Focal hemosiderin deposits and β-amyloid load in the ADNI cohort
Prevalence and risk factors for focal hemosiderin deposits are important considerations when planning amyloid-modifying trials for treatment and prevention of Alzheimer's disease (AD).
Subjects were cognitively normal (n = 171), early-mild cognitive impairment (MCI) (n = 240), late-MCI (n = 111), and AD (n = 40) from the Alzheimer's Disease Neuroimaging Initiative (ADNI). Microhemorrhages and superficial siderosis were assessed at baseline and on all available MRIs at 3, 6, and 12 months. β-amyloid load was assessed with (18)F-florbetapir positron emission tomography.
Prevalence of superficial siderosis was 1% and prevalence of microhemorrhages was 25% increasing with age (P < .001) and β-amyloid load (P < .001). Topographic densities of microhemorrhages were highest in the occipital lobes and lowest in the deep/infratentorial regions. A greater number of microhemorrhages at baseline was associated with a greater annualized rate of additional microhemorrhages by last follow-up (rank correlation = 0.49; P < .001).
Focal hemosiderin deposits are relatively common in the ADNI cohort and are associated with β-amyloid load.
Available from: Clifford R Jack
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ABSTRACT: Most subjects with logopenic variant of primary progressive aphasia (lvPPA) have β-amyloid (Aβ) deposition on Pittsburgh Compound B positron emission tomography (PiB-PET), usually affecting prefrontal and temporoparietal cortices, with less occipital involvement.
To assess clinical and imaging features in lvPPA subjects with unusual topographic patterns of Aβ deposition with highest uptake in occipital lobe.
Thirty-three lvPPA subjects with Aβ deposition on PiB-PET were included in this case-control study. Line plots of regional PiB uptake were created, including frontal, temporal, parietal and occipital regions, for each subject. Subjects in which the line sloped downwards in occipital lobe (lvPPA-low), representing low uptake, were separated from those where the line sloped upwards in occipital lobe (lvPPA-high), representing unusually high occipital uptake compared to other regions. Clinical variables, atrophy on MRI, hypometabolism on 18F-fluorodeoxyglucose positron emission tomography (FDG-PET), and presence and distribution of microbleeds and white matter hyperintensities (WMHs) were assessed.
Seventeen subjects (52%) were classified as lvPPA-high. Mean occipital PiB uptake in lvPPA-high was higher than all other regions and higher than all regions in lvPPA-low. The lvPPA-high subjects performed more poorly on cognitive testing, including executive and visuospatial testing, but the two groups did not differ in aphasia severity. Proportion of microbleeds and WMH was higher in lvPPA-high than lvPPA-low. Parietal hypometabolism was greater in lvPPA-high than lvPPA-low.
Unusually high occipital Aβ deposition is associated with widespread cognitive impairment and different imaging findings in lvPPA. These findings help explain clinical heterogeneity in lvPPA and suggest that Aβ influences severity of overall cognitive impairment but not aphasia.
Journal of neurology, neurosurgery, and psychiatry 08/2013; 84(12). DOI:10.1136/jnnp-2013-305628 · 6.81 Impact Factor
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ABSTRACT: To assist investigators in making design choices, we modeled Alzheimer's disease prevention clinical trials. We used longitudinal Clinical Dementia Rating Scale Sum of Boxes data, retention rates, and the proportions of trial-eligible cognitively normal participants age 65 and older in the National Alzheimer's Coordinating Center Uniform Data Set to model trial sample sizes, the numbers needed to enroll to account for drop out, and the numbers needed to screen to successfully complete enrollment. We examined how enrichment strategies affected each component of the model. Relative to trials enrolling 65-year-old individuals, trials enriching for older (minimum 70 or 75) age required reduced sample sizes, numbers needed to enroll, and numbers needed to screen. Enriching for subjective memory complaints reduced sample sizes and numbers needed to enroll more than age enrichment, but increased the number needed to screen. We conclude that Alzheimer's disease prevention trials can enroll elderly participants with minimal effect on trial retention and that enriching for older individuals with memory complaints might afford efficient trial designs.
Neurobiology of aging 10/2013; 35(3). DOI:10.1016/j.neurobiolaging.2013.09.001 · 5.01 Impact Factor
Available from: Paul A. Yates
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ABSTRACT: Cerebral microbleeds (microbleeds) are small, punctuate hypointense lesions seen in T2* Gradient-Recall Echo (GRE) and Susceptibility-Weighted (SWI) Magnetic Resonance Imaging (MRI) sequences, corresponding to areas of hemosiderin breakdown products from prior microscopic hemorrhages. They occur in the setting of impaired small vessel integrity, commonly due to either hypertensive vasculopathy or cerebral amyloid angiopathy. Microbleeds are more prevalent in individuals with Alzheimer's disease (AD) dementia and in those with both ischemic and hemorrhagic stroke. However they are also found in asymptomatic individuals, with increasing prevalence with age, particularly in carriers of the Apolipoprotein (APOE) ε4 allele. Other neuroimaging findings that have been linked with microbleeds include lacunar infarcts and white matter hyperintensities on MRI, and increased cerebral β-amyloid burden using (11)C-PiB Positron Emission Tomography. The presence of microbleeds has been suggested to confer increased risk of incident intracerebral hemorrhage - particularly in the setting of anticoagulation - and of complications of immunotherapy for AD. Prospective data regarding the natural history and sequelae of microbleeds are currently limited, however there is a growing evidence base that will serve to inform clinical decision-making in the future.
Frontiers in Neurology 01/2014; 4:205. DOI:10.3389/fneur.2013.00205
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