Download Medial Sphenoid Wing Meningioma

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-
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SimpsonD."Therecurrenceofintracranialmeningiomasafter
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SimonM,SchrammJ.Lateralandmiddlesphenoidwing
meningiomas,inDeMonteF,McDermottM,Al-MeftyO(eds):
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Surgicalstrategiesforgiantmedialsphenoidwingmeningiomas:A...
Lateralorbitotomyforremovalofsphenoidwingmeningiomasinvad...
Modifiedorbitozygomaticcraniotomyforlargemedialsphenoidwin...
Microsurgicalresectionoflargemedialsphenoidwingmeningiomas...
Microsurgicaltreatmentofmedialsphenoidwingmeningioma:Strat...