Brain perfusion imaging predicts survival in Alzheimer's disease

Vascular Function and Ion Channels in Alzheimer's Disease

This review paper explores the critical role of vascular ion channels in the regulation of cerebral artery function and examines the impact of Alzheimer's disease (AD) on these processes. Vascular ion channels are fundamental in controlling vascular tone, blood flow, and endothelial function in cerebral arteries. Dysfunction of these channels can lead to impaired cerebral autoregulation, contributing to cerebrovascular pathologies. AD, characterized by the accumulation of amyloid beta (Aβ) plaques and neurofibrillary tangles, has been increasingly linked to vascular abnormalities, including altered vascular ion channel activity. Here, we briefly review the role of vascular ion channels in cerebral blood flow control and neurovascular coupling. We then examine the vascular defects in AD, the current understanding of how AD pathology affects vascular ion channel function, and how these changes may lead to compromised cerebral blood flow and neurodegenerative processes. Finally, we provide future perspectives and conclusions. Understanding this topic is important as ion channels may be potential therapeutic targets for improving cerebrovascular health and mitigating AD progression.

The effects of voluntary running on cerebrovascular morphology and spatial short-term memory in a mouse model of amyloidosis

Physical activity has been correlated with a reduced risk of cognitive decline, including that associated with vascular dementia, mild cognitive impairment (MCI) and Alzheimer's disease (AD); recent literature suggests this may in part result from benefits to the cerebrovascular network. Using a transgenic (Tg) mouse model of AD, we evaluated the effect of running on cortical and hippocampal vascular morphology, cerebral amyloid angiopathy, amyloid plaque load, and spatial memory. TgCRND8 mice present with progressive amyloid pathology, advancing from the cortex to the hippocampus in a time-dependent manner. We postulated that the characteristic progression of pathology could lead to differential, time-dependent effects of physical activity on vascular morphology in these brain regions at 6 months of age. We used two-photon fluorescent microscopy and 3D vessel tracking to characterize vascular and amyloid pathology in sedentary TgCRND8 mice compared those who have a history of physical activity (unlimited access to a running wheel, from 3 to 6 months of age). In sedentary TgCRND8 mice, capillary density was found to be lower in the cortex and higher in the hippocampus compared to non-transgenic (nonTg) littermates. Capillary length, vessel branching, and non-capillary vessel tortuosity were also higher in the hippocampus of sedentary TgCRND8 compared to nonTg mice. Three months of voluntary running resulted in normalizing cortical and hippocampal microvascular morphology, with no significant difference between TgCRND8 and nonTg mice. The benefits of physical activity on cortical and hippocampal vasculature in 6-month old TgCRND8 mice were not paralleled by significant changes on parenchymal and cerebral amyloid pathology. Short-term spatial memory- as evaluated by performance in the Y-maze- was significantly improved in running compared to sedentary TgCRND8 mice. These results suggest that long-term voluntary running contributes to the maintenance of vascular morphology and spatial memory in TgCRND8 mice, even in the absence of an effect on amyloid pathology.

Endothelial Dysfunction and Amyloid-β-Induced Neurovascular Alterations

Alzheimer's disease (AD) and cerebrovascular diseases share common vascular risk factors that have disastrous effects on cerebrovascular regulation. Endothelial cells, lining inner walls of cerebral blood vessels, form a dynamic interface between the blood and the brain and are critical for the maintenance of neurovascular homeostasis. Accordingly, injury in endothelial cells is regarded as one of the earliest symptoms of impaired vasoregulatory mechanisms. Extracellular buildup of amyloid-β (Aβ) is a central pathogenic factor in AD. Aβ exerts potent detrimental effects on cerebral blood vessels and impairs endothelial structure and function. Recent evidence implicates vascular oxidative stress and activation of the non-selective cationic channel transient receptor potential melastatin (TRPM)-2 on endothelial cells in the mechanisms of Aβ-induced neurovascular dysfunction. Thus, Aβ triggers opening of TRPM2 channels in endothelial cells leading to intracellular Ca(2+) overload and vasomotor dysfunction. The cerebrovascular dysfunction may contribute to AD pathogenesis by reducing the cerebral blood supply, leading to increased susceptibility to vascular insufficiency, and by promoting Aβ accumulation. The recent realization that vascular factors contribute to AD pathobiology suggests new targets for the prevention and treatment of this devastating disease.

Identification of diabetes-related dementia: Longitudinal perfusion SPECT and amyloid PET studies

AIMS

We attempted to identify a dementia subgroup with characteristics associated with diabetes mellitus (DM)-related metabolic abnormalities, referred to as diabetes-related dementia, using longitudinal single photon emission computed tomography (SPECT) and Pittsburgh compound-B (PiB) positron emission tomography (PET).

METHODS

We classified 175 patients with clinically diagnosed Alzheimer disease (AD) and DM into 4 subgroups based on brain imaging in a 2013 study. Among them, we investigated follow-up SPECT studies in 29 patients of an AD group showing decreased regional cerebral blood flow (rCBF) of the parietotemporal lobe on initial SPECT and 18 patients of a diabetes-related dementia group showing neither decreased rCBF of the parietotemporal lobe nor cerebrovascular disease, which is strongly associated with DM-related factors. Eleven of them underwent PiB PET.

RESULTS

Follow-up SPECT showed more profound rCBF reduction in the parietotemporal lobe and other areas of the AD group, whereas follow-up SPECT showed an rCBF reduction in small areas of the frontotemporal and limbic lobes of the diabetes-related dementia group. Six of 9 patients with diabetes-related dementia were negative or equivocal for PiB binding.

CONCLUSION

A subset of a dementia subgroup with characteristics predominantly associated with DM-related factors may underlie a pathophysiology different from AD, although these patients were clinically diagnosed as having AD. The identification of diabetes-related dementia may be necessary for considering an appropriate therapy and prevention in clinical practice.

Soluble amyloid precursor protein 770 is released from inflamed endothelial cells and activated platelets: a novel biomarker for acute coronary syndrome

BACKGROUND

Separate monitoring of the cleavage products of different amyloid β precursor protein (APP) variants may provide useful information.

RESULTS

We found that soluble APP770 (sAPP770) is released from inflamed endothelial cells and activated platelets as judged by ELISA.

CONCLUSION

sAPP770 is an indicator for endothelial and platelet dysfunctions.

SIGNIFICANCE

How sAPP770 is released in vivo has been shown. Most Alzheimer disease (AD) patients show deposition of amyloid β (Aβ) peptide in blood vessels as well as the brain parenchyma. We previously found that vascular endothelial cells express amyloid β precursor protein (APP) 770, a different APP isoform from neuronal APP695, and produce Aβ. Since the soluble APP cleavage product, sAPP, is considered to be a possible marker for AD diagnosis, sAPP has been widely measured as a mixture of these variants. We hypothesized that measurement of the endothelial APP770 cleavage product in patients separately from that of neuronal APP695 would enable discrimination between endothelial and neurological dysfunctions. Using our newly developed ELISA system for sAPP770, we observed that inflammatory cytokines significantly enhanced sAPP770 secretion by endothelial cells. Furthermore, we unexpectedly found that sAPP770 was rapidly released from activated platelets. We also found that cerebrospinal fluid mainly contained sAPP695, while serum mostly contained sAPP770. Finally, to test our hypothesis that sAPP770 could be an indicator for endothelial dysfunction, we applied our APP770 ELISA to patients with acute coronary syndrome (ACS), in which endothelial injury and platelet activation lead to fibrous plaque disruption and thrombus formation. Development of a biomarker is essential to facilitate ACS diagnosis in clinical practice. The results revealed that ACS patients had significantly higher plasma sAPP770 levels. Furthermore, in myocardial infarction model rats, an increase in plasma sAPP preceded the release of cardiac enzymes, currently used markers for acute myocardial infarction. These findings raise the possibility that sAPP770 can be a useful biomarker for ACS.

Dynamic single photon emission computed tomography--basic principles and cardiac applications

The very nature of nuclear medicine, the visual representation of injected radiopharmaceuticals, implies imaging of dynamic processes such as the uptake and wash-out of radiotracers from body organs. For years, nuclear medicine has been touted as the modality of choice for evaluating function in health and disease. This evaluation is greatly enhanced using single photon emission computed tomography (SPECT), which permits three-dimensional (3D) visualization of tracer distributions in the body. However, to fully realize the potential of the technique requires the imaging of in vivo dynamic processes of flow and metabolism. Tissue motion and deformation must also be addressed. Absolute quantification of these dynamic processes in the body has the potential to improve diagnosis. This paper presents a review of advancements toward the realization of the potential of dynamic SPECT imaging and a brief history of the development of the instrumentation. A major portion of the paper is devoted to the review of special data processing methods that have been developed for extracting kinetics from dynamic cardiac SPECT data acquired using rotating detector heads that move as radiopharmaceuticals exchange between biological compartments. Recent developments in multi-resolution spatiotemporal methods enable one to estimate kinetic parameters of compartment models of dynamic processes using data acquired from a single camera head with slow gantry rotation. The estimation of kinetic parameters directly from projection measurements improves bias and variance over the conventional method of first reconstructing 3D dynamic images, generating time-activity curves from selected regions of interest and then estimating the kinetic parameters from the generated time-activity curves. Although the potential applications of SPECT for imaging dynamic processes have not been fully realized in the clinic, it is hoped that this review illuminates the potential of SPECT for dynamic imaging, especially in light of new developments that enable measurement of dynamic processes directly from projection measurements.

Correlation of findings in advanced MR techniques with global severity scales in patients with some grade of cognitive impairment

INTRODUCTION

Some previous studies in patients with mild cognitive impairment and Alzheimer's disease have probed changes in the results of (1)H magnetic resonance spectroscopy and perfusion- and diffusion-weighted imaging. The purpose of this work was to correlate the results of perfusion- and diffusion-weighted imaging and magnetic resonance spectroscopy with the results of two global severity scales in cognitive impairment: the clinical dementia rating (CDR) and the global deterioration scale (GDS).

PATIENTS AND METHODS

We evaluated 87 patients with cognitive impairment of diverse grade (35 men and 52 women; mean age, 70.2 +/- 8.5 years old). All patients were evaluated by a neurological team in our hospital. They applied both global severity scales (CDR and GDS) and referred the patients to our diagnostic imaging department to make a cerebral magnetic resonance imaging study and studies of diffusion- and perfusion-weighted imaging and magnetic resonance spectroscopy. We excluded patients with history of Parkinson's disease, frontotemporal dementia, cerebrovascular disease, intracranial tumors, hydrocephaly, epilepsy, alcoholism and psychiatric disorders. Magnetic resonance spectroscopy was carried out in the left occipital cortex and in the posterior cingulate gyrus. The evaluated metabolites were N-acetylaspartate (NAA), choline (Cho), creatine (Cr) and myo-inositol (mI). After diffusion-weighted imaging, we calculated apparent diffusion coefficient values in the region of interest located in hippocampi, white matter of temporal lobes, occipital lobes, parietal lobes, frontal lobes and posterior cingulate gyrus of both hemispheres. In perfusion-weighted imaging, we calculated the relative cerebral blood volume in hippocampi, gray matter of frontal lobes, occipital lobes, temporoparietal regions, posterior cingulate gyri and somatic-sensorial cortex. We used Spearman coefficient to analyse the correlation among the different factors. Statistical analysis was made with SPSS 14 software.

RESULTS

We found 33 patients with Alzheimer's disease and 54 with mild cognitive impairment. The Spearman coefficient had statistical significance in the correlation of CDR and GDS (R(2)=0.596, p<0.001). Magnetic resonance spectroscopy showed a good correlation between ratios of NAA/Cr and NAA/mI with CDR and GDS in both evaluated regions and a weak correlation between Cho/Cr in the left occipital lobe and GDS. In diffusion-weighted imaging, we found a weak correlation between GDS and apparent diffusion coefficient values in hippocampi, temporal lobes, left frontal lobe and left occipital lobe. Finally, perfusion showed a weak correlation between GDS and relative cerebral blood volume in occipital lobes and posterior cingulate gyrus.

CONCLUSION

In patients with cognitive impairment, there is a good correlation between CDR and GDS. The tool that showed the closest correlation with the clinical scales (CDR and GDS) was magnetic resonance spectroscopy in the left occipital cortex and posterior cingulate gyrus. Perfusion- and diffusion-weighted imaging are tools with a weak correlation with clinical scales, GDS being unique that gave us significant statistical results; this could be explained by the major number of items considered for cognitive impairment (GDS 2 and 3) compared with CDR (CDR 0.5). Magnetic resonance spectroscopy can be used in the diagnostic, following and evaluation of the response to the treatment in patients with cognitive impairment (mild cognitive impairment and Alzheimer's disease), complementing the information obtained in the clinical evaluation.

The overlap between neurodegenerative and vascular factors in the pathogenesis of dementia

There is increasing evidence that cerebrovascular dysfunction plays a role not only in vascular causes of cognitive impairment but also in Alzheimer's disease (AD). Vascular risk factors and AD impair the structure and function of cerebral blood vessels and associated cells (neurovascular unit), effects mediated by vascular oxidative stress and inflammation. Injury to the neurovascular unit alters cerebral blood flow regulation, depletes vascular reserves, disrupts the blood-brain barrier, and reduces the brain's repair potential, effects that amplify the brain dysfunction and damage exerted by incident ischemia and coexisting neurodegeneration. Clinical-pathological studies support the notion that vascular lesions aggravate the deleterious effects of AD pathology by reducing the threshold for cognitive impairment and accelerating the pace of the dementia. In the absence of mechanism-based approaches to counteract cognitive dysfunction, targeting vascular risk factors and improving cerebrovascular health offers the opportunity to mitigate the impact of one of the most disabling human afflictions.

The progression of cognitive deterioration and regional cerebral blood flow patterns in Alzheimer's disease: a longitudinal SPECT study

BACKGROUND AND PURPOSE

The progression of cognitive deterioration in patients with Alzheimer's disease (AD) is considerably variable. The ability to predict the progression rate is important for clinicians to treat and manage patients with AD. We examined the possible relationship between the rate of cognitive deterioration and regional cerebral blood flow (rCBF) patterns in patients with AD.

METHODS

We followed 48 patients with AD for an average of 37 months. They were subsequently divided into the rapidly progressing group (n=24) and slowly progressing group (n=24) based on an annual Mini-Mental State Examination (MMSE) score change. Initial and follow-up rCBF were assessed using single photon emission CT (SPECT) and the SPECT data were analyzed by 3D-stereotactic surface projections.

RESULTS

At initial evaluation, the rapidly progressing group had greater rCBF deficits mainly in the parietotemporal and frontal regions, and left posterior cingulate than did the slowly progressing group. When compared with initial SPECT, follow-up SPECT showed a significant rCBF reduction in widespread regions, including parietotemporal and frontal lobes, of the rapidly progressing group, while showed in the scattered and small regions of hemispheres of the slowly progressing group.

CONCLUSION

Our longitudinal SPECT study suggests a significant association between rCBF deficits in the parietotemporal, posterior cingulate, and frontal regions and subsequent rapid cognitive and rCBF deterioration.

Cerebrovascular dysfunction in amyloid precursor protein transgenic mice: contribution of soluble and insoluble amyloid-beta peptide, partial restoration via gamma-secretase inhibition

The contributing effect of cerebrovascular pathology in Alzheimer's disease (AD) has become increasingly appreciated. Recent evidence suggests that amyloid-beta peptide (Abeta), the same peptide found in neuritic plaques of AD, may play a role via its vasoactive properties. Several studies have examined young Tg2576 mice expressing mutant amyloid precursor protein (APP) and having elevated levels of soluble Abeta but no cerebral amyloid angiopathy (CAA). These studies suggest but do not prove that soluble Abeta can significantly impair the cerebral circulation. Other studies examining older Tg2576 mice having extensive CAA found even greater cerebrovascular dysfunction, suggesting that CAA is likely to further impair vascular function. Herein, we examined vasodilatory responses in young and older Tg2576 mice to further assess the roles of soluble and insoluble Abeta on vessel function. We found that (1) vascular impairment was present in both young and older Tg2576 mice; (2) a strong correlation between CAA severity and vessel reactivity exists; (3) a surprisingly small amount of CAA led to marked reduction or complete loss of vessel function; 4) CAA-induced vasomotor impairment resulted from dysfunction rather than loss or disruption of vascular smooth muscle cells; and 5) acute depletion of Abeta improved vessel function in young and to a lesser degree older Tg2576 mice. These results strongly suggest that both soluble and insoluble Abeta cause cerebrovascular dysfunction, that mechanisms other than Abeta-induced alteration in vessel integrity are responsible, and that anti-Abeta therapy may have beneficial vascular effects in addition to positive effects on parenchymal amyloid.

Cognitive predictors of mortality in elderly retirees: results from the Freedom House study

OBJECTIVE

The objective of this longitudinal cohort study was to study the cognitive domains associated with five-year longitudinal survival among healthy, well-educated, noninstitutionalized elderly.

METHODS

Survival curves were generated as a function of cross-sectional baseline cognitive test performance.

RESULTS

Nonverbal tests were significantly associated with survival. This finding was markedly consistent. Several nonverbal tasks were each significantly associated with survival independently of age, gender, baseline level of care, and healthcare utilization. In a multivariate model, copying a clock made the strongest, independent contribution to survival.

CONCLUSIONS

Right hemisphere integrity in general and nonverbal drawing tasks in particular have been associated with survival in conditions as diverse as Alzheimer disease, stroke, and epilepsy. This study extends this association to "normal" aging. The mechanism by which nonverbal cognitive function is related to mortality remains unclear but may be mediated by changes in right hemisphere cortical control of autonomic function. Nondemented older persons may be at risk. Clock drawing may provide a simple means of identifying them.

Insular Alzheimer's disease pathology as a cause of "age-related" autonomic dysfunction and mortality in the non-demented elderly

Only a few brain structures have been implicated in the autonomic control of blood pressure and heart rate. Among them are heteromodal association areas in the cortex, especially the insular cortex. Ischemic insular lesions have been associated with both cardiac arrhythmias and mortality. However, stroke may not be the only insular pathology with the potential to disrupt autonomic function. Alzheimer's disease (AD) is associated with both insular pathology and autonomic dysfunction. Alzheimer's dementia is merely the final stage of a pathological process that spans decades. Recent studies have demonstrated a hierarchichal sequence of AD pathology that includes the insular cortex. This may explain why AD has effects on BP and central autonomic cardio-regulatory functions. However, AD reaches the insular cortex at a "preclinical" stage in its development (i.e., before "dementia" can be diagnosed). Thus, AD pathology should also be considered as a possible explanation for autonomic morbidity and mortality in non-demented elderly persons. We hypothesize that autonomic dyscontrol, commonly seen in non-demented well elderly persons without significant cardiovascular disease (CVD), reflects subclinical stages of AD pathology affecting the insular cortex. If true, then preclinical AD pathology should be considered as a possible explanation for arrhythmia/fall related morbidity and mortality in non-demented elderly persons.

Evidence of biochemical and biomagnetic interactions in Alzheimer's disease: an MEG and MR spectroscopy study

BACKGROUND

Several neuroimaging studies have shown reliable differences between Alzheimer's disease (AD) patients and age-matched controls. However, few studies have demonstrated the interactions between neuroimaging methods for the diagnoses of AD.

OBJECTIVE

In this study, we try to elucidate the complementary nature of magnetoencephalography (MEG) and magnetic resonance spectroscopy (MRS) examinations in the assessmentof AD.

METHODS

Ten patients fulfilling the NINCDS-ADRDA criteria of probable AD, and 10 elderly individuals with no history of neurological or psychiatric illness serving as age-matched controls participated in the study. All patients and controls received an MRS, MEG and neuropsychological assessment. MEG data were obtained in the context of a working memory task, previously utilized in a similar sample of patients.

RESULTS

The AD group showed a reduced number of activity sources over left temporoparietal areas during the late portion of the evoked magnetic field (between 400-800 ms), as well as a bilateral temporoparietal increase in creatine and myoinositol concentrations, and in the myoinositol/N-acetyl-aspartate ratio. The combination of the variables 'number of dipoles during the late portion of the evoked magnetic field' and 'myoinositol/N-acetyl-aspartate ratio' accounted for 65% of the variance of the Mini Mental State Examination scores.

CONCLUSIONS

These results highlight the importance of assessing the complex brain pathology underlying AD by utilizing multiple brain examination modalities in a coordinate approach.

Proton magnetic resonance spectroscopy and magnetoencephalographic estimation of delta dipole density: a combination of techniques that may contribute to the diagnosis of Alzheimer's disease

Whole-head magnetoencephalographic recordings were obtained from 10 patients with Alzheimer's disease (AD) and 10 healthy controls in a resting position. Spectroscopic examinations were performed by means of a 1.5-tesla whole-body scanner in the temporoparietal regions of both hemispheres. The relationship between (1)H-MRS-based and magnetoencephalography (MEG)-based measures and their conjoined capability to improve the diagnosis of AD were investigated in this study. Logistic regression analyses were performed. Three separated logistic models were calculated for (1)H-MRS-based metabolites, low-frequency magnetic activity, and the combination of both measures. A combined myoinositol/N-acetyl aspartate (mI/NAA)-delta dipole density (DD) model predicted the diagnosis with 90% sensitivity and 100% specificity. Additionally, the combination of temporoparietal mI/NAA and delta DD values explained the variability of individuals' cognitive status. The results support the notion that a multidisciplinary approach may improve the understanding and diagnosis of AD.

Molecular neuroimaging in Alzheimer's disease

Considerable data exist to support the use of positron emission tomography (PET) and single photon emission computed tomography (SPECT) scanning as biomarkers for Alzheimer's disease (AD). The techniques are reasonably sensitive and specific in differentiating AD from normal aging, and recent studies with pathological confirmation show good sensitivity and specificity in differentiating AD from other dementias. These techniques also can detect abnormalities in groups of asymptomatic and presymptomatic individuals and may be able to predict decline to dementia. However, there are a number of existing questions related to the use of these techniques in samples that are fully representative of the spectrum of patients with dementia. For example, it is unclear how well PET and SPECT perform in comparison to a clinical diagnosis obtained in the same patient group, when autopsy is used as a gold standard. It will also be important to know what PET and SPECT add to the certainty of diagnosis in addition to the standard clinical diagnosis. Despite these unanswered questions, PET and SPECT may have application as biomarkers for AD in a number of clinical and research settings, especially in academic centers, where most of the existing studies have been done.

Brain perfusion SPECT in patients with mild cognitive impairment and Alzheimer's disease: comparison of a semiquantitative and a visual evaluation

Due to the increasing importance of early recognition and differential diagnosis of dementias, cerebral perfusion scans using "single photon emission computed tomography" (SPECT) are increasingly integrated into the examination routine. The goal of this study was to check the diagnostic validity of SPECT scans of MCI- and DAT-patients, two subgroups out of 369 persons with etiologically unclear cognitive dysfunction, which underwent an assessment program for probable dementia including cognitive testing, cranial computed tomography, ultrasound, routine laboratory testing including vascular risk factors. After exclusion of patients with no or other forms of dementia we analyzed SPECT data of patients with mild cognitive impairment (MCI; n = 85) and dementia of the Alzheimer type (DAT; n = 78) in comparison with a healthy control group (n = 34).Visual assessment as well as a manual "regions of interest" (ROI) regionalization of the cortex were performed, whereby a ROI/cerebellum ratio was calculated as a semi-quantitative value. Association cortex areas were assessed regarding frontal, temporal, and parietal lobes of both hemispheres. When comparing the ratios of patients with DAT and controls, we found a statistically significant reduction of the cerebral perfusion in all measured cortex areas (p < 0.001). The comparison of patients with MCI with the selected control group also established a statistically significant difference in the cerebral perfusion for the evaluated cortex areas with the exception of the left hemispheric frontal and parietal cortex.A considerable number of the MCI patients showed an MMSE-score within the normal range, but with regard to the perfusion in the right hemispheric association cortex these patients also could be distinguished unambiguously from controls. Sensitivity levels found by visual assessment were at least as high as those found by the ROI method (pathological assessment: visual 49.4% vs. ROI 47.1% for MCI; visual 75.6% vs. ROI 73.1% for DAT). High experienced visual assessment of cerebral perfusion scans using SPECT provides an useful additional tool in diagnosis of cognitive impairment. The used semiquantitative ROI-method is nearly equivalent and does not depend on the experience of the investigator.

FDG-PET measurement is more accurate than neuropsychological assessments to predict global cognitive deterioration in patients with mild cognitive impairment

The accurate prediction, at a pre-dementia stage of Alzheimer's disease (AD), of the subsequent clinical evolution of patients would be a major breakthrough from both therapeutic and research standpoints. Amnestic mild cognitive impairment (MCI) is presently the most common reference to address the pre-dementia stage of AD. However, previous longitudinal studies on patients with MCI assessing neuropsychological and PET markers of future conversion to AD are sparse and yield discrepant findings, while a comprehensive comparison of the relative accuracy of these two categories of measure is still lacking. In the present study, we assessed the global cognitive decline as measured by the Mattis scale in 18 patients with amnestic MCI over an 18-month follow-up period, studying which subtest of this scale showed significant deterioration over time. Using baseline measurements from neuropsychological evaluation of memory and PET, we then assessed significant markers of global cognitive change, that is, percent annual change in the Mattis scale total score, and searched for the best predictor of this global cognitive decline. Altogether, our results revealed significant decline over the 18-month follow-up period in the total score and the verbal initiation and memory-recall subscores of the Mattis scale. The percent annual change in the total Mattis score significantly correlated with age and baseline performances in delayed episodic memory recall as well as semantic autobiographical and category word fluencies. Regarding functional imaging, significant correlations were also found with baseline PET values in the right temporo-parietal and medial frontal areas. Age and right temporo-parietal PET values were the most significant predictors of subsequent global cognitive decline, and the only ones to survive stepwise regression analyses. Our findings are consistent with previous works showing predominant delayed recall and semantic memory impairment at a pre-dementia stage of AD, as well as early metabolic defects in the temporo-parietal associative cortex. However, they suggest that only the latter predictor is specifically and accurately associated with subsequent cognitive decline in patients with MCI within 18 months of first assessment.

Diagnosis of suspected Alzheimer's disease is improved by automated analysis of regional cerebral blood flow

PURPOSE

Accurate diagnosis of Alzheimer's disease (AD), the most common form of dementia, remains difficult. In order to assess whether fully automated stereotactic surface projection (3D-SSP) presentation contributes to the diagnosis of AD by single-photon emission computed tomography (SPECT), we investigated the diagnostic accuracy of transaxial display with and without 3D-SSP analysis as well as the correlation between cerebral perfusion in different cortical areas and the mini mental score (MMS).

METHODS

Seventy-two patients referred because of cognitive impairment were included in the study. According to the National Institute of Neurological and Communicative Disorders and Stroke (NINCDS) and the Alzheimer's disease and Related Disorders Association (ADRDA) criteria, 27 patients were diagnosed as having probable AD while 45 were classified as non-AD patients. 3D-SSP was used to quantify the regional cerebral blood flow (rCBF) acquired from SPECT imaging.

RESULTS

Compared with the transaxial section presentation alone, 3D-SSP presentation improved the area under the receiver operating curve (p<0.05) as well as intra-observer (k=0.73 vs 0.88) and inter-observer (k=0.50 vs 0.84) reproducibility. Upon normalisation of regional to thalamic activity, multiple regression analysis revealed a strong correlation between the MMS and rCBF in the right parietal cortex (p=0.002).

CONCLUSION

Addition of 3D-SSP to the transaxial section display of ECD-SPECT studies improves the reproducibility and the diagnostic performance in respect of AD in patients with cognitive impairment and provides a valid tool for assessment of the severity of cortical perfusion abnormalities in such patients.

Cerebrovascular effects of amyloid-beta peptides: mechanisms and implications for Alzheimer's dementia

1. The amyloid B-peptide (AB) is involved in the mechanisms of Alzheimer dementia. This paper reviews experimental evidence indicating that AB exerts profound effects on the regulation of the cerebral circulation. 2. Thus, AB compromises the ability of cerebral endothelial cells to produce vascular relaxing factors, impairs the ability of cerebral blood vessels to maintain adequate flow during hypotension, and attenuates the increases in CBF evoked by enhanced brain activity. 3. Studies in transgenic mice overexpressing the amyloid precursor protein suggest that these cerebrovascular alterations disrupt the delicate balance between the brain's energy requirements and cerebral blood supply, rendering the brain more vulnerable to ischemic injury. 4. The findings support the recently emerged notion that vascular factors play a pathogenic role in the early stages of Alzheimer dementia.

Influence of hormonal replacement therapy on the regional cerebral blood flow in postmenopausal women

OBJECTIVES

The aim of this study was evaluation of the influence of hormonal replacement therapy (HRT) on the regional cerebral blood flow in postmenopausal women.

METHODS

The study group were 20 postmenopausal women, mean age 48.7 years (S.D. +/- 4.9 years). The control group were ten regularly menstruating women, mean age 32.6 years (S.D. +/- 13.2 years). In the studied group we measured the severity of climacteric syndrome with the use of Kupperman index and serum FSH and 17beta-estradiol level with the use of radioimmunological method. Cerebral blood flow was measured at rest using Single Photon Emission Computed Tomography (SPECT). Tracer accumulation evaluation was performed in three slices defined as: cerebellar slice, thalamic slice and ventricular slice, the reference region was delineated in the cerebellum. In ten women with an impairment in the cerebral blood flow at the beginning of the study all the tests were repeated after 12 months of HRT.

RESULTS

Before HRT mean value of the Kupperman index in the study group was 29.8 points (S.D. +/- 7.1 points); 17beta-estradiol 27 pg/ml (S.D. +/- 2 pg/ml); FSH 56 IU/l (S.D. +/- 49.5 IU/l); SPECT study revealed cerebral blood flow impairment in ten women. In all the studied slices cerebral blood flow was lower in the study group than in the controls. After 12 months of HRT the mean value of the Kupperman index in the study group was 13.2 points (S.D. +/- 2.1 points) (P < 0.05); 17beta-estradiol 44 pg/ml (S.D. +/- 25 pg/ml); FSH 36.4 IU/l (S.D. +/- 57.3 ng/ml); we found cerebral blood flow increase in all studied slices: right cerebellar slice: 5.2%; left cerebellar slice: 4.1%; right thalamic slice: 3.8%; left thalamic slice: 3.3%; right ventricular slice: 7.5%*; left ventricular slice: 6.7%* (* P < 0.05).

CONCLUSIONS

Cerebral blood flow is lower in the postmenopausal women than in regularly menstruating women. HRT increases regional cerebral blood flow and this improvement coexists with an increase of serum 17beta-estradiol level.

The role of neuroimaging in the diagnosis of vascular dementia

Vascular dementia (VaD) and Alzheimer's disease share many pathological and clinical characteristics. Whereas clinical criteria can help differentiate VaD from other types of dementia, neuroimaging is required for confirmation of vascular lesions. Neuroimaging also provides information about location and size of vascular lesions that can lead to a better understanding of symptoms and may help guide therapy.

The apolipoprotein E gene, attention, and brain function

The epsilon4 allele of the apolipoprotein E (ApoE) gene is associated with alterations in brain function and is a risk factor for Alzheimer's disease (AD). Changes in components of visuospatial attention with ApoE-epsilon4, aging, and AD are described. Healthy middle-aged adults without dementia who have the ApoE-epsilon4 gene show deficits in spatial attention and working memory that are qualitatively similar to those seen in clinically diagnosed AD patients. The findings support an association between ApoE polymorphism and specific components of visuospatial attention. Molecular mechanisms that may mediate the ApoE-attention link by modulating cholinergic neurotransmission to the posterior parietal cortex are discussed. Studies of attention and brain function in ApoE-epsilon4 carriers without dementia can advance knowledge of the genetics of visual attention, may enhance understanding of the preclinical phase of AD, and may lead to better methods for early AD detection.

Focal temporoparietal slow activity in Alzheimer's disease revealed by magnetoencephalography

BACKGROUND

Patients suffering from Alzheimer's disease exhibit more activity in the conventional electroencephalographic delta and theta bands. This activity concurs with atrophy and reduced metabolic and perfusion rates, particularly in temporoparietal structures.

METHODS

Whole-head magnetoencephalographic recordings were obtained from 15 patients diagnosed with Alzheimer's disease and 19 healthy control subjects during a resting condition. The generators of focal magnetic slow waves were located employing a single moving dipole model.

RESULTS

Dipole density in the delta and theta bands was enhanced in the Alzheimer's disease group compared with healthy control subjects. Slow-wave activity differed significantly between groups in temporoparietal regions of both hemispheres. Right temporoparietal slow-wave activity covaried with cognitive performance, whereas left temporal delta activity varied with a functional status scale.

CONCLUSIONS

Our results support the predominant role of the temporoparietal areas in the diagnosis of Alzheimer's disease. Magnetoencephalography and the source analysis of focal slow activity in particular provide interesting and potentially clinically useful tools to assess functional modifications of patients' brain and to evaluate its relationship with the cognitive status.

The apolipoprotein E gene, attention, and brain function

The epsilon4 allele of the apolipoprotein E (ApoE) gene is associated with alterations in brain function and is a risk factor for Alzheimer's disease (AD). Changes in components of visuospatial attention with ApoE-epsilon4, aging, and AD are described. Healthy middle-aged adults without dementia who have the ApoE-epsilon4 gene show deficits in spatial attention and working memory that are qualitatively similar to those seen in clinically diagnosed AD patients. The findings support an association between ApoE polymorphism and specific components of visuospatial attention. Molecular mechanisms that may mediate the ApoE-attention link by modulating cholinergic neurotransmission to the posterior parietal cortex are discussed. Studies of attention and brain function in ApoE-epsilon4 carriers without dementia can advance knowledge of the genetics of visual attention, may enhance understanding of the preclinical phase of AD, and may lead to better methods for early AD detection.

Alterations in cerebral blood flow and glucose utilization in mice overexpressing the amyloid precursor protein

We have used quantitative autoradiographic techniques to study the relationship between cerebral blood flow (CBF) and glucose utilization (CGU) in two lines of transgenic mice overexpressing Swedish mutant amyloid precursor protein (APP) and APP-derived Abeta peptides. Mice were studied at an age when there are no amyloid plaques. In the 2123 line, CBF was reduced only in telencephalic regions with no corresponding decrease in CGU. In 2576 transgenics, a line with higher levels of Abeta peptide, both CBF and CGU were reduced throughout the brain. The data indicate that Abeta induces alterations in resting CBF that are either associated with or independent of alterations in CGU and that occur in the absence of amyloid deposition in neuropil of blood vessels. These observations support the hypothesis that cerebrovascular and metabolic abnormalities are early events in the pathogenesis of Alzheimer's disease.

Single photon emission CT and positron emission tomography in the evaluation of neurologic disease

Widely available SPECT allows imaging of certain critical components of neurotransmission, providing clinically and experimentally significant information. Future efforts may be directed toward developing innovative techniques to delineate dynamic neurochemical changes in vivo.

Neuroimaging in dementia

Positron emission tomography, single photon emission computed tomography, and MR imaging are brain imaging techniques that have been applied widely to the study of patients with dementia. This article reviews current data on the clinical use of these techniques in the differential diagnosis of dementia and the prediction of dementia in those at risk.

Timing of disease progression by quantitative EEG in Alzheimer' s patients

This prospective study was planned to assess whether quantitative EEG (qEEG) can give an estimate of the timing of achievement of three endpoints (loss of activities of daily living, incontinence, and death) in 72 consecutive patients (53 females, 19 males; mean age, 70.8) affected with probable Alzheimer's disease, as defined according to the NINCDS-ADRDA criteria. Power-weighted, log-transformed relative values of the four conventional EEG bands were considered in a central-posterior temporal region for each hemisphere. The hypothesis was tested by the lifereg procedure of the Statistical Analysis System package (first significance level accepted, P < or = 0.01). Because patients were in different stages of the disease, the statistical analysis was performed in the entire group as well as in the subgroup of 41 patients (mean age, 69.6) with mild dementia (scoring 3 or 4 on the global deterioration scale). In the whole group, the loss of activities of daily living was predicted by delta power in either side (P = 0.01), incontinence was predicted by alpha power in the right side (P < 0.01), whereas the statistical significance was not reached for death (P < 0.05). In the subgroup of mild demented patients, the loss of activities of daily living was predicted by delta power in the left side (P = 0.01), incontinence by both delta (P < 0.01) and alpha (P < 0.001) power in the right side, and death was not significantly predicted (P = 0.08). Quantitative EEG is a low-cost, discomfort-free technique which may be used to obtain information on the timing of disease evolution. The results showed in mild Alzheimer's disease appear especially interesting to attempt a prediction of the future time course of the disease from its beginning.