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Amyloid deposition in semantic dementia: a positron emission tomography study.

ABSTRACT: BACKGROUND:Pittsburgh compound B ([11C]-PIB) identifies amyloid-? (A?) deposition in vivo. Asymptomatic A? deposition has been reported consistently in some healthy older subjects. Of patients with frontotemporal dementia, those who have later onset have a higher potential for A? deposition. OBJECTIVE:Comparison of A? deposition in Alzheimer's disease (AD), healthy older controls, and patients with early- and late-onset semantic dementia (SD), a subtype of frontotemporal dementia. METHODS:Subjects were recruited from tertiary academic care centers specializing in assessment and management of patients with neurodegenerative disease. We used the radiotracer [11C]-PIB in a high-resolution positron emission tomography scanner to evaluate 11 participants with SD (six with onset before age 65 and five with later onset), 9 with probable AD, and 10 controls over age 60. The main outcome measures were frontal, temporal, parietal, and total [11C]-PIB standardized uptake value ratios to establish PIB-positive (PIB+) cutoff. RESULTS:The five patients with late-onset SD were PIB-negative. Two of six with early-onset SD, seven of nine with AD, and 1 of 10 controls were PIB+. The SD participants who were PIB+ did not have memory or visuospatial deficits that are typical in AD. CONCLUSIONS:A? deposition does not seem to be associated with late-onset SD. Future larger studies might confirm whether a significant minority of early-onset SD patients exhibit A? deposition. Copyright © 2016 John Wiley & Sons, Ltd.

SUBMITTER: Brown EE

PROVIDER: S-EPMC6139433 | biostudies-literature | 2016 Sep

REPOSITORIES: biostudies-literature

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Amyloid deposition in semantic dementia: a positron emission tomography study.

Brown Eric E EE Graff-Guerrero Ariel A Houle Sylvain S Mizrahi Romina R Wilson Alan A AA Pollock Bruce G BG Mulsant Benoit H BH Felsky Daniel D Voineskos Aristotle N AN Tang-Wai David F DF Verhoeff Nicolaas P L G NP Freedman Morris M Ismail Zahinoor Z Chow Tiffany W TW

International journal of geriatric psychiatry 20160125 9

<h4>Background</h4>Pittsburgh compound B ([11C]-PIB) identifies amyloid-β (Aβ) deposition in vivo. Asymptomatic Aβ deposition has been reported consistently in some healthy older subjects. Of patients with frontotemporal dementia, those who have later onset have a higher potential for Aβ deposition.<h4>Objective</h4>Comparison of Aβ deposition in Alzheimer's disease (AD), healthy older controls, and patients with early- and late-onset semantic dementia (SD), a subtype of frontotemporal dementia. ...[more]

PMID: 26807731

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Project description:BackgroundDisclosure of amyloid positron emission tomography (PET) results to individuals without dementia has become standard practice in secondary prevention trials and also increasingly occurs in clinical practice. However, this is controversial given the current lack of understanding of the predictive value of a PET result at the individual level and absence of disease-modifying treatments. In this study, we systematically reviewed the literature on the disclosure of amyloid PET in cognitively normal (CN) individuals and patients with mild cognitive impairment (MCI) in both research and clinical settings.MethodsWe performed a systematic literature search of four scientific databases. Two independent reviewers screened the identified records and selected relevant articles. Included articles presented either empirical data or theoretical data (i.e. arguments in favor or against amyloid status disclosure). Results from the theoretical data were aggregated and presented per theme.ResultsOf the seventeen included studies, eleven reported empirical data and six provided theoretical arguments. There was a large variation in the design of the empirical studies, which were almost exclusively in the context of cognitively normal trial participants, comprising only two prospective cohort studies quantitatively assessing the psychological impact of PET result disclosure which showed a low risk of psychological harm after disclosure. Four studies showed that both professionals and cognitively normal individuals support amyloid PET result disclosure and underlined the need for clear disclosure protocols. From the articles presenting theoretical data, we identified 51 'pro' and 'contra' arguments. Theoretical arguments in favor or against disclosure were quite consistent across population groups and settings. Arguments against disclosure focused on the principle of non-maleficence, whereas its psychological impact and predictive value is unknown. Important arguments in favor of amyloid disclosure are the patients right to know (patient autonomy) and that it enables early future decision making.DiscussionBefore amyloid PET result disclosure in individuals without dementia in a research or clinical setting is ready for widespread application, more research is needed about its psychological impact, and its predictive value at an individual level. Finally, communication materials and strategies to support disclosure of amyloid PET results should be further developed and prospectively evaluated.

Project description:BackgroundAs more older adults undergo surgery, it is critical to understand the long-term effects of surgery on brain health, particularly in relation to the development of Alzheimer's disease. This study examined the association of surgical hospitalization with subsequent brain β-amyloid deposition in nondemented older adults.MethodsThe Atherosclerosis Risk in Communities-Positron Emission Tomography (ARIC-PET) study is a prospective cohort study of 346 participants without dementia who underwent florbetapir PET imaging. Active surveillance of local hospitals and annual participant contact were used to gather hospitalization and surgical information (International Classification of Disease, Ninth Revision, Clinical Modification codes) over the preceding 24-yr period. Brain amyloid measured using florbetapir PET imaging was the primary outcome. Elevated amyloid was defined as a standardized uptake value ratio of more than 1.2.ResultsOf the 313 participants included in this analysis (age at PET: 76.0 [SD 5.4]; 56% female), 72% had a prior hospitalization, and 50% had a prior surgical hospitalization. Elevated amyloid occurred in 87 of 156 (56%) participants with previous surgical hospitalization, compared with 45 of 87 (52%) participants who had no previous hospitalization. Participants with previous surgical hospitalizations did not show an increased odds of elevated brain amyloid (odds ratio, 1.32; 95% CI, 0.72 to 2.40; P = 0.370) after adjusting for confounders (primary analysis). Results were similar using the reference group of all participants without previous surgery (hospitalized and nonhospitalized; odds ratio, 1.58; 95% CI, 0.96 to 2.58; P = 0.070). In a prespecified secondary analysis, participants with previous surgical hospitalization did demonstrate increased odds of elevated amyloid when compared with participants hospitalized without surgery (odds ratio, 2.10; 95% CI, 1.09 to 4.05; P = 0.026). However, these results were attenuated and nonsignificant when alternative thresholds for amyloid-positive status were used.ConclusionsThe results do not support an association between surgical hospitalization and elevated brain amyloid.

Project description:PurposePathological studies suggest that neuroinflammation is exacerbated by increased beta-amyloid (A?) levels in the brain early in Alzheimer's disease (AD). The time course and relationships between astrocytosis and A? deposition were examined using multitracer in vivo positron emission tomography (PET) imaging in an AD transgenic mouse model, followed by postmortem autoradiography and immunohistochemistry analysis.MethodsPET imaging with the amyloid plaque tracer (11)C-AZD2184 and the astroglial tracer (11)C-deuterium-L-deprenyl ((11)C-DED) was carried out in APPswe mice aged 6, 8-15 and 18-24 months (4-6 animals/group) and in wild-type (wt) mice aged 8-15 and 18-24 months (3-6 animals/group). Tracer uptake was quantified by region of interest analysis using PMOD software and a 3-D digital mouse brain atlas. Postmortem brain tissues from the same APPswe and wt mice in all age groups were analysed for A? deposition and astrocytosis by in vitro autoradiography using (3)H-AZD2184, (3)H-Pittsburgh compound B (PIB) and (3)H-L-deprenyl and immunostaining performed with antibodies for A?42 and glial fibrillary acidic protein (GFAP) in sagittal brain sections.Results(11)C-AZD2184 PET retention in the cerebral cortices of APPswe mice was significantly higher at 18-24 months than in age-matched wt mice. Cortical and hippocampal (11)C-DED PET binding was significantly higher at 6 months than at 8-15 months or 18-24 months in APPswe mice, and it was also higher than at 8-15 months in wt mice. In vitro autoradiography (3)H-AZD2184 and (3)H-PIB binding confirmed the in vivo findings with (11)C-AZD2184 and demonstrated age-dependent increases in A? deposition in APPswe cortex and hippocampus. There were no significant differences between APPswe and wt mice in (3)H-L-deprenyl autoradiography binding across age groups. Immunohistochemical quantification demonstrated more A?42 deposits in the cortex and hippocampus and more GFAP(+) reactive astrocytes in the hippocampus at 18-24 months than at 6 months in APPswe mice.ConclusionThe findings provide further in vivo evidence that astrocytosis occurs early in AD, preceding A? plaque deposition.

Dataset Information

Amyloid deposition in semantic dementia: a positron emission tomography study.

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Amyloid deposition in semantic dementia: a positron emission tomography study.

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