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Sacralchordoma.Radiographics2009;29:1525–30,with permission.)
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AnteriorSacralMeningocele
Anteriorsacralmeningocele(ASM)isararedevelopmentallesionwitha slightfemalepredominanceprecipitatedbyacongenitaldefect representinganareaofsacralagenesisthroughwhichtheduralsac herniates.ASMisassociatedwithCurrarinosyndrome,anautosomal dominantconditionthatincludesfindingsofpresacralmass,sacral deformity,andanorectalmalformation.Becauseoftheherniationand compressionofcerebrospinalfluid,patientsfrequentlycomplainof headachesduringdefecation,pressure,lowerbackpain,andurinary difficulty.Diagnosisistypicallymadebyimagingstudiessuchas computedtomographyorMRI,buttheclassicpathognomonicfindingon plainfilmisthe“scimitarsign”associatedwiththeherniationofthedural sac(Fig.23-4).Biopsyofthislesionisabsolutelycontraindicatedbecause itcancausecerebrospinalfluidleakandmeningitis.Surgical managementrequiresligationoftheduraldefect.
FIGURE23-4Bariumenemademonstratingananterior
sacralmeningocele(ASM).ASMina43-year-oldmanwitha historyofheadache,meningitis,andchronicconstipation. Frontalimagefromabariumenemaexaminationshowsa rectalstenosisduetoextrinsiccompression(arrows)witha distendedproximalcolon.Notethesacralbonedefect(the scimitarsign;arrowheads).
(DahanH,ArrivéL,WendumD,DocoulePointeH,DjouhriH, TubianaJM.Retrorectaldevelopmentalcystsinadults: clinicalandradiologic-histopathologicreview,differential diagnosis,andtreatment.Radiographics2001;21:575–84,with permission.)
OtherCongenitalLesions
Otherrareretrorectalmassesincludeadrenalresttumors,whichare exceedinglyuncommonandtypicallyexcisedwithprecautionssimilarto thoseusedwhenremovingpheochromocytomasinotherlocations.Rectal duplicationcystsmayshareacommonwallwiththerectumandcanbe difficulttoexcise.Theycontainsecretorymucosaandafullyformedwall
withsmoothmuscleandaseparatefeedingvessel.Accordingly,theymay fillwithmucousandexertpressureonsurroundingstructurescausing painanddiscomfort.Althoughtheirmalignantpotentialisunknown, excisionofduplicationcystsisrecommendedbecausesurveillanceis difficult,ifnotimpossible.
OsseousandNeurogenicLesions
Osseouslesionsarerare,andcomprise5–10%ofpresacrallesionsand arisefrombone,cartilage,andfibroustissue.Benigntumorsinclude giantcell,osteoblastoma,andaneurysmalbonecysts.Malignantosseous tumorsincludeosteogenicsarcoma,Ewing’ssarcoma,myeloma,and chondrosarcoma.Malignantlesionshaveanoverallpoorprognosisbut completeexcisioneitherforcureifmalignant,ortopreventrecurrenceif benign,isencouraged.Neurogeniclesionsarethesecondmostcommon presacrallesionaftercongenitallesions.Theyarisefromperipheral nervesandthemajorityofthemarebenign,whichinclude neurofibromas,schwannomas,andganglioneuromas.Malignantlesions includeneuroblastomaandavarietyofperipheralnervesheathtumors. Aswithallpresacraltumors,completeexcisionistheruleanddiagnosis isoftenmadelatertoavoidtheriskofinfectionandperforationofthe masswithtumorseedingthatmaycomplicatebiopsyorfineneedle aspiration.
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InflammatoryorMiscellaneousTumors
Miscellaneoustumorsaccountfor10–25%ofallpresacraltumorsand includelipoma,fibroma,leiomyoma,hemangioma,endothelioma, desmoid(locallyaggressive),liposarcoma,fibrosarcoma,malignant histiocytoma,leiomyosarcomas,hemangiopericytoma,metastatic adenocarcinoma,andinflammatorytumors.Inflammatorylesions typicallyaffecttherectrorectalspaceasaresultofaninfectiousprocess adjacenttothearea.Pain,fever,drainage,historyofanalfistula,prior surgery,orCrohn’sdiseaseshouldraisesuspicionofaninfectionor inflammation.Tuberculosiscanrarelypresentasadrainingpresacral sinuswithinfectedbone(Pott’sdisease).Treatmentoftheseprocessesis directedattheunderlyingcause.
PREOPERATIVEPLANNING
Presacraltumorsareusuallyfoundincidentallyunlessinfectionor malignanttransformationdevelops.Adiagnosticevaluationfora presacralsourceshouldbepromptedbyahighindexofsuspicionanda multitudeofvaryingsymptoms:pelvicpressure,pain,neuropraxia,fever, headache,largebowelobstruction,recurrentpilonidalsinuses,or abnormalgait.Adigitalrectalexamination(DRE)willnearlyalways identifymostlow-lyinglesionssuchasdermoids.Thegoalsofimaging foranypresacralmasslesionaredelineationofanatomy,characterization ofthelesion,andassessmentoftheadjacenttissueinvolvement. Computedtomographywithandwithoutrectalandintravenouscontrast isveryusefulatdelineatingcysticfromsolidmasses.However,themost sensitiveandspecifictestfordiagnosisisMRIimagingandisimperative inthepreoperativeplanningprocess.Manypresacraltumorshavevery characteristicfindingsonMRIthatmakeidentificationpossibleinthe absenceoftissuediagnosis.MRIcandelineatesoft-tissueplanes identifyingpreciseareasofinvasiontherebyenablingsurgicalplanning. Specifically,theextentofneurologic,vascular,rectal,andbonyinvasion canbeadequatelyandaccuratelyassessed.Forpatientswithsacral meningocele,specificidentificationoftheleveloftheconnectionbetween thecystandthethecalsaccanbemade.Preoperativecounselingand surgicalteamschedulingcanproceedonthisbasis.Finally,adirect examinationoftherectalmucosashouldbecompletedtoexclude fistulizingorinvasivelesions.Colonoscopy,flexiblesigmoidoscopy,or proctoscopyservethispurposeandcanhelpbettercharacterizethe natureofthelesionpriortoamajorprocedure.
Theroleofpreoperativebiopsyforpresacraltumorshasbeen controversial.Historically,theroleofbiopsyorfineneedleaspiration (FNA)fordiagnosisoftheselesionswasdiscouragedbecauseofthe potentialforinfectionandtumorseeding.Biopsiesofpurelycysticlesions areunnecessaryandshouldbeavoidedaswellasbiopsyofanterior meningoceles,whichcarrya30%mortalityratefrommeningitisandis absolutelycontraindicated.However,inthelast10years,advancesin imagingmodalitiesandimprovedknowledgeoftumorbiologyand neoadjuvanttherapyhasledtoreevaluationoftheroleofpreoperative biopsyinsolid,heterogeneoustumors.Recentstudiesshowthat preoperativebiopsyissafe,includingthatofMessicketal.,who demonstratednorecurrencein24patientswhounderwentadiagnostic biopsyforapresacraltumor.Mercheaetal.performed76biopsieson solidpresacraltumorsanddemonstratedasensitivityof96%anda specificityof100%,concludingthatpreoperativepercutaneousbiopsyis
essentialintheinvestigationofsolidpresacraltumorstoguide management.Forexample,lymphoma,gastrointestinalstromaltumors (GISTs),Ewing’ssarcoma,andosteogenicsarcomatumorsmayall benefitfromcytoreductionwithappropriateneoadjuvanttherapy. Additionalprognosticcharacteristicsmayalsobeobtainedwith preoperativebiopsythatmayaltersurgicalplanningandalertthe surgeontothepossibleneedofenlistingothersurgicalspecialists. Despitetheincreasingfrequencyofpreoperativebiopsies,proper guidelinesshouldbeadheredtoas,describedbyDozoisetal.:
hematomas.
shouldbehadwiththesurgeontoensuretheneedletractisremoved duringafuturesurgicalresection.
becausetheneedletractcannotusuallyberemovedenbloc.
ADVANCESINNEOADJUVANTTHERAPY
Neoadjuvantchemotherapycanbeessentialtothetreatmentofpresacral tumorssuchasEwing’ssarcomaandosteogenicsarcoma.Tyrosine kinaseinhibitorshavealsobeenshowntobeeffectiveinimproving disease-freesurvivalinchordomasandGISTs.Inaddition,transcatheter arterialembolizationhasbeenperformedasanadjuncttoresectionfor large,locallyadvancedsacralchordomas.Theroleofradiotherapyisless clearlydefinedbecausemostofthesepresacraltumorsareradio­resistant.However,novelapproachessuchascarbonionradiotherapy (CIRT)andprotonbeamradiationarestillbeinginvestigatedandhave beenshowntohavesomepotentialtherapeuticeffects.These neoadjuvantmodalitiesarebeyondthescopeofthischapter,but nonethelesshighlighttheimportanceofincorporatingamultidisciplinary approachwithinterventionalradiologyandmedicalandradiation oncologyinadditiontoothersurgicalsubspecialties(neurosurgery, gynecology,urology,andorthopedics)asrequiredbythetumortypeand proximitytoadjacentstructures.
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Surgery
Operativeapproachestopresacralmassesarepredicatedonseveralkey factors:locationofthemass,involvementofadjacentstructures, malignantpotential,andpatientperformancestatus.Preoperative planningbeginswithappropriateimaging,whichestablishesthelocation, size,andinvolvementofadjacentstructures.Preoperativeimagingalone oracarefullyconsideredbiopsyprovidescluesastothemalignant potentialofpresacraltumorsandpossibleneoadjuvantstrategies. Tumorswithminimalmalignantpotentialrequireradicalresectionwith organsparing,whereasmalignanttumorsmayrequireenblocresection ofadjacentstructurestodecreaselocalrecurrence.Preoperativeimaging alsoguidestheneedforotherapproachesandnecessitatesthe involvementofothersurgicalspecialistsifnecessary.Forinstance,an anteriorsacralmenigoceleresectionrequiresateamthatincludesa neurosurgeon.Osseouspresacraltumorsthatinvolvethesacrumorother bonystructuresalmostcertainlymandatetheinvolvementofeitheran orthopedicsurgeonwithexperienceinsacralorvertebralresection,pelvic stabilization,andneurologicorduralsurgery.Finally,apreoperative bowelpreparationthedaybeforethesurgeryisadvised.Functional
compromiseshouldbeplannedforaswell,basedontheexpectedextent ofresection.Preoperativecounselingregardingtheneedforastoma,the needtoself-catheterizetheurinarybladder,orthepossibilityoflower extremitymotordysfunctionshouldbeanticipatedandoffered.
Tumorscanbeapproachedinthreeways:throughananterioror transabdominalapproach;throughaposteriorortranssacralapproach; orthroughacombinationofbothmethods.Generally,tumorsabovethe levelofS3mandateananteriororcombinedapproach.Typically,ifthe upperextentofthelesioncanbepalpatedthroughtheanusonDRE,and thetumordoesnotinvolveadjacentstructures,aposterior-onlyapproach iseffective.
PosteriorApproach
Tumors(dermoid,epidermoid,andteratomas)thatdonotextendabove thelevelofS3andcanbecompletelyappreciatedonDREcanbetypically excisedviaasmalljuxtasacral(longitudinal)incisionextendingfromjust abovetheanalsphincterupward(Fig.23-5).Alternatively,atransverse incisionmaybemadeoverlyingthecoccyx,butexposureofmore proximal,largerlesionsmaybecompromisedwiththisapproach.The dissectioniscarrieddownthroughthelumbosacralfasciatothelevators. Afingerintherectumhelpspushthemobilestructureanddefinethe marginsofthemass.Thecystwallisfrequentlyfoundtopushupthrough thelevatormusculatureandattenuateitsomewhatsothatthemuscle itselfis“draped”overthestructureandcanbedissectedortransectedoff thecystwallatthispoint.Thecystisthenreflectedofftheposteriorrectal wall.Averyapparentplaneisnearlyalwaysobservedbetweenthecyst andtherectum.Transectionoftheanococcygealligamentfacilitatesthe exposureofthecoccyxandifthemassisadherenttothecoccyx,thenthe coccyxissimplyexcisedenblocwiththecyst.Thesurgeonshouldavoid violatingtherectumaswellasthecystwalltominimizethechanceof fistulaandinfection.Completeexcisionofthecystwallisoptimalto avoidrecurrence.Closureofthemass-occupiedspaceinlayerswith absorbablesutureoverasmalldrainbroughtoutlaterallyisadvisable. Skinclosurecanbedonewithasmall-caliberabsorbablemonofilament suture.
FIGURE23-5Schematicrepresentationofajuxtasacral
incisionforapresacraldermoidcystexcision.Theincision (dottedlines)followsthesideofthesacrumfromjustsuperior totheanalsphinctermechanismtothecranialextentofthe retrorectalcyst.Theincisionshouldbeonthesideofthe sacrumthatthecystmostcloselyapproximates.
p.176
p.177
AnteriorApproach
IfthedistalextentofthepresacraltumorresidesabovethelevelofS3– S4,theanteriortransabdominalapproachshouldbeutilized(Fig.23-6). Althoughalowermidlinelaparotomyhasbeenthegoldstandard, laparoscopicandrobotictechniqueshaverecentlybeendescribedasa safeandefficaciousalternativeinthehandsofexperts.Regardlessofthe technique,themesorectumiscircumferentiallymobilizedoffthe
presacralmass.Thelesioncanthenbemeticulouslydissectedoffthe presacralfascia,takingcaretoidentifythearterialblood(ifany)soasnot toinadvertentlyligatethemiddlesacralartery.Malignantorrectal duplicationcystsinvadingtherectummayrequireenblocresectionwith acolorectalorcoloanaldouble-stapledorhand-sewnanastomosis. Lesionsinvadingthesacrumorfromtheduralspacemayrequirea combinedabdominoperinealapproachwithenblocsacralresection.
FIGURE23-6Highlesionsorthoseinvolvingresectionof
intra-abdominalorgansarebetterresectedviaananterioror combinedapproach.
(ZhangHY,ThangtranganI,BalabhadraRS,etal.Surgical techniquesfortotalsacrectomyandspinopelvic reconstruction.NeurosurgFocus2003;15(2):E5,with permission.)
CombinedApproach
LargertumorsextendingabovethelevelofS3–S4orinvolvingstructures suchasduraorbonealmostalwaysrequireacombined
abdominoperinealresection.Thecombinedapproachhastheadvantage ofallowingagoodvisualizationofstructuressuchasuretersandnerves andanadequatecontrolofvesselsduringtheresection.Forinvasive tumorssuchaschordomasthatrequiresacralresectionatorabovethe levelofS3,severaltechnicalconsiderationsmustbemade.Positioning canbechallengingandvarioustechniquesforpositioninghavebeen describedforthisapproach,withthemostcommonpositioning commonlyreferredtoasa“sloppylateralposition”soastoallowboth teamstoworksimultaneously.Dependingonthetumorinvolvementof additionalstructures,theresectionmayalsobeginwiththepatientin highlithotomyposition,andcanbestartedwiththemobilizationofthe sigmoidcolonandrectumwithclearidentificationofuretersbilaterally. Ifpossible,theplanebetweentherectumandthepresacraltumoris enteredanddistallyextendedtothemasstowardthehealthydistalrectal mucosaortotheanorectaljunction.Ifthetumorappearstopenetratethe rectum,thenitisobligatorytoremovetherectumenblocandperforman end-to-endanastomosiswithorwithoutadivertingloopileostomyifa verydistalrectalcuffcanbesafelyspared.Enblocresectionsmayalso involvetheremovalofthesacrumaswellassacralnerveroots.Atleast oneS3nerverootshouldbepreservedtoenablefecalandurinary continence.Ifthisisnotpossible,thenacolostomyshouldbeconsidered. Ifanenblocresectionand/orpelvicexenterationare/isperformed,then theperinealdefectshouldideallybeclosedwithavascularizedmuscle flap(Fig.23-7).Duringtheabdominalportionofthesurgery,bloodloss canbeminimizedbyligatingthemiddlerectalandsacralvesselsand bothinternaliliacarteriesandveins,althoughsomemuscleflapsmay relyonthearterialbloodsupplyofthedistalbranchesoftheinternaliliac artery.Ifbetterexposureisneededthanthelateraldecubituspositioncan provide,maturationofthestomaandclosureoftheabdomencanbe done,andthepatientcanbetransitionedintothepronejackknife positionforthecompletionofthepartialortotalsacrectomy.Inthiscase, theentirespecimenistakenenblocwiththesacrumfromtheposterior positionwhereexposureandvisualizationareoptimized(Figs.23-8and
23-9).Anticipationofclosureofthelargesacraldefectwithsoft-tissue
flaps,eitherlocal(gluteal)orfromtheabdomen(rectus)orlatissimus dorsiisanimportantpartofpreoperativeplanning(Figs.23-10and23-
11).Becauseglutealflapsareoftenusedforreconstruction,someauthors
advocatepreservationoftheinternaliliacvesselsifpossibletopreserve bloodsupplytothesetissues.Alternatively,ifthevesselsshouldbe
made.
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