Faculty Bibliography

OBJECTIVES/OBJECTIVE:Anti-amyloid-beta immunotherapy requires frequent MRI screening for amyloid-related imaging abnormalities-hemorrhage subtype (ARIA-H), consisting of cerebral microbleeds (CMB) and/or superficial siderosis (SS), using gradient-recalled echo (GRE) or susceptibility-weighted imaging (SWI). Screening MRI sequences for ARIA-H may benefit from acceleration to maximize patient enrollment by increased throughput and reduced motion degradation. This study assessed the diagnostic performance of standard GRE and SWI to echo-planar imaging (EPI) accelerated substitutions for detecting CMB and SS. MATERIALS AND METHODS/METHODS:This retrospective single-center rater study included 50 patients, 25 with CMB and 25 patients without CMB (median age 77 y, IQR: 70 to 82 y; 30 of 50 female) who were imaged with FDG PET-3T MRI from April to July 2023. Standard GRE (90 s) and SWI (192 s) were compared with an EPI-accelerated GRE (aGRE; 13 s, 86% time reduction) and an EPI-accelerated SWI substitution (aSWI; 33 s, 83% time reduction). Three board-certified neuroradiologists independently reported CMB and SS (per ARIA-H monitoring guidelines), perceived image quality and motion for each sequence. There were 240 total assessments per rater (the 4 different sequences for the 50 patients plus 10 duplicated patients). Sensitivity, specificity, positive and negative predictive values, area under the curve (AUC), inter-rater and intrarater agreement were determined for each sequence and rater. RESULTS:The aggregate AUCs for the 4 individual sequences were excellent for detecting CMB (0.84 to 0.94) and SS (0.89 to 1.00) without statistical differences observed between standard and EPI-accelerated substitutions. Both aGRE and aSWI had high negative predictive values (96.5% to 100%). There were modest quantitative correlations between standard and accelerated sequences (0.606 and 0.391 for GRE and SWI, respectively), no differences in CMB count for aGRE (bias 0.01, P=0.895), but reduced CMB count with aSWI (bias -1.12, P=0.014). Inter-rater agreements were mildly reduced for both GRE versus aGRE (eg, 0.757 to 0.622 for CMB detection) and SWI versus aSWI (eg, 0.834 to 0.649 for SS detection). Perceived image quality for accelerated sequences was reduced, but with less motion observed with aSWI. CONCLUSIONS:The aGRE and aSWI sequences shorten scan times 86% and 83%, respectively, with similar diagnostic performance for ARIA-H screening, but reduced rater agreement and perceived image quality.

PURPOSE OF REVIEW/UNASSIGNED:Alzheimer disease (AD) and epilepsy are major causes of neurologic disability and are reciprocally related: epileptiform discharges, subclinical seizures, and epilepsy are more prevalent in patients with AD compared with controls; progressive cognitive impairment commonly afflicts epilepsy patients; and late-onset epilepsy patients have higher rates of new-onset dementia. RECENT FINDINGS/UNASSIGNED:Epidemiologic studies support shared risk factors (e.g., genetic variants, vascular disease, sleep disorders, microbiome) with notable divergences. AD and epilepsy have some overlapping anatomic (e.g., hippocampus, entorhinal, and association cortex), clinical (e.g., memory, attentional, and executive) impairments, and neuropathologic (e.g., amyloid, tau, neurofibrillary tangles) features. Shared clinical and translational challenges include underlying mechanisms (e.g., genetic variants, neuroinflammation, metabolic and mitochondrial dysfunction, excitatory/inhibitory imbalance, microbiome, and sociodemographic factors) and identifying valid and reliable biomarkers (e.g., total tau and phosphorylated tau (p-tau), amyloid deposition, Aβ42/Aβ40 ratio) to assess disease progression, predict outcomes, and assess potentially disease-modifying interventions. SUMMARY/UNASSIGNED:Identifying convergences and divergences between epilepsy and AD may inform our understanding. The clinical, neurophysiologic, neuropathologic, and molecular pathologic changes in AD and epilepsy may reveal pathophysiologic insights and therapeutic opportunities.

INTRODUCTION/BACKGROUND:Neutrophil-to-lymphocyte ratio (NLR), a marker of systemic inflammation, has been linked to dementia risk, but prior studies were limited by small sample sizes. METHODS:We assessed the association between baseline NLR and incident Alzheimer's disease (AD) and Alzeimer's disease and related dementias (AD/ADRD) using electronic health records from New York University (NYU) (n = 284,530) and the Veterans Health Administration [VA] (n = 85,836) Hospitals from 2011 to 2023. AD/ADRD diagnoses were identified via International Classification of Diseases (ICD) codes ≥6 months post-baseline. Cox models and cumulative incidence functions (CIFs) adjusted for demographic and clinical variables, with death as a competing risk. RESULTS:Higher NLR was associated significantly with increased AD/ADRD risk in both cohorts (NYU hazard ratio [HR] = 1.07, 95% confidence interval [CI] 1.02-1.15; VA HR = 1.21, 95% CI 1.10-1.34). Spline analysis further confirmed a continuous dose-response relationship, and subgroup analyses showed higher risk among female and Hispanic patients. DISCUSSION/CONCLUSIONS:Elevated NLR is independently associated with higher AD/ADRD risk across diverse populations, highlighting the role of systemic inflammation and neutrophil-mediated pathways in neurodegeneration.

INTRODUCTION/BACKGROUND:We examined obstructive sleep apnea (OSA) severity's association with Alzheimer's disease (AD) plasma biomarkers, independent or synergistic with cerebrospinal fluid (CSF) amyloid, and as a proof of concept, whether plasma amyloid beta (Aβ)42/Aβ40 with OSA severity improves detection of amyloidosis and tau pathology. METHODS:In 120 cognitively normal older adults (70 with CSF data) from New York University sleep and aging studies (2013-2021), OSA severity was measured using apnea/hypopnea index with 4% desaturation; plasma Aβ40, Aβ42, tau, and neurofilament light chain (NfL) via single molecule array; CSF amyloid and tau via enzyme-linked immunosorbent assay. Associations evaluated adjusted correlations and generalized models; receiver operating characteristic analyses evaluated diagnostic accuracy. RESULTS:OSA severity correlated with plasma Aβ40 (r = 0.21), Aβ42 (r = 0.26), and Aβ42/Aβ40 (r = 0.20). Plasma tau and NfL associations depended on CSF-Aβ42. OSA severity with Aβ42/Aβ40 improved CSF amyloidosis (area under the curve [AUC] = 0.78) and tau pathology (AUC = 0.71) detection. DISCUSSION/CONCLUSIONS:OSA severity relates to elevated plasma Aβ and, with CSF amyloid, to tau/NfL. Combined plasma and OSA measures aid non-invasive AD associations' detection.

INTRODUCTION/BACKGROUND:Though brain fog is common in Long-coronavirus disease 2019 (Long-COVID), the incidence of mild cognitive impairment (MCI) is unknown. METHODS:In an observational cohort study, recovered COVID-positive, Long-COVID, and COVID-negative subjects underwent blinded evaluation using National Alzheimer's Coordinating Center (NACC) and National Institute on Aging (NIA) -Alzheimer's Association diagnostic criteria for dementia and MCI. The cumulative incidence of MCI was calculated for each group, and the hazard of MCI was compared between groups. RESULTS:Among 260 subjects, the cumulative incidence of MCI over 4.4 years was higher with Long-COVID (27%) versus recovered-COVID (5%) or COVID-negative status (1%). There was a higher hazard of MCI for patients with Long-COVID compared to those without (hazard ratio [HR] 3.93, 95% confidence interval [CI] 1.86-8.31, p < 0.001), and specifically for the Alzheimer's disease (AD) -related MCI subtype (HR 3.20, 95% confidence interval [CI] 1.14-9.00, p = 0.027). DISCUSSION/CONCLUSIONS:The cumulative incidence and adjusted hazard of MCI (and specifically AD-related MCI) at 4.4 years was significantly higher among Long-COVID patients compared to recovered-COVID and COVID-negative controls.

Neurodegeneration, along with amyloid and tau, define the AT(N) framework of Alzheimer's disease that has shaped the development of diagnostics and therapeutics. Yet, biomarker development for neurodegeneration has lagged behind that for amyloid and tau, with limited definition of its heterogeneous microstructural aspects that may each serve as critical measures. In this issue of the JCI, Gong et al. leveraged diffusion MRI to derive a unique measure of axonal injury or axonal density index (ADI). Through cross-sectional and longitudinal analyses, they demonstrated that the ADI has superior performance in detecting, tracking, and predicting clinical impairment compared with prior diffusion MRI methods to evaluate axonal health and standard biomarkers of amyloid and tau. As such, the ADI measure may serve as an important expansion of the neurodegeneration biomarker repertoire.

INTRODUCTION/BACKGROUND:Choroid plexus (ChP) enlargement is a neuroimaging biomarker of neuroinflammation and neurodegeneration. However, evidence of ChP structural and perfusion alterations in long coronavirus disease (COVID) and their clinical relevance remains limited. METHODS:This study included 86 long COVID, 67 recovered COVID, and 26 COVID-negative healthy controls (HCs). ChP volume and cerebral blood flow (CBF) were quantified, and their associations with Alzheimer's disease (AD) symptoms and plasma biomarkers were examined. RESULTS:Both patient groups showed higher ChP volume and lower CBF than HC. Relative to recovered COVID, long COVID patients had a larger ChP volume, but no significant difference in CBF. ChP volume correlated positively with glial fibrillary acidic protein (r = 0.35) and phosphorylated tau217 (p-tau217; r = 0.54), while CBF correlated negatively with p-tau217 (r = -0.56). Both ChP volume and CBF were associated with cognitive decline measured with Mini-Mental State Examination and Clinical Dementia Rating. DISCUSSION/CONCLUSIONS:These findings suggest that ChP differences in long COVID are associated with AD-related cognitive decline and increased plasma biomarkers. HIGHLIGHTS/CONCLUSIONS:Long coronavirus disease (COVID) patients show choroid plexus (ChP) enlargement and reduced cerebral blood flow. ChP alterations are associated with Alzheimer's disease (AD)-related symptoms and plasma biomarker changes. ChP alterations on magnetic resonance imaging may serve as imaging markers for tracking neurological symptoms and AD-related pathology in post-COVID patients.

Machine learning (ML) on structural MRI data shows high potential for classifying Alzheimer's disease (AD) progression, but the specific contribution of brain regions, demographics, and proteinopathy remains unclear. Using Alzheimer's Disease Neuroimaging Initiative (ADNI) data, we applied an extreme gradient-boosting algorithm and SHAP (SHapley Additive exPlanations) values to classify cognitively normal (CN) older adults, those with mild cognitive impairment (MCI) and AD dementia patients. Features included structural MRI, CSF status, demographics, and genetic data. Analyses comprised one cross-sectional multi-class classification (CN vs. MCI vs. AD dementia, n = 568) and two longitudinal binary-class classifications (CN-to-MCI converters vs. CN stable, n = 92; MCI-to-AD converters vs. MCI stable, n = 378). All classifications achieved 70-77% accuracy and 61-83% precision. Key features were CSF status, hippocampal volume, entorhinal thickness, and amygdala volume, with a clear dissociation: hippocampal properties contributed to the conversion to MCI, while the entorhinal cortex characterized the conversion to AD dementia. The findings highlight explainable, trajectory-specific insights into AD progression.