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MedialSphenoidWingMeningiomaLastUpdated:March11,2018
Approximately~15-20%ofallmeningiomasarisefromthesphenoidwing,withabouthalfofthesearisingfromthemedialportionofthewing.
Medialsphenoidwingmeningiomasareaheterogeneousgroupoftumorsoriginatingfromtheanteriorclinoidandthemedialthirdofthelessersphenoidwing.Thisgroupincludesbothglobularandhyperostoticenplaquetumors(alsocalled“spheno-orbital”meningiomas).Spheno-orbitalmeningiomaswillbediscussedintheLateralSphenoidWingMeningiomachapter.Therearenospecificpathologicorgeneticfeaturesformedialsphenoidwingmeningiomas.Someofthesetumorsarecausedbyionizingradiation.
Surgicalmanagementofmedialsphenoidwingmeningiomasischallengingbecauseofthecloselyassociatedcriticalneurovascularstructuresalongtheparasellarregion.Meningiomascanoriginatefromanypartofthemeningesalongtheclinoidprocessorlessersphenoidwingandgrowmedially,soclinicalpresentationandtechnicaldetailsofsurgicaltreatmentvaryaccordingly.
Sphenoidwingmeningiomascanbedividedintothreemaingroupsbasedonthesiteoftheirorigin:thosearisingfromtheanteriorclinoidandmedialthirdofthesphenoidwing;thosearisingfromthemiddleandlateralsphenoidwing;andenplaquemeningiomasofthesphenoidwing.Inthischapter,Iwilldiscusstechniquesforresectionofglobularmeningiomasoftheanteriorclinoidandmedialportionsof
TheNeurosurgicalAtlas byAaronCohen-Gadol,M.D.
thesphenoidwing.
TheSimpsonscaleremainsthemostpracticalmethodtopredicttheriskofmeningiomarecurrencefollowingresection.
Table1:SimpsonScaleforPredictionofMeningiomaRecurrenceafterSurgery
SimpsonGrade
CompletenessofResection 10yrRecurrence
I Completewithassociatedduraandboneremoval
9%
II Completewithcoagulationofduralattachment
19%
III Completewithoutduralcoagulation 29%
IV Subtotalresection 40%
Classification
Anteriorclinoidmeningiomasarefurtherclassifiedintothreefollowingsubgroupsbasedontheirsiteoforiginalongtheanteriorclinoid.Eachgroupoffersauniquesetoftechnicaldifficultyformicrosurgery,butallthreetypicallyinvolveboththeinternalcarotidartery(ICA)andtheopticapparatusandpotentiallytheoculomotornerve.
AstheICAemergesfromthecavernoussinusinferiorandmedialtotheanteriorclinoidprocess,itpassesthroughthesubduralspacebetweentheinnerandouter(orupperandlower)duralringswhere1-2mmofitssegmentlacksarachnoidalcovering.MeningiomasarisingaroundthisshortsegmentareclassifiedasGroup1clinoidalmeningiomas.
Figure1:AlateralviewofthecavernoussinusandclinoidalsegmentsoftherightICA.NotetheshortICAsegmentbetweentheupperandlowerduralringswheregroup1clinoidalmeningiomasarisefrom(imagecourtesyofALRhoton,Jr).
AsGroup1tumorsgrow,theytypicallyengulftheICA,growdistallytowardtheICAbifurcationandencasetheproximalmiddlecerebralartery.Becausetheylackaninterveningarachnoidalplane,theyaredenselyadherenttotheadventitiaoftheICA,renderingdissectiondifficultandresultinginlowerratesofsurgicalcure.Group1tumorsalsotypicallyinvolvetheopticnerveandchiasm,butanarachnoidplaneinveststhetumorinthisregion,facilitatingdissection.Group1tumorsfrequentlyinvadethecavernoussinus.
Group2clinoidalmeningiomasarisefromthesuperiorandlateralaspectsoftheanteriorclinoiddura.ThesetumorsoftenengulftheICAastheygrow,butareinvestedbythearachnoidallayersofthecarotidcistern,creatingaccessibledissectionplanes.Additionally,thesetumorsownarachnoidaldissectionplaneswithintheregionoftheopticnerveandchiasm.Cavernoussinusinvasioniscommon.
Thesetumorsarethereforemoreamenabletoaggressivesaferesectionthangroup1tumors.
Group3clinoidalmeningiomasarisefromtheopticforamenandextendintotheopticcanal.Becauseoftheirsiteoforiginandgrowthpattern,group3tumorsbecomesymptomaticearlierthanGroup1and2tumorsandaresubstantiallysmalleratthetimeoftheirdiagnosis.ThesetumorsareinvestedbyarachnoidmembranesintheareaoftheICA,butbecausetheyoriginateawayfromthechiasmaticcistern,thereistypicallynoobviousarachnoidplanebetweenthetumorandtheopticapparatus.Asaresult,surgicalcureislesscommonandtheriskofpostoperativevisualdeclineismorereal.
Thetumorsarisingfromthemiddleportionofthesphenoidwinggrowverylargebeforetheirclinicalpresentation.Theycausesignificantmasseffectonthetemporallobe,andiftheyhaveenoughmedialextension,theycausevisualdisturbance.Smallerlesionswithoutmedialextensioncanbetreatedlikeconvexitymeningiomasafterresectionofthesphenoidwing.
Diagnosis
Themostcommonclinicalpresentationofclinoidalandmedialsphenoidwingmeningiomasareheadachesandvisualdisturbancesuchasblurredvision,visualfielddeficit,oropticatrophy(resultingfromopticapparatuscompression)ordiplopia(resultingfromoculomotornervedistortion).
Tumorsthatinvadethecavernoussinusorsuperiororbitalfissuremaycauseadditionalcranialneuropathies.Largetumorswithmiddlecranialfossaextensioncompressingthetemporallobeorbrainstemresultinseizuresorhemiparesis,respectively.Suchtumorsmayalsocausecognitiveandmemorydeficits,personalitychanges,and
dysphasia.
Tumor-inducedhyperostosisofthesphenoidwingandlateralorbitmaypresentwithproptosis,diplopia,andorbitalpain.Enplaquemeningiomasofthesphenoidwing,alsocalledspheno-orbitalmeningiomas,presentwithsuchocularmanifestations.Thesetumorscaninvadethelateralwallofthecavernoussinus,superiororbitalfissure,floorofthemiddlecranialfossa,andtheextracranialinfratemporalfossa.
Evaluation
Athoroughhistoryandphysicalexamwithparticularattentiontothesymptomsandsignsmentionedabovearerequired.Thin-cutorhigh-resolutionmagneticresonance(MR)imaging,whileincludingfatsuppressionsequencesthroughtheorbits,canassessorbitalinvolvement.
AngiographicevaluationwithMRangiographyorcomputedtomography(CT)angiographydeterminesthemeningioma’srelationshiptothesurroundingvasculatureandtheirdegreeofencasement.However,thesestudiesarerarelynecessaryastheT2-weightedMRimagesareadequateforidentificationofrelevantvasculature.ThebonewindowsonCTangiographyalsodeterminetheextentoftumor-infiltratedhyperostosis.
CatheterangiographycandemonstratestheutilityofpreoperativeembolizationandestimatestherobustnessofcollateralbloodsupplyviaatemporaryballoonocclusiontestiftheICAisencasedandatahighriskofoperativeinjury.However,IadvocatesubtotalremovalofthisbenigntumorinanattempttopreservetheICA.Withtheavailabilityofradiosurgery,theassociatedischemicrisksofamoreaggressiveresectionarenotwarranted.
Idonotbelieveendovascularembolizationisnecessaryformostmeningiomasastheycanbedevascularizedearlyduringexposurebyaggressiveresectionofthesphenoidwingandanteriorclinoidaswellascauterizationoftheinvolveddura.
Athoroughneuro-opthalmologicandendocrinologicassessmentshouldbeperformedaspartofevaluationforallsymptomaticparasellartumors,includingmeningiomas.
Figure2:Medialsphenoidwingmeningiomascanpresent
differentsetoftechnicalchallengesbasedontheirinvolvementofthemedialneurovascularstructuresandtheencasementofthecarotidartery’sperforatingvessels.Amedialsphenoidwingmeningiomawithminimalmedialextensionisshown(upperimages).TheSylvianmiddlecerebralarterybranchesdrapeoverthesuperiorpoleofthetumor.Amoretruemedialsphenoidwing/clinoidalmeningiomawithsignificantmedialextensionandencasementoftheICAisalsoincluded(lowerimages).
Figure3:Agroup3orright-sidedopticforamenmeningiomaisdemonstrated.Thestrategiclocationofthismassleadstoitsearlydiscoveryduetotheassociatedrelativelyrapidcourseofvisualdeterioration.
IndicationsforProcedure
Surgicalresectionisthemainstayoftreatmentformedialsphenoidwingmeningiomas.Stereotacticradiosurgeryisanoptionforasymptomaticsmalltumorswithoutmasseffect,buttheproximityof
highlyradiosensitiveopticchiasmandnervesoftenprecludesitsuse.Observationisalsoareasonabletreatmentplanforsmallincidentaltumors.
Figure4:Coronalandaxialviewsofamiddle/medialsphenoidwingmeningiomawithitstypicalrelationshiptothesurroundingvascularstructuresisdemonstrated.Moreprominentevidenceofopticapparatuscompressionisusuallypresent.
PreoperativeConsiderations
Computedtomography(CT)measurestheextentofbonyinvasionorhyperostosis.ThisinformationisimportantforintraoperativenavigationtoguidegrosstotalresectionoftheinvolvedboneandachievingSimpsonscale1outcome.ThisCTdataalsodeterminesthepotentialneedtoprepareacustomimplantpreoperativelytoreconstructtheareaofresectedbone.
Preoperativeunderstandingofhowthetumorhasdistortedthenormalvasculatureisbeneficialtoavoidcatastrophicvascularinjury.Furthermore,significantvascularencasementattheskullbase
highlightstheneedforplannedsubtotalresectionassmallcaliberICAperforatingarteriesarehighlyvulnerabletoarterialinjuryanddissectionduringtumorexcision.Magneticresonance(MR)imagesprovidethenecessaryinformation.
Alumbardraincandecompressthebrainearlyandallowforanobstructedextraduralclinoidectomytoreleasetheaffectedopticnervebeforethetumorismanipulated.
OperativeAnatomy
Familiaritywiththeparaclinoidvascularandopticapparatusanatomyinadditiontobonymorphologyisimportant.
Figure5:Osteologyoftheanteriorandmiddlecranialbaseisshown.Notethelessersphenoidwing,anteriorclinoidprocessandsurroundingbonystructures(imagecourtesyofALRhoton,Jr).Extraduralclinoidectomycanexposethebaseofthetumorearlyandfacilitateitsdevascularization.Furthermore,extradural
opticnervedecompressionprotectsthenerveearlybeforeanyintraduraltumormanipulationplacesthenerveatriskoftractioninjury.
Figure6:Differentanatomicalviewsoftheanteriorclinoidprocesses,cavernoussinus,andtheirassociatedneurovascularstructures.Theduraisremovedovertherightanteriorclinoidprocess(imagescourtesyofALRhoton,Jr).Mostmeningiomasentertheopticcanalmedialtothenerve
becauseoftheavailabilityofapotentialspacethere.Theoculomotornerveisatriskofinjuryduringclinoidectomyandtumorresection.Medialsphenoidwingmeningiomasmayinfiltratethecavernoussinus;however,thisportionofthetumorshouldbeleftbehindbecauseoftheriskofoperatingwithinthecavernoussinus.
RESECTIONOFMEDIALSPHENOIDWINGMENINGIOMA
Mostmedialsphenoidwingmeningiomascanberesectedthroughtheextendedpterionalcraniotomy.Ifthelesionharborsasignificantsuprasellarcomponent,theorbitozygomaticcraniotomyaffordsanexcellentexposureofthesuprasellarextentofthetumorwithminimalfrontalloberetraction.Tumorswithintraorbitalextensionalsorequireanorbitozygomatic/orbitalosteotomytoexposetheorbit,removethetumorandcorrecttheproptosis.Iusetheextendedpterionalcraniotomywithextraduralclinoidectomyfor>90%ofmedialsphenoidwingmeningiomas.
Theuseofprophylacticperioperativeantiepilepticmedicationsiscontroversial.Iprefertoadministeraloadingdoseofthismedicationatsurgeryandcontinuethemedicationfor7dayspostoperatively.Intheabsenceofanyseizurewithintheperioperativeperiod,thismedicationistaperedoffaround1weekaftersurgery.Ifthepatientsuffersfromanyseizureactivityduringtheperioperativeperiod,thedosemaybeincreasedandcontinuedfor6monthsto1year.
Sincelargertumorsfilltheopticocarotidcisternsandoftenpreventearlycerebrospinalfluiddrainageforbrainrelaxation,Iimplantalumbardrainafterinductionoftheanesthesiatopromotebrainrelaxation.Thisrelaxationisimportantfor1)makingextraduralclinoidectomypossibledespitethetumoroverlyingthemedialsphenoidwing,2)earlyextra-andintraduralaggressivetumordevascularizationanddisconnectionthroughmobilizationofthe
tumorbaseawayfromtheskullbasebeforeitsdebulking.
Forgianttumorswithsignificantedemaandmasseffect,CSFdrainageshouldbeconductedjudiciouslyandgradually,preferablyafterduralopeningtoavoidtranstentorialherniation.OverdrainageofcerebrospinalfluidattheoutsetofsurgerycanalsopotentiallymakedissectionoftheSylvianfissuremoredifficult.
PleaserefertotheExtraduralClinoidectomychapterforfurtherdetailsregardingtheinitialstepsoftheoperationaftercraniotomy.Hyperostoticclinoidprocesscanbechallengingtosafelyremove,astheboneisveryresistanttodrilling.Theopticnerveshouldbeskeletonizedandcarefullyprotectedduringheavydrillingusingampleamountofirrigationfluid.
Hypertrophiedclinoidprocessescandistortthenormalanatomyoftheopticforamen/canal.IusetheassistanceofintraoperativeCTnavigationtolocalizetheforamen/canal.Oncetheclinoidectomyiscomplete,thetumor’sbasealongtheduraoverthesphenoidwingandclinoidprocessisthoroughlydevascularizedextradurally.
Oncetheabovestepsarecomplete,Iopenthedurainacrescentshapeandexposethemeningiomafollowingananteriorsylvianfissuresplit.
INTRADURALPROCEDURE
SlowegressofCSFviathelumbardrainachievesdesirablebrainrelaxation.
Figure7:Exposureofthetumorthroughaleft-sidedextendedpterionalcraniotomyafterextraduralclinoidectomyisshown.Inthiscase,thelargetumorextendedlaterallythroughtheSylvianfissure.Following~40ccofgradualCSFdrainagethroughthelumbardrain,in10ccaliquots,thetumorismobilizedawayfromthelateralsphenoidwingduraanditsmoremedialduralattachmentscoagulated.Thisimportantmaneuvercompletesacriticalstepintheoperationthatleadstothoroughdevascularizationofthetumorandsignificantlyexpeditesthelaterstepsofdissectionbyminimizingtheneedtofrequentlyinterrupttumordissection/removaltoobtainhemostasis.
Figure8:Icontinuetumordevascularizationalongtheanteriorcranialfossawhilekeepingtheapproximatelocationoftheopticnerveinmindtoavoiditsheatinjury.CSFdrainage,Sylvianfissuresplitandstrategicuseofthehandheldsuctiondeviceobviatetheneedforfixedretractors.
Figure9:Enucleationanddebulkingoffirmtumorsisconductedusinganultrasonicaspirator(leftimage)whilesoftertumorsaredebulkedusingbipolarelectrocautery,suctionapparatusandpituitaryrongeurs.Next,Igentlydrawuponthetumorcapsuletocauseitscollapseintothedebulkedcoreofthetumor(rightimage).Itiscriticaltostayinsidethetumorcapsule.Violationofthecapsuleplacesthevulnerableadherentmedialcerebrovascularstructuresatrisk.Vicinityoftheultrasonicaspiratortothevessels,evenwithoutanimmediatecontact,canleadtoirreparablevascularinjury.Thisdeviceshouldbeusedawayfromthecriticalvascularstructures.
Figure10:Atthisjuncture,aftersometumordebulkingtocreatemoreworkingspace,IfurthersplitthedistalaspectofSylvianfissureandidentifytheM2branchesdrapedoverthesuperior
andposteriorpolesofthetumorcapsule.IalsogentlymobilizethetumorcapsuleposteriorlyalongthesphenoidwinginanattempttofindorestimatethelocationoftheICAattheskullbase.TheselattertwomaneuvershelpmeapproximatetherouteoftheMCAbranches,includingtheM1,alongthemedialtumorcapsule-myblindspot.
Figure11:AllMCAvesselsaresharplydissectedoffofthetumorcapsuleandprotectedwiththeuseofcottonoidsoncemobilized(upperimage).Bluntdissectionshouldbeavoided
whenpossible.Mostimportantly,thefeedingarteriesofthetumorandthevitalenpassagevesselsareclearlyidentifiedbeforetheirfateisdecided.Piecesofpapaverine-soakedGelfoamareusedtoperiodicallybathesmallenpassagevesselsforreliefoftheirvasospasm.HighermagnificationintraoperativeviewdemonstratesdissectionoftheM2branchesawayfromthetumor(T)(lowerimage).
Althoughvascularencasementiscommononimaginginthesetumors,mostoften,thearachnoidalplanebetweenthetumorandtheMCAbranchesremainsintactenoughtodissectthevesselfreefromthetumor.Ifthetumoristooadherentforthismaneuver,asmallsheetoftumormustbeleftonthevesselsfortheirprotectionandpreventionofvasospasm.
Figure12:ItisimportanttocarefullymobilizetheanteriorfrontalpoleofthetumorinordertoidentifytheopticnerveandICAattheleveloftheskullbase(upperimage).Followingthecontour
ofsphenoidwingmedially,onecanlocalizetheapproximatelocationoftheopticcanalandtheICA.Inthelowerintraoperativephoto,thefrontalportionofthetumorsisremovedandthelocationoftheopticnerveandcarotidarteryisappreciatedatthetipofthesuctiondevice.Residualcoagulatedtumorispresentalongthetentorium.
Figure13:GentlemobilizationofthemedialcapsuleandsharpdissectionwilluncovertheopticnerveandproximalICA.Thefalciformligamentisincisedtountethertheopticnerve.TheposteriorcommunicatingarterycanbeseenoriginatingfromtheposteriorwallofICA.Thisarteryisanindicatorforthegenerallocationoftheoculomotornerve.Itthetumorisveryadherenttothenervesorvessels,aggressivemanipulationandbluntdissectionmustbeavoidedandasheetoftumorleftbehind.Despitegentlehandlingofthetumoraroundtheoculomotor
nerveandtentorium,mostpatientswillsufferfromtransientthirdandfourthnervepalsiesaftersurgery.Coagulationofthetentoriumaroundthesenervesshouldbeminimizedasmuchasfeasible.
Figure14:Next,Imobilizetheposteriortumorcapsuleawayfromthetemporallobe.Thebaseofthetumoralongtheanteriormiddlefossaisdisconnected.Iprefertosay“thereitis”andbewrong100times,ratherthansay“thereitwas”andberightonce.Neurovascularstructures(morespecifically,theposteriorcommunicatingartery,anteriorchoroidalarteriesandtheoculomotornerve)aredisplacedandcanbefoundinveryunexpectedlocations.Theyareinharm’swayduringaggressivecoagulationinfaceofbleeding.Themedial
arachnoidmembranesoverthebasalcisternsandbrainstemareleftuntouched.
Figure15:Itisessentialtomaintainthearachnoidplanesalongtheentirecircumferenceofthetumorcapsule.Topreventinfarcts,Ipreserveeveryperforatingarteryandminimizeitsmanipulation.Aftergrosstotaltumorresection,theinfiltratedduraalongthemedialsphenoidwingiscauterized.Theneurovascularanatomyattheendofresectionisdemonstrated.
Theopticcanalisthenexploredwithafineball-tipdissector.Iftumorisidentifiedinthislocation,thefalciformligamentisdividedfurther
andtheopticnerveunroofedtoallowintracanaliculartumorextraction.Aggressiveremovalofattachedtumorfromtheopticnervecandisruptthenerve’sbloodsupplyandworsenvisualdeficits.Ifthetumorisnotreadilyseparablefromthenerve,athinsheetoftumormustbeleftonthenerveandtheopticcanalgenerouslyunroofed.Carefulmicrosurgeryaroundthesensitiveoculomotornerveisnecessarytoavoidpermanentcranialnerveparesis.Thecavernoussinusisnotentered.
Inmeningiomasurgery,thefirstoperationisthebestopportunityforsurgicalcure.Therefore,safeaggressivetumorremovalisanappropriateoperativephilosophy.However,ifthetumorisadherenttotheproximalICAandencasesthisportionoftheartery,athinsheetoftumormustbeleftbehind.DissectionofadherenttumorinthisregioninvariablyleadstoinjurytothesmallperforatorsoriginatingfromthemedialwalloftheICA,includingtheposteriorcommunicatingandanteriorchoroidalarteries.
Unfortunately,Ihavesufferedfromtheagonyofthiscomplication.Oneofmypatientssufferedfromaninfarctintheposteriorlimboftheinternalcapsule,causinghemiplegia,afterremovalofagiantmedialsphenoidwingmeningioma.Ithereforeadviseagainstaggressivemanipulationoftheattachedencasingtumoralongtheskullbase.
Figure16:Theopticnerveisdecompressed,buttheadherentfirm/calcifiedtumorencasingthevasculatureisleftbehindtoavoidinjurytotheperforatingarteries(upperimage).Thelowerintraoperativephotodemonstratestheanteriorchoroidalarteryoroneoftheperforators(arrow)encasedbythetumor.This
pieceofthetumorwasnotmanipulated.
AdditionalConsiderations
Dissectionoffibroustumorscanbechallengingandalternativetechniquesarenecessarytomobilizethetumorfromtheopticnerveandthecarotidartery.
Figure17:Thefibrouscapsuleofthismedialsphenoidwingmeningiomathatwasresistanttomobilizationwasremovedby
dividingthetumorintotwofragmentsparalleltothelongaxisoftheICA.Theproximalcarotidarteryandopticnervewerefirstidentifiedattheskullbase(upperphoto).ThetumorwassubsequentlydividedalongtheaxisoftheICA(lowerphoto).Thisdivisionfacilitatedmobilizationandremovaloftheanteriorandposteriorfragmentsofthetumor.
CaseExample
Thispatientpresentedwithright-sidedvisualdeclineandwasdiagnosedwithalargemedialsphenoidwingmeningioma.
Figure18:TheMRimagesofthefirstrowdemonstratethemassandassociatedorbitalroofhyperostosis.Extraduralclinoidectomydecompressedtheopticnerveearly.ThedistalMCAbranchesweredissectedandprotected(secondrow).Asdissectioncontinuedtowardtheskullbase,thetumorwasdividedalongtheICA;thismaneuverfacilitatedtumormobilization(lastrow,leftimage).Theopticnervewasfounddistalinitsforamenandgenerouslyreleasedviaremovaloftheintracanalicularportionofthetumor(lastrow,rightimage).
RESECTIONOFOPTICFORAMENMENINGIOMA
Removalofopticforamenmeningiomasismorestraightforwardasthesetumorsarediscoveredwhentheyaresmall.Theydonotencasethevasculature.However,theycanadheretotheopticapparatus.
Figure19:Arightopticforamen,group3meningioma,isdemonstrated(topimage).Extraduralclinoidectomyunroofstheopticnerve(middlephoto)inpreparationofintraduralopeningofthefalciformligamentanddissectionofthetumorwithintheopticcanal.Theextracanalicularextentofthetumoralongthemedialaspectofthenerveisshownuponduralopeningandelevationofthefrontallobe(lowerimage).
Figure20:AKarlinblade(SymmetricSurgical,Antioch,TN)isusedtocutthefalciformligamentonthesideofthetumortowardthesurgeon(topimage).Theextracanalicularcomponentofthetumorisdissectedawayfromthenerveusingsharptechniquesanddeliveredusingpituitaryrongeurs(bottomphotos).
Figure21:Thesmallperforatingvesselstothechiasmareprotected(topimage)whileanangleddissectormobilizesthemoreintracanalicularportionofthetumoraroundthemedialopticnervewithintheoperativeblindspot(middleimage).Angledstraightdissectorinspectsthedistalpartofthecanaltoensurecompletedecompressionofthecanal;thisfindingisalsoverifiedusingamicrosurgicalmirror(lowerimages).
ClosureandPostoperativeCare
AsmallpieceoftemporalismuscleisusedtoplugtheextraduralspaceatthesiteofclinoidectomytopreventapostoperativeCSFleak.Thelumbardrainisremovedattheendoftheoperation.Postoperativecareissimilartotheoneforpatientswithotherskullbasemeningiomas.
PostoperativevasospasmoftheMCAbranchesisasignificantriskandshouldbetimelyconsideredinthedifferentialdiagnosisofdelayedpostoperativeneurologicdecline.ImagingusingaCTangiogramiswarranted.
PearlsandPitfalls
Athoroughextraduralsphenoidwingresectionand
clinoidectomyleadstoanopportunitytodevascularizethetumoranddecompresstheopticnerveearlyintheprocedure.Earlytumordevascularizationminimizesbleedingduringthedemandingmicrosurgicalstepsoftheoperationandkeepstheoperativefieldpristine.Avoidanceofbipolarcoagulationaroundthemedialneurovascularstructuresislifesaving.Thecriticalneurovascularstructuresarealongthemedialcapsuleandthereforewithintheblindspotofthesurgeon.Centraltumordebulkingandcarefulmobilizationofthetumorcapsulearekeymaneuverstoavoidingcomplications.Allvesselsshouldbetreatedwithutmostrespectandasmallsheetofadherenttumormustbeleftbehind.TheperforatorsalongtheICAattheskullbasearenonforgiving.
DOI:https://doi.org/10.18791/nsatlas.v5.ch05.3
Contributor:AndrewR.Conger,MD,MS
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