Fundamental pathological lesions in vascular dementia

Neuroimaging determinants of cognitive impairment in the memory clinic: how important is the vascular burden?

While neurodegenerative and vascular neurocognitive disorder (NCD) often co-occur, the contribution of vascular lesions, especially stroke lesions identified on MRI, to global cognition in a real-life memory clinic population remains unclear. The main objective of this retrospective study was to determine NCD neuroimaging correlates: the GM atrophy pattern and vascular lesions (especially stroke lesion localization by voxel-based lesion-symptom mapping, VLSM) in a memory clinic. We included 336 patients with mild or major NCD who underwent cerebral MRI and a neuropsychological assessment. The GM atrophy pattern (obtained by voxel-based morphometry, VBM) and the stroke lesion localization (obtained by VLSM) associated with G5 z-score (a global cognitive score), were included as independent variables with other neuroimaging and clinical indices in a stepwise linear regression model. The mean age was 70.3 years and the mean MMSE score 21.3. On MRI, 75 patients had at least one stroke lesion. The G 5 z-score was associated with GM density in the pattern selected by the VBM analysis (R2 variation = 0.166, p < 0.001) and the presence of a stroke lesion in the region selected by the VSLM analysis (mainly in the right frontal region; R2 variation = 0.018, p = 0.008). The interaction between the two factors was insignificant (p = 0.374). In conclusion, in this first study combining VBM and VLSM analysis in a memory clinic, global cognition was associated with a specific GM atrophy pattern and the presence of a stroke lesion mainly in the right frontal region.

Locus Coeruleus Degeneration Differs Between Frontotemporal Lobar Degeneration Subtypes

Background:

There are few studies on the locus coeruleus (LC) in frontotemporal lobar degeneration (FTLD) and the potential differences in the LC related to the underlying proteinopathy.

Objective:

The aim of this study was to investigate the LC in FTLD subgroups.

Methods:

Neuropathological cases diagnosed with FTLD were included. The subgroups consisted of FTLD with tau, transactive response DNA-binding protein 43 (TDP) and fused in sarcoma (FUS). Micro- and macroscopical degeneration of the LC were assessed with respect to the number of neurons and the degree of depigmentation. A group of cognitively healthy subjects and a group with vascular cognitive impairment (VCI) served as comparison groups.

Results:

A total of 85 FTLD cases were included, of which 44 had FTLD-TDP, 38 had FTLD-tau, and three had FTLD-FUS. The groups were compared with 25 VCI cases and 41 cognitively healthy control cases (N = 151 for the entire study). All FTLD groups had a statistically higher microscopical degeneration of the LC compared to the controls, but the FTLD-tau group had greater micro- and macroscopical degeneration than the FTLD-TDP group. Age correlated positively with the LC score in the FTLD-tau group, but not in the FTLD-TDP group.

Conclusion:

A greater microscopical degeneration of the LC was observed in all FTLD cases compared to healthy controls and those with VCI. The LC degeneration was more severe in FTLD-tau than in FTLD-TDP. The macroscopically differential degeneration of the LC in FTLD subgroups may facilitate differential diagnostics, potentially with imaging.

Assessing the quality of reports about randomized controlled trials of scalp acupuncture treatment for vascular dementia

BACKGROUND

This study aimed to evaluate the quality of reports about randomized controlled trials (RCTs) of scalp acupuncture (SA) for the treatment of vascular dementia (VD).

METHOD

A systematic search of reports published through to December 2015 was performed in eight databases. The quality of RCTs that used SA as an intervention for VD was evaluated based on the 2010 Consolidated Standards for Reporting of Trials (CONSORT) and 2010 Standards for Reporting Interventions in Controlled Trials of Acupuncture (STRICTA) guidelines. Thirteen items from the CONSORT guideline were scored to give an overall quality score (OQS, range 0-13), and a combined key methodological index score (MIS) (range 0-5) of five key methodological items was measured. The OQS of 17 items from the STRICTA guideline (range 0-17) was also measured.

RESULTS

In total, 26 reports were evaluated. The median OQS based on the CONSORT guideline was 8 (minimum 5, maximum 11), and "trial design," "sample size," "ancillary analyses," and "harms" had a positive rate of less than 10%. The median MIS was 2 (minimum 0, maximum 5), with "allocation concealment and implementation," "blinding," and "intent-to-treat analysis" having a positive rate of less than 15%. The median OQS based on the STRICTA guideline was 12 (minimum 8, maximum 14), with "extent to which treatment was varied (1c)," "number of needle insertions per subject per session (2a)," and "setting and context of treatment (4b)" having a positive rate of less than 10%.

CONCLUSIONS

The overall quality of reports on RCTs of SA treatment for VD was moderate to low. The quality of methodological items was markedly lower than that of other items. The CONSORT and STRICTA guidelines should be used more frequently to standardize the quality of RCT reports of SA treatment for VD.

Factors Determining Cognitive Dysfunction in Cerebral Small Vessel Disease

INTRODUCTION

Vascular dementia consists of cognitive and functional impairment due to cerebrovascular brain injury. With reference to small vessel disease (SVD), even though the radiological evidence of SVD is present in a large number of persons above the age of 80 years, less than one-third of the people progress to dementia. Hence, if those factors are identified, we may be able to formulate strategies to protect that percentage of patients who progress to dementia. In this study, we have analyzed some genetic and nongenetic factors in patients with and without a cognitive impairment in the presence of radiological SVD.

PATIENTS AND METHODS

Two hundred and ten patients who satisfied the criteria for the study were included. All medical comorbidities, demographic factors, substance abuse, etc., were documented and neuropsychological evaluation done. In addition, the genetic testing was done for the polymorphisms of TT, TC, and CC alleles of CYP11B2 based on the literature evidence of the association of CYP11B2 polymorphism and hypertension.

RESULTS

This prospective hospital-based study revealed a significant relationship among hypertension, hyperhomocysteinemia, and severity of white matter changes but other comorbidities did not correlate. No significant correlation was seen between cognitive dysfunction and severity of white matter changes or genotypes TT, TC, and CC. However, TC genotype was more common in male hypertensives. Even though hypertension and hyperhomocysteinemia were associated with leukoaraiosis, none of the factors studied trigger conversion of these radiological changes to clinical cognitive impairment.

DISCUSSION AND CONCLUSION

Severity of cerebral white matter changes seems to correlate with hypertension and hyperhomocysteinemia, however, none of the co-morbidities studied including the three polymorphisms of CYP11B2, that is, TT, TC, and CC seem to determine the conversion of leukoaraiosis to dementia.

Platelets in the Alzheimer's disease brain: do they play a role in cerebral amyloid angiopathy?

Alzheimer’s disease (AD) is characterized by extracellular beta-amyloid plaques and intracellular tau tangles. AD-related pathology is often accompanied by vascular changes. The predominant vascular lesions in AD are cerebral amyloid angiopathy (CAA) and arteriosclerosis. Platelets circulate along the vessel wall responding immediately to vascular injury. The aim of the present study was to explore the presence and migration of platelets (thrombocytes) to sites of small vascular bleedings and/or to beta-amyloid plaques in the brain. We infused fluorescently labeled red PKH26 mouse platelets into transgenic Alzheimer mice overexpressing APP with Swedish/Dutch/Iowa mutations (APP_SDI) and explored if platelets migrate into the brain. Further we studied whether platelets accumulate in the vicinity of β-amyloid plaques. Our animal data shows that infused platelets are found in the liver and partly in the lung, while in the brain platelets were visible to a minor degree. In mice, we did not observe a significant association of platelets with beta-amyloid plaques or vessels. In the brain of Alzheimer postmortem patients platelets could be detected by immunohistochemistry for CD41 and CD62P, but the majority was found in vessels with or without beta-amyloid load, and only a few single platelets migrated deeper into the brain. Our findings suggest that platelets do not migrate into the brains of Alzheimer disease but are concentrated in brain vessels.

Discovery of Acupoints and Combinations with Potential to Treat Vascular Dementia: A Data Mining Analysis

The prevalence of vascular dementia (VaD) is high among the elderly. Acupuncture, a popular therapeutic method in China, can improve memory, orientation, calculation, and self-managing ability in VaD patients. However, in clinical acupuncture and acupuncture research, the selection of acupoints to treat VaD remains challenging. This study aimed to discover acupoints and acupoint combinations with potential for VaD based on data mining. After database searching and screening for articles on clinical trials evaluating the effects of acupuncture on VaD, 238 acupuncture prescriptions were included for further analysis. Baihui (GV 20), Sishencong (EX-HN 1), Fengchi (GB 20), Shuigou (GV 26), and Shenting (GV 24) appeared most frequently in the modern literature and are potential acupoints for VaD. Combinations between Baihui (GV 20), Sishencong (EX-HN 1), Fengchi (GB 20), Shenting (GV 24), Shuigou (GV 26), and Zusanli (ST 36) were most frequent and represent potential combinations for VaD treatment. These results provide a reference for the selection and combination of acupoints to treat VaD in clinical acupuncture and acupuncture research.

Synaptic protein levels altered in vascular dementia

Introduction

Cerebral ischaemia is the defining pathophysiological abnormality in most forms of vascular dementia (VAD), but the pathogenesis of the dementia remains poorly understood. In Alzheimer's disease (AD), there is early loss of synaptic proteins, but these have been little studied in VAD.

Materials and Methods

We measured synaptophysin, postsynaptic density protein 95 (PSD-95), drebrin, synaptosomal-associated protein 25 (SNAP-25) and vascular endothelial growth factor (VEGF) by enzyme-linked immunosorbent assays in superior temporal cortex from 11 patients with VAD and, initially, 11 non-dementia controls. We corrected for neuronal content by measurement of neuron-specific enolase. A further 11 controls were subsequently used in a validation study. Simulation of post-mortem delay found that PSD-95 was stable at 4°C but declined slightly at RT. SNAP-25 and drebrin showed good post-mortem stability. Previous studies had shown good post-mortem preservation of synaptophysin and VEGF.

Results

The VAD cases had lower synaptophysin (but P > 0.05 in initial study), significantly lower SNAP-25 (P = 0.024) and significantly higher drebrin (P = 0.020). On comparison with the second control group, the reduction in synaptophysin was significant (P = 0.008), and the other results were confirmed.

Conclusion

There is probably a reduction in presynaptic proteins in the temporal cortex in VAD, although not as marked as in AD. In VAD, there is also an increase in drebrin, which may be a response to reduced synaptic input.

APOE genotype modifies the relationship between midlife vascular risk factors and later cognitive decline

BACKGROUND

Vascular risk factors have been associated with cognitive decline; however, it remains unclear whether apolipoprotein E (APOE) genotype modifies this relationship. We aimed to further elucidate these relationships and extend previous findings by examining data from a more comprehensive cognitive assessment than used in prior studies.

METHODS

In all, 1436 participants from the prospective Framingham Offspring Cohort Study underwent health examination from 1991 to 1995, followed by a baseline neuropsychological assessment (1999-2003) and a repeat neuropsychological assessment approximately 8 years later (2004-2009). Multivariate linear regression analyses were performed to examine the relationship among midlife vascular risk factors, presence of the APOE ε4 allele, and cognitive change.

RESULTS

APOE genotype significantly modified the associations between both midlife hypertension and cardiovascular disease and decline in language abilities and midlife diabetes and decline in verbal memory, attention, and visuospatial abilities. Associations between increased midlife vascular risk burden and greater cognitive decline were observed among APOE ε4 carriers but not noncarriers.

CONCLUSIONS

The present findings revealed a subgroup at increased risk for cognitive decline (APOE ε4 carriers with midlife exposure to vascular risk factors) and suggest that treatment of vascular risk factors during midlife may reduce the risk of cognitive impairment later in life, particularly among APOE ε4 carriers.

Cerebrovascular risk factors and preclinical memory decline in healthy APOE ε4 homozygotes

OBJECTIVE

To characterize the effects of cerebrovascular (CV) risk factors on preclinical memory decline in cognitively normal individuals at 3 levels of genetic risk for Alzheimer disease (AD) based on APOE genotype.

METHODS

We performed longitudinal neuropsychological testing on an APOE ε4 enriched cohort, ages 21-97. The long-term memory (LTM) score of the Auditory Verbal Learning Test (AVLT) was the primary outcome measure. Any of 4 CV risk factors (CVany), including hypercholesterolemia (CHOL), prior cigarette use (CIG), diabetes mellitus (DM), and hypertension (HTN), was treated as a dichotomized variable. We estimated the longitudinal effect of age using statistical models that simultaneously modeled the cross-sectional and longitudinal effects of age on AVLT LTM by APOE genotype, CVany, and the interaction between the two.

RESULTS

A total of 74 APOE ε4 homozygotes (HMZ), 239 ε4 heterozygotes (HTZ), and 494 ε4 noncarriers were included. APOE ε4 carrier status showed a significant quadratic effect with age-related LTM decline in all models as previously reported. CVany was associated with further longitudinal AVLT LTM decline in APOE ε4 carriers (p=0.02), but had no effect in noncarriers. When ε4 HTZ and HMZ were considered separately, there was a striking effect in HMZ (p<0.001) but not in HTZ. In exploratory analyses, significant deleterious effects were found for CIG (p=0.001), DM (p=0.03), and HTN (p=0.05) in APOE ε4 carriers only that remained significant only for CIG after correction for multiple comparisons.

CONCLUSION

CV risk factors influence age-related memory decline in APOE ε4 HMZ.

Promoter sequence variants of LIGHT are associated with female vascular dementia

LIGHT (homologous to L ymphotoxins, exhibits I nducible expression, and competes with herpes simplex virus G lycoprotein D for H erpes virus entry mediator, a receptor expressed by T lymphocytes) is implicated in the inflammation by disrupted T cell homeostasis, primarily at a transcriptional level. We investigated the association of LIGHT promoter with ischemic stroke and vascular dementia induced by such inflammation. We determined transcription factor binding sites altered by promoter SNPs using transcription factor prediction programs. Six common haplotypes composed of the selected SNPs (C-770T, G-607T, G-543A, and A-399G) were used for the assay of reporter activity. The most frequent haplotype construct, CGGA, induced the highest luciferase activity. The haplotype TTGA showed the lowest expression with 0.39-fold activity (P < 0.001) of CGGA. The substitution from C to T at the locus of C-770T (TGGA) decreased the reporter activity by 47% (P < 0.001). The SNPs and haplotypes were further investigated to see their association with ischemic stroke and vascular dementia in 455 controls and 478 patients. Significant association with vascular dementia was shown in the allele T of C-770T (odds ratio [OR] = 1.54; P < 0.05) and the haplotype TTGA (OR = 10.59; P < 0.05) in females. We concluded that the allele T of C-770T and the haplotype TTGA of the promoter SNPs in LIGHT gene might decrease the expression of LIGHT and subsequently increase the susceptibility to vascular dementia in females.

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.

Neuroradiological findings in vascular dementia

INTRODUCTION

There are multiple diagnostic criteria for vascular dementia (VaD) that may define different populations. Utilizing the criteria of the National Institute of Neurological Disorders and Stroke and Association Internationale pour la Recherche et l'Enseignement en Neurosciences (NINDS-AIREN) has provided improved consistency in the diagnosis of VaD. The criteria include a table listing brain imaging lesions associated with VaD.

METHODS

The different neuroradiological aspects of the criteria are reviewed based on the imaging data from an ongoing large-scale clinical trial testing a new treatment for VaD. The NINDS-AIREN criteria were applied by a centralized imaging rater to determine eligibility for enrollment in 1,202 patients using brain CT or MRI.

RESULTS

Based on the above data set, the neuroradiological features that are associated with VaD and that can result from cerebral small-vessel disease with extensive leukoencephalopathy or lacunae (basal ganglia or frontal white matter), or may be the consequence of single strategically located infarcts or multiple infarcts in large-vessel territories, are illustrated. These features may also be the consequence of global cerebral hypoperfusion, intracerebral hemorrhage, or other mechanisms such as genetically determined arteriopathies.

CONCLUSION

Neuroimaging confirmation of cerebrovascular disease in VaD provides information about the topography and severity of vascular lesions. Neuroimaging may also assist with the differential diagnosis of dementia associated with normal pressure hydrocephalus, chronic subdural hematoma, arteriovenous malformation or tumoral diseases.

Effects of amelioration of total flavonoids from stems and leaves of Scutellaria baicalensis Georgi on cognitive deficits, neuronal damage and free radicals disorder induced by cerebral ischemia in rats

Previous studies reported that the total flavonoids from the stems and leaves of Scutellaria baicalensis Georgi (TFSS) could enhance and improve learning and memory abilities in experimental animals, and reduce the neuronal pathologic alterations induced by some reagents in mice. The present study examined whether TFSS can improve memory dysfunction, neuronal damage, and abnormal free radicals induced by permanent cerebral ischemia in rats. The permanent cerebral ischemic model in rats was produced by bilateral ligation of the common carotid arteries. The influence of permanent cerebral ischemia on learning and memory was determined in the Morris water maze. The neuronal damage in the hippocampus and cerebral cortex was assessed by the neuronal morphologic observations. The contents of malondialdehyde (MDA) and nitric oxide (NO), and the activities of superoxide dismutase (SOD) and catalase (CAT) in the hippocampus and cerebral cortex were measured using thiobarbituric acid, nitrate reductase, xanthine-xanthine oxidase, and ammonium molybdate spectrophotometric methods, respectively. In learning and memory performance tests, cerebral ischemic rats always required a longer latency time to find the hidden platform and spent a shorter time in the target quadrant in the Morris water maze. TFSS 17.5-70 mg.kg(-1) daily orally administered to ischemic rats for 20 d, from day 16-35 after operation differently reduced the prolonged latency and increased swimming time spent in the target quadrant. In neuronal morphologic observations, daily oral TFSS 17.5-70 mg.kg(-1) for 21 d, from day 16-36 after operation markedly inhibited the ischemia-induced neuronal damage. In addition, the increased contents of MDA and NO, and SOD activity, and the decreased activity of CAT in the hippocampus and cerebral cortex induced by cerebral ischemia were differently reversed. The reference drug piracetam (140 mg.kg(-1) per day for 20-21 d) similarly improved impaired memory and neuronal damage but had no significant effects on free radicals in ligated rats. TFSS can improve memory deficits and neuronal damage in rats after permanent cerebral ischemia, which may be beneficial in the treatment of cerebrovascular dementia.

Protective Effects of Breviscapine on Ischemic Vascular Dementia in Rats

Breviscapine, a traditional Chinese medicine, is extensively used in clinic to treat cardiovascular diseases and cerebrovascular injury. In this study, we demonstrated the effects of breviscapine on vascular dementia (VD) rats, which were mimicked by permanent occlusion of bilateral common carotid arteries. Breviscapine (2 mg/kg for 14 d) improved the performance of learning and memory of VD rats in Morris water maze, decreased the level of lipid peroxidation and free radicals, and attenuated the pathological alterations, such as nuclear shrink, cellular edema and irregular arrangement of pyramidal layer in the hippocampal CA(1) area. In vitro experiment, breviscapine (50 microg/l) protected cortical neuron from injury and decreased intracellular calcium overloading induced by H2O2 (10 mM). The results suggest that breviscapine has therapeutic effect on cerebral ischemia and vascular dementia.

Thrombin induces expression of cytokine-induced SH2 protein (CIS) in rat brain astrocytes: involvement of phospholipase A2, cyclooxygenase, and lipoxygenase

Previously we have reported that thrombin induces inflammatory mediators in brain glial cells (Ryu et al. 2000. J Biol Chem 275:29955). In the present study, we found that thrombin induced a negative regulator of a cytokine signaling molecule, cytokine-induced SH2 protein (CIS), in rat brain astrocytes. In response to thrombin, CIS expression was increased at both the mRNA and protein levels. Although STAT5 is known to regulate CIS expression, thrombin did not activate STAT5, and inhibitors of JAK2 (AG490) and JAK3 (WHI-P97 and WHI-P154) had little effect on thrombin-induced CIS expression. In contrast, cytosolic phospholipase A(2) (cPLA(2)), cyclooxygenase (COX), and lipoxygenase (LO) play a role in CIS expression, since inhibitors of cPLA(2), cyclooxygenase (COX), and LO significantly reduced CIS expression. Reactive oxygen species (ROS) scavengers (N-acetyl-cysteine [NAC] and trolox) reduced thrombin-induced CIS expression, and inhibitors of COX and LO reduced ROS produced by thrombin. Furthermore, prostaglandin E(2) (PGE(2)) and leukotriene B(4) (LTB(4)), products of COX and LO, respectively, potentiated thrombin-induced CIS expression, indicating that ROS, and PGE(2) and LTB(4) generated by COX and LO, mediate CIS expression. Since interferon-gamma (IFN-gamma)-induced GAS-luciferase activity and tyrosine phosphorylation of STAT1 and STAT3 were lower in CIS-transfected cells compared to control vector-transfected cells, CIS could have anti-inflammatory activity. These data suggest that thrombin-stimulation of ROS and prostaglandin and leukotriene production via the cPLA(2), COX and LO pathways results in CIS expression. More importantly, CIS expression may be a negative feedback mechanism that prevents prolonged inflammatory responses.

Vascular cognitive impairment

Cerebrovascular disease is the second most common cause of acquired cognitive impairment and dementia and contributes to cognitive decline in the neurodegenerative dementias. The current narrow definitions of vascular dementia should be broadened to recognise the important part cerebrovascular disease plays in several cognitive disorders, including the hereditary vascular dementias, multi-infarct dementia, post-stroke dementia, subcortical ischaemic vascular disease and dementia, mild cognitive impairment, and degenerative dementias (including Alzheimer's disease, frontotemporal dementia, and dementia with Lewy bodies). Here we review the current state of scientific knowledge on the subject of vascular brain burden. Important non-cognitive features include depression, apathy, and psychosis. We propose use of the term vascular cognitive impairment, which is characterised by a specific cognitive profile involving preserved memory with impairments in attentional and executive functioning. Diagnostic criteria have been proposed for some subtypes of vascular cognitive impairment, and there is a pressing need to validate and further refine these. Clinical trials in vascular cognitive impairment are in their infancy but support the value of therapeutic interventions for symptomatic treatment.

Pathological lesions in vascular dementia

According to current diagnostic criteria, a definite diagnosis of vascular dementia (VaD) can be reached on pathological grounds by showing the presence of vascular lesions and the absence of degenerative changes exceeding those expected for age. However, while it is commonly accepted that VaD is a group of heterogeneous entities rather than a process with a unique pathological substrate, the spectrum of vessel and parenchyma changes etiologically associated with the clinical syndrome remains basically unidentified. The review of some recent clinical-pathological series shows that different studies have assessed the presence of dissimilar vascular lesions and that, in many cases, no pathological definition was given. This has hindered the clarification of clinical-pathological correlations in the field of VaD. In this scenario, the use of animal models of cerebrovascular diseases may help to elucidate the type of lesions possibly linked with cognitive impairment in humans and might provide insight into some of the pathophysiological mechanisms of vascular cognitive impairment. A consensus is today needed in order to harmonize the pathological examination of vascular lesions in cases of dementia. An ongoing survey aimed at collecting information about the procedures used in different pathological laboratories in the assessment of lesions possibly associated with dementia is finally presented.

Subcortical ischaemic vascular dementia

Vascular dementia is the second most common type of dementia. The subcortical ischaemic form (SIVD) frequently causes cognitive impairment and dementia in elderly people. SIVD results from small-vessel disease, which produces either arteriolar occlusion and lacunes or widespread incomplete infarction of white matter due to critical stenosis of medullary arterioles and hypoperfusion (Binswanger's disease). Symptoms include motor and cognitive dysexecutive slowing, forgetfulness, dysarthria, mood changes, urinary symptoms, and short-stepped gait. These manifestations probably result from ischaemic interruption of parallel circuits from the prefrontal cortex to the basal ganglia and corresponding thalamocortical connections. Brain imaging (computed tomography and magnetic resonance imaging) is essential for correct diagnosis. The main risk factors are advanced age, hypertension, diabetes, smoking, hyperhomocysteinaemia, hyperfibrinogenaemia, and other conditions that can cause brain hypoperfusion such as obstructive sleep apnoea, congestive heart failure, cardiac arrhythmias, and orthostatic hypotension. Cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL)and some forms of cerebral amyloid angiopathy have a genetic basis. Treatment is symptomatic and prevention requires control of treatable risk factors.

Magnetic resonance imaging and magnetic resonance spectroscopy in dementias

This article reviews recent studies of magnetic resonance imaging and magnetic resonance spectroscopy in dementia, including Alzheimer's disease, frontotemporal dementia, dementia with Lewy bodies, idiopathic Parkinson's disease, Huntington's disease, and vascular dementia. Magnetic resonance imaging and magnetic resonance spectroscopy can detect structural alteration and biochemical abnormalities in the brain of demented subjects and may help in the differential diagnosis and early detection of affected individuals, monitoring disease progression, and evaluation of therapeutic effect.

Cerebral arteriovenous transit time (CTT): a sonographic assessment of cerebral microcirculation using ultrasound contrast agents

Transcranial color-coded sonography (TCCS) has been used to investigate major brain-supplying arteries, draining veins and brain parenchyma. Here, we describe a contrast-enhanced TCCS analysis of cerebral arteriovenous transit time (cTT) as a measure of cerebral microcirculation. We evaluate its reproducibility and its correlation with clinical impairment of brain function and neuropsychological tests. A total of 27 patients with cerebral microangiopathy and 30 healthy controls were examined. CTT is defined by the time an ultrasound contrast agent requires to pass from the P2-segment of the posterior cerebral artery to the vein of Galen. This was measured by comparison of power Doppler intensity in two off-line defined regions of interest. Serial intraindividual cTT measurements within several min showed a good reproducibility of this parameter. cTT was significantly longer in patients with cerebral microangiopathy than in controls (Mann-Whitney U test,p < 0.001) and related to cognitive impairment measured by the Mini-Mental-State examination. We conclude that it is a quick and reliable parameter related to increased vascular resistance of the microcirculation or a rarefaction of microvessels. Further studies are needed to show the sensitivity and specificity of cTT in the diagnosis of small vessel disease and the interference of important circulation factors, such as heart failure or blood viscosity.

Orthostatic hypotension and cognitive decline in older people

OBJECTIVES

To establish the role of orthostatic hypotension (OH) as a risk factor for cognitive decline among home-dwelling and institutionalized older people and to describe other predictors of cognitive decline.

DESIGN

Follow-up study with two clinical examinations.

SETTING

A community-based setting in northern Finland.

PARTICIPANTS

All of the 1159 people aged 70 or more living in five rural municipalities around the town of Oulu in Northern Finland in 1991. At the time of the follow-up examination, 2.5 years later, 884 of the original participants were alive and 651 were re-examined.

MEASUREMENTS

In 1991, 907 people (78.3% of the total population) were tested for orthostatic hypotension, and their cognitive capacity was assessed with the Mini-Mental State Examination (MMSE). The calculation/spelling tasks were excluded from the final version used in the statistical analysis. The re-assessment of cognitive capacity was made on 651 subjects (73.6% of those alive) who had participated in the first examination. The data were analyzed using polychotomous and linear regression analysis models.

RESULTS

The prevalence of OH was 28.7%, with no age or sex differences. The mean sum score for the shortened MMSE in 1991 was 21.6 (+/-3.98) for persons with OH and 21.1 (+/-4.08) for non-OH persons. During the follow-up, the sum score declined in the OH group by .44 (+/-2.81) points and in the non-OH group by .83 (+/-3.61) points. No type of OH (systolic or diastolic 1- or 3-minute values or their combination) predicted cognitive decline; the only predictors were old age and low level of formal education.

CONCLUSIONS

Orthostatic hypotension is a common clinical condition that affects every fourth person aged 70 years or older. By temporarily inducing cerebral hypoperfusion, it may cause or exacerbate cognitive dysfunction. In an unselected population, OH was not associated with cognitive deterioration, nor did it predict cognitive decline during a 2-year follow-up.

Vascular dementia: a contemporary review of epidemiology, diagnosis, prevention, and treatment

The past decade has seen a renewed interest in vascular dementia. Key epidemiologic studies have examined the prevalence, incidence, course and risk factors of vascular dementia. New classification systems have been developed to improve the reliability of the diagnosis, and there have been advances in diagnostic methodology, such as neuroimaging and neuropsychological assessment. New treatments for vascular dementia are being developed to protect the brain from cerebral ischemia and to limit progression of cognitive impairment. Diagnostic criteria for vascular dementia remain to be validated by carefully designed, systematic, clinicopathologic study. Once such criteria are validated, meaningful study of subgroups of vascular dementia can be explored. Until the relationship between vascular dementia and Alzheimer's disease is better defined, the nosology for vascular dementia may be defined best as dementia associated with stroke.

Signaling pathways involved in thrombin-induced cell protection

This study examined the signal transduction pathways involved in thrombin-induced neuroprotection and compares these results with those of a similar study of thrombin-induced neuronal death. In thrombin-induced protection of astrocytes from hypoglycemia, pretreatment of astrocytes with tyrosine or serine/threonine kinase inhibitors, cytochalasin D, or exoenzyme C3, a potent inhibitor of the small GTPase RhoA, attenuated thrombin-induced protection. These same inhibitors were previously shown to block thrombin-induced cell death, implying a similarity in the cell death and cell-protective pathways. Biochemical assays determined that thrombin increased available RhoA activity, although more slowly and to a lesser extent than occurs in thrombin-induced cell death. A clear difference in these pathways was revealed when a time course study of thrombin-induced cell death indicated that unlike thrombin-induced protection, cells must be exposed to thrombin for >16 h to irreversibly enter the cell death pathway. Addition of lower doses of thrombin every 24 h also induced cell death. These studies indicate that exposure of cells to micromolar concentrations of thrombin alone does not induce cell death, but the continued exposure to thrombin is required. Thus the cell death and protective pathways may share initial signaling proteins, but differences in the amplitude as well as the duration of the signal may result in different final pathways.