神经影像与临床.ppt

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,*,Multiple sclerosis(MS),is considered the most common,inflammatory autoimmune,neurologic disorder,involving especially the,white matter,(,WM,),the main pathologic features of which include a,primary,perivascular inflammation,demyelination,gliosis,and,axonal injury,.MS is a,chronic disease,estimated to affect 2.5 million people worldwide,and almost 400,000 persons in only the United States.,Women,are affected twice to 3 times as frequently as men,and it is uncommon in children,accounting for only about 0.3%to 0.4%of all cases.The symptoms begin most frequently during the,third,and,fourth,decades,.However,MS can develop after age,50 years,accounting for 10%of cases.MS is the most frequent cause of,nontraumatic,neurologic disability,in young and middle-age adults.Thus,early diagnosis is required to promptly begin a more effective treatment.,MS,:different imaging features.(A,B)Axial fluid-attenuated inversion recovery(,FLAIR,)shows typical appearance of,deep WM,plaques like multiple hyperintense lesions in,subcortical,and,cerebral deep WM,mostly,ovoid,in shape.(C,D)Sagittal FLAIR shows demyelinating plaques along the margin of,lateral ventricles,and the,corpus callosum,with the typical,radial arrangement,called,Dawson fingers.,MS,:different imaging features.Axial T1-weighted images before(E)and after(F)gadolinium administration show a single plaque in the right frontal lobe,which shows,enhancement,after contrast injection,consistent acute inflammatory,demyelination,.(G),Diffusion-weighted imaging,reveals a,high signal lesion,which may be related to the,acute phase of the disease.,A 55-year-old woman presenting with a 1-month history of homonymous hemianopsia.(A)Sagittal,T1-,weighted image shows a,large hypointense occipital,lesion,hyperintense,on axial,FLAIR,(B).(C)Sagittal,T1,-weighted image and gadolinium-,enhanced,axial image(D)shows heterogeneous enhancement,along the wall,of the lesion,suggesting acute disease.,A 55-year-old woman presenting with a 1-month history of homonymous hemianopsia.(E)Relative cerebral blood volume map,does not,show a,high perfusion.,(F)Axial,DWI,and,ADC,maps(G)show,restricted diffusion,along the,medial wall,of the lesion,suggesting acute phase.,(A)Sagittal and axial,FLAIR,(B)shows,demyelinating plaques,along the,margin,of the,lateral ventricles,and the,corpus callosum,.(C)In the axial,FA,map,regions of interest were drawn in the plaque,periplaque regions,NAWM.Note that a difference in FA values between lesion,periplaque region,and NAWM can be observed.(D)Midsagittal FA map shows placement of region of interest in the corpus callosum.Note the reduction of FA values in the corpus callosum.,A 7-year-old girl presenting with a 4-week history of progressive left hemiparesis.(AC)Axial,sagittal,and coronal,FLAIR,shows a large,hyperintense,right,frontoparietal,lesion with,lesion-in-a-lesion,appearance,suggesting,demyelinating plaque.,(D,E)Axial,DWI,shows,mildly,hyperintense,signal of the,rim part,mildly hypointense,on,ADC,maps,which may show restricted diffusion,observed in acute disease.(F),Gadolinium-enhanced,axial,T1,-weighted image shows heterogeneous enhancement of the lesion,mostly peripheral,suggesting acute disease.,Multiple T2 hyperintense,WM lesions in different diseases showing the low specificity of this,feature(axial FLAIR).(A),Ischemic small vessel disease;,(B),vasculitis,;,(C),human immunodeficiency virus,;,(D),migraine,;(E),cerebrovascular,disease.,A 37-year-old woman who presented with a 40-day history of progressive paresthesia,weakness of both legs.(A,B)Axial and sagittal FLAIR shows multiple hyperintense lesions along the margin of the body of lateral ventricles and corpus callosum,suggesting demyelination plaques.(C)Gadolinium-enhanced axial T1-weighted image shows ring enhancement of the right frontal lesion and homogeneous enhancement of the left parietal lesion,both suggesting acute inflammation.(D)DWI shows a high signal in both lesions,which may be related to acute disease.,Although,T2,-weighted and fluid-attenuated inversion recovery(,FLAIR,)sequences are,highly sensitive,for,MS,lesions,they,lack histopathologic specificity,.This finding may be explained because,inflammation,edema,demyelination,gliosis,and,axonal loss,are all represented as areas of,high,signal,intensity on these sequences.Thus,they are,not able to differentiate,between,different,plaque subtypes,.,Mildly T1,-weighted SE imaging can be more specific and can,determine,whether the lesion is,acute,or,chronic,.,T1,-weighted SE imaging seems to be,more specific,than T2-weighted imaging for identifying clinically relevant lesions.,Hypo,intense lesions on,T1,-weighted SE,the so-called,black holes,represent chronic plaques,which may correlate with disease progression and disability.,Contrast-enhanced T1,-weighted imaging is routinely used in clinical assessment of patients with MS to,depict acute lesions,.,In the acute inflammatory phase,a,disruption,of the,blood-brain barrier,occurs,and an,acute,lesion appears first as a,nodule,-,enhancing lesion,and subsequently progresses to a,r,ingenhancing,lesion.MR imaging can be 5 to 10 times more sensitive in depicting acute plaques,representing disease activity,than the clinical evaluation of relapses,which suggests that most of the enhancing lesions are clinically silent.,Diffusion MR,imaging has been used to evaluate,MS plaques,.Some,acute plaques,may show,restricted diffusion,mostly at their,margin,.This pattern of enhancement is not specific for demyelinating disease,but its diagnosis can be suspected,because it is frequently,peripheral,and,discontinuous,.This imaging characteristic may also be useful in the differential diagnosis with other expansive lesions,such as,gliomas,which can present restricted diffusion within the solid portion of the lesion,secondary to,high cellularity,.,Diffusion MR imaging has been used to differentiate acute from chronic MS plaques,using,ADC,and,FA,.Although some investigators have used DWI and DTI to try to make such a distinction,the results are inconsistent.Initial papers suggested that ADC is increased within MS plaques compared with normal WM.Current evidence indicates that the pathologic substrate of MS lesions is different among MS subgroups and that disease progression may be associated with neuronal and axonal loss.Therefore the increase in diffusivity possibly reflects expanded free water content within the lesion,although the relative contribution from edema,demyelination,and axonal loss is difficult to determine.The,highest diffusion values,seem to be found in hypointense lesions,the so-called,black hole,compared with enhancing lesions and isointense lesions.However,hypointensities on T1-weighted images do not solely represent tissue destruction of the late stages of the disease but may also be associated with acute lesions,resulting in enlargement of the extracellular space as a result of edema and inflammation,a process that is potentially reversible at follow-up.,Acute edematous lesions were found to sometimes have even higher ADC values than chronic lesions.Thus,predicting activity of the disease based on the DWI findings,measured through ADC maps,is unreliable In general,MS lesions have decreased FA values on DTI when compared with the contralateral NAWM and normal control subjects The reduction in the FA values within the plaques indicates the disruption of myelin and axonal structures that leads to disorganization and increased extracellular space.Some investigators reported that reduction in FA values observed in enhancing plaques is lower than in nonenhancing plaques,suggesting that DTI can indicate disease activity.FA values can also be found to be reduced in ring-enhancing plaques compared with homogenous enhancing lesions.However,conflicting results have been reported when FA values are used to differentiate acute from chronic plaques.Some reports were not able to depict any statistical difference between these histopathologic MS plaque subtypes.,In an acute lesion tissue damage can be permanent,related to neurodegeneration,and on the other hand it can be transient,as observed in edema,demyelination,and remyelination.The postprocessing of DTI data may add new information regarding the cytoarchitecture and histopathologic alterations related to MS.The tensor model provides,besides the FA and MD,other measures of the diffusion direction.For each vector,a value known as an eigenvalue is attributed(,1,2,and,3).Axial diffusivity(eigenvalue,1)is defined as the diffusion along the long axis and is higher than across the main fibers.It indicates a rate for the diffusion of water parallel to a bundle of axons or tract.,Radial diffusivity is the one observed at the other perpendicular plans,represented by the average of eigenvalue,2 and,3,and represents the rate of the diffusion of water perpendicular to the axons.Demyelination in general leads to reduction in radial diffusivity values,whereas axonal damage leads to axial diffusivity alterations.Increased radial diffusivity relates to demyelination,and decreased radial diffusivity is seen during remyelination.Based on these findings regarding axial and radial diffusivities alterations related to histopathologic intrinsic characteristics of MS plaques,a recent study suggests that DTI can determine the plaque subtype:acute,subacute,or chronic.Such a distinction is hard to make using FA values and MD.Although these are preliminary results,the investigators suggest that eigenvalues may be more sensible than FA and MD measurement when the demyelinating process is the most important damage.In the acute plaque,the demyelinating process is predominant,with altered radial diffusivity.A mixed pattern of histopathologic damage is observed in chronic plaques,including demyelination,altering radial diffusivity,and axonal loss,altering axial diffusivity.,On the a specimen showing the perivenous inflammation in MS.MS,starts,as,inflammation,around,these,veins,.In the first four weeks of the inflammation there is enhancement with gadolinium due to loss of blood brain barrier.First there is homogeneous enhancement but this can change to ring enhancement.,Multiple sclerosis,(MS)is a relatively common,acquired,chronic,relapsing,demyelinating,disease,involving,the,central nervous system,.It is by,definition,disseminated,not only in,space,(i.e multiple lesions),but also in,time,(i.e lesions are of different age).,A number of clinical variants are recognised,each with specific imaging findings and clinical presentation.They include:,classic MS,(Charcot type),tumefactive multiple sclerosis,acute malignant Marburg type,Devic disease,(Devic opticomyelitis),Schilder type,(diffuse cerebral sclerosis),Balo concentric sclerosis,(BCS),Epidemiology,Presentation is usually between,adolescence,and the,sixth decade,with a,peak,at approximately,35 years,of age.There is a strong,well recognised,female predilection,with a F:M ratio of,2-3:1,.,Multiple sclerosis has a,fascinating geographic distribution,:it is rarely found in,equatorial regions,with incidence gradually increasing with distance from the,equator,.,Clinical presentation,Clinical presentation is both highly variable acutely,as a result of varying plaque location as well as over time,with a number of patterns of longitudinal disease being described,1.,relapsing,remitting,most common(70%of cases),patients exhibit,periodic symptoms,with,complete recovery,(early on),2.,secondary progressive,approximately 85%of patients with relapsing-remitting MS eventually enter a secondarily progressive phase,3.,primary progressive,uncommon(10%of cases),patients do not have remissions,with neurological deterioration being relentless,4.,progressive with relapses,5.,benign MS,15-50%of cases,defined as patients who remain functionally active for over 15 years,As is evident from this list,there is overlap,and in some cases patients can drift from one pattern to another.Upon presentation patients often have evidence of multiple previous asymptomatic lesions,and the diagnosis of multiple sclerosis can be strongly inferred.In other instances patients present with the first plaque.This is known as clinically isolated syndrome(CIS)and not all patients go on to develop MS.,Symptoms may be,sensory or motor or mixed,including cranial nerve involvement e.g.,trigeminal neuralgia,or,optic neuritis,.,Pathology,The exact aetiology is poorly known although it is believed to have both,genetic,and,acquired contributary components,.An infectious agent or at least catalyst have long been suspected due to the geographic distribution and presence of clusters of cases,however no agent has as yet been firmly identified.,MS is believed to result from a,cellular mediated auto immune response,against,ones,own myelin components,with,loss,of,oligodendrocytes,with,little,or,no axonal degeneration,.,Demyelination,occurs in,discrete,foc,i,termed,plaques,which range in size from a,few millimetres,to a,few centimeter,s and are,typically perivenula,r.,Each lesion goes through three pathological stages,early acute stage,(active plaques)active,myelin break down,plaques,appear,pink,and,swollen,sub acute stage,plaques,become,paler,in,colour,(chalky),abundant macrophages,chronic stage,(inactive plaques,/,gliosis,)little or no myelin breakdown,gliosis,with associated,volume loss,appear,grey,/,translucent,Patients,serum IgG levels,tend to be,elevated,and,CSF,analysis commonly shows,oligoclonal bands,Associations,a strong association with,HLA-DR2 class II,has been identified.,Melkersson-Rosenthal syndrome:postulated,Radiographic features,Plaques can occur anywhere in the central nervous system.They are typically ovoid in shape and perivenular in distribution.,CT,CT features are usually non specific,and significant change may be seen on MRI with an essentially normal CT scan.Features that may be present include:,plaques,can be,homogeneously hypo attenuating,brain atrophy,may be evident in with,long standing chronic MS,some plaques may show,contrast enhancement,in the,active phase,MRI,MRI has revolutionised the diagnosis and surveillance of patients with MS.Not only can an MRI confirm the diagnosis,but follow-up scans can assess response to treatment and try and determine the disease pattern,T1,lesions are typically,iso,to,hypo,intense(,chronic,),callososeptal interface may have multiple small hypo intense lesions(Venus necklace)or the,corpus callosum,may merely appear,thinned,T2,:lesions are typically,hyper,intense,FLAIR,:lesions are typically,hyper,intense,when arranged,perpendicular,to,lateral ventricles,extending,radially outward,(best seen on parasagittal images)they are termed,Dawson fingers,T1 C+(Gd),:,active,lesions show,enhan,cement,enha,ncement is often,incomplete,around the periphery(,open ring sign,),DWI/ADC,:,active,plaques may demonstrate,restricted diffusion,MR spectroscopy,:may show,reduced NAA,peaks within plaques,Even on a single scan,some fea