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38 result(s) for "Fields, Daryl"
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Epidural stimulation of the cervical spinal cord for post-stroke upper-limb paresis
Cerebral strokes can disrupt descending commands from motor cortical areas to the spinal cord, which can result in permanent motor deficits of the arm and hand. However, below the lesion, the spinal circuits that control movement remain intact and could be targeted by neurotechnologies to restore movement. Here we report results from two participants in a first-in-human study using electrical stimulation of cervical spinal circuits to facilitate arm and hand motor control in chronic post-stroke hemiparesis ( NCT04512690 ). Participants were implanted for 29 d with two linear leads in the dorsolateral epidural space targeting spinal roots C3 to T1 to increase excitation of arm and hand motoneurons. We found that continuous stimulation through selected contacts improved strength (for example, grip force +40% SCS01; +108% SCS02), kinematics (for example, +30% to +40% speed) and functional movements, thereby enabling participants to perform movements that they could not perform without spinal cord stimulation. Both participants retained some of these improvements even without stimulation and no serious adverse events were reported. While we cannot conclusively evaluate safety and efficacy from two participants, our data provide promising, albeit preliminary, evidence that spinal cord stimulation could be an assistive as well as a restorative approach for upper-limb recovery after stroke. Electrical stimulation of cervical spinal circuits facilitates arm and hand movements in two participants with moderate and severe chronic post-stroke hemiparesis.
Spinal metaplasticity in respiratory motor control
A hallmark feature of the neural system controlling breathing is its ability to exhibit plasticity. Less appreciated is the ability to exhibit metaplasticity, a change in the capacity to express plasticity (i.e., \"plastic plasticity\"). Recent advances in our understanding of cellular mechanisms giving rise to respiratory motor plasticity lay the groundwork for (ongoing) investigations of metaplasticity. This detailed understanding of respiratory metaplasticity will be essential as we harness metaplasticity to restore breathing capacity in clinical disorders that compromise breathing, such as cervical spinal injury, motor neuron disease and other neuromuscular diseases. In this brief review, we discuss key examples of metaplasticity in respiratory motor control, and our current understanding of mechanisms giving rise to spinal plasticity and metaplasticity in phrenic motor output; particularly after pre-conditioning with intermittent hypoxia. Progress in this area has led to the realization that similar mechanisms are operative in other spinal motor networks, including those governing limb movement. Further, these mechanisms can be harnessed to restore respiratory and non-respiratory motor function after spinal injury.
A guide to selecting upper thoracic versus lower thoracic uppermost instrumented vertebra in adult spinal deformity correction
Purpose Operative treatment of adult spinal deformity (ASD) has been shown to improve patient health-related quality of life (HRQOL). Selection of the uppermost instrumented vertebra (UIV) in either the upper thoracic (UT) or lower thoracic (LT) spine is a pivotal decision with effects on operative and postoperative outcomes. This review overviews the multifaceted decision-making process for UIV selection in ASD correction. Methods PubMed was queried for articles using the keywords “uppermost instrumented vertebra”, “upper thoracic”, “lower thoracic”, and “adult spinal deformity”. Results Optimization of UIV selection may lead to superior deformity correction, better patient-reported outcomes, and lower risk of proximal junctional kyphosis (PJK) and failure (PJF). Patient alignment characteristics, including preoperative thoracic kyphosis, coronal deformity, and the magnitude of sagittal correction influence surgical decision-making when selecting a UIV, while comorbidities such as poor body mass index, osteoporosis, and neuromuscular pathology should also be taken in to account. Additionally, surgeon experience and resources available to the hospital may also play a role in this decision. Currently, it is incompletely understood whether postoperative HRQOLs, functional and radiographic outcomes, and complications after surgery differ between selection of the UIV in either the UT or LT spine. Conclusion The correct selection of the UIV in surgical planning is a challenging task, which requires attention to preoperative alignment, patient comorbidities, clinical characteristics, available resources, and surgeon-specific factors such as experience.
Top-ten most-cited articles on anterior column release in the context of minimally invasive lumbar interbody fusion
Introduction: Lateral anterior column release (ACR) is a minimally invasive option for the correction of sagittal plane deformity. To assemble a homogeneous picture of published research on ACR, an advanced bibliometric analysis was conducted to compile the top-ten most-cited articles on the topic of ACR. Methods: A keyword search using the Thomson Reuters Web of Knowledge was conducted to identify articles discussing the role of lateral ACR. The articles were then ranked based on the total number of citations to identify the ten most-cited articles published. A subjective appraisal of the findings of these articles was conducted to provide a ranked literature review and to examine trends in the study of ACR between 2012 and 2019. Results: The earliest published article on ACR was in 2012 by Deukmedjian et al. Three articles were in vitro biomechanical assessments of ACR, and seven articles were on outcome analyses, which were either case series or case controlled. The most-cited article was a biomechanical study authored by Uribe et al. The article with the highest rate of citations/year was authored by Manwaring et al. Uribe and the European Spine Journal were the most frequently cited author and journal, respectively. Conclusions: The lateral ACR approach has enjoyed significant scholarly attention since its advent. Higher-level analyses with robust control groups, larger sample sizes, and long-term follow-up are necessary to improve our understanding of this approach.
Potentiation of cortico-spinal output via targeted electrical stimulation of the motor thalamus
Cerebral white matter lesions prevent cortico-spinal descending inputs from effectively activating spinal motoneurons, leading to loss of motor control. However, in most cases, the damage to cortico-spinal axons is incomplete offering a potential target for therapies aimed at improving volitional muscle activation. Here we hypothesize that, by engaging direct excitatory connections to cortico-spinal motoneurons, stimulation of the motor thalamus could facilitate activation of surviving cortico-spinal fibers thereby immediately potentiating motor output. To test this hypothesis, we identify optimal thalamic targets and stimulation parameters that enhance upper-limb motor-evoked potentials and grip forces in anesthetized monkeys. This potentiation persists after white matter lesions. We replicate these results in humans during intra-operative testing. We then design a stimulation protocol that immediately improves strength and force control in a patient with a chronic white matter lesion. Our results show that electrical stimulation targeting surviving neural pathways can improve motor control after white matter lesions. Cerebral lesions result in loss of upper-limb motor functions. Here, the authors show that electrical stimulation of the motor thalamus can immediately and significantly improve strength and volitional force control improving arm and hand functions.
Cancer cachexia impairs neural respiratory drive in hypoxia but not hypercapnia
Background Cancer cachexia is an insidious process characterized by muscle atrophy with associated motor deficits, including diaphragm weakness and respiratory insufficiency. Although neuropathology contributes to muscle wasting and motor deficits in many clinical disorders, neural involvement in cachexia‐linked respiratory insufficiency has not been explored. Methods We first used whole‐body plethysmography to assess ventilatory responses to hypoxic and hypercapnic chemoreflex activation in mice inoculated with the C26 colon adenocarcinoma cell line. Mice were exposed to a sequence of inspired gas mixtures consisting of (i) air, (ii) hypoxia (11% O2) with normocapnia, (iii) hypercapnia (7% CO2) with normoxia, and (iv) combined hypercapnia with hypoxia (i.e. maximal chemoreflex response). We also tested the respiratory neural network directly by recording inspiratory burst output from ligated phrenic nerves, thereby bypassing influences from changes in diaphragm muscle strength, respiratory mechanics, or compensation through recruitment of accessory motor pools. Results Cachectic mice demonstrated a significant attenuation of the hypoxic tidal volume (0.26mL±0.01mL vs 0.30mL±0.01mL; p<0.05), breathing frequency (317±10bpm vs 344±6bpm; p<0.05) and phrenic nerve (29.5±2.6% vs 78.8±11.8%; p<0.05) responses. On the other hand, the much larger hypercapnic tidal volume (0.46±0.01mL vs 0.46±0.01mL; p>0.05), breathing frequency (392±5bpm vs 408±5bpm; p>0.05) and phrenic nerve (93.1±8.8% vs 111.1±13.2%; p>0.05) responses were not affected. Further, the concurrent hypercapnia/hypoxia tidal volume (0.45±0.01mL vs 0.45±0.01mL; p>0.05), breathing frequency (395±7bpm vs 400±3bpm; p>0.05), and phrenic nerve (106.8±7.1% vs 147.5±38.8%; p>0.05) responses were not different between C26 cachectic and control mice. Conclusions Breathing deficits associated with cancer cachexia are specific to the hypoxic ventilatory response and, thus, reflect disruptions in the hypoxic chemoafferent neural network. Diagnostic techniques that detect decompensation and therapeutic approaches that support the failing hypoxic respiratory response may benefit patients at risk for cancer cachectic‐associated respiratory failure.
Tajikistan's winter energy crisis
Tajikistan's electricity system is in a state of crisis. Approximately 70 percent of the Tajik people suffer from extensive shortages of electricity during the winter. These shortages, estimated at about 2,700 GWh, about a quarter of winter electricity demand, impose economic losses estimated at over United States (US) 200 million dollars per annum or 3 percent of Gross Domestic Product (GDP). The electricity shortages have not been addressed because investments have not been made in new electricity supply capacity and maintenance of existing assets has not improved. The financial incentive for electricity consumers to reduce their consumption is inadequate as electricity prices are among the lowest in the world. Without prompt action to remedy the causes of Tajikistan's electricity crisis and with growing demand, the shortages could increase to about 4,500 GWh by 2016 (over a third of winter electricity demand) or worse. The World Bank undertook this study to assist the Government of Tajikistan (GoT) in finding ways to overcome the current electricity shortages and establish a sound basis for meeting the growing electricity demand in Tajikistan. The study focuses on the investments and policy reforms needed between now and 2020 to strengthen the financial, technical and institutional capacity of the Tajik power sector and prepare the GoT for undertaking a major expansion of power supply capacity. The study excludes large hydropower plants with storage, given their complexity and global experience that such projects are subject to delays. The winter electricity shortages are caused by a combination of low hydropower output during winter when river flows are low and high demand driven by heating needs. The GoT should focus its immediate attention on three ways to eliminate the current winter power shortages: 1) ambitious energy efficiency plans to reduce uneconomic power usage; 2) new dual-fired thermal power supply to complement the existing hydropower supply during winter; and 3) increased energy imports to leverage surplus electricity supply in neighboring countries.
Load Sharing Classification Score in Patients with TLICS 4
INTRODUCTION Patient with TLICS 4 fall in a grey zone where treatment is at the discretion of neurosurgeon. This decision is often based on determination on whether the fracture is stable predicated on integirty of posterior ligamentous complex. MRI is often used to evaluate ligamentous injury but previous studies have shown that this MRI is too hypersensitive, leading to high rate of false positives. Load sharing classification is a repdorudicle scale that could be used to evaluate stability of a thoracolumbar fracture based on CT scan only. METHODS 111 consectutive neurologically intact patients with isolated thoracolumbar burst fracture (i.e. TLICS 4) were included in this retrospective study. Load sharing classification (LSC) score was determined based on degree of comminution (1-3), apposition (1-3), and kyphosis (1-3), total composite score of 3–9. RESULTS 44 patients underwent MRI, 15 had ligamentous injury, and 32 (28.8%) required surgery. In univariate logistic regression LSC score was associated with MRI acquisition (OR 1.7, 1.3- 2.1), presence of ligamentous injury (OR 1.5, 1.2- 2.0). In multivariate logistic regression, LSC score was assocaited with surgery (OR 3.7, 2.3-5.9), independent of MRI or PLC injury. None of the patients who did not undergo surgery required an operation with a mean follow up of 12.3 months. CONCLUSION Load sharing classification score in patients with TLICS4 is predictive of undergoing MRI, presence of ligamentous injury, and most strongly, surgical intervention. The application of load sharing classification in these patients may further guide decision making, obviating the need for MRI, and potentially save costs.
A Roadmap for Implanting Electrode Arrays to Evoke Tactile Sensations Through Intracortical Stimulation
Intracortical microstimulation (ICMS) is a method for restoring sensation to people with paralysis as part of a bidirectional brain–computer interface (BCI) to restore upper limb function. Evoking tactile sensations of the hand through ICMS requires precise targeting of implanted electrodes. Here we describe the presurgical imaging procedures used to generate functional maps of the hand area of the somatosensory cortex and subsequent planning that guided the implantation of intracortical microelectrode arrays. In five participants with cervical spinal cord injury, across two study locations, this procedure successfully enabled ICMS‐evoked sensations localized to at least the first four digits of the hand. The imaging and planning procedures developed through this clinical trial provide a roadmap for other BCI studies to ensure the successful placement of stimulation electrodes. Functional imaging of the somatosensory cortex in people with spinal cord injury enabled planning for precise electrode array placement in the brain for a brain–computer interface. Stimulation through electrodes in the somatosensory cortex generated sensations of touch in digits that matched the functional imaging results used for placement.
Initiatives in the hydro sector post World Commission on Dams - The Hydropower Sustainability Assessment Forum
The World Commission on Dams (WCD) has called for developers, governments, civil society, etc. to use its Strategic Priorities as a starting point for dialogue and initiatives to address issues regarding the development of dams. One very notable follow-up initiative has been led by the hydropower industry. The International Hydropower Association developed Sustainability Guidelines (IHA, 2004) and a Sustainability Assessment Protocol (IHA, 2006), and most recently has been involved in a two-year process with governments, NGOs and the finance sector to develop a broadly endorsed sustainability assessment tool based on review and update of the IHA Sustainability Assessment Protocol. This cross-sectoral process, known as the Hydropower Sustainability Assessment Forum (HSAF), has drawn on the knowledge base and many of the findings and recommendations of the World Commission on Dams, as well as a number of other developments in the last ten years. A fundamental premise of the work of the Forum is that an industry-driven and -owned initiative has far-reaching potential to influence performance in the hydropower sector. At the same time, the potential for the use of a broadly endorsed sustainability assessment tool for hydropower by those in other sectors is well recognised and aspired to by the Forum. This paper describes the work of the Forum up to August 2009 and the contents of the Draft Protocol released publicly in August 2009, and considers some of the commonalities and points of departure between this process and the WCD. The Forum's work on the Hydropower Sustainability Assessment Protocol is a work in progress, so this paper can describe but not give a full analysis of the work while it is in train.