Hippocampal and entorhinal cortex atrophy in frontotemporal dementia and Alzheimer's disease

Patterns of cortical thinning in Alzheimer's disease and frontotemporal dementia

In vivo measurement of cortical thickness is a sensitive representation of pathology in neurodegenerative disorders which primarily target the gray mantle. In this study we used magnetic resonance images to describe the patterns of cortical thinning in 11 frontotemporal dementia (FTD), 38 Alzheimer's disease (AD) and 34 healthy elderly (H(E)) subjects. AD and FTD displayed significant thinning of the cortical mantle compared to the H(E) group, but with distinctive distributions. AD subjects had significantly thinner cortex in all lobes whereas FTD compared to H(E) showed significant differences only in specific regions of frontal and temporal lobes. When compared to AD, the FTD subjects had a trend of thinner cortex in the anterior cingulate region and in selective regions of anterior frontal and temporal regions. In conclusion, the cortical thinning in dementia when compared to H(E), is disease specific whereby FTD subjects display a pattern distinct than that seen in Alzheimer's disease.

Neuropsychological deficits in frontotemporal dementia and Alzheimer's disease: a meta-analytic review

We sought to identify the cognitive tests that best discriminate between Alzheimer's disease (AD) and frontotemporal dementia (FTD). A comprehensive search of all studies examining the cognitive performance of persons diagnosed with AD and FTD, published between 1980 and 2006, was conducted. Ninety-four studies were identified, comprising 2936 AD participants and 1748 FTD participants. Weighted Cohen's d effect sizes, percentage overlap statistics, confidence intervals and fail-safe Ns were calculated for each cognitive test that was used by two or more studies. The most discriminating cognitive tests were measures of orientation, memory, language, visuomotor function and general cognitive ability. Although there were large and significant differences between groups on these measures, there was substantial overlap in the scores of the AD and FTD groups. Age, education, years since diagnosis and diagnostic criteria did not significantly contribute to the group differences. Given the large overlap in the test performance of persons diagnosed with AD and FTD, cognitive tests should be used cautiously and in conjunction with a medical history, behavioural observations, imaging and information from relatives when making differential diagnoses.

Deformation-based morphometry reveals brain atrophy in frontotemporal dementia

OBJECTIVE

To compare deformation-based maps of local anatomical size between subjects with frontotemporal dementia (FTD) and healthy subjects to identify regions of the brain involved in FTD.

DESIGN

Structural magnetic resonance images were obtained from 22 subjects with FTD and 22 cognitively normal, age-matched controls. We applied deformation-based morphometry and compared anatomy between groups using an analysis of covariance model that included a categorical variable denoting group membership and covaried for head size.

SETTING

University of California, San Francisco, Memory and Aging Center, and the San Francisco Veterans Affairs Medical Center.

PATIENTS

Twenty-two subjects with FTD and 22 cognitively normal, age-matched controls.

INTERVENTIONS

Neurological, neuropsychological, and functional evaluations and magnetic resonance imaging.

MAIN OUTCOME MEASURE

Deformation maps of local anatomical size.

RESULTS

Patients with FTD showed extensive, significant atrophy of the frontal lobes, affecting both gray matter and white matter. Atrophy of similar magnitude but less significance was observed in the anterior temporal lobes. The subcortical and midbrain regions, particularly the thalamus, pons, and superior and inferior colliculi, showed strongly significant atrophy of smaller magnitude.

CONCLUSIONS

We confirmed frontal and anterior temporal gray matter atrophy in FTD. The observed white matter loss, thalamic involvement, and midbrain atrophy are consistent with pathological findings in late-stage FTD. Dysfunction of ventral-frontal-brainstem circuitry may underlie some of the unique clinical features of FTD.

Structural magnetic resonance imaging-derived biomarkers for Alzheimer’s disease

The development and validation of biomarkers for prediction, diagnosis and tracking of progression of Alzheimer’s disease are both increasingly important. As potential pharmaceutical agents are developed for Alzheimer’s disease, their efficacy needs to be assessed. When medications become available, those subjects who may derive most benefit from such treatments need to be selected and their response to treatment monitored. As such, there has been much research into biomarkers in recent years, with many showing promise in all areas of biomarker utility. This review focuses on the potential of structural imaging as a biomarker in Alzheimer’s disease.

Human experience seeking correlates with hippocampus volume: convergent evidence from manual tracing and voxel-based morphometry

Experience seekers continuously pursue novel environmental stimuli, a tendency linked to genetic variation in mesolimbic dopamine transmission. However, the neuroanatomical basis accompanying these genetic and neurochemical associations is unknown. Animal and human experimental results suggest a central role for the hippocampus in processing novel stimuli. Here, we explored whether differences in human experience seeking are related to variations in hippocampal volume. High-resolution anatomic MR images were analyzed in 40 individuals who ranged from low through high on a validated experience seeking personality scale. Manual tracing analysis demonstrated positive correlation between right hippocampal volumes and scores on the experience seeking scale. A separate voxel-based morphometric analysis confirmed these results and localized the significant increase to the anterior portion of right hippocampal grey matter. We tested and were able to reject the possibility that results were mediated by a personality trait related to, but distinct from, experience seeking. The present data provide the first direct evidence for a relationship between human experience seeking and brain structure. In addition, these results provide new ecologically relevant evidence for a link between right anterior hippocampus and novelty processing.

Imaging and CSF studies in the preclinical diagnosis of Alzheimer's disease

It is widely believed that the path to early and effective treatment for Alzheimer's disease (AD) requires the development of early diagnostic markers that are both sensitive and specific. To this aim, using longitudinal study designs, we and others have examined magnetic resonance imaging (MRI), 2-fluoro-2-deoxy-d-glucose-positron emission tomography (FDG/PET), and cerebrospinal fluid (CSF) biomarkers in cognitively normal elderly (NL) subjects and in patients with mild cognitive impairment (MCI). Such investigations have led to the often replicated findings that structural evidence of hippocampal atrophy as determined by MRI, as well as metabolic evidence from FDG-PET scan of hippocampal damage, predicts the conversion from MCI to AD. In this article we present a growing body of evidence of even earlier diagnosis. Brain pathology can be detected in NL subjects and used to predict future transition to MCI. This prediction is enabled by examinations revealing reduced glucose metabolism in the hippocampal formation (hippocampus and entorhinal cortex [EC]) as well as by the rate of medial temporal lobe atrophy as determined by MRI. However, neither regional atrophy nor glucose metabolism reductions are specific for AD. These measures provide secondary not primary evidence for AD. Consequently, we will also summarize recent efforts to improve the diagnostic specificity by combining imaging with CSF biomarkers and most recently by evaluating amyloid imaging using PET. We conclude that the combined use of conventional imaging, that is MRI or FDG-PET, with selected CSF biomarkers incrementally contributes to the early and specific diagnosis of AD. Moreover, selected combinations of imaging and CSF biomarkers measures are of importance in monitoring the course of AD and thus relevant to evaluating clinical trials.

Different regional patterns of cortical thinning in Alzheimer's disease and frontotemporal dementia

Alzheimer's disease and frontotemporal dementia (FTD) can be difficult to differentiate clinically because of overlapping symptoms. Distinguishing the two dementias based on volumetric measurements of brain atrophy with MRI has been only partially successful. Whether MRI measurements of cortical thinning improve the differentiation between Alzheimer's disease and FTD is unclear. In this study, we measured cortical thickness using a set of automated tools (Freesurfer) to reconstruct the brain's cortical surface from T1-weighted structural MRI data in 22 patients with Alzheimer's disease, 19 patients with FTD and 23 cognitively normal subjects. The goals were to detect the characteristic patterns of cortical thinning in these two types of dementia, to test the relationship between cortical thickness and cognitive impairment, to determine if measurement of cortical thickness is better than that of cortical volume for differentiating between these dementias and normal ageing and improving the classification of Alzheimer's disease and FTD based on neuropsychological scores alone. Compared to cognitively normal subjects, Alzheimer's disease patients had a thinner cortex primarily in bilateral, frontal, parietal, temporal and occipital lobes (P < 0.001), while FTD patients had a thinner cortex in bilateral, frontal and temporal regions and some thinning in inferior parietal regions and the posterior cingulate (P < 0.001). Compared to FTD patients, Alzheimer's disease patients had a thinner cortex (P < 0.001) in parts of bilateral parietal and precuneus regions. Cognitive impairment was negatively correlated with cortical thickness of frontal, parietal and temporal lobes in Alzheimer's disease, while similar correlations were not significant in FTD. Measurement of cortical thickness was similar to that of cortical volume in differentiating between normal ageing, Alzheimer's disease and FTD. Furthermore, cortical thickness measurements significantly improved the classification between Alzheimer's disease and FTD based on neuropsychological scores alone, including the Mini-Mental State Examination and a modified version of the Trail-Making Test. In conclusion, the characteristic patterns of cortical thinning in Alzheimer's disease and FTD suggest that cortical thickness may be a useful surrogate marker for these types of dementia.

Tracking Alzheimer's disease

Population-based brain mapping provides great insight into the trajectory of aging and dementia, as well as brain changes that normally occur over the human life span. We describe three novel brain mapping techniques, cortical thickness mapping, tensor-based morphometry (TBM), and hippocampal surface modeling, which offer enormous power for measuring disease progression in drug trials, and shed light on the neuroscience of brain degeneration in Alzheimer's disease (AD) and mild cognitive impairment (MCI). We report the first time-lapse maps of cortical atrophy spreading dynamically in the living brain, based on averaging data from populations of subjects with Alzheimer's disease and normal subjects imaged longitudinally with MRI. These dynamic sequences show a rapidly advancing wave of cortical atrophy sweeping from limbic and temporal cortices into higher-order association and ultimately primary sensorimotor areas, in a pattern that correlates with cognitive decline. A complementary technique, TBM, reveals the 3D profile of atrophic rates, at each point in the brain. A third technique, hippocampal surface modeling, plots the profile of shape alterations across the hippocampal surface. The three techniques provide moderate to highly automated analyses of images, have been validated on hundreds of scans, and are sensitive to clinically relevant changes in individual patients and groups undergoing different drug treatments. We compare time-lapse maps of AD, MCI, and other dementias, correlate these changes with cognition, and relate them to similar time-lapse maps of childhood development, schizophrenia, and HIV-associated brain degeneration. Strengths and weaknesses of these different imaging measures for basic neuroscience and drug trials are discussed.

Atrophy rates of the cingulate gyrus and hippocampus in AD and FTLD

This study explores the diagnostic utility of atrophy rates of the cingulate gyrus, its subdivisions and the hippocampus in Alzheimer's disease (AD) and frontotemporal lobar degeneration (FTLD). Regions were manually outlined on MR images of a group of pathologically or genetically confirmed patients with AD (n=19), FTLD (n=8) and age-matched controls (n=11). Mean (S.D.) atrophy rates (%year(-1)) in the cingulate in controls, AD and FTLD were -0.3 (1.2), 5.9 (3.5), and 8.6 (4.1), respectively. Hippocampal atrophy rates in controls, AD and FTLD were -0.1 (0.8), 3.4 (2.2), and 5.2 (5.4), respectively. Atrophy rates were significantly higher in the cingulate and hippocampi in AD and FTLD compared with controls (p<0.01). There was evidence of a difference in trends of atrophy in the cingulate (more anterior in FTLD and more posterior in AD) between the disease groups (p=0.03). Cingulate atrophy rates discriminated perfectly between FTLD and controls. Significantly better discrimination between AD and controls was obtained by hippocampal rather than cingulate rates. In conclusion, cingulate atrophy is as significant a feature of AD and FTLD as hippocampal atrophy.

Hypoperfusion in frontotemporal dementia and Alzheimer disease by arterial spin labeling MRI

OBJECTIVES

To test if arterial spin labeling (ASL) MRI could detect a pattern of hypoperfusion in frontotemporal dementia (FTD) vs cognitively normal (CN) control subjects; to determine the regional difference of perfusion between FTD and Alzheimer disease (AD); and to determine whether hypoperfusion in FTD correlates with cognitive impairment.

METHODS

We included 21 patients with FTD, 24 patients with AD, and 25 CN subjects in this cross-sectional MRI study. All subjects had MRI scans including T1-weighted structural images and ASL-MR images.

RESULTS

ASL-MRI detected a pattern of hypoperfusion in right frontal regions in patients with FTD vs CN subjects, similar to PET and SPECT. FTD had higher perfusion than AD in the parietal regions and posterior cingulate. Frontal hypoperfusion in FTD correlated with deficits in judgment and problem solving. Adding frontal perfusion to gray matter (GM) atrophy significantly improved the classification of FTD from normal aging to 74%, and adding parietal perfusion to GM atrophy significantly improved the classification of FTD from AD to 75%. Combining frontal and parietal lobe perfusion further improved the classification of FTD from AD to 87%.

CONCLUSION

Frontotemporal dementia and Alzheimer disease display different spatial distributions of hypoperfusion on arterial spin labeling MRI. With further development and evaluation, arterial spin labeling MRI could contribute to the differential diagnosis between frontotemporal dementia and Alzheimer disease.

Gene expression profiles in anatomically and functionally distinct regions of the normal aged human brain

In this article, we have characterized and compared gene expression profiles from laser capture microdissected neurons in six functionally and anatomically distinct regions from clinically and histopathologically normal aged human brains. These regions, which are also known to be differentially vulnerable to the histopathological and metabolic features of Alzheimer's disease (AD), include the entorhinal cortex and hippocampus (limbic and paralimbic areas vulnerable to early neurofibrillary tangle pathology in AD), posterior cingulate cortex (a paralimbic area vulnerable to early metabolic abnormalities in AD), temporal and prefrontal cortex (unimodal and heteromodal sensory association areas vulnerable to early neuritic plaque pathology in AD), and primary visual cortex (a primary sensory area relatively spared in early AD). These neuronal profiles will provide valuable reference information for future studies of the brain, in normal aging, AD and other neurological and psychiatric disorders.

Topographical patterns of lobar atrophy in frontotemporal dementia and Alzheimer's disease

BACKGROUND/AIMS

Fronto-temporal dementia (FTD) designates a group of relatively common neurodegenerative disorders. The aim of this study was to characterize the patterns of brain atrophy in FTD compared to Alzheimer's disease (AD).

METHODS

A novel semiautomatic volumetric MRI analysis method was applied to measure regional brain volumes in FTD (n = 15; behavioural variant n = 9, language variant n = 6) in contrast with AD patients (n = 15) and age-matched controls (NC) (n = 15). FTD and AD patients were matched on demographic measures and Mini Mental State Examination scores.

RESULTS

Significant atrophy was present in the frontal and anterior temporal lobes of subjects with FTD compared to AD (p = 0.02; effect size = 1.11) and compared to NC (p < 0.001; effect size = 1.86). Severe atrophy of the left anterior temporal region distinguished the language variant. AD patients, by contrast, did not differ from NC for frontal lobe volume but had smaller anterior temporal lobes (p = 0.03). Both dementia groups had medial temporal lobe atrophy of similar magnitude. A logistic regression model including 4 regional measures correctly classified 100% of subjects.

CONCLUSION

FTD can be reliably differentiated from AD by virtue of a topographical pattern of atrophy involving the frontal lobes and anterior temporal regions. Medial temporal lobe volumes do not distinguish FTD from AD.

Enhanced magnetic auditory steady-state response in early Alzheimer's disease

OBJECTIVE

Previous studies have reported abnormalities in both spontaneous and evoked electromagnetic brain activity in Alzheimer's disease (AD). We studied the auditory steady-state response (SSR) which represents the net effect of entrained background activity and superimposed cortical evoked responses, in AD patients and healthy controls.

METHODS

Whole-head magnetoencephalography (MEG) was used to measure SSR to monaural 40-Hz stimulation in AD patients and age-matched controls. Equivalent current dipoles (ECD) of the SSR were modeled in each hemisphere, and source amplitudes were compared between the two groups using time-varying ECD models.

RESULTS

Our results indicate that the SSR is significantly increased in AD patients with mild to moderate cognitive deterioration in comparison with healthy elderly subjects.

CONCLUSIONS

Goal-directed functioning requires optimization of inhibitory and excitatory inputs in the cortex, allowing the adaptation of responsiveness to repetitive stimulation with low relevance. The present results suggest that this balance is impaired in AD, manifesting itself in decreased inhibition in cortical auditory processing and impaired adaptation of the stimulus-locked activity, probably due to abnormalities in cholinergic modulation.

SIGNIFICANCE

MEG appears to be a sensitive tool to detect abnormalities of auditory processing already in early stages of AD.

Alzheimer's disease

Alzheimer's disease is the most common cause of dementia. Research advances have enabled detailed understanding of the molecular pathogenesis of the hallmarks of the disease--ie, plaques, composed of amyloid beta (Abeta), and tangles, composed of hyperphosphorylated tau. However, as our knowledge increases so does our appreciation for the pathogenic complexity of the disorder. Familial Alzheimer's disease is a very rare autosomal dominant disease with early onset, caused by mutations in the amyloid precursor protein and presenilin genes, both linked to Abeta metabolism. By contrast with familial disease, sporadic Alzheimer's disease is very common with more than 15 million people affected worldwide. The cause of the sporadic form of the disease is unknown, probably because the disease is heterogeneous, caused by ageing in concert with a complex interaction of both genetic and environmental risk factors. This seminar reviews the key aspects of the disease, including epidemiology, genetics, pathogenesis, diagnosis, and treatment, as well as recent developments and controversies.

Magnetic resonance imaging of Alzheimer's disease

A modern challenge for neuroimaging techniques is to contribute to the early diagnosis of neurodegenerative diseases, such as Alzheimer's disease (AD). Early diagnosis includes recognition of pre-demented conditions, such as mild cognitive impairment (MCI) or having a high risk of developing AD. The role of neuroimaging therefore extends beyond its traditional role of excluding other conditions such as neurosurgical lesions. In addition, early diagnosis would allow early treatment using currently available therapies or new therapies in the future. Structural imaging can detect and follow the time course of subtle brain atrophy as a surrogate marker for pathological processes. New MR techniques and image analysis software can detect subtle brain microstructural, perfusion or metabolic changes that provide new tools to study the pathological processes and detect pre-demented conditions. This review focuses on markers of macro- and microstructural, perfusion, diffusion and metabolic MR imaging and spectroscopy in AD.

The role of quantitative structural imaging in the early diagnosis of Alzheimer's disease

The goal of this article is to review the role of structural neuroimaging in the diagnosis of Alzheimer's disease (AD). We present relevant neuroanatomy, highlight progress in the domain of AD imaging, and review the clinical characteristics of the prodromal phase of AD. We describe the history of the diagnostic issue by examining at cross-section and longitudinally the differences between patients who have AD and normal controls. We also present how subsequent works applied these characteristic traits to the early detection of the prodromal disease and to prediction of future decline. The article delineates the differences between subjects who have mild cognitive impairment and AD, which illustrate the spreading of the pathology with disease progression. The last section describes problems encountered in the differential diagnosis.

Neuropsychological differences between frontotemporal dementia and Alzheimer's disease: a review

This paper surveys the similarities and differences between frontotemporal dementia (FTD) and Alzheimer's disease (AD). The review covers findings primarily from neuropsychological studies on memory, language, attention/executive function, and visuospatial abilities. However, neuropsychiatric and neuroimaging data are also briefly discussed. Distinguishing features of both FTD and AD are described in order to present a comprehensive clinical picture of these dementing diseases, which is essential for the process of differential diagnosis. The cause of specific cognitive deficits is also considered. Our comprehensive review of the empirical literature reveals that AD is characterized by early memory loss and visuospatial problems, while among the main features of FTD are behavioral abnormalities and executive dysfunctions.

Hippocampal atrophy on MRI in frontotemporal lobar degeneration and Alzheimer's disease

BACKGROUND

Hippocampal atrophy on magnetic resonance imaging (MRI) is an early characteristic of Alzheimer's disease. However, hippocampal atrophy may also occur in other dementias, such as frontotemporal lobar degeneration (FTLD).

OBJECTIVE

To investigate hippocampal atrophy on MRI in FTLD and its three clinical subtypes, in comparison with Alzheimer's disease, using volumetry and a visual rating scale.

METHODS

42 patients with FTLD (17 frontotemporal dementia, 13 semantic dementia, and 12 progressive non-fluent aphasia), 103 patients with Alzheimer's disease, and 73 controls were included. Hippocampal volumetry and the easily applicable medial temporal lobe atrophy (MTA) rating scale were applied to assess hippocampal atrophy.

RESULTS

Multivariate analysis of variance for repeated measures showed an effect of diagnostic group on hippocampal volume. There was a significant diagnosis by side (left v right) interaction. Both FTLD and Alzheimer's disease showed hippocampal atrophy compared with controls. Results of the visual MTA rating scale confirmed these findings. Within the FTLD subtypes there were marked differences in hippocampal atrophy. Frontotemporal dementia and semantic dementia showed bilateral hippocampal atrophy, and in semantic dementia the left hippocampus was smaller than in Alzheimer's disease. No significant hippocampal atrophy was detected in non-fluent progressive aphasia.

CONCLUSIONS

Hippocampal atrophy is not only a characteristic of Alzheimer's disease but also occurs in FTLD. The three clinical subtypes of FTLD show different patterns of hippocampal atrophy.

Morphological characteristics and electrophysiological properties of CA1 pyramidal neurons in macaque monkeys

Little is known about the morphological characteristics and intrinsic electrophysiological properties of individual neurons in the nonhuman primate hippocampus. We have used intracellular recording and biocytin-labeling techniques in the in vitro hippocampal slice preparation to provide quantitative evaluation of the fundamental morphological and intrinsic electrophysiological characteristics of macaque monkey CA1 pyramidal neurons. These neurons have previously been studied in the rat in our laboratory. Monkey CA1 pyramidal neurons have an average soma volume of 3578 microm3, 4.71 basal dendrites with 53 terminal branches for a dendritic length of about 10,164 microm, 1.13 apical dendrites with 47 terminal branches for a dendritic length of about 10,678 microm. In comparison, rat CA1 pyramidal neurons have an average soma volume of 2066 microm3, 3.35 basal dendrites with 29 terminal branches for a dendritic length of about 4,586 microm, 1.43 apical dendrites with 62 terminal branches for a dendritic length of about 8,838 microm. The basic intrinsic electrophysiological properties of CA1 pyramidal cells are similar in monkeys and rats. Monkey CA1 pyramidal neurons have a resting membrane potential of about -62 mV (rat: -62 mV), an input resistance of 35 MOmega (rat: 34-49 MOmega), a rheobase of 0.17 nA (rat: 0.12-0.20 nA) and an action potential amplitude of 83 mV (rat: 71-89 mV). Although morphological differences such as the increased dendritic length may translate into differences in neural processing between primates and rodents, the functional significance of these morphological differences is not yet clear. Quantitative studies of the primate brain are critical in order to extrapolate information derived from rodent studies into better understanding of the normal and pathological function of the human hippocampus.

Comprehensive dissection of the medial temporal lobe in AD: measurement of hippocampus, amygdala, entorhinal, perirhinal and parahippocampal cortices using MRI

BACKGROUND

Early pathological involvement of specific medial temporal lobe areas is characteristic for Alzheimer's disease (AD).

OBJECTIVE

To determine the extent of regional medial temporal lobe atrophy, including hippocampus, amygdala, and entorhinal, perirhinal, and parahippocampal cortices in mild AD patients and healthy controls, and to compare diagnostic accuracy across volumetric markers.

METHODS

We studied 34 patients with clinically probable AD and 22 healthy elderly control subjects. Regional volumetric measures were obtained from volumetric T1-weighted MRI scans after accounting for global brain atrophy using affine transformation into standard space.

RESULTS

Volumes of medial temporal lobe structures were significantly smaller in AD patients than in controls with exception of the left entorhinal cortex. The degree of atrophy was comparable between all structures. Diagnostic accuracy (number of correctly allocated cases divided by number of all cases) was highest for the right parahippocampal cortex with 85%, but only slightly lower for the right hippocampus and right entorhinal cortex with 82% and 84%. Using a linear combination of markers, the unilateral volumes of the right hippocampus, parahippocampal cortex and perirhinal cortex yielded an accuracy of 93%.

CONCLUSION

Extent of atrophy is similar between the different regions of the medial temporal lobe in mild AD.Volume measurements of medial temporal lobe structures in addition to the hippocampus only yield improved diagnostic accuracy if a combination of these structures is used.

Comparisons between Alzheimer disease, frontotemporal lobar degeneration, and normal aging with brain mapping

Alzheimer disease (AD) and frontotemporal lobar degeneration (FTLD) are both common degenerative dementias in the under 65 age group. Although clinical criteria have been defined for both diseases, there is considerable overlap in clinical features, and hence, diagnosis still can be very difficult particularly in the early stages of the disease. As a result, there has been increasing interest in using magnetic resonance imaging to better characterize these diseases and to aid in diagnosis. Voxel-based morphometry (VBM) is an automated technique that assesses patterns of regional gray matter atrophy on magnetic resonance imaging between 2 groups of subjects. It is unbiased in that it looks throughout the whole brain and does not require any a priori assumptions concerning which structures to assess, giving it a significant advantage over traditional region of interest-based methods. Voxel-based morphometry has been widely used to assess patterns of regional atrophy in subjects with AD and FTLD. These studies have demonstrated specific patterns of regional loss in both diseases, compared the 2 diseases to look for differences that could be diagnostically useful, and have correlated regions of gray matter loss to cognitive and behavioral deficits in these subjects. This article will review the findings of these studies and discuss the role of VBM in these neurodegenerative diseases.

Distribution of brain atrophy in behavioral variant frontotemporal dementia

Marked brain atrophy occurs in frontotemporal dementia (FTD) yet substantial variation between cases is seen. Recently, a four-level staging scheme which reflects increasing disease duration, severity of dementia and degree of neurodegeneration was described. In the present study, the extent and magnitude of atrophy in behavioral variant FTD and its relationship to disease duration and pathological subtype was further evaluated by quantifying the volume of 30 anatomically-defined regions. A validated point count technique was applied to 17 patients with FTD (9 Pick's disease, 6 dementia lacking distinctive histology, 2 FTD with motor neuron disease) and 21 controls. Atrophy was seen in all brain regions except the inferior frontal cortex and area 37. As might be expected, increasing severity of atrophy occurred with increasing disease duration and stage however measurable atrophy was more widespread than indicated by the staging scheme. Furthermore, severity of atrophy was not related to pathological subtype. Frontal, limbic and temporal regions appeared to be severely affected early in the disease process with temporal lobe atrophy the best predictor of disease duration. White matter, more posterior regions and the subcortex were affected later in the disease. These findings demonstrate a pattern of selective vulnerability which progresses over time. Furthermore, they demonstrate that although patients with a similar clinical subtype may have differing underlying histopathology, the pattern, severity and progression of brain atrophy is the same. This suggests that the regional pattern of neurodegeneration, rather than the type of histopathology influences the clinical syndrome in FTD.

Small hippocampal size in cognitively normal subjects with coronary artery disease

OBJECTIVE

Hippocampal size reduction detected by three-dimensional structural magnetic resonance imaging (3D-MRI) represents an important hallmark of Alzheimer's disease (AD). Recently, epidemiological and neuropathological studies have associated coronary artery disease (CAD) and cardiovascular risk factors with AD. The present study aimed to assess whether small hippocampal size is also a feature of CAD.

METHODS

Hippocampal volumes were assessed in 20 men with CAD and 20 healthy matched control subjects by use of 3D-MRI. Subjects with a history of neurological or psychiatric disorder, or signs of cognitive impairment were rigorously excluded.

RESULTS

Compared with controls, subjects with CAD had significantly smaller (-14%) hippocampal volumes. Cardiovascular risk factors were not related to hippocampal volumes of CAD subjects.

CONCLUSIONS

Our results demonstrate small hippocampal size in CAD subjects without any cognitive impairment. Future studies should clarify whether the annual rate of hippocampal volume loss of persons with CAD is greater than that of healthy individuals and predicts later cognitive decline or dementia.

Glucose metabolism and serotonin receptors in the frontotemporal lobe degeneration

In patients with the frontal variant of frontotemporal lobar degeneration (fv-FTLD), behavioral abnormalities may vary from apathy with motor slowness (apathetic form) to disinhibition with agitation (disinhibited form). These clinical presentations may be related to specific regional cerebral dysfunction and to deficit in the serotoninergic system. We studied cerebral glucose uptake using (18)F-fluorodeoxyglucose and positron emission tomography in 18 patients fulfilling clinical criteria for fv-FTLD and showing, respectively, an apathetic or disinhibited behavioral syndrome. In eight of these patients, we also evaluated the 5-hydroxytryptamine-2A receptor cerebral receptor distribution with [(11)C]MDL and positron emission tomography. We found a reduction of frontal glucose metabolism in the whole group of fv-FTLD patients. Apathetic syndrome was associated with a prevalent dorsolateral and frontal medial hypometabolism, whereas the disinhibited syndrome demonstrated a selective hypometabolism in interconnected limbic structures (the cingulate cortex, hippocampus/amygdala, and accumbens nucleus). The in vivo measurements of [(11)C]MDL indicated a significant reduction of 5-hydroxytryptamine-2A receptors in orbitofrontal, frontal medial, and cingulate cortices. These (18)F-fluorodeoxyglucose positron emission tomography changes can be considered as specific functional markers of the different behavioral presentations in fv-FTLD. The serotoninergic system dysfunction provides a rationale for therapeutic trials with selective serotonin reuptake inhibitors.

Visual assessment of medial temporal atrophy on MR films in Alzheimer's disease: comparison with volumetry

BACKGROUND AND AIMS

To test the agreement of a visual rating scale of medial temporal lobe atrophy (MTA) with linear and volumetric assessments, and to test its accuracy in discriminating between Alzheimer's disease (AD) patients and controls.

METHODS

Participants were 28 patients with AD and 29 healthy controls. MTA was evaluated according to Scheltens' five-point scale. Its accuracy in distinguishing AD patients from controls was evaluated as a stand-alone measure and in association with linear [width of the temporal horn (WTH)] and volumetric [hippocampal volume (HV)] measures.

RESULTS

The agreement of this visual rating scale with the other MTA measures was statistically significant (vs WTH and vs HV, p for trend < 0.00005). The visual rating scale showed a good accuracy in distinguishing AD patients from controls [area under the curve (AUC) 0.89, 95% confidence interval (CI) 0.79-0.98]. Although the accuracy of the visual rating scale improved in association with linear WTH (AUC 0.91, 95% CI 0.82-0.99) and in association with HV (AUC 0.93, 95% CI 0.86-1.00), the improvement was not significant.

CONCLUSIONS

The visual rating scale of MTA, easily applicable in clinical practice, shows good agreement with more demanding quantitative methods, and can discriminate AD patients from controls with good accuracy.

MR-based in vivo hippocampal volumetrics: 2. Findings in neuropsychiatric disorders

Magnetic resonance imaging (MRI) has opened a new window to the brain. Measuring hippocampal volume with MRI has provided important information about several neuropsychiatric disorders. We reviewed the literature and selected all English-language, human subject, data-driven papers on hippocampal volumetry, yielding a database of 423 records. Smaller hippocampal volumes have been reported in epilepsy, Alzheimer's disease, dementia, mild cognitive impairment, the aged, traumatic brain injury, cardiac arrest, Parkinson's disease, Huntington's disease, Cushing's disease, herpes simplex encephalitis, Turner's syndrome, Down's syndrome, survivors of low birth weight, schizophrenia, major depression, posttraumatic stress disorder, chronic alcoholism, borderline personality disorder, obsessive-compulsive disorder, and antisocial personality disorder. Significantly larger hippocampal volumes have been correlated with autism and children with fragile X syndrome. Preservation of hippocampal volume has been reported in congenital hyperplasia, children with fetal alcohol syndrome, anorexia nervosa, attention-deficit and hyperactivity disorder, bipolar disorder, and panic disorder. Possible mechanisms of hippocampal volume loss in neuropsychiatric disorders are discussed.

Diagnosis of Alzheimer?s disease using brain perfusion SPECT and MR imaging: which modality achieves better diagnostic accuracy?

PURPOSE

The purpose of this study was to compare the accuracy of MR imaging and brain perfusion single-photon emission tomography (SPECT) in diagnosing Alzheimer's disease (AD).

METHODS

The transaxial section display of brain perfusion SPECT, three-dimensional stereotactic surface projection (3D-SSP) SPECT image sets, thin-section MR imaging of the hippocampus and perfusion MR imaging were evaluated in 66 subjects comprising 35 AD patients and 31 subjects without AD. SPECT and MR imaging were visually interpreted by two experts and two novices, and the diagnostic ability of each modality was evaluated by receiver operating characteristic (ROC) analysis.

RESULTS

In the experts' interpretations, there was no significant difference in the area under the ROC curve (Az) between 3D-SSP and thin-section MR imaging, whereas the Az of transaxial SPECT display was significantly lower than that of 3D-SSP (3D-SSP: 0.97, thin-section MR imaging: 0.96, transaxial SPECT: 0.91), and the Az of perfusion MR imaging was lowest (0.63). The sensitivity and specificity of each modality were, respectively, 80.0% and 96.8% for 3D-SSP, 77.1% and 96.8% for thin-section MR imaging, 60.0% and 93.5% for transaxial SPECT display and 34.3% and 100% for perfusion MR imaging. In the novices' interpretations, the Az, sensitivity and specificity of 3D-SSP were superior to those of thin-section MR imaging.

CONCLUSION

Thin-section hippocampal MR imaging and 3D-SSP image sets had potentially equivalent value for the diagnosis of AD, and they were superior to transaxial SPECT display and perfusion MR imaging. For avoidance of the effect of interpreters' experience on image evaluation, 3D-SSP appears to be optimal.

A comparison between the accuracy of voxel-based morphometry and hippocampal volumetry in Alzheimer's disease

PURPOSE

To compare the accuracy of voxel-based morphometry (VBM) and region of interest (ROI)-based hippocampal volumetry to detect medial temporal lobe atrophy in Alzheimer's disease (AD).

MATERIALS AND METHODS

A total of 27 AD patients (age 74 +/- 9 years; 22 women; Mini-Mental State Exam [MMSE] 21 +/- 4) and 25 controls (age 70 +/- 8; 16 women; MMSE 29 +/- 1) were studied. Accuracy of VBM to detect gray matter loss in those seven AD patients and 11 controls with similar ROI-based hippocampal measures and of ROI-based volumetry to detect gray matter loss in those four AD patients and five controls with similar VBM-based hippocampal measures was assessed. VBM was performed with statistical parametric mapping (SPM99).

RESULTS

The area under the curve was 0.96 (95% C.I., 0.92-1.00) for VBM, 0.89 (95% C.I., 0.80-0.98) for ROI-based hippocampal measures, and 0.99 (95% C.I., 0.96-1.00) for both. In subjects with similar ROI-based hippocampal measures, VBM detected atrophy in AD patients at P < 0.0001, while in subjects with similar VBM-based hippocampal measure, volumetry was not significant (P = 0.11). Both measures independently contributed to discrimination (P = 0.004 and P = 0.032) in a logistic regression model.

CONCLUSION

These results indicate that VBM is more accurate, but the combination of both methods provides the highest accuracy for detection of hippocampal atrophy in AD.

MRI and CSF studies in the early diagnosis of Alzheimer's disease

The main goal of our studies has been to use MRI, FDG-PET, and CSF biomarkers to identify in cognitively normal elderly (NL) subjects and in patients with mild cognitive impairment (MCI), the earliest clinically detectable evidence for brain changes due to Alzheimer's disease (AD). A second goal has been to describe the cross-sectional and longitudinal interrelationships amongst anatomical, CSF and cognition measures in these patient groups. It is now well known that MRI-determined hippocampal atrophy predicts the conversion from MCI to AD. In our summarized studies, we show that the conversion of NL subjects to MCI can also be predicted by reduced entorhinal cortex (EC) glucose metabolism, and by the rate of medial temporal lobe atrophy as determined by a semi-automated regional boundary shift analysis (BSA-R). However, whilst atrophy rates are predictive under research conditions, they are not specific for AD and cannot be used as primary evidence for AD. Consequently, we will also review our effort to improve the diagnostic specificity by evaluating the use of CSF biomarkers and to evaluate their performance in combination with neuroimaging. Neuropathology studies of normal ageing and MCI identify the hippocampal formation as an early locus of neuronal damage, tau protein pathology, elevated isoprostane levels, and deposition of amyloid beta 1-42 (Abeta42). Many CSF studies of MCI and AD report elevated T-tau levels (a marker of neuronal damage) and reduced Abeta42 levels (possibly due to increased plaque sequestration). However, CSF T-tau and Abeta42 level elevations may not be specific to AD. Elevated isoprostane levels are also reported in AD and MCI but these too are not specific for AD. Importantly, it has been recently observed that CSF levels of P-tau, tau hyperphosphorylated at threonine 231 (P-tau231) are uniquely elevated in AD and elevations found in MCI are useful in predicting the conversion to AD. In our current MCI studies, we are examining the hypothesis that elevations in P-tau231 are accurate and specific indicators of AD-related changes in brain and cognition. In cross-section and longitudinally, our results show that evaluations of the P-tau231 level are highly correlated with reductions in the MRI hippocampal volume and by using CSF and MRI measures together one improves the separation of NL and MCI. The data suggests that by combining MRI and CSF measures, an early (sensitive) and more specific diagnosis of AD is at hand. Numerous studies show that neither T-tau nor P-tauX (X refers to all hyper-phosphorylation site assays) levels are sensitive to the longitudinal progression of AD. The explanation for the failure to observe longitudinal changes is not known. One possibility is that brain-derived proteins are diluted in the CSF compartment. We recently used MRI to estimate ventricular CSF volume and demonstrated that an MRI-based adjustment for CSF volume dilution enables detection of a diagnostically useful longitudinal P-tau231 elevation. Curiously, our most recent data show that the CSF isoprostane level does show significant longitudinal elevations in MCI in the absence of dilution correction. In summary, we conclude that the combined use of MRI and CSF incrementally contributes to the early diagnosis of AD and to monitor the course of AD. The interim results also suggest that a panel of CSF biomarkers can provide measures both sensitive to longitudinal change as well as measures that lend specificity to the AD diagnosis.

Imaging in psychiatric illnesses

Brain imaging has given new insights into the structure and function of the brain in psychiatric illnesses. The conditions studied include Alzheimer's disease, Schizophrenia, depression and psychopathic disorders. Emerging technologies in the field of brain imaging have helped in the understanding of pathophysiology, aetiology, diagnosis, treatment response and prognosis of certain psychiatric disorders. This article summarizes the literature available and the potential clinical applications.

Semiautomatic brain region extraction: a method of parcellating brain regions from structural magnetic resonance images

Structural MR imaging has become essential to the evaluation of regional brain changes in both healthy aging and disease-related processes. Several methods have been developed to measure structure size and regional brain volumes, but many of these methods involve substantial manual tracing and/or landmark identification. We present a new technique, semiautomatic brain region extraction (SABRE), for the rapid and reliable parcellation of cortical and subcortical brain regions. We combine the SABRE parcellation with tissue compartment segmentation [NeuroImage 17 (2002) 1087] to produce measures of gray matter (GM), white matter (WM), ventricular CSF, and sulcal CSF for 26 brain regions. Because SABRE restricts user input to a few easily identified landmarks, inter-rater reliability is high for all volumes, with all coefficients between 0.91 and 0.99. To assess construct validity, we contrasted SABRE-derived volumetric data from healthy young and older adults. Results from the SABRE parcellation and tissue segmentation showed significant differences in multiple brain regions in keeping with regional atrophy described in the literature by researchers using lengthy manual tracing methods. Our findings show that SABRE is a reliable semiautomatic method for assessing regional tissue volumes that provides significant timesavings over purely manual methods, yet maintains information about individual cortical landmarks.

Hippocampus and entorhinal cortex in mild cognitive impairment and early AD

Magnetic resonance imaging (MRI) has been suggested as a useful tool in early diagnosis of Alzheimer's disease (AD). Based on MRI-derived volumes, we studied the hippocampus and entorhinal cortex (ERC) in 59 controls, 65 individuals with mild cognitive impairment (MCI) and 48 patients with AD. The controls and individuals with MCI were derived from population-based cohorts. Volumes of the hippocampus and ERC were significantly reduced in the following order: control > MCI > AD. Stepwise discriminant function analysis showed that the most efficient overall classification between controls and individuals with MCI subjects was achieved with ERC measurements (65.9%). However, the best overall classification between controls and AD patients (90.7%), and between individuals with MCI and AD patients (82.3%) was achieved with hippocampal volumes. Our results suggest that the ERC atrophy precedes hippocampal atrophy in AD. The ERC volume loss is dominant over the hippocampal volume loss in MCI, whereas more pronounced hippocampal volume loss appears in mild AD.

Age, education and test performance on the Finnish CERAD

OBJECTIVES

The purpose of this study was to clarify the effects of age and education on CERAD (Consortium to Establish a Registry for Alzheimer's Disease) test performances.

MATERIAL AND METHODS

We present preliminary data on CERAD test results for a sample of elderly normal Finns (n = 40, age 58-85 years).

RESULTS

Our results show no significant correlation between age and CERAD test results. Significant differences were found between subjects with low versus high education in nine CERAD test scores. The mean scores in the low-education group were near the cut-off point in the naming test, whereas the mean scores of the high-education group nearly reached the ceiling on six test scores. These differences were evident in the wordlist learning test, which has previously been argued to be unaffected by educational level. Savings scores were unaffected by education.

CONCLUSION

The results underline the importance of taking into account the educational level of persons with subjective memory complaints when screening with CERAD for mild cognitive impairment and preclinical Alzheimer's disease.

Hippocampal deformation-based shape analysis in epilepsy and unilateral mesial temporal sclerosis

PURPOSE

To assess shape changes in patients with mesial temporal sclerosis (MTS) and temporal lobe epilepsy (TLE), by using deformation-based hippocampal shape analysis.

METHODS

We retrospectively reviewed magnetic resonance imaging (MRI) studies in 30 subjects with unilateral MTS (15 right-sided MTS, 15 left-sided MTS) and TLE. We defined the "average" hippocampus in the right- and left-MTS groups by generating a mean transformation for the 15 deformation images in each group. Further to quantify the difference between the hippocampi, we coregistered the mean transformation of the involved hippocampus (with MTS) to the contralateral hippocampus, considering the left- and right-MTS groups independently. We generated a color "flame" scale showing degrees of outward and inward deviation of the coregistered hippocampi.

RESULTS

Both the right- and left-MTS groups showed similar shape changes, with maximal inward deformation in the medial and lateral hippocampal head and the hippocampal tail. However, more extensive involvement was seen in the lateral hippocampal body in the right-MTS group as compared with the left.

CONCLUSIONS

Deformation-based hippocampal shape analysis shows specific regions of hippocampal surface anatomy that are most affected in MTS. This technique may aid in detection of clinically significant anatomic abnormalities of the hippocampus in patients with epilepsy.

A critical discussion of the role of neuroimaging in mild cognitive impairment

OBJECTIVE

In this paper, the current neuroimaging literature is reviewed with regard to characteristic findings in mild cognitive impairment (MCI). Particular attention is drawn to the possible value of neuroimaging modalities in the prediction and early diagnosis of Alzheimer's disease (AD).

METHODS

First, the potential contribution of neuroimaging to an early, preclinical diagnosis of degenerative disorders is discussed at the background of our knowledge about the pathogenesis of AD. Second, relevant neuroimaging studies focusing on MCI are explored and summarized. Neuroimaging studies were found through Medline search and by systematically checking through the bibliographies of relevant articles.

RESULTS

Structural volumetric magnetic resonance imaging (MRI) and positron emission tomography (PET)/single photon emission tomography (SPECT) are currently the most commonly used neuroimaging modalities in studies focusing on MCI. There were considerable variations in demographical and clinical characteristics across studies. However, significant hippocampal and entorhinal cortex volume reductions were consistently found in subjects with MCI as compared with cognitively unimpaired controls. While hippocampal and entorhinal cortex atrophy in subjects with MCI are also well-established risk factors for the development of AD, these measures cannot be regarded as being of high predictive value in an individual case. Evidence for other typical neuroimaging changes in MCI is still scarce. In PET and SPECT studies, reduced blood flow and/or glucose metabolism in temporoparietal association areas, posterior cingulate and hippocampus were associated with a higher risk of progressive cognitive decline in MCI. In quantitative electroencephalogram (QEEG), low beta, high theta, low alpha and slowed mean frequency were associated with development of dementia.

CONCLUSIONS

Existing studies suggest that neuroimaging measures have the potential to become valuable tools in the early diagnosis of AD. To establish their value in routine use, larger studies, preferably with long prospective follow-up are needed.

Imaging end points for monitoring neuroprotection in Parkinson's disease

In this review, the potential role of positron emission tomography and single-photon emission computed tomography as biological markers for following the progression of Parkinson's disease (PD) is discussed, and their value for assessing the efficacy of putative neuroprotective agents in PD is considered. It is concluded that functional imaging provides a valuable adjunct to clinical assessment when judging the efficacy of neuroprotective approaches to PD.

A meta-analysis of structural and functional brain imaging in dementia of the Alzheimer's type: a neuroimaging profile

We conducted a quantitative review of the imaging literature using meta-analytic methodology to characterize further the magnitude of hippocampal deficit in probable Alzheimer's disease (AD) and to determine whether other neuroanatomic structures in AD can better discriminate the disease from normal aging. Additionally, we parceled the discriminability of neuroanatomic structures by duration of disease to determine those structures most sensitive to AD in its early and late stages. One hundred twenty-one studies published between 1984 and 2000 met criteria for inclusion in the present analysis. In total, structural (i.e., CT and MRI) and functional (i.e., SPECT and PET) neuroimaging results from 3511 patients with AD, and 1632 normal healthy controls were recorded across meta-analyses. Our results include neuroimaging profiles for both early onset and longer duration patients with AD. In sum, these profiles yield a signature of diagnostic markers in both cortical and subcortical neuroanatomic areas. This signature is consistent with the clinical phenomenology of Alzheimer's dementia and should aid in the positive identification of AD.

Early diagnosis of Alzheimer's disease: contribution of structural neuroimaging

To accurately predict the development of Alzheimer's disease (AD) at its predementia stage would be a major breakthrough from both therapeutic and research standpoints. In this review, our focus is on markers obtained with structural imaging--especially magnetic resonance imaging (MRI)--and on studies of subjects at risk of developing AD. Among the latter, amnestic mild cognitive impairment (MCI) is currently the most commonly accepted reference, and therefore is specially targeted in this review. MCI refers to patients with significant but isolated memory impairment relative to subjects of identical age. Consistent with established histopathological data, structural imaging studies comparing patients with early probable AD to healthy aged subjects have shown that the most specific and sensitive features of AD at this stage are hippocampal and entorhinal cortex atrophy, especially when combined with a reduced volume of the temporal neocortex. MCI patients have significant hippocampal atrophy when compared to aged normal controls. When comparing patients with probable AD to MCI subjects, hippocampal region atrophy significantly extends to the neighboring temporal association neocortex. However, only longitudinal studies of MCI subjects are suited to assess (in a retrospective way) the predictive value of initial atrophy measurements for progression to AD. Few such studies have been published so far and for the most they were based on small samples. Furthermore, the comparison among studies is clouded by differences in both populations studied and MRI methodology used. Nevertheless, comparing the initial MRI data of at-risk subjects who convert to AD at follow-up to those of nonconverters suggests that a reduced association temporal neocortex volume combined with hippocampal or anterior cingulate cortex atrophy may be the best predictor of progression to AD. These data, although still preliminary, are consistent with postmortem studies describing the hierarchical progression of tau lesions in normal aging and early stages of AD, such that damage to the medial temporal lobe and association cortex would account for the memory and nonmemory cognitive impairments, respectively, the combination of which is required to operationally define probable AD. Future research in this field should capitalize on thorough methodology for brain structure delineation, and combine atrophy measurements to cognitive and/or functional imaging data.

Computer-assisted imaging to assess brain structure in healthy and diseased brains

Neuroanatomical structures may be profoundly or subtly affected by the interplay of genetic and environmental factors, age, and disease. Such effects are particularly true in healthy ageing individuals and in those who have neurodegenerative diseases. The ability to use imaging to identify structural brain changes associated with different neurodegenerative disease states would be useful for diagnosis and treatment. However, early in the progression of such diseases, neuroanatomical changes may be too mild, diffuse, or topologically complex to be detected by simple visual inspection or manually traced measurements of regions of interest. Computerised methods are being developed that can capture the extraordinary morphological variability of the human brain. These methods use mathematical models sensitive to subtle changes in the size, position, shape, and tissue characteristics of brain structures affected by neurodegenerative diseases. Neuroanatomical features can be compared within and between groups of individuals, taking into account age, sex, genetic background, and disease state, to assess the structural basis of normality and disease. In this review, we describe the strengths and limitations of algorithms of existing computer-assisted tools at the most advanced stage of development, together with available and foreseeable evidence of their usefulness at the clinical and research level.

Amygdaloid atrophy in frontotemporal dementia and Alzheimer's disease

Crude and corrected amygdaloid volumes were computed from magnetic resonance scans in ten patients with frontotemporal dementia (FTD), 25 patients with Alzheimer's disease (AD) and 27 controls. Amygdaloid atrophy was present in FTD (P<0.005) compared to controls, and a trend for increasing atrophy from controls, through FTD to AD (P for trend <0.00005) showed that FTD amygdaloid volumes were intermediate between controls and AD. Behavioral and Klüver-Bucy-like symptoms, characteristic of FTD, cannot be explained by amygdaloid atrophy alone.

Olfactory identification and apolipoprotein E epsilon 4 allele in mild cognitive impairment

To investigate olfactory identification and apolipoprotein E epsilon 4 allele in patients with mild cognitive impairment (MCI), we used Cross-Cultural Smell Identification Test (CC-SIT) from University of Pennsylvania to assess olfactory identification performance and polymerase chain reaction (PCR) to detect apolipoprotein E epsilon 4 (ApoE epsilon 4) allele in 28 patients with MCI and the 30 age-matched control subjects in present study. The Mann-Whitney U test demonstrated that the MCI group performed significantly worse on CC-SIT than the normal aging group (P<0.01). For MCI patients olfaction scores correlated positively with CAMCOG-C (r=0.61, P<0.01), but not with age, gender or years of education. In normal subjects, the CC-SIT score showed no significant associations with age, gender, years of education, or CAMCOG-C. As the least common allele in Chinese, epsilon 4 was found in 13.3% of controls and in 35.8% of MCI in this study. ApoE epsilon 4 was significantly higher in MCI group than normal group (chi(2)=4.65, P<0.01). There was a significant effect of allele status on odor identification: subjects with epsilon 4 allele were not able to identify as many odors as the subjects without epsilon 4 allele (P<0.01). These results suggested that the decreased olfactory identification in MCI may be a marker for the early diagnosis of Alzheimer's disease, and ApoE genotype may be part of the basis of olfactory identification decline.

Dementing disorders: volumetric measurement of cerebrospinal fluid to distinguish normal from pathologic findings -- feasibility study

The authors describe a magnetic resonance (MR) imaging technique to quantify the severity and distribution of cerebral atrophy by using automated volumetric analysis of the distribution of cerebrospinal fluid. The MR imaging technique demonstrated high diagnostic sensitivity and specificity in a group of healthy subjects and patients with dementing diseases. The authors conclude that this approach provides valuable clinical information that is complementary to information acquired with standard diagnostic practices.

Effects of subcortical ischemic vascular dementia and AD on entorhinal cortex and hippocampus

OBJECTIVE

To determine the effects of subcortical ischemic vascular dementia (SIVD) and AD on entorhinal cortex (ERC) and hippocampus.

METHODS

Thirty-eight cognitively normal subjects, 18 patients with SIVD, and 22 patients with AD were included. Volumes of ERC and hippocampus were manually measured based on MRI. Global cerebral changes of cortical gray matter, subcortical gray matter, white matter, sulcal CSF, ventricular CSF (vCSF), and white matter signal hyperintensities (WMSH) were assessed.

RESULTS

Patients with SIVD had 21.7% (p < 0.01) smaller ERC and 18.2% (p < 0.01) smaller hippocampi than cognitively normal subjects and 24.4% (p < 0.01) larger ERC and 11.1% (p < 0.05) larger hippocampi than patients with AD. In addition, patients with SIVD had less cortical gray matter and white matter and more vCSF and WMSH (all p < 0.01) than cognitively normal subjects and more vCSF and WMSH (p < 0.01) than patients with AD. The volumes of ERC and hippocampus were positively correlated to similar extents (p < 0.01) in SIVD and AD. Cortical gray matter loss was positively correlated (p < 0.01) with hippocampal atrophy, but not with ERC atrophy, in SIVD and AD. Hippocampal volume alone could classify 82% of patients with SIVD from cognitively normal subjects and 63% of patients with SIVD from subjects with AD. Adding global cerebral changes to hippocampus substantially improved the classification to 96% between patients with SIVD and cognitively normal subjects and 83% between subjects with SIVD and those with AD, whereas adding ERC change to hippocampus did not significantly improve the discrimination.

CONCLUSIONS

The entorhinal cortex and hippocampus are less affected by subcortical ischemic vascular dementia than by AD.

Presenile dementia syndromes: an update on taxonomy and diagnosis

The four major degenerative dementias that often begin in presenescence: are reviewed. These are Alzheimer's disease, frontotemporal dementia, dementia with Lewy bodies, and Creutzfeldt-Jakob disease. Their epidemiological, genetic, and clinical features are reviewed, and controversies in taxonomy arising from recent discoveries described. Particular attention is given to the pathological role of protein aggregation, which appears to be a factor in each disease.

Diagnostic patterns of regional atrophy on MRI and regional cerebral blood flow change on SPECT in young onset patients with Alzheimer's disease, frontotemporal dementia and vascular dementia

OBJECTIVES

Alzheimer's disease (AD), frontotemporal dementia (FTD) and vascular dementia (VaD) are the three most common causes of young onset dementias. Most neuroimaging studies of these disorders have involved comparisons with normal controls. The aims of this study were to examine the clinical diagnostic value of magnetic resonance imaging (MRI) and single photon emission computed tomography (SPECT) (in combination and in isolation) in the differentiation of one form of dementia from another from amongst a group of AD, FTD and VaD.

METHODS

T1 weighted MRI images and 99mTc-HMPAO SPECT images were obtained from consecutive patients with FTD (n=21), AD (n=23) and VaD (n=20) and rated visually by experienced neuroradiologists and nuclear medicine physicians.

RESULTS

Asymmetrical atrophy was seen only in FTD. Frontotemporal dementia patients were the most atrophic whereas severe atrophy was rarely observed in VaD. Severe frontal atrophy (unilaterally or bilaterally) and/or asymmetrical atrophy on MRI is highly diagnostic (sensitivity 0.71, specificity 0.93, LR 10.24) of FTD from within a group of FTD and non-FTD (AD, VaD) patients. Mild or severe parietal atrophy with severe reduction in parietal regional cerebral blood flow on SPECT is diagnostic (sensitivity 0.71, specificity 0.76, LR 3.02) of AD from within a group of AD and non-AD (VaD, FTD) patients.

CONCLUSION

Anatomical (MRI) and functional (SPECT) imaging provide different information and a combination of these modalities improves diagnostic specificity.

Alzheimer's disease: its diagnosis and pathogenesis

A hypothesis has been presented that links many of the identified and putative risk factors for AD and suggests a mechanism for their action. Crawford (1996, 1998) proposes an association between AD and cerebral blood flow (CBF) by citing evidence that many of the factors that are linked with an increased risk of AD also decrease CBF (e.g., old age, depression, underactivity, head trauma). Similarly, it is suggested factors that increase CBF are associated with a decreased risk of AD (e.g., education, exercise, smoking, NSAIDs). Although the authors acknowledge that reduced CBF is not sufficient to cause AD, the reported positive and negative associations provide tantalizing evidence for a common mode of action for many of the equivocal risk factors reported to date. This hypothesis is also consistent with other data that links microvascular damage and impaired blood flow (de la Torre, 1997, 2000) and low education with increased cerebrovascular disease (Del Ser et al., 1999). Gaining a better understanding of the interaction between AD and vascular disease is of great importance. Not only will it provide insights into the pathogenesis of AD, but it may also provide us with a rare opportunity for the treatment and possible prevention of AD. A great many risk factors for vascular disease have been identified and intervention programs have successfully reduced the incidence of heart disease and stroke. The potential exists to provide the same level of success with AD.

Retrieval and encoding of episodic memory in normal aging and patients with mild cognitive impairment

We investigated retrieval and encoding of episodic memory in normal aging and patients with mild cognitive impairment (MCI). There was significant decline in the function of orientation, language and praxis besides memory impairment in the MCI group. Impairment of encoding and retrieval of episodic memory was observed in the MCI group. Encoding of episodic memory is vulnerable to be impaired in the MCI group.