Cognitive impairment: classification by 1H magnetic resonance spectroscopy

Proton magnetic resonance spectroscopy of N-acetyl aspartate in first depressive episode and chronic major depressive disorder: A systematic review and meta-analysis

N-acetyl aspartate (NAA) is a marker of neuronal integrity and metabolism. Deficiency in neuronal plasticity and hypometabolism are implicated in Major Depressive Disorder (MDD) pathophysiology. To test if cerebral NAA concentrations decrease progressively over the MDD course, we conducted a pre-registered meta-analysis of Proton Magnetic Resonance Spectroscopy (1H-MRS) studies comparing NAA concentrations in chronic MDD (n = 1308) and first episode of depression (n = 242) patients to healthy controls (HC, n = 1242). Sixty-two studies were meta-analyzed using a random-effect model for each brain region. NAA concentrations were significantly reduced in chronic MDD compared to HC within the frontal lobe (Hedges' g = -0.330; p = 0.018), the occipital lobe (Hedges' g = -0.677; p = 0.007), thalamus (Hedges' g = -0.673; p = 0.016), and frontal (Hedges' g = -0.471; p = 0.034) and periventricular white matter (Hedges' g = -0.478; p = 0.047). We highlighted a gap of knowledge regarding NAA levels in first episode of depression patients. Sensitivity analyses indicated that antidepressant treatment may reverse NAA alterations in the frontal lobe. We highlighted field strength and correction for voxel grey matter as moderators of NAA levels detection. Future studies should assess NAA alterations in the early stages of the illness and their longitudinal progression.

Mitochondria in Alzheimer's disease and their potential role in Alzheimer's proteostasis

Alzheimer's disease (AD) is a progressive brain disorder characterized by memory loss and the accumulation of two insoluble protein aggregates, tau neurofibrillary tangles and beta-amyloid plaques. Widespread mitochondrial dysfunction also occurs and mitochondria from AD patients display changes in number, ultrastructure, and enzyme activities. Mitochondrial dysfunction in AD presumably links in some way to its other disease characteristics, either as a cause or consequence. This review characterizes AD-associated mitochondrial perturbations and considers their position in its pathologic hierarchy. It focuses on the crosstalk that occurs between mitochondria, nuclear gene expression, and cytosolic signaling pathways that serves to maintain cell homeostasis. To this point, recent evidence indicates mitochondria trigger retrograde responses that influence cell proteostasis in general and AD proteostasis specifically. Potentially pertinent retrograde responses include the mitochondrial unfolded protein response (mtUPR), integrated stress response (ISR), autophagy/mitophagy, and proteasome function. A fuller perspective of mitochondrial dysfunction in AD, and its relation to protein aggregation, could enhance our overall understanding of this disease.

MR approaches in neurodegenerative disorders

Neurodegenerative disease is the umbrella term which refers to a range of clinical conditions causing degeneration of neurons within the central nervous system leading to loss of brain function and eventual death. The most prevalent of these is Alzheimer's disease (AD), which affects approximately 50 million people worldwide and is predicted to reach 75 million by 2030. Neurodegenerative diseases can only be fully diagnosed at post mortem by neuropathological assessment of the type and distribution of protein deposits which characterise each different condition, but there is a clear role for imaging technologies in aiding patient diagnoses in life. Magnetic resonance imaging (MRI) and spectroscopy (MRS) techniques have been applied to study these conditions for many years. In this review, we consider the range of MR-based measurements and describe the findings in AD, but also contrast these with the second most common dementia, dementia with Lewy bodies (DLB). The most definitive observation is the major structural brain changes seen in AD using conventional T1-weighted (T1w) MRI, where medial temporal lobe structures are notably atrophied in most symptomatic patients with AD, but often preserved in DLB. Indeed these findings are sufficiently robust to have been incorporated into clinical diagnostic criteria. Diffusion tensor imaging (DTI) reveals widespread changes in tissue microstructure, with increased mean diffusivity and decreased fractional anisotropy reflecting the degeneration of the white matter structures. There are suggestions that there are subtle differences between AD and DLB populations. At the metabolic level, atrophy-corrected MRS demonstrates reduced density of healthy neurons in brain areas with altered perfusion and in regions known to show higher deposits of pathogenic proteins. As studies have moved from patients with advanced disease and clear dysfunction to patients with earlier presentation such as with mild cognitive impairment (MCI), which in some represents the first signs of their ensuing dementia, the ability of MRI to detect differences has been weaker and further work is still required, ideally in much larger cohorts than previously studied. The vast majority of imaging research in dementia populations has been univariate with respect to the MR-derived parameters considered. To date, none of these measurements has uniquely replicated the patterns of tissue involvement seen by neuropathology, and the ability of MR techniques to deliver a non-invasive diagnosis eludes us. Future opportunities may lie in combining MR and nuclear medicine approaches (position emission tomography, PET) to provide a more complete view of structural and metabolic changes. Such developments will require multi-variate analyses, possibly combined with artificial intelligence or deep learning algorithms, to enhance our ability to combine the array of image-derived information, genetic, gender and lifestyle factors.

Brain amyloid burden and cerebrovascular disease are synergistically associated with neurometabolism in cognitively unimpaired older adults

Alzheimer's disease (AD) is the most common cause of cognitive dysfunction in older adults. The pathological hallmarks of AD such as beta amyloid (Aβ) aggregation and neurometabolic change, as indicated by altered myo-inositol (mI) and N-acetylaspartate (NAA) levels, typically precede the onset of cognitive dysfunction by years. Furthermore, cerebrovascular disease occurs early in AD, but the interplay between vascular and neurometabolic brain change is largely unknown. Thirty cognitively normal older adults (age = 70 ± 5.6 years, Mini-Mental State Examination = 29.2 ± 1) received 11-C-Pittsburgh Compound B positron emission tomography for estimating Aβ-plaque density, 7 Tesla fluid-attenuated inversion recovery magnetic resonance imaging for quantifying white matter hyperintensity volume as a marker of small vessel cerebrovascular disease and high-resolution magnetic resonance spectroscopic imaging at 7 Tesla, based on free induction decay acquisition localized by outer volume suppression to investigate tissue-specific neurometabolism in the posterior cingulate and precuneus. Aβ (β = 0.45, p = 0.018) and white matter hyperintensities (β = 0.40, p = 0.046) were independently and interactively (β = -0.49, p = 0.026) associated with a higher ratio of mI over NAA (mI/NAA) in the posterior cingulate and precuneus gray matter but not in the white matter. Our data suggest that cerebrovascular disease and Aβ burden are synergistically associated with AD-related gray matter neurometabolism in older adults.

Decreased Glutamate Levels in Patients with Amnestic Mild Cognitive Impairment: An sLASER Proton MR Spectroscopy and PiB-PET Study

BACKGROUND AND PURPOSE

Glutamate levels may be informative about the declining neuronal health in the central nervous system. We used an advanced proton MR spectroscopy (¹ H-MRS) protocol composed of semi-localization by adiabatic selective refocusing (sLASER) localization and FAST(EST)MAP shimming for detection of alterations in brain glutamate concentrations in patients with amnestic mild cognitive impairment.

METHODS

Participants with amnestic mild cognitive impairment (n = 14; median age = 80) and age- and sex-matched clinically normal controls (n = 32; median age = 79) from the population-based Mayo Clinic Study of Aging were recruited prospectively to the 3T single-voxel ¹ H-MRS study that examined metabolite changes in the posterior cingulate gyri. To be included, controls had to have low β-amyloid load on [¹¹ C] Pittsburgh Compound B (PiB)-PET (standard uptake value ratio; SUVr < 1.42) and patients with amnestic mild cognitive impairment had to have high β-amyloid load (SUVr ≥ 1.42).

RESULTS

Glutamate concentration and the glutamate/myo-inositol ratio were lower in patients with amnestic mild cognitive impairment than clinically normal controls (P < .05). Higher global cortical PiB-PET SUVr correlated with lower glutamate/myo-inositol (r = -.3, P = .04).

CONCLUSIONS

The advanced sLASER with FAST(EST)MAP shimming is a promising protocol for identifying glutamate alterations. Advanced ¹ H-MRS protocols may add to the understanding of early Alzheimer's disease pathophysiology through detection of glutamate concentration in posterior cingulate gyri of individuals with amnestic mild cognitive impairment.

Magnetic Resonance Spectroscopy in Alzheimer's Disease: Systematic Review and Meta-Analysis

BACKGROUND

The application of non-invasive proton magnetic resonance spectroscopy (1H-MRS) could potentially identify changes in cerebral metabolites in the patients with Alzheimer's disease (AD). However, whether these metabolites can serve as biomarkers for the diagnosis of AD remains unclear.

OBJECTIVE

Using meta-analysis, we aimed to investigate the patterns of cerebral metabolite changes in several cerebral regions that are strongly associated with cognitive decline in AD patients.

METHODS

Using Hedges' g effect size, a systematic search was performed in PubMed, Cochrane Library, Ovid, Embase, and EBSCO, and 38 studies were integrated into the final meta-analysis.

RESULTS

According to the observational studies, N-acetyl aspartate (NAA) in AD patients was significantly reduced in the posterior cingulate (PC) (effect size (ES) =-0.924, p <  0.005) and bilateral hippocampus (left hippocampus: ES =-1.329, p <  0.005; right hippocampus: ES =-1.287, p <  0.005). NAA/Cr (creatine) ratio decreased markedly in the PC (ES =-1.052, p <  0.005). Simultaneously, significant elevated myo-inositol (mI)/Cr ratio was found not only in the PC but also in the parietal gray matter. For lack of sufficient data, we failed to elucidate the efficacy of pharmacological interventions with the metabolites changes.

CONCLUSION

The available data indicates that NAA, mI, and the NAA/Cr ratio might be potential biomarkers of brain dysfunction in AD subjects. Choline (Cho)/Cr and mI/NAA changes might also contribute toward the diagnostic process. Thus, large, well-designed studies correlated with cerebral metabolism are needed to better estimate the cerebral extent of alterations in brain metabolite levels in AD patients.

Proton MRS in mild cognitive impairment

Mild cognitive impairment (MCI) is a clinical syndrome operationalized for early diagnosis and treatment of Alzheimer's disease (AD). Many individuals with MCI are at the prodromal stage of AD or other dementia. Various quantitative magnetic resonance imaging (MRI) techniques that measure the anatomic, biochemical, microstructural, functional, and blood-flow changes are being evaluated as possible surrogate measures for early diagnosis and disease progression in MCI. The pathology underlying MCI is heterogeneous, dominated by AD, cerebrovascular disease, Lewy body disease, or a mixture of these pathologies in autopsy cohorts. Proton magnetic resonance spectroscopy ((1)H MRS) metabolite markers may help identify and track etiologies that typically underlie MCI in the elderly. The role of proton MRS will be critical for pathophysiological processes for which a reliable biomarker does not exist such as neuronal dysfunction, glial and microglial activation in MCI.

Magnetic resonance imaging study cannot individually distinguish individuals with mild cognitive impairment, mild Alzheimer's disease, and normal aging

OBJECTIVE

To evaluate the volumetric and spectroscopy aspects of hippocampus in patients with mild Alzheimer's disease (AD) and mild cognitive impairment (MCI).

METHODS

A series of patients older than 65 years and with memory deficit were studied.

RESULTS

The evocation of words test presented a significant reduction in the number of words recalled by the patients with MCI and mild AD as compared with the control group. Bilateral reduction of the hippocampus volume in the AD group was observed when compared to the control group. There were no statistical differences in the values of NAA/Cr, mI/Cr, Cho/Cr and mI/NAA between the groups.

CONCLUSIONS

Magnetic resonance imaging study failed to individually distinguish patients with MCI, mild AD and normal aging. However, patients with mild AD presented loss of asymmetry between the right and left hippocampus, and a reduction in hippocampus volume.

Therapeutic and preventive effects of methylene blue on Alzheimer's disease pathology in a transgenic mouse model

Methylene blue (MB) belongs to the phenothiazinium family. It has been used to treat a variety of human conditions and has beneficial effects on the central nervous system in rodents with and without brain alteration. The present study was designed to test whether chronic MB treatment taken after (therapeutic effect) or before (preventive effect) the onset of beta-amyloid pathology influences cognition in a transgenic mouse model (APP/PS1). In addition, the present study aims at revealing whether these behavioral effects might be related to brain alteration in beta-amyloid deposition. To this end, we conducted an in vivo study and compared two routes of drug administration, drinking water versus intraperitoneal injection. Results showed that transgenic mice treated with MB orally or following intraperitoneal injection were protected from cognitive impairments in a variety of social, learning, and exploratory tasks. Immunoreactive beta-amyloid deposition was significantly reduced in the hippocampus and adjacent cortex in MB-treated transgenic mice. Interestingly, these beneficial effects were observed independently of beta-amyloid load at the time of MB treatment. This suggests that MB treatment is beneficial at both therapeutic and preventive levels. Using solid-state High Resolution Magic Angle Spinning Nuclear Magnetic Resonance (HRMAS-NMR), we showed that MB administration after the onset of amyloid pathology significantly restored the concentration of two metabolites related to mitochondrial metabolism, namely alanine and lactate. We conclude that MB might be useful for the therapy and prevention of Alzheimer's disease. This article is part of the Special Issue entitled 'The Synaptic Basis of Neurodegenerative Disorders'.

1H-MR spectroscopy metabolite levels correlate with executive function in vascular cognitive impairment

BACKGROUND

White matter hyperintensities (WMHs) are associated with vascular cognitive impairment (VCI) but fail to correlate with neuropsychological measures. As proton MR spectroscopy ((1)H-MRS) can identify ischaemic tissue, we hypothesised that MRS detectable brain metabolites would be superior to WMHs in predicting performance on neuropsychological tests.

METHODS

60 patients with suspected VCI underwent clinical, neuropsychological, MRI and CSF studies. They were diagnosed as having subcortical ischaemic vascular disease (SIVD), multiple infarcts, mixed dementia and leukoaraiosis. We measured brain metabolites in a white matter region above the lateral ventricles with (1)H-MRS and WMH volume in this region and throughout the brain.

RESULTS

We found a significant correlation between both total creatine (Cr) and N-acetylaspartyl compounds (NAA) and standardised neuropsychological test scores. Cr levels in white matter correlated significantly with executive function (p=0.001), attention (p=0.03) and overall T score (p=0.007). When lesion volume was added as a covariate, NAA also showed a significant correlation with executive function (p=0.003) and overall T score (p=0.015). Furthermore, while metabolite levels also correlated with total white matter lesion volume, adjusting the Cr levels for lesion volume did not diminish the strength of the association between Cr levels and neuropsychological scores. The lowest metabolite levels and neuropsychological scores were found in the SIVD group. Finally, lesion volume alone did not correlate significantly with any neuropsychological test score.

CONCLUSION

These results suggest that estimates of neurometabolite levels provide additional and useful information concerning cognitive function in VCI not obtainable by measurements of lesion load.

MAGNETIC RESONANCE SPECTROSCOPY IN EVALUATION OF COGNITIVE FUNCTIONS IN PATIENTS WITH METABOLIC SYNDROME

Objective. To evaluate the role of magnetic resonance spectroscopy (MR-spectroscopy) in the study of cognitive functions in patients with metabolic syndrome (MS).

Design and methods. The study included patients with MS (10 patients without cognitive impairment and 11 subjects with cognitive dysfunction). All patients underwent neuropsychological testing, and cognitive evoked potential for the assessment of cognitive functions. Brain metabolism was studied by proton MR-spectroscopy.

Results. In patients with MS and cognitive impairment, and without cognitive dysfunction no morphological changes in the brain according to the magnetic resonance imaging (MRI) were found. According to MR-spectroscopy of the brain in patients with MS and cognitive dysfunction the metabolism impairment is primarily associated with the increase in lactate and inositol.

Conclusion. Indicators of neuropsychological testing, the cognitive evoked potential are associated with the violation of brain metabolism in patients with MS and cognitive impairment.

Magnetic resonance spectroscopy in common dementias

Neurodegenerative dementias are characterized by elevated myoinositol and decreased N-acetylaspartate (NAA) levels. The increase in myoinositol seems to precede decreasing NAA levels in Alzheimer's diseases. NAA/myo-inositol ratio in the posterior cingulate gyri decreases with increasing burden of Alzheimer's disease pathologic conditions. Proton magnetic resonance spectroscopy ((1)H MRS) is sensitive to the pathophysiologic processes associated with the risk of dementia in patients with mild cognitive impairment. Although significant progress has been made in improving the acquisition and analysis techniques in (1)H MRS, translation of these technical developments to clinical practice have not been effective because of the lack of standardization for multisite applications and normative data and an insufficient understanding of the pathologic basis of (1)H MRS metabolite changes.

Magnetic resonance spectroscopy in Alzheimer's disease

Aging is the primary risk factor for dementia. With increasing life expectancy and aging populations worldwide, dementia is becoming one of the significant public health problems of the century. The most common pathology underlying dementia in older adults is Alzheimer's disease. Proton magnetic resonance spectroscopy (MRS) may provide a window into the biochemical changes associated with the loss of neuronal integrity and other neurodegenerative pathology that involve the brain before the manifestations of cognitive impairment in patients who are at risk for Alzheimer's disease. This review focuses on proton MRS studies in normal aging, mild cognitive impairment, and dementia, and how proton MRS metabolite levels may be potential biomarkers for early diagnosis of dementia-related pathologic changes in the brain.

N-acetylaspartate, choline, myoinositol, glutamine and glutamate (glx) concentration changes in proton MR spectroscopy (1H MRS) in patients with mild cognitive impairment (MCI)

Background

Purpose of study was evaluation of regional metabolic disorders using ¹H MRS in patients with MCI, as a predictor of clinical conversion to dementia based on clinical follow-up.

Material/Methods

The study group consisted of 31 subjects with diagnosis of MCI based on criteria the Mayo Clinic Group. ¹H MRS was performed with a single-voxel method using PRESS sequence. The volume of interest (VOI) was located in the hippocampal formation and posterior part of the cingulated gyrus.

Results

Patients had annual clinical control at least twice. At the beginning, 9 had amnestic MCI and the others had multidomain MCI. During follow-up (median 3 yrs) 8 subjects had stable disease (SD), 13 had disease progression (DP) and 10 develop Alzheimer disease (AD). Baseline metabolic ratios (¹H MRS) between 3 groups indicated significant difference (P<0.05) in left frontal lobe in mI/H₂0 ratio, between patients with SD (0.27) and DP. In comparing the groups with DP and AD, a significant difference in NAA/Cr (1.77 vs. 1.43) was found. A significant difference within left temporal external lobes was found between SD and DP in NAA/H₂O ratio (0.55 vs. 0.51). An additional significant difference within medial temporal lobe was found between DP and AD in Glx/H₂O ratio (0.44 vs. 0.34) on the right side.

Conclusions

¹H MRS seems to be sensitive method allows prediction of which patients are liable to progress from MCI to AD. Combined with other biomarkers of disease staging, it is an important approach in the preclinical AD diagnosis, as well as the assessment of dementia progression.

Using proton magnetic resonance spectroscopy to identify mild cognitive impairment

BACKGROUND

Single-volume proton magnetic resonance spectroscopy (1H MRS) has considerable diagnostic potential for Alzheimer's disease (AD). This study investigated 1H MRS in specific regions of the brain, the posterior cingulate gyri (PCG) and the hippocampus, in patients with AD, amnestic mild cognitive impairment (aMCI), and in normal control subjects.

METHODS

1H MRS analysis was carried out on 47 patients with AD, 32 patients with aMCI and 56 normal control subjects (NC group). Volumes of the PCG and hippocampus were assessed, and the metabolic signals of N-acetylaspartate (NAA), choline compounds (Cho), myo-inositol (mI), and creatine (Cr) were quantified.

RESULTS

In the PCG, differences between the test groups were found in NAA/Cr, Cho/Cr, mI/Cr and NAA/mI ratios. Group differences were also found in mI/Cr and NAA/mI ratios in the left hippocampus, and in mI/Cr and NAA/mI ratios in the right hippocampus. NAA/Cr ratios increased in the PCG between AD and aMCI patients, and between aMCI and NC patients. Conversely, mI/Cr ratios in the PCG and left hippocampus decreased across AD, aMCI, and NC subjects. In discriminate and ROC (Receiver Operating Characteristic) analyses, a NAA/Cr ratio of ≤ 1.50 in the PCG indicated optimal potential for discriminating between aMCI patients and normal control subjects. Discriminating potential was also found to be high for a NAA/mI ratio in the PCG of ≤ 2.72. Despite significant differences between NC and aMCI patients in the mI/Cr ratio in the PCG and in the NAA/mI ratio in the left hippocampus, their sensitivity and specificity were all lower than 75%.

CONCLUSION

Proton MRS of the PCG using the NAA/Cr ratio as a metabolic marker indicates considerable potential for distinguishing between aMCI and NC subjects.

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.

Transient gastric irritation in the neonatal rats leads to changes in hypothalamic CRF expression, depression- and anxiety-like behavior as adults

AIMS

A disturbance of the brain-gut axis is a prominent feature in functional bowel disorders (such as irritable bowel syndrome and functional dyspepsia) and psychological abnormalities are often implicated in their pathogenesis. We hypothesized that psychological morbidity in these conditions may result from gastrointestinal problems, rather than causing them.

METHODS

Functional dyspepsia was induced by neonatal gastric irritation in male rats. 10-day old male Sprague-Dawley rats received 0.1% iodoacetamide (IA) or vehicle by oral gavage for 6 days. At 8-10 weeks of age, rats were tested with sucrose preference and forced-swimming tests to examine depression-like behavior. Elevated plus maze, open field and light-dark box tests were used to test anxiety-like behaviors. ACTH and corticosterone responses to a minor stressor, saline injection, and hypothalamic CRF expression were also measured.

RESULTS

Behavioral tests revealed changes of anxiety- and depression-like behaviors in IA-treated, but not control rats. As compared with controls, hypothalamic and amygdaloid CRF immunoreactivity, basal levels of plasma corticosterone and stress-induced ACTH were significantly higher in IA-treated rats. Gastric sensory ablation with resiniferatoxin had no effect on behaviors but treatment with CRF type 1 receptor antagonist, antalarmin, reversed the depression-like behavior in IA-treated rats

CONCLUSIONS

The present results suggest that transient gastric irritation in the neonatal period can induce a long lasting increase in depression- and anxiety-like behaviors, increased expression of CRF in the hypothalamus, and an increased sensitivity of HPA axis to stress. The depression-like behavior may be mediated by the CRF1 receptor. These findings have significant implications for the pathogenesis of psychological co-morbidity in patients with functional bowel disorders.

Current strategies in the discovery of small-molecule biomarkers for Alzheimer’s disease

With the number of patients suffering from Alzheimer’s disease rapidly increasing, there is a major requirement for an accurate biomarker capable of diagnosing the disease early. Much of the research is focused on protein and genetic approaches; however, small molecules may provide viable marker molecules. Examples that support this approach include known abnormalities in lipid metabolism, glucose utilization and oxidative stress, which have been demonstrated in patients suffering from the disease. Therefore, by-products of this irregular metabolism may provide accurate biomarkers. In this review we present the current approaches previously published in the literature used to investigate potential small-molecule and metabolite markers, and report their findings. A wide range of techniques are discussed, including separation approaches (LC, GC and CE), magnetic resonance technologies (NMR and magnetic resonance spectroscopy), and immunoassays.

Short echo time proton magnetic resonance spectroscopy in Alzheimer's disease: a longitudinal multiple time point study

Short echo time localized proton magnetic resonance spectroscopy provides quantification of brain metabolites, including N-acetyl-aspartate, myo-inositol, creatine/phosphocreatine and choline-containing compounds, which may be useful biomarkers for monitoring Alzheimer's disease. We aimed to quantify the rate of metabolite change in Alzheimer's disease, to assess factors influencing changes and to investigate the potential for serial magnetic resonance spectroscopy as an Alzheimer's disease trial biomarker. A total of 42 patients and 22 controls each had up to six magnetic resonance spectroscopy examinations over a 2-year period, using a midline posterior cingulate single-voxel point resolved spectroscopy sequence (1.5 T; time to repetition = 2000 ms; echo time = 30 ms; 192 averages). Metabolite ratios N-acetyl-aspartate:creatine/phosphocreatine, choline-containing compounds:creatine/phosphocreatine, and myo-inositol:creatine/phosphocreatine were measured using online software (PROBE-Q) and the N-acetyl-aspartate:myo-inositol ratio was derived. Baseline ratios were compared between patients and controls. A linear mixed model was used to quantify longitudinal changes and extended to assess the effect of age, disease severity and baseline use of acetylcholinesterase inhibitors. Patients and controls were matched for age (patients: 68.9 ± 7.2 years; controls: 69.1 ± 6.7 years); 71% of the patients were on acetylcholinesterase inhibitors at baseline; mean Mini-Mental State Examination for patients was 19.4 ± 4.1. A total of 307 spectra were acquired. In cross-sectional analyses, patients were significantly different from controls for N-acetyl-aspartate:creatine/phosphocreatine (11% lower, P < 0.001), N-acetyl-aspartate:myo-inositol (24% lower, P < 0.001), and myo-inositol:creatine/phosphocreatine (17% higher, P < 0.001). After adjustment for N-acetyl-aspartate:myo-inositol, none of the other variables differed significantly. In patients there was significant decline in N-acetyl-aspartate:creatine/phosphocreatine (mean: 2.2%/year; 95% confidence interval: 0.9-3.5) and N-acetyl-aspartate:myo-inositol (mean: 3.7%/year; 95% confidence interval: 1.7-5.7), with no evidence for influence by age, disease severity or acetylcholinesterase inhibitor use. There was significant excess decline in patients compared with controls only in N-acetyl-aspartate:myo-inositol (mean: 3.6%/year; 95% confidence interval: 0.8-6.4; P = 0.014). Between-subject standard deviation for N-acetyl-aspartate:myo-inositol was 0% for controls and 3.5%/year for patients; within-subject standard deviation for a 1 year, two-time-point study was 9.2%/year for both patients and controls. These results confirm that magnetic resonance spectroscopy can be used to quantify excess metabolite decline in Alzheimer's disease, which may provide a useful measure of disease progression. We found no evidence that age, disease severity or acetylcholinesterase inhibitor use influenced rate of decline, although numbers were small. The substantial variability in longitudinal measurements that drives sample size requirements is principally within-subject and technique related: technical developments to reduce this variability may make serial magnetic resonance spectroscopy a viable biomarker in clinical trials for Alzheimer's disease.

[MR spectroscopy in dementia]

With an increasingly aging population we are faced with the problem of an increasing number of dementia patients. In addition to clinical, neuropsychological and laboratory procedures, MRI plays an important role in the early diagnosis of dementia. In addition to various morphological changes functional changes can also help in the diagnosis and differential diagnosis of dementia. Overall the diagnosis of dementia can be improved by using parameters from MR spectroscopy. This article focuses on MR spectroscopic changes in the physiological aging process as well as on changes in mild cognitive impairment a precursor of Alzheimer's dementia, in Alzheimer's dementia, frontotemporal dementia, vascular dementia and Lewy body dementia.

Selective lamina dysregulation in granular retrosplenial cortex (area 29) after anterior thalamic lesions: an in situ hybridization and trans-neuronal tracing study in rats

There is growing evidence that lesions of the anterior thalamic nuclei cause long-lasting intrinsic changes to retrosplenial cortex, with the potential to alter its functional properties. The present study had two goals. The first was to identify the pattern of changes in eight markers, as measured by in-situ hydridisation, in the granular retrosplenial cortex (area Rgb) following anterior thalamic lesions. The second was to use retrograde trans-neuronal tracing methods to identify the potential repercussions of intrinsic changes within granular retrosplenial cortex. In Experiment 1, adult rats received unilateral lesions of the anterior thalamic nuclei and were perfused 4 weeks later. Of the eight markers, four (c-fos, zif268, 5ht2rc, kcnab2) showed a very similar pattern of change, with decreased levels in superficial retrosplenial cortex (lamina II) in the ipsilateral hemisphere but little or no change in deeper layers (lamina V). A fifth marker (cox6b) showed a shift in activity levels in the opposite direction to the previous four markers. Three other markers (cox6a1, CD74, ncs-1) did not appear to change activity levels after surgery. The predominant pattern of change, a decrease in superficial cortical activity, points to potential alterations in plasticity and metabolism. In Experiment 2, wheat germ agglutin (WGA) was injected into the anterior thalamic nuclei in rats given different survival times, sometimes in combination with the retrograde, fluorescent tracer, Fast Blue. Dense aggregations of retrogradely labeled cells were always found in lamina VI of granular retrosplenial cortex, but additional labeled cells in lamina II were only found: (1) in WGA cases, that is never after Fast Blue injections, and (2) after longer WGA survival times (3 days). These layer II Rgb cells are likely to have been trans-neuronally labeled, revealing a pathway from lamina II of Rgb to those deeper retrosplenial cells that project directly to the anterior thalamic nuclei.

Diffusion tensor imaging of the posterior cingulate is a useful biomarker of mild cognitive impairment

OBJECTIVES

Mild cognitive impairment (MCI) is recognized as a predementia state, but its definition is inconsistent and only 20%-30% develop dementia after 2 years. Biomarkers may help identify individuals at greatest risk of progressive decline. The authors examine a novel neuroimaging technique, diffusion tensor imaging (DTI) as a potential biomarker of MCI.

DESIGN

Cross-sectional prospective study.

SETTING

Subjects were recruited randomly using the electoral roll from two electorates in East Sydney, Australia.

PARTICIPANTS

A community-dwelling sample (N = 249) and age 70-90 years.

MEASUREMENTS

Screening to exclude dementia, comprehensive neuropsychiatric assessment, cognitive test battery, structural magnetic resonance imaging and DTI to obtain measures of fractional anisotropy (FA) and mean diffusivity (MD). MCI was diagnosed by standard criteria.

RESULTS

After controlling for age, sex, and years of education, the amnestic MCI (aMCI) group demonstrated microstructural pathology in the parahippocampal white matter, frontal white matter, splenium of corpus callosum, and posterior cingulate region. The nonamnestic MCI (naMCI) group demonstrated microstructural pathology in the frontal white matter, internal capsule, occipital white matter, and the posterior cingulate region. A binary logistic regression model showed that DTI of the left posterior cingulate was significant in identifying persons with aMCI to an accuracy of 85.1%. Receiver operating characteristics curve analysis yielded a sensitivity of 80% and specificity of 60.3% in distinguishing aMCI from naMCI and the normal comparison group.

CONCLUSION

DTI of the posterior cingulate region discriminates MCI from cognitively normal individuals with accuracy and has the potential to be used as a biomarker of MCI, in particular aMCI.

Proton magnetic resonance spectroscopy in dementias and mild cognitive impairment

With the anticipated increase in dementias due to the aging demographic of industrialized nations, biomarkers for neurodegenerative diseases are increasingly important as new therapies are being developed for clinical trials. Proton MR spectroscopy ((1)H MRS) appears poised to be a viable means of tracking brain metabolic changes due to neurodegenerative diseases and potentially as a biomarker for treatment effects in clinical therapeutic trials. This review highlights the body of literature investigating brain metabolic abnormalities in Alzheimer's disease, amnestic mild cognitive impairment, frontotemporal dementia, vascular dementia, Lewy body dementia, and Parkinson's disease dementia. In particular, the review addresses the viability of (1)H MRS to discriminate among dementias, to measure disease progression, and to measure the effects of pharmacological treatments. While findings to date are encouraging, more study is needed in longitudinal patterns of brain metabolic changes, correspondence with changes in clinical markers of disease progression, and sensitivity of (1)H MRS measures to treatment effects. Such developments will hopefully benefit the search for effective treatments of dementias in the twenty-first century.

Longitudinal metabolic and cognitive changes in mild cognitive impairment patients

Advancements in clinical therapies have identified the need for biomarkers of early Alzheimer disease that distinguish the earliest stages of pathology and target those patients who are likely to gain the most benefit. The aim of this study was to characterize the longitudinal metabolic changes measured by 1H magnetic resonance spectroscopy in correlation to neuropsychologic indices of episodic memory, attention and mental processing speed, language facility, and executive function in subjects with mild cognitive impairment (MCI). Quantitative 1H magnetic resonance spectroscopy of the posterior cingulate gyrus was performed and repeated at 11.56+/-4.3 months. N-acetyl aspartate (NAA), total choline (Cho), total creatine (Cr), myo-inositol (mI), and glutamate/glutamine (Glx) metabolite levels were measured, corrected for cerebrospinal fluid dilution, and ratios calculated in MCI and cognitively normal subjects. In the first study, MCI subjects showed lower NAA levels, NAA/Cho, and NAA/mI ratios and increased Cho/Cr and mI/Cr compared with controls. In the follow-up study, 36% of the MCI subjects [atypical MCI (atMCI)] showed interval increases in NAA, Cr, and Glx levels compared with 64% of MCI subjects (typical MCI) who showed an interval decrease in NAA, Cr, and Glx. Both MCI subgroups had higher Clinical Dementia Rating scores and lower scores on episodic memory, phonemic, and semantic word fluency tasks, compared with controls. The annualized rate of change in metabolic and cognitive status did not differ between normal aging and MCI subjects. atMCI subjects showed significant negative correlations between metabolite levels and executive function task scores, with NAA/mI showing a significant positive correlation with phonemic and semantic word fluency. There were no significant correlations between metabolite levels and cognitive performance in tMCI subjects; however, NAA/mI and mI/Cr were negatively correlated with executive function tasks. These results indicate 2 distinct evolving metabolite profiles that correlate with changes in executive function and can be used to differentiate MCI from normal aging.

Magnetic resonance spectroscopy performance for detection of dementia, Alzheimer's disease and mild cognitive impairment in a community-based survey

BACKGROUND/AIMS

To evaluate (1)H-labelled magnetic resonance spectroscopy (MRS) in patients with a low Mini Mental State Examination (MMSE) score identified during a dementia community-based survey.

METHODS

A population sample of 1,500 individuals (>64 years old) was randomly selected. Two hundred and fifteen individuals (MMSE < or =24) were sorted into clinical groups: dementia, Alzheimer's disease, mild cognitive impairment (MCI), normal. Up to 56 of these individuals attended the MRS appointment. Two single-voxel sequences (TR 1,500, TE 35/144 ms) were carried out in the posterior cingulate gyrus of each individual, and the ratios N-acetylaspartate (NAA)/creatine (Cr), choline (Cho)/Cr, myo-inositol (mI)/Cr, NAA/mI and NAA/Cho were compared statistically. The ability of MRS to distinguish clinical groups was assessed by receiver-operating characteristics analysis. Cognition effects on metabolite ratios were estimated, with gender and cognition as categorical variables and age as a continuous covariate.

RESULTS

NAA/Cr and NAA/Cho ratios were lower in dementia or Alzheimer's disease than in MCI and normal groups. The NAA/Cr ratio at TE 35 ms performed best when distinguishing dementia or Alzheimer's disease from non-demented subjects (cut-off point 1.40). MRS could not distinguish between MCI patients and normal subjects. Dementia was an independent predictor of metabolite values.

CONCLUSION

In a population sample, conventional MRS still proved to be a useful tool for dementia discrimination, but it is potentially far less useful as a surrogate marker for MCI.

Utility of different MR modalities in mild cognitive impairment and its use as a predictor of conversion to probable dementia

RATIONALE AND OBJECTIVES

Mild cognitive impairment has been regarded as a pre-Alzheimer condition, but some patients do not develop dementia. The authors' objective was to determine whether findings from a combined use of H1 magnetic resonance spectroscopy (MRS), perfusion imaging (PI), and diffusion-weighted imaging (DWI) would predict conversion from amnesic mild cognitive impairment to dementia and to compare the diagnostic accuracy in discriminating patients with probable Alzheimer disease (AD), mixed dementia (MD), Lewy body dementia (LBD), pre-Alzheimer disease mild cognitive impairment (MCI), vascular MCI (VaMCI), and anxious or depression patients with cognitive impairment (DeMCI).

MATERIALS AND METHODS

A longitudinal cohort of 119 consecutive and incident subjects (73 women, 46 men; age 70+/-9.5 years) who fulfilled the criteria of amnesic MCI was followed for a mean period of 29 months. At baseline, a neuropsychological examination and standard blood test were performed, and different areas were examined by proton MRS, PI, and DWI. Among the group of patients considered to have AD, we also included patients with MD because these patients have a neurodegenerative component.

RESULTS

After the follow-up period, 54 patients were considered as converted to dementia (49 with AD; 5 with LBD), 28 patients as MCI, 22 patients as DeMCI, and 15 patients as VaMCI. We found that N-acetylaspartate (NAA)/creatine (Cr) ratios in posterior cingulated gyri (PCG) predict the conversion to probable AD with a sensitivity of 82% and specificity of 72%, and NAA/Cr ratios in the left occipital cortex (LOC) had a sensitivity of 78% and specificity of 69%. When we used spectroscopy in the PCG and LOC to differentiate the types of MCI and dementias, we found significance differences in NAA/Cr, NAA/myoinositol (mI), NAA/choline (Cho), mI/NAA, and Cho/Cr ratios. The apparent diffusion coefficient (ADC) values in the right hippocampus showed differences in patients with LBD and DeMCI (P=.003), LBD with MCI (P=0.48), and LBD and VaMCI (P=.009).

CONCLUSIONS

NAA/Cr ratios in PCG and LOC can predict the conversion from MCI to dementia with high sensitivity and specificity. MRS can differentiate AD from MCI, but cannot differentiate the types of MCI. DWI in the right hippocampus presents higher values of ADC in LBD and allows differentiating it from MCI.

Proteome-based identification of plasma proteins associated with hippocampal metabolism in early Alzheimer's disease

BACKGROUND AND METHODS

There is an urgent need for peripheral surrogates of Alzheimer's disease (AD) that accurately reflect disease state and severity as well as correlate with key features of its neuropathology. The aim of this study was to identify plasma proteins associated with known in vivo markers of disease activity. In an earlier proteomic study of plasma, we discovered a panel of 15 proteins that were differentially expressed in AD and further validated complement factor-H (CFH) and alpha-2-macroglobulin (A2M) as AD-specific plasma biomarkers. In the present study, we extended these findings by testing the associations of these plasma proteins with neuro-imaging measures of disease progression in AD. We combined (1)H-magnetic resonance spectroscopy of the hippocampus and MRI-based hippocampal volumetry with proteomic analysis of plasma in early AD and mild cognitive impairment (MCI) to achieve this goal. Using (1)H-magnetic resonance spectroscopy, we derived estimates of the hippocampal metabolite ratio N-acetylaspartate/myo-inositol (NAA/mI), a biochemical measure that is associated with cognitive decline in early AD. We also undertook a proteomic analysis of plasma in these individuals using two-dimensional gel electrophoresis (2DGE).

RESULTS

We observed that two plasma proteins previously shown to be differentially expressed in AD, complement factor-H (CFH) and alpha-2-macroglobulin (A2M) showed significant positive correlations with hippocampal NAA/mI ratio in AD.

CONCLUSIONS

The association of plasma CFH and A2M with hippocampal NAA/mI in this cohort of AD subjects suggests that these proteins may reflect disease progression in early AD. These findings warrant validation in large population-based datasets.

Lafora disease: spectroscopy study correlated with neuropsychological findings

PURPOSE

To evaluate the metabolic changes both in grey and white matter in Lafora disease using proton magnetic resonance spectroscopy and to determine the possible correlation with the pattern of cognitive impairment.

METHODS

Five patients with Lafora disease and six healthy controls were included in the study. Patients underwent at the same time-point neuropsychological testing and 1[H]MRS, using PRESS sequences (TE=136 and 25 ms) positioned in the frontal and posterior cingulate gyrus cortexes and in the adjacent frontal and parietal white matter.

RESULTS

Neuropsychological testing showed in all patients a prevalent involvement of performance abilities--with partial sparing of verbal competences--and of executive functions, suggesting a major involvement of frontal areas. Analysis of 1[H]MRS showed a statistically significant reduction in NAA/mI and NAA/Cr in grey matter of patients compared to controls, more significant in frontal regions. In white matter, a significant reduction of NAA/mI ratio was observed both in the frontal and parietal regions, associated with a reduction of the NAA/Cr only in the frontal white matter. NAA/mI was found to be the most statistically significant altered parameter in all regions studied and the only significantly altered ratio in strong correlation with all sets of neuropsychological parameters.

CONCLUSIONS

Our study confirmed the predominant metabolic damage in the frontal cortex, also demonstrating NAA/mI ratio to be the most sensitive parameter to detect metabolic brain changes in Lafora disease; moreover, it evidenced frontal white matter spectroscopic changes. Both spectroscopy values and clinical features of cognitive impairment showed a prevalent frontal impairment.

Alzheimer's disease beyond the genomic era: nuclear magnetic resonance (NMR) spectroscopy-based metabolomics

Alzheimer's disease (AD) is a complex disease, with no definitive biomarkers available that allow clinical diagnosis; this represents a major problem for the advance of efficient drug discovery programs. A successful approach towards the understanding and treatment of AD should take into consideration this complex nature. In this sense, metabolic networks are subject to severe stoichiometric restrictions. Metabolomics amplifies changes both in the proteome and the genome, and represents a more accurate approximation to the phenotype of an organism in health and disease. In this article, we will examine the current rationale for metabolomics in AD, its basic methodology and the available data in animal models and human studies. The discussed topics will highlight the importance of being able to use the metabolomic information in order to understand disease mechanisms from a systems biology perspective as a non-invasive approach to diagnose and grade AD. This could allow the assessment of new therapies during clinical trials, the identification of patients at risk to develop adverse effects during treatment and the final implementation of new tools towards a more personalized medicine.

1H magnetic resonance spectroscopy in dementia

Present data support the concept that (1)H magnetic resonance spectroscopy ((1)H MRS) may become an adjunct to clinical evaluation for differential diagnosis of dementia in the future. The value of (1)H MRS in monitoring the disease progression in dementia is expected to be in areas where group effects are sought such as monitoring effectiveness of therapies in drug trials. Elevation of myoinositol to creatine (mI/Cr) and choline to creatine (Cho/Cr) and reduction in the neuronal integrity marker N-acetylaspartate to creatine (NAA/Cr) levels in individuals with mild cognitive impairment and pre-symptomatic Alzheimer's disease suggests that (1)H MRS may also be valuable in predicting future development of dementia and monitoring early disease progression for preventive therapies. Investigations of in vivo (1)H MRS as a marker for differential diagnosis and progression of dementia, however, has been limited to clinically confirmed cohorts and remains to be validated by histopathology at autopsy. Overall, MRS is a promising investigational technique in ageing and dementia at this time. The potential clinical application of MRS in ageing and dementia, however, is growing with technical advances in the field.

Anterior thalamic lesions produce chronic and profuse transcriptional de-regulation in retrosplenial cortex: A model of retrosplenial hypoactivity and covert pathology

Anterior thalamic lesions are thought to produce 'covert pathology' in retrosplenial cortex, but the causes are unknown. Microarray analyses tested the hypothesis that thalamic damage causes a chronic, hypo-function of metabolic and plasticity-related pathways (Experiment 1). Rats with unilateral, anterior thalamic lesions were exposed to a novel environment for 20 minutes, and granular retrosplenial tissue sampled from both hemispheres 30 minutes, 2h, or 8h later. Complementary statistical approaches (analyses of variance, predictive patterning and gene set enrichment analysis) revealed pervasive gene expression differences between retrosplenial cortex ipsilateral to the thalamic lesion and contralateral to the lesion. Selected gene differences were validated by QPCR, immunohistochemistry (Experiment 1), and in situ hybridisation (Experiment 2). Following thalamic lesions, the retrosplenial cortex undergoes profuse cellular transcriptome changes including lower relative levels of specific mRNAs involved in energy metabolism and neuronal plasticity. These changes in functional gene expression may be largely driven by decreases in the expression of multiple transcription factors, including brd8, c-fos, fra-2, klf5, nfix, nr4a1, smad3, smarcc2, and zfp9, with a much smaller number (nfat5, neuroD1, RXRγ) showing increases. These findings have implications for conditions such as diencephalic amnesia and Alzheimer's disease, where both anterior thalamic pathology and retrosplenial cortex hypometabolism are prominent.

Proton Magnetic Resonance Spectroscopy of the Hippocampus in Patients With Mild Cognitive Impairment

OBJECTIVE

To assess the brain metabolites in the hippocampus of patients with mild cognitive impairment (MCI) using proton magnetic resonance spectroscopy at 0.5 T.

METHODS

Absolute concentrations and ratios to creatine of N-acetyl aspartate, myoinositol, glutamate + glutamine, and choline were measured in the right and left hippocampus of 5 MCI patients and 5 control subjects.

RESULTS

In MCI subjects, reduced N-acetyl aspartate was found in the right hippocampus (P = 0.01), and increased myoinositol was found in the left hippocampus (P = 0.02). Myoinositol/N-acetyl aspartate ratios were higher in the right (P = 0.03) and left (P = 0.01) hippocampus of MCI subjects. No significant difference in the concentration of glutamate + glutamine was observed between the control and MCI groups.

CONCLUSIONS

An increase in myoinositol and a decrease in N-acetyl aspartate may be observed in the preclinical stages of dementia. Ratio measurements of these metabolites may serve as a biomarker for MCI.

[Cognitive impairment: classification by proton magnetic resonance spectroscopy and the contributions of conventional magnetic resonance imaging]

OBJECTIVE

To analyze the diagnostic accuracy of proton magnetic resonance spectroscopy (1H MRS) in patients with cognitive impairment and to establish the usefulness of complementary information provided by conventional magnetic resonance imaging (MRI).

MATERIAL AND METHODS

64 patients with cognitive impairment, including Alzheimer's disease (AD) (n=31), vascular dementia (n=6), mild cognitive impairment (MCI) (n=9), and major depression (n=18), were studied. All patients underwent cerebral MRI and single-volume 1H MRS using two echo times (TE, 31 and 136 ms) in the posterior cingulate gyrus and right temporal lobe. The metabolites analyzed were N-acetylaspartate (NAA), myo-Inositol (mI), choline (Ch), and creatine (Cr), and the ratios of Ch/Cr, mI/Cr, NAA/mI and NAA/Cr were calculated. In order to differentiate among the different types of cognitive impairment, the alterations in imaging and spectroscopy findings were graded from 0 to 4, as was the mean combination of the two, and then ROC curves were obtained.

RESULTS

Statistically significant differences were found between the spectra of patients with dementia (AD and vascular dementia) and those without dementia (MCI and depression) in the posterior cingulate gyrus. The NAA/mI ratio yielded the best area under the ROC curve, with the best sensitivity (82.5%) and specificity (72.7%) in the diagnosis of AD. The NAA/mI and mI/Cr quotients differentiated between the four degenerative pathologies causing the cognitive impairment. The combination of MRI and 1H MRS significantly improved the accuracy of the diagnosis of AD.

CONCLUSIONS

The metabolic differences found among patients with cognitive impairment using 1H MRS can be useful for differentiating AD, vascular dementia, MCI, and depression. The combination of spectroscopy and MRI findings is useful in the diagnosis of AD.

Effects of Alzheimer disease on fronto-parietal brain N-acetyl aspartate and myo-inositol using magnetic resonance spectroscopic imaging

Previous magnetic resonance (MR) spectroscopy studies of Alzheimer disease (AD) reporting reduced N-acetyl aspartate (NAA) and increased myo-Inositol (mI) used single voxel techniques, which have limited ability to assess the regional distribution of the metabolite abnormalities. The objective of this study was to determine the regional distribution of NAA and mI alterations in AD by using MR spectroscopic imaging. Fourteen patients with AD and 22 cognitively normal elderly were studied using structural MR imaging and MR spectroscopic imaging. Changes of NAA, mI, and various metabolite ratios were measured in frontal and parietal lobe gray matter (GM) and white matter. This study found: (1) when compared with cognitively normal subjects, AD patients had increased mI and mI/creatine (Cr) ratios primarily in parietal lobe GM, whereas frontal lobe GM and white matter were spared; (2) in the same region where mI was increased, AD patients had also decreased NAA and NAA/Cr ratios, replicating previous findings; (3) however, increased mI or mI/Cr ratios did not correlate with decreased NAA or NAA/Cr ratios; and (4) using mI/Cr and NAA/Cr together improved sensitivity and specificity to AD from control as compared with NAA/Cr alone. In conclusion, decreased NAA and increased mI in AD are primarily localized in parietal lobe GM regions. However, the NAA and mI changes are not correlated with each other, suggesting that they represent different processes that might help staging of AD.

Conversion of MCI to dementia: Role of proton magnetic resonance spectroscopy

Mild cognitive impairment (MCI) represents a heterogeneous group of cognitive disturbances at high risk of dementia. The amnestic subtype (aMCI) might be a prodromal state of Alzheimer's disease (AD). The aim of this study is the identification, by proton magnetic resonance spectroscopy (1H MRS), of modifications in brain metabolites able to detect subjects with aMCI at risk of conversion towards AD. Twenty-five subjects with aMCI and 29 normal elderly were enrolled; they underwent a comprehensive clinical and instrumental assessment, a cerebral 1H MRS scan to measure N-acetyl aspartate (NAA), choline (Cho), myo-inositol (mI) and creatine (Cr) in the paratrigonal white matter, bilaterally. After 1 year, 5 MCI subjects became demented (progressive MCI, pMCI). Their baseline levels of metabolites were compared with those evaluated in stable MCI (sMCI) and in controls. We observed a significant difference of the NAA/Cr ratio between pMCI (1.48+/-0.08) and sMCI (1.65+/-0.12) and between pMCI and controls (1.63+/-0.16) in the left hemisphere, suggesting that this metabolic alteration can be detected before the clinical appearance of dementia.

Metabolic alteration transients during paroxysmal activity in an epileptic patient with fixation-off sensitivity: a case study

The purpose of this study was to investigate short-time metabolic variations related to continuous epileptic activity elicited by fixation-off sensitivity (FOS). Time-resolved magnetic resonance spectroscopy was performed on a patient on whom previous clinical findings clearly indicated presence of FOS. The epileptic focus was localized with a simultaneous electroencephalographic and functional magnetic resonance imaging study. The results showed a linear increase of the sum of glutamate and glutamine with time of paroxysmal activity in epileptic focus and much greater concentration of choline-containing compounds in focus than in the contralateral side.

1H MR spectroscopy using TE averaged PRESS: A more sensitive technique to detect neurodegeneration associated with Alzheimer's disease

A sensitive proton magnetic resonance spectroscopy ((1)H MRS) acquisition scheme that is capable of discriminating between normal controls and a group of patients with early Alzheimer's disease (AD) is presented. The performance of this newly developed method, TE averaged PRESS (PRESS-J), in detecting neurodegeneration associated with early AD is compared with that of short echo time (TE) PRESS. A stepwise discriminant function analysis is used to construct discriminant functions for both pulse sequences. These functions are each composed of a single predictor: the N-acetyl aspartate (NAA)/creatine (Cr) ratio for PRESS-J, and the NAA/myoInositol (mI) ratio for PRESS. We observed lower P-values, higher areas under the receiver operating characteristic curves, and higher sensitivity at a given specificity for the PRESS-J discriminating function in comparison with the PRESS discriminating function. The higher sensitivity of PRESS-J is due to decreased variability when the singlets are fit in the spectra. This increased sensitivity enables new MR applications and, among other benefits, allows for smaller group sizes in drug trials, which can significantly reduce the cost of such trials.