18F-AV-1451 PET Imaging in Three Patients with Probable Cerebral Amyloid Angiopathy

Cerebral Amyloid Angiopathy and Downstream Alzheimer Disease Plasma Biomarkers

Importance

As amyloid-targeted therapies have become commercially available, the monitoring of cerebral amyloid angiopathy (CAA), which is an important risk factor for amyloid-related imaging abnormalities, has received increasing attention. However, comprehensive evidence on the association between Alzheimer disease (AD) plasma biomarkers and various CAA imaging markers is still lacking.

Objective

To examine the association of CAA imaging markers with downstream AD plasma biomarkers in relation to amyloid-β (Aβ) uptake on positron emission tomography (PET) and whether their interplay is associated with cognitive changes.

Design, Setting, and Participants

This registry-based cohort study in 25 hospitals across South Korea recruited participants aged 45 years or older who were registered between January 1, 2016, and December 31, 2023. Participants were categorized as having no cognitive impairment, mild cognitive impairment, or dementia of the Alzheimer type.

Exposures

Cerebral amyloid angiopathy imaging markers assessed by magnetic resonance imaging, including cerebral microbleeds (CMBs), cortical superficial siderosis, white matter hyperintensities, lacunes, and enlarged perivascular spaces.

Main Outcomes and Measures

Plasma phosphorylated tau-217 (p-tau217) was measured using a commercial assay. Glial fibrillary acidic protein (GFAP) and neurofilament light chain (NfL) were measured using a single-molecule assay on a single platform. All participants underwent amyloid PET imaging. Associations of CAA and vascular imaging markers with downstream AD plasma biomarkers were investigated using linear regression.

Results

A total of 1708 participants were included (mean [SD] age, 71.2 [8.4] years; 1044 female [61.1%]). The mean (SD) follow-up period was 4.3 (3.1) years. Lobar CMB counts and the presence of CAA were associated with downstream AD plasma biomarkers, including p-tau217 (β = 0.12 [95% CI, 0.05-0.18] and 0.29 [95% CI, 0.12-0.47], respectively), GFAP (β = 0.07 [95% CI, 0.03-0.12] and 0.20 [95% CI, 0.09-0.31], respectively), and NfL (β = 0.07 [95% CI, 0.03-0.11] and 0.16 [95% CI, 0.06-0.25], respectively) with and without the mediation of Aβ uptake on PET (indirect effect: lobar CMBs-p-tau217, 59.8% [β = 0.07 (95% CI, 0.03-0.11)]; lobar CMBs-GFAP, 49.3% [β = 0.04 (95% CI, 0.01-0.06)]; lobar CMBs-NfL, 20.9% [β = 0.01 (95% CI, 0.01-0.03)]; CAA-p-tau217, 50.9% [β = 0.15 (95% CI, 0.06-0.24)]; CAA-GFAP, 39.2% [β = 0.08 (95% CI, 0.03-0.13)]; CAA-NfL, 19.2% [β = 0.03 (95% CI, 0.01-0.05)]). Amyloid-β uptake fully mediated the associations between cortical superficial siderosis and downstream AD plasma markers. In contrast, hypertensive arteriosclerotic vascular imaging markers, including lacunes, deep CMBs, and enlarged perivascular spaces in basal ganglia, were associated with only NfL levels (β = 0.07 [95% CI, 0.01-0.13], 0.20 [95% CI, 0.08-0.32], and 0.14 [95% CI, 0.06-0.23], respectively), regardless of Aβ uptake on PET. Finally, there were interactive associations of lobar CMBs in conjunction with p-tau217 levels (β = -0.56 [95% CI, -0.79 to -0.34]) and GFAP levels (β = -0.44 [95% CI, -0.70 to -0.17]) with annual Mini-Mental State Examination changes.

Conclusions and Relevance

In this cohort study of participants with no cognitive impairment, mild cognitive impairment, or dementia of the Alzheimer type, a novel association was found among CAA imaging markers, downstream AD plasma biomarkers, and cognitive declines in relation to brain Aβ burdens. The findings emphasize the importance of understanding the clinical effects of amyloid-related imaging abnormality-like CAA imaging markers in light of upcoming amyloid-targeted therapies.

Dual-Phase C-11 PiB PET Images for Detecting Tau Pathology in Cerebral Amyloid Angiopathy

BACKGROUND

Cerebral amyloid angiopathy (CAA) is a major cause of lobar intracerebral hemorrhage and cognitive dysfunction in the elderly, and frequently coexists with Alzheimer's disease and tau pathology. Dual-phase 11C-PiB PET detects amyloid deposition and cerebral perfusion changes and may have diagnostic value for identifying tau in CAA.

METHODS

We prospectively enrolled patients with probable CAA for dynamic PiB and AV1451 scans. We compared early-phase (0-6 min after tracer injection) and late-phase (40-70 min) PiB PET between the tau(+) and tau(-) groups (based on AV1451 PET) and investigated their diagnostic values for detecting tau.

RESULTS

CAA/tau(+) had lower early-phase temporal PiB uptake than CAA/tau(-) (p = 0.014) and higher late-phase uptake in the whole cortex and temporal and parietal lobes (all p < 0.05). Early-phase temporal PiB SUVR correlated with tau burden (r = -0.34, p = 0.038). Using Youden's cut-off, early-phase and late-phase PET had sensitivities of 55% and 80% and specificities of 85% and 65% for detecting tau, respectively. Combining early- and late-phase scans provided a rule-out sensitivity of 90% and rule-in specificity of 100% for tau pathology in CAA.

CONCLUSIONS

Dual-phase 11C-PiB PET represents a reliable approach for assessing tau and could potentially identify CAA patients for tau biomarker testing.

Neuroimaging in Dementia

OBJECTIVE

This article captures the current literature regarding the use of neuroimaging measures to study neurodegenerative diseases, including early- and late-onset Alzheimer disease, vascular cognitive impairment, frontotemporal lobar degeneration disorders, dementia with Lewy bodies, and Parkinson disease dementia. In particular, the article highlights significant recent changes in novel therapeutics now available for the treatment of Alzheimer disease and in defining neurodegenerative disease using biological frameworks. Studies summarized include those using structural and functional MRI (fMRI) techniques, as well as metabolic and molecular emission tomography imaging (ie, positron emission tomography [PET] and single-photon emission computerized tomography [SPECT]).

LATEST DEVELOPMENTS

Neuroimaging measures are considered essential biomarkers for the detection and diagnosis of most neurodegenerative diseases. The recent approval of anti-amyloid antibody therapies has highlighted the importance of MRI and PET techniques in treatment eligibility and monitoring for associated side effects. Given the success of the initial biomarker-based classification system for Alzheimer disease (the amyloid, tau, neurodegeneration [A/T/N] framework), researchers in vascular cognitive impairment have created similar techniques for biomarker-based diagnosis. Further, the A/T/N framework for Alzheimer disease has been updated to include several pathologic targets for biomarker detection.

ESSENTIAL POINTS

Neurodegenerative diseases have a major health impact on millions of patients around the world. Neuroimaging biomarkers are rapidly becoming major diagnostic tools for the detection, monitoring, and treatment of neurodegenerative diseases. This article educates readers about the current literature surrounding the use of neuroimaging tools in neurodegenerative diseases along with recent important developments in the field.

Cerebral tau pathology in cerebral amyloid angiopathy

Tau, a hallmark of Alzheimer's disease, is poorly characterized in cerebral amyloid angiopathy. We aimed to assess the clinico-radiological correlations between tau positron emission tomography scans and cerebral amyloid angiopathy. We assessed cerebral amyloid and hyperphosphorylated tau in patients with probable cerebral amyloid angiopathy (n = 31) and hypertensive small vessel disease (n = 27) using 11C-Pittsburgh compound B and 18F-T807 positron emission tomography. Multivariable regression models were employed to assess radio-clinical features related to cerebral tau pathology in cerebral amyloid angiopathy. Cerebral amyloid angiopathy exhibited a higher cerebral tau burden in the inferior temporal lobe [1.25 (1.17-1.42) versus 1.08 (1.05-1.22), P < 0.001] and all Braak stage regions of interest (P < 0.05) than hypertensive small vessel disease, although the differences were attenuated after age adjustment. Cerebral tau pathology was significantly associated with cerebral amyloid angiopathy-related vascular markers, including cortical superficial siderosis (β = 0.12, 95% confidence interval 0.04-0.21) and cerebral amyloid angiopathy score (β = 0.12, 95% confidence interval 0.03-0.21) after adjustment for age, ApoE4 status and whole cortex amyloid load. Tau pathology correlated significantly with cognitive score (Spearman's ρ=-0.56, P = 0.001) and hippocampal volume (-0.49, P = 0.007), even after adjustment. In conclusion, tau pathology is more frequent in sporadic cerebral amyloid angiopathy than in hypertensive small vessel disease. Cerebral amyloid angiopathy-related vascular pathologies, especially cortical superficial siderosis, are potential markers of cerebral tau pathology suggestive of concomitant Alzheimer's disease.

A review of the flortaucipir literature for positron emission tomography imaging of tau neurofibrillary tangles

Alzheimer's disease is defined by the presence of β-amyloid plaques and neurofibrillary tau tangles potentially preceding clinical symptoms by many years. Previously only detectable post-mortem, these pathological hallmarks are now identifiable using biomarkers, permitting an in vivo definitive diagnosis of Alzheimer's disease. 18F-flortaucipir (previously known as 18F-T807; 18F-AV-1451) was the first tau positron emission tomography tracer to be introduced and is the only Food and Drug Administration-approved tau positron emission tomography tracer (Tauvid™). It has been widely adopted and validated in a number of independent research and clinical settings. In this review, we present an overview of the published literature on flortaucipir for positron emission tomography imaging of neurofibrillary tau tangles. We considered all accessible peer-reviewed literature pertaining to flortaucipir through 30 April 2022. We found 474 relevant peer-reviewed publications, which were organized into the following categories based on their primary focus: typical Alzheimer's disease, mild cognitive impairment and pre-symptomatic populations; atypical Alzheimer's disease; non-Alzheimer's disease neurodegenerative conditions; head-to-head comparisons with other Tau positron emission tomography tracers; and technical considerations. The available flortaucipir literature provides substantial evidence for the use of this positron emission tomography tracer in assessing neurofibrillary tau tangles in Alzheimer's disease and limited support for its use in other neurodegenerative disorders. Visual interpretation and quantitation approaches, although heterogeneous, mostly converge and demonstrate the high diagnostic and prognostic value of flortaucipir in Alzheimer's disease.

Neuroimaging in Dementia

OBJECTIVE

Neurodegenerative diseases are significant health concerns with regard to morbidity and social and economic hardship around the world. This review describes the state of the field of neuroimaging measures as biomarkers for detection and diagnosis of both slowly progressing and rapidly progressing neurodegenerative diseases, specifically Alzheimer disease, vascular cognitive impairment, dementia with Lewy bodies or Parkinson disease dementia, frontotemporal lobar degeneration spectrum disorders, and prion-related diseases. It briefly discusses findings in these diseases in studies using MRI and metabolic and molecular-based imaging (eg, positron emission tomography [PET] and single-photon emission computerized tomography [SPECT]).

LATEST DEVELOPMENTS

Neuroimaging studies with MRI and PET have demonstrated differential patterns of brain atrophy and hypometabolism in different neurodegenerative disorders, which can be useful in differential diagnoses. Advanced MRI sequences, such as diffusion-based imaging, and functional MRI (fMRI) provide important information about underlying biological changes in dementia and new directions for development of novel measures for future clinical use. Finally, advancements in molecular imaging allow clinicians and researchers to visualize dementia-related proteinopathies and neurotransmitter levels.

ESSENTIAL POINTS

Diagnosis of neurodegenerative diseases is primarily based on symptomatology, although the development of in vivo neuroimaging and fluid biomarkers is changing the scope of clinical diagnosis, as well as the research into these devastating diseases. This article will help inform the reader about the current state of neuroimaging in neurodegenerative diseases, as well as how these tools might be used for differential diagnoses.

Amyloid and tau PET in cerebral amyloid angiopathy-related inflammation two case reports and literature review

Background

Cerebral amyloid angiopathy-related inflammation (CAA-ri) is a clinical syndrome characterized by MRI findings of amyloid-related imaging abnormalities-edema (ARIA-E) suggestive of autoimmune and inflammatory reaction and hemorrhagic evidence of cerebral amyloid angiopathy. The longitudinal variation of amyloid PET and its imaging association with CAA-ri are undetermined. Moreover, tau PET in CAA-ri has been rarely investigated.

Method

We retrospectively described two cases of CAA-ri. We provided the temporal change of amyloid and tau PET in the first case, and the cross-sectional finding of amyloid and tau PET in the second case. We also performed a literature review of the imaging features of amyloid PET in reported cases of CAA-ri.

Results

In the first case, an 88-year-old male presented with progressive consciousness and gait disturbances over 2 months. MRI showed disseminated cortical superficial siderosis. Amyloid PET prior to and after the CAA-ri revealed focally decreased amyloid load in the region of ARIA-E. In the second case, a 72-year-old male was initially suspected to have central nervous system cryptococcosis but later diagnosed with CAA-ri because of the characteristic MRI features and good response to corticosteroid treatment; a subsequent amyloid scan revealed positive amyloid deposition of the brain. Neither case suggested an association between the region of ARIA-E and higher amyloid uptake on PET before or after onset of CAA-ri. Our literature review revealed variable findings related to amyloid burden in post-inflammatory regions in previously reported CAA-ri cases with available amyloid PET. Our case is the first report of longitudinal changes on amyloid PET and show focal decreases in amyloid load after the inflammatory process.

Conclusion

This case series highlights the need to better explore the potential of longitudinal amyloid PET in the understanding of the mechanisms of CAA-ri.

Recurrent Lobar Hemorrhages and Multiple Cortical Superficial Siderosis in a Patient of Alzheimer's Disease With Homozygous APOE ε2 Allele Presenting Hypobetalipoproteinemia and Pathological Findings of 18F-THK5351 Positron Emission Tomography: A Case Report

In Alzheimer's disease, the apolipoprotein E gene (APOE) ε2 allele is a protective genetic factor, whereas the APOE ε4 allele is a genetic risk factor. However, both the APOE ε2 and the APOE ε4 alleles are genetic risk factors for lobar intracerebral hemorrhage. The reasons for the high prevalence of lobar intracerebral hemorrhage and the low prevalence of Alzheimer's disease with the APOE ε2 allele remains unknown. Here, we describe the case of a 79-year-old Japanese female with Alzheimer's disease, homozygous for the APOE ε2 allele. This patient presented with recurrent lobar hemorrhages and multiple cortical superficial siderosis. The findings on the ¹¹C-labeled Pittsburgh Compound B-positron emission tomography (PET) were characteristic of Alzheimer's disease. ¹⁸F-THK5351 PET revealed that the accumulation of ¹⁸F-THK 5351 in the right pyramidal tract at the pontine level, the cerebral peduncle of the midbrain, and the internal capsule, reflecting the lesions of the previous lobar intracerebral hemorrhage in the right frontal lobe. Moreover, ¹⁸F-THK5351 accumulated in the bilateral globus pallidum, amygdala, caudate nuclei, and the substantia nigra of the midbrain, which were probably off-target reaction, by binding to monoamine oxidase B (MAO-B). ¹⁸F-THK5351 were also detected in the periphery of prior lobar hemorrhages and a cortical subarachnoid hemorrhage, as well as in some, but not all, areas affected by cortical siderosis. Besides, ¹⁸F-THK5351 retentions were observed in the bilateral medial temporal cortices and several cortical areas without cerebral amyloid angiopathy or prior hemorrhages, possibly where tau might accumulate. This is the first report of a patient with Alzheimer's disease, carrying homozygous APOE ε2 allele and presenting with recurrent lobar hemorrhages, multiple cortical superficial siderosis, and immunohistochemically vascular amyloid β. The ¹⁸F-THK5351 PET findings suggested MAO-B concentrated regions, astroglial activation, Waller degeneration of the pyramidal tract, neuroinflammation due to CAA related hemorrhages, and possible tau accumulation.

Association of Memory Impairment With Concomitant Tau Pathology in Patients With Cerebral Amyloid Angiopathy

OBJECTIVE

Relying on tau-PET imaging, this cross-sectional study explored whether memory impairment is linked to the presence of concomitant tau pathology in individuals with cerebral amyloid angiopathy (CAA).

METHODS

Forty-six patients with probable CAA underwent a neuropsychological examination and an MRI for quantification of structural markers of cerebral small vessel disease. A subset of these participants also completed a [¹¹C]-Pittsburgh compound B (n = 39) and [¹⁸F]-flortaucipir (n = 40) PET for in vivo estimation of amyloid and tau burden, respectively. Participants were classified as amnestic or nonamnestic on the basis of neuropsychological performance. Statistical analyses were performed to examine differences in cognition, structural markers of cerebral small vessel disease, and amyloid- and tau-PET retention between participants with amnestic and those with nonamnestic CAA.

RESULTS

Patients with probable CAA with an amnestic presentation displayed a globally more severe profile of cognitive impairment, smaller hippocampal volume (p < 0.001), and increased tau-PET binding in regions susceptible to Alzheimer disease neurodegeneration (p = 0.003) compared to their nonamnestic counterparts. Amnestic and nonamnestic patients with CAA did not differ on any other MRI markers or on amyloid-PET binding. In a generalized linear model including all evaluated neuroimaging markers, tau-PET retention (β = -0.85, p = 0.001) and hippocampal volume (β = 0.64 p = 0.01) were the only significant predictors of memory performance. The cognitive profile of patients with CAA with an elevated tau-PET retention was distinctly characterized by a significantly lower performance on the memory domain (p = 0.004).

CONCLUSIONS

These results suggest that the presence of objective memory impairment in patients with probable CAA could serve as a marker for underlying tau pathology.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that tau-PET retention is related to the presence of objective memory impairment in patients with CAA.

Tau reduction in aged mice does not impact Microangiopathy

Microangiopathy, including proliferation of small diameter capillaries, increasing vessel tortuosity, and increased capillary blockage by leukocytes, was previously observed in the aged rTg4510 mouse model. Similar gene expression changes related to angiogenesis were observed in both rTg4510 and Alzheimer's disease (AD). It is uncertain if tau is directly responsible for these vascular changes by interacting directly with microvessels, and/or if it contributes indirectly via neurodegeneration and concurrent neuronal loss and inflammation. To better understand the nature of tau-related microangiopathy in human AD and in tau mice, we isolated capillaries and observed that bioactive soluble tau protein could be readily detected in association with vasculature. To examine whether this soluble tau is directly responsible for the microangiopathic changes, we made use of the tetracycline-repressible gene expression cassette in the rTg4510 mouse model and measured vascular pathology following tau reduction. These data suggest that reduction of tau is insufficient to alter established microvascular complications including morphological alterations, enhanced expression of inflammatory genes involved in leukocyte adherence, and blood brain barrier compromise. These data imply that 1) soluble bioactive tau surprisingly accumulates at the blood brain barrier in human brain and in mouse models, and 2) the morphological and molecular phenotype of microvascular disturbance does not resolve with reduction of whole brain soluble tau. Additional consideration of vascular-directed therapies and strategies that target tau in the vascular space may be required to restore normal function in neurodegenerative disease.

The preclinical amyloid sensitive composite to determine subtle cognitive differences in preclinical Alzheimer's disease

Recently, the focus of Alzheimer's disease (AD) research has shifted from the clinical stage to the preclinical stage. We, therefore, aimed to develop a cognitive composite score that can detect the subtle cognitive differences between the amyloid positive (Aβ+) and negative (Aβ-) status in cognitively normal (CN) participants. A total of 423 CN participants with Aβ positron emission tomography images were recruited. The multiple-indicators multiple-causes model found the latent mean difference between the Aβ+ and Aβ- groups in the domains of verbal memory, visual memory, and executive functions. The multivariate analysis of covariance (MANCOVA) showed that the Aβ+ group performed worse in tests related to the verbal and visual delayed recall, semantic verbal fluency, and inhibition of cognitive inference within the three cognitive domains. The Preclinical Amyloid Sensitive Composite (PASC) model we developed using the result of MANCOVA and the MMSE presented a good fit with the data. The accuracy of the PASC score when applied with age, sex, education, and APOE ε4 for distinguishing between Aβ+ and Aβ- was adequate (AUC = 0.764; 95% CI = 0.667-0.860) in the external validation set (N = 179). We conclude that the PASC can eventually contribute to facilitating more prevention trials in preclinical AD.

Cerebral Microhemorrhage at MRI in Mild Cognitive Impairment and Early Alzheimer Disease: Association with Tau and Amyloid β at PET Imaging

Background Growing evidence indicates an association between cerebral microhemorrhages (MHs) and amyloid β accumulation in Alzheimer disease (AD), but to the knowledge of the authors the association with tau burden is unknown. Purpose To investigate the association between cerebral MH load and tau pathologic structure measured in healthy older individuals and individuals along the AD spectrum, stratified by using the A (amyloid β)/T (tau)/N (neurodegeneration) biomarker classification system. Materials and methods In this prospective cohort study, participants from the AD Neuroimaging Initiative were included (healthy control participants, participants with mild cognitive impairment, and participants with AD dementia; data from October 2005 to January 2019). T2*-weighted gradient-echo MRI was performed to quantify MH, fluorine 18 (¹⁸F) flortaucipir (AV-1451) PET was performed to quantify tau, and ¹⁸F-florbetaben/¹⁸F- florbetapir (AV45) PET was performed to quantify amyloid β to study associations of MH with regional and global tau and amyloid β load. Associations with cerebrospinal fluid (CSF) biomarkers (amyloid β1-42, total tau, phosphorylated tau 181) were also assessed. Analysis of covariance and Spearman rank correlation test for cross-sectional analysis and Wilcoxon signed rank test for longitudinal analyses were used, controlling for multiple comparisons (Bonferroni significance threshold, P < .008). Results Evaluated were 343 participants (mean age, 75 years ± 7; 186 women), including 205 participants who were A-TN- (mean age, 73 years ± 7; 115 women), 80 participants who were A+TN- (mean age, 76 years ± 7; 38 women), and 58 participants who were A+TN+ (mean age, 77 ± 8; 34 women). MH count was associated with global (Spearman ρ = 0.27; P = .004) and frontal (ρ = 0.27; P = .005) amyloid β load and global tau load (ρ = 0.31; P = .001). In a longitudinal analysis, MH count increased significantly over approximately 5 years in the entire cohort (T-1, 81 [range, 0-6 participants]; T0, 214 [range, 0-58 participants]; P < .001), in A+TN+ (T-1, 20 [range, 0-5 participants]; T0, 119 [range, 1-58 participants]; P < .001), A+TN- (T-1, 31 [range, 0-6 participants]; T0, 43 [range, 0-8 participants]; P = .03), and A-TN- (T-1, 30 [range, 0-4 participants]; T0, 52 [range, 0-6 participants]; P = .007). A higher MH count was associated with higher future global (ρ = 0.29; P = .008) and parietal (ρ = 0.31; P = .005) amyloid β and parietal tau load (ρ = 0.31; P = .005). Conclusion Cerebral microhemorrhage load is associated spatially with tau accumulation, both cross-sectionally and longitudinally. © RSNA, 2020 Online supplemental material is available for this article.

A Nomogram for Predicting Amyloid PET Positivity in Amnestic Mild Cognitive Impairment

BACKGROUND

Most clinical trials focus on amyloid-β positive (Aβ+) amnestic mild cognitive impairment (aMCI), but screening failures are high because only a half of patients with aMCI are positive on Aβ PET. Therefore, it becomes necessary for clinicians to predict which patients will have Aβ biomarker.

OBJECTIVE

We aimed to compare clinical factors, neuropsychological (NP) profiles, and apolipoprotein E (APOE) genotype between Aβ+ aMCI and Aβ-aMCI and to develop a clinically useful prediction model of Aβ positivity on PET (PET-Aβ+) in aMCI using a nomogram.

METHODS

We recruited 523 aMCI patients who underwent Aβ PET imaging in a nation-wide multicenter cohort. The results of NP measures were divided into following subgroups: 1) Stage (Early and Late-stage), 2) Modality (Visual, Verbal, and Both), 3) Recognition failure, and 4) Multiplicity (Single and Multiple). A nomogram for PET-Aβ+ in aMCI patients was constructed using a logistic regression model.

RESULTS

PET-Aβ+ had significant associations with NP profiles for several items, including high Clinical Dementia Rating Scale Sum of Boxes score (OR 1.47, p = 0.013) and impaired memory modality (impaired both visual and verbal memories compared with visual only, OR 3.25, p = 0.001). Also, presence of APOEɛ4 (OR 4.14, p < 0.001) was associated with PET-Aβ+. These predictors were applied to develop the nomogram, which showed good prediction performance (C-statistics = 0.79). Its prediction performances were 0.77/0.74 in internal/external validation.

CONCLUSIONS

The nomogram consisting of NP profiles, especially memory domain, and APOEɛ4 genotype may provide a useful predictive model of PET-Aβ+ in patients with aMCI.

A new perspective for advanced positron emission tomography-based molecular imaging in neurodegenerative proteinopathies

Recent studies in neurodegenerative conditions have increasingly highlighted that the same neuropathology can trigger different clinical phenotypes or, vice-versa, that similar phenotypes can be triggered by different neuropathologies. This evidence has called for the adoption of a pathology spectrum-based approach to study neurodegenerative proteinopathies. These conditions share brain deposition of abnormal protein aggregates, leading to aberrant biochemical, metabolic, functional, and structural changes. Positron emission tomography (PET) is a well-recognized and unique tool for the in vivo assessment of brain neuropathology, and novel PET techniques are emerging for the study of specific protein species. Today, key applications of PET range from early research and clinical diagnostic tools to their use in clinical trials for both participants screening and outcome evaluation. This position article critically reviews the role of distinct PET molecular tracers for different neurodegenerative proteinopathies, highlighting their strengths, weaknesses, and opportunities, with special emphasis on methodological challenges and future applications.

Association of plasma endothelial lipase levels on cognitive impairment

BACKGROUND

Peripheral high-density lipoprotein cholesterol (HDL-C) has been known to influx into the brain and be inversely associated with the risk of Alzheimer's disease (AD). However, recent prospective studies of the association between HDL-C and AD have yielded inconsistent results. Here, we examined the association between the endothelial lipase (EL), which is known to be major determinant of HDL-C levels, and cognitive function.

METHOD

We compared plasma from 20 patients with Alzheimer's disease (AD), 38 persons with mild cognitive impairment, and 51 cognitively normal controls. Plasma EL levels were measured using the enzyme-linked immunosorbent assay.

RESULTS

EL levels were inversely correlated with HDL-C, as previously reported; however, there were no mean differences in plasma EL between the diagnostic groups. An analysis by classification of dementia severity according to clinical dementia rating (CDR) showed that the EL levels were significantly higher in the CDR1 group (mild dementia), as compared to CDR0 (no dementia), CDR0.5 (very mild), and CDR2 (moderate) groups. Prior to moderate dementia stage, trends analysis showed that EL levels tended to increase with increasing severity (p for trend = 0.013). Consistently, elevated EL levels were significantly correlated with the mini-mental state examination (MMSE) score (r = - 0.29, p = 0.003). Logistic regression for association between plasma EL and cognitive impairment (MMSE score ≤ 25) showed that participants with EL levels in the upper range (> 31.6 ng/ml) have a higher adjusted odds ratio of cognitive impairment than those within the lower EL range.

CONCLUSION

Findings from the present study reflect the association of EL and cognition, suggesting that the individuals with elevated plasma EL concentration are at an increased risk of cognitive impairment.

Advances in cerebral amyloid angiopathy imaging

Cerebral amyloid angiopathy (CAA) is a cerebral small vessel disease caused by β -amyloid (Aβ) deposition at the leptomeningeal vessel walls. It is a common cause of spontaneous intracerebral hemorrhage and a frequent comorbidity in Alzheimer’s disease. The high recurrent hemorrhage rate in CAA makes it very important to recognize this disease to avoid potential harmful medication. Imaging studies play an important role in diagnosis and research of CAA. Conventional computed tomography and magnetic resonance imaging (MRI) methods reveal anatomical alterations, and remains as the most reliable tool in identifying CAA according to modified Boston criteria. The vascular injuries of CAA result in both hemorrhagic and ischemic manifestations and related structural changes on MRI, including cerebral microbleeds, cortical superficial siderosis, white matter hyperintensity, MRI-visible perivascular spaces, and cortical microinfarcts. As imaging techniques advance, not only does the resolution of conventional imaging improve, but novel skills in functional and molecular imaging studies also enable in vivo analysis of vessel physiological changes and underlying pathology. These modern tools help in early detection of CAA and may potentially serve as sensitive outcome markers in future clinical trials. In this article, we reviewed past studies of CAA focusing on utilization of various conventional and novel imaging techniques in both research and clinical aspects.

Neuroimaging in aging and neurologic diseases

Neuroimaging biomarkers for neurologic diseases are important tools, both for understanding pathology associated with cognitive and clinical symptoms and for differential diagnosis. This chapter explores neuroimaging measures, including structural and functional measures from magnetic resonance imaging (MRI) and molecular measures primarily from positron emission tomography (PET), in healthy aging adults and in a number of neurologic diseases. The spectrum covers neuroimaging measures from normal aging to a variety of dementias: late-onset Alzheimer's disease [AD; including mild cognitive impairment (MCI)], familial and nonfamilial early-onset AD, atypical AD syndromes, posterior cortical atrophy (PCA), logopenic aphasia (lvPPA), cerebral amyloid angiopathy (CAA), vascular dementia (VaD), sporadic and familial behavioral-variant frontotemporal dementia (bvFTD), semantic dementia (SD), progressive nonfluent aphasia (PNFA), frontotemporal dementia with motor neuron disease (FTD-MND), frontotemporal dementia with amyotrophic lateral sclerosis (FTD-ALS), corticobasal degeneration (CBD), progressive supranuclear palsy (PSP), dementia with Lewy bodies (DLB), Parkinson's disease (PD) with and without dementia, and multiple systems atrophy (MSA). We also include a discussion of the appropriate use criteria (AUC) for amyloid imaging and conclude with a discussion of differential diagnosis of neurologic dementia disorders in the context of neuroimaging.

Lessons learned about [F-18]-AV-1451 off-target binding from an autopsy-confirmed Parkinson's case

[F-18]-AV-1451 is a novel positron emission tomography (PET) tracer with high affinity to neurofibrillary tau pathology in Alzheimer’s disease (AD). PET studies have shown increased tracer retention in patients clinically diagnosed with dementia of AD type and mild cognitive impairment in regions that are known to contain tau lesions. In vivo uptake has also consistently been observed in midbrain, basal ganglia and choroid plexus in elderly individuals regardless of their clinical diagnosis, including clinically normal whose brains are not expected to harbor tau pathology in those areas. We and others have shown that [F-18]-AV-1451 exhibits off-target binding to neuromelanin, melanin and blood products on postmortem material; and this is important for the correct interpretation of PET images. In the present study, we further investigated [F-18]-AV-1451 off-target binding in the first autopsy-confirmed Parkinson’s disease (PD) subject who underwent antemortem PET imaging. The PET scan showed elevated [F-18]-AV-1451 retention predominantly in inferior temporal cortex, basal ganglia, midbrain and choroid plexus. Neuropathologic examination confirmed the PD diagnosis. Phosphor screen and high resolution autoradiography failed to show detectable [F-18]-AV-1451 binding in multiple brain regions examined with the exception of neuromelanin-containing neurons in the substantia nigra, leptomeningeal melanocytes adjacent to ventricles and midbrain, and microhemorrhages in the occipital cortex (all reflecting off-target binding), in addition to incidental age-related neurofibrillary tangles in the entorhinal cortex. Additional legacy postmortem brain samples containing basal ganglia, choroid plexus, and parenchymal hemorrhages from 20 subjects with various neuropathologic diagnoses were also included in the autoradiography experiments to better understand what [F-18]-AV-1451 in vivo positivity in those regions means. No detectable [F-18]-AV-1451 autoradiographic binding was present in the basal ganglia of the PD case or any of the other subjects. Off-target binding in postmortem choroid plexus samples was only observed in subjects harboring leptomeningeal melanocytes within the choroidal stroma. Off-target binding to parenchymal hemorrhages was noticed in postmortem material from subjects with cerebral amyloid angiopathy. The imaging-postmortem correlation analysis in this PD case reinforces the notion that [F-18]-AV-1451 has strong affinity for neurofibrillary tau pathology but also exhibits off-target binding to neuromelanin, melanin and blood components. The robust off-target in vivo retention in basal ganglia and choroid plexus, in the absence of tau deposits, meningeal melanocytes or any other identifiable binding substrate by autoradiography in the PD case reported here, also suggests that the PET signal in those regions may be influenced, at least in part, by biological or technical factors that occur in vivo and are not captured by autoradiography.