神经影像与临床课件.ppt

1、imaging and clinical 10 Leukoaraiosis(脑白质疏松症脑白质疏松症)represents a heterogeneous diffuse anomaly of cerebral white matter localized predominantly periventricular,detected by CT scan(hypodensity)or MRI(hyperintensity on T2 weighted images or FLAIR).Leukoaraiosis affects approximately 7%of cases with isc

2、hemic stroke,20%in those with lacunar infarcts,30-40%of patients with dementia and 2/3 of patients with vascular dementia.Also in old people is in association with vascular risk factors like arterial hypertension.Pathophysiology:in region with leukoaraiosis,there are areas of demyelination,increased

3、 perivascular space,gliosis and axonal loss.Initially it was thought that demyelination was secondary to incomplete ischemia but PET scan revealed the los as totality of nervous fibers.The same images also appear in obstructive hydrocephalus,disseminated metastasis of white matter and lymphomas.Cere

4、bral white matter is vascularised by penetrating arteries and arterioles which are branches of larger superficial cerebral arteries.Structural modification of these arteries are as follow:from concentric hyaline deposits of artery wall,to lipo-hyalinosis(it is referred to severe disorganisation of v

5、ascular bed with macrophage presence)and fibrinoid necrosis.In asymptomatic elders the lumen of these arteries are decreased significantly.Pathological studies suggest that leukoaraiosis is one of the manifestations of cerebral small vessels disease.From this point of view it can be explained the re

6、lation between leukoaraiosis and lacunar infarcts.Age and arterial hypertension are associated more frequently with ischemic leukoaraiosis,where hypercholesterolemia,diabetes mellitus,and myocardial infarction are associated more frequent with isolated lacunar infarcts.So suggested non-atheromatosis

7、 pathogenesis of cerebral small arteries implicated in ischemic leukoaraiosis.Staging of leukoaraiosis in grades according to lesion severity and their advancement is done with the help of cerebral MRI scan:Stage I:hyperintense lesions on T2 weighted and FLAIR images are spot-like and are located in

8、 neighborhood of frontal horns of lateral ventricles.Stage II:white matter lesions are located around subependymal region of lateral ventricles.Stage III:white matter lesion on T2 weighted and FLAIR are the same as in stage II in addition focal spot-like lesion of deep white matter.Stage IV:hyperint

9、ense white matter lesions on T2 weighted and FLAIR images are extended,fusiform and interconnected.FLAIR images of single subcortical leukoaraiosis(SLA)(a),multiple SLA(b),large multiple SLA(c),and periventricular leukoaraiosis(PLA)(c).Arrow heads and arrows show SLA and PLA,respectively.Leukoaraios

10、is in 1 region(frontal)marked by arrow Advanced Leukoaraiosis(in bilateral frontal and occipital regions)marked by arrows Patient S.B.,60 years,smoker,history of myocardial infarction,admitted for vertigo,memory disturbances and headache.MRI scan shows:leukoaraiosisstage I,deep parietal lacunar infa

11、rct on right side.Stage I:hyperintense lesions on T2 weighted and FLAIR images are spot-like and are located in neighborhood of frontal horns of lateral ventricles.Patient L.H.,65 year,with untreated arterial hypertension,smoker,admitted for left hemiplegia suddenly occurred.Cerebral MRI scan shows

12、primary right temporo-parietal primary intracerebral hematoma,mixed cerebral atrophy,leukoaraiosis stage II.Stage II:white matter lesions are located around subependymal region of lateral ventricles.Patient C.N.,63 years,with arterial hypertension,diabetes mellitus,peripheral arterial disease,gait a

13、bnormalities for one year,frequent falling and memory disturbances.Cerebral MRI scan shows:mixed brain atrophy and leukoaraiosis stage II.Patient P.I.,70 years,with arterial hypertension,diabetes mellitus,with left posterior cerebral arterial ischemic stroke in the last 3 years,admitted for righthem

14、iparesis and mixed aphasia.Cerebral MRI shows acute left middle cerebral arterial stroke,old posterior cerebral arterial stroke on left side and leukoaraiosis stage III.Stage III:white matter lesion on T2 weighted and FLAIR are the same as in stage II in addition focal spot-like lesion of deep white

15、 matter.Patient M.G.,71 years,known with arterial hypertension,dyslipidemia,history of bilateral PCA Infarcts(first one in 2004 and the second in 2008),cortical blindness,with sphincter abnormalities for some months,gait and memory diffi culties aggravated.Cerebral MRI scan shows:mixed brain atrophy

16、,leukoaraiosis stage II-III,bilateral old occipital ischemic lesions.Patient G.V.,68 years,history of untreated arterial hypertension of 10 years,with gait apraxia,dementia,phonation abnormalities for about one year.Cerebral MRI shows mixed brain atrophy and leukoaraiosis stage IV.Stage IV:hyperinte

17、nse white matter lesions on T2 weighted and FLAIR images are extended,fusiform and interconnected.Forms of white matter lesions(WML);small caps(A),large caps(B),extending caps(C),thin lining(D),smooth halo(E),irregular periventricular WML(F),punctuate deep WML(G),deep WML beginning confluence(H),con

18、fluent deep WML(I)With the help of MRI scan leukoaraiosis was classified in 4 stages,according to severity and extension(Brand-Zawadzki).Stage II was present frequently in patients with acute stroke.Stage III was in patients with chronic vascular lesions.Stage IV in our studied group was found in th

19、ose with Binswanger disease.Severity of leukoaraiosis increases with age.Severity of neurologic symptoms is in direct proportion with severity of leukoaraiosis Leukoaraiosis is a risk factor for cognitive decline,in our study this affect was accentuated due to association with brain atrophy in 66%of

20、 all cases.Presence of leukoaraiosis is associated with increased risk of stroke recurrence.Progressive multifocal leukoencephalopathy(PML：进行进行性多灶性白质脑病性多灶性白质脑病)is a demyelinating disease which results from the JC virus（多瘤病毒多瘤病毒）infecting oligodendrocytes（少突胶质细胞少突胶质细胞）.It is considered the most commo

21、n clinical manifestation of JC virus infection in the brain.Epidemiology PML is strongly associated with immunosuppressed states,particularly AIDS but also can occur in transplant patients and.Incidence in non HIV settings are thought to be increasing.Primary PML developing in an immunocompetent pat

22、ient is very rare.In AIDS,it typically develops in patients with CD4 counts of 50-100 cells/uL,and is found in approximately 5%of autopsies of patients who died from AIDS.More recently it has also been associated with Natalizumab(Tysabri TM),an IgG monoclonal antibody used in the treatment of relaps

23、ing remitting multiple sclerosis Clinical presentation Patients with PML present with various neurological symptoms.It typically spares the optic nerve and the spinal cord.The most frequently encoutered symptoms include:altered mental status motor deficits limb and gait ataxia visual symptoms(diplop

24、ia&hemianopia)seizure(as PML can also involve the grey matter)The final diagnosis is established with brain biopsy(specificity:100%,sensitivity:65-95%).Pathology Lesions tend to have a confluent,bilateral but asymmetrical cerebral involvement.Lesions were distributed throughout the brain,including t

25、he brain stem and basal ganglia.While the condition invariably involves white matter,lesions can also involve grey matter.Histology reveals demyelinating plaques involving the subcortical U-fibers with sparing of the cortex and deep gray matter.Other findings include infected oligodendrocytes with e

26、nlarged amphophilic nuclei located at the periphery of the lesions,macrophages containing phagocytosed cellular debris and myelin,and reactive gliosis with enlarged astrocytes Radiographic features CT Asymmetric focal zones of low attenuation involving the peri-ventricular and sub-cortical white mat

27、ter.This is in distinction to the more symmetrical hypo-attenuation seen in HIV encephalopathy.MRI Typically seen as multifocal,asymmetric peri-ventricular and sub-cortical involvement.There is little or no mass effect.The U-fibers are commonly involved.T1:involved regions are usually hypo-intense T

28、2:involved regions are hyper-intense T1 C+(Gd):typically there is no enhancement,however if present it may be associated with improved survival MR spectroscopy:according to one study spectra of PML lesions were characterised by significantly reduced NAA,lactate presence,and by significantly increase

29、d Cho and lipids compared with control group values Treatment and prognosis Prognosis is generally is poor with an inexorable neurologic decline leading to coma and death occurring in the majority of patients with PML.If untreated,PML is usually fatal within 1 year.Treatment with highly active antiretroviral therapy(HAART)may prolong survival.Some reports also state some benefit with cytarabine.弓形纤维弓形纤维短联合纤维束短联合纤维束