Neuropathologic correlates of leuko-araiosis

Imaging Markers of Vascular Brain Health: Quantification, Clinical Implications, and Future Directions

Cerebrovascular disease (CVD) manifests through a broad spectrum of mechanisms that negatively impact brain and cognitive health. Oftentimes, CVD changes (excluding acute stroke) are insufficiently considered in aging and dementia studies which can lead to an incomplete picture of the etiologies contributing to the burden of cognitive impairment. Our goal with this focused review is 3-fold. First, we provide a research update on the current magnetic resonance imaging methods that can measure CVD lesions as well as early CVD-related brain injury specifically related to small vessel disease. Second, we discuss the clinical implications and relevance of these CVD imaging markers for cognitive decline, incident dementia, and disease progression in Alzheimer disease, and Alzheimer-related dementias. Finally, we present our perspective on the outlook and challenges that remain in the field. With the increased research interest in this area, we believe that reliable CVD imaging biomarkers for aging and dementia studies are on the horizon.

The potential role of leukoaraiosis in remodeling the brain network to buffer cognitive decline: a Leukoaraiosis And Disability study from Alzheimer's Disease Neuroimaging Initiative

Background

Leukoaraiosis (LA) is a phenomenon of the brain that is often observed in elderly people. However, little is known about the role of LA in cognitive impairment in neurodegeneration and disease. This cross-sectional, retrospective Leukoaraiosis And Disability (LADIS) study aimed to characterize the relationship between brain white matter connectivity properties with LA ratings in patients with Alzheimer's disease (AD) as compared with age-matched cognitively normal controls.

Methods

Patients with AD (n=76) and elderly individuals with normal cognitive (NC) function (n=82) were classified into 3 groups, LA1, LA2, and LA3, according to the rating of their white matter changes (WMCs). Diffusion tensor imaging (DTI) data were analyzed by quantifying and comparing the white matter connectivity properties and gray matter (GM) volume of brain regions of interest (ROIs).

Results

The rich-club network properties in the AD LA1 and LA2 groups showed significant patterns of disrupted peripheral regions and reduced connectivity compared to those in the NC LA1 and LA2 groups, respectively. However, the rich-club network properties in the AD LA3 group showed similar patterns of disrupted peripheral regions and reduced connectivity compared to those in the NC LA3 group, despite there being significant hippocampal and amygdala atrophic differences between AD patients and NC elders. Compared to the NC LA1 group, the characteristic path length of white matter fiber connectivity in the NC LA3 group was significantly increased, and the brain's global efficiency, clustering coefficient, and network connectivity strength were significantly reduced (P<0.05, respectively). However, no significant differences (P>0.05) were observed in characteristic path length, reduced global efficiency, or the clustering coefficient between the NC LA3 and AD LA1 groups, or between the NC LA3 and AD LA2 groups.

Conclusions

Our findings offer some insights into a potential role of LA in cognitive impairment that may predict the development of disability in older adults. The occurrence of LA, an intermediate degenerative change, during neurodegeneration and disease may potentially lead to the remodeling of the brain network through brain plasticity. LA, therefore, representing a possible compensatory mechanism to buffer cognitive decline.

Doppler Resistivity and Cerebral Small Vessel Disease: Hemodynamic Structural Correlation and Usefulness for the Etiological Classification of Acute Ischemic Stroke

INTRODUCTION AND GOAL

Lacunar stroke is defined as an <1.5 cm diameter infarct located in the territory of a perforating artery, that is not accessible for direct study using conventional imaging techniques. Diagnosis requires exclusion of other causes. It usually occurs in the context of chronic cerebral small vessel disease, which can be suspected during the neurosonography study in the form of high pulsatility [PI] or resistance index [RI]. Clinical research was performed to confirm that PI and RI correlate with cerebral small vessel lesion burden and to determine whether these parameters are useful for supporting a lacunar origin (LO) in acute stroke.

MATERIAL AND METHODS

We prospectively recorded internal carotid artery resistivity and the Fazekas score for all patients with acute ischemic stroke who met inclusion but not exclusion criteria over a 6-month period.

RESULTS

The study population comprised 74 patients. A correlation was observed between the Fazekas score and resistivity. Both parameters predicted a LO, with an area under the curve of .78 and .696, respectively. The optimal cut-offs were PI = .96/RI = .58 for screening (sensitivity, 96%) and PI = 1.46/RI = .83 for confirmation (specificity, 89%).

CONCLUSIONS

Doppler ultrasound is a useful technique for determining the LO of acute stroke.

Diabetes and neurodegeneration in the brain

Although an association between diabetes mellitus (DM) and cognitive dysfunction has been recognized for a century, it is often not considered as a complication of DM and remains under-recognized. Cognitive dysfunction, usually present as mild cognitive impairment, can occur with either type 1 or type 2 DM. Both forms of DM contribute to accelerated cerebral atrophy and to the presence of heightened white matter abnormalities. These effects are noted most at the two extremes of life, in childhood and in the advanced years. The cognitive spheres most affected include attention and executive function, processing speed, perception, and memory. Although DM is unlikely to lead to frank dementia, its ability to exacerbate existing neurodegenerative processes, such as Alzheimer disease, will impact tremendously upon our society in the upcoming decades as our population ages. This chapter describes the clinical impact of DM upon the brain, along with discussion of the potential therapeutic avenues to be discovered in the coming decades. We need to prepare for better preventative and therapeutic management of this cerebral neurodegenerative condition.

Gait dyspraxia as a clinical marker of cognitive decline in Down syndrome: A review of theory and proposed mechanisms

Down syndrome (DS) is the most common genetic cause of intellectual disability in children. With aging, DS is associated with an increased risk for Alzheimer's disease (AD). The development of AD neuropathology in individuals with DS can result in further disturbances in cognition and behavior and may significantly exacerbate caregiver burden. Early detection may allow for appropriate preparation by caregivers. Recent literature suggests that declines in gait may serve as an early marker of AD-related cognitive disorders; however, this relationship has not been examined in individuals with DS. The theory regarding gait dyspraxia and cognitive decline in the general population is reviewed, and potential applications to the population with individuals with DS are highlighted. Challenges and benefits in the line of inquiry are discussed. In particular, it appears that gait declines in aging individuals with DS may be associated with known declines in frontoparietal gray matter, development of AD-related pathology, and white matter losses in tracts critical to motor control. These changes are also potentially related to the cognitive and functional changes often observed during the same chronological period as gait declines in adults with DS. Gait declines may be an early marker of cognitive change, related to the development of underlying AD-related pathology, in individuals with DS. Future investigations in this area may provide insight into the clinical changes associated with development of AD pathology in both the population with DS and the general population, enhancing efforts for optimal patient and caregiver support and propelling investigations regarding safety/quality of life interventions and disease-modifying interventions.

Cerebral hypoperfusion induces cortical watershed microinfarcts which may further aggravate cognitive decline in Alzheimer's disease

Increasing number of data, including the existence of common risk factors, indicate an association between cerebrovascular disease and Alzheimer's disease (AD). AD is known to be often associated with cerebral hypoperfusion. Recent histopathological evidence showed a significant association between watershed cortical microinfarcts and AD indicating that cerebral hypoperfusion induces not only white matter damage, known as leuko-araiosis, but cortical border zone infarcts as well, further aggravating the degenerative process and worsening dementia. In late stages of Alzheimer's disease--in cases with neuropathologically confirmed definite AD--the occurrence of watershed cortical microinfarcts was ten times higher than in aged matched control cases. Congophilic angiopathy and perturbed hemodynamic factors were found to be important factors in the genesis of watershed microinfarcts. To consider the vulnerability of the cerebral blood flow and the perturbed cortical vascular network in AD is important. Neuroleptic and sedative treatments frequently employed in AD may further accentuate cerebral hypoperfusion by decreasing blood pressure. Therefore, to treat and prevent arterial hypotension and maintain cerebral perfusion at an appropriate level in AD is essential.

Clinically asymptomatic vascular brain injury: a potent cause of cognitive impairment among older individuals

Cerebrovascular risk factors and stroke are highly prevalent with advancing age, and stroke may be more common than Alzheimer's disease, particularly among older men. While stroke mortality continues to decline, the prevalence of individuals with various vascular risk factors continues to rise and many are undiagnosed or undertreated. Asymptomatic cerebrovascular brain injury that includes asymptomatic brain infarction and white matter hyperintensities as well as accelerated brain atrophy is even more frequent than clinical stroke. Moreover, the impact of cerebrovascular risk factors on brain injury appears to begin in middle life and additively increases the likelihood of later life dementia. This review focuses on the use of neuroimaging and genetics to understand the impact of asymptomatic vascular risk factors on the trajectories of cognitive aging as well as incident cognitive impairment, stroke, and mortality. Results of this review emphasize the need for early detection and treatment of vascular risk factors to improve the cognitive health of our rapidly aging population.

White matter lesions and brain gray matter volume in cognitively normal elders

Cerebral white matter lesions (WMLs) reflect small vessel disease, are common in elderly individuals, and are associated with cognitive impairment. We sought to determine the relationships between WMLs, age, gray matter (GM) volume, and cognition in the Cardiovascular Health Study (CHS). From the Cardiovascular Health Study we selected 740 cognitively normal controls with a 1.5 T magnetic resonance imaging (MRI) scan of the brain and a detailed diagnostic evaluation. WML severity was determined using a standardized visual rating system. GM volumes were analyzed using voxel-based morphometry implemented in the Statistical Parametric Mapping software. WMLs were inversely correlated with GM volume, with the greatest volume loss in the frontal cortex. Age-related atrophy was observed in the hippocampus and posterior cingulate cortex. Regression analyses revealed links among age, APOE*4 allele, hypertension, WMLs, GM volume, and digit symbol substitution test scores. Both advancing age and hypertension predict higher WML load, which is itself associated with GM atrophy. Longitudinal data are needed to confirm the temporal sequence of events leading to a decline in cognitive function.

Age-related changes in white matter lesions, hippocampal atrophy, and cerebral microbleeds in healthy subjects without major cerebrovascular risk factors

Although cumulative evidence indicates that risk factors for arteriosclerosis have an impact on age-related changes in brain pathology, the influence of aging without major risk factors on changes in brain structures has not yet been fully elucidated. We used magnetic resonance imaging (MRI) to study how aging affects structural changes in the brain (eg, white matter lesions, hippocampal atrophy [HA], microbleeds) in normal subjects without major risk factors for cerebrovascular diseases. We studied 1108 subjects who underwent voluntary brain screening and had no cerebrovascular risk factors, such as hypertension, diabetes mellitus, or hyperlipidemia. We examined the conventional and T2-weighted MRI to define white matter hyperintensities, HA, and cerebral microbleeds in addition to all physical parameters, blood biochemical data, and neuropsychiatric symptoms. We found that the prevalence of white matter lesions and HA increased significantly with age (P < .001). Logistic analysis showed that periventricular hyperintensity was significantly related to age (P < .0001) and depressive state (P < .01). A linear relation was found between white matter lesions and HA (P < .05). Cerebral microbleeds also increased with age, and their presence was associated with HA (P < .001). White matter lesions, HA, and cortical microbleeds were associated with one another in healthy elderly subjects, and these changes were affected by the aging process independent of any cerebrovascular risk factors. Cerebral amyloid angiopathy may underlie these age-related brain changes.

CT perfusion quantification of small-vessel ischemic severity

BACKGROUND AND PURPOSE

Cerebral blood flow (CBF) abnormalities are previously demonstrated in white matter disease. A gradation of change may exist between patients with mild and more severe white matter disease. An association between blood brain barrier dysfunction, increasing age and white matter disease is also suggested. The purpose of this study was to quantify and correlate white matter disease severity and CT perfusion (CTP)-derived CBF and to determine whether permeability surface abnormality increases with white matter disease severity.

MATERIALS AND METHODS

One hundred twenty patients with strokelike symptoms underwent CTP and MR imaging. Of these, 35 patients (15 women, 20 men; age, 66 +/- 15.7 years) with rapidly resolving symptoms and normal imaging characteristics consistent with transient ischemic attack were retrospectively reviewed and constituted the study cohort. Two blinded neurologists rated white matter severity, assigning age-related white matter change (ARWMC) scores. Patients were dichotomized a priori into mild and moderate-to-severe. CBF, cerebral blood volume (CBV), mean transit time (MTT), and permeability surface product maps were calculated for periventricular and subcortical white matter regions and average white and gray matter. Associations with white matter severity were tested by uni- and multivariate logistic regression analyses. Receiver operating characteristic analysis was performed.

RESULTS

White matter disease was mild in 26 patients and moderate-to-severe in 9. Age was associated with increased likelihood of having moderate-to-severe white matter disease (P = .02). ARWMC correlated with subcortical (r = -0.50, P < .001) and average CBF (r = -0.55, P < .001). White matter severity was associated with subcortical (P = .03) and average (P = .03) white matter CBF, with a trend toward periventricular white matter CBF (P = .05). Uni- and multivariate analysis controlling for the confounding effect of age demonstrated significant association between white matter severity and subcortical (P = .032) white matter CBF. Area under the curve was 0.82. No permeability surface abnormality was found.

CONCLUSIONS

CTP-derived subcortical white matter CBF is independently associated with white matter disease severity.

Clinical utility of evaluating intracranial artery stenosis and silent brain infarction to predict the presence of subclinical coronary artery disease in ischemic stroke patients

OBJECTIVE

We have recently reported the prevalence of subclinical cardiovascular diseases and the association between the presence of subclinical coronary artery disease (CAD) and vascular risk factors in ischemic stroke patients. The relationship between the presence of subclinical CAD and elements of brain ischemia including intracranial artery stenosis, silent brain infarction (SBI), and white matter lesions remains unclear. We determined the usefulness of elements of brain ischemia to predict the presence of subclinical CAD in ischemic stroke patients.

METHODS

The study group comprised 100 patients with first-ever ischemic stroke who had no history of CAD. Intracranial artery stenosis on magnetic resonance angiography and SBI and white matter lesions on magnetic resonance imaging were investigated in comparison with CAD defined as > or =50% stenosis on coronary computed tomographic angiography.

RESULTS

Thirty-six patients had subclinical CAD. Intracranial artery stenosis (78.1% vs 35.1%, p<0.0001) and SBI (69.4% vs 46.9%, p=0.03) were more prevalent in patients with subclinical CAD. Of the patients with both intracranial artery stenosis and SBI, 61% had subclinical CAD. Multiple regression analyses showed that the presence of subclinical CAD was independently associated with intracranial artery stenosis; <50% stenosis (OR 8.01 95%CI 2.02 to 31.9; p<0.01), > or =50% stenosis (OR 19.5 95%CI 2.77 to 137.4; p<0.01), and multiple SBI (OR 3.85 95%CI 1.23 to 12.0; p<0.05).

CONCLUSION

The evaluation of intracranial artery stenosis and SBI may be useful to identify ischemic stroke patients at high risk for subclinical CAD.

Clinical and neuropsychological features associated with structural imaging patterns in patients with mild cognitive impairment

AIM

To describe the clinical and neuropsychological features of mild cognitive impairment (MCI) patients with medial temporal atrophy (MTA), white matter hyperintensities (WMH), both, and neither and to assess whether the rate of progression differs among groups.

METHODS

Ninety-five MCI patients were divided into 4 groups based on the presence of MTA and WMH: 29 were MTA- WMH-, 11 MTA- WMH+, 23 MTA+ WMH-, and 32 MTA+ WMH+. MCI patients were compared with 30 normal subjects. MTA and WMH were assessed with MR-based visual rating scales. Subjects underwent an extensive clinical and neuropsychological investigation. Fifty-six underwent follow-up evaluation.

RESULTS

MTA- WMH- had relatively good neuropsychological performance, little vascular and physical comorbidity. MTA- WMH+ performed poorly only on executive neuropsychological tests. MTA+ WMH- patients had poor neuropsychological performances (mainly on memory tests), high physical and vascular comorbidity. MTA+ WMH+ were impaired in neuropsychological performances, had a high number of physical diseases and severe vascular comorbidity. On follow-up, 25% of MTA+ WMH- and 32% of MTA+ WMH+ and none in MTA- WMH- and in MTA- WMH+ converted to dementia (p = 0.05, log rank test).

CONCLUSION

Structural neuroimaging can identify subgroups of MCI patients with specific clinical and neuropsychological features.

The enigma of vascular cognitive disorder and vascular dementia

The prevalence, morphology and pathogenesis of vascular dementia (VaD), recently termed vascular cognitive impairment, are a matter of discussion, and currently used clinical diagnostic criteria show moderate sensitivity (average 50%) and variable specificity (range 64-98%). In Western clinic-based series, VaD is suggested in 8-10% of cognitively impaired aged subjects. Its prevalence in autopsy series varies from 0.03 to 58%, with reasonable values of 8-15%, while in Japan it is seen in 22-35%. Neuropathologic changes associated with cognitive impairment include multifocal and/or diffuse disease and focal lesions: multi-infarct encephalopathy, white matter lesions or arteriosclerotic subcortical (leuko)encephalopathy, multilacunar state, mixed cortico-subcortical type, borderline/watershed lesions, rare granular cortical atrophy, post-ischemic encephalopathy and hippocampal sclerosis. They result from systemic, cardiac and local large or small vessel disease. Recent data indicate that cognitive decline is commonly associated with widespread small ischemic/vascular lesions (microinfarcts, lacunes) throughout the brain with predominant involvement of subcortical and functionally important brain areas. Their pathogenesis is multifactorial, and their pathophysiology affects neuronal networks involved in cognition, memory, behavior and executive functioning. Vascular lesions often coexist with Alzheimer disease (AD) and other pathologies. Minor cerebrovascular lesions, except for severe amyloid angiopathy, appear not essential for cognitive decline in full-blown AD, while both mild Alzheimer pathology and small vessel disease may interact synergistically. The lesion pattern of "pure" VaD, related to arteriosclerosis and microangiopathies, differs from that in mixed-type dementia (AD with vascular encephalopathy), more often showing large infarcts, which suggests different pathogenesis of both types of lesions. Due to the high variability of cerebrovascular pathology and its causative factors, no validated neuropathologic criteria for VaD are available, and a large variability across laboratories still exists in the procedures for morphologic examination and histology techniques.

VITA study: white matter hyperintensities of vascular and degenerative origin in the elderly

The etiology of white matter hyperintensities (WMH) seen on T2-weighted cranial magnetic resonance images is a matter of debate. We investigated deep and periventricular WMH in the brains of a community-based cohort of 532 subjects aged 75-76 years. The objective of this study was to determine whether WMH at age of 75 years were associated rather with vascular factors than with degenerative factors. Arterial hypertension treated with antihypertensive drugs favored WMH, and WMH were found more frequently in subjects with focal vascular lesions. Additionally, we found significant associations between both, deep white matter and periventricular hyperintensities, and focal atrophy of medial temporal lobe structures. The odds ratio for deep WMH in subjects with more severe medial temporal atrophy was 4.4 (95%-CI: 1.9-9.8) that for periventricular hyperintensities was 3.9 (95%-CI: 1.7-8.8). These findings might indicate that not only vascular factors alone but also degenerative factors favor the occurrence of WMH after the age of 75 years.

Family-based association study of matrix metalloproteinase-3 and -9 haplotypes with susceptibility to ischemic white matter injury

Susceptibility to ischemic damage to the subcortical white matter of the brain has a strong genetic basis. Dysregulation of matrix metalloproteinases (MMPs) contributes to loss of cerebrovascular integrity and white matter injury. We investigated whether sequence variation in the genes encoding MMP3 and MMP9 is associated with variation in leukoaraiosis volume, determined by magnetic resonance imaging, in non-Hispanic whites and African-Americans using family-based association tests. Seven hundred and fifty-six white and 671 African-American individuals from sibships ascertained through two or more siblings with hypertension were genotyped for 7 and 8 haplotype-tagging polymorphisms in the MMP3 and MMP9 genes, respectively. MMP3 sequence variation was significantly associated with variation in leukoaraiosis volume in Whites. Two common haplotypes with opposing relationships to leukoaraiosis volume were identified. MMP9 sequence variation was also significantly associated with variation in leukoaraiosis volume in both African-Americans and Whites. Different haplotypes contributed to these associations in the two racial groups. These findings add to the growing body of evidence from animal models and human clinical studies suggesting a role of MMPs in ischemic white matter injury. They provide the basis for further investigation of the role of these genes in susceptibility and/or progression to clinical disease.

Clinical significance of corpus callosum atrophy in a mixed elderly population

Corpus callosum (CC) is the main tract connecting the hemispheres, but the clinical significance of CC atrophy is poorly understood. The aim of this work was to investigate clinical and functional correlates of CC atrophy in subjects with age-related white matter changes (ARWMC). In 569 elderly subjects with ARWMC from the Leukoaraiosis And DISability (LADIS) study, the CC was segmented on the normalised mid-sagittal magnetic resonance imaging (MRI) slice and subdivided into five regions. Correlations between the CC areas and subjective memory complaints, mini mental state examination (MMSE) score, history of depression, geriatric depression scale (GDS) score, subjective gait difficulty, history of falls, walking speed, and total score on the short physical performance battery (SPPB) were analyzed. Significant correlations between CC atrophy and MMSE, SPPB, and walking speed were identified, and the CC areas were smaller in subjects with subjective gait difficulty. The correlations remained significant after correction for ARWMC grade. In conclusion, CC atrophy was independently associated with impaired global cognitive and motor function in subjects with ARWMC.

Contributors to white matter damage in the frontal lobe in Alzheimer's disease

Abnormalities of cerebral white matter are present in a majority of patients with Alzheimer's disease (AD) and probably contribute to motor dysfunction and cognitive impairment. The white matter abnormalities are usually attributed to degenerative vascular disease and cerebral amyloid angiopathy (CAA) but the evidence is scanty or inconclusive. In the present study we examined sections of frontal lobe from 125 autopsy-confirmed cases of AD and assessed the relationship of degenerative large and small vessel disease, CAA, parenchymal Abeta load and APOE genotype, to several objective measures of white matter damage: extent of immunolabelling for glial fibrillary acidic protein (GFAP), axonal accumulation of amyloid precursor protein (APP), axon density in superficial and deep white matter, and intensity of staining for myelin. We found no association between atherosclerosis, arteriolosclerosis, CAA or APOE genotype and white matter damage. However, labelling of white matter for GFAP correlated strongly with the parenchymal Abeta load (P = 0.0003) and with APP accumulation (P = 0.008). Our findings suggest that severity of frontal white matter damage in AD is closely related to parenchymal Abeta load and that in most cases the contribution of degenerative vascular disease, CAA and APOE is relatively minor.

Cerebral white matter hyperintense lesions are associated with unstable carotid plaques

OBJECTIVES

The aim of this study was to determine whether unstable carotid plaques, a known risk factor for cerebral emboli, are associated with cerebral white matter lesions.

METHODS

Seventy-one symptomatic patients undergoing magnetic resonance imaging prior to carotid endarterectomy for high grade carotid stenosis were included in this study. The number and volume of white matter hyperintense lesions (WMHL) on fluid attenuated inversion recovery brain scans were compared according to the morphology of carotid plaque based upon the American Heart Association (AHA) histological classification.

RESULTS

Of the 57 patients who had good quality brain scans and non-fragmented carotid plaques, 15 plaques were defined as stable (type V) and 42 as unstable (type VI). After adjustment for the major risk factors affecting WMHL, unstable carotid plaques were found to be associated with more WMHL in the ipsilateral cerebral hemisphere than stable plaques (transformed means 2.50+/-1.2 vs. 1.53+/-1.1, p=0.016), however, there was only a trend towards larger WMHL volumes (p=0.079).

CONCLUSIONS

The observed association between unstable carotid plaques and the number of white matter lesions suggest that thromboembolic plaque activity may contribute to the development of leukoaraiosis, in particular smaller individual lesions. Larger studies are warranted to confirm this finding and explore the potential clinical impact for selecting candidates for carotid endarterectomy.

Atherosclerosis, vascular amyloidosis and brain hypoperfusion in the pathogenesis of sporadic Alzheimer's disease

We postulate that severe atherosclerotic occlusion of the circle of Willis and leptomeningeal arteries is an important factor in the pathogenesis of some sporadic Alzheimer's disease (AD) cases. These arterial stenoses are complicated by an overwhelming amyloid accumulation in the walls of leptomeningeal and cortical arteries resulting in a significant decrease in perfusion pressure and consequent ischemia/hypoxia of the brain tissue. We also propose that the distal areas of the white matter (WM) will be the first affected by a lack of oxygen and nutrients. Our hypotheses are supported by the following observations: (1) the number of stenoses is more frequent in AD than in the control population (p = 0.008); (2) the average index of occlusion is greater in AD than in the control group (p < 0.00001); (3) the index of stenosis and the total number of stenoses per case are positively correlated (R = 0.67); (4) the index of stenosis correlates with the neuropathological lesions of AD and with the MMSE psychometric test; (5) the number and degree of atherosclerosis of the anterior, middle and posterior cerebral arteries is more severe in cases of AD than in the control population; (6) atherosclerosis severity is apparently associated with the severity of the vascular amyloidosis; (7) the WM rarefaction correlates with the severity of the atherosclerosis and vascular amyloidosis; (8) the total cell count and microvessel count in the areas of WM rarefaction correlate with the neuropathological lesions of AD and with the MMSE score. Our data strongly suggest that severe hemodynamic disturbances contribute to sporadic AD and support the numerous observations indicating cardiovascular system participation in the pathogenesis of these dementias.

Cerebral white matter lesions and hypertension status in the elderly Korean: the Ansan Study

There is evidence of an association of hypertension with white matter lesions (WMLs), leukoaraiosis, in the human brain in the United States, Europe and Japan. However, no study on this association has been reported in Korea. Community-dwelling elderly subjects aged over 61 years were randomly selected from samples of the Ansan Health Study, while their blood pressures (BPs) were measured using a highly standardized protocol. Hypertension was defined as a systolic BP> or =140 mmHg or a diastolic BP> or =90 mmHg or as reported treatment with hypertensive medication, and further subclassified with respect to its subtypes and control status. WMLs were determined by a 1.5-T MRI scan and further categorized into five subgroups with respect to its severity. Hypertension status, such as uncontrolled hypertension even after antihypertensive medication (adjusted odd ratio [OR]=6.07; 95% CI, 2.08-17.78), isolated systolic hypertension before medication (OR=2.66; 95% CI, 1.08-6.57), and hypertension before medication (OR=2.55; 95% CI, 1.19-5.46) were significantly and independently correlated with the presence and severity of WMLs. Advancing age (OR=1.76; 95% CI, 1.38-2.25), lacunar infarction (OR=3.19; 95% CI, 1.83-5.58), and cigarette smoking (OR=1.10; 95% CI, 1.03-1.18) were significantly related to the presence and severity of WMLs. Regular and tight control for hypertension should be exercised to prevent WMLs among the elderly with hypertension.

Cerebral amyloid angiopathy and thrombolysis-related intracerebral haemorrhage

Intracerebral haemorrhage is a complication of thrombolytic therapy for acute myocardial infarction, pulmonary embolism, and ischaemic stroke. There is increasing evidence that cerebral amyloid angiopathy (CAA), which itself can cause haemorrhage (CAAH), may be a risk factor for thrombolysis-related intracerebral haemorrhage. CAAH and thrombolysis-related intracerebral haemorrhage share some clinical features, such as predisposition to lobar or superficial regions of the brain, multiple haemorrhages, increasing frequency with age, and an association with dementia. In vitro work showed that accumulation of amyloid-beta peptide causes degeneration of cells in the walls of blood vessels, affects vasoactivity, and improves proteolytic mechanisms, such as fibrinolysis, anticoagulation, and degradation of the extracellular matrix. In a mouse model of CAA there is a low haemorrhagic threshold after thrombolytic therapy compared with that in wild-type mice. To date only a small number of anecdotal clinicopathological relations have been reported; neuroimaging advances and further study of the frequency and role of CAA in patients with thrombolysis-related intracerebral haemorrhage are required.

Brain tissue microarrays in dementia research: white matter microvascular pathology in Alzheimer's disease

Tissue microarrays (TMA) consist of up to 1000 cylindrical tissue cores from different donor paraffin blocks relocated into one recipient block, allowing for efficient histopathological studies by fluorescence in situ hybridization, RNA in situ hybridization or immunohistochemistry. On the background of the increasing interest of the TMA technique in cancer research and the suggestion of its application also in studies of non-neoplastic intracranial disorders, the technique was applied to pathologic white matter in AD brains. Eight cases with AD and concomitant white matter pathology were neuropathologically diagnosed on whole brain coronal slides. The TMA technique was used to grade severity of white matter pathology and to quantify small vessels with traditional staining and immunohistochemical markers. These measurements were compared with the whole brain neuropathological assessment. The technique produced good results with preserved tissue structures as confirmed by the whole brain evaluation. Severity of white matter pathology evaluated on the TMA cores correlated negatively with small vessel quantities, and statistically significant differences in vessel quantities paralleled different grades of white matter pathology. It is concluded that the TMA technique could be further utilized in studies of dementing disorders, and may have its advantages in large, clinically well-characterized materials (e.g. in quantitative mapping of white matter changes).

Vascular-ischemic dementia: an update

Both the clinical criteria and morphologic substrates of dementia resulting from cerebrovascular disease and its relation to Alzheimer disease and other age-related brain changes are controversial. In clinical and autopsy studies in the Western world the prevalence of vascular-ischemic dementia (VID) is around 7-10%, while vascular cognitive impairment without dementia is much more frequent and the risk of poststroke dementia is increased in patients with prestroke cognitive decline. In contrast to previous suggestions that VID was largely the result of large hemispheral infarcts, according to recent studies, it is most commonly associated with widespread small ischemic or vascular lesions (microinfarcts, lacunes) throughout the CNS with predominant subcortical lesions in the basal ganglia and white matter or in strategically important brain regions (thalamus, hippocampus). The lesion pattern of rare "pure" VID, which is related to arteriolosclerotic and hypertensive microangiopathy, differs from that in mixed type dementia (Alzheimer disease and cerebrovascular lesions) that more often shows larger hemispheral infarcts. Another form of VID that is not infrequent in very old subjects is hippocampal sclerosis, a selective damage to the hippocampus that is often accompanied by multiple other cerebrovascular lesions. Both, mild Alzheimer type pathology and small vessel disease-associated subcortical vascular pathology appear to be common and may interact in causing cognitive decline, but the impact of cerebrovascular lesions on cognitive impairment and dementia needs to be further elucidated.

A new rating scale for age-related white matter changes applicable to MRI and CT

BACKGROUND AND PURPOSE

MRI is more sensitive than CT for detection of age-related white matter changes (ARWMC). Most rating scales estimate the degree and distribution of ARWMC either on CT or on MRI, and they differ in many aspects. This makes it difficult to compare CT and MRI studies. To be able to study the evolution and possible effect of drug treatment on ARWMC in large patient samples, it is necessary to have a rating scale constructed for both MRI and CT. We have developed and evaluated a new scale and studied ARWMC in a large number of patients examined with both MRI and CT.

METHODS

Seventy-seven patients with ARWMC on either CT or MRI were recruited and a complementary examination (MRI or CT) performed. The patients came from 4 centers in Europe, and the scans were rated by 4 raters on 1 occasion with the new ARWMC rating scale. The interrater reliability was evaluated by using kappa statistics. The degree and distribution of ARWMC in CT and MRI scans were compared in different brain areas.

RESULTS

Interrater reliability was good for MRI (kappa=0.67) and moderate for CT (kappa=0.48). MRI was superior in detection of small ARWMC, whereas larger lesions were detected equally well with both CT and MRI. In the parieto-occipital and infratentorial areas, MRI detected significantly more ARWMC than did CT. In the frontal area and basal ganglia, no differences between modalities were found. When a fluid-attenuated inversion recovery sequence was used, MRI detected significantly more lesions than CT in frontal and parieto-occipital areas. No differences were found in basal ganglia and infratentorial areas.

CONCLUSIONS

We present a new ARWMC scale applicable to both CT and MRI that has almost equal sensitivity, except for certain regions. The interrater reliability was slightly better for MRI, as was the detectability of small lesions.

Do white matter changes contribute to the subsequent development of dementia in patients with mild cognitive impairment? A longitudinal study

OBJECTIVE

White matter lesions on brain CT or MRI are a frequent finding in patients with Alzheimer's disease. However, little is known about the prognostic significance of these changes in cognitively impaired individuals who are at risk for subsequent development of dementia. This study aims at investigating the potential impact of white matter lucencies (WML) on brain CT on the course of mild cognitive impairment.

PATIENTS AND METHODS

Twenty-seven patients (mean age 72, SD 4.03) with mild cognitive impairment (MCI) and no signs of cerebrovascular disease were prospectively examined. At their initial presentation, all patients underwent a structured interview for the diagnosis of dementia (SIDAM) and a brain CT. Linear measures of atrophy and visual ratings of white matter changes were performed. At follow-up (mean interval 29 months), these patients were re-examined with the SIDAM. Eight patients had developed dementia and met clinical criteria for Alzheimer's disease (crossover group).

RESULTS

Evaluation of the initial CT scans revealed significantly more frequent and extended white matter abnormalities and a higher degree of temporal lobe atrophy in the crossover group as compared to the cognitively stable group. In the crossover group, high WML severity initially was associated with a lesser degree of temporal lobe atrophy and higher global cognitive performance.

CONCLUSION

We conclude that WML play a role in the dementia process and that they might accelerate cognitive decline in individuals with mild cognitive impairment. WML should be included in prospective studies of MCI as potential predictor variables.

Dementia of Alzheimer type with and without multiple lacunar infarctions: evaluation of white matter lesions

The white matter lesions in dementia of Alzheimer type (DAT) with and without multiple lacunar infarctions were studied relative to a normal control group. The frequency and distribution of white matter (WM) lesions in DAT (22 cases; mean age +/- standard deviation (SD), 88.1 +/- 5.8), DAT with multiple lacunar infarctions (DAT + CVD, 18 cases; mean age +/- SD, 87.8 +/- 6.0), and in a normal control group (17 cases; mean age +/- SD, 85.2 +/- 4.8) were evaluated. The frequency of myelin pallor (frontal, parietal and occipital lobes) was significantly higher in the DAT + CVD group than in the other groups (DAT and controls). There was no significant difference in the frequency of myelin pallor between the DAT and control groups. Therefore, it was concluded that the WM lesions in DAT are the result of ischemia rather than wallerian degeneration.

Are genetic factors important in the aetiology of leukoaraiosis? Results from a memory clinic population

OBJECTIVE

To discover whether polymorphism in either the apolipoprotein E (ApoE) or angiotensin-converting enzyme (ACE) genes is associated with leukoaraiosis, white matter lesions visible on neuroimaging of the brain, which is commonly seen in dementia as well as some normal elderly subjects.

DESIGN

Prospective study of consecutive patients attending our memory disorders clinic, to examine the relationship between leukoaraiosis and polymorphism of the ApoE and ACE genes.

SETTING

Memory disorders clinic in Bristol, UK.

PATIENTS

182 patients attending the memory disorders clinic for investigation of possible dementia of whom 75% were suffering from dementia, 20% from memory impairment but no dementia and in 5% of whom a dementing illness was thought to be unlikely; 38% of all patients had visible white matter lesions and 16% had cerebral infarcts.

MEASURES

Patients and/or carers who agreed to participate in the study had their ACE and ApoE genotype determined and their brain CT/MRI scans were assessed by a neuroradiologist, blind to the result of the genotyping, for the presence or absence of white matter low attenuation.

RESULTS

There was a significant association between white matter lesions and the DD genotype (p < 0.05), but not the ApoE genotype. However, this relationship with the DD genotype was only significant for patients with a previous infarct.

CONCLUSION

Homozygosity of ACE gene deletion polymorphism is a risk factor for white matter lesions when it is associated with cerebral infarction. This suggests that it may be possible to identify subjects who are at greater risk of developing white matter lesions and are at risk of cognitive impairment and possibly dementia.

Giant cell arteritis in association with cerebral amyloid angiopathy: immunohistochemical and molecular studies

Giant cell arteritis (GCA) usually manifests as a transmural vascular infiltrate of mononuclear and multinucleated giant cells (MNGC). We describe six patients with GCA associated with severe cerebral amyloid angiopathy (CAA), all with cerebral hemorrhage or varying degrees of cerebral infarct, and histological evidence of Alzheimer's disease (cortical CAA often predominating over senile plaques and neurofibrillary tangles). One case showed mostly cortical involvement (with old microhemorrhages), and the others were primarily leptomeningeal (with involvement of the underlying cortex and extensive encephalomalacia of adjacent brain). Many vessels with CAA exhibited a pronounced adventitial and perivascular infiltrate of lymphocytes, histiocytes, and MNGC. Immunohistochemical staining showed deposition of beta/A4 peptide primarily in the thickened media of CAA vessels, and within the cytoplasm of MNGC--suggesting phagocytosis of insoluble peptide. Cystatin C antibody stained vascular amyloid and diffusely highlighted astrocytic and MNGC cytoplasm. HAM56-positive macrophages were frequently seen around amyloid-laden vessels. Anti-smooth muscle actin immunohistochemistry suggests the occurrence of medial destruction by amyloid, with relative preservation of intimal cells. Ultrastructural studies performed in one case confirmed the presence of intracytoplasmic amyloid in MNGC. The GCA seen in these cases of CAA most likely represents a foreign body response to amyloid proteins, causing secondary destruction of the vessel wall. DNA from brain tissues of five affected patients was examined to assess whether mutations were present in exon 17 of the APP gene or exon 2 of the cystatin C gene, a finding that might explain the foreign body giant cell response to amyloid proteins in these cases. However, restriction fragment mapping of amplified gene segments showed that previously described mutations were not present in these cases.

Changes in local cerebral blood flow by neuroactivation and vasoactivation in patients with impaired cognitive function

Imaging of local cerebral blood flow (lCBF) may serve as an important supplementary tool in the aetiological assessment of dementias. In early or preclinical disease, however, there are less characteristic changes in lCBF. In the present study it was investigated whether vasoactivation or neuroactivation may produce more pronounced local lCBF deficits. Local CBF was investigated by using technetium-99m hexamethylpropylene amine oxime and single-photon emission tomography (SPET) in 80 patients (50 with mild cognitive impairment and 30 with dementia of Alzheimer type (DAT), all without evidence of cerebrovascular disease) at rest (baseline) and during activation. In 31 studies patients underwent vasomotor activation with acetazolamide, while 62 studies were performed under cognitive challenge (neuroactivation by labyrinth task). Cortical activity relative to that of cerebellum increased significantly in a right temporal region and tended to increase in other cortical regions upon vasoactivation. In contrast, neuroactivation reduced cortical activity relative to that of cerebellum in several left and right temporal and in left parietal regions. Visual classification of SPET images of patients with probable DAT by three observers resulted in a reduction of the number of definitely abnormal patterns from 9/12 to 4/12 by vasoactivation and an increase from 10/18 to 15/18 by neuroactivation. Correspondingly, abnormal ratings in patients with mild cognitive dysfunction were reduced from 7/19 to 5/19 by vasoactivation and were increased from 12/21 to 18/21 by neuroactivation. In conclusion, vasoactivation does not enhance local relative perfusion deficits in patients with cognitive impairment of non-vascular aetiology, whereas neuroactivation by labyrinth task produces more pronounced local flow differences and enhances abnormal patterns in lCBF imaging.

Hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D): I--A review of clinical, radiologic and genetic aspects

Hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D) is an autosomal dominant disease caused by deposition of beta-amyloid in the leptomeningeal arteries and cortical arterioles, in addition to preamyloid deposits and amyloid plaques in the brain parenchyma. The disease is due to a point mutation at codon 693 of the amyloid precursor protein (beta PP) gene at chromosome 21. Since this point mutation is diagnostic for HCHWA-D, presymptomatic testing is feasible and offered, together with genetic counselling and psychological support, to subjects at risk. HCHWA-D is clinically characterized by recurrent strokes, in addition to dementia, which can occur after the first stroke but also preceding it. Radiological studies revealed focal lesions (hemorrhages, hemorrhagic and non-hemorrhagic infarctions) and diffuse white matter damage. Diffuse white matter hyperintensities on MRI are an early symptom of HCHWA-D since they have been found on MRI scans of subjects who had not suffered a stroke. The presence of the diagnostic point mutation makes HCHWA-D a useful model to study the effects of cerebral amyloid angiopathy in vivo. The characteristic pathological abnormalities and its implications for Alzheimer's disease will be discussed in Part II of this article.

Comparison of different diagnostic criteria for vascular dementia (ADDTC, DSM-IV, ICD-10, NINDS-AIREN)

BACKGROUND AND PURPOSE

Vascular dementia (VD) has been an ill-defined term thus far. Recently detailed criteria for the diagnosis of VD have been proposed (Alzheimer's Disease Diagnostic and Treatment Centers [ADDTC], 1992; Diagnostic and Statistical Manual of Mental Disorders, 4th edition [DSM-IV], 1994; International Classification of Diseases, 10th revision [ICD-10], 1992, 1993; and National Institute of Neurological Disorders and Stroke-Association Internationale pour la Recherche et l'Enseignement en Neurosciences [NINDS-AIREN], 1993). Until now the clinical feasibility of these diagnostic guidelines has not been evaluated.

METHODS

This study aimed to compare these criteria in an unselected sample of 167 elderly patients (mean age, 72.0 +/- 9.9 years) admitted with probable dementia.

RESULTS

The number of cases that could be classified as VD differed widely between the various diagnostic guidelines. According to DSM-IV criteria, 45 cases were diagnosed as VD. Twenty-one cases fulfilled the ICD-10 research criteria, but only 12 met the NINDS-AIREN criteria for VD. Twenty-three cases were classified as ischemic VD as defined by the ADDTC criteria. The concordance was very poor since only 5 cases met the criteria for VD of all diagnostic guidelines.

CONCLUSIONS

Our results show that the classification according to different diagnostic guidelines yields rather distinct groups of patients. The reasons responsible for these findings are as follows: (1) different criteria for dementia, (2) limitation to ischemic VD in the ADDTC criteria, (3) no further differentiation of VD into subtypes according to CT or MRI findings (DSM-IV), and (4) the multifactorial etiopathology of VD. Major diagnostic difficulties ensue from the very frequent cases with white matter lesions, since their etiology and classification remain widely unknown.

H-1 MR spectroscopic imaging of white matter signal hyperintensities: Alzheimer disease and ischemic vascular dementia

PURPOSE

To investigate the association of white matter signal hyperintensities (WMSHs) with changes in hydrogen-1 metabolites.

MATERIALS AND METHODS

T2-weighted magnetic resonance (MR) imaging and H-1 MR spectroscopic imaging were performed in 21 elderly control subjects without or with minimal WMSHs, eight elderly subjects with substantial WMSHs, 11 probable Alzheimer disease patients with WMSHs, and eight ischemic vascular dementia (IVD) patients with WMSHs. N-acetylaspartate (NAA), choline-containing metabolites (Cho), and creatine-containing metabolites (Cr) were analyzed.

RESULTS

Differences in regional metabolite levels were found within the supraventricular brain of elderly control subjects. In Alzheimer disease patients, extensive WMSHs showed a lower percentage of NAA and a higher percentage of Cho compared with contralateral normal-appearing white matter (NAWM); in IVD patients, extensive and large WMSHs were associated with a higher percentage of Cho and a lower percentage of Cr compared with contralateral NAWM.

CONCLUSION

Regional metabolite variation and the presence of WMSHs are important covariants that must be accounted for in analysis of MR spectroscopic data.

Protective effect of cyclosporin A on white matter changes in the rat brain after chronic cerebral hypoperfusion

BACKGROUND AND PURPOSE

Activation of glial cells and rarefaction of the white matter have been reported in rat brain after bilateral permanent occlusion of the common carotid arteries. Using this model, we investigated the effects of the immunosuppressant cyclosporin A on the activation of glial cells and the white matter rarefaction.

METHODS

Both common carotid arteries were ligated bilaterally in 40 male Wistar rats. Twenty-two of these rats received an intraperitoneal injection of cyclosporin A, and the remaining 18 received a vehicle-solution injection. Microglia/macrophages were investigated with immunohistochemistry for the major histocompatibility complex class I and II antigens as well as for leukocyte common antigen. Astroglia were examined with glial fibrillary acidic protein as a marker. Activation of glial cells and white matter rarefaction were then investigated from 7 to 30 days after the ligation.

RESULTS

In vehicle-treated animals, there was a persistent and extensive activation of both microglia/macrophages and astroglia in the white matter, including the optic nerve, optic tract, corpus callosum, internal capsule, and traversing fiber bundles of the caudoputamen. In cyclosporin A-treated rats, the number of activated microglia/macrophages was significantly reduced (P < .01) to approximately one fifth of that in vehicle-treated animals. Similarly, rarefaction of the white matter was much less intense in cyclosporin A-treated rats (P < .01).

CONCLUSIONS

Cyclosporin A suppressed both glial activation and white matter changes after chronic cerebral hypoperfusion. These results suggest that immunologic reaction may play a role in the pathogenesis of the white matter changes and that the present model may be useful in investigating the pathophysiology of white matter changes induced by chronic cerebral hypoperfusion.

The significance of cerebral white matter abnormalities 100 years after Binswanger's report. A review

BACKGROUND

Changes in the cerebral hemispheric white matter are detected with increasing frequency by CT and MRI among persons older than 60 years. The pathogenesis, clinical significance, and morphological substrate of these changes are incompletely understood. Patients who have such neuroimaging abnormalities are sometimes diagnosed with "Binswanger's disease," an eponym that has generated much confusion because of its imprecise meaning. The objectives of this study were to determine whether the term Binswanger's disease merits acceptance as a distinct clinicopathologic entity, to deduce the clinical significance of these white matter abnormalities from the analysis of appropriate publications, and to evaluate studies that correlate in vivo changes in the cerebral white matter with pathological features.

SUMMARY OF REVIEW

We evaluated Binswanger's original case description and, after conducting a Medline search, reviewed more than 160 publications, mostly in the English language, on the subject of white matter abnormalities detectable by currently used neuroimaging methods (ie, leukoaraiosis).

CONCLUSIONS

Binswanger's original description appears to be insufficient for the purpose of defining a new nosological entity. After evaluating the vaguely outlined pathological correlates described in a few of these subcortical cerebral leukoencephalopathies, we conclude that the clinical significance of leukoaraiosis remains incompletely defined. However, its frequency increases with age independent of other risk factors, and in nondemented subjects leukoaraiosis is associated with deficits in selected cognitive functions. Moreover, leukoaraiosis correlates with an increased risk for the subsequent development of strokes. We make specific suggestions for future studies that may help to clarify this topic.

Leukoaraiosis and cause of death: a five year follow up

The causes of death of 127 patients, who had undergone CT examination of the brain in 1989, were investigated. The CT was re-evaluated. Twenty five patients were excluded because of pathological findings on CT other than leukoaraiosis (LA), infarction, or their combination or, because of a specific known aetiology for LA. Of the remaining 102 patients, 25 had pure LA, 18 had pure infarction, 37 had LA combined with infarction (cLA), and 22 had a normal CT. The mean time between the CT and death was 1.8 (SD 1.5) years. A vascular cause of death was clearly associated with LA and with the severity of LA. Patients with pure LA had a vascular cause of death as often as those with pure infarction and those with LA combined with infarction. These groups differed significantly from each other when comparing the occurrence of cerebrovascular, cardiovascular and other vascular causes of death. The results suggest that LA on CT is more likely to be associated with a cardiovascular cause of death, and pure infarction is more often associated with a cerebrovascular death.

Some methodological issues in neuroradiological research in psychiatry

An outline is given of some of the methodological issues discussed in neuroradiological research on psychiatric illness. Strengths and shortcomings of magnetic resonance imaging (MRI) in depicting and quantifying brain structures are described. Temporal lobe anatomy and pathology are easily accessible to MRI, whereas limits on anatomical delineation hamper approaches to frontal lobe study. White matter hyperintense lesions are sensitively depicted by MRI, but specificity is limited. Distinction of vascular and primary degenerative dementia is considerably improved by CT and MRI analysis. Computed tomography (CT) and MRI have enhanced the understanding of treatable organic psychiatric disorders, e.g., normal pressure hydrocephalus. Subcortical and white matter pathology has been replicated in CT and MRI studies of late-onset psychiatric disorders, clinical overlap with cerebrovascular disease or neurodegeneration may be of import. Transcranial sonography findings of brainstem structural change specific to unipolar depression may contribute to the understanding of affective psychoses. Magnetic resonance spectroscopy and functional MRI are likely to stimulate psychiatric research in the future.

Diagnosis of vascular dementia: Consortium of Canadian Centres for Clinical Cognitive Research concensus statement

Interest in vascular causes for cognitive impairment is increasing, in recognition that such causes are common, and possibly preventable. This has led to attempts to better define vascular dementia and its natural history. Several sets of criteria for the diagnosis of vascular dementia have been proposed. We provide a brief overview of the background to the initiation of a Canadian consensus conference, established by the Consortium of Canadian Centres for Clinical Cognitive Research (C5R) and report the conclusions reached at that conference. To date, no one set of criteria is demonstrably superior to another; we have therefore not endorsed any of the competing sets, nor have we recommended our own. Instead we suggest that empiric studies are required to establish valid criteria. A diagnostic checklist, which combines existing criteria and additional data, is attached for clinicians wishing to participate in such studies.

Magnetic resonance imaging findings in Japanese encephalitis. White matter lesions

Ten patients with Japanese encephalitis diagnosed by serological criteria underwent magnetic resonance imaging (MRI) in axial and coronal sections. In 6, a second MRI study was done. The MRI findings were compared with the clinical outcome. Four patients died within several months of onset, 2 had sequelae such as hemiparesis and dementia, and the remaining 4 had no sequelae. In 9 of 10 patients, either diffuse or patchy white matter lesions were observed bilaterally, together with abnormalities in areas such as the thalamus, basal ganglia, and brainstem. For 3 patients who died or remained demented, the second MRI revealed extensive, diffuse white matter abnormalities. This study indicates that Japanese encephalitis can produce white matter involvement, although gray matter structures such as the thalamus, basal ganglia, and brainstem are more severely affected. The severity of these MRI lesions correlated with the clinical outcome.

[Contribution of morphological imaging in the diagnosis of dementia. I--Alzheimer disease]

In patients with Alzheimer's disease, morphological neuroimaging techniques usually reveal signs of global cerebral atrophy which gradually worsen over time and depends on age and severity of the cognitive decline. Because of the lack of artifacts and of a more appropriate angle, magnetic resonance imaging scans may visualize a prominent atrophy of the medial temporal lobes, including hippocampal structures. Hippocampal atrophy is relatively specific of Alzheimer's disease before 65 and is related to the severity of memory disorders. White matter changes in patients without cerebrovascular risk factors are not more severe in patients with presenile Alzheimer's disease than in age-matched controls. They are, however, more severe in patients with senile onset than in age-matched controls. These findings suggest that white matter changes in patients with senile onset are consistent with a diagnosis of Alzheimer's disease.