The complex dynamics of stroke onset and progression

NSF DARE-transforming modeling in neurorehabilitation: perspectives and opportunities from US funding agencies

In recognition of the importance and timeliness of computational models for accelerating progress in neurorehabilitation, the U.S. National Science Foundation (NSF) and the National Institutes of Health (NIH) sponsored a conference in March 2023 at the University of Southern California that drew global participation from engineers, scientists, clinicians, and trainees. This commentary highlights promising applications of computational models to understand neurorehabilitation ("Using computational models to understand complex mechanisms in neurorehabilitation" section), improve rehabilitation care in the context of digital twin frameworks ("Using computational models to improve delivery and implementation of rehabilitation care" section), and empower future interdisciplinary workforces to deliver higher-quality clinical care using computational models ("Using computational models in neurorehabilitation requires an interdisciplinary workforce" section). The authors describe near-term gaps and opportunities, all of which encourage interdisciplinary team science. Four major opportunities were identified including (1) deciphering the relationship between engineering figures of merit-a term commonly used by engineers to objectively quantify the performance of a device, system, method, or material relative to existing state of the art-and clinical outcome measures, (2) validating computational models from engineering and patient perspectives, (3) creating and curating datasets that are made publicly accessible, and (4) developing new transdisciplinary frameworks, theories, and models that incorporate the complexities of the nervous and musculoskeletal systems. This commentary summarizes U.S. funding opportunities by two Federal agencies that support computational research in neurorehabilitation. The NSF has funding programs that support high-risk/high-reward research proposals on computational methods in neurorehabilitation informed by theory- and data-driven approaches. The NIH supports the development of new interventions and therapies for a wide range of nervous system injuries and impairments informed by the field of computational modeling. The conference materials can be found at https://dare2023.usc.edu/ .

Use it and/or lose it-experience effects on brain remodeling across time after stroke

The process of brain remodeling after stroke is time- and neural activity-dependent, and the latter makes it inherently sensitive to behavioral experiences. This generally supports targeting early dynamic periods of post-stroke neural remodeling with rehabilitative training (RT). However, the specific neural events that optimize RT effects are unclear and, as such, cannot be precisely targeted. Here we review evidence for, potential mechanisms of, and ongoing knowledge gaps surrounding time-sensitivities in RT efficacy, with a focus on findings from animal models of upper extremity RT. The reorganization of neural connectivity after stroke is a complex multiphasic process interacting with glial and vascular changes. Behavioral manipulations can impact numerous elements of this process to affect function. RT efficacy varies both with onset time and its timing relative to the development of compensatory strategies with the less-affected (nonparetic) hand. Earlier RT may not only capitalize on a dynamic period of brain remodeling but also counter a tendency for compensatory strategies to stamp-in suboptimal reorganization patterns. However, there is considerable variability across injuries and individuals in brain remodeling responses, and some early behavioral manipulations worsen function. The optimal timing of RT may remain unpredictable without clarification of the cellular events underlying time-sensitivities in its effects.

Role of inflammation and its mediators in acute ischemic stroke

Inflammation plays an important role in the pathogenesis of ischemic stroke and other forms of ischemic brain injury. Increasing evidence suggests that inflammatory response is a double-edged sword, as it not only exacerbates secondary brain injury in the acute stage of stroke but also beneficially contributes to brain recovery after stroke. In this article, we provide an overview on the role of inflammation and its mediators in acute ischemic stroke. We discuss various pro-inflammatory and anti-inflammatory responses in different phases after ischemic stroke and the possible reasons for their failures in clinical trials. Undoubtedly, there is still much to be done in order to translate promising pre-clinical findings into clinical practice. A better understanding of the dynamic balance between pro- and anti-inflammatory responses and identifying the discrepancies between pre-clinical studies and clinical trials may serve as a basis for designing effective therapies.

Comparative effectiveness research on patients with acute ischemic stroke using Markov decision processes

Background

Several methodological issues with non-randomized comparative clinical studies have been raised, one of which is whether the methods used can adequately identify uncertainties that evolve dynamically with time in real-world systems. The objective of this study is to compare the effectiveness of different combinations of Traditional Chinese Medicine (TCM) treatments and combinations of TCM and Western medicine interventions in patients with acute ischemic stroke (AIS) by using Markov decision process (MDP) theory. MDP theory appears to be a promising new method for use in comparative effectiveness research.

Methods

The electronic health records (EHR) of patients with AIS hospitalized at the 2^nd Affiliated Hospital of Guangzhou University of Chinese Medicine between May 2005 and July 2008 were collected. Each record was portioned into two "state-action-reward" stages divided by three time points: the first, third, and last day of hospital stay. We used the well-developed optimality technique in MDP theory with the finite horizon criterion to make the dynamic comparison of different treatment combinations.

Results

A total of 1504 records with a primary diagnosis of AIS were identified. Only states with more than 10 (including 10) patients' information were included, which gave 960 records to be enrolled in the MDP model. Optimal combinations were obtained for 30 types of patient condition.

Conclusion

MDP theory makes it possible to dynamically compare the effectiveness of different combinations of treatments. However, the optimal interventions obtained by the MDP theory here require further validation in clinical practice. Further exploratory studies with MDP theory in other areas in which complex interventions are common would be worthwhile.

The autonomic nervous system and ischemic stroke: a reciprocal interdependence

Signs and symptoms of autonomic nervous system (ANS) dysfunction are frequently reported after ischemic or haemorrhagic stroke and in many cases they exhibit peculiar patterns in relationship with the site and the extension of brain lesion. However if an ANS disorder can cause or predispose to a stroke is far from being correctly known. Evidences in favor of a pathogenetic mechanism of an ANS dysfunction are reported for myocardial infarction and such data are likely to be appropriate also for atherothrombotic type of ischemic stroke. On the other hand, it is well known that many risk factors for this pathology are strongly correlated with an altered functioning of ANS so that a reciprocal interdependence between ANS and stroke can be hypothesized. This review points to evidence the possible relationship existing between these two conditions and suggests a quite different diagnostic and therapeutic approach to both on the basis of their pathogenetic mechanisms.

Assessment of aortic pathology and peripheral arterial disease using multidetector computed tomographic angiography

The development of multidetector computed tomography represents a remarkable diagnostic advancement because this imaging modality has been widely used in the evaluation of the cardiovascular system. With scanner-adjusted image acquisition and contrast medium administration, multidetector computed tomographic angiography provides a cost-effective and accurate imaging assessment in patients with aortic pathologies or peripheral arterial occlusive disease. Multidetector computed tomographic angiography is associated with several advantages, including high image spatial resolution and rapid imaging acquisition speed. This diagnostic methodology allows accurate detection of a variety of intravascular lesions in the carotid artery, thoracic and abdominal aorta, renal arteries, and peripheral arterial systems. This article provides an overview of multidetector computed tomographic angiography in the assessment of arterial disease and reviews current literature about this diagnostic technology in the evaluation of aortic and peripheral arterial pathologies.