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JNeurosurg74:520-522,1991RemovaloftheroofoftheexternalauditorymeatusinapproachingthetentorialnotchthroughalowtemporalcraniotomyTechnicalnoteMARCP.SINt)OU,M.D.,D.Sc.BIoL.,ANDJEAN-LucFOBi:,M.D.DepartmentofNeurologicalSurgery,HOp#a~Neurologique,UniversityofLyon,Lyon,Franceu-Improvedaccesstothetentorialnotchcanbeobtainedbyremovaloftheroofoftheexternalauditorymeatusinassociationwithalowtemporalcraniotomy.Thisapproachdecreasestemporalloberetractionandtheriskofvenousinfarction.Thismethodwasperfectedinthesurgicallaboratoryonfivecadaversandwassuccessfullyperformedinapatientwithagiantaneurysmoftheposteriorcerebralartery.KEYWORDS'subtemporalapproach9tentorialnotch9externalauditorymeatus9aneurysm,giant9posteriorcerebralarteryTHEclassicalapproachtothetentorialnotchandtothepeduncularregion,includingtheposteriorcerebralartery(PCA)anditsP2andP3seg-ments,isbythesubtemporalroute.Theabsenceofacisterninthesubtemporalregionoftenleadstosignifi-canttemporalloberetractionwhichmayresultinthesacrificeoftheveinofLabb6andotherbridgingveinstothetransverseandtentorialsinuses.Todecreasetemporalloberetractionandtherisksofedemaandvenousinfarction,anapproachtothetentorialnotchhasbeendevelopedwhichinvolvesremovaloftheroofoftheexternalauditorymeatusinassociationwithalowtemporalcraniotomy.Wehaveperfectedthiscom-binedapproachinthesurgicallaboratorybilaterallyonfivecadavers(Tablel)andhaveperformeditinapatientwithagiantaneurysmofthePCAattheP2-P3junction.OperativeTechniqueThepatientisplacedinthelateralpositionwiththeheadinathree-pinheadholderandtilted15~down.Averticalanteriorskinincisionismadejustanteriortothetragustoavoiddamagingthefrontalbranchofthefacialnerve;aposteriorincisioniscarrieddowntothemastoidprocess.Thescalpflapandthehelixoftheeararereflectedinferiorlyuntilthesoftexternalauditorymeatusisreached;thisstructureisgentlydetachedfromitsboneroof.Thetemporalmuscleisincisedinacruciformfashionandreflectedinferiorly.Alowtem-poral4.0•3.0-cmcraniotomyisperformedjustabovetheexternalauditorymeatus.Theduramaterofthetemporalfossaisdetachedfromtheskullbaseaswellasthesoftexternalauditorymeatus.Theroofoftheexternalauditorymeatusisremovedatasecondstagewithasagittalvibratingsaw(Fig.1A)anditstemporalandzygomaticedgesaredrilledofftoprovidemoreroom.Themastoidcells,ifopened,mustbecarefullyoccludedwithbonewax.Theduraisopenedandre-flectedinferiorly.Underthesurgicalmicroscope,thetemporallobeisgentlyretractedwithtwonarrowSugitaretractors?~SpecialcareistakennottoteartheveinofLabb6andtheotherbridgingveinstothetransverseandtentorialsinuses.Thepyramidalspacewithanexternalbase,gainedbyremovaloftheroofoftheexternalauditorymeatus,providesadditionalroomforbettervisionandmanipulationofthemicrosurgicalinstruments(Fig.1B).Afterthesurgicalprocedurehasbeencompleted(inourclinicalcase,afterclippingagiantP2-P3aneurysm(Fig.2)),theduraisclosedwithcontinuousstitches.Thereafter,theroofoftheexternalmeatusandthetemporalboneflaparefixedwithwires.Theskinisthenclosed,andapledgetispackedwithintheexternalauditorymeatustoavoidtheriskofcica-tricialstenosis.520J.Neurosurg./Volume74~March,1991LowcraniotomytothetentorialnotchFIG.1.Operativedrawings.A:Thepatientliesinthelateralpositionwiththeheadtilted15~down.Theskinflapandthehelixoftheeararereflectedinferiorly,andalowtemporalcraniotomyisperformed.Theroofoftheexternalauditorymeatus(onthefightside)ist...