Differentiating Prodromal Dementia with Lewy Bodies from Prodromal Alzheimer's Disease: A Pragmatic Review for Clinicians

This pragmatic review synthesises the current understanding of prodromal dementia with Lewy bodies (pDLB) and prodromal Alzheimer's disease (pAD), including clinical presentations, neuropsychological profiles, neuropsychiatric symptoms, biomarkers, and indications for disease management. The core clinical features of dementia with Lewy bodies (DLB)-parkinsonism, complex visual hallucinations, cognitive fluctuations, and REM sleep behaviour disorder are common prodromal symptoms. Supportive clinical features of pDLB include severe neuroleptic sensitivity, as well as autonomic and neuropsychiatric symptoms. The neuropsychological profile in mild cognitive impairment attributable to Lewy body pathology (MCI-LB) tends to include impairment in visuospatial skills and executive functioning, distinguishing it from MCI due to AD, which typically presents with impairment in memory. pDLB may present with cognitive impairment, psychiatric symptoms, and/or recurrent episodes of delirium, indicating that it is not necessarily synonymous with MCI-LB. Imaging, fluid and other biomarkers may play a crucial role in differentiating pDLB from pAD. The current MCI-LB criteria recognise low dopamine transporter uptake using positron emission tomography or single photon emission computed tomography (SPECT), loss of REM atonia on polysomnography, and sympathetic cardiac denervation using meta-iodobenzylguanidine SPECT as indicative biomarkers with slowing of dominant frequency on EEG among others as supportive biomarkers. This review also highlights the emergence of fluid and skin-based biomarkers. There is little research evidence for the treatment of pDLB, but pharmacological and non-pharmacological treatments for DLB may be discussed with patients. Non-pharmacological interventions such as diet, exercise, and cognitive stimulation may provide benefit, while evaluation and management of contributing factors like medications and sleep disturbances are vital. There is a need to expand research across diverse patient populations to address existing disparities in clinical trial participation. In conclusion, an early and accurate diagnosis of pDLB or pAD presents an opportunity for tailored interventions, improved healthcare outcomes, and enhanced quality of life for patients and care partners.

Grey matter networks in women and men with dementia with Lewy bodies

Sex differences permeate many aspects of dementia with Lewy bodies (DLB), yet sex differences in patterns of neurodegeneration in DLB remain largely unexplored. Here, we test whether grey matter networks differ between sexes in DLB and compare these findings to sex differences in healthy controls. In this cross-sectional study, we analysed clinical and neuroimaging data of patients with DLB and cognitively healthy controls matched for age and sex. Grey matter networks were constructed by pairwise correlations between 58 regional volumes after correction for age, intracranial volume, and centre. Network properties were compared between sexes and diagnostic groups. Additional analyses were conducted on w-scored data to identify DLB-specific sex differences. Data from 119 (68.7 ± 8.4 years) men and 45 women (69.9 ± 9.1 years) with DLB, and 164 healthy controls were included in this study. Networks of men had a lower nodal strength compared to women. In comparison to healthy women, the grey matter networks of healthy men showed a higher global efficiency, modularity, and fewer modules. None of the network measures showed significant sex differences in DLB. Comparing DLB patients with healthy controls revealed global differences in women and more local differences in men. Modular analyses showed a more distinct demarcation between cortical and subcortical regions in men compared with women. While topologies of grey matter networks differed between sexes in healthy controls, those sex differences were diluted in DLB patients. These findings suggest a disease-driven convergence of neurodegenerative patterns in women and men with DLB, which may inform precision medicine in DLB.

Multi-pathological contributions toward atrophy patterns in the Alzheimer's disease continuum

Introduction

Heterogeneity in downstream atrophy in Alzheimer's disease (AD) is predominantly investigated in relation to pathological hallmarks (Aβ, tau) and co-pathologies (cerebrovascular burden) independently. However, the proportional contribution of each pathology in determining atrophy pattern remains unclear. We assessed heterogeneity in atrophy using two recently conceptualized dimensions: typicality (typical AD atrophy at the center and deviant atypical atrophy on either extreme including limbic predominant to hippocampal sparing patterns) and severity (overall neurodegeneration spanning minimal atrophy to diffuse typical AD atrophy) in relation to Aβ, tau, and cerebrovascular burden.

Methods

We included 149 Aβ + individuals on the AD continuum (cognitively normal, prodromal AD, AD dementia) and 163 Aβ- cognitively normal individuals from the ADNI. We modeled heterogeneity in MRI-based atrophy with continuous-scales of typicality (ratio of hippocampus to cortical volume) and severity (total gray matter volume). Partial correlation models investigated the association of typicality/severity with (a) Aβ (global Aβ PET centiloid), tau (global tau PET SUVR), cerebrovascular (total white matter hypointensity volume) burden (b) four cognitive domains (memory, executive function, language, visuospatial composites). Using multiple regression, we assessed the association of each pathological burden and typicality/severity with cognition.

Results

(a) In the AD continuum, typicality (r = -0.31, p < 0.001) and severity (r = -0.37, p < 0.001) were associated with tau burden after controlling for Aβ, cerebrovascular burden and age. Findings imply greater tau pathology in limbic predominant atrophy and diffuse atrophy. (b) Typicality was associated with memory (r = 0.49, p < 0.001) and language scores (r = 0.19, p = 0.02). Severity was associated with memory (r = 0.26, p < 0.001), executive function (r = 0.24, p = 0.003) and language scores (r = 0.29, p < 0.001). Findings imply better cognitive performance in hippocampal sparing and minimal atrophy patterns. Beyond typicality/severity, tau burden but not Aβ and cerebrovascular burden explained cognition.

Conclusion

In the AD continuum, atrophy-based severity was more strongly associated with tau burden than typicality after accounting for Aβ and cerebrovascular burden. Cognitive performance in memory, executive function and language domains was explained by typicality and/or severity and additionally tau pathology. Typicality and severity may differentially reflect burden arising from tau pathology but not Aβ or cerebrovascular pathologies which need to be accounted for when investigating AD heterogeneity.

Digital health and cardiovascular healthcare professionals in Portugal: Current status, expectations and barriers to implementation

INTRODUCTION AND OBJECTIVES

Digital health (DH) is a broad concept, bringing together technology and healthcare, that is playing an increasingly important role in the daily routine of healthcare professionals (HCPs) and promises to contribute to the prevention and treatment of cardiovascular disease. There are no solid data on the position of Portuguese HCPs toward the implementation of DH in cardiovascular medicine. This national cross-sectional study aims to provide a snapshot of DH implementation in Portuguese cardiovascular HCP routines and to identify both expectations and barriers to its adoption.

METHODS

An 18-question survey was created specifically for this study and distributed to 1174 individuals on the Portuguese Society of Cardiology mailing list.

RESULTS

We collected 117 valid responses (response rate 10%). Almost all participants had smartphones and laptops, and two-thirds had tablets. Electronic medical information systems were the most used DH tool (84% of respondents) and were considered the most important for improving cardiovascular care. Implantable technologies (sensors and devices), telemedicine and social media were used by more than two out of three respondents and considered «very important» or «extremely important» by most of them. Most participants showed positive expectations regarding the impact of DH in cardiovascular medicine: 78% agreed that DH could improve health outcomes, 64% that it promotes health literacy and 63% that it could decrease healthcare costs. The top-rated barriers were patients' inability to use smartphones, limited access to electronic devices, and lack of legal regulation of DH.

CONCLUSION

Most Portuguese cardiovascular HCPs had at least three electronic devices (mainly smartphones, laptops and tablets) and showed positive expectations regarding DH's current and future impact on cardiovascular medicine. Patient DH literacy, technology adoption, and DH regulation were identified as the most important barriers to increasing the adoption of DH tools in cardiovascular medicine.

Oscillatory and non-oscillatory features of the magnetoencephalic sensorimotor rhythm in Parkinson's disease

Parkinson's disease (PD) is associated with changes in neural activity in the sensorimotor alpha and beta bands. Using magnetoencephalography (MEG), we investigated the role of spontaneous neuronal activity within the somatosensory cortex in a large cohort of early- to mid-stage PD patients (N = 78) on Parkinsonian medication and age- and sex-matched healthy controls (N = 60) using source reconstructed resting-state MEG. We quantified features of the time series data in terms of oscillatory alpha power and central alpha frequency, beta power and central beta frequency, and 1/f broadband characteristics using power spectral density. Furthermore, we characterised transient oscillatory burst events in the mu-beta band time-domain signals. We examined the relationship between these signal features and the patients' disease state, symptom severity, age, sex, and cortical thickness. PD patients and healthy controls differed on PSD broadband characteristics, with PD patients showing a steeper 1/f exponential slope and higher 1/f offset. PD patients further showed a steeper age-related decrease in the burst rate. Out of all the signal features of the sensorimotor activity, the burst rate was associated with increased severity of bradykinesia, whereas the burst duration was associated with axial symptoms. Our study shows that general non-oscillatory features (broadband 1/f exponent and offset) of the sensorimotor signals are related to disease state and oscillatory burst rate scales with symptom severity in PD.

In vivo microstructural heterogeneity of white matter and cognitive correlates in aging using tissue compositional analysis of diffusion magnetic resonance imaging

BACKGROUND

Age-related cognitive decline is linked to changes in the brain, particularly the deterioration of white matter (WM) microstructure that accelerates after the age of 60. WM deterioration is associated with mild cognitive impairment and dementia, but the origin and role of white matter signal abnormalities (WMSA) seen in standard MRI remain debated due to their heterogeneity. This study explores the potential of single-shell 3-tissue constrained spherical deconvolution (SS3T-CSD), a novel technique that models diffusion data in terms of gray matter (TG ), white matter (Tw ), and cerebrospinal fluid (TC ), to differentiate WMSA from normal-appearing white matter and better understand the interplay between changes in WM microstructure and decline in cognition.

METHODS

A total of 189 individuals from the GENIC cohort were included. MRI data, including T1-weighted and diffusion images, were obtained. Preprocessing steps were performed on the diffusion MRI data, followed by the SS3T-CSD. WMSA were segmented using FreeSurfer. Statistical analyses were conducted to assess the association between age, WMSA volume, 3-tissue signal fractions (Tw , TG , and TC ), and neuropsychological variables.

RESULTS

Participants above 60 years old showed worse cognitive performance and processing speed compared to those below 60 (p < .001). Age was negatively associated with Tw in normal-appearing white matter (p < .001) and positively associated with TG in both WMSA (p < .01) and normal-appearing white matter (p < .001). Age was also significantly associated with WMSA volume (p < .001). Higher processing speed was associated with lower Tw and higher TG , in normal-appearing white matter (p < .01 and p < .001, respectively), as well as increased WMSA volume (p < .001). Similarly, lower MMSE scores correlated with lower Tw and higher TG in normal-appearing white matter (p < .05). High cholesterol and hypertension were associated with higher WMSA volume (p < .05).

CONCLUSION

The microstructural heterogeneity within normal-appearing white matter and WMSA is associated with increasing age and cognitive variation, in cognitively unimpaired individuals. Furthermore, the 3-tissue signal fractions are more specific to potential white matter alterations than conventional MRI measures such as WMSA volume. These findings also support the view that the WMSA volumes may be more influenced by vascular risk factors than the 3-tissue metrics. Finally, the 3-tissue metrics were able to capture associations with cognitive tests and therefore capable of capturing subtle pathological changes in the brain in individuals who are still within the normal range of cognitive performance.

Sex differences in brain atrophy in dementia with Lewy bodies

INTRODUCTION

Sex influences neurodegeneration, but it has been poorly investigated in dementia with Lewy bodies (DLB). We investigated sex differences in brain atrophy in DLB using magnetic resonance imaging (MRI).

METHODS

We included 436 patients from the European-DLB consortium and the Mayo Clinic. Sex differences and sex-by-age interactions were assessed through visual atrophy rating scales (n = 327; 73 ± 8 years, 62% males) and automated estimations of regional gray matter volume and cortical thickness (n = 165; 69 ± 9 years, 72% males).

RESULTS

We found a higher likelihood of frontal atrophy and smaller volumes in six cortical regions in males and thinner olfactory cortices in females. There were significant sex-by-age interactions in volume (six regions) and cortical thickness (seven regions) across the entire cortex.

DISCUSSION

We demonstrate that males have more widespread cortical atrophy at younger ages, but differences tend to disappear with increasing age, with males and females converging around the age of 75.

HIGHLIGHTS

Male DLB patients had higher odds for frontal atrophy on radiological visual rating scales. Male DLB patients displayed a widespread pattern of cortical gray matter alterations on automated methods. Sex differences in gray matter measures in DLB tended to disappear with increasing age.

Anti-dementia drugs: what is the evidence in advanced stages?

Dementia is a major public health concern due to its increasing prevalence, substantial caregiver burden, and high financial costs. Currently, the anti-dementia drugs aim only at a symptomatic effect. The subject of prescribing these drugs in advanced stages is a matter of considerable debate, with different countries making distinct recommendations. In this review article, we analyzed the evidence regarding cognitive and functional outcomes, adverse events, health-related costs, and caregiver burden in patients with advanced Alzheimer disease (AD) and mixed dementia. We included 35 studies. Most studies are heterogeneous, focus exclusively on AD, and show small benefits in terms of cognitive and functional scales. The overall evidence seems to suggest a benefit in introducing or maintaining anti-dementia drugs in patients with advanced dementia, but clinical meaningfulness is difficult to ascertain. The issue of costs and caregiver burden is significantly underexplored in this field but also seems to favor treatment continuation, despite a reduced overall effect. The decision of introducing or withdrawing anti-dementia drugs in advanced stages of dementia should be individualized. Future studies with homogeneous designs and outcomes are warranted.

Biomarkers of Alzheimer's Disease and Cerebrovascular Disease in Relation to Depressive Symptomatology in Individuals With Subjective Cognitive Decline

BACKGROUND

Subjective cognitive decline (SCD) has gained recent interest as a potential harbinger of neurodegenerative diseases such as Alzheimer's disease (AD) and cerebrovascular disease (CVD). In addition, SCD can be related to depressive symptomatology. However, the association between AD and CVD biomarkers, depressive symptomatology, and SCD is still unclear. We investigated the association of AD and CVD biomarkers and depressive symptomatology with SCD in individuals with subjective memory complaints (SCD-memory group) and individuals with subjective concentration complaints (SCD-concentration group).

METHODS

We recruited a population-based cohort of 217 individuals (all aged 70 years, 53% female participants, 119 SCD-memory individuals, 23 SCD-concentration individuals, and 89 controls). AD and CVD were assessed through cerebrospinal fluid levels of the Aβ42/40 ratio and phosphorylated tau, and white matter signal abnormalities on magnetic resonance imaging, respectively. Associations between biomarkers, depressive symptomatology, and SCD were tested via logistic regression and correlation analyses.

RESULTS

We found a significant association between depressive symptomatology with SCD-memory and SCD-concentration. Depressive symptomatology was not associated with AD and CVD biomarkers. Both the phosphorylated tau biomarker and depressive symptomatology predicted SCD-memory, and the Aβ42/40 ratio and depressive symptomatology predicted SCD-concentration.

CONCLUSIONS

The role of depressive symptomatology in SCD may differ depending on the stage within the spectrum of preclinical AD (as determined by amyloid-beta and tau positivity), and does not seem to reflect AD pathology. Our findings contribute to the emerging field of subclinical depressive symptomatology in SCD and clarify the association of different types of subjective complaints with distinct syndromic and biomarker profiles.

Degeneration of the cholinergic system in individuals with subjective cognitive decline: A systematic review

BACKGROUND

Subjective cognitive decline (SCD) is a risk factor for future cognitive impairment and dementia. It is uncertain whether the neurodegeneration of the cholinergic system is already present in SCD individuals. We aimed to review the current evidence about the association between SCD and biomarkers of degeneration in the cholinergic system.

METHOD

Original articles were extracted from three databases: Pubmed, Web of Sciences, and Scopus, in January 2023. Two researchers screened the studies independently.

RESULTS

A total of 11 research articles were selected. SCD was mostly based on amnestic cognitive complaints. Cholinergic system biomarkers included neuroimaging markers of basal forebrain volume, functional connectivity, transcranial magnetic stimulation, or biofluid. The evidence showed associations between basal forebrain atrophy, poorer connectivity of the cholinergic system, and SCD CONCLUSIONS: Degenerative changes in the cholinergic system can be present in SCD. Subjective complaints may help when identifying individuals with brain changes that are associated with cognitive impairment. These findings may have important implications in targeting individuals that may benefit from cholinergic-target treatments at very early stages of neurodegenerative diseases.

The physical and psychosocial impact of a school-based running programme for adolescents with disabilities

BACKGROUND

Adolescents with disabilities have fewer opportunities to participate in community-based fitness programmes. The purpose of this study was to examine the impact of a school-based running programme at a local middle school in Lebanon, Pennsylvania, on fitness and quality of life (QoL) in children with physical and cognitive disabilities in a life-skills classroom.

METHODS

Nineteen adolescents with diagnosed disabilities including intellectual disability (ID), autism spectrum disorder and Down syndrome were recruited from three life-skills classrooms to participate in a school-based running programme. The programme was designed to be implemented two times/week for 6 weeks by classroom teachers/aides. Physical therapy faculty and students developed the programme and assisted with implementation. Each session lasted 30 min, consisting of a warm-up and cooldown, relay races, games and timed runs. Pre- and post-test measures included physiological cost index (PCI) and Paediatric Quality of Life Inventory™ (PedsQL™). Pre- and post-test data were compared using Wilcoxon signed rank tests. Each week participants also completed a training log to reflect on the activity for the day.

RESULTS

Participants demonstrated significant improvements in PCI (P = 0.028) and the PedsQL™ (P = 0.008) following the running programme.

CONCLUSIONS

Results of this study suggest that participation in a 6-week school-based running programme may improve fitness and QoL in adolescents with disabilities.

A deep learning model for brain age prediction using minimally preprocessed T1w images as input

Introduction

In the last few years, several models trying to calculate the biological brain age have been proposed based on structural magnetic resonance imaging scans (T1-weighted MRIs, T1w) using multivariate methods and machine learning. We developed and validated a convolutional neural network (CNN)-based biological brain age prediction model that uses one T1w MRI preprocessing step when applying the model to external datasets to simplify implementation and increase accessibility in research settings. Our model only requires rigid image registration to the MNI space, which is an advantage compared to previous methods that require more preprocessing steps, such as feature extraction.

Methods

We used a multicohort dataset of cognitively healthy individuals (age range = 32.0-95.7 years) comprising 17,296 MRIs for training and evaluation. We compared our model using hold-out (CNN1) and cross-validation (CNN2-4) approaches. To verify generalisability, we used two external datasets with different populations and MRI scan characteristics to evaluate the model. To demonstrate its usability, we included the external dataset's images in the cross-validation training (CNN3). To ensure that our model used only the brain signal on the image, we also predicted brain age using skull-stripped images (CNN4).

Results

The trained models achieved a mean absolute error of 2.99, 2.67, 2.67, and 3.08 years for CNN1-4, respectively. The model's performance in the external dataset was in the typical range of mean absolute error (MAE) found in the literature for testing sets. Adding the external dataset to the training set (CNN3), overall, MAE is unaffected, but individual cohort MAE improves (5.63-2.25 years). Salience maps of predictions reveal that periventricular, temporal, and insular regions are the most important for age prediction.

Discussion

We provide indicators for using biological (predicted) brain age as a metric for age correction in neuroimaging studies as an alternative to the traditional chronological age. In conclusion, using different approaches, our CNN-based model showed good performance using one T1w brain MRI preprocessing step. The proposed CNN model is made publicly available for the research community to be easily implemented and used to study ageing and age-related disorders.

Association of CSF biomarkers with MRI brain changes in Alzheimer's disease

The relation between cerebrospinal fluid (CSF) biomarkers of Alzheimer's disease (AD) and magnetic resonance imaging (MRI) measures is poorly understood in cognitively healthy individuals from the general population. Participants' (n = 226) mean age was 70.9 years (SD = 0.4). CSF concentrations of amyloid beta (Aβ)1-42, total tau (t-tau), phosphorylated tau (p-tau), neurogranin, and neurofilament light, and volumes of hippocampus, amygdala, total basal forebrain (TBF), and cortical thickness were measured. Linear associations between CSF biomarkers and MRI measures were investigated. In Aβ1-42 positives, higher t-tau and p-tau were associated with smaller hippocampus (P = 0.001 and P = 0.003) and amygdala (P = 0.005 and P = 0.01). In Aβ1-42 negatives, higher t-tau, p-tau, and neurogranin were associated with larger TBF volume (P = 0.001, P = 0.001, and P = 0.01). No associations were observed between the CSF biomarkers and an AD signature score of cortical thickness. AD-specific biomarkers in cognitively healthy 70-year-olds may be related to TBF, hippocampus, and amygdala. Lack of association with cortical thickness might be due to early stage of disease.

Impact of a wearable-based physical activity and sleep intervention in multimorbidity patients: protocol for a randomized controlled trial

BACKGROUND

The benefits of physical activity (PA) and adequate sleep are well documented, and their importance strengthens with the increasing prevalence of chronic diseases and multimorbidity (MM). Interventions to promote physical activity and sleep that use commercial activity trackers may be useful non-pharmacological approaches to managing individual health; however, limited evidence exists on their use to improve physical activity in older adult patients with MM.

METHODS

This study aims to measure the effects of behavioral change techniques (BCTs) delivered by a wearable device on physical activity and quality of sleep (QS) in older adult patients with MM. We designed an open-label randomized controlled trial with participants recruited through primary care and a specialist outpatient clinic. Participants must be more than 65 years old, have MM, and have access to smartphones. All eligible participants will receive PA promotion content and will be randomly assigned to wear a smartwatch. The primary outcome will be the participants' PA measurement at baseline and at six months using the International Physical Activity Questionnaire - Short Form (IPAQ-SF). Secondary outcomes will include changes in the participants' frailty status, biometric measurements, quality of life, and biopsychosocial assessments. A sample size of 40 participants per arm was calculated to detect group differences, with 50 participants planned to recruit and randomize into each arm.

DISCUSSION

This study aims to contribute to a better understanding of PA patterns and the impact of wearable-based PA interventions in patients with MM. In addition, we aim to contribute to more knowledge about the relationship between PA patterns, Patient Reported Outcomes Measures (PROMs), and healthcare resource utilization in patients with MM. To achieve this, the study will leverage a locally developed PROMs registry and assess data from participants' medical records, in order to understand the added impact of wearable data and medical information data on predicting PROMs and unplanned hospital admissions.

TRIAL REGISTRATION

NCT05777291.

Child Neurology: Anti-Hu Encephalitis in an Adolescent With a Mediastinal Seminoma

Anti-Hu antibodies are associated with autoimmune syndromes, mainly limbic encephalitis, encephalomyelitis, and painful sensory polyneuropathy (Denny-Brown). We report the case of a 15-year-old boy presenting with epilepsia partialis continua (EPC) found to have a right middle frontal gyrus brain lesion without atrophy or contralateral involvement. After partial resection, neuropathology revealed neuronal loss, reactive gliosis and astrocytosis, and perivascular mononuclear inflammatory infiltrate and features of neuronophagia resembling Rasmussen encephalitis. Suboptimal response to antiseizure drugs and surgery prompted further workup with identification of positive serum anti-Hu antibodies and a mediastinal seminoma. The patient was treated with immunotherapy including steroids, IV immunoglobulin, azathioprine, rituximab, plasmapheresis, and mediastinal lesion resection. However, he continued to experience EPC and psychomotor impairment along with left hemiparesis and dysarthria. Given clinical progression with failure to respond to immunotherapy and antiseizure polytherapy, hemispherotomy was attempted and seizure freedom achieved. A review of the literature found only 16 cases of neurologic presentations associated with anti-Hu antibodies in children, confirming the rarity of EPC in these cases. Thus, this report provides a new observation of germ cell mediastinal tumor associated with anti-Hu antibodies in children, broadening the spectrum of anti-Hu-associated neurologic disorders in children and highlighting the importance of considering antineuronal antibody testing in children presenting with EPC and brain lesions suggestive of Rasmussen encephalitis.

Occipital atrophy signature in prodromal Lewy bodies disease

INTRODUCTION

Dementia with Lewy bodies (DLB) is typically characterized by parietal, temporal, and occipital atrophy, but less is known about the newly defined prodromal phases. The objective of this study was to evaluate structural brain alterations in prodromal DLB (p-DLB) as compared to healthy controls (HC) and full-blown dementia (DLB-DEM).

METHODS

The study included 42 DLB patients (n = 20 p-DLB; n = 22 DLB-DEM) and 27 HC with a standardized neurological assessment and 3-tesla magnetic resonance imaging. Voxel-wise analyses on gray-matter and cortical thickness were implemented to evaluate differences between p-DLB, DLB-DEM, and HC.

RESULTS

p-DLB and DLB-DEM exhibited reduced occipital and posterior parieto-temporal volume and thickness, extending from prodromal to dementia stages. Occipital atrophy was more sensitive than insular atrophy in differentiating p-DLB and HC. Occipital atrophy correlated to frontotemporal structural damage increasing from p-DLB to DLB-DEM.

DISCUSSION

Occipital and posterior-temporal structural alterations are an early signature of the DLB continuum and correlate with a long-distance pattern of atrophy.

A metagenomic study of gut viral markers in amyloid-positive Alzheimer's disease patients

BACKGROUND

Mounting evidence suggests the involvement of viruses in the development and treatment of Alzheimer's disease (AD). However, there remains a significant research gap in metagenomic studies investigating the gut virome of AD patients, leaving gut viral dysbiosis in AD unexplored. This study aimed to fill this gap by conducting a metagenomics analysis of the gut virome in both amyloid-positive AD patients (Aβ + ADs) and healthy controls (HCs), with the objective of identifying viral signatures linked with AD.

METHOD

Whole-genome sequence (WGS) data from 65 human participants, including 30 Aβ + ADs and 35 HCs, was obtained from the database NCBI SRA (Bio Project: PRJEB47976). The Metaphlan3 pipeline and linear discriminant analysis effect size (LEfSe) analysis were utilized for the bioinformatics process and the detection of viral signatures, respectively. In addition, the Benjamini-Hochberg method was applied with a significance cutoff of 0.05 to evaluate the false discovery rate for all biomarkers identified by LEfSe. The CombiROC model was employed to determine the discriminatory power of the viral signatures identified by LEfSe.

RESULTS

Compared to HCs, the gut virome profiles of Aβ + ADs showed lower alpha diversity, indicating a lower bacteriophage richness. The Siphoviridae family was decreased in Aβ + ADs. Significant decreases of Lactococcus phages were found in Aβ + ADs, including bIL285, Lactococcus phage bIL286, Lactococcus phage bIL309, and Lactococcus phage BK5 T, Lactococcus phage BM13, Lactococcus phage P335 sensu lato, Lactococcus phage phiLC3, Lactococcus phage r1t, Lactococcus phage Tuc2009, Lactococcus phage ul36, and Lactococcus virus bIL67. The predictive combined model of these viral signatures obtained an area under the curve of 0.958 when discriminating Aβ + ADs from HCs.

CONCLUSION

This is the first study to identify distinct viral signatures in the intestine that can be used to effectively distinguish individuals with AD from HCs.

Research diagnostic criteria for mild cognitive impairment with Lewy bodies: A systematic review and meta-analysis

INTRODUCTION

Operationalized research criteria for mild cognitive impairment with Lewy bodies (MCI-LB) were published in 2020. The aim of this systematic review and meta-analysis was to review the evidence for the diagnostic clinical features and biomarkers in MCI-LB set out in the criteria.

METHODS

MEDLINE, PubMed, and Embase were searched on 9/28/22 for relevant articles. Articles were included if they presented original data reporting the rates of diagnostic features in MCI-LB.

RESULTS

Fifty-seven articles were included. The meta-analysis supported the inclusion of the current clinical features in the diagnostic criteria. Evidence for striatal dopaminergic imaging and meta-iodobenzylguanidine cardiac scintigraphy, though limited, supports their inclusion. Quantitative electroencephalogram (EEG) and fluorodeoxyglucose positron emission tomography (PET) show promise as diagnostic biomarkers.

DISCUSSION

The available evidence largely supports the current diagnostic criteria for MCI-LB. Further evidence will help refine the diagnostic criteria and understand how best to apply them in clinical practice and research.

HIGHLIGHTS

A meta-analysis of the diagnostic features of MCI-LB was carried out. The four core clinical features were more common in MCI-LB than MCI-AD/stable MCI. Neuropsychiatric and autonomic features were also more common in MCI-LB. More evidence is needed for the proposed biomarkers. FDG-PET and quantitative EEG show promise as diagnostic biomarkers in MCI-LB.

Southern ocean carbon and heat impact on climate

The Southern Ocean greatly contributes to the regulation of the global climate by controlling important heat and carbon exchanges between the atmosphere and the ocean. Rates of climate change on decadal timescales are therefore impacted by oceanic processes taking place in the Southern Ocean, yet too little is known about these processes. Limitations come both from the lack of observations in this extreme environment and its inherent sensitivity to intermittent processes at scales that are not well captured in current Earth system models. The Southern Ocean Carbon and Heat Impact on Climate programme was launched to address this knowledge gap, with the overall objective to understand and quantify variability of heat and carbon budgets in the Southern Ocean through an investigation of the key physical processes controlling exchanges between the atmosphere, ocean and sea ice using a combination of observational and modelling approaches. Here, we provide a brief overview of the programme, as well as a summary of some of the scientific progress achieved during its first half. Advances range from new evidence of the importance of specific processes in Southern Ocean ventilation rate (e.g. storm-induced turbulence, sea-ice meltwater fronts, wind-induced gyre circulation, dense shelf water formation and abyssal mixing) to refined descriptions of the physical changes currently ongoing in the Southern Ocean and of their link with global climate. This article is part of a discussion meeting issue 'Heat and carbon uptake in the Southern Ocean: the state of the art and future priorities'.

Differential response to donepezil in MRI subtypes of mild cognitive impairment

BACKGROUND

Donepezil is an approved therapy for the treatment of Alzheimer's disease (AD). Results across clinical trials have been inconsistent, which may be explained by design-methodological issues, the pathophysiological heterogeneity of AD, and diversity of included study participants. We investigated whether response to donepezil differs in mild cognitive impaired (MCI) individuals demonstrating different magnetic resonance imaging (MRI) subtypes.

METHODS

From the Hippocampus Study double-blind, randomized clinical trial, we included 173 MCI individuals (donepezil = 83; placebo = 90) with structural MRI data, at baseline and at clinical follow-up assessments (6-12-month). Efficacy outcomes were the annualized percentage change (APC) in hippocampal, ventricular, and total grey matter volumes, as well as in the AD cortical thickness signature. Participants were classified into MRI subtypes as typical AD, limbic-predominant, hippocampal-sparing, or minimal atrophy at baseline. We primarily applied a subtyping approach based on continuous scale of two subtyping dimensions. We also used the conventional categorical subtyping approach for comparison.

RESULTS

Donepezil-treated MCI individuals showed slower atrophy rates compared to the placebo group, but only if they belonged to the minimal atrophy or hippocampal-sparing subtypes. Importantly, only the continuous subtyping approach, but not the conventional categorical approach, captured this differential response.

CONCLUSIONS

Our data suggest that individuals with MCI, with hippocampal-sparing or minimal atrophy subtype, may have improved benefit from donepezil, as compared with MCI individuals with typical or limbic-predominant patterns of atrophy. The newly proposed continuous subtyping approach may have advantages compared to the conventional categorical approach. Future research is warranted to demonstrate the potential of subtype stratification for disease prognosis and response to treatment.

TRIAL REGISTRATION

ClinicalTrial.gov NCT00403520. Submission Date: November 21, 2006.

Misfolded alpha-synuclein detection by RT-QuIC in dementia with lewy bodies: a systematic review and meta-analysis

Introduction: Dementia with Lewy Bodies (DLB) is the second most common cause of neurodegenerative dementia after Alzheimer's disease (AD), but the field is still lacking a specific biomarker for its core pathology: alpha synuclein (α-syn). Realtime quaking induced conversion (RT-QuIC) has recently emerged as a strong biomarker candidate to detect misfolded α-syn in DLB. However, the variability in the parameters of the technique and the heterogeneity of DLB patients make the reproducibility of the results difficult. Here, we provide an overview of the state-of-the-art research of α-syn RT-QuIC in DLB focused on: (1) the capacity of α-syn RT-QuIC to discriminate DLB from controls, Parkinson's disease (PD) and AD; (2) the capacity of α-syn RT-QuIC to identify prodromal stages of DLB; and (3) the influence of co-pathologies on α-syn RT-QuIC's performance. We also assessed the influence of different factors, such as technical conditions (e.g., temperature, pH, shaking-rest cycles), sample type, and clinical diagnosis versus autopsy confirmation. Methods: We conducted a systematic review following the PRISMA guidelines in August 2022, without any limits in publication dates. Search terms were combinations of "RT-QuIC" and "Lewy Bodies," "DLB" or "LBD". Results: Our meta-analysis shows that α-syn RT-QuIC reaches very high diagnostic performance in discriminating DLB from both controls (pooled sensitivity and specificity of 0.94 and 0.96, respectively) and AD (pooled sensitivity and specificity of 0.95 and 0.88) and is promising for prodromal phases of DLB. However, the performance of α-syn RT-QuIC to discriminate DLB from PD is currently low due to low specificity (pooled sensitivity and specificity of 0.94 and 0.11). Our analysis showed that α-syn RT-QuIC's performance is not substantially influenced by sample type or clinical diagnosis versus autopsy confirmation. Co-pathologies did not influence the performance of α-syn RT-QuIC, but the number of such studies is currently limited. We observed technical variability across published articles. However, we could not find a clear effect of technical variability on the reported results. Conclusion: There is currently enough evidence to test misfolded α-syn by RT-QuIC for clinical use. We anticipate that harmonization of protocols across centres and advances in standardization will facilitate the clinical establishment of misfolded α-syn detection by RT-QuIC.

Comparing three neuropsychological subgrouping approaches in subjective and mild cognitive impairment from a naturalistic multicenter study

Subjective cognitive impairment (SCI) and mild cognitive impairment (MCI) are two clinical groups with an increased risk to develop dementia, but they are highly heterogeneous. This study compared three different approaches to subgroup SCI and MCI patients and investigated their capacity to disentangle cognitive and biomarker heterogeneity. We included 792 patients from the MemClin-cohort (142 SCI and 650 MCI). Biomarkers included cerebrospinal fluid measures of beta-amyloid-42 and phosphorylated tau, as well as visual ratings of medial temporal lobe atrophy and white matter hyperintensities on magnetic resonance imaging. We found that a more inclusive approach identified individuals with a positive beta-amyloid-42 biomarker; a less inclusive approach captured individuals with higher medial temporal lobe atrophy; and a data-driven approach captured individuals with high white matter hyperintensities burden. The three approaches also captured some neuropsychological differences. We conclude that choice of approach may differ depending on the purpose. This study helps to advance our current understanding of the clinical and biological heterogeneity within SCI and MCI, particularly in the unselected memory clinic setting.

Recurrent encephalopathy associated with pegylated beta-interferon treatment

A 62-year-old woman with a history of multiple sclerosis (MS) presented with recurrent episodes of confusion, dysarthria and gait difficulties. These episodes occurred about 3 days after administration of pegylated interferon-beta-1a (Plegridy®) and resolved spontaneously in around 4 days. The brain MRI scan, laboratory findings and cerebrospinal fluid analysis during these episodes were negative for other causes of encephalopathy. She discontinued treatment with interferon and was started on teriflunomide, experiencing no recurrence of symptoms. We believe that interferon was responsible for this patient's recurrent encephalopathic syndrome, possibly due to its effects on inflammatory cytokines and endothelial dysfunction.

Fast three-dimensional image generation for healthy brain aging using diffeomorphic registration

Predicting brain aging can help in the early detection and prognosis of neurodegenerative diseases. Longitudinal cohorts of healthy subjects scanned through magnetic resonance imaging (MRI) have been essential to understand the structural brain changes due to aging. However, these cohorts suffer from missing data due to logistic issues in the recruitment of subjects. This paper proposes a methodology for filling up missing data in longitudinal cohorts with anatomically plausible images that capture the subject-specific aging process. The proposed methodology is developed within the framework of diffeomorphic registration. First, two novel modules are introduced within Synthmorph, a fast, state-of-the-art deep learning-based diffeomorphic registration method, to simulate the aging process between the first and last available MRI scan for each subject in three-dimensional (3D). The use of image registration also makes the generated images plausible by construction. Second, we used six image similarity measurements to rearrange the generated images to the specific age range. Finally, we estimated the age of every generated image by using the assumption of linear brain decay in healthy subjects. The methodology was evaluated on 2662 T1-weighted MRI scans from 796 healthy participants from 3 different longitudinal cohorts: Alzheimer's Disease Neuroimaging Initiative, Open Access Series of Imaging Studies-3, and Group of Neuropsychological Studies of the Canary Islands (GENIC). In total, we generated 7548 images to simulate the access of a scan per subject every 6 months in these cohorts. We evaluated the quality of the synthetic images using six quantitative measurements and a qualitative assessment by an experienced neuroradiologist with state-of-the-art results. The assumption of linear brain decay was accurate in these cohorts (R2  ∈ [.924, .940]). The experimental results show that the proposed methodology can produce anatomically plausible aging predictions that can be used to enhance longitudinal datasets. Compared to deep learning-based generative methods, diffeomorphic registration is more likely to preserve the anatomy of the different structures of the brain, which makes it more appropriate for its use in clinical applications. The proposed methodology is able to efficiently simulate anatomically plausible 3D MRI scans of brain aging of healthy subjects from two images scanned at two different time points.

Associations between different tau-PET patterns and longitudinal atrophy in the Alzheimer's disease continuum: biological and methodological perspectives from disease heterogeneity

BACKGROUND

Subtypes and patterns are defined using tau-PET (tau pathology) and structural MRI (atrophy) in Alzheimer's disease (AD). However, the relationship between tau pathology and atrophy across these subtypes/patterns remains unclear. Therefore, we investigated the biological association between baseline tau-PET patterns and longitudinal atrophy in the AD continuum; and the methodological characterization of heterogeneity as a continuous phenomenon over the conventional discrete subgrouping.

METHODS

In 366 individuals (amyloid-beta-positive cognitively normal, prodromal AD, AD dementia; amyloid-beta-negative cognitively normal), we examined the association between tau-PET patterns and longitudinal MRI. We modeled tau-PET patterns as a (a) continuous phenomenon with key dimensions: typicality and severity; and (b) discrete phenomenon by categorization into patterns: typical, limbic predominant, cortical predominant and minimal tau. Tau-PET patterns and associated longitudinal atrophy were contextualized within the Amyloid/Tau/Neurodegeneration (A/T/N) biomarker scheme.

RESULTS

Localization and longitudinal atrophy change vary differentially across different tau-PET patterns in the AD continuum. Atrophy, a downstream event, did not always follow a topography akin to the corresponding tau-PET pattern. Further, heterogeneity as a continuous phenomenon offered an alternative and useful characterization, sharing correspondence with the conventional subgrouping. Tau-PET patterns also show differential A/T/N profiles.

CONCLUSIONS

The site and rate of atrophy are different across the tau-PET patterns. Heterogeneity should be treated as a continuous, not discrete, phenomenon for greater sensitivity. Pattern-specific A/T/N profiles highlight differential multimodal interactions underlying heterogeneity. Therefore, tracking multimodal interactions among biomarkers longitudinally, modeling disease heterogeneity as a continuous phenomenon, and examining heterogeneity across the AD continuum could offer avenues for precision medicine.

Cross-sectional Associations of β-Amyloid, Tau, and Cerebrovascular Biomarkers With Neurodegeneration in Probable Dementia With Lewy Bodies

BACKGROUND AND OBJECTIVES

Although alpha-synuclein-related pathology is the hallmark of dementia with Lewy bodies (DLB), cerebrovascular and Alzheimer disease pathologies are common in patients with DLB. Little is known about the contribution of these pathologies to neurodegeneration in DLB. We investigated associations of cerebrovascular, β-amyloid, and tau biomarkers with gray matter (GM) volume in patients with probable DLB.

METHODS

We assessed patients with probable DLB and cognitively unimpaired (CU) controls with 11C-Pittsburgh compound B (PiB) and 18F-flortaucipir PET as markers of β-amyloid and tau, respectively. MRI was used to assess white matter hyperintensity (WMH) volume (a marker of cerebrovascular lesion load) and regional GM volume (a marker of neurodegeneration). We used correlations and analysis of covariance (ANCOVA) in the entire cohort and structural equation models (SEMs) in patients with DLB to investigate associations of WMH volume and regional β-amyloid and tau PET standardized uptake value ratios (SUVrs) with regional GM volume.

RESULTS

We included 30 patients with DLB (69.3 ± 10.2 years, 87% men) and 100 CU controls balanced on age and sex. Compared with CU controls, patients with DLB showed a lower GM volume across all cortical and subcortical regions except for the cuneus, putamen, and pallidum. A larger WMH volume was associated with a lower volume in the medial and orbital frontal cortices, insula, fusiform cortex, and thalamus in patients with DLB. A higher PiB SUVr was associated with a lower volume in the inferior temporal cortex, while flortaucipir SUVr did not correlate with GM volume. SEMs showed that a higher age and absence of the APOE ε4 allele were significant predictors of higher WMH volume, and WMH volume in turn was a significant predictor of GM volume in medial and orbital frontal cortices, insula, and inferior temporal cortex. By contrast, we observed 2 distinct paths for the fusiform cortex, with age having an effect through PiB and flortaucipir SUVr on one path and through WMH volume on the other path.

DISCUSSION

Patients with probable DLB have widespread cortical atrophy, most of which is likely influenced by alpha-synuclein-related pathology. Although cerebrovascular, β-amyloid, and tau pathologies often coexist in probable DLB, their contributions to neurodegeneration seem to be region specific.

Sex differences in grey matter networks in dementia with Lewy bodies

Objectives

Sex differences permeate many aspects of dementia with Lewy bodies (DLB), including epidemiology, pathogenesis, disease progression, and symptom manifestation. However, less is known about potential sex differences in patterns of neurodegeneration in DLB. Here, we test whether grey matter networks also differ between female and male DLB patients. To assess the specificity of these sex differences to DLB, we additionally investigate sex differences in healthy controls (HCs).

Methods

A total of 119 (68.7 ± 8.4 years) male and 45 female (69.9 ± 9.1 years) DLB patients from three European centres and the Mayo Clinic were included in this study. Additionally, we included 119 male and 45 female age-matched HCs from the Mayo Clinic. Grey matter volumes of 58 cortical, subcortical, cerebellar, and pontine brain regions derived from structural magnetic resonance images were corrected for age, intracranial volume, and centre. Sex-specific grey matter networks for DLB patients and HCs were constructed by correlating each pair of brain regions. Network properties of the correlation matrices were compared between sexes and groups. Additional analyses were conducted on W-scored data to identify DLB-specific findings.

Results

Networks of male HCs and male DLB patients were characterised by a lower nodal strength compared to their respective female counterparts. In comparison to female HCs, the grey matter networks of male HCs showed a higher global efficiency, modularity, and a lower number of modules. None of the global and nodal network measures showed significant sex differences in DLB.

Conclusions

The disappearance of sex differences in the structural grey matter networks of DLB patients compared to HCs may indicate a sex-dependent network vulnerability to the alpha-synuclein pathology in DLB. Future studies might investigate whether the differences in structural network measures are associated with differences in cognitive scores and clinical symptoms between the sexes.

Sex differences in brain atrophy in dementia with Lewy bodies

Background and objectives

Sex is an important contributing factor to neuroimaging phenotypes in brain disorders. However, little is known about the contribution of sex differences to the neurodegeneration in dementia with Lewy bodies (DLB). We investigated sex differences in probable DLB patients by using both visual rating scales of lobar atrophy and automated estimations of regional atrophy.

Methods

We included 442 probable DLB patients from the European-DLB consortium and the Mayo Clinic who have magnetic resonance imaging (MRI) data available. We assessed sex differences and the sex-by-age interaction in two largely independent samples through visual rating scales of lobar atrophy (n = 333; mean age 73 ± 8 years, 62% males) and automated regional estimations of gray matter (GM) volume and mean cortical thickness (CTh) (n = 165; mean age 69 ± 9 years, 72% males). We used binary logistic regression and ANOVA for statistical analysis.

Results

We found a statistically significantly higher likelihood of frontal atrophy measured by the global cortical atrophy-frontal subscale (GCA-F) in males (40% of males had an abnormal GCA-F score versus 29% of females, P-value = 0.006). Using automated estimations, we found smaller GM volumes in 6 cortical regions in males compared with females, as well as smaller GM volume in the entorhinal cortex and thinner olfactory cortices in females, compared with males. The sex-by-age interaction showed statistically significant results in 6 cortical volumes and 7 mean CTh estimations (P-value ≤ 0.05), accentuated in the right middle frontal gyrus (FDR-adjusted P-value = 0.047). These cross-sectional interactions indicated that while females have statistically significantly less atrophy than males at younger ages, differences become non-significant at older ages, with females showing the same level of atrophy than males around the age of 75.

Conclusions

This study demonstrates sex differences on brain atrophy in probable DLB. While male DLB patients have a more widespread pattern of cortical atrophy at younger ages, these sex differences tend to disappear with increasing age. Longitudinal studies will help establish these cross-sectional findings and inform on sex and age considerations to the use of MRI in clinical routine, as the field moves towards precision medicine.

The block design subtest of the Wechsler adult intelligence scale as a possible non-verbal proxy of cognitive reserve

Objectives

To investigate the potential of the Block design subtest of the Wechsler Adults Intelligence Scale as a non-verbal proxy of cognitive reserve.

Method

A total of 391 cognitively unimpaired participants were included in this study. The association between the Block design subtest and the Information subtest (an established verbal proxy of cognitive reserve) from the WAIS, as well as the association of the two subtests with a Cognitive Reserve Questionnaire (CRQ) were tested. In addition, multiple linear regression models were conducted to investigate the association of the Block design and Information subtests with cognitive performance. The capacity of the Block design subtest to minimize the negative effect of an older age over cognitive performance was also assessed and this effect was compared with that of the Information subtest. The four cognitive domains included were: verbal memory, visual-visuospatial memory, executive-premotor functions and processing speed.

Results

The Block design subtest correlated positively with both the Information subtest and the CRQ. A statistically significant association was observed between the Block design subtest and all four cognitive domains. Higher scores in the Block design subtest minimized the negative effect of aging on the cognitive domains of visual-visuospatial memory and executive-premotor functions, in a similar way to the results obtained for the Information subtest.

Conclusion

The Block design subtest is significantly correlated with two established proxies of cognitive reserve: it correlates with cognitive performance and high scores in Block design have the capacity to minimize the negative effect of an older age on cognitive performance. Therefore, the results suggest that the corrected Block design subtest could be considered as a non-verbal proxy of cognitive reserve.

Dementia with Lewy bodies: Impact of co-pathologies and implications for clinical trial design

Dementia with Lewy bodies (DLB) is clinically defined by the presence of visual hallucinations, fluctuations, rapid eye movement (REM) sleep behavioral disorder, and parkinsonism. Neuropathologically, it is characterized by the presence of Lewy pathology. However, neuropathological studies have demonstrated the high prevalence of coexistent Alzheimer's disease, TAR DNA-binding protein 43 (TDP-43), and cerebrovascular pathologic cases. Due to their high prevalence and clinical impact on DLB individuals, clinical trials should account for these co-pathologies in their design and selection and the interpretation of biomarkers values and outcomes. Here we discuss the frequency of the different co-pathologies in DLB and their cross-sectional and longitudinal clinical impact. We then evaluate the utility and possible applications of disease-specific and disease-nonspecific biomarkers and how co-pathologies can impact these biomarkers. We propose a framework for integrating multi-modal biomarker fingerprints and step-wise selection and assessment of DLB individuals for clinical trials, monitoring target engagement, and interpreting outcomes in the setting of co-pathologies.

(Dis-)Connected Dots in Dementia with Lewy Bodies-A Systematic Review of Connectivity Studies

Studies on dementia with Lewy bodies (DLB) have mainly focused on the degeneration of distinct cortical and subcortical regions related to the deposition of Lewy bodies. In view of the proposed trans-synaptic spread of the α-synuclein pathology, investigating the disease only in this segregated fashion would be detrimental to our understanding of its progression. In this systematic review, we summarize findings on structural and functional brain connectivity in DLB, as connectivity measures may offer better insights on how the brain is affected by the spread of the pathology. Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we searched Web of Science, PubMed, and SCOPUS for relevant articles published up to November 1, 2021. Of 1215 identified records, we selected and systematically reviewed 53 articles that compared connectivity features between patients with DLB and healthy controls. Structural and functional magnetic resonance imaging, positron emission tomography, single-positron emission computer tomography, and electroencephalography assessments of patients revealed widespread abnormalities within and across brain networks in DLB. Frontoparietal, default mode, and visual networks and their connections to other brain regions featured the most consistent disruptions, which were also associated with core clinical features and cognitive impairments. Furthermore, graph theoretical measures revealed disease-related decreases in local and global network efficiency. This systematic review shows that structural and functional connectivity characteristics in DLB may be particularly valuable at early stages, before overt brain atrophy can be observed. This knowledge may help improve the diagnosis and prognosis in DLB as well as pinpoint targets for future disease-modifying treatments. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

The hippocampal sparing subtype of Alzheimer's disease assessed in neuropathology and in vivo tau positron emission tomography: a systematic review

Neuropathology and neuroimaging studies have identified several subtypes of Alzheimer's disease (AD): hippocampal sparing AD, typical AD, and limbic predominant AD. An unresolved question is whether hippocampal sparing AD cases can present with neurofibrillary tangles (NFT) in association cortices while completely sparing the hippocampus. To address that question, we conducted a systematic review and performed original analyses on tau positron emission tomography (PET) data. We searched EMBASE, PubMed, and Web of Science databases until October 2022. We also implemented several methods for AD subtyping on tau PET to identify hippocampal sparing AD cases. Our findings show that seven out of the eight reviewed neuropathologic studies included cases at Braak stages IV or higher and therefore, could not identify hippocampal sparing cases with NFT completely sparing the hippocampus. In contrast, tau PET did identify AD participants with tracer retention in the association cortex while completely sparing the hippocampus. We conclude that tau PET can identify hippocampal sparing AD cases with NFT completely sparing the hippocampus. Based on the accumulating data, we suggest two possible pathways of tau spread: (1) a canonical pathway with early involvement of transentorhinal cortex and subsequent involvement of limbic regions and association cortices, and (2) a less common pathway that affects association cortices with limbic involvement observed at end stages of the disease or not at all.

Cholinergic white matter pathways along the Alzheimer's disease continuum

Previous studies have shown that the cholinergic nucleus basalis of Meynert and its white matter projections are affected in Alzheimer’s disease (AD) dementia and mild cognitive impairment (MCI). However, it is still unknown if these alterations can be found in individuals with subjective cognitive decline (SCD), and whether they are more pronounced than changes found in conventional brain volumetric measurements. To address these questions, we investigated microstructural alterations of two major cholinergic pathways in individuals along the AD continuum using an in vivo model of the human cholinergic system based on neuroimaging.

We included 405 participants (53 AD, 66 MCI, 174 SCD, and 112 healthy controls) from the Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE) Longitudinal Cognitive Impairment and Dementia Study (DELCODE). We modelled the cholinergic white matter pathways with an enhanced diffusion neuroimaging pipeline that included probabilistic fiber-tracking methods and prior anatomical knowledge. The integrity of the cholinergic white matter pathways was compared between stages of the AD continuum, in the whole cohort and in a CSF amyloid-beta stratified subsample. The discriminative power of the integrity of the pathways was compared to the conventional volumetric measures of hippocampus and nucleus basalis of Meynert, using a receiver operating characteristics analysis. A multivariate model was employed to investigate the role of these pathways in relation to cognitive performance.

We found that the integrity of the cholinergic white matter pathways was significantly reduced in all stages of the AD continuum, including individuals with SCD. The differences involved posterior cholinergic white matter in the SCD stage and extended to anterior frontal white matter in MCI and AD dementia stages. Both cholinergic pathways and conventional volumetric measures showed higher predictive power in the more advanced stages of the disease, i.e., MCI and AD dementia. In contrast, the integrity of cholinergic pathways was more informative in distinguishing SCD from healthy controls, as compared with the volumetric measures. The multivariate model revealed a moderate contribution of the cholinergic white matter pathways but not of volumetric measures towards memory tests in the SCD and MCI stages.

In conclusion, we demonstrated that cholinergic white matter pathways are altered already in SCD individuals, preceding the more widespread alterations found in MCI and AD. The integrity of the cholinergic pathways identified the early stages of AD better than conventional volumetric measures such as hippocampal volume or volume of cholinergic nucleus basalis of Meynert.

Prevalence and predictors of acquired long QT syndrome in the ER department

Introduction

Long QT syndrome (LQTS) is a rare heterogeneous syndrome that may be congenital or acquired, the latter being more common. Its real-world prevalence remains to be determined. We aimed to determine the prevalence of this syndrome in patients admitted to the emergency room (ER) and characterize the subset of patients with severely prolonged QT.

Methods

A retrospective analysis of ECG of all consecutively admitted patients in the ER of a tertiary hospital between the 28th of January and the 17th of March 2020 was made. All patients with Bazzett corrected QT interval greater than 470ms in men and 480ms in women were included. Repeated ECGs or with bad electrocardiographic quality, congenital LQTS, atrial fibrillation and pacemaker rhythm were excluded. Clinical data with a special focus on QT prolonging drugs and clinical factors were recorded. Statistical comparison was made between the groups with and without QT interval greater than 500ms.

Results

A total of 6280 ECGs of 5056 patients were analysed. After evaluation, 390 ECGs from 387 different patients were considered. Prevalence of LQTS at admission was 7.95%. Patients were more commonly men (53.1%) with an average age of 73.6±14.7 years old and mean QTc interval of 502.14±32.2ms. Only 20% of the patients were symptomatic, with the most common form of presentation being syncope (50%). No ventricular arrhythmias were recorded.

Regarding patients with a QT interval greater than 500ms, these were more frequently female (59.9% vs 37.2%, p&lt;0.001), were more frequently on QT prolonging drugs (77.8% vs 67.3%; p=0.002). Presence of clinical risk factors was not a risk factor per se (p=0.811) but a greater number of risk factors was linked to more severely prolonged QT (p=0.040). The main contributing factor was intake of antibiotics (odds ratio (OR) 3.497; CI 95% 1.074–11.321; p=0.038) followed by female gender (OR 2.518; CI 95% 1.668–3.800; p&lt;0.001) and use of antipsychotics (OR 1.960; CI 95% 1.159–3.316; p=0.012).

Conclusions

Acquired LQTS is particularly prevalent in the ER setting. The complex interaction of clinical factors and drug iatrogenesis and the unpredictability of its manifestations render its management and recognition difficult but essential. Female patients on antibiotics and antipsychotics are at particularly high risk. Efforts must be made in order to avoid, detect and treat acquired LQTS as early as possible.

Funding Acknowledgement

Type of funding sources: None.

Management of Refractory Status Epilepticus: An International Cohort Study (MORSE CODe) Analysis of Patients Managed in the ICU

BACKGROUND AND OBJECTIVES

Status epilepticus that continues after the initial benzodiazepine and a second anticonvulsant medication is known as refractory status epilepticus (RSE). Management is highly variable because adequately powered clinical trials are missing. We aimed to determine whether propofol and midazolam were equally effective in controlling RSE in the intensive care unit, focusing on management in resource-limited settings.

METHODS

Patients with RSE treated with midazolam or propofol between January 2015 and December 2018 were retrospectively identified among 9 centers across 4 continents from upper-middle-income economies in Latin America and high-income economies in North America, Europe, and Asia. Demographics, Status Epilepticus Severity Score, etiology, treatment details, and discharge modified Rankin Scale (mRS) were collected. The primary outcome measure was good functional outcome defined as a mRS score of 0-2 at hospital discharge.

RESULTS

Three hundred eighty-seven episodes of RSE (386 patients) were included, with 162 (42%) from upper-middle-income and 225 (58%) from high-income economies. Three hundred six (79%) had acute and 79 (21%) remote etiologies. Initial RSE management included midazolam in 266 (69%) and propofol in 121 episodes (31%). Seventy episodes (26%) that were initially treated with midazolam and 42 (35%) with propofol required the addition of a second anesthetic to treat RSE. Baseline characteristics and outcomes of patients treated with midazolam or propofol were similar. Breakthrough (odds ratio [OR] 1.6, 95% CI 1.3-2.0) and withdrawal seizures (OR 2.0, 95% CI 1.7-2.5) were associated with an increased number of days requiring continuous intravenous anticonvulsant medications (cIV-ACMs). Prolonged EEG monitoring was associated with fewer days of cIV-ACMs (1-24 hours OR 0.5, 95% CI 0.2-0.9, and >24 hours OR 0.7, 95% CI 0.5-1.0; reference EEG <1 hour). This association was seen in both, high-income and upper-middle-income economies, but was particularly prominent in high-income countries. One hundred ten patients (28%) were dead, and 80 (21%) had good functional outcomes at hospital discharge.

DISCUSSION

Outcomes of patients with RSE managed in the intensive care unit with propofol or midazolam infusions are comparable. Prolonged EEG monitoring may allow physicians to decrease the duration of anesthetic infusions safely, but this will depend on the implementation of RSE management protocols. Goal-directed management approaches including EEG targets may hold promise for patients with RSE.

CLASSIFICATION OF EVIDENCE

This study provides Class III data that propofol and midazolam are equivalently efficacious for RSE.

Parent-reported toothbrushing behaviour in the Portuguese preschool population

PURPOSE

Study toothbrushing behaviours and associated factors in a Portuguese preschool population.

METHODS

The study population was the parents of children attending Portuguese kindergartens. The data on sociodemographic and toothbrushing behaviours, at home and at school, were collected by an online questionnaire. The data analysis was performed using Chi-square, Fisher, Mann-Whitney and Kruskal-Wallis tests (α = 0.05).

RESULTS

The sample included 711 parents. Most of the children brushed their teeth at home at least twice-a-day (65.3%), with the help of an adult (62.9%). The majority of the children did not brush their teeth at school (71.2%); however, only 9.9% of the parents reported that they don't/wouldn't authorise it. Considering both toothbrushing, at home and at school, 75% of the children brushed their teeth twice-a-day. However, only 7.8% of the children performed all the correct toothbrushing related procedures. Toothbrushing at school was more frequent in private kindergartens (p < 0.001). A higher level of education was associated with non-authorisation of toothbrushing at school (p = 0.019) and with performing the correct toothbrushing related procedures (p = 0.007). Attending an oral health professional appointment was also associated with performing the correct toothbrushing related procedures (p = 0.005).

CONCLUSION

Toothbrushing twice-a-day was frequent in the studied population, however, the percentage of children who brushed at school was low, as well as the percentage of children who performed all the correct toothbrushing related procedures. Toothbrushing at school was more likely in private kindergartens. Performing correct toothbrushing related procedures was more frequent in children who had a previous oral health appointment and whose parents had a higher education level.

Multi-cohort and longitudinal Bayesian clustering study of stage and subtype in Alzheimer's disease

Understanding Alzheimer's disease (AD) heterogeneity is important for understanding the underlying pathophysiological mechanisms of AD. However, AD atrophy subtypes may reflect different disease stages or biologically distinct subtypes. Here we use longitudinal magnetic resonance imaging data (891 participants with AD dementia, 305 healthy control participants) from four international cohorts, and longitudinal clustering to estimate differential atrophy trajectories from the age of clinical disease onset. Our findings (in amyloid-β positive AD patients) show five distinct longitudinal patterns of atrophy with different demographical and cognitive characteristics. Some previously reported atrophy subtypes may reflect disease stages rather than distinct subtypes. The heterogeneity in atrophy rates and cognitive decline within the five longitudinal atrophy patterns, potentially expresses a complex combination of protective/risk factors and concomitant non-AD pathologies. By alternating between the cross-sectional and longitudinal understanding of AD subtypes these analyses may allow better understanding of disease heterogeneity.

Association of Cerebrovascular and Alzheimer Disease Biomarkers With Cholinergic White Matter Degeneration in Cognitively Unimpaired Individuals

OBJECTIVES

Several pathological processes might contribute to the degeneration of the cholinergic system in aging. We aimed to determine the contribution of amyloid, tau, and cerebrovascular biomarkers towards the degeneration of cholinergic white matter (WM) projections in cognitively unimpaired individuals.

METHODS

The contribution of amyloid and tau pathology was assessed through cerebrospinal fluid (CSF) levels of the Aβ_42/40 ratio and phosphorylated tau (p-tau). CSF Aβ₃₈ levels were also measured. Cerebrovascular pathology was assessed using automatic segmentations of WM lesions on magnetic resonance imaging (MRI). Cholinergic WM projections (i.e., cingulum and external capsule pathways) were modeled using tractography based on diffusion tensor imaging data. Sex and APOE 𝜀4 carriership were also included in the analysis as variables of interest.

RESULTS

We included 203 cognitively unimpaired individuals from the H70 Gothenburg Birth Cohort Studies (all individuals 70 years old, 51% female). WM lesion burden was the most important contributor to the degeneration of both cholinergic pathways (Increase in mean square error (IncMSE)=98.8% in external capsule pathway and IncMSE=93.3% in the cingulum pathway). Levels of Aβ₃₈ and p-tau also contributed to cholinergic white matter degeneration, especially in the external capsule pathway (IncMSE=28.4% and IncMSE=23.4%, respectively). The Aβ_42/40 ratio did not contribute notably to the models (IncMSE<3.0%). APOE 𝜀4 carriers showed poorer integrity in the cingulum pathway (IncMSE=21.33%). Women showed poorer integrity of the external capsule pathway (IncMSE=21.55%), which was independent of amyloid status as reflected by the non-significant differences in integrity when comparing amyloid positive versus amyloid negative women participants (T₂₀₁=-1.55; p=0.123).

CONCLUSIONS

In cognitively unimpaired older individuals, WM lesions play a central role in the degeneration of cholinergic pathways. Our findings highlight the importance of WM lesion burden in the elderly population, which should be considered in the development of prevention programs for neurodegeneration and cognitive impairment.

Neuropathologic Features of Antemortem Atrophy-Based Subtypes of Alzheimer Disease

BACKGROUND AND OBJECTIVES

To investigate whether antemortem MRI-based atrophy subtypes of Alzheimer disease (AD) differ in neuropathologic features and comorbid non-AD pathologies at postmortem.

METHODS

From the Alzheimer's Disease Neuroimaging Initiative cohort, we included individuals with antemortem MRI evaluating brain atrophy within 2 years before death, antemortem diagnosis of AD dementia/mild cognitive impairment, and postmortem-confirmed AD neuropathologic change. Antemortem atrophy subtypes were modeled as continuous phenomena based on a recent conceptual framework: typicality (spanning limbic-predominant AD to hippocampal-sparing AD) and severity (spanning typical AD to minimal atrophy AD). Postmortem neuropathologic evaluation included AD hallmarks, β-amyloid, and tau as well as non-AD pathologies, alpha-synuclein and TAR DNA-binding protein 43 (TDP-43). We also investigated the overall concomitance across these pathologies. Partial correlations assessed the associations between antemortem atrophy subtypes and postmortem neuropathologic outcomes.

RESULTS

In 31 individuals (26 AD dementia/5 mild cognitive impairment, mean age = 80 years, 26% females), antemortem typicality was significantly negatively associated with neuropathologic features, including β-amyloid (rho = -0.39 overall), tau (rho = -0.38 regionally), alpha-synuclein (rho = -0.39 regionally), TDP-43 (rho = -0.49 overall), and concomitance of pathologies (rho = -0.59 regionally). Limbic-predominant AD was associated with higher Thal phase, neuritic plaque density, and presence of TDP-43 compared with hippocampal-sparing AD. Regionally, limbic-predominant AD showed a higher presence of tau and alpha-synuclein pathologies in medial temporal structures, a higher presence of TDP-43, and concomitance of pathologies subcortically/cortically compared with hippocampal-sparing AD. Antemortem severity was significantly negatively associated with concomitance of pathologies (rho = -0.43 regionally), such that typical AD showed higher concomitance of pathologies than minimal atrophy AD.

DISCUSSION

We provide a direct antemortem-to-postmortem validation, highlighting the importance of understanding atrophy-based heterogeneity in AD relative to AD and non-AD pathologies. We suggest that (1) typicality and severity in atrophy reflect differential aspects of susceptibility of the brain to AD and non-AD pathologies; and (2) limbic-predominant AD and typical AD subtypes share similar biological pathways, making them more vulnerable to AD and non-AD pathologies compared with hippocampal-sparing AD, which may follow a different biological pathway. Our findings provide a deeper understanding of associations of atrophy subtypes in AD with different pathologies, enhancing the prevailing knowledge of biological heterogeneity in AD and could contribute toward tracking disease progression and designing clinical trials in the future.