1、imaging and clinical 10,Leukoaraiosis(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 is
2、chemic 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
3、, increased 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
4、 lymphomas. Cerebral 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
5、disorganisation of vascular 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
6、 can be explained the relation 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. S
7、o suggested non-atheromatosis 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
8、are spot-like and are located in 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
9、 deep white matter. Stage IV: hyperintense 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 an
10、d arrows show SLA and PLA, respectively.,Leukoaraiosis in 1 region (frontal) marked by arrowAdvanced 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. M
11、RI scan shows: leukoaraiosis stage I, deep parietal lacunar infarct 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,
12、admitted for left hemiplegia suddenly occurred. Cerebral MRI scan shows 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,
13、with arterial hypertension, diabetes mellitus, peripheral arterial disease, gait abnormalities 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
14、left posterior cerebral arterial ischemic stroke in the last 3 years, admitted for right hemiparesis 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
15、 weighted and FLAIR are the same as in stage II in addition focal spot-like lesion of deep white 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 abnormalit
16、ies for some months, gait and memory diffi culties aggravated. Cerebral MRI scan shows: mixed brain atrophy, 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 ab
17、normalities for about one year. Cerebral MRI shows mixed brain atrophy and leukoaraiosis stage IV.,Stage IV: hyperintense 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 cap
18、s (C), thin lining (D), smooth halo (E), irregular periventricular WML (F), punctuate deep WML (G), deep WML beginning confluence (H), confluent 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
19、 frequently in patients with acute stroke. Stage III was in patients with chronic vascular lesions. Stage IV in our studied group was found in those with Binswanger disease. Severity of leukoaraiosis increases with age. Severity of neurologic symptoms is in direct proportion with severity of leukoar
20、aiosis Leukoaraiosis is a risk factor for cognitive decline, in our study this affect was accentuated due to association with brain atrophy in 66% of all cases. Presence of leukoaraiosis is associated with increased risk of stroke recurrence.,Progressive multifocal leukoencephalopathy (PML：进行性多灶性白质脑
21、病) is a demyelinating disease which results from the JC virus（多瘤病毒） infecting oligodendrocytes（少突胶质细胞）. It is considered the most common clinical manifestation of JC virus infection in the brain .EpidemiologyPML is strongly associated with immunosuppressed states, particularly AIDS but also can occu
22、r in transplant patients and . Incidence in non HIV settings are thought to be increasing. Primary PML developing in an immunocompetent patient 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
23、died from AIDS .More recently it has also been associated with Natalizumab (Tysabri TM), an IgG monoclonal antibody used in the treatment of relapsing remitting multiple sclerosis,Clinical presentationPatients with PML present with various neurological symptoms. It typically spares the optic nerve a
24、nd the spinal cord. The most frequently encoutered symptoms include :altered mental statusmotor deficitslimb and gait ataxiavisual symptoms (diplopia & hemianopia)seizure (as PML can also involve the grey matter) The final diagnosis is established with brain biopsy (specificity : 100%, sensitivity :
25、 65-95%).,Pathology Lesions tend to have a confluent, bilateral but asymmetrical cerebral involvement . Lesions were distributed throughout the brain, including the brain stem and basal ganglia. While the condition invariably involves white matter, lesions can also involve grey matter .Histology rev
26、eals demyelinating plaques involving the subcortical U-fibers with sparing of the cortex and deep gray matter. Other findings include infected oligodendrocytes with enlarged amphophilic nuclei located at the periphery of the lesions, macrophages containing phagocytosed cellular debris and myelin, an
27、d reactive gliosis with enlarged astrocytes,Radiographic features CT Asymmetric focal zones of low attenuation involving the peri-ventricular and sub-cortical white matter. This is in distinction to the more symmetrical hypo-attenuation seen in HIV encephalopathy.MRI Typically seen as multifocal, as
28、ymmetric 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 T2 : involved regions are hyper-intense T1 C+ (Gd) : typically there is no enhancement , however if present it may be associat
29、ed with improved survival,MR spectroscopy : according to one study spectra of PML lesions were characterised by significantly reduced NAA, lactate presence, and by significantly increased Cho and lipids compared with control group values Treatment and prognosis Prognosis is generally is poor with an
30、 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,短联合纤维束,
