationof} sensoryfibers.Inverseanastomosesfromtheulnarnerveto themediannerveareveryrareandaresituatedinthedistal partoftheforearm.

LeibovicandHastings’anastomoses

TypeI(60%):anastomosisofthemediannervewiththeulnar nervethatcontinuesintothehandduetoinnervationofthe musclesthatarenormallyinnervatedsolelybythe median nerve(Ia)orwithsomemusclesinnervatedbytheulnarnerve (Ib).15

TypeII(35%):anastomosisofthemediannervewiththe ulnar nerve that continuesinto the hand toinnervate the musclesthatarenormallyinnervatedbytheulnarnerve.15

Type III (3%): anastomosis of the ulnar nerve with the mediannervethatcontinuesintothehandduetoinnervation ofthemusclesthatarenormallyinnervatedbythemedian nerve.15

Type IV (1%): anastomosis of the ulnar nerve with the mediannervethatcontinuesintothehandduetoinnervation

of the muscles that are normally innervated by the ulnar nerve.15

Vascularvariations

Persistenceofthearteryofthemediannerve

Thisleftoverfromtheembryonicstageisobservedin1–16% ofthecases.16_{AccordingtoKleinertetal.,}17_whofounditin 3.4%oftheircases,itparticipatedsignificantlyinthe super-ficialpalmararchin0.5%ofthecases.Abifidmediannerve maybefoundtogetherwiththis.Thecomplicationproduced isthrombosis,whichgivesrisetoacuteCTS.

Theulnararteryisinasuperficialposition,underthefascia andabovethemuscle.6

Muscleandtendonvariations

Longpalmarmuscle

There is a variation of the long palmar muscle with an intratunnel tendon, called the deep long palmar muscle, whichisinsertedinthedeepfaceofthepalmar aponeuro-sisandmaygiverisetoconstrictionofthemediannerve.The longpalmarmusclemayalsobeinaninverseposition,with intratunnelmusclebodies,andthisiscalledaninverselong palmarmuscle.11,18

Superficialflexorofthefingers

Extensionofthemusclebodyinthecarpaltunnelisthemost frequent variation: 46% inwomen and 7.8% inmen.19 _An accessorymusclebodyorananastomosiswiththelong pal-marmusclehasbeendescribedinassociationwithCTS.11,16,18

Lumbricalmuscles

Extensionoftheintratunnelinsertionorabnormalinsertion overthesuperficialflexoroftheindexfingermaybeobserved, butitremainsunprovenwhethertheseoccurrencesmightbe responsibleforcompressionofthemediannerve.6,18

Physiopathology

and

etiology

Ultrastructuralnerveanomaliesandclinicalcorrelations

From a physiopathologicalpoint ofview,compressive syn-dromescombinethephenomenaofcompressionandtension. Anatomically,therearetwositesofmediannerve compres-sion:oneattheleveloftheproximallimitofthecarpaltunnel, causedbywristflexionbecauseofchangesinthicknessand stiffnessofthe forearmfasciaand inthe proximalportion oftheflexorretinaculum;andthesecondatthelevelofthe narrowestportion,closetothehamatehook.11

Nerve compression and traction may sequentially cre-ateproblemsrelating tointraneuralblood microcirculation, lesionsatthelevelofthemyelinsheathandataxonallevel, andchangestothesupportingconnectivetissue.Lundborg20 proposedthefollowingclinical–anatomicalclassification:

• Redistributionoffluidstotheupperlimbs,wheninasupine

position;

• Lackofamusclepumpmechanismthatmightcontribute

towarddrainageofinterstitialfluidsinthecarpaltunnel;

• Tendencytokeepthe wrist inaflexedposition, thereby

increasingtheintratunnelpressure;

• Increasedarterialpressure duringthe secondhalfofthe

night.

If the pressure exceeds 40–50mmHg, this will interfere with the venous return of the intraneural microcircula-tion and cause diminished intraneural oxygen supply and venousstasis,withpermeabilityproblemsoriginating from theendoneurialedema.Anincreaseinpressureof30mmHg for2hleadstoprogressiveweakeningoftheslowand fast axonal transportation. This is corrected when the patient repositionshiswristandmakesfingermovements,thereby enablingdrainageoftheedema.Afterthecompressionhas beenrelieved,thereisarapidimprovementinthesymptoms. Intermediarystage–Thesymptomsarebothnocturnaland diurnal.Abnormalitiesofthemicrocirculationareconstantly present,withepineuralandintrafascicularinterstitialedema, whichcausesincreasedendoneurialfluidpressure.This inter-stitialedemacausesabsenceofcellflowandthickeningofthe connectiveenvelope,notablyinrelationtotheepineurium. DestructionofthemyelinsheathandnodesofRanvieralso occurs,basedonsaltatoryconductionofinflowstothesurface ofthemyelinatednervefibers.Afterthecompressionhasbeen relieved,rapidimprovementofthesymptomsoccursthrough reestablishment ofthe intraneuralmicrocirculation. Unlike therestoration,repairofthe myelinsheath requiresweeks tomonthsandcausesintermittentsymptomsandpersistent electrophysiologicalabnormalities.

Advancedstage–Symptomsareconstantlypresent, espe-ciallysignsofsensoryormotordeficit,translatedasdisruption ofagreaterorlessernumberofaxons(axonotmesis). Walle-riandegenerationexistsatthelevelofthedisruptedaxons. Theconnectiveenvelopesformthe siteforreactivefibrous thickening.Afterreleaseofthenerve,therecoverydepends onnerveregeneration,whichtakesseveralmonthsandmay beincomplete.Thesignificanceoftherecoverywilldepend onthepatient’spotentialforaxonalregeneration,particularly withregardtoage,theexistenceofpolyneuropathyandthe severityofthecompression.

Inreality,evenwith compressionofall the nervefibers withinthesame nerve, theywillnotbeatthe same stage ofinjury.Ithasbeendemonstratedthattheperipheralnerve fibersintheregionofthenervetrunkareaffectedbeforethe morecentralfibersand,likewise,themyelinatedfibersin rela-tiontothesmallerfibersandthesensoryfibersinrelationto themotorfibers.

InchronicCTScases,worseningmayoccuroveraperiod ofmonthsoryears.

Associatedpathologicalconditions

Polyneuropathy

Allformsofpolyneuropathy,includingthoserelatingto dia-betesmellitus,promoteCTSwithstructuralandfunctional

alterationsofthemediannerve,whichmakesthenervemore sensitivetoallcompressivephenomena.21

Hereditaryneuropathywithhypersensitivitytopressureis ahereditarysensory-motorformofneuropathythatisfocal andrecurrent.Thefirstsymptomsonlyrarelyappearbefore the age of 20 years. It is characterized by occurrences of criseswithparalysisandparesthesiainwell-definedareasof thenervetrunk.Thesecrises,whicharegenerallysecondary to mild trauma or prolonged compression, often regress. Recurrence is frequent. Paralysis may become definitively established.Attheelectrophysiologicallevel, thiscondition ischaracterizedbymyelinopathywithstretchingofthedistal motorlatency.Biopsiesofthenerveshowzonesoffocal thick-eningofmyelinintheformofsausages(tomacula).Hereditary neuropathywithhypersensitivitytopressureisinheritedas a dominant autosomal geneticlesion in80% of the cases, throughadeletionofchromosome17.Thetreatmentis symp-tomatic.

Nervecompressionsyndrome:“doubleconstriction syndrome”

Theconceptofdoublecompressionofthenerveisattributed toUptonandMacComas22_{andisbasedonthefactthat} prox-imal compression on the path of a nerve makes it more susceptible than ifthe compression waslocated more dis-tally, because of cumulative effects on anterogradeaxonal transportation. Likewise, this can occur in cases of distal compression,duetoalterationsoftheretrogradeaxonal trans-portation(“inverteddoubleconstrictionsyndrome”).Thismay occur in practice in cases of association between proxi-mal compression of the nerve route at the vertebral level (or thoracicoutletsyndrome)and distalCTS. Careful clini-calexamination,aidedbyanelectrophysiologicalstudy,will determinewherethecompressionsiteis(proximalordistal), i.e.themainagentresponsibleforthesymptoms,thus guid-ingthetreatment.Treatmentappliedtothemaincompression siteisgenerallysufficientforsuchpatients.Compressionof the nerve layershould beborne inmind ifthe results are incompleteor thereistherapeuticfailureinthemedicalor surgicaltreatment.

Etiologies

Inthegreatmajorityofcases,CTSiscalledidiopathic. Sec-ondaryCTSmayberelatedtoabnormalitiesofthecontaineror content.Furthermore,dynamicCTSisfrequentlyfoundunder pathologicalconditionsrelatingtomanualwork.

Idiopathiccarpaltunnelsyndrome

themostimportantpredisposingfactors.Repetitivemanual activitiesandexposuretovibrationsandcoldtemperatures weretheleastimportant.Otherfactorsinvolvedwereobesity andsmoking.

Secondarycarpaltunnelsyndrome

Abnormalitiesofthecontainer

Anyconditionthatmodifiesthewallsofthecarpaltunnelmay causecompressionofthemediannerve.

• Abnormalitiesoftheshapeorpositionofthecarpalbones:

dislocationorsubluxationofthecarpus;28,29

• Abnormalities ofthe shapeofthedistalextremityofthe

radius:fractures(translationofmorethan35%)30_orskewed consolidationofthedistalradius;osteosynthesismaterial ontheanteriorfaceoftheradius;31

• Joint abnormalities: wrist arthrosis,32 inflammatory

arthritis33 _{(due to synovial hypertrophy, bone} deforma-tion and/or carpal shortening), infectious arthritis,34,35 rhizarthrosis36_{orvillonodularsynovitis;}37

• Acromegaly.38

Abnormalitiesofcontent

• Tenosynovialhypertrophy;

• Inflammatorytenosynovitis:inflammatoryrheumatism,33

lupusandinfection;

• Metabolic tenosynovitis: diabetesmellitus21 (abnormality

of collagen turnover), primary or secondary amyloid-osis (chronic hemodialysis with deposition of beta-2-microglobulin),39_gout40_{andchondrocalcinosis;}41

• Abnormalitiesoffluiddistribution:pregnancy,42,43in0.34%

to 25% of the cases, especially in the third trimester, with frequent signs of deficit in 37–85% of the cases; hypothyroidism;44 _{and chronic kidney failure} (arteriove-nousfistula).39

• Abnormal or supernumerary muscle: deep palmar

muscle,45 _{intratunnel position of the muscle body of} thesuperficialflexor46_{orproximalextensionofthemuscle} bodyofthelumbricalmuscles;47

• Persistentarterialhypertrophyofthemediannerve;48

• Intratunneltumor:lipoma,synovialcyst,synovialsarcoma

or neural tumor (schwannoma, neurofibroma or lipofi-broma);

• Hematoma: hemophilia,49 anticoagulant accident50 or

trauma;51

• Obesity.52

Dynamiccarpaltunnelsyndrome

Thepressureinsidethecarpaltunnelincreasesduringwrist extension and flexion.53 _{Repetitive extension and flexion} movements of the wrist, along with flexion of the fingers andsupinationoftheforearm,havebeenimplicatedinthis increase.54_{Incursionsofmusclebodiesfromthesuperficial} anddeepflexorsofthefingers,whenthewristandfingersare extended,havebeen foundin50%ofthe cases.55_This par-ticularmovementcanbeseeninoccupationalpathological conditions.56

CTSandworkingoncomputers

NoincreaseintheprevalenceofCTSincasesofworkingon computersformorethan15hperweekhasbeenobserved. A tendency towardincreasedprevalencehas been demon-stratedincasesofworkingoncomputersformorethan20h perweek.57

Exposuretovibration

Exposure to vibration is one of the lesser predisposing factors.27,54 _{The ultrastructural consequences comprise} microcirculatory compression problems and intraneural edemafollowinginjuryofthemyelinandaxons.

Acutecarpaltunnelsyndrome

Etiologies:

• Trauma:displacementduetofracturingofthedistalradius

ordislocationofthewrist;

• Infection;

• Hemorrhageduetooverdoseofanticoagulantorincasesof

hemophilia;

• High-pressureinjection;

• Acutethrombosisofthearteryofthemediannerve;

• Burns.

Diagnosis

Theclinicalapproachtowardpatientswithacroparesthesiaof thehandconsistsoffivestages:

• Discussthe diagnosis from the consultation office,

chal-lenge tests, analyseson possibleassociated pathological conditionsanddifferentialdiagnosis;

• Determinetheetiology;

• Evaluatetheseverityofcompressionthrough

discrimina-tive sensitivity analysis on the Weber test and analysis onthe strengthofthethenar musclesinnervatedbythe mediannerve;

• Judge whether it is appropriate toperform

complemen-tary examinations, starting with electroneuromyography (ENMG);

• Proposetreatmentadaptedtotheseverityofthecondition,

etiology,locationandactivitycontext.

Itshouldbenotedfirstofallthatthereisnogoldstandard forapositivediagnosisofCTS.

Challengetests

Themediannerveisaccessibleinfrontofthewristflexion creaseandbehindthelongpalmartendonorinthemiddleof thewrist.

• Tinelsign:thetestispositiveifthepatientperceives

• Phalensign:thetestispositiveif,duringmaximumactive

flexionofthewristfor1min(elbowextended),paresthesia appearsintheareaofthemediannerve.Thetimetakenfor thesymptomstoappear(inseconds)isnoted.The sensitiv-ityisbetween67and83%andthespecificityisbetween47 and100%.58,59

• PaleyandMcMurphytest:60thesignispositiveifmanual

pressureclosetothemediannerve (between1and 2cm proximallytothewristflexioncrease)triggerspainor pares-thesia.Thesensitivityis89%andthespecificityis45%.58

• Compressiontestwithwristflexed:61pressure isapplied

usingtwofingersonthemedianregionofthecarpaltunnel, withthewristflexedat60◦_{,elbowextendedandforearm} supinated.Thetestispositiveifparesthesiaappearsinthe areaofthemediannerve.Tetroetal.61_{foundsensitivityof} 82%andspecificityof99%.

AccordingtoSzabo,theexistenceofnocturnal acropares-thesiaisthemostsensitivesymptom(96%).Thetestwiththe highestsensitivityisdirectcompression(Paleyand McMur-phy) (89%), followed bythe Phalen test, the monofilament test of Semmes-Weinstein (83%) and, lastly, the score of Katz et al.62 _{(76%). The typical form taken by nocturnal} acroparesthesia comprises tingling, numbness,swelling or hypoesthesia,withorwithoutpainreachingatleasttwoof thefirstthreefingers,palmandbackofthehandexcluded.

ThemostspecifictestsarethescoreofKatzetal.62_(76%) andtheTinelsign(71%).Acombinationoffourabnormaltests (compressiontest,monofilamenttest,scoreofKatzet al.62 andnocturnalsymptoms)givesrisetoaprobabilityofaCTS diagnosisof0.86.Ifthesefourtestsarenormal,theprobability thatthepatientmighthaveCTSis0.0068.Itwasconcluded thatENMGisnomorefrequentlyusedindiagnosingCTSin eithermoderateorsevereform.

Appreciatingtheseverity:Lundborg’sanatomoclinical classification

Fromtheanalysisonthetimeswhensymptomsappearand investigationofsignsofneurologicaldeficit,symptomscan be classified into early, intermediate and advanced states. Paresthesiacanoccuratnight,inthemorningorthroughout theday.Forsensitivity,theWebertest,whichanalyzeshow thepulpofthefingersdiscriminatesbetweentwopoints,is verypractical.Startingfrom adistanceof6mm,the sensi-tivityisconsideredtobeabnormal.Atthemotorlevel,this study includedthe thumb opposition strength and investi-gatedthenaramyotrophy.

Electroneuromyography(ENMG)examination

ENMGconsistsofastimulationstageandadetectionstage. Itisbilateral.Thestimulation-detectionstagemakesit pos-sibletostudythesensoryandmotornerveconductionofthe mediannerveandhighlighttheelectiveweakeningin pass-ingthroughthecarpaltunnel.Italsoenablesanalysisonthe amplitudeanddurationofthesensoryandmotorresponses. Thisexplorationiscompletedbymeasurementsofthenerve conductionofthehomolateralulnarnerveandbystudieson thecontralateralside.

Theearliestandmostsensitiveelectricalabnormalityisa decreaseinthesensoryconductionvelocity(possibly identi-fiedthroughthecentimetermeasurementmethod)between the palmofthehand and thefingersand wrist.Amedian transtunnel velocity <45m/s in pathological cases can be accepted,versusnormalvalues≥50m/s.63,64

Thisexaminationisoperator-dependent.Theskin temper-atureandagehaveaninfluenceontheresults.ENMGmay bepositivein0–46%ofasymptomaticsubjectsandnegative in 16–24%ofpatients withaclinical diagnosis of CTS.65–68 Serror69_{evaluatedENMGincasesinwhichthemotordistal} latencyalonewasstudiedandfoundsensitivityof54% but specificity of97.5%.ENMGdoesnotprovidesupplementary evidenceindiagnosingCTSinrelationtotheclinical evalua-tion,whentheclinicaldiagnosisseemsevident.70_Anatomical variationsoftheMartin–GruberandRiche–Cannieutypesmay disturbtheinterpretationoftheENMGanalysisof stimulation-detection.

The working group of the French National Agency for HealthcareAccreditationandEvaluation(ANAES)71_concluded thefollowing:

• ENMGissituatedafterclinicalexamination;

• ENMGisnotindispensablefordiagnosingtypicalforms;

• ENMGisunnecessarybeforecorticoidinfiltration;

• ENMGisrecommendedincasesofdoubt.Itaidsinmaking

differentialdiagnoses;

• ENMGisrecommendedbeforemakingsurgicaldecisions;

• ENMGisrequestedinrecognizingoccupationaldiseases.

Images

WristradiographsandincidenceofCTS

INastudyon300patients(477cases),72_radiographic abnor-malities were found in33% ofthecases, and 18.6% ofthe patients had lesions that could beinvolved inthe appear-anceofCTS.NoneoftheseetiologiesmodifiedCTStreatment. Intwocasesoutofthe477,theabnormalitiesrequired spe-cifictreatment.Itwasconcludedthatsystematicradiographic examinationsmadeinsufficientcontributiontobejustified.

Radiographsofthewrist(face, lateraland carpaltunnel views)areusefulinthefollowingsituations:73

• Toexplaintheclinicalexamination;

• Toexplaintheanamnesis.

Echography

Magneticresonanceimaging(MRI)

MRIisrarelyindicated,butmaybeusefulforetiological diag-nosesinthefollowingsituations:

• Forexaminingsecondarysynovialpathologicalconditions;

• As part of diagnosing CTS in children or young adults,

withthe aimofdetectingintratunnelmuscle abnormali-ties,particularlyincasesofCTSoccurringthroughexertion orintratunneltumors.

Final

remarks

Detailedanatomicalknowledgeisfundamentallyimportant formedicalpractice,giventhatanatomicalvariations,when unknown, may give rise to severe complications in surgi-calprocedures.Clinicalcomprehensionofadiseaseisonly attainedwhenits physiopathologyandetiologyare known; from thisknowledge,possibletreatments canbeanalyzed. Thus,althoughCTSismostlyidiopathic,othercauses need to bedetermined in order to progress with adequate pre-ventionand treatment. Another difficulty inclarifying this syndromeistheabsenceofanygoldstandardfor confirma-tion.Hence,thediagnosis isprimarilyclinicaland mostof theteststhatcanbeappliedforevaluatingitsseverityvary insensitivityand specificity.Nonetheless, suchtestsare of greatvalueforrulingout otherpossiblepathological condi-tions.

Conflicts

of

interest

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