Amyloid imaging in the differential diagnosis of dementia: Review and potential clinical applications

Memory and Aging Center, Department of Neurology, University of California San Francisco, 350 Parnassus Avenue, Suite 905, San Francisco, CA 94143, USA. .
Alzheimer's Research and Therapy (Impact Factor: 3.98). 11/2011; 3(6):31. DOI: 10.1186/alzrt93
Source: PubMed


In the past decade, positron emission tomography (PET) with carbon-11-labeled Pittsburgh Compound B (PIB) has revolutionized the neuroimaging of aging and dementia by enabling in vivo detection of amyloid plaques, a core pathologic feature of Alzheimer's disease (AD). Studies suggest that PIB-PET is sensitive for AD pathology, can distinguish AD from non-AD dementia (for example, frontotemporal lobar degeneration), and can help determine whether mild cognitive impairment is due to AD. Although the short half-life of the carbon-11 radiolabel has thus far limited the use of PIB to research, a second generation of tracers labeled with fluorine-18 has made it possible for amyloid PET to enter the clinical era. In the present review, we summarize the literature on amyloid imaging in a range of neurodegenerative conditions. We focus on potential clinical applications of amyloid PET and its role in the differential diagnosis of dementia. We suggest that amyloid imaging will be particularly useful in the evaluation of mildly affected, clinically atypical or early age-at-onset patients, and illustrate this with case vignettes from our practice. We emphasize that amyloid imaging should supplement (not replace) a detailed clinical evaluation. We caution against screening asymptomatic individuals, and discuss the limited positive predictive value in older populations. Finally, we review limitations and unresolved questions related to this exciting new technique.

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    • "Briefly, AD is characterized neuropathologically by at least five heterogeneous features, all of which support the progressive generation of abnormal tau and amyloid, neural and synaptic deficits and proinflammatory signaling to various degrees. These features include: the appearance of hyperphosphorylated tau-protein containing intracellular neurofibrillary tangles; amyloidogenesis - the progressive, age-related generation, aggregation and accumulation of Aβ peptides into dense, insoluble, proinflammatory and pathogenic deposits of senile plaque; reduced synaptic densities and synaptic protein assemblies; significant neuronal loss in the temporal lobe and hippocampal regions that, as AD progresses, radiates into the more distal parietal, frontal and occipital poles of the brain; and a unique, chronic and progressive smoldering inflammation of the neocortex and limbic system of the brain, especially in the middle to late stages of AD [11-18,20-25]. "
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    ABSTRACT: Abundant neurochemical, neuropathological, and genetic evidence suggests that a critical number of proinflammatory and innate immune system-associated factors are involved in the underlying pathological pathways that drive the sporadic Alzheimer's disease (AD) process. Most recently, a series of epigenetic factors - including a select family of inducible, proinflammatory, NF-κB-regulated small noncoding RNAs called miRNAs - have been shown to be significantly elevated in abundance in AD brain. These upregulated miRNAs appear to be instrumental in reshaping the human brain transcriptome. This reorganization of mRNA speciation and complexity in turn drives proinflammatory and pathogenic gene expression programs. The ensuing, progressively altered immune and inflammatory signaling patterns in AD brain support immunopathogenetic events and proinflammatory features of the AD phenotype. This report will briefly review what is known concerning NF-κB-inducible miRNAs that are significantly upregulated in AD-targeted anatomical regions of degenerating human brain cells and tissues. Quenching of NF-κB-sensitive inflammatory miRNA signaling using NF-κB-inhibitors such as the polyphenolic resveratrol analog trans-3,5,4'-trihydroxystilbene (CAY10512) may have some therapeutic value in reducing inflammatory neurodegeneration. Antagonism of NF-κB-inducing, and hence proinflammatory, epigenetic and environmental factors, such as the neurotrophic herpes simplex virus-1 and exposure to the potent neurotoxin aluminum, are briefly discussed. Early reports further indicate that miRNA neutralization employing anti-miRNA (antagomir) strategies may hold future promise in the clinical management of this insidious neurological disorder and expanding healthcare concern.
    Alzheimer's Research and Therapy 12/2012; 4(6):47. DOI:10.1186/alzrt150 · 3.98 Impact Factor
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    • "Some of these will indicate an evolution in terms of diagnostic accuracy, compared to less advanced technologies.21 Other novel tracers will be used primarily to stratify patients for targeted therapies.22-24 "
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    ABSTRACT: Clinical molecular imaging by use of PET and PET/CT is increasingly important in routine oncological practice worldwide. A vast majority of clinical PET investigations are performed with [(18)F]-fluorodeoxyglucose (FDG), but there is a growing interest in novel molecular probes among scientists and clinicians. Beyond FDG, a small number of different tracers have been shown to be of clinical value. With a growing commercial interest in tracer development, many more are under investigation. This review provides some examples of clinical situations where tracers other than FDG have been found useful and an outlook towards technical and regulatory development needed to allow the full impact of clinical PET to benefit the individual patient.
    Theranostics 05/2012; 2(5):427-36. DOI:10.7150/thno.3794 · 8.02 Impact Factor
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    ABSTRACT: Introduction: Alzheimer's disease (AD) is a common, progressive neurological disorder whose incidence is reaching epidemic proportions. The prevailing "amyloid cascade hypothesis," which maintains that the aberrant proteolysis of beta-amyloid precursor protein (βAPP) into neurotoxic amyloid beta (Aβ) peptides is central to the etiopathology of AD, continues to dominate pharmacological approaches to the clinical management of this insidious disorder. This review is a compilation and update on current pharmacological strategies designed to down-regulate Aβ42 peptide generation in an effort to ameliorate the tragedy of AD. Areas covered: This review utilized online data searches at various open online-access websites including the Alzheimer Association, Alzheimer Research Forum; individual drug company databases; the National Institutes of Health (NIH) Medline; Pharmaprojects database; Scopus; inter-University research communications; and unpublished research data. Expert opinion: Anti-acetylcholinesterase-, chelation-, N-methyl-D-aspartate (NMDA) receptor antagonist-, statin-, Aβ immunization-, β-secretase-, γ-secretase-based, and other strategies to modulate βAPP processing, have dominated pharmacological approaches directed against AD-type neurodegenerative pathology. Cumulative clinical results of these efforts remain extremely disappointing, and have had little overall impact on the clinical management of AD. While a number of novel approaches are in consideration and development, to date there is still no effective treatment or cure for this expanding healthcare concern.
    Expert Opinion on Emerging Drugs 03/2012; 17(1). DOI:10.1517/14728214.2012.672559 · 3.06 Impact Factor
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