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F-fluorodeoxyglucose (FDG) Positron Emission Tomography (PET) is a widely used diagnostic tool that can detect and quantify pathophysiology, as assessed through changes in cerebral glucose ...metabolism.
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F-FDG PET scans can be analyzed using voxel-based statistical methods such as Statistical Parametric Mapping (SPM) that provide statistical maps of brain abnormalities in single patients. In order to perform SPM, a “spatial normalization” of an individual’s PET scan is required to match a reference PET template. The PET template currently used for SPM normalization is based on
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O-H
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O images and does not resemble either the specific metabolic features of
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F-FDG brain scans or the specific morphological characteristics of individual brains affected by neurodegeneration. Thus, our aim was to create a new
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F-FDG PET aging and dementia-specific template for spatial normalization, based on images derived from both age-matched controls and patients. We hypothesized that this template would increase spatial normalization accuracy and thereby preserve crucial information for research and diagnostic purposes. We investigated the statistical sensitivity and registration accuracy of normalization procedures based on the standard and new template—at the single-subject and group level—independently for subjects with Mild Cognitive Impairment (MCI), probable Alzheimer’s Disease (AD), Frontotemporal lobar degeneration (FTLD) and dementia with Lewy bodies (DLB). We found a significant statistical effect of the population-specific FDG template-based normalisation in key anatomical regions for each dementia subtype, suggesting that spatial normalization with the new template provides more accurate estimates of metabolic abnormalities for single-subject and group analysis, and therefore, a more effective diagnostic measure.
The current model of Alzheimer disease (AD) stipulates that brain amyloidosis biomarkers turn abnormal earliest, followed by cortical hypometabolism, and finally brain atrophy ones. The aim of this ...study is to provide clinical evidence of the model in patients with mild cognitive impairment (MCI).
A total of 73 patients with MCI from 3 European memory clinics were included. Brain amyloidosis was assessed by CSF Aβ42 concentration, cortical metabolism by an index of temporoparietal hypometabolism on FDG-PET, and brain atrophy by automated hippocampal volume. Patients were divided into groups based on biomarker positivity: 1) Aβ42- FDG-PET- Hippo-, 2) Aβ42+ FDG-PET- Hippo-, 3) Aβ42 + FDG-PET + Hippo-, 4) Aβ42 + FDG-PET+ Hippo+, and 5) any other combination not in line with the model. Measures of validity were prevalence of group 5, increasing incidence of progression to dementia with increasing biological severity, and decreasing conversion time.
When patients with MCI underwent clinical follow-up, 29 progressed to dementia, while 44 remained stable. A total of 26% of patients were in group 5. Incident dementia was increasing with greater biological severity in groups 1 to 5 from 4% to 27%, 64%, and 100% (p for trend < 0.0001), and occurred increasingly earlier (p for trend = 0.024).
The core biomarker pattern is in line with the current pathophysiologic model of AD. Fully normal and fully abnormal pattern is associated with exceptional and universal development of dementia. Cases not in line might be due to atypical neurobiology or inaccurate thresholds for biomarker (ab)normality.
Morphological abnormalities have been reported for the hippocampi and amygdalae in young schizophrenia patients, but very little is known about the pattern of abnormalities in elderly schizophrenia ...patients. Here we investigated local structural differences in the hippocampi and amygdalae of elderly schizophrenia patients compared with healthy elderly subjects. We also related these differences to clinical symptom severity.
20 schizophrenia patients (mean age: 67.4 ± 6.2 years; Mini-Mental State Exam: 22.8 ± 4.4) and 20 healthy elderly subjects (70.3 ± 7.5 years; 29.0 ± 1.1) underwent high resolution magnetic resonance imaging of the brain. The Radial Atrophy Mapping technique was used to reconstruct the 3D shape of the amygdala and the hippocampus. Local differences in tissue reductions were computed between groups and permutation tests were run to correct for multiple comparisons, in statistical maps thresholded at p = 0.05.
Significant tissue reduction was observed bilaterally in the amygdala and hippocampus of schizophrenia patients. The basolateral-ventral-medial amygdalar nucleus showed the greatest involvement, with over 30% local tissue reduction. The centro-medial, cortical, and lateral nuclei were also atrophic in patients. The hippocampus showed significant tissue loss in the medio-caudal and antero-lateral aspects of CA1, and in medial section of its left head (pre- and para-subiculum). In the left amygdala and hippocampus, local tissue volumes were significantly correlated with negative symptoms.
Tissue loss and altered morphology were found in elderly schizophrenia patients. Tissue loss mapped to amygdalo-hippocampal subregions known to have bidirectional and specific connections with frontal cortical and limbic structures and was related to clinical severity.
The aim of this study was to investigate predictors of progressive cognitive deterioration in patients with suspected non-Alzheimer disease pathology (SNAP) and mild cognitive impairment (MCI).
We ...measured markers of amyloid pathology (CSF β-amyloid 42) and neurodegeneration (hippocampal volume on MRI and cortical metabolism on (18)F-fluorodeoxyglucose-PET) in 201 patients with MCI clinically followed for up to 6 years to detect progressive cognitive deterioration. We categorized patients with MCI as A+/A- and N+/N- based on presence/absence of amyloid pathology and neurodegeneration. SNAPs were A-N+ cases.
The proportion of progressors was 11% (8/41), 34% (14/41), 56% (19/34), and 71% (60/85) in A-N-, A+N-, SNAP, and A+N+, respectively; the proportion of APOE ε4 carriers was 29%, 70%, 31%, and 71%, respectively, with the SNAP group featuring a significantly different proportion than both A+N- and A+N+ groups (p ≤ 0.005). Hypometabolism in SNAP patients was comparable to A+N+ patients (p = 0.154), while hippocampal atrophy was more severe in SNAP patients (p = 0.002). Compared with A-N-, SNAP and A+N+ patients had significant risk of progressive cognitive deterioration (hazard ratio = 2.7 and 3.8, p = 0.016 and p < 0.001), while A+N- patients did not (hazard ratio = 1.13, p = 0.771). In A+N- and A+N+ groups, none of the biomarkers predicted time to progression. In the SNAP group, lower time to progression was correlated with greater hypometabolism (r = 0.42, p = 0.073).
Our findings support the notion that patients with SNAP MCI feature a specific risk progression profile.
Progressive brain atrophy is believed to be the Alzheimer’s disease (AD) marker with the greatest evidence for validity. Mapping the topography of cortical atrophy throughout the stages of severity ...may allow the neural networks affected to be identified. Twenty healthy elderly persons (OH, MMSE 29.1 ± 1.0), 11 patients with incipient AD (iAD, 26.5 ± 2.0), 15 with mild AD (miAD, 23.5 ± 2.2), and 15 with moderate AD (moAD, 16.5 ± 2.0) underwent 3D magnetic resonance. Cortical pattern matching analysis was performed and maps of percent differences in gray matter distribution were computed between the following groups: iAD versus OH, miAD versus iAD, and moAD versus miAD. Compared to OH, iAD patients exhibited a mean cortical gray matter loss of 9–20% in areas encompassing the polysynaptic hippocampal pathway (posterior cingulate/retrosplenial and medial temporal cortex) and subgenual/orbitofrontal cortices, and a less widespread loss of 5–11% in other neocortical areas. Compared to iAD, miAD featured widespread mean gray matter loss of 14–19% in areas encompassing the direct hippocampal pathway (temporal pole, temporoparietal association cortex, and dorsal prefrontal cortex), sensorimotor, and visual cortex, with a less marked loss (7–9%) in the polysynaptic pathway areas. Compared to miAD, only atrophy in the primary sensorimotor cortex was still relatively marked in moAD, with a mean gray matter loss of 10–11%; the loss in other regions was generally below 10%. These findings suggest that the polysynaptic hippocampal pathway is affected in iAD, the direct pathway and sensorimotor and visual networks are affected in moAD, and the sensorimotor network is affected in moAD.
Abstract Introduction Proposed diagnostic criteria (international working group and National Institute on Aging and Alzheimer's Association) for Alzheimer's disease (AD) include markers of ...amyloidosis (abnormal cerebrospinal fluid CSF amyloid beta Aβ42) and neurodegeneration (hippocampal atrophy, temporo-parietal hypometabolism on 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET), and abnormal CSF tau). We aim to compare the accuracy of these biomarkers, individually and in combination, in predicting AD among mild cognitive impairment (MCI) patients. Methods In 73 MCI patients, followed to ascertain AD progression, markers were measured. Sensitivity and specificity, positive (LR+) and negative (LR−) likelihood ratios, and crude and adjusted hazard ratios were computed. Results Twenty-nine MCI patients progressed and 44 remained stable. Positivity to any marker achieved the lowest LR− (0.0), whereas the combination Aβ42 plus FDG-PET achieved the highest LR+ (6.45). In a survival analysis, positivity to any marker was associated with 100% conversion rate, whereas negativity to all markers was associated with 100% stability. Discussion The best criteria combined amyloidosis and neurodegeneration biomarkers, whereas the individual biomarker with the best performance was FDG-PET.
Objective
The aim of this study is to assess the impact of age at onset on the prognostic value of Alzheimer’s biomarkers in a large sample of patients with mild cognitive impairment (MCI).
Methods
...We measured Aβ42,
t
-tau, hippocampal volume on magnetic resonance imaging (MRI) and cortical metabolism on fluorodeoxyglucose–positron emission tomography (FDG-PET) in 188 MCI patients followed for at least 1 year. We categorised patients into earlier and later onset (EO/LO). Receiver operating characteristic curves and corresponding areas under the curve (AUCs) were performed to assess and compar the biomarker prognostic performances in EO and LO groups. Linear Model was adopted for estimating the time-to-progression in relation with earlier/later onset MCI groups and biomarkers.
Results
In earlier onset patients, all the assessed biomarkers were able to predict cognitive decline (
p
< 0.05), with FDG-PET showing the best performance. In later onset patients, all biomarkers but
t
-tau predicted cognitive decline (
p
< 0.05). Moreover, FDG-PET alone in earlier onset patients showed a higher prognostic value than the one resulting from the combination of all the biomarkers in later onset patients (earlier onset AUC 0.935 vs later onset AUC 0.753,
p
< 0.001). Finally, FDG-PET showed a different prognostic value between earlier and later onset patients (
p
= 0.040) in time-to-progression allowing an estimate of the time free from disease.
Discussion
FDG-PET may represent the most universal tool for the establishment of a prognosis in MCI patients and may be used for obtaining an onset-related estimate of the time free from disease.
Mild alterations in cognitive function are present in normal aging and severe cognitive alterations are a hallmark of Alzheimer's disease (AD). Cognitive deficits are prevalent in patients with ...schizophrenia (SCZ) and worsen with old age. We recently reported that elderly SCZ patients show reduced levels of amyloid‐beta (Aβ)1–42 in cerebrospinal fluid (CSF). To further clarify the role of Aβ in cognitive decline, we analyzed the whole panel of CSF Aβ isoforms in elderly SCZ patients as well as in sporadic AD using SELDI TOF MS. The immunoproteomic study revealed, in all analyzed CSF samples, the presence of 15 different Aβ peptides. In CSF from SCZ, we detected an overall strong reduction of almost all Aβ species while in sporadic AD Aβ1–42 was the only peptide reduced. A significant independent association between Aβ1–40 levels and global cognition was found in SCZ. In addition, in SCZ patients, duration of therapy was positively associated with soluble amyloid precursor protein alpha levels, the total amount of CSF Aβ and the most abundant Aβ1–40 isoform. These data suggests a dysmetabolism of amyloid precursor protein in older SCZ patients. Thus, the quite comparable reduction of CSF Aβ1–42 in AD and in elderly SCZ patients reflects different pathophysiological dynamics in ageing brain.
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