Download Use of Endoscopes in Skull Base Surgery

TheNeurosurgicalAtlas byAaronCohen-Gadol,M.D.
UseofEndoscopesinSkullBase
Surgery
BasicsoftheTransnasalEndoscopicApproach
Figure1:Endoscopicilluminationofthecentralskullbasecan
beachievedwithastraightendoscopeplacedwithinonenostril.
Endoscopespermitthevisualizationofmanyskullbase
structuresincluding:sphenoidsinus,plannumsphenoidale,
sella,pituitarygland,cavernoussinus,dorsumsella,suprasellar
region,ethmoidroof,frontalsinus,andcribiformplate.
Figure2:Efficientendoscopictechniqueinvolvesbinarial
endoscopicdissection.Theendoscopeshouldbeheld
superiorlywithinonenostrilbyonesurgeon.Thispermitsa
secondsurgeontomanipulatetwodissectioninstruments,one
withintheipsilateralandcontralateralnares.
Figure3:Themiddleturbinateisremovedunderendoscopic
guidance.Themiddleturbinateshouldbepreservedduringan
endonasalprocedureifpossible,howeverahypertrophic
turbinatewithipsilateralnasalseptaldeviationoften
necessitatesremovaltopermitvisualizationandinstrument
manipulation.Toperformthisremoval,theturbinateshouldbe
injectedwithepinephrineandlidocainetofacilitate
vasoconstrictionandbetransectedatitsrootandremoved.
Figure4:Thesphenoethmoidrecesshousestheostiumofthe
sphenoidsinus.Therecessisboundedmediallybythe
posteriornasalseptumandlaterallybythesuperiorturbinate.
Removetheposteriorthirdofthenasalseptumwithabackbitingrongeur.Asuction-debriderisusedtoremoveexcess
mucosafollowingtheremovaloftheethmoidperpendicular
plate.Theostiumisenlargedmedially(dashedoutline)witha
kerrisonpunch.Theenlargementiscompletedwithdrillingof
thesphenoidrostrumtoitsbasecentrallyandlaterally.
Figure5:Awidesphenoidotomyiscreatedtopermitnecessary
manipulationbytwodissectinginstrumentswithinthefield.
Visualizationoftheplanumsphenoidale,tuberculumsella,sellar
face,middleclivus,andthelateralwallofthesphenoidsinus
adjacenttothecavernoussinus.Beginthebonyresection
superficialtotheanteriorselladura,whichisrepresentedbythe
lowerdashedrectangle.Thebonyexcisionisthenextended
superiorlytoremovethetuberculumsellaandbonecovering
theplanumsphenoidale,opticcanals,andmedialoptic-carotid
recess,whichisrepresentedbytheupperdashedrectangle.
Theremovalcanalsobeextendedinferiorlyandlaterally.
Figure6:Completedendoscopicapproachtothepituitarygland
andopticchiasm
ClivalChordoma
Figure1:Coronalviewofaclivalchordoma.Chordomaswithin
thislocationexertmasseffectonthepituitaryglanddisplacing
itrostrallyandonthebrainstemdisplacingitposteriorly.An
anteriorapproachwillrequireresectionoftumoranteriorand
inferiortotheglandtopermitelevationofthegland.
Figure2:Axialviewofaclivalchordoma.
Figure3:Sagittalviewofaclivalchordoma.
Figure4:Transsphenoidalendoscopicapproachtoasphenoid
sinustumor.Thewidesphenoidotomyallowsforamore
optimalexposureofthetumor,thesuprasellarregion,and
planumsphenoidale.
Figure5:Transsphenoidalendoscopicapproachthroughthe
sellaandplanumtoexposeasellartumor.Thesellarfloorand
facecanberemovedwithkerrisonpunchesandadrill.Bone
excisioncanbeextendedlaterallyoneachsideofthesellato
theanteriorfaceofthecavernoussinus.Duralincisioncanbe
madesuperiorandinferiortotheintercavernoussinus,andthe
sinuscanthenbecoagulatedandremoved.Proximalpituitary
glandandsuprasellarexposurecanbeachievedbywidely
openingtheduraalongthesellaandsuprasellarsurface.Distal
pituitaryglandexposurecanbeachievedbytransectingthe
diaphragmasella.
Figure6:Transsphenoidalendoscopicapproachtoa
retrosellartumor(dashedline).Toachieveretrosellaraccessthe
pituitaryglandmustbeelevatedoutofthesella.Tumor
resectionmayrequireopeningoftheclivalordorsumsella
tumor.Duralinfiltrationisobservedandcomplicatesthe
resectionbutprepontinearachnoidistypicallyspared.
Esthesioneuroblastoma
Figure1:Coronalviewofanesthesioneuroblastoma.Erosionof
thecribiformplateiscommonlyobservedleadingtoextension
intotheanteriorcranialfossaorfrontalsinus.
Figure2:Axialviewofanesthesioneuroblastoma.
Figure3:Sagittalviewofanesthesioneuroblastoma.
Figure4:Duringanendoscopicapproachthetumorcanbe
viewedprojectingfromtheolfactorycleft.Themiddleturbinateis
displacedlaterallytoaccommodatethetumormass.
Figure5:Tumorexposureisachievedbyperformingan
ethmoidectomyandmiddleturbinectomy.Thisadditional
exposureiscriticaltoassistinidentifyingthetumororigin.
Figure6:Piecemealresectionofthetumorisperformedandthe
originisidentifiedfollowingskeletonizationofthecribiformplate
andethmoidroof.
Figure7:Followingidentificationoftheoriginforthe
esthesioneuroblastomaalongtheduraandskullbase,generous
excisionmarginsattheoriginshouldbeachievedandverified
byintraoperativefrozensectionanalysis.
Figure8:Theclosurerequiresaduralrepairattheintraduralsite
ofthetumor.Therepairsubstanceisplacedintradurallyand
extradurally.Thebonydefectresultingfromtheapproach
shouldberepairedwithaseptalbonegraftorprostheticplate.
Theseptalbonegraftorprostheticplateshouldbelargeenough
toprovideoverlapwiththebonymargins(asseeninthe
illustration).Amucosalflapisalsousedtosuperficiallyoverlay
onthebonydefect.Itcanbeacquiredasapedicledflaporfree
graft.Toensurecompetenceoftheclosureanadhesivecanbe
usedtopreventleakageofcerebrospinalfluid.
PituitaryMicroadenomaandMacroadenoma
Figure1:Coronalviewofapituitarymicroadenoma.The
adenomaismostcommonlypresentwithintheinferiorextentof
thecentralportionofthepituitarygland.Theadenomaby
definitionislessthan1cmindiameter,mostcommonly
measuresapproximately5mmindiameter.Despitethesmallsize
oftheadenoma,itisnecessarytowidelyremovethesphenoid
bonetoallowforinstrumentmanipulationandefficient
resection.
Figure2:Axialviewofapituitarymicroadenoma.
Figure3:Sagittalviewofapituitarymicroadenoma.
Figure4:Followingthestandardendoscoptictransphenoidal
approach,thesellarfloorshouldberemovedtopermita
durotomyinarectangularpattern(dashedline).Bipolarforceps
canbeusedtocoagulatethecornersoftherectangular
durotomytopreventopeningbetweenthetwolayersand
formationofatracttothecavernoussinus.Thedurotomycan
beextendedbycuttingoutfromthecornersoftheinitial
rectanglardurotomy(dashedline).
Figure5:Followingtheextensionofthedurotomy,theanterior
portionofthepituitaryglandcanbevisualized.Thepituitary
glandcanbegentlydisplacedfromitslocationwithinthesellato
permitinspectionofthecircumferentialduralinterface.Incision
intotheglandmaybenecessarytoretrieveasmallcentrally
locatedmicroadenoma(dashedline).
Figure6:Locatingamicroadenomawithinthepituitary
parenchymacanbechallenging.Useofcolorandtexture
distinctioncanbeusefulindistinguishingadenomafromnative
tissue.Anadenomawillhaveasofttextureversusthemorefirm
surroundingparenchyma.Theadenomawillbetan-grayto
purpleincolorversustheorangesurroundingparenchyma.
Figure7:Pituitarymicroadenomascanpossesssurrounding
extensionswithintheadjacentcompressedanteriorpituitary
tissue,termedthepseudocapsule.Duringtheresectionofa
microadenoma,thepseudocapsuleshouldalsoberemovedto
betterprovideanendocrinologiccureandpreventadenoma
recurrence.Removalofthissmallnativepituitarytissuedoes
notimpairanteriorlobesecretoryfunction.
Figure8:Followingcompleteresectionofthepituitary
microadenomaandpseudocapsule,theresectioncavityis
examinedforpersistentbleedingordrainageofcerebrospinal
fluid.Closureofthesellarfloorshouldbeginwithplacementof
anabsorbablepolyethyleneglycolblockeitherintradurallyor
extradurallywithsufficientoverhang(dashedlines)overthe
drilledmarginofthesellarfloortopreventherniationintothe
sphenoidsinus.Thisblockisthencoveredwithanadhesive
andfreemucosalgraft.Thismultilayeredclosuredecreasesthe
riskofcerebrospinalfluidleakage.Sphenoidsinuspackingwith
adiposetissueisnotnecessaryforasuccessfulclosure.
Figure9:Coronalviewofamacroadenomaexpandingthesella
inferiorlyandlaterally.Theselesionscanalsodemonstrate
cavernoussinusextensionandmasseffectontheopticchiasm
orhypophysealstalk.Thetranssphenoidalapproachshouldbe
consideredfordomeshapedlesionswithsellarandmidline
suprasellarinvolvement.Lateralextensionandirregularityofthe
superiorsurfaceadjacenttotheinternalcarotidarteryare
contraindicationstothetranssphenoidalapproach.
Figure10:Axialviewofapituitarymacroadenoma.
Figure11:Sagittalviewofapituitarymacroadenoma.
Figure12:Thetranssphenoidalapproachtomacroadenomasis
similartotheapproachformicroadenomasexcept
macroadenomasrequiremoreextensiveremovalofthe
sphenoidtofacilitatesurgicalexposure.Thesuperior
intercavernousandcavernoussinuscanbereflectedtofurther
enhancevisualization.Theresectionofamacroadenomabegins
withcentraldebulkingusingaringcurettageorsuction,and
subsequentcollapseoftheperipheralmassintotheresection
cavity.
Figure13:Tumorresectionproceedswithremovalofthe
macroadenomaalongthesellarfloorandonthelateral
extentthatborderthecavernoussinus.Thelateralextentofthe
tumorcanusuallyberemovedwithoutopeningthecavernous
sinus.
Figure14:Thesuprasellarportionofthetumorwilldropcaudally
whentheadenomawithinthesellahasbeenremoved.
Identificationofthenativepituitaryglandiscommonlyobserved
atthisstageduetoacommonsuperolateraldisplacementofthe
glandinthepresenceofamacroadenoma.Aneasilyentered
planebetweenthetumorandthenativeglandpermitstheir
separation.Ifduringtheresection,foldsofglandand
arachnoidareretainedwithintheperiphery,thisisasignof
retainedtumorfragments.
Meningoencephalocele
Figure1:Coronalviewofananteriorfossaencephalocele.
Anteriorskullbaseencephalocelesormeningocelescanbe
observedbyinstrumentationofthenose.Optimallythe
endoscopeshouldbeangled30-to45-degrees.
Figure2:Axialviewofananteriorfossaencephalocele.
Figure3:Sagittalviewofananteriorfossaencephalocele.
Figure4:Initiallyduringtheendonasalapproachtheleftmiddle
turbinateisinview.Adjacentstructuresmustberemovedto
allowfortheendonasalapproachtoan
encephaloceleextendingfromtheethmoidsinus(deepto
dashedline).Thesestructuresincludetheuncinateprocess,
ethmoidbulla,andlateralnasalwall.
Figure5:Themiddleturbinateispreservedandretracted
mediallytopermitdeeperdissection.Anethmoidectomyand
excisionoftheuncinateprocessfacilitateexposureofthe
encephalocele.
Figure6:Theencephaloceleshouldbeinspected
circumferentiallytoidentifythelocationoftheskullbasedefect.
Thebonymarginsoftheskullbasedefectneedtobeexposed
bycautiouslyremovingthemucosaandskeletonizingthe
ethmoidmargins.
Figure7:Bipolarcauterizationisusedtoshrinkthe
encephaloceleuntiltheremnantcanbereducedinto
theadjacentskullbasedefect.
Figure8:Theadjacentmucosatotheskullbasedefectis
removedtopermitvisualizationofthemargins.Abonyor
cartilagenousplate(dashedline)shouldbeplaced
intracraniallytocovertheskullbasedefectforanydehiscence
greaterthan5mmindiameter.Thenasalseptumoran
absorbableprostheticplatearemostcommonlyusedforthis
purpose.
Figure9:Theclosureiscompletedwithplacementofanasal
mucosalgraftoverthedehiscentskullbaseandplateinsert.A
nasalspongecanbeplacedtomaintainpressureonthe
underlyingmucosalgraft.
TransphenoidalDrainageofaPetrousApexCholesterol
Granuloma
Figure1:Axialviewofapetrousapexcholesterolgranuloma
thatextendsmedialtotheinternalcarotidartery.Themedial
abutmentofthesphenoidsinus(SS)makesthetranssphenoidal
routefavorablefordrainage.
Figure2:Adistortmentoftheposterolateralwallofthesphenoid
sinusisinducedbythemedialextentionofthepetrousapex
cholesterolgranuloma.
Figure3:Atranssphenoidendoscopicapproach,permits
incisionandevacuationofthecholesterolgranuloma.
Figure4:Axialviewofapetrousapex
cholesterolgranulomathatextendsmedialtotheinternalcarotid
artery.Despitenothavingasextensiveabutmentwiththe
sphenoidsinus,thislesioncanstillbeincisedandevacuated
viaatranssphenoidalapproach.
Figure5:Theposteriorwallofthesphenoidsinusmustbe
opened(dashedline)topermittheexposurenecessaryto
evacuatethecholesterolgranuloma.
Figure6:Anangleddrillisusedtoremovetheboneliningthe
posteriorsphenoidsinus.
Figure7:Anincisioninthewallofthecholesterol
granulomashouldbemadewidelytoavoida
stenoticevacuationroute.
Figure8:Axialviewofapetrousapex
cholesterolgranulomathatdoesnotextendtothemedialmargin
oftheinternalcarotidartery.Thismakesthetranssphenoidal
approachtoincisionandevacuationnotanoptionforthis
configurationofacholesterolgranuloma.
AllimagesarecopyrightbyRKJackler.Permissiongrantedfornonprofiteducationaluseofimages,withattributiontotheirsource.
Createdby:RobertJackler(surgeon)andChristineGralapp(artist)
Withcontributionsby:NikolasBlevins,GriffithHarsh,Michael
Kaplan,LawrencePitts,CharlesYingling,&CoreyMass
http://med.stanford.edu/sm/ohns-skull-base-surgery-atlas/