T1 mapping from routine 3D T1-weighted inversion recovery sequences in clinical practice: comparison against reference inversion recovery fast field echo T1 scans and feasibility in multiple sclerosis.

BACKGROUND AND PURPOSE: Quantitative T1 mapping can be an essential tool for assessing tissue injury in multiple sclerosis (MS). We introduce T1-REQUIRE, a method that converts a single high-resolution anatomical 3D T1-weighted Turbo Field Echo (3DT1TFE) scan into a parametric T1 map that could be used for quantitative assessment of tissue damage. We present the accuracy and feasibility of this method in MS. METHODS: 14 subjects with relapsing-remitting MS and 10 healthy subjects were examined. T1 maps were generated from 3DT1TFE images using T1-REQUIRE, which estimates T1 values using MR signal equations and internal tissue reference T1 values. Estimated T1 of lesions, white, and gray matter regions were compared with reference Inversion-Recovery Fast Field Echo T1 values and analyzed via correlation and Bland-Altman (BA) statistics. RESULTS: 159 T1-weighted (T1W) hypointense MS lesions and 288 gray matter regions were examined. T1 values for MS lesions showed a Pearson's correlation of r = 0.81 (p < 0.000), R2 = 0.65, and Bias = 4.18%. BA statistics showed a mean difference of -53.95 ms and limits of agreement (LOA) of -344.20 and 236.30 ms. Non-lesional normal-appearing white matter had a correlation coefficient of r = 0.82 (p < 0.000), R2 = 0.67, Bias = 8.78%, mean difference of 73.87 ms, and LOA of -55.67 and 203.41 ms. CONCLUSIONS: We demonstrate the feasibility of retroactively derived high-resolution T1 maps from routinely acquired anatomical images, which could be used to quantify tissue pathology in MS. The results of this study will set the stage for testing this method in larger clinical studies for examining MS disease activity and progression.

Quantification of Collateral Supply with Local-AIF Dynamic Susceptibility Contrast MRI Predicts Infarct Growth.

Background and purpose: In ischemic stroke, leptomeningeal collaterals can provide compensatory blood flow to tissue at risk despite an occlusion, and impact treatment response and infarct growth. The purpose of this work is to test the hypothesis that local perfusion with an appropriate Local Arterial Input Function (AIF) is needed to quantify the degree of collateral blood supply in tissue distal to an occlusion. Materials and methods: Seven experiments were conducted in a pre-clinical middle cerebral artery occlusion model. Magnetic resonance dynamic susceptibility contrast (DSC) was imaged and post-processed as cerebral blood flow maps with both a traditionally chosen single arterial input function (AIF) applied globally to the whole brain (i.e. "Global-AIF") and a novel automatic delay and dispersion corrected AIF (i.e. "Local AIF") that is sensitive to retrograde flow. Pial collateral recruitment was assessed from x-ray angiograms and infarct growth via serially acquired diffusion weighted MRI scans both blinded to DSC. Results: The degree of collateralization at x-ray correlated strongly with quantitative perfusion determined using the Local AIF in the ischemic penumbra (R2=0.81) compared to a traditionally chosen Global-AIF (R2=0.05). Quantitative perfusion calculated using a Local-AIF was negatively correlated (less infarct progression as local perfusion increased) with infarct growth (R2 = 0.79) compared to Global-AIF (R2=0.02). Conclusions: Local DSC perfusion with a Local-AIF is more accurate for assessing tissue status and degree of leptomeningeal collateralization than traditionally chosen AIFs. These findings support use of a Local-AIF in determining quantitative tissue perfusion with collateral supply in occlusive disease.

Efficacy Assessment of Cerebral Perfusion Augmentation Through Functional Connectivity in an Acute Canine Stroke Model.

BACKGROUND AND PURPOSE: Ischemic stroke disrupts functional connectivity within the brain's resting-state networks (RSNs), impacting recovery. This study evaluates the effects of NEH (Norepinephrine and Hydralazine), a cerebral perfusion augmentation therapy, on RSN integrity in a hyper-acute canine stroke model. MATERIALS AND METHODS: Fifteen adult purpose-bred mongrel canines, divided into treatment and control (natural history) groups, underwent endovascular induction of acute middle cerebral artery occlusion (MCAO). Post-occlusion, the treatment group received intra-arterial Norepinephrine (0.1-1.52 µg/kg/min, adjusted for 25-45 mmHg above baseline mean arterial pressure) and Hydralazine (20mg). Resting-state fMRI data were acquired with a 3.0 T scanner using a BOLD-sensitive EPI sequence (TR/TE=1400 ms/20ms, 2.5 mm slices, 300 temporal positions). Preprocessing included motion correction, spatial smoothing (2.5 mm FWHM), and high-pass filtering (0.01 Hz cutoff). Functional connectivity within RSNs were analyzed through group-level independent component analysis (ICA) and weighted whole-brain ROI-to-ROI connectome, pre-and post-MCAO. RESULTS: NEH therapy significantly maintained connectivity post-MCAO in the Higher-order Visual and Parietal RSNs, as evidenced by thresholded statistical mapping (TFCE p-corr > 0.95). However, this preservation was network-dependent, with no significant changes in the Primary Visual and Sensorimotor networks. CONCLUSIONS: NEH demonstrates potential as a proof-of-concept therapy for maintaining RSN functional connectivity following ischemic stroke, emphasizing the therapeutic promise of perfusion augmentation. These insights reinforce the role of functional connectivity as a measurable endpoint for stroke intervention efficacy, suggesting clinical translatability for patients with insufficient collateral circulation. ABBREVIATIONS: NEH＝ Norepinephrine and Hydralazine; RSN＝ Resting-State Network; ICA = Independent Component Analysis; rsfMRI = resting-state Functional Magnetic Resonance Imaging; MCAO = Middle Cerebral Artery Occlusion; TFCE = Threshold-Free Cluster Enhancement.

Vaccine-Boosted CCP Decreases Virus Replication and Hastens Resolution of Infection Despite Transiently Enhancing Disease in SARS-CoV-2-Infected Hamsters.

Definitive data demonstrating the utility of coronavirus disease 2019 (COVID-19) convalescent plasma (CCP) for treating immunocompromised patients remains elusive. To better understand the mechanism of action of CCP, we studied viral replication and disease progression in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected hamsters treated with CCP obtained from recovered COVID-19 patients that were also vaccinated with an mRNA vaccine, hereafter referred to as Vaxplas. Vaxplas transiently enhanced disease severity and lung pathology in hamsters treated near peak viral replication due to immune complex and activated complement deposition in pulmonary endothelium, and recruitment of M1 proinflammatory macrophages into the lung parenchyma. However, aside from one report, transient enhanced disease has not been reported in CCP recipient patients, and the transient enhanced disease in Vaxplas hamsters may have been due to mismatched species IgG-FcR interactions, infusion timing, or other experimental factors. Despite transient disease enhancement, Vaxplas dramatically reduced virus replication in lungs and improved infection outcome in SARS-CoV-2-infected hamsters.

Dopamine Increases Accuracy and Lengthens Deliberation Time in Explicit Motor Skill Learning.

Although animal research implicates a central role for dopamine in motor skill learning, a direct causal link has yet to be established in neurotypical humans. Here, we tested if a pharmacological manipulation of dopamine alters motor learning, using a paradigm which engaged explicit, goal-directed strategies. Participants (27 females; 11 males; aged 18-29 years) first consumed either 100 mg of levodopa (n = 19), a dopamine precursor that increases dopamine availability, or placebo (n = 19). Then, during training, participants learnt the explicit strategy of aiming away from presented targets by instructed angles of varying sizes. Targets jumped mid-movement by the instructed aiming angle. Task success was thus contingent upon aiming accuracy and not speed. The effect of the dopamine manipulations on skill learning was assessed during training and after an overnight follow-up. Increasing dopamine availability at training improved aiming accuracy and lengthened reaction times, particularly for larger, more difficult aiming angles, both at training and, importantly, at follow-up, despite prominent session-by-session performance improvements in both accuracy and speed. Exogenous dopamine thus seems to result in a learnt, persistent propensity to better adhere to task goals. Results support the proposal that dopamine is important in engagement of instrumental motivation to optimize adherence to task goals, particularly when learning to execute goal-directed strategies in motor skill learning.

Long-term Outcomes With Macroplastique in Women With Stress Urinary Incontinence Secondary to Intrinsic Sphincter Deficiency.

OBJECTIVE: To evaluate the long-term outcomes of polydimethylsiloxane (Macroplastique (MPQ)) in women with stress urinary incontinence (SUI) secondary to intrinsic sphincter deficiency (ISD) using validated questionnaires. METHODS: Following IRB approval, charts of non-neurogenic women with SUI secondary to ISD who underwent MPQ injection were reviewed from a prospectively maintained database. ISD was defined as positive stress test with a well-supported urethra and low Valsalva leak point pressure when available. Excluded were women with follow-up <5years. Baseline data included validated questionnaire scores (UDI-6 question 3 (0-3), VAS Quality of Life, Incontinence Impact Questionnaire (IIQ-7)) and urodynamic study findings. Patients were followed with same questionnaires and three-dimensional ultrasound evaluating volume/configuration of MPQ. All three-dimensional ultrasound measurements were performed by the same imaging team blinded to clinical outcomes. Outcomes were evaluated in four groups based on prior SUI treatment. Success was defined as UDI-6 question 3 score of 0-1 and not requiring additional anti-incontinence therapy at the last visit after the last MPQ injection. RESULTS: From April 2011-December 2016, 106 patients (median age 67) met study criteria. Median follow-up time was 7.4years. Median MPQ injected was 5 mL. Overall success was 43%, with 54% successful after one injection and 46% requiring ≥2 injections. Across all groups, patients had improvement in Quality of Life and IIQ-7 Question 7 (frustration). Among the failure group, 17% opted for a secondary autologous sling procedure. CONCLUSION: MPQ demonstrated long-term favorable outcomes in a subset of women with SUI secondary to ISD.

Trial Readiness of Cavernous Malformations With Symptomatic Hemorrhage, Part II: Biomarkers and Trial Modeling.

BACKGROUND: Quantitative susceptibility mapping (QSM) and dynamic contrast-enhanced quantitative perfusion (DCEQP) magnetic resonance imaging sequences assessing iron deposition and vascular permeability were previously correlated with new hemorrhage in cerebral cavernous malformations. We assessed their prospective changes in a multisite trial-readiness project. METHODS: Patients with cavernous malformation and symptomatic hemorrhage (SH) in the prior year, without prior or planned lesion resection or irradiation were enrolled. Mean QSM and DCEQP of the SH lesion were acquired at baseline and at 1- and 2-year follow-ups. Sensitivity and specificity of biomarker changes were analyzed in relation to predefined criteria for recurrent SH or asymptomatic change. Sample size calculations for hypothesized therapeutic effects were conducted. RESULTS: We logged 143 QSM and 130 DCEQP paired annual assessments. Annual QSM change was greater in cases with SH than in cases without SH (P=0.019). Annual QSM increase by ≥6% occurred in 7 of 7 cases (100%) with recurrent SH and in 7 of 10 cases (70%) with asymptomatic change during the same epoch and 3.82× more frequently than clinical events. DCEQP change had lower sensitivity for SH and asymptomatic change than QSM change and greater variance. A trial with the smallest sample size would detect a 30% difference in QSM annual change during 2 years of follow-up in 34 or 42 subjects (1 and 2 tailed, respectively); power, 0.8, α=0.05. CONCLUSIONS: Assessment of QSM change is feasible and sensitive to recurrent bleeding in cavernous malformations. Evaluation of an intervention on QSM percent change may be used as a time-averaged difference between 2 arms using a repeated measures analysis. DCEQP change is associated with lesser sensitivity and higher variability than QSM. These results are the basis of an application for certification by the US Food and Drug Administration of QSM as a biomarker of drug effect on bleeding in cavernous malformations. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03652181.

Trial Readiness of Cavernous Malformations With Symptomatic Hemorrhage, Part I: Event Rates and Clinical Outcome.

BACKGROUND: Cerebral cavernous malformation with symptomatic hemorrhage (SH) are targets for novel therapies. A multisite trial-readiness project (https://www.clinicaltrials.gov; Unique identifier: NCT03652181) aimed to identify clinical, imaging, and functional changes in these patients. METHODS: We enrolled adult cerebral cavernous malformation patients from 5 high-volume centers with SH within the prior year and no planned surgery. In addition to clinical and imaging review, we assessed baseline, 1- and 2-year National Institutes of Health Stroke Scale, modified Rankin Scale, European Quality of Life 5D-3 L, and patient-reported outcome-measurement information system, Version 2.0. SH and asymptomatic change rates were adjudicated. Changes in functional scores were assessed as a marker for hemorrhage. RESULTS: One hundred twenty-three, 102, and 69 patients completed baseline, 1- and 2-year clinical assessments, respectively. There were 21 SH during 178.3 patient years of follow-up (11.8% per patient year). At baseline, 62.6% and 95.1% of patients had a modified Rankin Scale score of 1 and National Institutes of Health Stroke Scale score of 0 to 4, respectively, which improved to 75.4% (P=0.03) and 100% (P=0.06) at 2 years. At baseline, 74.8% had at least one abnormal patient-reported outcome-measurement information system, Version 2.0 domain compared with 61.2% at 2 years (P=0.004). The most common abnormal European Quality of Life 5D-3 L domains were pain (48.7%), anxiety (41.5%), and participation in usual activities (41.4%). Patients with prospective SH were more likely than those without SH to display functional decline in sleep, fatigue, and social function patient-reported outcome-measurement information system, Version 2.0 domains at 2 years. Other score changes did not differ significantly between groups at 2 years. The sensitivity of scores as an SH marker remained poor at the time interval assessed. CONCLUSIONS: We report SH rate, functional, and patient-reported outcomes in trial-eligible cerebral cavernous malformation with SH patients. Functional outcomes and patient-reported outcomes generally improved over 2 years. No score change was highly sensitive or specific for SH and could not be used as a primary end point in a trial.

Quantitative perfusion and water transport time model from multi b-value diffusion magnetic resonance imaging validated against neutron capture microspheres.

Purpose: Quantification of perfusion in ml/100 g/min, rather than comparing relative values side-to-side, is critical at the clinical and research levels for large longitudinal and multi-center trials. Intravoxel incoherent motion (IVIM) is a non-contrast magnetic resonance imaging diffusion-based scan that uses a multitude of b-values to measure various speeds of molecular perfusion and diffusion, sidestepping inaccuracy of arterial input functions or bolus kinetics. Questions remain as to the original of the signal and whether IVIM returns quantitative and accurate perfusion in a pathology setting. This study tests a novel method of IVIM perfusion quantification compared with neutron capture microspheres. Approach: We derive an expression for the quantification of capillary blood flow in ml/100 g/min by solving the three-dimensional Gaussian probability distribution and defining water transport time (WTT) as when 50% of the original water remains in the tissue of interest. Calculations were verified in a six-subject pre-clinical canine model of normocapnia, CO2 induced hypercapnia, and middle cerebral artery occlusion (ischemic stroke) and compared with quantitative microsphere perfusion. Results: Linear regression analysis of IVIM and microsphere perfusion showed agreement (slope = 0.55, intercept = 52.5, R2=0.64) with a Bland-Altman mean difference of -11.8 [-78,54] ml/100 g/min. Linear regression between dynamic susceptibility contrast mean transit time and IVIM WTT asymmetry in infarcted tissue was excellent (slope=0.59, intercept = 0.3, R2=0.93). Strong linear agreement was found between IVIM and reference standard infarct volume (slope = 1.01, R2=0.79). The simulation of cerebrospinal fluid (CSF) suppression via inversion recovery returned a blood signal reduced by 82% from combined T1 and T2 effects. Conclusions: The accuracy and sensitivity of IVIM provides evidence that observed signal changes reflect cytotoxic edema and tissue perfusion and can be quantified with WTT. Partial volume contamination of CSF may be better removed during post-processing rather than with inversion recovery.

Transient susceptibility imaging as a measure of hemodynamic compromise: A pilot study.

BACKGROUND AND PURPOSE: The purpose of this study was to test the hypothesis that hemodynamically compromised brains exhibit transient changes in magnetic susceptibility throughout the cardiac cycle, and to model these changes using Linear System Theory to extract an index that reflects cerebrovascular reserve. MATERIALS AND METHODS: Eleven patients with angiographically-confirmed intracranial atherosclerotic disease with >50% stenosis were imaged with susceptibility weighted, cardiac-gated single shot images of cerebral Oxygen Extraction Fraction (OEF) at different timepoints of the cardiac cycle. Cardiac gating of the OEF acquisition allowed interrogation of oxygenated blood and the detection of changes throughout the cardiac cycle. Independent component analysis (ICA) of raw k-space data across the cardiac phase allowed MRI signal decomposition into dynamic and static components for image reconstruction. An asymmetry index score of the resultant parametric images were compared to test the hypothesis that variation in hemoglobin-induced susceptibility across the cardiac cycle indeed reflects pathophysiology of cerebrovascular disease. A mathematical model was derived to parameterize physiologic changes induced by the presence of a hemodynamically significant stenosis in the brain as a tissue impulse response parameter (ß). RESULTS: OEF was elevated in the affected hemisphere (50.34 ± 12.13% vs 46.93 ± 12.34%), but failed to reach statistical significance (p < .0796). Transient changes in the OEF signal showed significant distinction between healthy and compromised tissue (0.56 ± 0.067 vs 0.44 ± 0.067, p < .019)). The derived tissue impulse response function was found to be significant as well (10.72 ± 3.48 10-3 ms-1, 9.69 ± 3.51 10-3 ms-1; p < .037). CONCLUSION: In this pilot study, we found transient OEF and ß to be significant predictors of hemispheric compromise.

Express Visuomotor Responses Reflect Knowledge of Both Target Locations and Contextual Rules during Reaches of Different Amplitudes.

When humans reach to visual targets, extremely rapid (∼90 ms) target-directed responses can be observed in task-relevant proximal muscles. Such express visuomotor responses are inflexibly locked in time and space to the target and have been proposed to reflect rapid visuomotor transformations conveyed subcortically via the tecto-reticulo-spinal pathway. Previously, we showed that express visuomotor responses are sensitive to explicit cue-driven information about the target, suggesting that the express pathway can be modulated by cortical signals affording contextual prestimulus expectations. Here, we show that the express visuomotor system incorporates information about the physical hand-to-target distance and contextual rules during visuospatial tasks requiring different movement amplitudes. In one experiment, we recorded the activity from two shoulder muscles as 14 participants (6 females) reached toward targets that appeared at different distances from the reaching hand. Increasing the reaching distance facilitated the generation of frequent and large express visuomotor responses. This suggests that both the direction and amplitude of veridical hand-to-target reaches are encoded along the putative subcortical express pathway. In a second experiment, we modulated the movement amplitude by asking 12 participants (4 females) to deliberately undershoot, overshoot, or stop (control) at the target. The overshoot and undershoot tasks impaired the generation of large and frequent express visuomotor responses, consistent with the inability of the express pathway to generate responses directed toward nonveridical targets as in the anti-reach task. Our findings appear to reflect strategic, cortically driven modulation of the express visuomotor circuit to facilitate rapid and effective response initiation during target-directed actions.SIGNIFICANCE STATEMENT Express (∼90 ms) arm muscle responses that are consistently tuned toward the location of visual stimuli suggest a subcortical contribution to target-directed visuomotor behavior in humans, potentially via the tecto-reticulo-spinal pathway. Here, we show that express muscle responses are modulated appropriately to reach targets at different distances, but generally suppressed when the task required nonveridical responses to overshoot/undershoot the real target. This suggests that the tecto-reticulo-spinal pathway can be exploited strategically by the cerebral cortex to facilitate rapid initiation of effective responses during a visuospatial task.

Administration of vaccine-boosted COVID-19 convalescent plasma to SARS-CoV-2 infected hamsters decreases virus replication in lungs and hastens resolution of the infection despite transiently enhancing disease and lung pathology.

The utility of COVID-19 convalescent plasma (CCP) for treatment of immunocompromised patients who are not able to mount a protective antibody response against SARS-CoV-2 and who have contraindications or adverse effects from currently available antivirals remains unclear. To better understand the mechanism of protection in CCP, we studied viral replication and disease progression in SARS-CoV-2 infected hamsters treated with CCP plasma obtained from recovered COVID patients that had also been vaccinated with an mRNA vaccine, hereafter referred to as Vaxplas. We found that Vaxplas dramatically reduced virus replication in the lungs and improved infection outcome in SARS-CoV-2 infected hamsters. However, we also found that Vaxplas transiently enhanced disease severity and lung pathology in treated animals likely due to the deposition of immune complexes, activation of complement and recruitment of increased numbers of macrophages with an M1 proinflammatory phenotype into the lung parenchyma.

Cavernous Angioma Symptomatic Hemorrhage (CASH) Trial Readiness II: Imaging Biomarkers and Trial Modeling.

Background: Quantitative susceptibility mapping (QSM) and dynamic contrast enhanced quantitative perfusion (DCEQP) MRI sequences assessing iron deposition and vascular permeability were previously correlated with new hemorrhage in cavernous angiomas. We assessed their prospective changes in cavernous angiomas with symptomatic hemorrhage (CASH) in a multisite trial readiness project ( clinicaltrials.gov NCT03652181 ). Methods: Patients with CASH in the prior year, without prior or planned lesion resection or irradiation were enrolled. Mean QSM and DCEQP of CASH lesion were acquired at baseline, and at 1- and 2-year follow-ups. Sensitivity and specificity of biomarker changes were analyzed in relation to predefined lesional symptomatic hemorrhage (SH) or asymptomatic change (AC). Sample size calculations for hypothesized therapeutic effects were conducted. Results: We logged 143 QSM and 130 DCEQP paired annual assessments. Annual QSM change was greater in cases with SH than in cases without SH (p= 0.019). Annual QSM increase by ≥ 6% occurred in 7 of 7 cases (100%) with recurrent SH and in 7 of 10 cases (70%) with AC during the same epoch, and 3.82 times more frequently than clinical events. DCEQP change had lower sensitivity for SH and AC than QSM change, and greater variance. A trial with smallest sample size would detect a 30% difference in QSM annual change in 34 or 42 subjects (one and two-tailed, respectively), power 0.8, alpha 0.05. Conclusions: Assessment of QSM change is feasible and sensitive to recurrent bleeding in CASH. Evaluation of an intervention on QSM percent change may be used as a time-averaged difference between 2 arms using a repeated measures analysis. DCEQP change is associated with lesser sensitivity and higher variability than QSM. These results are the basis of an application for certification by the U.S. F.D.A. of QSM as a biomarker of drug effect in CASH.

The effects of crank power and cadence on muscle fascicle shortening velocity, muscle activation and joint-specific power during cycling.

Whilst people typically choose to locomote in the most economical fashion, during bicycling they will, unusually, chose cadences that are higher than metabolically optimal. Empirical measurements of the intrinsic contractile properties of the vastus lateralis (VL) muscle during submaximal cycling suggest that the cadences that people self-selected might allow for optimal muscle fascicle shortening velocity for the production of knee extensor muscle power. It remains unclear, however, whether this is consistent across different power outputs where the self-selected cadence (SSC) varies. We examined the effect of cadence and external power requirements on muscle neuromechanics and joint power during cycling. VL fascicle shortening velocity, muscle activation and joint-specific power were measured during cycling between 60 and 120 rpm (including SSC), while participants produced 10%, 30% and 50% of peak maximal power. VL shortening velocity increased as cadence increased but was similar across the different power outputs. Although no differences were found in the distribution of joint power across cadence conditions, the absolute knee joint power increased with increasing crank power output. Muscle fascicle shortening velocity increased in VL at the SSC as pedal power demands increased from submaximal towards maximal cycling. A secondary analysis of muscle activation patterns showed minimized activation of VL and other muscles near the SSC at the 10% and 30% power conditions. Minimization of activation with progressively increasing fascicle shortening velocities at the SSC may be consistent with the theory that the optimum shortening velocity for maximizing power increases with the intensity of exercise and recruitment of fast twitch fibers.

Increased muscle force does not induce greater stretch-induced damage to calf muscles during work-matched heel drop exercise.

PURPOSE: To investigate the effect of muscle force during active stretch on quantitative and qualitative indicators of exercise-induced muscle damage (EIMD) in the medial gastrocnemius (MG) muscle. METHODS: Twelve recreationally active volunteers performed two trials of an eccentric heel drop exercise. Participants performed a single bout of low-load (body weight) and high-load (body weight + 30% body weight) exercises on separate legs. The total mechanical work output for each condition was matched between legs. Before, two hours and 48 h after each bout of eccentric exercise, electrically stimulated triceps surae twitch torque, muscle soreness, MG active fascicle length at maximum twitch torque and muscle passive stiffness were collected. Triceps surae electromyographic (EMG) activity, MG fascicle stretch and MG muscle-tendon unit (MTU) length were measured during the eccentric tasks. RESULTS: The high-load condition increased triceps surae muscle activity by 6-9%, but reduced MG fascicle stretch (p < 0.001). MTU stretch was similar between conditions. The greater muscle force during stretch did not give rise to additional torque loss (5 vs 6%) or intensify muscle soreness. CONCLUSIONS: Adding 30% body weight during eccentric contractions has a modest impact on exercise-induced muscle damage in the medial gastrocnemius muscle. These results suggest that muscle load may not be an important determinant of stretch-induced muscle damage in the human MG muscle. The muscle investigated does exhibit large pennation angles and high series elastic compliance; architectural features that likely buffer muscle fibres against stretch and damage.

A preliminary diagnostic accuracy study of quantitative MRI biomarkers for differentiating parotid tumor types.

Background: Differentiating among the different types of parotid tumors on imaging is useful for guiding clinical disposition, which ultimately may lead to surgical management. The goal of this study was to determine whether quantitative T2 signal characteristics and morphologic features on magnetic resonance imaging (MRI) can serve as predictive biomarkers for distinguishing between tumor types. Methods: A retrospective review of T2-weighted MRIs in patients with pathology-proven parotid tumors was performed. Quantitative T2 maps and surface regularity measurements of the tumors were obtained via semi-automated regions of interest (ROI). Linear Discriminant Analysis was used to populate the receiver operating characteristics (ROCs) curves for these variables. A P value of <0.05 was considered to be significant. Results: A total of 35 tumors (21 benign and 14 malignant neoplasms) were included in this analysis. For differentiating the benign versus malignant classes of parotid tumors, T2 signal and surface regularity combined yielded an area under the curve of 0.62 (P value: 0.2) through the ROC analysis. However, for the pleomorphic adenomas versus other types of parotid tumors, using both T2 signal and surface regularity yielded an area under the curve of 0.81 (P value: 0.007) through the ROC analysis. Conclusions: T2 signal and surface regularity combined can significantly differentiate pleomorphic adenomas from other types of parotid tumors and can potentially be used as a predictive imaging biomarker.

Effectiveness of ocrelizumab on clinical and MRI outcome measures in multiple sclerosis across black and white cohorts: A single-center retrospective study.

OBJECTIVE: To examine differences in the therapeutic response to ocrelizumab in multiple sclerosis (MS) patients who self-identified as either White or Black, assessed longitudinally by expanded disability status scale (EDSS) progression and MRI brain volume loss. METHODS: MS subjects treated with ocrelizumab were retrospectively identified. Clinical data were available for 229 subjects (White 146; Black 83) and MRI data from for 48 subjects (White 31; Black 17). Outcome measures were changes in the EDSS and brain volume over time. EDSS were analyzed as raw scores, ambulatory (EDSS <5.0) vs. ambulatory with assistance (5.5 ≤ EDSS ≤ 6.5) status, and EDSS severity (< 3.0, 3.0-5.0, and > 5.5 ≤ 6.5). General linear mixed model was used for statistical analysis. FreeSurfer was used for volumetric analysis. RESULTS: The Black cohort had overrepresentation of females (78% vs. 62%, p = 0.013), lower age (median, 45 (IQR 39-51) vs. 49 (38-58), p = 0.08), lower Vitamin D levels (33 (21-45) vs. 40 (29-52), p = 0.002), and higher EDSS (4 (2-6) vs. 2.5 (1-6), p = 0.019). There was no progression of EDSS scores over the 2-year observation period. The covariates with significant influence on the baseline EDSS scores were older age, race, longer disease duration, prior MS treatment, and lower vitamin D levels. No differences were observed between the racial groups over time in the cortical, thalamic, caudate, putamen, and brainstem gray matter volumes nor in the cortical thickness or total lesion volume. CONCLUSION: In this real-world clinical and radiological study, ocrelizumab treatment was highly effective in stabilizing clinical and MRI measures of disease progression in Blacks and Whites, despite higher baseline disability in the Black cohort.

Musculoskeletal simulations to examine the effects of accentuated eccentric loading (AEL) on jump height.

Background: During counter movement jumps, adding weight in the eccentric phase and then suddenly releasing this weight during the concentric phase, known as accentuated eccentric loading (AEL), has been suggested to immediately improve jumping performance. The level of evidence for the positive effects of AEL remains weak, with conflicting evidence over the effectiveness in enhancing performance. Therefore, we proposed to theoretically explore the influence of implementing AEL during constrained vertical jumping using computer modelling and simulation and examined whether the proposed mechanism of enhanced power, increased elastic energy storage and return, could enhance work and power. Methods: We used a simplified model, consisting of a ball-shaped body (head, arm, and trunk), two lower limb segments (thigh and shank), and four muscles, to simulate the mechanisms of AEL. We adjusted the key activation parameters of the muscles to influence the performance outcome of the model. Numerical optimization was applied to search the optimal solution for the model. We implemented AEL and non-AEL conditions in the model to compare the simulated data between conditions. Results: Our model predicted that the optimal jumping performance was achieved when the model utilized the whole joint range. However, there was no difference in jumping performance in AEL and non-AEL conditions because the model began its push-off at the similar state (posture, fiber length, fiber velocity, fiber force, tendon length, and the same activation level). Therefore, the optimal solution predicted by the model was primarily driven by intrinsic muscle dynamics (force-length-velocity relationship), and this coupled with the similar model state at the start of the push-off, resulting in similar push-off performance across all conditions. There was also no evidence of additional tendon-loading effect in AEL conditions compared to non-AEL condition. Discussion: Our simplified simulations did not show improved jump performance with AEL, contrasting with experimental studies. The reduced model demonstrates that increased energy storage from the additional mass alone is not sufficient to induce increased performance and that other factors like differences in activation strategies or movement paths are more likely to contribute to enhanced performance.

Augmentation of perfusion with simultaneous vasodilator and inotropic agents in experimental acute middle cerebral artery occlusion: a pilot study.

BACKGROUND: This study tests the hypothesis that simultaneous cerebral blood pressure elevation and potent vasodilation augments perfusion to ischemic tissue in acute ischemic stroke and it varies by degree of pial collateral recruitment. METHODS: Fifteen mongrel canines were included. Subjects underwent permanent middle cerebral artery occlusion; pial collateral recruitment was scored before treatment. Seven treatment subjects received a continuous infusion of norepinephrine (0.1-1.52 µg/kg/min; titrated 25-45 mmHg above baseline mean arterial pressure while keeping systolic blood pressure below 180 mmHg) and hydralazine (20 mg) starting 30 min post-occlusion. Perfusion (cerebral blood flow-CBF) was evaluated with quantitative dynamic susceptibility contrast MRI 2.5 hours post-occlusion to produce images in mL/100 g/min, and relative CBF measured as ratios. Mean region of interest (ROI) values were reported, and compared and subject to regression analysis to elucidate trends. RESULTS: Differences in quantitative CBF (qCBF) between treatment and control group varied by degree of pial collateral recruitment, based on Wilcoxon rank sum scores and regression model fit. For poorly collateralized subjects, ipsilateral anatomic, core infarct, and penumbra regions showed treatment with higher qCBF, raised above the ischemic threshold, compared with the control, while well collateralized subjects showed a paradoxical decrease maintained above the ischemic threshold for neuronal death. qCBF on the contralateral side increased regardless of collateralization. CONCLUSION: Results suggest that perfusion can be augmented in ischemic stroke with norepinephrine and hydralazine. Perfusion augmentation depends on degree of collateralization and territory in question, with some evidence of vascular steal.

Analysis of the extent of limbic system changes in multiple sclerosis using FreeSurfer and voxel-based morphometry approaches.

BACKGROUND AND PURPOSE: The limbic brain is involved in diverse cognitive, emotional, and autonomic functions. Injury of the various parts of the limbic system have been correlated with clinical deficits in MS. The purpose of this study was to comprehensively examine different regions of the subcortical limbic system to assess the extent of damage within this entire system as it may be pertinent in correlating with specific aspects of cognitive and behavioral dysfunction in MS by using a fully automated, unbiased segmentation approach. METHODS: Sixty-seven subjects were included in this study, including 52 with multiple sclerosis (MS) and 15 healthy controls. Only patients with stable MS disease, without any relapses, MRI activity, or disability progression were included. Subcortical limbic system segmentation was performed using the FreeSurfer pipeline ScLimbic, which provides volumes for fornix, mammillary bodies, hypothalamus, septal nuclei, nucleus accumbens, and basal forebrain. Hippocampus and anterior thalamic nuclei were added as additional components of the limbic circuitry, also segmented through FreeSurfer. Whole limbic region mask was generated by combining these structures and used for Voxel-based morphometry (VBM) analysis. RESULTS: The mean [95% confidence interval] of the total limbic system volume was lower (0.22% [0.21-0.23]) in MS compared to healthy controls (0.27%, [0.25-0.29], p < .001). Pairwise comparisons of individual limbic regions between MS and controls was significant in the nucleus accumbens (0.046%, [0.043-0.050] vs. 0.059%, [0.051-0.066], p = .005), hypothalamus (0.062%, [0.059-0.065] vs. 0.074%, [0.068-0.081], p = .001), basal forebrain (0.038%, [0.036-0.040] vs. 0.047%, [0.042-0.051], p = .001), hippocampus (0.47%, [0.45-0.49] vs. 0.53%, [0.49-0.57], p = .004), and anterior thalamus (0.077%, [0.072-0.082] vs. 0.093%, [0.084-0.10], p = .001) after Bonferroni correction. Volume of several limbic regions was significantly correlated with T2 lesion burden and brain parenchymal fraction (BPF). Multiple regression model showed minimal influence of BPF on limbic brain volume and no influence of other demographic and disease state variables. VBM analysis showed cluster differences in the fornix and anterior thalamic nuclei at threshold p < 0.05 after adjusting for covariates but the results were insignificant after family-wise error corrections. CONCLUSIONS: The results show evidence that brain volume loss is fairly extensive in the limbic brain. Given the significance of the limbic system in many disease states including MS, such volumetric analyses can be expanded to studying cognitive and emotional disturbances in larger clinical trials. FreeSurfer ScLimbic pipeline provided an efficient and reliable methodology for examining many of the subcortical structures related to the limbic brain.