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Cerebral collateral circulation is a network of blood vessels which stabilizes blood flow and maintains cerebral perfusion whenever the main arteries fail to provide an adequate blood supply, as happens in ischemic stroke. These arterial networks are able to divert blood flow to hypoperfused cerebral areas. The extent of the collateral circulation determines the volume of the salvageable tissue, the so-called “penumbra”. Clinically, this is associated with greater efficacy of reperfusion therapies (thrombolysis and thrombectomy) in terms of better short- and long-term functional outcomes, lower incidence of hemorrhagic transformation and of malignant oedema, and smaller cerebral infarctions. Recent advancements in brain imaging techniques (CT and MRI) allow us to study these anastomotic networks in detail and increase the likelihood of making effective therapeutic choices. In this narrative review we will investigate the pathophysiology, the clinical aspects, and the possible diagnostic and therapeutic role of collateral circulation in acute ischemic stroke.

The brains of humans and other mammals are highly vulnerable to interruptions in blood flow and decreases in oxygen levels. Here we describe the restoration and maintenance of microcirculation and molecular and cellular functions of the intact pig brain under ex vivo normothermic conditions up to four hours post-mortem. We have developed an extracorporeal pulsatile-perfusion system and a haemoglobin-based, acellular, non-coagulative, echogenic, and cytoprotective perfusate that promotes recovery from anoxia, reduces reperfusion injury, prevents oedema, and metabolically supports the energy requirements of the brain. With this system, we observed preservation of cytoarchitecture; attenuation of cell death; and restoration of vascular dilatory and glial inflammatory responses, spontaneous synaptic activity, and active cerebral metabolism in the absence of global electrocorticographic activity. These findings demonstrate that under appropriate conditions the isolated, intact large mammalian brain possesses an underappreciated capacity for restoration of microcirculation and molecular and cellular activity after a prolonged post-mortem interval. A specialized technology can restore and preserve microcirculation and cellular functions hours post-mortem in an isolated pig brain.

We study international mobility in academia, with a focus on the migration of published researchers to and from Russia. Using an exhaustive set of over 2.4 million Scopus publications, we analyze all researchers who have published with a Russian affiliation address in Scopus-indexed sources in 1996–2020. The migration of researchers is observed through the changes in their affiliation addresses, which altered their mode countries of affiliation across different years. While only 5.2% of these researchers were internationally mobile, they accounted for a substantial proportion of citations. Our estimates of net migration rates indicate that while Russia was a donor country in the late 1990s and early 2000s, it has experienced a relatively balanced circulation of researchers in more recent years. These findings suggest that the current trends in scholarly migration in Russia could be better framed as brain circulation, rather than as brain drain. Overall, researchers emigrating from Russia outnumbered and outperformed researchers immigrating to Russia. Our analysis on the subject categories of publication venues shows that in the past 25 years, Russia has, overall, suffered a net loss in most disciplines, and most notably in the five disciplines of neuroscience, decision sciences, mathematics, biochemistry, and pharmacology. We demonstrate the robustness of our main findings under random exclusion of data and changes in numeric parameters. Our substantive results shed light on new aspects of international mobility in academia, and on the impact of this mobility on a national science system, which have direct implications for policy development. Methodologically, our novel approach to handling big data can be adopted as a framework of analysis for studying scholarly migration in other countries.

The devastating russian military invasion of Ukraine forced millions of people to flee their homes. Among those affected are highly skilled scientists, resulting in a significant loss of human capital for Ukraine, which is crucial for the post-war reconstruction. To address this pressing issue, the Young Scientists Council (YSC) at the Ministry of Education and Science of Ukraine launched the “Ukrainian Science Diaspora” initiative to mitigate the brain drain.The purpose of this study is to outline the first steps taken by this initiative. Moreover, it demonstrates lessons learned from the pilot meetings. The essence of the initiative is to keep links with scholars who left Ukraine and join the efforts of different migration waves of Ukrainian scientists for the further rebuilding of Ukraine. The YSC and other institutions prepared the analytical report on the needs and plans of Ukrainian scientists abroad. In addition, the paper highlights various events and activities organized by the YSC and other self-formed associations of Ukrainian scientists worldwide, working together to establish networks that could take the form of public organizations or be part of local unions of scientists. At present, efforts are focused on identifying Ukrainian scientists interested in joining this initiative, with the ultimate goal of identifying areas where Ukrainian scientists can participate in post-war reconstruction. The success of this initiative will undoubtedly play a crucial role in ensuring that Ukraine can retain its valuable human capital and continue to thrive in the face of adversity. AcknowledgmentThis study is co-funded by the European Union through the European Education and Culture Executive Agency (EACEA) within the project “Europeanisation of Doctoral Studies in Line with the Innovative Doctoral Training Principles in Europe: Towards a Common Future” 101083493 – EDOCS – ERASMUS-JMO-2022-HEI-TCH-RSCH https://edocs.snau.edu.ua/en/

The phenomenon of scientific mobility, actively developing in recent decades, attracts increasing attention of researchers in view of its importance for the development of science, dissemination of scientific knowledge, making informed decisions in the management of science and training of qualified personnel. Based on an extensive analysis of the literature on the topic in the last 30 years with the use of bibliometric approaches, this paper outlines the main evolutionary stages of scientific mobility in the context of brain drain and circulation concepts; considers relations, advantages and disadvantages of scientific mobility in relation to scientific inbreeding; describes the main approaches and methodological aspects formed today in the study of the scientists mobility; discusses its positive and negative consequences for researchers, organizations, countries, and individual disciplines, and summarizes the motivations and driving forces of scientists when leaving the country and when returning.

Brain abscess (BA) is a severe neurological emergency, which remains a challenge for physicians despite medical advancements. The purpose of this study is to describe the epidemiology of BA in Taiwan and to investigate potential factors affecting the survival of patients with BA. By using the Taiwan National Health Insurance Research Database, we identified hospitalized patients with a discharge diagnosis of pyogenic BA (324.X) between 2000 and 2013. The incidence and in-hospital mortality of BA were calculated based on both age and sex. A total of 6027 BA cases were identified. The overall incidence of BA was 1.88 (95% CI: 1.83-1.93) per 100,000 person-years and increased with age, from 0.58 per 100,000 person-years in individuals aged 0-14 years to 4.67 per 100,000 person-years in those over 60 years of age. The male-to-female incidence ratio was 2.37 (95% CI: 2.24-2.50), with a mountain-shaped distribution across ages peaking at 40-44 years. The in-hospital mortality also increased with age, from 4.22% (95% CI: 2.54-6.97) at 0-14 years to 17.34% (95% CI: 15.79-19.02) in individuals over 60 years of age, without a gender difference (11.9% for males, 12.5% for females). Age, stroke, septicemia, pneumonia, meningitis, and hepatitis were associated with increased risk of in-hospital mortality. There was a male predominance for BA, and both the incidence and in-hospital mortality rates increased with age. Infection-related disease such as septicemia, pneumonia and meningitis were important factors associated with in-hospital mortality. In addition to the original treatment of BA, we suggest paying close attention to potential infections to improve the outcome of BA patients.

Key Points Summary points that barrier scientists and neuroscientists need to collaborate on: The neurovascular unit (NVU; comprising cellular and acellular elements of brain vessels, parenchymal cells and peripheral immune cells) incorporates three main functionalities — blood–brain barrier, neuroimmune axis and regulation of the cerebral blood flow — that are tightly integrated in brain physiology and play a part in the pathogenesis of numerous neurological diseases. Exchange of information, nutrients and molecules between systemic and central compartments is controlled by the myriad of NVU transporters, which become dysfunctional in brain diseases such as epilepsy, brain tumours and Alzheimer's disease. Targeting the intracellular signalling pathways that regulate selective blood–brain barrier transporters can potentially be used to enhance brain drug delivery, protect the brain from xenobiotics and prevent the pathogenesis and/or slow the progression of CNS diseases. Neurogenesis and angiogenesis are co-regulated in embryonic and adult brains and are often controlled by the same classes of mediators. Novel methods for co-ordinated stimulation of both neuronal and vascular regeneration will be essential to develop successful brain repair strategies. Progress in understanding and treating brain disease is contingent upon better understanding of the integral function of the NVU in disease, advancing the means to interrogate molecular and functional aspects of the NVU, and the development of strategies to deliver therapeutics across the blood–brain barrier. New high resolution imaging techniques are providing stubstantial advances in the blood–brain barrier field and have a powerful potential for further progress. In particular, in vivo two-photon imaging studies of interactions of glial cells and blood cells with the blood–brain barrier are required to compose an integrated picture of blood–brain barrier regulation and function. A great many aspects of neuronal physiology and pathology involve or affect the brain barriers. Recent insights into the role of the blood–brain barrier during development, and advances in our understanding of how it affects neurological disorders, have led to closer links between the two topics. The delivery of many potentially therapeutic and diagnostic compounds to specific areas of the brain is restricted by brain barriers, of which the most well known are the blood–brain barrier (BBB) and the blood–cerebrospinal fluid (CSF) barrier. Recent studies have shown numerous additional roles of these barriers, including an involvement in neurodevelopment, in the control of cerebral blood flow, and — when barrier integrity is impaired — in the pathology of many common CNS disorders such as Alzheimer's disease, Parkinson's disease and stroke.

A large variety of severe medical conditions involve alterations in microvascular circulation. Hence, measurements or simulation of circulation and perfusion has considerable clinical value and can be used for diagnostics, evaluation of treatment efficacy, and for surgical planning. However, the accuracy of traditional tracer kinetic one-compartment models is limited due to scale dependency. As a remedy, we propose a scale invariant mathematical framework for simulating whole brain perfusion. The suggested framework is based on a segmentation of anatomical geometry down to imaging voxel resolution. Large vessels in the arterial and venous network are identified from time-of-flight (ToF) and quantitative susceptibility mapping (QSM). Macro-scale flow in the large-vessel-network is accurately modelled using the Hagen-Poiseuille equation, whereas capillary flow is treated as two-compartment porous media flow. Macro-scale flow is coupled with micro-scale flow by a spatially distributing support function in the terminal endings. Perfusion is defined as the transition of fluid from the arterial to the venous compartment. We demonstrate a whole brain simulation of tracer propagation on a realistic geometric model of the human brain, where the model comprises distinct areas of grey and white matter, as well as large vessels in the arterial and venous vascular network. Our proposed framework is an accurate and viable alternative to traditional compartment models, with high relevance for simulation of brain perfusion and also for restoration of field parameters in clinical brain perfusion applications.

Objective Posterior circulation ischemic stroke (PCiS) constitutes 20–30% of ischemic stroke cases. Detailed information about differences between PCiS and anterior circulation ischemic stroke (ACiS) remains scarce. Such information might guide clinical decision making and prevention strategies. We studied risk factors and ischemic stroke subtypes in PCiS vs. ACiS and lesion location on magnetic resonance imaging (MRI) in PCiS. Methods Out of 3,301 MRIs from 12 sites in the National Institute of Neurological Disorders and Stroke (NINDS) Stroke Genetics Network (SiGN), we included 2,381 cases with acute DWI lesions. The definition of ACiS or PCiS was based on lesion location. We compared the groups using Chi-squared and logistic regression. Results PCiS occurred in 718 (30%) patients and ACiS in 1663 (70%). Diabetes and male sex were more common in PCiS vs. ACiS (diabetes 27% vs. 23%, p  < 0 .05 ; male sex 68% vs. 58%, p  < 0.001). Both were independently associated with PCiS (diabetes, OR = 1.29; 95% CI 1.04–1.61; male sex, OR = 1.46; 95% CI 1.21–1.78). ACiS more commonly had large artery atherosclerosis (25% vs. 20%, p  < 0.01) and cardioembolic mechanisms (17% vs. 11%, p  < 0.001) compared to PCiS. Small artery occlusion was more common in PCiS vs. ACiS (20% vs. 14%, p  < 0.001). Small artery occlusion accounted for 47% of solitary brainstem infarctions. Conclusion Ischemic stroke subtypes differ between the two phenotypes. Diabetes and male sex have a stronger association with PCiS than ACiS. Definitive MRI-based PCiS diagnosis aids etiological investigation and contributes additional insights into specific risk factors and mechanisms of injury in PCiS.

International academic mobility is associated with higher research productivity, collaboration, and impact, but national-level evidence from low- and middle-income countries remains scarce. This study presents a large-scale bibliometric analysis of international mobility among Brazilian researchers in health and life sciences, using Scopus data (2005–2020). We analyzed over 1.3 million publications by 214,263 researchers with at least one Brazilian affiliation. Researchers were classified into five mobility categories (Nonmobile, Emigrants, Returnees, Immigrants, Visitors) using longitudinal affiliation data. We mapped mobility patterns and disciplinary variation, then applied propensity score matching to compare research performance across groups on citations, journal prestige, and international collaboration. Although only 15% of researchers exhibited international mobility, they contributed 59% of total publications. Mobile researchers consistently outperformed nonmobile peers across all performance metrics. Notably, 68% of mobile researchers returned to Brazil, with Returnees showing citation impact comparable to Emigrants. Immigrants demonstrated lower performance than Emigrants, suggesting a limited compensation effect for outbound talent loss. These findings provide the first large-scale mapping of researcher mobility in Brazil and demonstrate how bibliometric methods can inform national strategies. We argue that shifting from a “brain drain” toward a “brain circulation” framework can better leverage international experience to strengthen national research capacity.