The Use of Event Related Potentials to Predict Amyloid PET Status Among Patients from a Memory Disorders Clinic.

Background: Amyloid positron emission tomography (PET) scans provide in vivo evidence of Alzheimer's disease (AD); however, their high cost limits their use in standard clinical care. Event related potentials (ERPs) may represent an inexpensive and non-invasive additional method for detecting AD pathology. Objective: We investigated whether ERPs, along with neuropsychological data, serve as predictors of amyloid PET status in patients with memory complaints. Methods: Veterans aged 50-100 were recruited from a memory disorders clinic. Participants underwent a neuropsychological battery and an ERP auditory oddball protocol. Twenty-eight patients had a positive amyloid PET scan, and thirty-nine patients had a negative scan. Results: ERP-P200 target amplitude and P200 standard latency were predictors of amyloid PET status. When submitting to ROC analysis, P200 standard latency exhibited the highest specificity and sensitivity in predicting amyloid PET positivity, correctly classifying the amyloid PET status for 86% of patients. Conclusions: ERP-P200 measures are strong indicators of amyloid-ß presence in patients from a memory disorder clinic. Increased P200 amplitude and decreased P200 latency in patients with a positive amyloid PET scan may be attributed to hyperactivation of perceptual bottom-up processes compensating for AD-related synaptic loss in the fronto-parietal networks.

Stress testing the Centiloid: Precision and variability of PET quantification of amyloid pathology.

INTRODUCTION: Assessing the potential sources of bias and variability of the Centiloid (CL) scale is fundamental for its appropriate clinical application. METHODS: We included 533 participants from AMYloid imaging to Prevent Alzheimer's Disease (AMYPAD DPMS) and Alzheimer's Disease Neuroimaging Initiative (ADNI) cohorts. Thirty-two CL pipelines were created using different combinations of reference region (RR), RR and target types, and quantification spaces. Generalized estimating equations stratified by amyloid positivity were used to assess the impact of the quantification pipeline, radiotracer, age, brain atrophy, and harmonization status on CL. RESULTS: RR selection and RR type impact CL the most, particularly in amyloid-negative individuals. The standard CL pipeline with the whole cerebellum as RR is robust against brain atrophy and differences in image resolution, with 95% confidence intervals below ± 3.95 CL for amyloid beta positivity cutoffs (CL < 24). DISCUSSION: The standard CL pipeline is recommended for most scenarios. Confidence intervals should be considered when operationalizing CL cutoffs in clinical and research settings. HIGHLIGHTS: We developed a framework for evaluating Centiloid (CL) variability to different factors. Reference region selection and delineation had the highest impact on CL values. Whole cerebellum (WCB) and whole cerebellum plus brainstem (WCB+BSTM) as reference regions yielded consistent results across tracers. The standard CL pipeline is robust against atrophy and image resolution variation. Estimated within- and between-pipeline variability (95% confidence interval) in absolute CL units.

Spatial extent as a sensitive amyloid-PET metric in preclinical Alzheimer's disease.

INTRODUCTION: Spatial extent-based measures of how far amyloid beta (Aß) has spread throughout the neocortex may be more sensitive than traditional Aß-positron emission tomography (PET) measures of Aß level for detecting early Aß deposits in preclinical Alzheimer's disease (AD) and improve understanding of Aß's association with tau proliferation and cognitive decline. METHODS: Pittsburgh Compound-B (PIB)-PET scans from 261 cognitively unimpaired older adults from the Harvard Aging Brain Study were used to measure Aß level (LVL; neocortical PIB DVR) and spatial extent (EXT), calculated as the proportion of the neocortex that is PIB+. RESULTS: EXT enabled earlier detection of Aß deposits longitudinally confirmed to reach a traditional LVL-based threshold for Aß+ within 5 years. EXT improved prediction of cognitive decline (Preclinical Alzheimer Cognitive Composite) and tau proliferation (flortaucipir-PET) over LVL. DISCUSSION: These findings indicate EXT may be more sensitive to Aß's role in preclinical AD than level and improve targeting of individuals for AD prevention trials. HIGHLIGHTS: Aß spatial extent (EXT) was measured as the percentage of the neocortex with elevated Pittsburgh Compound-B. Aß EXT improved detection of Aß below traditional PET thresholds. Early regional Aß deposits were spatially heterogeneous. Cognition and tau were more closely tied to Aß EXT than Aß level. Neocortical tau onset aligned with reaching widespread neocortical Aß.

Donanemab, another anti-Alzheimer's drug with risk and uncertain benefit.

Based on "reducing amyloid plaques in the brain", the U.S. Food and Drug Administration has granted accelerated and full approval for two monoclonal anti-Alzheimer's antibodies, aducanumab and lecanemab, respectively. Approval of a third antibody, donanemab, is pending. Moreover, lecanemab and donanemab are claimed to cause delay in the cognitive decline that characterizes the disease. We believe that these findings are subject to misinterpretation and statistical bias. Donanemab is claimed to cause removal of up to 86 % of cerebral amyloid and 36 % delay in cognitive decline compared to placebo. In reality, these are very small changes on an absolute scale and arguably less than what can be achieved with cholinesterase inhibitor/memantine therapy. Moreover, the "removal" of amyloid, based on the reduced accumulation of amyloid-PET tracer, most likely also reflects therapy-related tissue damage. This would also correlate with the minimal clinical effect, the increased frequency of amyloid-related imaging abnormalities, and the accelerated loss of brain volume in treated compared to placebo patients observed with these antibodies. We recommend halting approvals of anti-AD antibodies until these issues are fully understood to ensure that antibody treatment does not cause more harm than benefit to patients.

Amyloid-PET imaging predicts functional decline in clinically normal individuals.

BACKGROUND: There is good evidence that elevated amyloid-ß (Aß) positron emission tomography (PET) signal is associated with cognitive decline in clinically normal (CN) individuals. However, it is less well established whether there is an association between the Aß burden and decline in daily living activities in this population. Moreover, Aß-PET Centiloids (CL) thresholds that can optimally predict functional decline have not yet been established. METHODS: Cross-sectional and longitudinal analyses over a mean three-year timeframe were performed on the European amyloid-PET imaging AMYPAD-PNHS dataset that phenotypes 1260 individuals, including 1032 CN individuals and 228 participants with questionable functional impairment. Amyloid-PET was assessed continuously on the Centiloid (CL) scale and using Aß groups (CL < 12 = Aß-, 12 ≤ CL ≤ 50 = Aß-intermediate/Aß± , CL > 50 = Aß+). Functional abilities were longitudinally assessed using the Clinical Dementia Rating (Global-CDR, CDR-SOB) and the Amsterdam Instrumental Activities of Daily Living Questionnaire (A-IADL-Q). The Global-CDR was available for the 1260 participants at baseline, while baseline CDR-SOB and A-IADL-Q scores and longitudinal functional data were available for different subsamples that had similar characteristics to those of the entire sample. RESULTS: Participants included 765 Aß- (61%, Mdnage = 66.0, IQRage = 61.0-71.0; 59% women), 301 Aß± (24%; Mdnage = 69.0, IQRage = 64.0-75.0; 53% women) and 194 Aß+ individuals (15%, Mdnage = 73.0, IQRage = 68.0-78.0; 53% women). Cross-sectionally, CL values were associated with CDR outcomes. Longitudinally, baseline CL values predicted prospective changes in the CDR-SOB (bCL*Time = 0.001/CL/year, 95% CI [0.0005,0.0024], p = .003) and A-IADL-Q (bCL*Time = -0.010/CL/year, 95% CI [-0.016,-0.004], p = .002) scores in initially CN participants. Increased clinical progression (Global-CDR > 0) was mainly observed in Aß+ CN individuals (HRAß+ vs Aß- = 2.55, 95% CI [1.16,5.60], p = .020). Optimal thresholds for predicting decline were found at 41 CL using the CDR-SOB (bAß+ vs Aß- = 0.137/year, 95% CI [0.069,0.206], p < .001) and 28 CL using the A-IADL-Q (bAß+ vs Aß- = -0.693/year, 95% CI [-1.179,-0.208], p = .005). CONCLUSIONS: Amyloid-PET quantification supports the identification of CN individuals at risk of functional decline. TRIAL REGISTRATION: The AMYPAD PNHS is registered at www.clinicaltrialsregister.eu with the EudraCT Number: 2018-002277-22.

"There has to be more caring": patient and care partner experiences of the disclosure of amyloid-ß PET scan results.

OBJECTIVES: To explore patient and care partner experiences of receiving an amyloid scan result, with a focus on how clinician disclosure practices influenced patient and care partner emotional responses to the scan result and/or diagnosis. METHODS: Semi-structured interviews with 38 people with mild cognitive impairment or dementia and 62 care partners who experienced the disclosure of results from an amyloid PET scan as part of the CARE-IDEAS study. We used thematic analysis to analyze interview transcripts. RESULTS: We identified four aspects of the disclosure process that could influence patient and care partner emotional experiences of the scan result/diagnosis: (1) mode of delivery, (2) presence of a care partner, (3) clarity of the scan result explanation, and (4) discussion of post-scan treatment and support options. CONCLUSIONS: Emotional experiences of an amyloid scan result can vary depending on how results are communicated. These findings support previous efforts to develop standard disclosure protocols. Scan results should be delivered in person with the care partner present. Clinicians should give a clear explanation of the result and its implications in an empathetic manner. Options for treatment and support should be discussed for all patients.

New objective simple evaluation methods of amyloid PET/CT using whole-brain histogram and Top20%-Map.

OBJECTIVE: This study aims to assess the utility of newly developed objective methods for the evaluation of intracranial abnormal amyloid deposition using PET/CT histogram without use of cortical ROI analyses. METHODS: Twenty-five healthy volunteers (HV) and 38 patients with diagnosed or suspected dementia who had undergone 18F-FPYBF-2 PET/CT were retrospectively included in this study. Out of them, 11C-PiB PET/CT had been also performed in 13 subjects. In addition to the conventional methods, namely visual judgment and quantitative analyses using composed standardized uptake value ratio (comSUVR), the PET images were also evaluated by the following new parameters: the skewness and the mode-to-mean ratio (MMR) obtained from the histogram of the brain parenchyma; Top20%-map highlights the areas with high tracer accumulation occupying 20% volume of the total brain parenchymal on the individual's CT images. We evaluated the utility of the new methods using histogram compared with the visual assessment and comSUVR. The results of these new methods between 18F-FPYBF-2 and 11C-PiB were also compared in 13 subjects. RESULTS: In visual analysis, 32, 9, and 22 subjects showed negative, border, and positive results, and composed SUVR in each group were 1.11 ± 0.06, 1.20 ± 0.13, and 1.48 ± 0.18 (p < 0.0001), respectively. Visually positive subjects showed significantly low skewness and high MMR (p < 0.0001), and the Top20%-Map showed the presence or absence of abnormal deposits clearly. In comparison between the two tracers, visual evaluation was all consistent, and the ComSUVR, the skewness, the MMR showed significant good correlation. The Top20%-Maps showed similar pattern. CONCLUSIONS: Our new methods using the histogram of the brain parenchymal accumulation are simple and suitable for clinical practice of amyloid PET, and Top20%-Map on the individual's brain CT can be of great help for the visual assessment.

At-Home Administration of Gantenerumab by Care Partners to People with Early Alzheimer's Disease: Feasibility, Safety and Pharmacodynamic Impact.

BACKGROUND: Monoclonal antibodies that target amyloid-beta and remove amyloid plaques can slow cognitive and functional decline in early Alzheimer's disease. Gantenerumab is a subcutaneously administered fully-human anti-amyloid-beta monoclonal antibody with highest affinity for aggregated amyloid-beta. Since the phase 3 GRADUATE trials did not meet the primary endpoint (change from baseline to Week 116 in Clinical Dementia Rating scale - Sum of Boxes), development of gantenerumab in sporadic Alzheimer's disease was stopped and all ongoing trials were terminated early due to sponsor decision. Subcutaneous administration at the clinic or at home by care partner would be an important option for other therapies in this class in order to increase flexibility and reduce overall burden. The insights obtained from the experience with gantenerumab home administration by care partner in the phase 2 GRADUATION trial will serve to guide the ongoing efforts with other anti-amyloid-beta antibodies. OBJECTIVES: To evaluate the pharmacodynamic effects on brain amyloid load of once weekly subcutaneous administration of gantenerumab and the safety and feasibility of home administration by care partners. DESIGN: Phase 2, open-label, single arm study. SETTING: Multicenter trial conducted in 33 sites in 8 countries from November 2020 to March 2023. PARTICIPANTS: Participants aged 50 to 90 with early symptomatic Alzheimer's disease (mild cognitive impairment/mild dementia due to Alzheimer's disease), and evidence of amyloid positron emission tomography positivity. INTERVENTION: Participants could receive up to 255 mg gantenerumab once-weekly, administered subcutaneously at site or at home by healthcare professionals or non-healthcare-professional care partners. MEASUREMENTS: The primary endpoint was the change from baseline to Week 52 and to Week 104 in brain amyloid load as measured by PET centiloid levels. The secondary endpoints were responses to the home administration questionnaire, plasma concentrations and safety. RESULTS: The overall number of participants enrolled was 192, with a mean (standard deviation) amyloid PET load at baseline of 101.80 (29.80) centiloids. At the time of early study termination by sponsor, 149 participants had valid Week 52 amyloid PET data (primary endpoint), and 12 participants had an early termination PET within the pre-defined time range of Week 104. The mean change in amyloid PET from baseline to Week 52 and Week 104 was -26.19 centiloids (range: -75.6-15.8; n=149) and -35.48 centiloids (range: -63.2--7.0; n=12), respectively. Responses to the home administration questionnaire at Week 52 (n=148) indicated that the majority of care partners (88-97%) considered administration of study drug at home easy (30.4%) or very easy (57.4%), and convenient (25.7%) or very convenient (70.9%). Care partners felt confident (31.1%) or very confident (62.2%) and satisfied (29.7%) or very satisfied (64.9%) with giving the injection at home. Responses by care partners at Week 36 (n=72), Week 76 (n=126) and Week 104 (n=29) and participant (patient) assessment of convenience and satisfaction at these time points were similar. There were no new safety findings associated with gantenerumab administered subcutaneously once weekly at 255 mg or safety issues associated with at-home injections by non-healthcare professional care partners. CONCLUSIONS: Once-weekly subcutaneous home administration of the anti-amyloid-beta antibody gantenerumab by non-healthcare-professional care partners to participants with early Alzheimer's disease was feasible, safe, well tolerated, and considered as a convenient option by both the care partners and participants with Alzheimer's disease. Although gantenerumab's development has been stopped due to lack of efficacy, this approach has the potential to reduce the frequency of hospital/outpatient clinic visits required for treatment with other anti-amyloid-ß antibodies and can increase flexibility of drug administration for people living with Alzheimer's disease and their families.

Antibody engagement with amyloid-beta does not inhibit [11C]PiB binding for PET imaging.

The elimination of amyloid-beta (Aß) plaques in Alzheimer's disease patients after treatment with anti-Aß antibodies such as lecanemab and aducanumab is supported by a substantially decreased signal in amyloid positron emission tomography (PET) imaging. However, this decreased PET signal has not been matched by a similar substantial effect on cognitive function. There may be several reasons for this, including short treatment duration and advanced disease stages among the patients. However, one aspect that has not been investigated, and the subject of this study, is whether antibody engagement with amyloid plaques inhibits the binding of amyloid-PET ligands, leading to a false impression of Aß removal from the brain. In the present study, tg-ArcSwe mice received three injections of RmAb158, the murine version of lecanemab or phosphate-buffered saline (PBS) before the administration of the amyloid-PET radioligand [11C]PiB, followed by isolation of brain tissue. Autoradiography showed that RmAb158- and PBS-treated mice displayed similar [11C]PiB binding. Moreover, the total Aß1-40 levels, representing the major Aß species of plaques in the tg-ArcSwe model, as well as soluble triggering receptor on myeloid cells 2 (sTREM2) levels, were similar in both groups. Interestingly, the concentration of soluble Aß aggregates was decreased in the RmAb158-treated group, along with a small but significant decrease in the total Aß1-42 levels. In conclusion, this study indicates that the binding of [11C]PiB to Aß accurately mirrors the load of Aß plaques in the brain, aligning with how amyloid-PET is interpreted in clinical studies of anti-Aß antibodies. However, early treatment effects on soluble Aß aggregates and Aß1-42 levels were not detected.

Beta amyloid PET scans for dementia diagnoses: Practice and research implications from CARE-IDEAS.

Beta amyloid PET scans are a minimally invasive biomarker that may inform Alzheimer's disease (AD) diagnosis. The Caregiver's Reactions and Experience (CARE) study, an IDEAS supplement, aimed to understand experiences of PET scan recipients and their care partners regarding motivations for scans, reporting and interpreting results, and impact of results. Patients with mild cognitive impairment or dementia who agreed to join the CARE-IDEAS study and their care partners participated in a baseline survey and follow-up survey approximately 18 months later, supplemented by in-depth qualitative interviews with subsets of participants. Patients who received scans and volunteered for follow-up research were more likely to be male, better educated, and have higher income than the general population. Survey information was merged with Medicare data. This article integrates findings from several CARE-IDEAS publications and provides implications for practice and research. Although most participants accurately reported scan results, they were often confused about their meaning for prognosis. Some participants reported distress with results, but there were no significant changes in measured depression, burden, or economic strain over time. Many respondents desired more information about prognosis and supportive resources. Scan results were not differentially associated with changes in service use over time. Findings suggest a need for carefully designed and tested tools for clinicians to discuss risks and benefits of scans and their results, and resources to support patients and care partners in subsequent planning. Learning of scan results provides a point-of-contact that should be leveraged to facilitate shared decision-making and person-centered longitudinal AD care.

Molecular neuroimaging in dominantly inherited versus sporadic early-onset Alzheimer's disease.

Approximately 5% of Alzheimer's disease patients develop symptoms before age 65 (early-onset Alzheimer's disease), with either sporadic (sporadic early-onset Alzheimer's disease) or dominantly inherited (dominantly inherited Alzheimer's disease) presentations. Both sporadic early-onset Alzheimer's disease and dominantly inherited Alzheimer's disease are characterized by brain amyloid-ß accumulation, tau tangles, hypometabolism and neurodegeneration, but differences in topography and magnitude of these pathological changes are not fully elucidated. In this study, we directly compared patterns of amyloid-ß plaque deposition and glucose hypometabolism in sporadic early-onset Alzheimer's disease and dominantly inherited Alzheimer's disease individuals. Our analysis included 134 symptomatic sporadic early-onset Alzheimer's disease amyloid-Positron Emission Tomography (PET)-positive cases from the University of California, San Francisco, Alzheimer's Disease Research Center (mean ± SD age 59.7 ± 5.6 years), 89 symptomatic dominantly inherited Alzheimer's disease cases (age 45.8 ± 9.3 years) and 102 cognitively unimpaired non-mutation carriers from the Dominantly Inherited Alzheimer Network study (age 44.9 ± 9.2). Each group underwent clinical and cognitive examinations, 11C-labelled Pittsburgh Compound B-PET and structural MRI. 18F-Fluorodeoxyglucose-PET was also available for most participants. Positron Emission Tomography scans from both studies were uniformly processed to obtain a standardized uptake value ratio (PIB50-70 cerebellar grey reference and FDG30-60 pons reference) images. Statistical analyses included pairwise global and voxelwise group comparisons and group-independent component analyses. Analyses were performed also adjusting for covariates including age, sex, Mini-Mental State Examination, apolipoprotein ε4 status and average composite cortical of standardized uptake value ratio. Compared with dominantly inherited Alzheimer's disease, sporadic early-onset Alzheimer's disease participants were older at age of onset (mean ± SD, 54.8 ± 8.2 versus 41.9 ± 8.2, Cohen's d = 1.91), with more years of education (16.4 ± 2.8 versus 13.5 ± 3.2, d = 1) and more likely to be apolipoprotein ε4 carriers (54.6% ε4 versus 28.1%, Cramer's V = 0.26), but similar Mini-Mental State Examination (20.6 ± 6.1 versus 21.2 ± 7.4, d = 0.08). Sporadic early-onset Alzheimer's disease had higher global cortical Pittsburgh Compound B-PET binding (mean ± SD standardized uptake value ratio, 1.92 ± 0.29 versus 1.58 ± 0.44, d = 0.96) and greater global cortical 18F-fluorodeoxyglucose-PET hypometabolism (mean ± SD standardized uptake value ratio, 1.32 ± 0.1 versus 1.39 ± 0.19, d = 0.48) compared with dominantly inherited Alzheimer's disease. Fully adjusted comparisons demonstrated relatively higher Pittsburgh Compound B-PET standardized uptake value ratio in the medial occipital, thalami, basal ganglia and medial/dorsal frontal regions in dominantly inherited Alzheimer's disease versus sporadic early-onset Alzheimer's disease. Sporadic early-onset Alzheimer's disease showed relatively greater 18F-fluorodeoxyglucose-PET hypometabolism in Alzheimer's disease signature temporoparietal regions and caudate nuclei, whereas dominantly inherited Alzheimer's disease showed relatively greater hypometabolism in frontal white matter and pericentral regions. Independent component analyses largely replicated these findings by highlighting common and unique Pittsburgh Compound B-PET and 18F-fluorodeoxyglucose-PET binding patterns. In summary, our findings suggest both common and distinct patterns of amyloid and glucose hypometabolism in sporadic and dominantly inherited early-onset Alzheimer's disease.

Predicting amyloid-PET and clinical conversion in apolipoprotein E ε3/ε3 non-demented individuals with multidimensional factors.

The apolipoprotein E (APOE) ε4 is a well-established risk factor of amyloid-ß (Aß) in Alzheimer's disease (AD). However, because of the high prevalence of APOE ε3, there may be a large number of people with APOE ε3/ε3 who are non-demented and have Aß pathology. There are limited studies on assessing Aß status and clinical conversion in the APOE ε3/ε3 non-demented population. Two hundred and ninety-three non-demented individuals with APOE ε3/ε3 from ADNI database were divided into Aß-positron emission tomography (Aß-PET) positivity (+) and Aß-PET negativity (-) groups using cut-off value of >1.11. Stepwise regression searched for a single or multidimensional clinical variables for predicting Aß-PET (+), and the receiver operating characteristic curve (ROC) assessed the accuracy of the predictive models. The Cox regression model explored the risk factors associated with clinical conversion to mild cognitive impairment (MCI) or AD. The results showed that the combination of sex, education, ventricle and white matter hyperintensity (WMH) volume can accurately predict Aß-PET status in cognitively normal (CN), and the combination of everyday cognition study partner total (EcogSPTotal) score, age, plasma p-tau 181 and WMH can accurately predict Aß-PET status in MCI individuals. EcogSPTotal score were independent predictors of clinical conversion to MCI or AD. The findings may provide a non-invasive and effective tool to improve the efficiency of screening Aß-PET (+), accelerate and reduce costs of AD trial recruitment in future secondary prevention trials or help to select patients at high risk of disease progression in clinical trials.

Deep Learning-Driven Estimation of Centiloid Scales from Amyloid PET Images with 11C-PiB and 18F-Labeled Tracers in Alzheimer's Disease.

BACKGROUND: Standard methods for deriving Centiloid scales from amyloid PET images are time-consuming and require considerable expert knowledge. We aimed to develop a deep learning method of automating Centiloid scale calculations from amyloid PET images with 11C-Pittsburgh Compound-B (PiB) tracer and assess its applicability to 18F-labeled tracers without retraining. METHODS: We trained models on 231 11C-PiB amyloid PET images using a 50-layer 3D ResNet architecture. The models predicted the Centiloid scale, and accuracy was assessed using mean absolute error (MAE), linear regression analysis, and Bland-Altman plots. RESULTS: The MAEs for Alzheimer's disease (AD) and young controls (YC) were 8.54 and 2.61, respectively, using 11C-PiB, and 8.66 and 3.56, respectively, using 18F-NAV4694. The MAEs for AD and YC were higher with 18F-florbetaben (39.8 and 7.13, respectively) and 18F-florbetapir (40.5 and 12.4, respectively), and the error rate was moderate for 18F-flutemetamol (21.3 and 4.03, respectively). Linear regression yielded a slope of 1.00, intercept of 1.26, and R2 of 0.956, with a mean bias of -1.31 in the Centiloid scale prediction. CONCLUSIONS: We propose a deep learning means of directly predicting the Centiloid scale from amyloid PET images in a native space. Transferring the model trained on 11C-PiB directly to 18F-NAV4694 without retraining was feasible.

Alzheimer's Amyloid Hypothesis and Antibody Therapy: Melting Glaciers?

The amyloid cascade hypothesis for Alzheimer's disease is still alive, although heavily challenged. Effective anti-amyloid immunotherapy would confirm the hypothesis' claim that the protein amyloid-beta is the cause of the disease. Two antibodies, aducanumab and lecanemab, have been approved by the U.S. Food and Drug Administration, while a third, donanemab, is under review. The main argument for the FDA approvals is a presumed therapy-induced removal of cerebral amyloid deposits. Lecanemab and donanemab are also thought to cause some statistical delay in the determination of cognitive decline. However, clinical efficacy that is less than with conventional treatment, selection of amyloid-positive trial patients with non-specific amyloid-PET imaging, and uncertain therapy-induced removal of cerebral amyloids in clinical trials cast doubt on this anti-Alzheimer's antibody therapy and hence on the amyloid hypothesis, calling for a more thorough investigation of the negative impact of this type of therapy on the brain.

Combining Blood-Based Biomarkers and Structural MRI Measurements to Distinguish Persons with and without Significant Amyloid Plaques.

Background: Amyloid-ß (Aß) plaques play a pivotal role in Alzheimer's disease. The current positron emission tomography (PET) is expensive and limited in availability. In contrast, blood-based biomarkers (BBBMs) show potential for characterizing Aß plaques more affordably. We have previously proposed an MRI-based hippocampal morphometry measure to be an indicator of Aß plaques. Objective: To develop and validate an integrated model to predict brain amyloid PET positivity combining MRI feature and plasma Aß42/40 ratio. Methods: We extracted hippocampal multivariate morphometry statistics from MR images and together with plasma Aß42/40 trained a random forest classifier to perform a binary classification of participant brain amyloid PET positivity. We evaluated the model performance using two distinct cohorts, one from the Alzheimer's Disease Neuroimaging Initiative (ADNI) and the other from the Banner Alzheimer's Institute (BAI), including prediction accuracy, precision, recall rate, F1 score, and AUC score. Results: Results from ADNI (mean age 72.6, Aß+ rate 49.5%) and BAI (mean age 66.2, Aß+ rate 36.9%) datasets revealed the integrated multimodal (IMM) model's superior performance over unimodal models. The IMM model achieved prediction accuracies of 0.86 in ADNI and 0.92 in BAI, surpassing unimodal models based solely on structural MRI (0.81 and 0.87) or plasma Aß42/40 (0.73 and 0.81) predictors. CONCLUSIONS: Our IMM model, combining MRI and BBBM data, offers a highly accurate approach to predict brain amyloid PET positivity. This innovative multiplex biomarker strategy presents an accessible and cost-effective avenue for advancing Alzheimer's disease diagnostics, leveraging diverse pathologic features related to Aß plaques and structural MRI.

Amyloid brain-dedicated PET images can diagnose Alzheimer's pathology with Centiloid Scale.

PURPOSE: To evaluate whether the Centiloid Scale may be used to diagnose Alzheimer's Disease (AD) pathology effectively with the only use of amyloid PET imaging modality from a brain-dedicated PET scanner. METHODS: This study included 26 patients with amyloid PET images with 3 different radiotracers. All patients were acquired both on a PET/CT and a brain-dedicated PET scanner (CareMiBrain, CMB), from which 4 different reconstructions were implemented. A new pipeline was proposed and used for the PET image analysis based on the original Centiloid Scale processing pipeline, but with only PET images. The Youden's Index was employed to calculate the optimal cutoffs for diagnosis and evaluated by the AUC, accuracy, precision, and recall metrics. RESULTS: The Centiloid Scale (CL) processing pipeline was validated with and without the use of MR images. The CL cutoffs for AD pathology diagnosis on the PET/CT and the 4 CMB reconstructions were 34.4 ±â€¯2.2, 43.5 ±â€¯3.5, 51.9 ±â€¯12.5, 57.5 ±â€¯6.8 and 41.8 ±â€¯1.2 respectively. Overall, for these cutoffs all metrics obtained the maximum score. CONCLUSION: The Centiloid scale applied to PET images allows for AD pathology diagnosis. The CMB scanner can be used with the Centiloid scale to automatically assist in the diagnosis of AD pathology, relieving the large burden of neurodegenerative diseases on a traditional PET/CT.

Impaired Glymphatic Flow on Diffusion Tensor MRI as a Marker of Neurodegeneration in Alzheimer's Disease: Correlation with Gray Matter Volume Loss and Cognitive Decline Independent of Cerebral Amyloid Deposition.

Background: Impaired glymphatic flow on the Alzheimer's disease (AD) spectrum may be evaluated using diffusion tensor image analysis along the perivascular space (DTI-ALPS). Objective: We aimed to validate impaired glymphatic flow and explore its association with gray matter volume, cognitive status, and cerebral amyloid deposition on the AD spectrum. Methods: 80 participants (mean age, 76.9±8.5 years; 57 women) with AD (n = 65) and cognitively normal (CN) (n = 15) who underwent 3T brain MRI including DTI and/or amyloid PET were included. After adjusting for age, sex, apolipoprotein E status, and burden of white matter hyperintensities, the ALPS-index was compared according to the AD spectrum. The association between the ALPS-index and gray matter volume, cognitive status, and quantitative amyloid from PET was assessed. Results: The ALPS-index in the AD was significantly lower (mean, 1.476; 95% CI, 1.395-1.556) than in the CN (1.784;1.615-1.952; p = 0.026). Volumes of the entorhinal cortex, hippocampus, temporal pole, and primary motor cortex showed significant associations with the ALPS-index (all, p < 0.05). There was a positive correlation between the ALPS-index and MMSE score (partial r = 0.435; p < 0.001), but there was no significant correlation between the ALPS-index and amyloid SUVRs (all, p > 0.05). Conclusions: Decreased glymphatic flow measured by DTI-ALPS in AD may serve as a marker of neurodegeneration correlating with structural atrophy and cognitive decline.

Characterizing brain tau and cognitive decline along the amyloid timeline in Alzheimer's disease.

Recent longitudinal PET imaging studies have established methods to estimate the age at which amyloid becomes abnormal at the level of the individual. Here we recontextualized amyloid levels into the temporal domain to better understand the downstream Alzheimer's disease processes of tau neurofibrillary tangle (NFT) accumulation and cognitive decline. This cohort study included a total of 601 individuals from the Wisconsin Registry for Alzheimer's Prevention and Wisconsin Alzheimer's Disease Research Center that underwent amyloid and tau PET, longitudinal neuropsychological assessments and met clinical criteria for three clinical diagnosis groups: cognitively unimpaired (n = 537); mild cognitive impairment (n = 48); or dementia (n = 16). Cortical 11C-Pittsburgh compound B (PiB) distribution volume ratio (DVR) and sampled iterative local approximation were used to estimate amyloid positive (A+; global PiB DVR > 1.16 equivalent to 17.1 centiloids) onset age and years of A+ duration at tau PET (i.e. amyloid chronicity). Tau PET burden was quantified using 18F-MK-6240 standardized uptake value ratios (70-90 min, inferior cerebellar grey matter reference region). Whole-brain and region-specific approaches were used to examine tau PET binding along the amyloid timeline and across the Alzheimer's disease clinical continuum. Voxel-wise 18F-MK-6240 analyses revealed that with each decade of A+, the spatial extent of measurable tau spread (i.e. progressed) from regions associated with early to late NFT tau stages. Regional analyses indicated that tau burden in the entorhinal cortex was detectable, on average, within 10 years of A+ onset. Additionally, the entorhinal cortex was the region most sensitive to early amyloid pathology and clinical impairment in this predominantly preclinical sample. Among initially cognitively unimpaired (n = 472) individuals with longitudinal cognitive follow-up, mixed effects models showed significant linear and non-linear interactions of A+ duration and entorhinal tau on cognitive decline, suggesting a synergistic effect whereby greater A+ duration, together with a higher entorhinal tau burden, increases the likelihood of cognitive decline beyond their separable effects. Overall, the amyloid time framework enabled a spatiotemporal characterization of tau deposition patterns across the Alzheimer's disease continuum. This approach, which examined cross-sectional tau PET data along the amyloid timeline to make longitudinal disease course inferences, demonstrated that A+ duration explains a considerable amount of variability in the magnitude and topography of tau spread, which largely recapitulated NFT staging observed in human neuropathological studies. By anchoring disease progression to the onset of amyloid, this study provides a temporal disease context, which may help inform disease prognosis and timing windows for anti-amyloid therapies.

Expression of regional brain amyloid-ß deposition with [18F]Flutemetamol in Centiloid scale -a multi-site study.

PURPOSE: The Centiloid project helps calibrate the quantitative amyloid-ß (Aß) load into a unified Centiloid (CL) scale that allows data comparison across multi-site. How the smaller regional amyloid converted into CL has not been attempted. We first aimed to express regional Aß deposition in CL using [18F]Flutemetamol and evaluate regional Aß deposition in CL with that in standardized uptake value ratio (SUVr). Second, we aimed to determine the presence or absence of focal Aß deposition by measuring regional CL in equivocal cases showing negative global CL. METHODS: Following the Centiloid project pipeline, Level-1 replication, Level-2 calibration, and quality control were completed to generate corresponding Centiloid conversion equations to convert SUVr into Centiloid at regional levels. In equivocal cases, the regional CL was compared with visual inspection to evaluate regional Aß positivity. RESULTS: 14 out of 16 regional conversions from [18F]Flutemetamol SUVr to Centiloid successfully passed the quality control, showing good reliability and relative variance, especially precuneus/posterior cingulate and prefrontal regions with good stability for Centiloid scaling. The absence of focal Aß deposition could be detected by measuring regional CL, showing a high agreement rate with visual inspection. The regional Aß positivity in the bilateral anterior cingulate cortex was most prevalent in equivocal cases. CONCLUSION: The expression of regional brain Aß deposition in CL with [18F]Flutemetamol has been attempted in this study. Equivocal cases had focal Aß deposition that can be detected by measuring regional CL.

Human in vivo evidence of associations between herpes simplex virus and cerebral amyloid-beta load in normal aging.

BACKGROUND: Mounting data suggests that herpes simplex virus type 1 (HSV-1) is involved in the pathogenesis of AD, possibly instigating amyloid-beta (Aß) accumulation decades before the onset of clinical symptoms. However, human in vivo evidence linking HSV-1 infection to AD pathology is lacking in normal aging, which may contribute to the elucidation of the role of HSV-1 infection as a potential AD risk factor. METHODS: To shed light into this question, serum anti-HSV IgG levels were correlated with 18F-Florbetaben-PET binding to Aß deposits and blood markers of neurodegeneration (pTau181 and neurofilament light chain) in cognitively normal older adults. Additionally, we investigated whether associations between anti-HSV IgG and AD markers were more evident in APOE4 carriers. RESULTS: We showed that increased anti-HSV IgG levels are associated with higher Aß load in fronto-temporal regions of cognitively normal older adults. Remarkably, these cortical regions exhibited abnormal patterns of resting state-functional connectivity (rs-FC) only in those individuals showing the highest levels of anti-HSV IgG. We further found that positive relationships between anti-HSV IgG levels and Aß load, particularly in the anterior cingulate cortex, are moderated by the APOE4 genotype, the strongest genetic risk factor for AD. Importantly, anti-HSV IgG levels were unrelated to either subclinical cognitive deficits or to blood markers of neurodegeneration. CONCLUSIONS: All together, these results suggest that HSV infection is selectively related to cortical Aß deposition in normal aging, supporting the inclusion of cognitively normal older adults in prospective trials of antimicrobial therapy aimed at decreasing the AD risk in the aging population.