医学院神经解剖学教案：脑神经损伤课件

神经解剖学选修课教程4 2脑神经损伤lesionsofthecranialnerves NervesI II andVIIIaredevotedtospecialsensoryinput NervesIII IV andVIcontroleyemovementsandpupillaryconstriction NervesXIandXIIarepuremotor XI sternocleidomastoidandtrapezius XII musclesoftongue NervesV VII IX andXaremixed NotethatnervesIII VII IX andXcarryparasympatheticfibers GangliaRelatedtoCranialNervesThetwotypesofgangliarelatedtocranialnerves 1 thosecontainingcellbodiesofafferent somaticorvisceral axonswithinthecranialnerves thesegangliaaresomewhatanalogoustothedorsalrootganglia and 2 gangliathatcontainthesynapticterminalsofvisceralefferentaxons togetherwithpostsynaptic parasympathetic neuronsthatprojectperipherally Sensorygangliaofthecranialnervesincludethesemilunar gasserian ganglion nerveV geniculateganglion nerveVII cochlearandvestibularganglia nerveVIII inferiorandsuperiorglos sopharyngealganglia nerveIX superiorvagalganglion nerveX andinferiorvagal nodose gan glion nerveX Thegangliaofthecranialparasym patheticdivisionoftheautonomicnervoussystemaretheciliaryganglion nerveIII thepterygopalatineandsubmandibularganglia VIII oticganglion IX andintramuralganglion X ThefirstfourofthesegangliahaveacloseassociationwithbranchesofV thetrigeminalbranchesmaycoursethroughtheautonomicganglia ANATOMICRELATIONSHIPSOFTHECRANIALNERVES CN CranialNerveI OlfactoryNerveThetrueolfactorynervesareshortconnectionsthatprojectfromtheolfactorymucosawithinthenoseandtheolfactorybulbwithinthecranialcavity Thereare9 15ofthesenervesoneachsideofthebrain Theolfactorybulbliesjustabovethecribriformplateandbelowthefrontallobe itisnestledwithintheolfactorysulcus Axonsfromtheolfactorybulbrunwithintheolfactorystalk synapseintheanteriorolfactorynucleus andterminateintheprimaryolfactorycortex pyriformcortex aswellastheentorhinalcortexandamygdala ClinicalCorrelationsAnosmia absenceofthesenseofsmell canresultfromdisorders eg viralinfections suchasthecommoncold involvingthenasalmucosa Thetinyolfactorynervesandbulbscanbeinjuredasaresultofheadtrauma Moreover thelocationoftheolfactorybulbandstalk belowthefrontallobe predisposesthemtocompressionfromfrontallobetumorsandolfactorygroovemeningiomas Cranialnerve and oculomotornerve trochlearnerve andabducensnerve Botheyesmoveinthesamedirectiontofollowanobjectinspace buttheymovebysimultaneouslycontractingandrelaxingdifferentmuscles thisiscalledaconjugategazemovement Fixatingonasinglepointiscalledvergence whichrequiresadifferentsetofmuscles includingtheintraocularmuscles Eachoftheextraocularmusclesisbroughtintoplayinconjugategazemovementsorvergence Gazeandvergencecenters Conjugategazeandvergencearecontrolledfromthreeareasinthebrainstem Therearetwolateralgazecentersintheparamedianpontinereticularformationneartheleftandrightabducensnucleiandavergencecenterinthepretectumjustabovethesuperiorcolliculi Summary innervationoftheeye 5 Conjugatelateralmovementsoftheeyes motorneuronsandinternuclearneuronsintheabducensnucleus Frontaleyefieldcontrolsvoluntaryeyemovements Stimulationofthisarearesultsinconjugatedeviationoftheeyestotheoppositeside Eachofthesethreeareascanbeactivatedduringheadmovementbythevestibularsystemviathemediallongitudinalfasciculus Activationofthelateralgazecenterontherightproducesconjugategazetotherightandviceversa Regionsinthecontralatcralfrontallobe theeyefieldarea influencevoluntaryeyemovementsviapolysynapticconnectionstothelateralgazecenters whereasregionsintheoccipitallobein fluencevisualpursuitandalsohaveconnectionswiththevergencecenter Conjugaterightgaze Theimpulsesforvoluntaryconjugatemovementsinrightlateralgazeareinitiatedintheleftfrontallobe Involuntaryconjugatemovementsinrightlateralgazeareinitiatedintheoccipitallobes Pupillarylightreflex VERGENCEMOVEMENTSConvergenceoccurswhenbotheyesarefocusedonanearobject Thisnonconju gatemovementisaccompaniedbycon strictionofthepupilandaccommodation focusing ofthelens Theneuronalpathwaysofconvergencearepoorlyunderstoodbutarepresumedtobesimilartothosejustdescribedforvisualfixation ConvergencerequirestheintegrityoftheoccipitalcortexbutnotthatofthefrontaleyefieldorthePPRF Visualguidanceisalsoprovidedthroughthesuperiorcolliculus Thispro jectstothepretectalarea whichcontainsatleastonegroupofcells thenucleusoftheoptictract withaxonsthatcontactmedialrectusmotorneuronsintheoculo motornucleiofbothsides Controlofpupillarysize Thediameterofthepupilisaffectedbyparasympatheticefferentfibersintheoculomotornerveandsympatheticfibersfromthesuperiorcervicalganglion Fig8 8 Constriction miosis ofthepupiliscausedbythestimulationofparasympatheticfibers whereasdilation mydriasis iscausedbysympatheticactivation Thesizeofbothpupilsisnormallyaffectedsimultaneouslybyoneormoreofsuchcausesasemotion pain drugs andchangesinlightintensityandaccommodation Thepupillarylightreflexisacon strictionofbotheyesinresponsetoabrightlight Evenifthelighthitsonlyoneeye bothpupilsusuallycon strict thisisaconsensualresponse Thepathwaysforthereflexincludeopticnervefibers ortheircollater als tothepreteetum anuclearareabetweenthalamusandmidbrain Fig8 9 Shortfibersgofromthepre teelumtobothEdinger Westphalnuclei thevisceralcomponentsoftheoculomotornuclei bywayoftheposteriorcommissureandtobothciliarygangliabywayoftheoculomotornerves Postganglionicparasympatheticfiberstotheconstrictormusclesareactivated andthesympatheticnervesofthedilatormuscleareinhibited Theinteractionbetweenthesecomponentsoftheautonomicnervoussystemcanbeusedtolocalizealesioninthereflexpathways Theaccommodationreflexinvolvespathwaysfromthevisualcortexintheoccipitallobetothepre teetum Fromhere fiberstoallnucleiofnervesIII IV andVIcausevergenceoftheextraocularmusclesaswellasparasympatheticactivationoftheconstrictorandciliarymuscleswithineacheye Internuclearophthalmoplegiaisduetoatinylesioninonemediallongitudinalfasciculusatalevelbetweenth