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Importance Classifying disease based on underlying pathobiology rather than clinical phenotype has implications for the development of biomarkers and therapy development. Observations Transactive response DNA-binding protein 43 kDa (TDP-43) pathology is observed across a range of clinically defined neurodegenerative disorders including limbic predominant age-related encephalopathy (LATE), most cases of amyotrophic lateral sclerosis (ALS), inclusion body myositis, multisystem proteinopathy, and approximately half the cases of frontotemporal dementia (FTD). Despite this shared biology, the current nosology for these neurodegenerative disorders is based on their distinct clinical phenotypes. An alternative approach recognizes the central role of TDP-43 pathology in disease pathogenesis, reserving the use of clinical terms like ALS, FTD, or LATE to describe phenotypic manifestations of underlying pathobiology. This approach also recognizes the converging biomarker and neuropathological data indicating that pathology begins presymptomatically, before the overt clinical manifestations of disease appear. Conclusions and Relevance In proposing a pathobiological definition of disease, the goal is to provide a road map for developing biomarkers that accurately reflect the underlying pathobiology of disease and for advancing therapeutic candidates that effectively target fundamental disease mechanisms.

Introduction: Flipped classroom models, which use active, case-based discussion, have shown promise across graduate medical education. Previous literature demonstrates that transitioning to a flipped classroom model resulted in significant increases in overall Orthopaedic In-Training Examination (OITE) scores. This observational study retrospectively compares foot and ankle OITE scores for orthopaedic surgery residents before and after implementation of a flipped classroom curriculum. Methods: This retrospective study reviewed OITE scores for orthopaedic residents, comparing a lecture-based curriculum (n = 49) to a flipped classroom curriculum (n = 61). Residents who started their second year in July 2020 or later were defined as treated. The curriculum is given to the postgraduate year-2 (PGY2) residents only. Percentage of correct foot and ankle questions (F&A) were analyzed via mixed-effects models using random-subject intercepts. Fixed effects included PGY, overall performance on other sections, and flipped classroom status. All statistical analyses were performed in R version 4.4.1. Results: Residents in the flipped classroom cohort demonstrated a statistically significant increase in F&A questions answered correctly. The average increase was 7% (95% confidence interval: 4%, 10%; p < 0.001). This improvement trend became clearly visible in PGY3 and grew stronger in senior residents. Specifically, PGY3 residents improved their mean percentage correct from 62.26% to 66.07% (p = 0.16). PGY4 residents improved from 69.16% to 74.83% (p = 0.013), and PGY5 residents improved from 69.03% to 75.53% (p = 0.006). Historically, approximately 75% of traditional PGY5 residents scored lower on the F&A section than on the rest of the examination. Conversely, in the flipped classroom group, approximately 75% of PGY4 and PGY5 residents scored higher on the F&A section compared with other sections Discussion: The implementation of a flipped classroom model was associated with a statistically significant improvement in resident performance on the F&A section of the OITE. The educational benefits of this curriculum appear cumulative over the course of residency, with the most substantial performance gains realized by senior residents in their fourth and fifth years of training. Level of Evidence: Level III , Observational Study. See Instructions for Authors for a complete description of levels of evidence.

Abstract INTRODUCTION Although cerebrospinal fluid (CSF) biomarkers reflect neurodegeneration in Alzheimer's disease (AD), it remains unclear whether these biomarkers track neurodegeneration in early‐onset Alzheimer's disease (EOAD). METHODS In 80 EOAD patients, we examined correlations between eight CSF biomarker levels and cortical thickness decreases within the EOAD cortical atrophy signature. Significant correlations were then entered into a multiple regression analysis. We also examined contributions of EOAD atrophy and CSF biomarkers to cognitive impairment. RESULTS The levels of four CSF biomarkers correlated to EOAD signature atrophy. Stepwise regression analyses revealed that CSF neurofilament light chain (NfL) levels best predicted EOAD signature atrophy. Multiple regression showed EOAD signature atrophy combined with CSF NfL levels explained more variance in cognitive impairment than either factor alone. DISCUSSION Within EOAD patients, CSF NfL levels relate to the magnitude of cortical atrophy, and a combination of EOAD signature atrophy and CSF NfL levels most robustly predict cognitive impairment.

Importance In vivo biomarkers for detecting neuropathologies from repetitive head impacts (RHI), including chronic traumatic encephalopathy (CTE), are needed. Objective To evaluate the utility of plasma phosphorylated tau 217 (p-tau217), assess its performance as a beta-amyloid (Aβ) biomarker in participants with RHI exposure at risk for CTE, and explore concordance with CTE neuropathology in a postmortem subsample. Design, Setting, and Participants This longitudinal, multicenter, case-control study used data from the Diagnostics, Imaging, and Genetics Network for the Objective Study and Evaluation of CTE (DIAGNOSE CTE) Research Project, collected from September 2016 to October 2023. Participants were former American football players (case participants) and asymptomatic men unexposed to RHI (control participants). A subsample had available neuropathologic data. Exposures RHI, traumatic encephalopathy syndrome (TES) diagnoses, and levels of CTE certainty. Main Outcomes and Measures Plasma p-tau217 (classified as positive [≥0.63 pg/mL], intermediate [0.40-0.62 pg/mL], and negative [&amp;lt;0.40 pg/mL]), Aβ–positron emission tomography (PET; 18 F-florbetapir; with Aβ-positive defined as a standardized uptake value ratio [SUVR] ≥1.10), and tau-PET ( 18 F-flortaucipir). TES diagnoses were assigned by multidisciplinary consensus conference. Analyses of postmortem brains controlled for age, race, and APOE ε4 status. Results Among 231 participants (mean [SD] age, 57.75 [8.25] years), 177 were former football players (117 professional and 60 college) and 54 were unexposed participants. Former football players had higher baseline mean (SD) p-tau217 concentrations than unexposed participants (0.35 [0.26] pg/mL vs 0.27 [0.14] pg/mL; P = .008), although this was driven by a higher proportion of Aβ-PET–positive participants among former players. Plasma p-tau217 increased over time across the sample (B = 0.207 [95% CI, 0.117-0.298]; P &amp;lt; .001), with no significant time × exposure group interactions. Among football players, p-tau217 showed no time × group interactions with TES diagnosis, TES-CTE certainty, or RHI metrics. Higher p-tau217 concentration correlated with higher global Aβ-PET SUVR (B = 0.058 [95% CI, 0.053-3.501; P = .01), with a few discordant cases (5 participants were p-tau217–negative and Aβ-PET–positive; 7 participants were p-tau217–positive and Aβ-PET–negative). P-tau217 had similar areas under the curve for projecting Aβ-PET positivity as cerebrospinal fluid (CSF) p-tau181/Aβ42 and CSF Aβ40/42 measures (p-tau217: AUC, 0.88 [95% CI, 0.80-0.96]; CSF p-tau181/Aβ42: AUC, 0.89 [95% CI, 0.79-1.00]; CSF Aβ40/42: AUC, 0.85 [95% CI, 0.72-0.98]). Among 9 brain donors, 6 had CTE (stages II-IV; none with Alzheimer disease). Seven had negative or intermediate p-tau217, concordant with Aβ-PET. Two p-tau217 outliers with stage III CTE had normal concentrations upon additional testing. Conclusions and Relevance The findings of this study suggest that plasma p-tau217 concentration is unlikely to be useful for the detection of CTE, but it does show utility for ruling out Aβ pathology in participants at risk for CTE.

Study Design. Post hoc analysis of prospectively-collected data. Objective. To identify factors predicting the most (and least) satisfaction following surgery for cervical spondylotic myelopathy (CSM). Summary of Background Data. Patient satisfaction affects long-term outcomes after surgery but the preoperative factors that influence postoperative satisfaction have not been well studied in patients with CSM. Methods. We conducted a post hoc analysis of prospectively-collected data from the Quality Outcomes Database (QOD) CSM registry cohort. Baseline and surgical characteristics were compared for patients with CSM reporting the most [North American Spine Society Satisfaction Score (NASS) 1] and least (NASS 4) satisfaction 24 months postoperatively. A multivariable logistic regression model was constructed using backward stepwise elimination to determine significant predictors of most versus least satisfaction. Twenty-four-month patient-reported outcomes (PROs) were compared. Results. Overall, 1141 patients were prospectively enrolled with 948 (83.1%) reaching 24-month follow-up. Of these, 699 met prespecified inclusion criteria: 610 (87.3%) were most satisfied and 89 (12.7%) were least satisfied. Though there were mean improvements in all 24-month PROs for the most satisfied cohort ( P <0.001), there were no significant improvements in 24-month PROs for the least satisfied cohort ( P >0.05). Using multivariable logistic regression modeling, a preoperative symptom of upper extremity weakness (OR=2.5, P =0.003), subjective myelopathy (OR=2.0, P =0.04), absence of numbness complaints (OR=2.2, P =0.003), symptom duration under 12 months (OR=1.6, P =0.047), Caucasian race (OR=2.3, P =0.001), participation in activities outside of the home (OR=2.0, P =0.04), anterior approach (OR=2.3, P <0.001), and higher baseline quality of life (OR=4.0, P =0.01) were predictive of the most satisfaction. Conclusion. Compared with the least satisfied, those most satisfied following surgery for CSM more often had a preoperative symptom of arm weakness, subjective myelopathy, the absence of numbness complaints, symptom duration under 12 months, higher baseline quality of life, and participation in activities outside of the home. Compared with a posterior approach, an anterior approach was associated with the most satisfaction. Taken together, early surgical treatment--before myelopathic symptoms significantly impact one's quality of life--may be considered to optimize patient satisfaction following CSM surgery.

Introduction Uveal melanoma has a marked tropism for the liver where immune tolerance facilitates metastatic progression and resistance to immunotherapy. Impaired CD8 + T cell immunosurveillance is a central determinant of disease progression in uveal melanoma, yet the underlying mechanisms driving liver-mediated immune subpression and hepatic metastasis are not fully understood. Here, we investigate molecular pathways that regulated hepatic CD8 + T cell function and evaluate clinical outcomes associated with liver-directed therapy. Methods Expression of autotaxin (ATX), the expression responsible for generating lysophosphatidic acid (LPA), was evaluated in hepatic resident cell populations. ATX transcript levels were assessed in CD8 + T cells isolated from hepatic metastases and compared with matched peripheral blood and healthy donor control. Antigen-specific effector CD8 + T cells were used to characterize downstream signaling responses to LPA stimulation. Functional studies evaluating cytokine production during chronic antigen exposure were performed using CD8 + T cells from LPA receptor 5-deficient ( Lpar5 -/- ) mice. Results We identify the autotaxin-lysophosphatidic acid (ATX-LPA) axis as a prominent immunoregulatory pathway in the metastatic hepatic tumor microenvironment. ATX, the enzyme responsible for LPA production, is constitutively expressed by hepatic resident cells, is detectable on Kupffer cells and is associated with increased immunosubpressive markers. CD8 + T cells isolated from hepatic metastasis in a patient with uveal melanoma display markedly elevated ATX transcripts compared to matched peripheral blood (&gt;5 log 2 fold change) and healthy controls. Using antigen-specific effector CD8 + T cells, we demonstrate LPA signaling induces low level, persistent ERK phosphorylation distinct from canonical antigen-induced TCR signaling. Genetic deletion of the LPA receptor 5 ( Lpar5 -/- ) on CD8 + T cells restores CD8 T cell percentages and cytokine function during persistent antigen stimulation in the presence of LPA. Discussion These findings define an ATX-LPA mechanisms of dysfunctional ERK signaling that may contribute to hepatic immune subpression in uveal melanoma. We highlight this pathway as a rational therapeutic target alongside liver-directed clinical interventions.

Abstract Repetitive head impacts sustained during American football have been associated with neuropathological changes such as white matter shear injuries. However, the impact of specific factors, such as age of first exposure and cumulative head impact burden, on white matter integrity remains unclear. This study investigated in vivo white matter microstructural changes using diffusion tensor imaging and tract-based spatial statistics in 165 male former American football players (mean age 57.3 years, range 45–74) and 52 unexposed asymptomatic male controls (mean age 59.4 years, range 45–74) in the DIAGNOSE CTE Research Project. Compared to controls, former football players exhibited significantly higher fractional anisotropy (FA) in 1.97% of the white matter skeleton (1552 voxels; Cohen’s d = 0.587) and higher tissue-corrected FA (FAt) in 1.48% of the white matter skeleton (1004 voxels; Cohen’s d = 0.616). No significant differences were observed for mean diffusivity, axial diffusivity, radial diffusivity, or free water between football players and controls. Among football players, there were no significant differences in the white matter microstructure between players diagnosed with traumatic encephalopathy syndrome and those without the diagnosis. Lower FA was significantly associated with older age (P &lt; 0.00001) and an earlier age of first exposure to tackle football (P &lt; 0.01), while lower FAt was associated with greater cumulative head impact burden, specifically higher linear acceleration (P &lt; 0.04) and rotational force (P &lt; 0.02). This study highlights the influential role of exposure factors on white matter microstructure in former American football players, as well as the utility of diffusion tensor imaging to aid in characterizing the long-term effects of repetitive head impacts in contact sport athletes.