神经成像

神经成像南华大学附二医院魏麓云主任医师定义：神经成像是指用MRI扫描颅神经和周围神经，显示相应神经的影像。第一部分：颅神经成像一、颅神经成像是指十二对颅神经脑外、颅内行走的路径以及邻近脑组织结构的影像。当然，也包括病理改变。这种病理改变即包括颅神经本身，也包括邻近脑组织，以及邻近脑组织病理改变对颅神经的影响，或者反之。二、意义：从粗放型临床科室向精细化研究型科室转化。三、注意事项：（1）看片者要有神经局解的知识，同时要有三维结构的思维，也就是说同一个颅神经的路径在不同的维度，它的位置、形状、邻近脑组织、血管肯定不同。如横断位、冠状位、矢状位，彼此之间是不同的。（2）要清楚知道MRI不同序列所表达的含义（3）申请者必须要写清做哪对颅神经，部位在哪里？是否需要强化？在申请单上一一写清，对别人，对自己都有好处。（4）为什么要强化？其实，神经成像不需要强化，强化的目的：1颅神经周围脑组织病理改变，包括血管、脑膜病理改变；2颅神经本身病变需要。（5）DTI与神经成像都是精细化诊断，前者诊断传导束受损情况，要求精细化到具体传导束，例如脊丘束，皮质脊髓束，皮质脑干束等等。也就说“吃点菜”。因此，申请者要点清是什么传导束而不是什么部位。（6）搭配问题：例如：Bell面神经炎查看面神经管，由于面神经出脑后在颅骨内走很长一段，做MRI神经成像，看不清面神经管，因此，需要做面神经管CT.神经成像与微血管的关系，需要SWI，或3DTOFMRA,例如动脉瘤与第三对颅神经关系。（7）0.5TMRI扫描80例病人。结论：IngeneralthecranialnerveswerebestviewedwithT1-weightedimages,nervesIII,VIlandVIIIwereviewedinallthreeplanes(axiaLcoronalandsagitttal)in76-98%ofthepatients.NervesIX,X,XIandXIlwereviewedonlywiththeaxialplane.in80%ofcases.ItwasdifficulttoseparatecranialnerveIXfromX,andXIfromXIIbecauseoftheirtinystructuraanddoseproximitytoeachother.三、MRI颅神经局部解剖Asmentionedabove,theolfactoryandopticnervesarenottruenervesbutanextensionofthebrain,that′swhytheyareaffectedbytumorssuchasgliomasandmeningiomasincontrasttoIII-XIInevesthatcandevelopschwannomas.第一对颅神经：嗅神经（TheOlfactoryNerve）Unlikemostcranialnerves,theolfactorynerveconsistsofwhite-mattertractsandisnotsurroundedbySchwanncells.Toavoidconfusingtheolfactorynervewiththegyrusrectusonaxialimages,itisimportanttorememberthattheolfactorynerveissituateddeepintheolfactorygroove,inferiortothegyrusrectus.第二对颅神经：视神经（TheOpticNerve）Liketheolfactorynerve,theopticnerveisawhite-mattertractwithoutsurroundingSchwanncells.Itincludesfouranatomicsegments:retinal,orbital,canalicular,andcisternal(Fig3).Theretinalsegmentleavestheocularglobethroughthelaminacribrosasclerae(theopticforamenofthesclera).Theorbitalsegment,whichissurroundedbyaduralsheathcontainingCSF,travelsthroughthecenterofthefat-filledorbit.Thecanalicularsegmentistheportionthatliesintheopticcanal,belowtheophthalmicartery.Thissegmentofthenerveisfrequentlyoverlookedonradiologicimages,soitshouldbespecificallysoughtwhenimagingforvisionloss.Finally,thecisternalsegmentofthenervecanbevisualizedinthesuprasellarcistern,wherethenerveleadstotheopticchiasm.Keyanatomiclandmarksinthesuprasellarcisternincludetheinfundibulum(stalk)ofthepituitarygland,theanteriorcerebralartery,and,posteriortothechiasm,themamillarybodies(Fig4).BecauseasingleimageobtainedwithanSSFPsequenceusuallydepictsonlyashortsegmentoftheopticnerve,thick-sectionreconstructionofSSFPacquisitionsmaybeneededtoallowexaminationoftheentirelengthofthenerveonasingleimage.StandardT2-weightedimagesalsoareusefulforthispurpose(Fig4).Fig.6:TRAUMA.Thispatientreferedmonocularvisuallossafterheadtrauma.Theseimagesobtained10monthsaftertheinjuryshowathinandhyperintensesecondleftcranialnervecomparedwiththerightone.Axialfat-saturatedT2weightedimage(WI)(1)fat-saturatedcoronalT2(2)andaxialT2WI(3).第三对颅神经：动眼神经（TheOculomotorNerve）Theoculomotornerveoriginatesfromnucleideeptothesuperiorcolliculus,ventraltothecerebralaqueduct,andinferiortothepinealgland.Thenervethentravelsacrossthemidbrainfromposteriortoanterior.Theoculomotornerverootemergesintotheinterpeduncularcistern,andthisrootentryzoneinthecisternisagoodwaytoidentifytheoculomotornerveonaxialSSFPMRimages(Fig6).Intheprepontinecistern,thenervetravelsbetweenthesuperiorcerebellarandposteriorcerebralarteries,whichmakesiteasytoidentifyoncoronalSSFPimages(Fig7).Thecavernoussegmentoftheoculomotornerverunsalongthelateralwallofthecavernoussinusandisthemostsuperiorofthenervesinthissinus.Theoculomotornervethenenterstheorbitthroughthesuperiororbitalfissure,beforesplittingintosuperiorandinferiordivisionslateraltotheopticnerve.Knowledgeofthisanatomymaybehelpfulforidentifyingthepreciselocationofanerveabnormality(Fig8).第四对颅神经滑车神经（TheTrochlearNerve）Thetrochlearnerveistheonlynervewitharootentryzonearisingfromthedorsal(posterior)brainstem.Afterexitingthepons,thetrochlearnervecurvesforwardoverthesuperiorcerebellarpeduncle,thenrunsalongsidetheoculomotornervebetweentheposteriorcerebralandsuperiorcerebellararteries。Thetrochlearnervethenpiercestheduratoenterthecisternabasalisbetweenthefreeandattachedbordersofthecerebellartentorium。Aftercompletingitscisternalcourse,thetrochlearnerverunsthroughthelateralcavernoussinusjustbelowtheoculomotornerveandenterstheorbitthroughthesuperiororbitalfissuretoinnervatethesuperiorobliquemuscle.Thenerveisnamedforthetrochlea,thefibrouspulleythroughwhichthetendonofthesuperiorobliquemusclepassesThecisternalsegmentofthistinynerveismosteasilyidentifiableposterolateraltothebrainstem(Fig9).Alongpartofitsintracranialcourse,thetrochlearnerveliesbetweendurallayers,whereitisdifficulttovisualizeonradiologicimages.Particularattentionshouldbegiventotheanterioraspectofthetentoriuminpatientsinwhomthepresenceofisolatedtrochlearnervepalsyissuspected.第五对颅神经（TheTrigeminalNerve）Anunderstandingofthepathologicprocessesthatmayinvolvethetrigeminalnerverequiresadetailedknowledgeofit