[Alzheimer's disease and magnetic resonance spectroscopy of the hippocampus]

Protective effect of potassium 2-(l-hydroxypentyl)-benzoate on hippocampal neurons, synapses and dystrophic axons in APP/PS1 mice

RATIONALE

As the hub of memory and space, hippocampus is very sensitive to a wide variety of injuries and is one of the earliest brain structures to develop neurodegenerative changes in AD. Previous research has showed a protective effect of potassium 2-(l-hydroxypentyl)-benzoate (PHPB) on cognitive deficits in animal models of AD. However, it is unclear whether this protective effect is associated with hippocampal alterations.

OBJECTIVES

The present study was conducted to evaluate the protective effect of PHPB on hippocampal neurodegenerative changes in middle-aged APP/PS1 mice.

METHODS

Ten-month-old male APP/PS1 transgenic mice and age-matched wild-type mice were randomly divided into three groups. PHPB-treated APP/PS1 group received 30 mg/kg PHPB by oral gavage once daily for 12 weeks. Wild-type group and APP/PS1 group received the same volume of water alone. Twelve weeks later, mice (13-month-old) were tested for in vivo 1H-MRS examination and then sacrificed for subsequent biochemical and pathological examinations using transmission electron microscopy, Golgi staining, immunohistochemistry, and western blotting.

RESULTS

We found that PHPB treatment significantly improved the micromorphology of hippocampal neurons and subcellular organelles, ameliorated synapse loss and presynaptic axonal dystrophy, increased hippocampal dendritic spine density and dendritic complexity, enhanced the expression of hippocampal synapse-associated proteins, and improved hippocampal metabolism in middle-aged APP/PS1 mice.

CONCLUSIONS

Our study showed for the first time the protective effect of PHPB on hippocampal neurons, synapses, and dystrophic axons in APP/PS1 mice, which to some extent revealed the possible mechanism for its ability to improve cognition in animal models of AD.

Vascular dementia: Diagnostic criteria and supplementary exams. Recommendations of the Scientific Department of Cognitive Neurology and Aging of the Brazilian Academy of Neurology. Part I

Vascular dementia (VaD) is the most prevalent form of secondary dementia and the second most common of all dementias. The present paper aims to define guidelines on the basic principles for treating patients with suspected VaD (and vascular cognitive impairment - no dementia) using an evidence-based, systematized approach. The knowledge used to define these guidelines was retrieved from searches of several databases (Medline, Scielo, Lilacs) containing scientific articles, systematic reviews, meta-analyses, largely published within the last 15 years or earlier when pertinent. Information retrieved and selected for relevance was used to analyze diagnostic criteria and to propose a diagnostic system encompassing diagnostic criteria, anamnesis, as well as supplementary and clinical exams (neuroimaging and laboratory). Wherever possible, instruments were selected that had versions previously adapted and validated for use in Brazil that take into account both schooling and age. This task led to proposed protocols for supplementary exams based on degree of priority, for application in clinical practice and research settings.

Proton spectroscopy in Alzheimer's disease and cognitive impairment no dementia: a community-based study

OBJECTIVE

To describe the findings of proton magnetic resonance spectroscopy ((1)H-MRS) in Alzheimer's disease (AD) and cognitive impairment, no dementia (CIND) elderly from a community-based sample.

METHODS

Thirteen patients with AD, 12 with CIND and 15 normal individuals were evaluated. The (1)H-MRS was performed in the right temporal, left parietal and medial occipital regions studying the metabolites N-acetylaspartate (NAA), creatine (Cr), choline (Cho) and myoinositol (mI). The clinical diagnosis was based on standardized cognitive tests - MMSE and CAMDEX - and the results correlated with the (1)H-MRS.

RESULTS

Parietal Cho was higher in control individuals and lower in CIND subjects. AD and control groups were better identified by temporal and parietal mI combined with the temporal NAA/Cr ratio. CIND was better identified by parietal Cho.

CONCLUSION

The (1)H-MRS findings confirmed the hypothesis that metabolic alterations are present since the first symptoms of cognitively impaired elderly subjects. These results suggest that combining MRS from different cerebral regions can help in the diagnosis and follow-up of community elderly individuals with memory complaints and AD.

Evaluation of Alzheimer's disease by analysis of MR images using multilayer perceptrons and committee machines

Alzheimer's disease is the most common cause of dementia, yet hard to diagnose precisely without invasive techniques, particularly at the onset of the disease. This work approaches image analysis and classification of synthetic multispectral images composed by diffusion-weighted magnetic resonance (MR) cerebral images for the evaluation of cerebrospinal fluid area and its correlation with the advance of Alzheimer's disease. The MR images were acquired from a unique volunteer with Alzheimer's, using an image system based on a clinical 1.5T tomographer. The classification methods are based on multilayer perceptrons and committee machines and the classification results are used to correlate clinical and imaging findings. The classification results are used to improve the usual analysis of the ADC map.

Quantitative MR imaging in Alzheimer disease

Alzheimer disease (AD) is the most common type of dementia. It currently affects approximately 4 million people in the United States. AD is a progressive neurodegenerative disorder characterized by the gradual deposition of neuritic plaques and neurofibrillary tangles in the brain, which is thought to occur decades before the onset of clinical symptoms. Identification of people at risk before the clinical appearance of dementia has become a priority due to the potential benefits of therapeutic intervention. Although atrophy of medial temporal lobe structures has been shown to correlate with progression of AD, a growing number of recent reports have indicated that such atrophy may not be specific to AD. To improve diagnostic specificity, new quantitative magnetic resonance (MR) imaging methods are being developed that exploit known pathogenic mechanisms exclusive to AD. This article reviews the MR techniques that are currently available for the diagnostic assessment of AD.

Alzheimer's disease and proton magnetic resonance spectroscopy of limbic regions: a suggestion of a clinical-spectroscopic staging

OBJECTIVE

To compare magnetic resonance proton spectroscopic with clinical data and to propose a spectroscopic staging of Alzheimer's disease (AD).

METHOD

Subjects (n = 46), normals (12) and with AD (34), paired to age (CDR0-CDR3); AD diagnosis according to DSM-IV/NINCDS-ADRDA criteria; 1H-MRS with Signa Horizon LX-GE, 1.5T; single voxel at hippocampal region/HCR and posterior cingulate area/PCA.

RESULTS

Statistically significant decrease (p < 0.01) only of Naa/Cr--at HCR among the CDR0, CDR1+CDR2, and CDR3, and at PCA between CDR0 and CDR1+CDR2 in relation to CDR3.

CONCLUSION

The HCR is the first to show Naa reduction (CDR1). The PCA suffers later (CDR3). These values decline progressively according to the severity stages. Considering the disparities between the HCR and PCA it is possible to suggest a spectroscopic (metabolite) staging (MS) of AD, as follows: MS0 (-CDR0) = both normal HCR and PCA, MS1-2 (approximately CDR1-2) = abnormal HCR and normal PCA, and MS3 (approximately CDR3) = both abnormal HCR and PCA. These results make possible the early diagnosis, to follow the degenerative process throughout the course, and to suggest a spectroscopic staging related to the clinical stages of AD.

A multicenter reproducibility study of single-voxel 1H-MRS of the medial temporal lobe

Proton magnetic resonance spectroscopy ((1)H-MRS) has provided evidence for a reduction of N-acetyl-aspartate (NAA) in the medial temporal lobe (MTL) in cerebral disorders such as Alzheimer's Disease. Within the (1)H-MRS study of the German Research Network on Dementia, we determined the multicenter reproducibility of single-voxel (1)H-MRS of the MTL. At five sites with 1.5T MR systems, single-voxel (1)H spectra from the MTL of an identical healthy subject were measured. The same subject was also examined at one of the sites five times to assess intracenter stability. The protocol included water-suppressed spectra with TE 272 ms and TE 30 ms and unsuppressed spectra for absolute quantification of metabolite concentrations. The intracenter reproducibility of absolute NAA concentration, expressed as coefficient of variation (CV), was 1.8%. CV for the concentrations of creatine (Cr), choline (Cho), and myoinositol (MI) and for the ratios NAA/Cr, NAA/Cho, and MI/NAA varied by 11-16%. Intercenter CV was 3.9% for NAA and were below 10% for all other metabolites and metabolic ratios. Our study demonstrates that quantitative assessment of NAA with single-voxel MRS can be performed with high intercenter reproducibility. This is the basis for applying (1)H-MRS in large-scale early recognition and treatment studies in MTL affecting disorders.

Canavan disease: A white matter disorder

Breakdown of oligodendrocyte-neuron interactions in white matter (WM), such as the loss of myelin, results in axonal dysfunction and hence a disruption of information processing between brain regions. The major feature of leukodystrophies is the lack of proper myelin formation during early development or the onset of myelin loss late in life. These early childhood WM diseases are described as hypomyelination or dysmyelination arising from a primary block in normal myelin synthesis because of a genetic mutation expressed in oligodendrocytes, or failure in myelination secondary to neuronal or astroglial dysfunctions (van der Knaap 2001 Dev. Med. Child Neurol. 43:705-712). Here, we describe the pathophysiological parameters of Canavan disease (CD), caused by genetic mutations of the aspartoacylase (ASPA) gene, a metabolic enzyme restricted in the central nervous system (CNS) to oligodendrocytes. CD presents pathophysiological dysfunctions similar to diseases caused by myelin gene mutations, such as Pelizaeus-Merzbacher disease (PMD) and several animal models, such as myelin deficient rat (md), jimpy (jp), shiverer (sh), and quaking (qk viable) mutant mice. These single gene mutations have pleiotropic effects, whereby the alteration of one myelin gene expression disrupts functional expression of other oligodendrocyte genes with an outcome of hypomyelination/dysmyelination. Among all of the known leukodystrophies, CD is the first disorder, which was approved and tested for the adeno-associated virus vector (AAV)-ASPA gene therapy (Leone et al. 2000 Ann. Neurol. 48:27-38; Janson et al. 2001 Trends Neurosci. 24:706-712) without much success following the first two attempts. ASPA gene delivery attempts in animal models have shown a lowering of N-acetyl L-aspartate and a change in motor functions, while sponginess of the WM, a characteristic of CD remained unchanged (Matalon et al. 2003 Mol. Ther. 7 (5, Part 1):580-587; McPhee et al. 2005 Brain Res. Mol. Brain Res. 135:112-121) even with better viral serotype and delivery of the gene during early phase of development (Klugmann et al. 2005 Mol. Ther. 11:745-753). While different approaches are being sought for the success of gene therapy, there are pivotal developmental questions to address regarding the specific regions of the CNS and cell lineages that become the target for the onset and progression of CD symptoms from early to late stages of development.

[Proton spectroscopy in Alzheimer's disease and cognitive impairment not dementia: a community study]

OBJECTIVE

To describe the proton magnetic resonance spectroscopy (1H-ERM) data in Alzheimer's disease (AD) and Cognitive Impairment Not Dementia (CIND) in a community sample.

METHOD

We investigated subjects with AD (n=6), CIND (n=7) and normal control (n=7). 1H-ERM was performed with single voxel (8 cm3) placed in temporal, parietal and occipital regions and studied metabolites were: N-acetylaspartate (NAA), creatine (Cr), choline (Cho) and myo-inositol (mI).

RESULTS

NAA concentration was higher in control subjects than AD and intermediated in CIND patients. Cho parietal plus occipital and Cr parietal plus Cho occipital classified correctly 92.3% of subjects Control vs AD. Temporal mI classified 78.6% of subjects between Control vs CIND.

CONCLUSION

Spectroscopy can be used in the diagnosis and follow-up of individuals with cognitive impairment; evaluation of community subjects may show different patterns of brain metabolites distribution.

A comparative study of the different N-acetylaspartate measures of the medial temporal lobe in Alzheimer's disease

OBJECTIVE

To investigate group differences and correlations and to determine the sensitivity and specificity of different measures of the neuronal marker N-acetylaspartate (NAA) in the medial temporal lobe of Alzheimer's Disease (AD) patients.

METHODS

The metabolic ratio NAA/creatine (Cr), the absolute concentration of NAA referenced against brain tissue (BT) water and NAA multiplied with the amount of BT in the proton magnetic resonance spectroscopy (1H-MRS) voxel were assessed in patients and healthy controls with a single-voxel 1H-MRS protocol.

RESULTS

All measures were significantly lower in AD patients compared with controls. NAA/Cr and NAA correlated weakly, and there was no correlation of NAA with the amount of BT in the voxel. The highest specificity (87%) at a sensitivity of 80% was observed for NAA multiplied with the amount of BT in the voxel. There was no correlation of the MMSE with any of the NAA parameters.

CONCLUSIONS

NAA/Cr does not reflect NAA concentration very well. NAA is not correlated with brain atrophy. The BT volume in the 1H-MRS voxel in combination with the concentration of NAA discriminates AD from healthy controls sufficiently.

Diagnóstico de doença de Alzheimer no Brasil: critérios diagnósticos e exames complementares. Recomendações do Departamento Científico de Neurologia Cognitiva e do Envelhecimento da Academia Brasileira de Neurologia

Este consenso teve o objetivo de recomendar condutas baseadas em evidências para o diagnóstico clínico de doença de Alzheimer (DA) em nosso meio. Foram avaliados sistematicamente consensos elaborados em outros países e artigos sobre o diagnóstico de DA no Brasil disponíveis no PUBMED ou LILACS. Concluiu-se que o diagnóstico de demência deve basear-se nos critérios do Manual de Diagnóstico e Estatística da Associação Psiquiátrica Americana (DSM) e o de DA, nos de McKhann et al. (NINCDS-ADRDA). Os exames complementares recomendados são: hemograma completo, concentrações séricas de uréia, creatinina, tiroxina livre, hormônio tíreo-estimulante, albumina, enzimas hepáticas, vitamina B12 e cálcio, reações sorológicas para sífilis e, em pacientes com idade inferior a 60 anos, sorologia para HIV. Exame do líquido cefalorraqueano está indicado em situações particulares. Tomografia computadorizada (ou preferentemente ressonância magnética, quando disponível) é exame obrigatório e tem a finalidade principal de excluir outras doenças. Cintilografia de perfusão (SPECT) e EEG são métodos opcionais.