周围神经疾病 (2)

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1、PeripheralNeuropathy（周围神经病）陶恩祥(taoenxiang@yahoo.com.cn)中山大学孙逸仙纪念医院神经科PeripheralNervousSystemANATOMYOFPERIPHERALNERVESAxons&Myelin1.AxonsthickerthanonemicronintheCNSandperipheralnervoussystem(PNS)aremyelinated.2.Myelinisaspiralsheetofcellmembranewrappedaroundtheaxon.IntheCN

2、S,myelinisproducedbyoligodendroglialcellsandinthePNSbySchwanncells.Eacholigodendrocytemakesmultiplesegmentsofmyelinthatwraparoundmanyaxons.EachSchwanncellmakesonesegmentofmyelin.Thisisonereasonwhyperipheralmyelinregeneratesmoreefficiently.NodesofRanvierNodesofRanvierarepoi

3、ntsofdiscontinuitybetweenadjacentmyelinsheathsinwhichtheaxonisnotcoveredbymyelin.UnmyelinatedaxonsUnmyelinatedaxonsarecoveredbySchwanncellcytoplasm,butthereisnospiralingofSchwanncellmembranearoundthem.ThecompositionofmyelinThestructureofcentralandperipheralmyelinisessentia

4、llythesame.Myeliniscomposedof70%lipidsand30%protein.1.someimportantdifferencesinmyelinproteinsbetweenCNSandPNS.（1）someallergicreactionagainstPNSmyelindoesnotcausecentraldemyelinationandviceversa;（2）inheritedmetabolicdisordersofmyelinproteinsthataffectperipheralnervesdonotd

5、amagecentralmyelin.2.ButlipidsaresimilarbetweenPNSandCNSmyelin.So,metabolicdisordersofmyelinlipids,suchasmetachromaticleukodystrophy,affectboth,thecentralwhitematterandperipheralnerves.OrganizationofSpinalNerves:1.Root–insidevertebralcanala.dorsalsensoryrootwithaganglionb.

6、ventralmotor2.Mixedspinalnerve3.Ramia.dorsal-mixedtoskinandmusclesofbackb.ventral-mixed“spinalnerve”toventrolateralbodysurfacesandlimbsc.whiteramuscommunicansmotorANSd.grayramuscommunicansmotorANS1.Fig14-7DermatomesSensoryinnervationsbyspecificspinalnervesEachpairofspinal

7、nervesmonitorsspecificregionofbodysurface.Clinicalsignificance?PrincipalPlexusesBraidsofventralramiofcervical,thoracic,lumbarorsacralspinalnervesCervicalPlexusPhrenicnerve-innervatesdiaphragmMusculocutaneousnerve-innervatesbicepsandbrachialismusclesMediannerve-innervatesla

8、teralflexorsUlnarnerve-innervatesmedialflexorsRadialnerve-innervatesforearmextensorsBrach