Brainstem Dorsolateral Areas Of Surgical Approach, Microsurgical Anatomy Study

ObjectiveToprovideanatomicdatafortreatinglesionsinthedorsolateralregionalofbrainstemthroughcomparingthefarposteriorsubtemporalandtheextremelateralsupracerebelluminfratentorialapproachusedmicrosurgicalapproaches.MMMMeeeetttthhhhooodds1.Tenwetaduitcadavericheadswithoutlesionsfixedbyformalinwereusedinthisstudy.ThinMRIscanningofeachheadwasperformedpreoperatively,andtheimagedateswereinputintotheneuronavigationsystem,thentheoperationplanweremade.2.Tosimulatethefarposteriorsubtemporalandtheextremelateralsupracerebelluminfratentorialapproachineachhead,andthesurgicalexposurewasobservedundermicrocope.3.Duringthesurgicalprocedures,theneuronavigationsystemwasusedtoguidetheoperationsandtocomparetherangoftheexposureandrelatedimportantstructuresofthesetwoapproaches.RRRReeeessssuuuullltts1.Thetemporallobeislimitedtractioncausedbythelabbeveininthefieldofvision,sacrificedtheveinallowgoodvisualizationofdorsolateralbrainstemandthecorrespondingfreetentorialedge;theextremelateralsupracerebelluminfratentorialapproachcanobtainedbettervisualizationincludinglateraltentorialincisura,ambientcisterns,dorsolateralofthemesencephalon,trochlearnerveandtheaccompaniedsuperiorcerebellarartery,posteriorcerebralartery(p2,p3),medialposteriorchoroidalarteryandlateralquadrigeminalcistern,aswellascreateenoughworkingspacetodorsolateralbrainstem;skeletonizationofthesigmoidsinusandtransversesinuspermittedamoreanteriorviewoflaterialbrainstemandthecorrespondingfreetentorialedge.2.Thedrainingveinsencounteredinfarposteriorsubtemporalislongerthanintheextremelateralsupracerebelluminfratentorialapproach(p<0.05);thetwoapproachdistancewasnosignificantdifference(p>0.05);Theextremelateralsupracerebelluminfratentorialapproachviewgainedmorethanfarposteriorsubtemporalapproachbeforetentorialincision(p<0.05)andnosignificantdifference(p>0.05)aftertentorialincision;theverticalorhorizontalangleintwoapproacheswasnosignificantdifference(p>0.05).CCCCoooonnnncccclllluuuussssiiioonThefarposteriorsubtemporalapproachdirectlyexposedthe ObjectiveLesionssituatedposterolaterallyalongthemesencephalonpresentwithaspecialchallenge.FarposteriorsubtemporalapproachrisksinjurytotheveinofLabbe.Midlineandparamediansupracerebellarinfratentorialapproachdonotadequatelyexposethistreacherousregion.Anextremelateralsupracerebellarinfratentorialapproachwasusedtoapproachlesionsatthislocation.MMMMeeeetttthhhhoooddsweretrospectivelyanalyzedourexperiencein11patientswithlesionsatdorsolateralbrainstemandtentorialringtreatedbytheextremelateralsupracerebellarinfratentorialapproach.Themaximumdiameterofthetumorsrangedfrom3.0to6.7cm(mean,4.5cm).Thesigmoidsinusandthetransversesinuswerethoroughlyskeletonizewiththeboneremovalincludingmastoidandoccipital.Thestaysuturesoftheduraflapstopullthesigmoidsinusanteriorlyandthetransversesinusupwardandthelateralaspectofthebrainstemisapproachedviathesupracerebellarinfratentorial.RRRReeeessssuuuulllttsThoroughlyskeletonizethesinusandstaysuturesoftheduraflapstopullthesigmoidsinusanteriorlyandthetransversesinusupwardwidentheopeningintotheinfratentorialspaceandtheposteriorsurfaceofthepetrousbone.Grosstotalresectionsofthetumorswereachievedin8cases,subtotalresectionsin3cases.Nopatientsdied.Neurologicaldeficitsincludingheadacheandfacenumbnessimprovementwerein7 casesandunchangedwerein2cases,and2patientswerefoundnewcranialnervespalsyoccurred.AllcaseshadbeendemonstratednotumorrecurrenceorgrowthbyMRIscanningduringthefollow-upperiodof1to24monthsandneurofunctionrecoveryin9cases,1caseoffacenumbnesswasimprovedandfaceparalysisin1case.ConclusionTheextremelateralsupracerebellarinfratentorialapproachcanenhancethesurgicalexposure,andenlargetheoperativeview,andcutearlythebloodsupplyoftumorearlier,andavoidtheexcessiveretractiononcerebellum,aswellasfacilitatetheprotectionofthesevitalcranialnervesandvesselsaroundbrainstem.Theextremelateralsupracerebellarinfratentorialapproachiseffectiveforapproachingtheposterolateralmesencephalon.