Sports-related peripheral nerve injuries of the upper limb.

Peripheral nerve injuries in athletes affect the upper limb more commonly than the lower limb. Common mechanisms include compression, traction, laceration, and ischemia. Specific sports can have unique mechanisms of injury and are more likely to be associated with certain neuropathies. Familiarity with these sport-specific variables and recognition of the common presentations of upper limb neuropathic syndromes are important in assessing an athlete with a suspected peripheral nerve injury. Evaluation may require imaging modalities and/or electrodiagnostic testing to confirm a nerve injury. In some cases, diagnostic injections may be needed to differentiate neuropathic versus musculoskeletal etiology. Early and accurate diagnosis is essential for treatment/management and increases the likelihood of a safe return-to-sport and avoidance of long-term functional consequences. Most nerve injuries can be treated conservatively, however, severe or persistent cases may require surgical intervention. This monograph reviews key diagnostic, management, and preventative strategies for sports-related peripheral nerve injuries involving the upper limb.

A standardized ultrasound approach in neuralgic amyotrophy.

Neuralgic amyotrophy (NA), also referred to as idiopathic brachial plexitis and Parsonage-Turner syndrome, is a peripheral nerve disorder characterized by acute severe shoulder pain followed by progressive upper limb weakness and muscle atrophy. While NA is incompletely understood and often difficult to diagnose, early recognition may prevent unnecessary tests and interventions and, in some situations, allow for prompt treatment, which can potentially minimize adverse long-term sequalae. High-resolution ultrasound (HRUS) has become a valuable tool in the diagnosis and evaluation of NA. Pathologic HRUS findings can be grouped into four categories: nerve swelling, swelling with incomplete constriction, swelling with complete constriction, and fascicular entwinement, which may represent a continuum of pathologic processes. Certain ultrasound findings may help predict the likelihood of spontaneous recovery with conservative management versus the need for surgical intervention. We recommend relying heavily on history and physical examination to determine which nerves are clinically affected and should therefore be assessed by HRUS. The nerves most frequently affected by NA are the suprascapular, long thoracic, median and anterior interosseous nerve (AIN) branch, radial and posterior interosseous nerve (PIN) branch, axillary, spinal accessory, and musculocutaneous. When distal upper limb nerves are affected (AIN, PIN, superficial radial nerve), the lesion is almost always located in their respective fascicles within the parent nerve, proximal to its branching point. The purpose of this review is to describe a reproducible, standardized, ultrasonographic approach for evaluating suspected NA, and to share reliable techniques and clinical considerations when imaging commonly affected nerves.

Predator-Prey Evolution from an Eco-evolutionary Trade-off Model: The Role of Trait Differentiation.

We develop a novel eco-evolutionary modelling framework and demonstrate its efficacy by simulating the evolution of trait distributions in predator and prey populations. The eco-evolutionary modelling framework assumes that population traits have beta distributions and defines canonical equations for the dynamics of each total population size, the population's average trait value, and a measure of the population's trait differentiation. The trait differentiation is included in the modelling framework as a phenotype analogue, Q, of Wright's fixation index [Formula: see text], which is inversely related to the sum of the beta distribution shape parameters. The canonical equations may be used as templates to describe the evolution of population trait distributions in many ecosystems that are subject to stabilising selection. The solutions of the "population model" are compared with those of a "phenotype model" that simulates the growth of each phenotype as it interacts with every other phenotype under the same trade-offs. The models assume no sources of new phenotypic variance, such as mutation or gene flow. We examine a predator-prey system in which each population trades off growth against mortality: the prey optimises devoting resources to growth or defence against predation; and the predator trades off increasing its attack rate against increased mortality. Computer solutions with stabilising selection reveal very close agreement between the phenotype and population model results, which both predict that evolution operates to stabilise an initially oscillatory system. The population model reduces the number of equations required to simulate the eco-evolutionary system by several orders of magnitude, without losing verisimilitude for the overarching population properties. The population model also allows insights into the properties of the system that are not available from the equivalent phenotype model.

The eco-evolutionary modelling of populations and their traits using a measure of trait differentiation.

We develop new equations for the eco-evolutionary dynamics of populations and their traits. These equations resolve the change in the phenotypic differentiation within a population, which better estimates how the variance of the trait distribution changes. We note that traits may be bounded, assume they may be described by beta distributions with small variances, and develop a coupled ordinary differential equation system to describe the dynamics of the total population, the mean trait value, and a measure of phenotype differentiation. The variance of the trait in the population is calculated from its mean and the population's phenotype differentiation. We consider an example of two competing plant populations to demonstrate the efficacy of the new approach. Each population may trade-off its growth rate against its susceptibility to direct competition from the other population. We create two models of this system: a population model based on our new eco-evolutionary equations; and a phenotype model, in which the growth or demise of each fraction of each population with a defined phenotype is simulated as it interacts with a shared limiting resource and its competing phenotypes and populations. Comparison of four simulation scenarios reveals excellent agreement between the predicted quantities from both models: total populations, the average trait values, the trait variances, and the degree of phenotypic differentiation within each population. In each of the four scenarios simulated, three of which are initially subject to competitive exclusion in the absence of evolution, the populations adapt to coexist. One population maximises growth and dominates, while the other minimises competitive losses. These simulations suggest that our new eco-evolutionary equations may provide an excellent approximation to phenotype changes in populations.

The emergence of new trophic levels in eco-evolutionary models with naturally-bounded traits.

Ecosystems and food webs are structured into trophic levels of who eats whom. Species that occupy higher trophic levels have less available energy and higher energetic costs than species at lower trophic levels. So why do higher trophic levels exist? What processes generate new trophic levels? We consider a heuristic eco-evolutionary model based on simple Lotka-Volterra equations, where the evolution of traits is described by a generalisation of Lande's equation. The transition from competition to predation in this simplest of models is a successful, safe strategy for a population, and suggests a propensity to develop new trophic levels may be an inherent property of ecosystems. Numerical simulations with a more complex eco-evolutionary model of interacting plant and herbivore populations display the emergence of a new trophic level as an alternative to continued competition. These simulations reveal that new trophic levels may arise naturally from ecosystems because a robust strategy for a population in the presence of a strong competitor that could dominate or potentially extinguish them, is to predate upon the competitor. The same properties that make the competitor strong make it an ideal prey, suggesting the rubric that it is better to eat a strong competitor than to continue competing.

Ultrasound-guided treatment of peripheral entrapment mononeuropathies.

The advent of high-resolution neuromuscular ultrasound (US) has provided a useful tool for conservative treatment of peripheral entrapment mononeuropathies. US-guided interventions require careful coordination of transducer and needle movement along with a detailed understanding of sonoanatomy. Preprocedural planning and positioning can be helpful in performing these interventions. Corticosteroid injections, aspiration of ganglia, hydrodissection, and minimally invasive procedures can be useful nonsurgical treatments for mononeuropathies refractory to conservative care. Technical aspects as well as the current understanding of the indications and efficacy of these procedures for common entrapment mononeuropathies are reviewed in this study. Muscle Nerve, 2019.

Simulating Eco-evolutionary Processes in an Obligate Pollination Model with a Genetic Algorithm.

Pollination interactions are common, and their maintenance is critical for many food crops upon which human populations depend. Pollination is a mutualism interaction; together with predation and competition, mutualism makes up the triumvirate of fundamental interactions that control population dynamics. Here we examine pollination interactions (nectar reward for gamete transport service) using a simple heuristic model similar to the Lotka-Volterra models that have underpinned our understanding of predation and competition so effectively since the 1920s. We use a genetic algorithm to simulate the eco-evolutionary interactions of the plant and pollinator populations and examine the distributions of the parameter values and zero isoclines to infer the relative ubiquity of the various eco-evolutionary outcomes possible in the model. Our results suggest that trade-offs between costs and benefits for the pollinator may be a key component of obligate pollination systems in achieving adaptive success creating and stably occupying mutualist niches.

A Simple, Realistic, Inexpensive Nerve Phantom.

Ultrasound-guided nerve blocks are common techniques in several medical specialties. Phantoms are commonly used when teaching these procedures. Commercial phantoms are expensive, and most previously published "homemade" nerve phantoms have a substantial amount of posterior shadowing, making it difficult to visualize the needle posterior to the simulated nerve. We have constructed a simple and easy-to-make nerve block phantom using a hot dog core embedded in a gelatin-psyllium hydrophilic mucilloid fiber mixture that has little to no posterior shadowing.

Predicting the risk of acute care readmissions among rehabilitation inpatients: A machine learning approach.

INTRODUCTION: Readmission from inpatient rehabilitation facilities to acute care hospitals is a serious problem. This study aims to develop a predictive model based on machine learning algorithms to identify patients at high risk of readmission. METHODS: A retrospective dataset (2001-2017) including 16,902 patients admitted into a large inpatient rehabilitation facility in North Carolina was collected in 2017. Three types of machine learning models with different predictors were compared in 2018. The model with the highest c-statistic was selected as the best model and further tested by using five sets of training and validation data with different split time. The optimum threshold for classification was identified. RESULTS: The logistic regression model with only functional independence measures has the highest validation c-statistic at 0.852. Using this model to predict the recent 5 years acute care readmissions yielded high discriminative ability (c-statistics: 0.841-0.869). Larger training data yielded better performance on the test data. The default cutoff (0.5) resulted in high specificity (>0.997) but low sensitivity (<0.07). The optimum threshold helped to achieve a balance between sensitivity (0.754-0.867) and specificity (0.747-0.780). CONCLUSIONS: This study demonstrates that functional independence measures can be analyzed by using machine learning algorithms to predict acute care readmissions, thus improving the effectiveness of preventive medicine.

Improving the Performance Time and Accuracy of Ultrasound-Guided Interventions: A Randomized Controlled Double-Blind Trial of the Line-of-Sight Approach and the "APPLES" Mnemonic.

OBJECTIVES: To determine whether the line-of-sight approach improved the performance time and accuracy of ultrasound (US)-guided needle placement targeting the subdeltoid bursa in a cadaver among novice operators compared to the side approach. A secondary objective was to determine whether participants thought the APPLES (angle, position, perpendicular, line up, entry, sweep) mnemonic was a helpful guide for performing the procedure. METHODS: Medical students and residents were randomized into either a line-of-sight or side approach group and then crossed over to the other group. The procedure time was determined by 2 blinded reviewers. A survey was administered to determine which method participants preferred and whether they thought the APPLES mnemonic was helpful. A paired t test was used to compare the performance time, and the McNemar test was used to compare the accuracy of the methods. RESULTS: Among the 110 participants, the performance time with the line-of-sight approach (mean, 14.4 seconds; SD, 9.95 seconds) was significantly decreased compared to the side approach (mean, 18.6 seconds; SD, 10.1 seconds; P = .00029). Additionally, participants who only hit the target using one method were more likely to hit the target in 30 seconds using the line-of-sight approach (P = .035). In total, 72.7% of participants preferred the line-of-sight approach over the side approach, and 88.2% of participants thought that APPLES mnemonic was useful. CONCLUSIONS: This study highlights the finding that positioning of the operator is important in performing US-guided interventions, and the line-of-sight approach may improve the performance time and accuracy among novice operators. Furthermore, the APPLES mnemonic serves as a useful educational tool for teaching US-guided interventional procedures.

SHIELD and HZETRN Comparisons of Pion Production Cross Sections.

A program of comparing American (NASA) and Russian (ROSCOSMOS) space radiation transport codes has recently begun, and the first paper directly comparing the NASA and ROSCOSMOS space radiation transport codes, HZETRN and SHIELD respectively has recently appeared. The present work represents the second time that NASA and ROSCOSMOS calculations have been directly compared, and the focus here is on models of pion production cross sections used in the two transport codes mentioned above. It was found that these models are in overall moderate agreement with each other and with experimental data. Disagreements that were found are discussed.

Obligate Mutualism in an Extended Consumer-Resource Framework.

The development of a theory to underpin the obligate mutualist interactions that appear to be ubiquitous in nature has not proceeded at the same pace as the development of theory to support competition and predation. A constraint may be that obligate mutualism appears unable to be presented in the simple linear models that have so successfully served as heuristics for the other interactions. A number of simple nonlinear models have been used to propose explanations of obligate mutualism, but these solutions are often predicated on careful choices of functional forms. We present a theory of obligate mutualism in an explicit mass-conserving framework using simple models that are robust to choices of functional forms.

More May Not be Better: Enhanced Spacecraft Shielding May Exacerbate Cognitive Decrements by Increasing Pion Exposures during Deep Space Exploration.

The pervasiveness of deep space radiation remains a confounding factor for the transit of humans through our solar system. Spacecraft shielding both protects astronauts but also contributes to absorbed dose through galactic cosmic ray interactions that produce secondary particles. The resultant biological effects drop to a minimum for aluminum shielding around 20 g/cm2 but increase with additional shielding. The present work evaluates for the first time, the impact of secondary pions on central nervous system functionality. The fractional pion dose emanating from thicker shielded spacecraft regions could contribute up to 10% of the total absorbed radiation dose. New results from the Paul Scherrer Institute have revealed that low dose exposures to 150 MeV positive and negative pions, akin to a Mars mission, result in significant, long-lasting cognitive impairments. These surprising findings emphasize the need to carefully evaluate shielding configurations to optimize safe exposure limits for astronauts during deep space travel.

Constructing ecologies.

We synthesize the generic properties of ecologically realistic multi-trophic level models and define criteria for ecological realism. We define an "ecospace" in which all ecologically realistic dynamics are confined, and construct "resource rays" that define the resources available to each species at every point in the ecospace. Resource rays for a species are lines from a vertex of maximum resource to the opposite boundary where no resources are available. The growth functions of all biota normally decrease along their resource rays, and change sign from positive to negative. This property prescribes that each species must have a zero isosurface within the ecospace. We illustrate our conditions on a highly cited three trophic level model from population dynamics, showing how to extend this system biologically consistently to a closed ecological system. Our synthesis extends the concept of carrying capacity of population models to explicitly include exhaustion of limiting resources, and so allows for population biology models to be considered as ecologically closed systems with respect to a key limiting nutrient. This approach unifies many theoretical and applied models in a common biogeochemical framework, facilitates better understanding of the key structures of complex ecologies, and suggests strategies for efficient design of experiments.

Neuromuscular Ultrasound: Indications in the Electrodiagnostic Laboratory.

ABSTRACT: Accurate assessment of neuromuscular disorders is critical to facilitate timely treatment and achieve the best outcomes. Historically, electrodiagnostic studies have filled this role, but recently, neuromuscular ultrasound is being used in the electrodiagnostic laboratory. This review discusses the uses of neuromuscular ultrasound in the electrodiagnostic laboratory that have strong evidence, emphasizing those that could be adopted in a typical electrodiagnostic laboratory with a reasonable level of equipment and training. The evidence currently supports using neuromuscular ultrasound to diagnose carpal tunnel syndrome and ulnar neuropathies at the elbow and as a supplementary test when electrodiagnostic studies are suspected to be falsely negative or in axonal nonlocalizing lesions. Neuromuscular ultrasound can identify the causes of focal mononeuropathies, which can change treatment in specific cases. It is sensitive at identifying fasciculations and providing complementary evidence of autoimmune demyelinating polyneuropathies. It is particularly helpful in assessing nerves after trauma. Neuromuscular ultrasound is likely to prove even more useful in the electrodiagnostic laboratory as the technology continues to advance.

Impact of a Hybrid-Virtual Teaching Model on the Physical Examination Skills of Fourth-Year Medical Students.

ABSTRACT: A required fourth-year advanced core neurology-physical medicine and rehabilitation clerkship was adapted to hybrid format (2-wk remote; 2-wk in-person) during the COVID-19 pandemic. With teaching of the neurological physical examination being shifted to the remote component, we sought to determine whether this negatively affected student performance on an Objective Structured Clinical Examination, particularly the physical examination component. Mean pandemic-era total Objective Structured Clinical Examination scores ( n = 79, 85.1 ± 7.3) were similar to prepandemic era ( n = 137, 83.5 ± 6.0, P = 0.082). Pandemic-era physical examination scores were slightly higher than prepandemic (86.9 ± 6.5 vs. 84.9 ± 6.6). Despite conversion of the clerkship to a hybrid curriculum, the performance of the students on the Objective Structured Clinical Examination and the physical examination were unchanged. Reasons for this lack of change may include the constructiveness and integration of the case-based virtual demonstrations combined with in-person learning or the flexibility of the virtual course to allow students more time to prepare for the Objective Structured Clinical Examination and the physical examination. Our findings demonstrate that a hybrid-virtual model can be used to teach foundational skills such as the basics of the physical examination, while allowing faculty to address higher-order skills such as integration of clinical data with medical knowledge.

Impact of Predefined Angles and a Revised APPLES Mnemonic on Accuracy and Performance Time for Simulated Ultrasound-Guided Injections.

OBJECTIVES: Our objective was to determine whether predefined angles would improve performance time and accuracy of ultrasound-guided procedures by novice operators and whether a revised APPLES (approach, position, perpendicular, lift, entry, sweep) mnemonic was a helpful guide for performing the procedure. METHODS: Participants attempted to hit targets in-plane and out-of-plane at different depths with a needle under ultrasound guidance with and without predefined angles. Participants were then asked if they thought that the mnemonic would be helpful when learning both methods for ultrasound-guided procedures. RESULTS: There were 120 participants all of whom had performed fewer than six ultrasound guided procedures. Accuracy increased in all groups when angles were provided; however, only the 3-cm in-plane approach achieved statistical significance. Performance time also achieved statistical significance in two of the four groups. Ninety-five percent of participants thought that the revised APPLES mnemonic would be helpful for learning and performing ultrasound-guided procedures in the future. CONCLUSIONS: Predefined angles seem to positively impact procedure time and accuracy for some target depths, and the APPLES mnemonic could be a helpful mental checklist for many novice operators. These may be useful tools to facilitate safe and efficient ultrasound-guided procedures in the clinical space.

A Required, Combined Neurology-Physical Medicine and Rehabilitation Clerkship Addresses Clinical and Health Systems Knowledge Gaps for Fourth-Year Medical Students.

ABSTRACT: This study evaluated the impact of a 4-wk mandatory neurology-physical medicine and rehabilitation advanced-core clerkship for fourth-year medical students. The combined clerkship encouraged an interdisciplinary and function-based approach to the management of common neurologic, musculoskeletal, and pain complaints. Seventy-three fourth-year medical students participated in the rotation over 1 yr. A survey assessing knowledge and skill set topics was conducted before and after the clerkship. Qualitative feedback regarding the rotation was provided by the students and analyzed. Significant gaps in knowledge and skill sets were identified before the clerkship and successfully addressed by combined teaching modalities. These data demonstrate that an integrated neurology-physical medicine and rehabilitation clerkship can improve students' confidence in multiple domains. Integrating physical medicine and rehabilitation into core clerkships at other medical schools may provide an avenue to address curriculum gaps.

Palmaris Longus Tendinopathy Diagnosed With Ultrasound: A Case Report.

This patient is a 52-year-old woman who was referred to the electrodiagnostic (EDX) laboratory for evaluation of pain and paresthesias of the left upper limb. The results of the EDX study were normal. However, ultrasound revealed tendinopathy of the palmaris longus tendon, manifested by increased hypoechogenicity, caliber, and tenderness in response to sonopalpation compared to the right side. To the authors' knowledge there are no reported cases of palmaris longus tendinopathy diagnosed with ultrasound. This case supports the use of point-of-care ultrasound to explore other possible causes of pathology in patients with paresthesias in the context of normal findings on an EDX study. LEVEL OF EVIDENCE: V.

Comparison of space radiation GCR models to AMS heavy ion data.

Galactic cosmic rays (GCR) are a constant source of radiation that constitutes one of the major hazards during deep space exploration missions for both astronauts and hardware. In this work, GCR models commonly used by the space radiation protection community are compared with recently published high-precision, high-resolution measurements of cosmic ray lithium, beryllium, boron, carbon, nitrogen, and oxygen fluxes along with their ratios (Li/B, Li/C, Li/O, Be/B, Be/C, Be/O, B/C, B/O, C/O, N/B, N/O) from the Alpha Magnetic Spectrometer (AMS). All of the models were developed and calibrated prior to the publication of this AMS data, therefore this is an opportunity to validate the models against an independent data set. This paper is a compliment to the previously published comparison of GCR models with AMS hydrogen, helium, and the boron-to-carbon ratio (Norbury et al., 2018).