Sella Turcica and Parasellar Region(蝶鞍和鞍旁区病变影像诊断)

SellaTurcicaandParasellarRegionDate:September18th,2011Ⅰ.AnatomicApproachtoDifferentialDiagnosisⅡ.PituitaryMicroadenomaⅢ.PituitaryMacroadenomaⅣ.Rathke’sCleftCystⅤ.CraniopharyngiomaⅥ.MeningiomaⅦ.AneurysmAneurysmvsMeningiomaⅧ.HamartomaⅨ.HypothalamicandChiasmGliomaⅩ.GerminomaⅪ.ChordomaⅫ.Metastases1.Firstidentifythepituitaryglandandsellaturcica.2.Thendeterminetheepicenterofthelesionandwhetheritisinthesellaorabove,beloworlateraltothesella.3.Ifitisinthesella,determinewhetherornotthesellaisenlarged.4.Oncethelocationofthemassisclear,analyzethesignalintensitypatterns:isthelesioncysticorsolid?5.Doesitcontainanyabnormalvessels?6.Arethereanycalcifications?Andsoon.7.FinallyestablishaDifferentialDiagnosis.InordertoanalyzeasellarorparasellarmassonMRIweusethefollowinganatomicapproach:ⅠAnatomicApproachtoDifferentialDiagnosisOnacoronalsectionthroughthebrainthereferencestructureisthepituitaryglandwhichliesinthesellaturcica.Itisusuallylargerinfemalesthaninmales-infemalesthesuperiorbordertendstobeconvex,whereasinmalesitisusuallyconcave.Themostcommonabnormalitiesthatariseinthepituitaryglandarepituitaryadenoma,Rathke'scleftcystandcraniopharyngioma.PituitaryglandThenextstructuretoidentifyisthepituitarystalk.Thisisaverticallyorientedstructurewhichconnectsthepituitaryglandtothebrain.Itisthinneratthebottomandthickeratthetop.Embryologically,itisalsoderivedfromRathke'scleftepitheliumandthereforethepathologies,whichcanariseinthepituitaryglandcanalsoariseinthestalk.Thereareafewunusualthingstobeconsideredinchildren,suchasgerminomasandeosinophilicgranulomas.Inadultsmetastasesandoccasionallylymphomacanariseinthepituitarystalk.PituitarystalklymphomaAnothermajorstructureinthesuprasellarcisternistheopticchiasm.Itisanextensionofthebrainandlookslikethenumber8lyingonitsside.Itisglialtissue-thereforethemostcommontumorstooriginateherearegliomas.IntheUSandEuropeanotherfrequentpathologyinthisregionisdemyelinatingdisease-particularlymultiplesclerosis.Thiscanalsobeassociatedwithsomeswellingoftheopticchiasm.OpticchiasmFurthercephaladliesthebaseofthebrain,whichatthislocationisthehypothalamus.Anatomicallythehypothalamusformsthelateralwallsandfloorofthethirdventricle.Themostcommonpathologiestoariseherearegliomas-inchildrenhamartomas,germinomasandeosinophilicgranuloma.HypothalamusAveryimportantstructureinthisareaistheinternalcarotidartery.ItrunsacomplexanatomiccourseasitpassesthroughtheskullbaseshapedlikeanSonlateralviews.Itpassesthroughthecavernoussinus.Thesegmentcranialtothisisknownasthesupracavernoussegment.Thisbifurcatesintotheanteriorcerebralartery,whichpassescraniallytotheopticchiasm,andthemiddlecerebralartery,whichrunslaterally.Aneurysmsandectasiasarepathologiesthatcanarisehere.Onemustalsobeawareofcongenitalvariationsinthecourseoftheinternalcarotid.Sometimesitisverymediallypositionedandcanactuallylieinthemidline.CarotidarteryThecavernoussinusisapairedcomplexofvenouschannels.InthelateralwallofthesinusrunnerveIII(oculomotorius),IV(trochlearis),V1andV2(trigeminus).Thesixthcranialnerve(abducens)runsmoremediallyandislocatedcaudaltothecarotidartery.Themostcommonpathologiesoccurringinthecavernoussinusincludeschwannomasarisingfromthecranialnervesandinflammation,whichcanleadtothrombosis.Thisisknownascavernoussinusthrombophlebitis.Carotid-cavernousfistulasarefistulouscommunicationsbetweenthecarotidarteryandtheveinsofthecavernoussinus.CavernoussinusThemeningescoverthecavernoussinus.Theyarethickerlaterallyandsuperiorlythanmediallyandinferiorly.Themostcommontumortoarisefromthemeningesisofcoursethemeningioma.Duralmetastasisisthesecondmostcommontumortoarisehere.Alsoinflammatorypathologiesoccurinthebasalmeninges-themostcommoninfectionbeingtuberculousmeningitis.Ofthenon-infectiousinflammatorypathologiessarcoidosisisthecommonest.MeningesInferiortothepituitaryglandliesthesphenoidsinus.Thisstructurecontainsairandislinedbymucosaandbone.Posteriortothesphenoidsinusliestheclivus(notshownonthiscoronalsectionthroughthebrain).Pathologythatarisesinthisareaincludescarcinomasarisingfromthemucosaofthesphenoidsinus-squamouscellcarcinomaandadenoidcysticcarcinomaarethemostcommon.Sphenoidsinus(1)Chordomasariseintheclivusandchondrosarcomasandosteosarcomasalsooccurinthisarea.Metastasescanoccuranywhere.Bacterialorfungalinflammatoryprocessesinthesphenoidsinuscanspreadintracraniallyviathecavernoussinus.Sphenoidsinus(2)ⅡPituitaryMicroadenoma(1)Bydefinition,pituitarymicroadenomasarelessthan10mmindiameterandarelocatedinthepituitarygland.Theseimagesshowaclassiccase:onT1alesionabout3-4mmindiameter,slightlyhypointensecomparedtonormalpituitarytissue,locatedinthepituitarygland.OnT2,thelesionisslightlyhyperintense.Thedifferentialdiagnosis:pituitarymicroadenomaorRathke'scleftcyst(thetwocanbeindistinguishable).ThesensitivityofanunenhancedMRIscanfordetectingpituitarymicroadenomasisabout70%.一般：T1低、T2高(蛋白质量≤10万mg/L)少数：T1、T2均高(10万＜蛋白质量＜17万mg/L)少数：T1高、T2低(蛋白质量≥17万mg/L)Itisnotalwaysnecessarytogiveintravenouscontrastfordetectingpituitarymicroadenomasaspatients