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TheNeurosurgicalAtlas byAaronCohen-Gadol,M.D. MedialSphenoidWingMeningioma Approximately~15-20%ofallmeningiomasarisefromthesphenoid wing,withabouthalfofthesearisingfromthemedialportionofthe wing. Medialsphenoidwingmeningiomasareaheterogeneousgroupof tumorsoriginatingfromtheanteriorclinoidandthemedialthirdofthe lessersphenoidwing.Thisgroupincludesbothglobularand hyperostoticenplaquetumors(alsocalled“spheno-orbital” meningiomas).Spheno-orbitalmeningiomaswillbediscussedinthe LateralSphenoidWingMeningiomachapter.Therearenospecific pathologicorgeneticfeaturesformedialsphenoidwing meningiomas.Someofthesetumorsarecausedbyionizing radiation. Surgicalmanagementofmedialsphenoidwingmeningiomasis challengingbecauseofthecloselyassociatedcriticalneurovascular structuresalongtheparasellarregion.Meningiomascanoriginate fromanypartofthemeningesalongtheclinoidprocessorlesser sphenoidwingandgrowmedially,soclinicalpresentationand technicaldetailsofsurgicaltreatmentvaryaccordingly. Sphenoidwingmeningiomascanbedividedintothreemaingroups basedonthesiteoftheirorigin:thosearisingfromtheanteriorclinoid andmedialthirdofthesphenoidwing;thosearisingfromthemiddle andlateralsphenoidwing;andenplaquemeningiomasofthe sphenoidwing.Inthischapter,Iwilldiscusstechniquesforresection ofglobularmeningiomasoftheanteriorclinoidandmedialportionsof thesphenoidwing. TheSimpsonscaleremainsthemostpracticalmethodtopredictthe riskofmeningiomarecurrencefollowingresection. Table1:SimpsonScaleforPredictionof MeningiomaRecurrenceafterSurgery Simpson Grade CompletenessofResection 10yr Recurrence I Completewithassociatedduraandbone removal 9% II Completewithcoagulationofdural attachment 19% III Completewithoutduralcoagulation 29% IV Subtotalresection 40% Classification Anteriorclinoidmeningiomasarefurtherclassifiedintothree followingsubgroupsbasedontheirsiteoforiginalongtheanterior clinoid.Eachgroupoffersauniquesetoftechnicaldifficultyfor microsurgery,butallthreetypicallyinvolveboththeinternalcarotid artery(ICA)andtheopticapparatusandpotentiallytheoculomotor nerve. AstheICAemergesfromthecavernoussinusinferiorandmedialto theanteriorclinoidprocess,itpassesthroughthesubduralspace betweentheinnerandouter(orupperandlower)duralringswhere 1-2mmofitssegmentlacksarachnoidalcovering.Meningiomas arisingaroundthisshortsegmentareclassifiedasGroup1clinoidal meningiomas. Figure1:Alateralviewofthecavernoussinusandclinoidal segmentsoftherightICA.NotetheshortICAsegmentbetween theupperandlowerduralringswheregroup1clinoidal meningiomasarisefrom(imagecourtesyofALRhoton,Jr). AsGroup1tumorsgrow,theytypicallyengulftheICA,growdistally towardtheICAbifurcationandencasetheproximalmiddlecerebral artery.Becausetheylackaninterveningarachnoidalplane,theyare denselyadherenttotheadventitiaoftheICA,renderingdissection difficultandresultinginlowerratesofsurgicalcure.Group1tumors alsotypicallyinvolvetheopticnerveandchiasm,butanarachnoid planeinveststhetumorinthisregion,facilitatingdissection.Group1 tumorsfrequentlyinvadethecavernoussinus. Group2clinoidalmeningiomasarisefromthesuperiorandlateral aspectsoftheanteriorclinoiddura.Thesetumorsoftenengulfthe ICAastheygrow,butareinvestedbythearachnoidallayersofthe carotidcistern,creatingaccessibledissectionplanes.Additionally, thesetumorsownarachnoidaldissectionplaneswithintheregionof theopticnerveandchiasm.Cavernoussinusinvasioniscommon. Thesetumorsarethereforemoreamenabletoaggressivesafe resectionthangroup1tumors. Group3clinoidalmeningiomasarisefromtheopticforamenand extendintotheopticcanal.Becauseoftheirsiteoforiginandgrowth pattern,group3tumorsbecomesymptomaticearlierthanGroup1 and2tumorsandaresubstantiallysmalleratthetimeoftheir diagnosis.Thesetumorsareinvestedbyarachnoidmembranesin theareaoftheICA,butbecausetheyoriginateawayfromthe chiasmaticcistern,thereistypicallynoobviousarachnoidplane betweenthetumorandtheopticapparatus.Asaresult,surgicalcure islesscommonandtheriskofpostoperativevisualdeclineismore real. Thetumorsarisingfromthemiddleportionofthesphenoidwinggrow verylargebeforetheirclinicalpresentation.Theycausesignificant masseffectonthetemporallobe,andiftheyhaveenoughmedial extension,theycausevisualdisturbance.Smallerlesionswithout medialextensioncanbetreatedlikeconvexitymeningiomasafter resectionofthesphenoidwing. Diagnosis Themostcommonclinicalpresentationofclinoidalandmedial sphenoidwingmeningiomasareheadachesandvisualdisturbance suchasblurredvision,visualfielddeficit,oropticatrophy(resulting fromopticapparatuscompression)ordiplopia(resultingfrom oculomotornervedistortion). Tumorsthatinvadethecavernoussinusorsuperiororbitalfissure maycauseadditionalcranialneuropathies.Largetumorswithmiddle cranialfossaextensioncompressingthetemporallobeorbrainstem resultinseizuresorhemiparesis,respectively.Suchtumorsmayalso causecognitiveandmemorydeficits,personalitychanges,and dysphasia. Tumor-inducedhyperostosisofthesphenoidwingandlateralorbit maypresentwithproptosis,diplopia,andorbitalpain.Enplaque meningiomasofthesphenoidwing,alsocalledspheno-orbital meningiomas,presentwithsuchocularmanifestations.Thesetumors caninvadethelateralwallofthecavernoussinus,superiororbital fissure,floorofthemiddlecranialfossa,andtheextracranial infratemporalfossa. Evaluation Athoroughhistoryandphysicalexamwithparticularattentiontothe symptomsandsignsmentionedabovearerequired.Thin-cutorhighresolutionmagneticresonance(MR)imaging,whileincludingfat suppressionsequencesthroughtheorbits,canassessorbital involvement. AngiographicevaluationwithMRangiographyorcomputed tomography(CT)angiographydeterminesthemeningioma’s relationshiptothesurroundingvasculatureandtheirdegreeof encasement.However,thesestudiesarerarelynecessaryastheT2weightedMRimagesareadequateforidentificationofrelevant vasculature.ThebonewindowsonCTangiographyalsodetermine theextentoftumor-infiltratedhyperostosis. Catheterangiographycandemonstratestheutilityofpreoperative embolizationandestimatestherobustnessofcollateralbloodsupply viaatemporaryballoonocclusiontestiftheICAisencasedandata highriskofoperativeinjury.However,Iadvocatesubtotalremovalof thisbenigntumorinanattempttopreservetheICA.Withthe availabilityofradiosurgery,theassociatedischemicrisksofamore aggressiveresectionarenotwarranted. Idonotbelieveendovascularembolizationisnecessaryformost meningiomasastheycanbedevascularizedearlyduringexposure byaggressiveresectionofthesphenoidwingandanteriorclinoidas wellascauterizationoftheinvolveddura. Athoroughneuro-opthalmologicandendocrinologicassessment shouldbeperformedaspartofevaluationforallsymptomatic parasellartumors,includingmeningiomas. Figure2:Medialsphenoidwingmeningiomascanpresent differentsetoftechnicalchallengesbasedontheirinvolvement ofthemedialneurovascularstructuresandtheencasementof thecarotidartery’sperforatingvessels.Amedialsphenoidwing meningiomawithminimalmedialextensionisshown(upper images).TheSylvianmiddlecerebralarterybranchesdrape overthesuperiorpoleofthetumor.Amoretruemedial sphenoidwing/clinoidalmeningiomawithsignificantmedial extensionandencasementoftheICAisalsoincluded(lower images). Figure3:Agroup3orright-sidedopticforamenmeningiomais demonstrated.Thestrategiclocationofthismassleadstoits earlydiscoveryduetotheassociatedrelativelyrapidcourseof visualdeterioration. IndicationsforProcedure Surgicalresectionisthemainstayoftreatmentformedialsphenoid wingmeningiomas.Stereotacticradiosurgeryisanoptionfor asymptomaticsmalltumorswithoutmasseffect,buttheproximityof highlyradiosensitiveopticchiasmandnervesoftenprecludesitsuse. Observationisalsoareasonabletreatmentplanforsmallincidental tumors. Figure4:Coronalandaxialviewsofamiddle/medialsphenoid wingmeningiomawithitstypicalrelationshiptothesurrounding vascularstructuresisdemonstrated.Moreprominentevidence ofopticapparatuscompressionisusuallypresent. PreoperativeConsiderations Computedtomography(CT)measurestheextentofbonyinvasionor hyperostosis.Thisinformationisimportantforintraoperative navigationtoguidegrosstotalresectionoftheinvolvedboneand achievingSimpsonscale1outcome.ThisCTdataalsodetermines thepotentialneedtoprepareacustomimplantpreoperativelyto reconstructtheareaofresectedbone. Preoperativeunderstandingofhowthetumorhasdistortedthe normalvasculatureisbeneficialtoavoidcatastrophicvascularinjury. Furthermore,significantvascularencasementattheskullbase highlightstheneedforplannedsubtotalresectionassmallcaliber ICAperforatingarteriesarehighlyvulnerabletoarterialinjuryand dissectionduringtumorexcision.Magneticresonance(MR)images providethenecessaryinformation. Alumbardraincandecompressthebrainearlyandallowforan obstructedextraduralclinoidectomytoreleasetheaffectedoptic nervebeforethetumorismanipulated. OperativeAnatomy Familiaritywiththeparaclinoidvascularandopticapparatusanatomy inadditiontobonymorphologyisimportant. Figure5:Osteologyoftheanteriorandmiddlecranialbaseis shown.Notethelessersphenoidwing,anteriorclinoidprocess andsurroundingbonystructures(imagecourtesyofALRhoton, Jr).Extraduralclinoidectomycanexposethebaseofthetumor earlyandfacilitateitsdevascularization.Furthermore,extradural opticnervedecompressionprotectsthenerveearlybeforeany intraduraltumormanipulationplacesthenerveatriskoftraction injury. Figure6:Differentanatomicalviewsoftheanteriorclinoid processes,cavernoussinus,andtheirassociated neurovascularstructures.Theduraisremovedovertheright anteriorclinoidprocess(imagescourtesyofALRhoton,Jr). Mostmeningiomasentertheopticcanalmedialtothenerve becauseoftheavailabilityofapotentialspacethere.The oculomotornerveisatriskofinjuryduringclinoidectomyand tumorresection.Medialsphenoidwingmeningiomasmay infiltratethecavernoussinus;however,thisportionofthetumor shouldbeleftbehindbecauseoftheriskofoperatingwithinthe cavernoussinus. RESECTIONOFMEDIALSPHENOIDWINGMENINGIOMA Mostmedialsphenoidwingmeningiomascanberesectedthrough theextendedpterionalcraniotomy.Ifthelesionharborsasignificant suprasellarcomponent,theorbitozygomaticcraniotomyaffordsan excellentexposureofthesuprasellarextentofthetumorwithminimal frontalloberetraction.Tumorswithintraorbitalextensionalsorequire anorbitozygomatic/orbitalosteotomytoexposetheorbit,removethe tumorandcorrecttheproptosis.Iusetheextendedpterional craniotomywithextraduralclinoidectomyfor>90%ofmedial sphenoidwingmeningiomas. Theuseofprophylacticperioperativeantiepilepticmedicationsis controversial.Iprefertoadministeraloadingdoseofthismedication atsurgeryandcontinuethemedicationfor7dayspostoperatively.In theabsenceofanyseizurewithintheperioperativeperiod,this medicationistaperedoffaround1weekaftersurgery.Ifthepatient suffersfromanyseizureactivityduringtheperioperativeperiod,the dosemaybeincreasedandcontinuedfor6monthsto1year. Sincelargertumorsfilltheopticocarotidcisternsandoftenprevent earlycerebrospinalfluiddrainageforbrainrelaxation,Iimplanta lumbardrainafterinductionoftheanesthesiatopromotebrain relaxation.Thisrelaxationisimportantfor1)makingextradural clinoidectomypossibledespitethetumoroverlyingthemedial sphenoidwing,2)earlyextra-andintraduralaggressivetumor devascularizationanddisconnectionthroughmobilizationofthe tumorbaseawayfromtheskullbasebeforeitsdebulking. Forgianttumorswithsignificantedemaandmasseffect,CSF drainageshouldbeconductedjudiciouslyandgradually,preferably afterduralopeningtoavoidtranstentorialherniation.Overdrainage ofcerebrospinalfluidattheoutsetofsurgerycanalsopotentially makedissectionoftheSylvianfissuremoredifficult. PleaserefertotheExtraduralClinoidectomychapterforfurther detailsregardingtheinitialstepsoftheoperationaftercraniotomy. Hyperostoticclinoidprocesscanbechallengingtosafelyremove,as theboneisveryresistanttodrilling.Theopticnerveshouldbe skeletonizedandcarefullyprotectedduringheavydrillingusing ampleamountofirrigationfluid. Hypertrophiedclinoidprocessescandistortthenormalanatomyof theopticforamen/canal.IusetheassistanceofintraoperativeCT navigationtolocalizetheforamen/canal.Oncetheclinoidectomyis complete,thetumor’sbasealongtheduraoverthesphenoidwing andclinoidprocessisthoroughlydevascularizedextradurally. Oncetheabovestepsarecomplete,Iopenthedurainacrescent shapeandexposethemeningiomafollowingananteriorsylvian fissuresplit. INTRADURALPROCEDURE SlowegressofCSFviathelumbardrainachievesdesirablebrain relaxation. Figure7:Exposureofthetumorthroughaleft-sidedextended pterionalcraniotomyafterextraduralclinoidectomyisshown.In thiscase,thelargetumorextendedlaterallythroughtheSylvian fissure.Following~40ccofgradualCSFdrainagethroughthe lumbardrain,in10ccaliquots,thetumorismobilizedawayfrom thelateralsphenoidwingduraanditsmoremedialdural attachmentscoagulated.Thisimportantmaneuvercompletesa criticalstepintheoperationthatleadstothorough devascularizationofthetumorandsignificantlyexpeditesthe laterstepsofdissectionbyminimizingtheneedtofrequently interrupttumordissection/removaltoobtainhemostasis. Figure8:Icontinuetumordevascularizationalongtheanterior cranialfossawhilekeepingtheapproximatelocationoftheoptic nerveinmindtoavoiditsheatinjury.CSFdrainage,Sylvian fissuresplitandstrategicuseofthehandheldsuctiondevice obviatetheneedforfixedretractors. Figure9:Enucleationanddebulkingoffirmtumorsis conductedusinganultrasonicaspirator(leftimage)whilesofter tumorsaredebulkedusingbipolarelectrocautery,suction apparatusandpituitaryrongeurs.Next,Igentlydrawuponthe tumorcapsuletocauseitscollapseintothedebulkedcoreofthe tumor(rightimage).Itiscriticaltostayinsidethetumorcapsule. Violationofthecapsuleplacesthevulnerableadherentmedial cerebrovascularstructuresatrisk.Vicinityoftheultrasonic aspiratortothevessels,evenwithoutanimmediatecontact,can leadtoirreparablevascularinjury.Thisdeviceshouldbeused awayfromthecriticalvascularstructures. Figure10:Atthisjuncture,aftersometumordebulkingtocreate moreworkingspace,IfurthersplitthedistalaspectofSylvian fissureandidentifytheM2branchesdrapedoverthesuperior andposteriorpolesofthetumorcapsule.Ialsogentlymobilize thetumorcapsuleposteriorlyalongthesphenoidwinginan attempttofindorestimatethelocationoftheICAattheskull base.Theselattertwomaneuvershelpmeapproximatetheroute oftheMCAbranches,includingtheM1,alongthemedialtumor capsule-myblindspot. Figure11:AllMCAvesselsaresharplydissectedoffofthe tumorcapsuleandprotectedwiththeuseofcottonoidsonce mobilized(upperimage).Bluntdissectionshouldbeavoided whenpossible.Mostimportantly,thefeedingarteriesofthe tumorandthevitalenpassagevesselsareclearlyidentified beforetheirfateisdecided.Piecesofpapaverine-soaked Gelfoamareusedtoperiodicallybathesmallenpassagevessels forreliefoftheirvasospasm.Highermagnification intraoperativeviewdemonstratesdissectionoftheM2branches awayfromthetumor(T)(lowerimage). Althoughvascularencasementiscommononimaginginthese tumors,mostoften,thearachnoidalplanebetweenthetumorandthe MCAbranchesremainsintactenoughtodissectthevesselfreefrom thetumor.Ifthetumoristooadherentforthismaneuver,asmall sheetoftumormustbeleftonthevesselsfortheirprotectionand preventionofvasospasm. Figure12:Itisimportanttocarefullymobilizetheanteriorfrontal poleofthetumorinordertoidentifytheopticnerveandICAat theleveloftheskullbase(upperimage).Followingthecontour ofsphenoidwingmedially,onecanlocalizetheapproximate locationoftheopticcanalandtheICA.Inthelower intraoperativephoto,thefrontalportionofthetumorsis removedandthelocationoftheopticnerveandcarotidarteryis appreciatedatthetipofthesuctiondevice.Residualcoagulated tumorispresentalongthetentorium. Figure13:Gentlemobilizationofthemedialcapsuleandsharp dissectionwilluncovertheopticnerveandproximalICA.The falciformligamentisincisedtountethertheopticnerve.The posteriorcommunicatingarterycanbeseenoriginatingfromthe posteriorwallofICA.Thisarteryisanindicatorforthegeneral locationoftheoculomotornerve.Itthetumorisveryadherentto thenervesorvessels,aggressivemanipulationandblunt dissectionmustbeavoidedandasheetoftumorleftbehind. Despitegentlehandlingofthetumoraroundtheoculomotor nerveandtentorium,mostpatientswillsufferfromtransientthird andfourthnervepalsiesaftersurgery.Coagulationofthe tentoriumaroundthesenervesshouldbeminimizedasmuchas feasible. Figure14:Next,Imobilizetheposteriortumorcapsuleaway fromthetemporallobe.Thebaseofthetumoralongtheanterior middlefossaisdisconnected.Iprefertosay“thereitis”andbe wrong100times,ratherthansay“thereitwas”andberight once.Neurovascularstructures(morespecifically,theposterior communicatingartery,anteriorchoroidalarteriesandthe oculomotornerve)aredisplacedandcanbefoundinvery unexpectedlocations.Theyareinharm’swayduring aggressivecoagulationinfaceofbleeding.Themedial arachnoidmembranesoverthebasalcisternsandbrainstemare leftuntouched. Figure15:Itisessentialtomaintainthearachnoidplanesalong theentirecircumferenceofthetumorcapsule.Toprevent infarcts,Ipreserveeveryperforatingarteryandminimizeits manipulation.Aftergrosstotaltumorresection,theinfiltrated duraalongthemedialsphenoidwingiscauterized.The neurovascularanatomyattheendofresectionisdemonstrated. Theopticcanalisthenexploredwithafineball-tipdissector.Iftumor isidentifiedinthislocation,thefalciformligamentisdividedfurther andtheopticnerveunroofedtoallowintracanaliculartumor extraction.Aggressiveremovalofattachedtumorfromtheopticnerve candisruptthenerve’sbloodsupplyandworsenvisualdeficits.Ifthe tumorisnotreadilyseparablefromthenerve,athinsheetoftumor mustbeleftonthenerveandtheopticcanalgenerouslyunroofed. Carefulmicrosurgeryaroundthesensitiveoculomotornerveis necessarytoavoidpermanentcranialnerveparesis.Thecavernous sinusisnotentered. Inmeningiomasurgery,thefirstoperationisthebestopportunityfor surgicalcure.Therefore,safeaggressivetumorremovalisan appropriateoperativephilosophy.However,ifthetumorisadherent totheproximalICAandencasesthisportionoftheartery,athinsheet oftumormustbeleftbehind.Dissectionofadherenttumorinthis regioninvariablyleadstoinjurytothesmallperforatorsoriginating fromthemedialwalloftheICA,includingtheposterior communicatingandanteriorchoroidalarteries. Unfortunately,Ihavesufferedfromtheagonyofthiscomplication. Oneofmypatientssufferedfromaninfarctintheposteriorlimbofthe internalcapsule,causinghemiplegia,afterremovalofagiantmedial sphenoidwingmeningioma.Ithereforeadviseagainstaggressive manipulationoftheattachedencasingtumoralongtheskullbase. Figure16:Theopticnerveisdecompressed,buttheadherent firm/calcifiedtumorencasingthevasculatureisleftbehindto avoidinjurytotheperforatingarteries(upperimage).Thelower intraoperativephotodemonstratestheanteriorchoroidalartery oroneoftheperforators(arrow)encasedbythetumor.This pieceofthetumorwasnotmanipulated. AdditionalConsiderations Dissectionoffibroustumorscanbechallengingandalternative techniquesarenecessarytomobilizethetumorfromtheopticnerve andthecarotidartery. Figure17:Thefibrouscapsuleofthismedialsphenoidwing meningiomathatwasresistanttomobilizationwasremovedby dividingthetumorintotwofragmentsparalleltothelongaxisof theICA.Theproximalcarotidarteryandopticnervewerefirst identifiedattheskullbase(upperphoto).Thetumorwas subsequentlydividedalongtheaxisoftheICA(lowerphoto). Thisdivisionfacilitatedmobilizationandremovaloftheanterior andposteriorfragmentsofthetumor. CaseExample Thispatientpresentedwithright-sidedvisualdeclineandwas diagnosedwithalargemedialsphenoidwingmeningioma. Figure18:TheMRimagesofthefirstrowdemonstratethemass andassociatedorbitalroofhyperostosis.Extradural clinoidectomydecompressedtheopticnerveearly.Thedistal MCAbranchesweredissectedandprotected(secondrow).As dissectioncontinuedtowardtheskullbase,thetumorwas dividedalongtheICA;thismaneuverfacilitatedtumor mobilization(lastrow,leftimage).Theopticnervewasfound distalinitsforamenandgenerouslyreleasedviaremovalofthe intracanalicularportionofthetumor(lastrow,rightimage). RESECTIONOFOPTICFORAMENMENINGIOMA Removalofopticforamenmeningiomasismorestraightforwardas thesetumorsarediscoveredwhentheyaresmall.Theydonot encasethevasculature.However,theycanadheretotheoptic apparatus. Figure19:Arightopticforamen,group3meningioma,is demonstrated(topimage).Extraduralclinoidectomyunroofsthe opticnerve(middlephoto)inpreparationofintraduralopening ofthefalciformligamentanddissectionofthetumorwithinthe opticcanal.Theextracanalicularextentofthetumoralongthe medialaspectofthenerveisshownuponduralopeningand elevationofthefrontallobe(lowerimage). Figure20:AKarlinblade(SymmetricSurgical,Antioch,TN)is usedtocutthefalciformligamentonthesideofthetumor towardthesurgeon(topimage).Theextracanalicular componentofthetumorisdissectedawayfromthenerveusing sharptechniquesanddeliveredusingpituitaryrongeurs (bottomphotos). Figure21:Thesmallperforatingvesselstothechiasmare protected(topimage)whileanangleddissectormobilizesthe moreintracanalicularportionofthetumoraroundthemedial opticnervewithintheoperativeblindspot(middleimage). Angledstraightdissectorinspectsthedistalpartofthecanalto ensurecompletedecompressionofthecanal;thisfindingisalso verifiedusingamicrosurgicalmirror(lowerimages). ClosureandPostoperativeCare Asmallpieceoftemporalismuscleisusedtoplugtheextradural spaceatthesiteofclinoidectomytopreventapostoperativeCSF leak.Thelumbardrainisremovedattheendoftheoperation. Postoperativecareissimilartotheoneforpatientswithotherskull basemeningiomas. PostoperativevasospasmoftheMCAbranchesisasignificantrisk andshouldbetimelyconsideredinthedifferentialdiagnosisof delayedpostoperativeneurologicdecline.ImagingusingaCT angiogramiswarranted. PearlsandPitfalls Athoroughextraduralsphenoidwingresectionand clinoidectomyleadstoanopportunitytodevascularizethe tumoranddecompresstheopticnerveearlyintheprocedure. Earlytumordevascularizationminimizesbleedingduringthe demandingmicrosurgicalstepsoftheoperationandkeepsthe operativefieldpristine.Avoidanceofbipolarcoagulation aroundthemedialneurovascularstructuresislifesaving. Thecriticalneurovascularstructuresarealongthemedial capsuleandthereforewithintheblindspotofthesurgeon. Centraltumordebulkingandcarefulmobilizationofthetumor capsulearekeymaneuverstoavoidingcomplications. Allvesselsshouldbetreatedwithutmostrespectandasmall sheetofadherenttumormustbeleftbehind.Theperforators alongtheICAattheskullbasearenonforgiving. DOI:https://doi.org/10.18791/nsatlas.v5.ch05.3 Contributor:AndrewR.Conger,MD,MS References Al-MeftyO.OperativeAtlasofMeningiomas.Philadelphia:LippincottRaven,1998. ChicoineM,JostS.Surgicalmanagementofmeningiomasofthe sphenoidwingregion:Operativeapproachestomedialand lateralsphenoidwing,spheno-orbital,andcavernoussinus meningiomas,inBenhamB.(ed):NeurosurgicalOperative Atlas:Neuro-oncology,2nded.RollingMeadows,IL:Thieme MedicalPublishersandtheAmericanAssociationof NeurologicalSurgeons,2007,161-169. KrishtA.Clinoidalmeningiomas,inDeMonteF,McDermottM,Al- MeftyO(eds):Al-Mefty’sMeningiomas,2nded,NewYork: ThiemeMedicalPublishers,2011.297-306. SimpsonD."Therecurrenceofintracranialmeningiomasafter surgicaltreatment."JNeurolNeurosurgPsychiatry.1957Feb; 20(1):22-39. SimonM,SchrammJ.Lateralandmiddlesphenoidwing meningiomas,inDeMonteF,McDermottM,Al-MeftyO(eds): Al-Mefty’sMeningiomas,2nded.NewYork:ThiemeMedical Publishers,2011,297-306. TewJM,vanLoverenHR,KellerJT.AtlasofOperative Microneurosurgery,Vol1.Philadelphia:Saunders,1994. TewJM,vanLoverenHR,KellerJT.AtlasofOperative Microneurosurgery,Vol2.Philadelphia:Saunders,2001. 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