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1.  Temporoparietal hypometabolism is common in FTLD and is associated with imaging diagnostic errors 
Archives of neurology  2010;68(3):329-337.
Objective
To evaluate the cause of diagnostic errors in the visual interpretation of positron emission tomography scans with 18F-fluorodeoxyglucose (FDG-PET) in patients with frontotemporal lobar degeneration (FTLD) and Alzheimer's disease (AD).
Design
Twelve trained raters unaware of clinical and autopsy information independently reviewed FDG-PET scans and provided their diagnostic impression and confidence of either FTLD or AD. Six of these raters also recorded whether metabolism appeared normal or abnormal in 5 predefined brain regions in each hemisphere – frontal cortex, anterior cingulate cortex, anterior temporal cortex, temporoparietal cortex and posterior cingulate cortex. Results were compared to neuropathological diagnoses.
Setting
Academic medical centers
Patients
45 patients with pathologically confirmed FTLD (n=14) or AD (n=31)
Results
Raters had a high degree of diagnostic accuracy in the interpretation of FDG-PET scans; however, raters consistently found some scans more difficult to interpret than others. Unanimity of diagnosis among the raters was more frequent in patients with AD (27/31, 87%) than in patients with FTLD (7/14, 50%) (p = 0.02). Disagreements in interpretation of scans in patients with FTLD largely occurred when there was temporoparietal hypometabolism, which was present in 7 of the 14 FTLD scans and 6 of the 7 lacking unanimity. Hypometabolism of anterior cingulate and anterior temporal regions had higher specificities and positive likelihood ratios for FTLD than temporoparietal hypometabolism had for AD.
Conclusions
Temporoparietal hypometabolism in FTLD is common and may cause inaccurate interpretation of FDG-PET scans. An interpretation paradigm that focuses on the absence of hypometabolism in regions typically affected in AD before considering FTLD is likely to misclassify a significant portion of FTLD scans. Anterior cingulate and/or anterior temporal hypometabolism indicates a high likelihood of FTLD, even when temporoparietal hypometabolism is present. Ultimately, the accurate interpretation of FDG-PET scans in patients with dementia cannot rest on the presence or absence of a single region of hypometabolism, but must take into account the relative hypometabolism of all brain regions.
doi:10.1001/archneurol.2010.295
PMCID: PMC3058918  PMID: 21059987
2.  Cortical α7 Nicotinic Acetylcholine Receptor and β-Amyloid Levels in Early Alzheimer’s Disease 
Archives of neurology  2009;66(5):646-651.
Objective
To examine α7 nicotinic acetylcholine receptor (nAChR) binding and β-amyloid (Aβ) peptide load in superior frontal cortex (SFC) across clinical and neuropathological stages of Alzheimer’s disease (AD).
Design
Quantitative measures of α7 nAChR by [3H]methyllycaconitine binding and Aβ concentration by enzyme-linked immunosorbent assay in SFC were compared across subjects with antemortem clinical classification of no cognitive impairment (NCI), mild cognitive impairment (MCI), or mild-moderate AD (mAD), and with post-mortem neuropathological diagnoses.
Setting
Academic medical center.
Subjects
Twenty-nine elderly retired clergy.
Results
Higher concentrations of total Aβ peptide in SFC were associated with clinical diagnosis of mAD (p=0.015), lower Mini Mental State Examination scores (p=0.0033), presence of cortical Aβ plaques (p=0.015), and likelihood of AD diagnosis by the NIA-Reagan criteria (p=0.0015). Increased α7 nAChR binding was associated with NIA-Reagan diagnosis (p=0.021) and, albeit weakly, the presence of cortical Aβ plaques (p=0.079). There was no correlation between the two biochemical measures.
Conclusions
These observations suggest that during the clinical progression from normal cognition to neurodegenerative disease state, total Aβ peptide concentration increases, while α7 nAChRs remain relatively stable in SFC. Regardless of subjects’ clinical status, however, elevated α7 nAChR binding is associated with increased Aβ plaque pathology, supporting the hypothesis that cellular expression of these receptors may be up-regulated selectively in Aβ plaque-burdened brain areas.
doi:10.1001/archneurol.2009.46
PMCID: PMC2841566  PMID: 19433665
acetylcholine; mild cognitive impairment; cholinergic; nicotinic; receptors; amyloid; dementia; frontal cortex
4.  Carbon 11–Labeled Pittsburgh Compound B and Carbon 11–Labeled (R)-PK11195 Positron Emission Tomographic Imaging in Alzheimer Disease 
Archives of neurology  2009;66(1):60-67.
Background
Alzheimer disease (AD) is defined neuropathologically by the presence of neurofibrillary tangles and plaques associated with tau and β-amyloid protein deposition. The colocalization of microglia and β-amyloid plaques has been widely reported in pathological examination of AD and suggests that neuroinflammation may play a role in pathogenesis and/or progression. Because postmortem histopathological analyses are limited to single end-stage assessment, the time course and nature of this relationship are not well understood.
Objective
To image microglial activation and β-amyloid deposition in the brains of subjects with and without AD.
Design, Setting, and Participants
Using two carbon 11 ([11C])–labeled positron emission tomographic imaging agents, Pittsburgh Compound B (PiB) and (R)-PK11195, we examined the relationship between amyloid deposition and microglial activation in different stages of AD using 5 control subjects, 6 subjects diagnosed with mild cognitive impairment, and 6 patients with mild to moderate AD.
Results
Consistent with prior reports, subjects with a clinical diagnosis of probable AD showed significantly greater levels of [11C]PiB retention than control subjects, whereas patients with mild cognitive impairment spanned a range from control-like to AD-like levels of [11C]PiB retention. Additionally, 2 asymptomatic control subjects also exhibited evidence of elevated PiB retention in regions associated with the early emergence of plaques in AD and may represent prodromal cases of AD. We observed no differences in brain [11C](R)-PK11195 retention when subjects were grouped by clinical diagnosis or the presence or absence of β-amyloid pathological findings as indicated by analyses of [11C]PiB retention.
Conclusions
These findings suggest that either microglial activation is limited to later stages of severe AD or [11C](R)-PK11195 is too insensitive to detect the level of microglial activation associated with mild to moderate AD.
doi:10.1001/archneurol.2008.511
PMCID: PMC2666881  PMID: 19139300
5.  Frequent Amyloid Deposition Without Significant Cognitive Impairment Among the Elderly 
Archives of neurology  2008;65(11):1509-1517.
Objective
To characterize the prevalence of amyloid deposition in a clinically unimpaired elderly population, as assessed by Pittsburgh Compound B (PiB) positron emission tomography (PET) imaging, and its relationship to cognitive function, measured with a battery of neuropsychological tests.
Design
Subjects underwent cognitive testing and PiB PET imaging (15 mCi for 90 minutes with an ECAT HR + scanner). Logan graphical analysis was applied to estimate regional PiB retention distribution volume, normalized to a cerebellar reference region volume, to yield distribution volume ratios (DVRs).
Setting
University medical center.
Participants
From a community-based sample of volunteers, 43 participants aged 65 to 88 years who did not meet diagnostic criteria for Alzheimer disease or mild cognitive impairment were included.
Main Outcome Measures
Regional PiB retention and cognitive test performance.
Results
Of 43 clinically unimpaired elderly persons imaged, 9 (21%) showed evidence of early amyloid deposition in at least 1 brain area using an objectively determined DVR cutoff. Demographic characteristics did not differ significantly between amyloid-positive and amyloid-negative participants, and neurocognitive performance was not significantly worse among amyloid-positive compared with amyloid-negative participants.
Conclusions
Amyloid deposition can be identified among cognitively normal elderly persons during life, and the prevalence of asymptomatic amyloid deposition may be similar to that of symptomatic amyloid deposition. In this group of participants without clinically significant impairment, amyloid deposition was not associated with worse cognitive function, suggesting that an elderly person with a significant amyloid burden can remain cognitively normal. However, this finding is based on relatively small numbers and needs to be replicated in larger cohorts. Longitudinal follow-up of these subjects will be required to support the potential of PiB imaging to identify preclinical Alzheimer disease, or, alternatively, to show that amyloid deposition is not sufficient to cause Alzheimer disease within some specified period.
doi:10.1001/archneur.65.11.1509
PMCID: PMC2636844  PMID: 19001171

Results 1-5 (5)