The Cerebellum and White and Gray Matter - My-MS.org

The cerebellum functions closely with the cerebral cortex and the brain stem. It's separated from the cerebrum by the fold of dura called the tentorium. It's ...   Home » Anatomy » BrainAnatomy-Part3 «   Printer-FriendlyVersion  Cerebellum Attherearofthebrainisthecerebellum.Thecerebellumissimilartothe cerebruminthateachhashemispheresthatcontroltheoppositesideofthebody andarecoveredbygraymatterandsurfacefolds.Thevermis,whichisacentral constrictedarea,connectsthehemispheres. Thecerebellumisconcernedwiththeautomaticregulationofmovementandposture, andthelearningofnewmotorpatterns.Thecerebellumbasicallycoordinatesbody movementandislocatedatthebackofthebrainbeneaththeoccipitallobes. Thecerebellumfinetunesmotoractivityormovementsuchasthefinemovements offingers.Thecerebellumcontrolsbalanceorequilibrium,posture,andcoordination bycontrollingthetoneofmusclesandthepositionoflimbs.Thecerebellumis importantinone'sabilitytoperformrapidandrepetitiveactionssuchas playingavideogame.Inthecerebellum,right-sidedabnormalitiesproduce symptomsonthesamesideofthebody. Thecerebellumfunctionscloselywiththecerebralcortexandthebrainstem. It'sseparatedfromthecerebrumbythefoldofduracalledthetentorium.It's dividedintotwolaterallobesconnectedbyafingerlikebundleofwhitefibers calledvermis.Theouterlayerofthecerebellumconsistsoffinefoldscalled folia.Threefiberbundlescalledcerebellarpedunclesconnectthecerebellum tothethreepartsofthebrainstem:Themidbrain,thepons,andthemedulla oblongata. Damagetothecerebellumorthecerebellarpedunclesisverycommoninmultiple sclerosis(MS)duetothelargeamountofwhitematterinthesestructures. Someofsymptomsassociatedwithdamagetothecerebellumorthenervoustracts leadingtoitare: • Dysdiadokokinesia(difficultyinperformingrapidalternatingmovements) • Ataxia(difficultyincoordinatingmovements) • Tremors • Lossofbalanceandvertigo • Muscleweakness • Dysarthria(lossofcoordinationofthemusclescontrollingspeech) • Lossofposturaltone WhiteMatter Thewhitematterregionsofthecentralnervoussystem(CNS)contrastwith thegraymatterregions.Thewhitematterreferstothosepartsofthebrain andspinalcordthatareresponsibleforcommunicationbetweenthevarious graymatterregionsandbetweenthegraymatterandtherestofthebody. Inessence,thegraymatteriswheretheprocessingisdoneandthewhite matteristhechannelsofcommunication. Thewhitematterisso-calledbecauseitcontainsmanynervefibersorneurons thataresheathedinthewhitefattyinsulatingproteincalledmyelin.In section,myeliniswhitewhereasthegraymatteristhatcolorduetoallthe graynucleicontainedinthecellsthatmakeitup. Thewhitematterisfoundintheinnerlayerofthecortex,theopticnerves, thecentralandlowerareasofthebrainorbrainstem,andsurroundingthe centralshaftofgraymatterinthespinalcord. MSispredominantlyadiseaseofthewhitematterintheCNS.About95%ofall lesionsassociatedwithMSoccurinthewhitematter. GrayMatter ThegraymatterregionsoftheCNS,thebrainandspinalcord,contrastwith thewhitematterregions.Thegraymatteristheareaswheretheactual "processing"isdonewhereasthewhitematterprovidesthecommunication betweendifferentgraymatterareasandbetweenthegraymatterandthe restofthebody. Theneuronsinthegraymatterconsistofneuronalcellbodiesandtheir dendrites.Thedendritesareshortprotrusionsthatcommunicatewithimmediately neighboringneuronsintheCNS.Incontrastwiththeneuronsofthewhite matter,graymatterneuronsdon'tcontainlongaxonsthattransmitthenerve impulsestomoredistantregionsoftheCNS. Enlargebypassingoverorclicking imageinfo ThisimageisCopyright©My-MS.organdfallsunderImageLicenseE definedundertheImageLicensesectionoftheDisclaimerpage. About40%ofthehumanbrainismadeupofgraymatterandtheother60%is whitematter.Thegraymatter,however,consumesabout94%ofthetotaloxygen usedbythebrain. ThevastmajorityofMSlesionsoccurinthewhitematterareasbutasmall number,about5%,dooccurwithinthegraymatter.Graymatterisso-called becauseinsectionithasagraycolorduetoallthegraynucleiinthecells thatmakeitup. GraymatterinvolvementisdetectedevenintheearlieststagesofMS,andgray matteratrophyoccursatafasterratethanwhitematteratrophyearlyinthe diseasecourse. Studieshavedeterminedthat: • Graymatterinvolvementandinparticularcortical demyelinationcanbeextensiveinMS. • Graymatterpathologymayoccurinpartindependently ofwhitematterlesionformation. • Aprimarilygraymatter-relatedprocessmaybethe earliestmanifestationofMS. • Graymatterinvolvementisassociatedwithphysical disability,fatigue,andcognitiveimpairmentinMS. • Graymatterdiseasemighthelpexplaintheobserved dissociationbetweenmarkersofinflammatorydemyelination(relapses, whitemattergadoliniumenhancement,whitematterlesionburden)and diseaseprogression. It'slikelythatgraymatterdamageisrelatedtowhitematterdamage.However, continuedstudiesofgraymatterpathologyaswellasneuronalandaxonal involvementinMSandrelatedexperimentalmodelsarenecessarytobetter understandtheetiologyandpathogenesisofthedegenerativecomponents. InarecentsupplementtoNeurology,itwasstatedbasicallythatrecentstudies havefoundthatgraymatterdamage,whichisn'teffectivelydetectedthrough MRI,maybemorepronouncedthanwhitematterdamage,especiallyearlyinthe diseaseprocess,andcanhaveconsiderableimpactonclinico-cognitive functioningandneuro-psychologicaldeficits.Sograymatterdamageisprobably greaterthanearlierbelievedorseenonanMRIandbecauseofthisfinding, it'sfeltthatcognitiveandpsychologicalfunctionsmayhavebeenimpactedtoa greaterextent. TopofPage «PreviousPage | NextPage» Copyright©2008-  My-MS.org-Allrightsreserved