Pharmacotherapies for the Treatment of Progressive Supranuclear Palsy: A Narrative Review.

Progressive supranuclear palsy (PSP) is a neurodegenerative disorder resulting from the deposition of misfolded and neurotoxic forms of tau protein in specific areas of the midbrain, basal ganglia, and cortex. It is one of the most representative forms of tauopathy. PSP presents in several different phenotypic variations and is often accompanied by the development of concurrent neurodegenerative disorders. PSP is universally fatal, and effective disease-modifying therapies for PSP have not yet been identified. Several tau-targeting treatment modalities, including vaccines, monoclonal antibodies, and microtubule-stabilizing agents, have been investigated and have had no efficacy. The need to treat PSP and other tauopathies is critical, and many clinical trials investigating tau-targeted treatments are underway. In this review, the PubMed database was queried to collect information about preclinical and clinical research on PSP treatment. Additionally, the US National Library of Medicine's ClinicalTrials.gov website was queried to identify past and ongoing clinical trials relevant to PSP treatment. This narrative review summarizes our findings regarding these reports, which include potential disease-modifying drug trials, modifiable risk factor management, and symptom treatments.

Updated safety results from phase 3 lecanemab study in early Alzheimer's disease.

BACKGROUND: Alzheimer disease (AD) is a major health problem of aging, with tremendous burden on healthcare systems, patients, and families globally. Lecanemab, an FDA-approved amyloid beta (Aß)-directed antibody indicated for the treatment of early AD, binds with high affinity to soluble Aß protofibrils, which have been shown to be more toxic to neurons than monomers or insoluble fibrils. Lecanemab has been shown to be well tolerated in multiple clinical trials, although risks include an increased rate of amyloid-related imaging abnormalities (ARIA) and infusion reactions relative to placebo. METHODS: Clarity AD was an 18-month treatment (Core study), multicenter, double-blind, placebo-controlled, parallel-group study with open-label extension (OLE) in participants with early AD. Eligible participants were randomized 1:1 across 2 treatment groups (placebo and lecanemab 10 mg/kg biweekly). Safety evaluations included monitoring of vital signs, physical examinations, adverse events, clinical laboratory parameters, and 12-lead electrocardiograms. ARIA occurrence was monitored throughout the study by magnetic resonance imaging, read both locally and centrally. RESULTS: Overall, 1795 participants from Core and 1612 participants with at least one dose of lecanemab (Core + OLE) were included. Lecanemab was generally well-tolerated in Clarity AD, with no deaths related to lecanemab in the Core study. There were 9 deaths during the OLE, with 4 deemed possibly related to study treatment. Of the 24 deaths in Core + OLE, 3 were due to intracerebral hemorrhage (ICH): 1 placebo in the Core due to ICH, and 2 lecanemab in OLE with concurrent ICH (1 on tissue plasminogen activator and 1 on anticoagulant therapy). In the Core + OLE, the most common adverse events in the lecanemab group (> 10%) were infusion-related reactions (24.5%), ARIA with hemosiderin deposits (ARIA-H) microhemorrhages (16.0%), COVID-19 (14.7%), ARIA with edema (ARIA-E; 13.6%), and headache (10.3%). ARIA-E and ARIA-H were largely radiographically mild-to-moderate. ARIA-E generally occurred within 3-6 months of treatment, was more common in ApoE e4 carriers (16.8%) and most common in ApoE ε4 homozygous participants (34.5%). CONCLUSIONS: Lecanemab was generally well-tolerated, with the most common adverse events being infusion-related reactions, ARIA-H, ARIA-E. Clinicians, participants, and caregivers should understand the incidence, monitoring, and management of these events for optimal patient care. TRIAL REGISTRATION: ClinicalTrials.gov numbers: Clarity AD NCT03887455).

Conjugal Synucleinopathies: A Clinicopathologic Study.

BACKGROUND: While preclinical studies have shown that alpha-synuclein can spread through cell-to-cell transmission whether it can be transmitted between humans is unknown. OBJECTIVES: The aim was to assess the presence of a synucleinopathy in autopsied conjugal couples. METHODS: Neuropathological findings in conjugal couples were categorized as Parkinson's disease (PD), dementia with Lewy bodies (DLB), Alzheimer's disease with Lewy bodies (ADLB), incidental Lewy body disease (ILBD), or no Lewy bodies. RESULTS: Ninety conjugal couples were included; the mean age of death was 88.3 years; 32 couples had no Lewy bodies; 42 couples had 1 spouse with a synucleinopathy: 10 PD, 3 DLB, 13 ADLB, and 16 ILBD; 16 couples had both spouses with a synucleinopathy: in 4 couples both spouses had PD, 1 couple had PD and DLB, 4 couples had PD and ADLB, 2 couples had PD and ILBD, 1 couple had DLB and ADLB, in 3 couples both had ADLB, and 1 couple had ADLB and ILBD. No couples had both spouses with ILBD. CONCLUSIONS: This large series of 90 autopsied conjugal couples found 16 conjugal couples with synucleinopathies, suggesting transmission of synucleinopathy between spouses is unlikely. © 2024 International Parkinson and Movement Disorder Society.

Altered resting-state functional connectivity and dynamic network properties in cognitive impairment: an independent component and dominant-coactivation pattern analyses study.

Introduction: Cognitive impairment (CI) due to Alzheimer's disease (AD) encompasses a decline in cognitive abilities and can significantly impact an individual's quality of life. Early detection and intervention are crucial in managing CI, both in the preclinical and prodromal stages of AD prior to dementia. Methods: In this preliminary study, we investigated differences in resting-state functional connectivity and dynamic network properties between 23 individual with CI due to AD based on clinical assessment and 15 healthy controls (HC) using Independent Component Analysis (ICA) and Dominant-Coactivation Pattern (d-CAP) analysis. The cognitive status of the two groups was also compared, and correlations between cognitive scores and d-CAP switching probability were examined. Results: Results showed comparable numbers of d-CAPs in the Default Mode Network (DMN), Executive Control Network (ECN), and Frontoparietal Network (FPN) between HC and CI groups. However, the Visual Network (VN) exhibited fewer d-CAPs in the CI group, suggesting altered dynamic properties of this network for the CI group. Additionally, ICA revealed significant connectivity differences for all networks. Spatial maps and effect size analyses indicated increased coactivation and more synchronized activity within the DMN in HC compared to CI. Furthermore, reduced switching probabilities were observed for the CI group in DMN, VN, and FPN networks, indicating less dynamic and flexible functional interactions. Discussion: The findings highlight altered connectivity patterns within the DMN, VN, ECN, and FPN, suggesting the involvement of multiple functional networks in CI. Understanding these brain processes may contribute to developing targeted diagnostic and therapeutic strategies for CI due to AD.

Impact of incidental synucleinopathy in mild cognitive impairment due to Alzheimer disease.

Recent evidence suggests that the presence of α-synuclein Lewy bodies (LBs) correlates with accelerated disease progression in patients with Alzheimer disease (AD) but it is unclear whether this effect is also exerted in the mild cognitive impairment (MCI) phase of AD. We sought to determine whether incidental LB pathology in patients with MCI due to AD is associated with a faster rate of cognitive decline compared to MCI controls without LB pathology. We identified patients within the National Alzheimer's Coordinating Center (NACC) database with MCI due to AD and stratified the cohort by the presence or absence of synucleinopathy. We utilized a repeated measures longitudinal analysis of Mini-Mental State Examination (MMSE) scores to determine whether the decline in performance occurred at a greater rate in the synucleinopathy patients. A total of 206 participants were studied; 80 had coincident synucleinopathy. The rate of decline in MMSE scores between the groups did not differ. This may suggest that a synergistic effect of LB and AD neuropathology is only appreciable in the later stages of disease progression. Further investigation into the effect of mixed LB and AD pathology in the early stages of cognitive impairment is warranted to highlight opportunities for targeted early intervention in patients.

Nonmedication Devices in Development for the Treatment of Alzheimer's Disease.

 Huge investments continue to be made in treatment for Alzheimer's disease (AD), with more than one hundred drugs currently in development. Pharmacological approaches and drug development, particularly those targeting amyloid-ß, have dominated the therapeutic landscape. At the same time, there is also a growing interest in devices for treating AD. This review aimed to identify and describe devices under development for AD treatment. In this review, we queried the devices that are in development for the treatment of AD. PubMed was searched through the end of 2021 using the terms "device," "therapeutics," and "Alzheimer's" for articles that report on devices to treat AD. Ten devices with 31 references were identified as actively being developed for the treatment of AD. Many of these devices are far along in development. Device-based therapies are often overlooked when evaluating treatment approaches to AD. However, many devices for treating AD are in development and some show promising results.

Pharmacological Approaches Using Diabetic Drugs Repurposed for Alzheimer's Disease.

Type 2 diabetes mellitus (T2DM) and Alzheimer's disease (AD) are chronic, progressive disorders affecting the elderly, which fosters global healthcare concern with the growing aging population. Both T2DM and AD have been linked with increasing age, advanced glycosylation end products, obesity, and insulin resistance. Insulin resistance in the periphery is significant in the development of T2DM and it has been posited that insulin resistance in the brain plays a key role in AD pathogenesis, earning AD the name "type 3 diabetes". These clinical and epidemiological links between AD and T2DM have become increasingly pronounced throughout the years, and serve as a means to investigate the effects of antidiabetic therapies in AD, such as metformin, intranasal insulin, incretins, DPP4 inhibitors, PPAR-γ agonists, SGLT2 inhibitors. The majority of these drugs have shown benefit in preclinical trials, and have shown some promising results in clinical trials, with the improvement of cognitive faculties in participants with mild cognitive impairment and AD. In this review, we have summarize the benefits, risks, and conflicting data that currently exist for diabetic drugs being repurposed for the treatment of AD.

Rescreening on RBANS Delayed Memory Index? Forget About It!

OBJECTIVE: To assess the value of rescreening patients with Alzheimer's disease who do not meet the inclusion criteria for the Repeatable Battery for the Assessment of Neuropsychological Status Delayed Memory Index (RBANS DMI) at the initial assessment. PATIENTS AND METHODS: Participants (aged 50-85 years, without dementia, Mini-Mental State Examination score ≥22, valid Clinical Dementia Rating [CDR] global score, and amyloid status at baseline) were identified in the European Prevention of Alzheimer's Dementia database. Changes from baseline in RBANS DMI were estimated using a mixed model for repeated measurements. Logistic regressions were used to estimate the probability of participants with baseline RBANS DMI 86-95 having RBANS DMI ≤85, CDR global score ≥0.5, and amyloid positivity at 6 and 12 months. RESULTS: There was significant variability in the change in RBANS DMI scores over time (median change at 6 months: 2.0). An estimated 15% of participants with RBANS DMI 86-95 at baseline progressed to ≤85 at 6 months; 8% also achieved CDR global score ≥0.5 and 5% were also amyloid positive. CONCLUSIONS: The results from our analysis indicate that there is limited value in rescreening patients based on their initial RBANS DMI score.

ATN cerebrospinal fluid biomarkers in dementia with Lewy bodies: Initial results from the United States Dementia with Lewy Bodies Consortium.

INTRODUCTION: The National Institute on Aging - Alzheimer's Association (NIA-AA) ATN research framework proposes to use biomarkers for amyloid (A), tau (T), and neurodegeneration (N) to stage individuals with AD pathological features and track changes longitudinally. The overall aim was to utilize this framework to characterize pre-mortem ATN status longitudinally in a clinically diagnosed cohort of dementia with Lewy bodies (DLB) and to correlate it with the post mortem diagnosis. METHODS: The cohort was subtyped by cerebrospinal fluid (CSF) ATN category. A subcohort had longitudinal data, and a subgroup was neuropathologically evaluated. RESULTS: We observed a significant difference in Aß42/40 after 12 months in the A+T- group. Post mortem neuropathologic analyses indicated that most of the p-Tau 181 positive (T+) cases also had a high Braak stage. DISCUSSION: This suggests that DLB patients who are A+ but T- may need to be monitored to determine whether they remain A+ or ever progress to T positivity. HIGHLIGHTS: Some A+T- DLB subjects transition from A+ to negative after 12-months. Clinically diagnosed DLB with LBP-AD (A+T+) maintain their positivity. Clinically diagnosed DLB with LBP-AD (A+T+) maintain their positivity. Monitoring of the A+T- sub-type of DLB may be necessary.

WarpDrive: Improving spatial normalization using manual refinements.

Spatial normalization-the process of mapping subject brain images to an average template brain-has evolved over the last 20+ years into a reliable method that facilitates the comparison of brain imaging results across patients, centers & modalities. While overall successful, sometimes, this automatic process yields suboptimal results, especially when dealing with brains with extensive neurodegeneration and atrophy patterns, or when high accuracy in specific regions is needed. Here we introduce WarpDrive, a novel tool for manual refinements of image alignment after automated registration. We show that the tool applied in a cohort of patients with Alzheimer's disease who underwent deep brain stimulation surgery helps create more accurate representations of the data as well as meaningful models to explain patient outcomes. The tool is built to handle any type of 3D imaging data, also allowing refinements in high-resolution imaging, including histology and multiple modalities to precisely aggregate multiple data sources together.

Blood-based biomarkers in Alzheimer's disease: Future directions for implementation.

INTRODUCTION: Disease-modifying therapies (DMTs) for Alzheimer's disease (AD) will increase diagnostic demand. A non-invasive blood-based biomarker (BBBM) test for detection of amyloid-ß pathology may reduce diagnostic barriers and facilitate DMT initiation. OBJECTIVE: To explore heterogeneity in AD care pathways and potential role of BBBM tests. METHODS: Survey of 213 healthcare professionals/payers in US/China/UK/Germany/Spain/France and two advisory boards (US/Europe). RESULTS: Current diagnostic pathways are heterogeneous, meaning many AD patients are missed while low-risk patients undergo unnecessary procedures. Confirmatory amyloid testing (cerebrospinal fluid biomarkers/positron emission tomography) is utilized in few patients, resulting in diagnostic/treatment delays. A high negative-predictive-value test could streamline the diagnostic pathway by reducing unnecessary procedures in low-risk patients; supporting confirmatory testing where needed. Imminent approval of DMTs will increase need for fast and reliable AD diagnostic tests. DISCUSSION: An easy-to-use, accurate, non-invasive BBBM test for amyloid pathology could guide diagnostic procedures or referral, streamlining early diagnosis and DMT initiation. Highlights: This study explored AD care pathways and how BBBM may meet diagnostic demandsCurrent diagnostic pathways are heterogeneous, with country and setting variationsMany AD patients are missed, while low-risk patients undergo unnecessary proceduresAn easy-to-use, accurate, non-invasive BBBM test for amyloid pathology is neededThis test could streamline early diagnosis of amyloid pathology and DMT initiation.

Cancer drugs with high repositioning potential for Alzheimer's disease.

INTRODUCTION: Despite the recent full FDA approval of lecanemab, there is currently no disease modifying therapy (DMT) that can efficiently slow down the progression of Alzheimer's disease (AD) in the general population. This statement emphasizes the need to identify novel DMTs in the shortest time possible to prevent a global epidemic of AD cases as the world population experiences an increase in lifespan. AREAS COVERED: Here, we review several classes of anti-cancer drugs that have been or are being investigated in Phase II/III clinical trials for AD, including immunomodulatory drugs, RXR agonists, sex hormone therapies, tyrosine kinase inhibitors, and monoclonal antibodies. EXPERT OPINION: Given the overall course of brain pathologies during the progression of AD, we express a great enthusiasm for the repositioning of anti-cancer drugs as possible AD DMTs. We anticipate an increasing number of combinatorial therapy strategies to tackle AD symptoms and their underlying pathologies. However, we strongly encourage improvements in clinical trial study designs to better assess target engagement and possible efficacy over sufficient periods of drug exposure.

A New Framework for Dementia Nomenclature.

Importance: Nomenclature in the field of neurodegenerative diseases presents a challenging problem. Inconsistent use of terms such as Alzheimer disease and dementia has compromised progress in clinical care, research, and development of therapeutics. Dementia-associated stigma further contributes to inconsistent and imprecise language. The result is a lack of clarity that produces confusion with patients and the general public and presents communication challenges among researchers. Therefore, the Advisory Council on Research, Care, and Services of the National Plan to Address Alzheimer's Disease authorized a committee to make recommendations for improvement. Objective: To establish a systematic neurodegenerative disease framework for information collection and communication to standardize language usage for research, clinical, and public health purposes. Evidence Review: The Dementia Nomenclature Initiative organized into 3 major stakeholder working groups: clinicians, researchers, and the public (including individuals living with dementia and family caregivers). To inform the work, the initiative completed a narrative literature review of dementia nomenclature evolution over the last century across the PubMed, CINAHL, PsycInfo, and Scopus databases (January 1, 2000, through July 31, 2020). Initiative working groups used the results as a foundation for understanding current challenges with dementia nomenclature and implications for research, clinical practice, and public understanding. The initiative obtained additional input via focus groups with individuals living with dementia and caregivers, with separate groups for race and ethnicity (American Indian or Alaska Native, Asian or Pacific Islander, Black or African American, Hispanic or Latino, and White) as an initial assessment of the meaning of dementia-related terms to these groups. Findings: From working group deliberations, the literature review, and focus group input, the initiative developed a framework clearly separating the clinical syndromic presentation experienced by affected individuals from possible underlying pathophysiologies. In the framework, domains of clinical impairment, such as cognitive, behavioral, motor, and other neurologic features, are graded by level of impairment between none and severe. Next, biomarker information describes underlying disease processes, explains the syndrome, and identifies possible disease labels: Alzheimer disease, frontotemporal degeneration, dementia with Lewy bodies, or vascular cognitive impairment dementia. Conclusions and Relevance: The Dementia Nomenclature Initiative established a framework to guide communication about cognitive impairment among older adults. Wider testing and refinement of the framework will subsequently improve the information used in communicating about cognitive impairment and the way in which the information is used in clinical, research, and public settings.

Roadmap for C9ORF72 in Frontotemporal Dementia and Amyotrophic Lateral Sclerosis: Report on the C9ORF72 FTD/ALS Summit.

A summit held March 2023 in Scottsdale, Arizona (USA) focused on the intronic hexanucleotide expansion in the C9ORF72 gene and its relevance in frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS; C9ORF72-FTD/ALS). The goal of this summit was to connect basic scientists, clinical researchers, drug developers, and individuals affected by C9ORF72-FTD/ALS to evaluate how collaborative efforts across the FTD-ALS disease spectrum might break down existing disease silos. Presentations and discussions covered recent discoveries in C9ORF72-FTD/ALS disease mechanisms, availability of disease biomarkers and recent advances in therapeutic development, and clinical trial design for prevention and treatment for individuals affected by C9ORF72-FTD/ALS and asymptomatic pathological expansion carriers. The C9ORF72-associated hexanucleotide repeat expansion is an important locus for both ALS and FTD. C9ORF72-FTD/ALS may be characterized by loss of function of the C9ORF72 protein and toxic gain of functions caused by both dipeptide repeat (DPR) proteins and hexanucleotide repeat RNA. C9ORF72-FTD/ALS therapeutic strategies discussed at the summit included the use of antisense oligonucleotides, adeno-associated virus (AAV)-mediated gene silencing and gene delivery, and engineered small molecules targeting RNA structures associated with the C9ORF72 expansion. Neurofilament light chain, DPR proteins, and transactive response (TAR) DNA-binding protein 43 (TDP-43)-associated molecular changes were presented as biomarker candidates. Similarly, brain imaging modalities (i.e., magnetic resonance imaging [MRI] and positron emission tomography [PET]) measuring structural, functional, and metabolic changes were discussed as important tools to monitor individuals affected with C9ORF72-FTD/ALS, at both pre-symptomatic and symptomatic disease stages. Finally, summit attendees evaluated current clinical trial designs available for FTD or ALS patients and concluded that therapeutics relevant to FTD/ALS patients, such as those specifically targeting C9ORF72, may need to be tested with composite endpoints covering clinical symptoms of both FTD and ALS. The latter will require novel clinical trial designs to be inclusive of all patient subgroups spanning the FTD/ALS spectrum.

The C9ORF72 Summit was held in March 2023 in Scottsdale, Arizona (USA). Some people who have the disease frontotemporal dementia or the disease amyotrophic lateral sclerosis have a change in one of their genes; the name of the gene is C9ORF72. People who carry this genetic difference usually inherited it from a parent. Researchers are improving their understanding of how the change in the C9ORF72 gene affects people, and efforts are being made to use this knowledge to develop treatments for amyotrophic lateral sclerosis and frontotemporal dementia. In addition to studying the cellular and molecular mechanisms of how the C9ORF72 mutation leads to cellular dysfunction and frontotemporal dementia and amyotrophic lateral sclerosis clinical symptoms, a large effort of the research community is aimed at developing measurements, called biomarkers, that could enhance therapy development efforts in multiple ways. Examples include monitoring of disease activity, identifying those at risk of developing amyotrophic lateral sclerosis or frontotemporal dementia, predicting which people might benefit from a particular treatment, and showing that a drug has had a biological effect. Markers that identify healthy people who are at risk of developing amyotrophic lateral sclerosis or frontotemporal dementia could be used to test treatments that would start before a person shows any symptoms and hopefully would delay or even prevent their onset.

Type 2 Diabetes Comorbidity and Cognitive Decline in Patients with Alzheimer's Disease.

BACKGROUND: Although insulin dysregulation and resistance likely participate in Alzheimer's disease (AD) etiologies, little is known about the correlation between type 2 diabetes mellitus (T2DM) and the progression of cognitive decline in patients with AD. OBJECTIVE: To determine whether AD patients with T2DM experience more rapid cognitive decline than those without T2DM. METHODS: All cognitive performance data and the presence or absence of T2DM comorbidity in patients with AD were derived from the US National Alzheimer's Coordinating Center's (NACC) Uniform Data Set (UDS). A search of the UDS identified 3,055 participants with AD who had more than one epoch completed. The data set culled clinically diagnosed AD dementia patients who were assessed for diabetes type identified during at least 1 visit. These patients were divided into 2 groups based on whether they had a diagnosis of T2DM. The data from these groups were then analyzed for differences in cognitive decline based on neuropsychological test battery scores and a Clinician Dementia Rating using a general linear model. RESULTS: Comparisons of the mean scores for 16 selected tests from the neuropsychological test battery showed no significant differences in baseline scores and scores at subsequent visits between the T2DM and nondiabetic groups. CONCLUSIONS: The results revealed no differences in cognitive decline metrics over the course of 5 visits in either study group. These data indicate that the presence of T2DM does not increase the rate of cognitive decline in AD. This finding contradicts expected disease burden and will need to be explored further.

A Randomized Double-blind Study to Assess the Skin Irritation and Sensitization Potential of a Once-weekly Donepezil Transdermal Delivery System in Healthy Volunteers.

BACKGROUND: A once-weekly donepezil transdermal delivery system (TDS; Adlarity; Corium, LLC) is indicated for the treatment of mild, moderate, and severe dementia of the Alzheimer type. METHODS: In this placebo-controlled, randomized, double-blind phase 1 trial, healthy volunteers aged 40 years or older were randomized to receive a placebo and donepezil TDS and were evaluated for the primary endpoints of skin irritation and sensitization potential. Skin irritation was scored. RESULTS: Two hundred fifty-six participants were randomized and received ≥1 dose of any treatment. After the first weekly TDS application, no skin irritation or minimal irritation was evident between donepezil and placebo TDSs. At the third weekly TDS application, for donepezil TDS, the average of the mean combined skin irritation score was 0.55 of a possible maximum of 7, indicating none to minimal skin irritation, and for placebo, the score was 0.19, indicating no skin irritation. Of 198 participants, 4 (2.0%) were considered potentially sensitized to donepezil TDS, and 0 were potentially sensitized to placebo TDS. CONCLUSION: Once-weekly 5-mg/d donepezil TDS demonstrated minimal skin irritation under conditions of use of 3 consecutive weekly patch applications to the same skin site and minimal sensitization potential.

Cerebral white matter rarefaction has both neurodegenerative and vascular causes and may primarily be a distal axonopathy.

Cerebral white matter rarefaction (CWMR) was considered by Binswanger and Alzheimer to be due to cerebral arteriolosclerosis. Renewed attention came with CT and MR brain imaging, and neuropathological studies finding a high rate of CWMR in Alzheimer disease (AD). The relative contributions of cerebrovascular disease and AD to CWMR are still uncertain. In 1181 autopsies by the Arizona Study of Aging and Neurodegenerative Disorders (AZSAND), large-format brain sections were used to grade CWMR and determine its vascular and neurodegenerative correlates. Almost all neurodegenerative diseases had more severe CWMR than the normal control group. Multivariable logistic regression models indicated that Braak neurofibrillary stage was the strongest predictor of CWMR, with additional independently significant predictors including age, cortical and diencephalic lacunar and microinfarcts, body mass index, and female sex. It appears that while AD and cerebrovascular pathology may be additive in causing CWMR, both may be solely capable of this. The typical periventricular pattern suggests that CWMR is primarily a distal axonopathy caused by dysfunction of the cell bodies of long-association corticocortical projection neurons. A consequence of these findings is that CWMR should not be viewed simply as "small vessel disease" or as a pathognomonic indicator of vascular cognitive impairment or vascular dementia.