Search

The processes of normal aging and aging-related pathologies subject the brain to an active re-organization of its brain networks. Among these, the default-mode network (DMN) is consistently implicated with a demonstrated reduction in functional connectivity within the network. However, no clear stipulation on the underlying mechanisms of the de-synchronization has yet been provided. In this study, we examined the spectral distribution of the intrinsic low-frequency oscillations (LFOs) of the DMN sub-networks in populations of young normals, older subjects, and acute and subacute ischemic stroke patients. The DMN sub-networks were derived using a mid-order group independent component analysis with 117 eyes-closed resting-state functional magnetic resonance imaging (rs-fMRI) sessions from volunteers in those population groups, isolating three robust components of the DMN among other resting-state networks. The posterior component of the DMN presented noticeable differences. Measures of amplitude of low-frequency fluctuation (ALFF) and fractional ALFF (fALFF) of the network component demonstrated a decrease in resting-state cortical oscillation power in the elderly (normal and patient), specifically in the slow-5 (0.01-0.027 Hz) range of oscillations. Furthermore, the contribution of the slow-5 oscillations during the resting state was diminished for a greater influence of the slow-4 (0.027-0.073 Hz) oscillations in the subacute stroke group, not only suggesting a vulnerability of the slow-5 oscillations to disruption but also indicating a change in the distribution of the oscillations within the resting-state frequencies. The reduction of network slow-5 fALFF in the posterior DMN component was found to present a potential association with behavioral measures, suggesting a brain-behavior relationship to those oscillations, with this change in behavior potentially resulting from an altered network integrity induced by a weakening of the slow-5 oscillations during the resting state. The repeated identification of those frequencies in the disruption of DMN stresses a critical role of the slow-5 oscillations in network disruption, and it accentuates the importance of managing those oscillations in the health of the DMN.

Background: Ischaemic stroke interrupts the flow of blood to part of the brain. Haemodilution is thought to improve the flow of blood to the affected areas of the brain and thus reduce infarct size., Objectives: To assess the effects of haemodilution in acute ischaemic stroke., Search Methods: We searched the Cochrane Stroke Group Trials Register (February 2014), the Cochrane Central Register of Controlled Trials (Issue 1, 2014), MEDLINE (January 2008 to October 2013) and EMBASE (January 2008 to October 2013). We also searched trials registers, scanned reference lists and contacted authors. For the previous version of the review, the authors contacted manufacturers and investigators in the field., Selection Criteria: Randomised trials of haemodilution treatment in people with acute ischaemic stroke. We included only trials in which treatment was started within 72 hours of stroke onset., Data Collection and Analysis: Two review authors assessed trial quality and one review author extracted the data., Main Results: We included 21 trials involving 4174 participants. Nine trials used a combination of venesection and plasma volume expander. Twelve trials used plasma volume expander alone. The plasma volume expander was plasma alone in one trial, dextran 40 in 12 trials, hydroxyethyl starch (HES) in five trials and albumin in three trials. Two trials tested haemodilution in combination with another therapy. Evaluation was blinded in 14 trials. Five trials probably included some participants with intracerebral haemorrhage. Haemodilution did not significantly reduce deaths within the first four weeks (risk ratio (RR) 1.10; 95% confidence interval (CI) 0.90 to 1.34). Similarly, haemodilution did not influence deaths within three to six months (RR 1.05; 95% CI 0.93 to 1.20), or death and dependency or institutionalisation (RR 0.96; 95% CI 0.85 to 1.07). The results were similar in confounded and unconfounded trials, and in trials of isovolaemic and hypervolaemic haemodilution. No statistically significant benefits were documented for any particular type of haemodiluting agents, but the statistical power to detect effects of HES was weak. Six trials reported venous thromboembolic events. There was a tendency towards reduction in deep venous thrombosis or pulmonary embolism or both at three to six months' follow-up (RR 0.68; 95% CI 0.37 to 1.24). There was no statistically significant increased risk of serious cardiac events among haemodiluted participants., Authors' Conclusions: The overall results of this review showed no clear evidence of benefit of haemodilution therapy for acute ischaemic stroke.These results are compatible with no persuasive beneficial evidence of haemodilution therapy for acute ischaemic stroke. This therapy has not been proven to improve survival or functional outcome.

Stroke is common, with a high rate of disability and death, and current therapies are both highly time sensitive and carry some risk, making rapid diagnosis important. Many cases of stroke are difficult to diagnose clinically during the acute phase, and there are limitations to the ability of diagnostic imaging to help with the necessary speed. A reliable and valid biomarker would be invaluable for this common clinical situation, as it has been with myocardial infarction. A large number of molecules have been evaluated for this role, both in the laboratory and in patients, but the results to date have been disappointing. In this article, we review the operative concepts in the search for a diagnostic biomarker of stroke, a few of the promising candidates and the current challenges to validation.

It is well established that several infectious diseases can directly lead to ischemic or hemorrhagic stroke during their course. It appears possible that common viral and bacterial infections can increase the susceptibility to stroke by promoting atherosclerosis, inflammation, and local thrombosis. Stroke commonly leads to disruption of protective mechanisms against infection and induces a cascade of anti-inflammatory and immunosuppressive reactions, which greatly increases the risk of infection. The social and economic costs of post-stroke infections and their impact on stroke morbidity and outcome are dramatic. Understanding the pathophysiologic links between stroke and infection is therefore of paramount importance, and effective preventive strategies to reduce the risk of infection are needed. This article summarizes current clinical and experimental data regarding the interactions between stroke and infection and outlines possible targets for therapeutic intervention.

Background: Ischemic stroke and transient ischemic attack can be difficult to diagnose clinically, and both acute and preventive therapies carry some risk. Serum biomarkers could increase diagnostic certainty by helping to distinguish cerebral ischemia from common mimics such as focal seizure, complicated migraine, and psychogenic spells. Biomarkers could also identify patients at high risk for future vascular events, which would aid in management decisions., Review Summary: There are many potential obstacles to finding these biomarkers, which are reviewed here, including the blood brain barrier, confounding by other conditions, and imperfect gold standards for use in validation. Diagnostic biomarkers are likely to be molecules found predominantly in brain tissue with rapid entry into the blood, whereas risk-stratification biomarkers may be related to the concept of an active atherosclerotic plaque. Many promising serum molecules have been examined in small series of patients with cerebrovascular disease., Conclusion: Large series examining many candidate molecules will be needed to find valid biomarkers, and this should be followed by use in future intervention trials to prove their utility.

Ischemic stroke is a leading cause of death and disability, and current treatments to limit tissue injury and improve recovery are limited. Cerebral infarction is accompanied by intense brain tissue inflammation involving many inflammatory cell types that may cause both negative and positive effects on outcomes. Many potential neuroprotective and neurorestorative treatments may affect, and be affected by, this inflammatory cell infiltration, so that accurate quantification of this tissue response is needed. We performed a systematic review of histological methods to quantify brain tissue inflammatory cell infiltration after cerebral infarction. We found reports of multiple techniques to quantify different inflammatory cell types. We found no direct comparison studies and conclude that more research is needed to optimize the assessment of this important stroke outcome. [ABSTRACT FROM AUTHOR]

Objective: Prophylactic antiseizure drugs (PAD) are commonly prescribed for non-traumatic intracerebral hemorrhage (ICH) despite limited evidence for this indication. We sought to determine the current prescribing patterns of the use of a PAD for ICH. Methods: A 36-item survey was distributed to physicians who manage ICH patients soliciting details of PAD prescription in their practice. Results: A total of 199 physicians responded to the survey, all of who manage 50 or more ICH patients per year. The respondents were neurologists (32%), neurosurgeons (11%), and intensivists (57%) in academia (69%) and private practice (31%). Prophylactic antiseizure drugs prescriptions used: never (33%), 1-33% (35%), 34-66% (14%), 67-99% (9%) of the time, or always (9%). Most respondents performed electroencephalographic and serum level monitoring in at least some patients. Levetiracetam was used most often (60%), followed by fosphenytoin (37%), for a usual duration of days (36%), weeks (47%), or months (17%). Prophylactic antiseizure drugs prescription varied by patient characteristics and physician specialty. Perception of physician community consensus regarding PAD use for ICH among respondents ranged from strongly (7%) or weakly (23%) against the practice, to a fairly equal division of opinion (41%), to weakly (27%) or strongly (4%) in favor of the practice. Conclusions: We found variability of multiple aspects of the current prescribing patterns and opinions regarding the use of a PAD for ICH. This variability is likely secondary to insufficient data. Clinical equipoise exists for this issue, and controlled trials would be both justified and useful. [ABSTRACT FROM AUTHOR]

Accurate histological quantification of astrocytosis after cerebral infarction is needed as this process may affect, and be affected by, many potential restorative treatments under investigation. We performed a systematic review to determine the most reliable histological method reported for measurement of postinfarction astrocytosis. We found reports of multiple techniques to quantify various parameters of immunohistochemical staining for the astrocyte marker glial fibrillary acidic protein on photomicrographs with several software packages. We found no studies directly comparing techniques. We conclude that the reported methods seem reasonable, but the descriptions were often insufficiently detailed to allow for replication, and the lack of comparison data makes the best method unclear. Further research is needed to optimize the analysis of this important tissue outcome after cerebral infarction. [ABSTRACT FROM AUTHOR]

Background: Although administration of various stem cells has shown promise in stroke models, neural stem cells (NSCs) derived from human induced pluripotent stem cells (iPSCs) have advantages over other cell types. We studied whether these cells could survive, differentiate, and improve stroke recovery in an ischemic stroke model. Methods: Human iPSCs were induced in vitro to an early NSC stage. One week after focal cerebral ischemia, 20 rats received cells or vehicle by intracerebral injection. Graft cell fate, infarct volume, and behavioral deficits were assessed. Results: Graft cells were found in 8 of the transplanted rats (80%), with estimated mean graft cell numbers nearly double the amount transplanted 1 month later. Graft cells also expressed markers of NSCs in 5 rats (63%), neurons in all 8 rats (100%), rare astrocytes in 4 rats (50%), and signs of proliferation in 4 rats (50%), but no tumor formation was observed. Stroke volume and behavioral recovery were similar between the groups. Conclusions: To our knowledge, this is the first report of transplantation of NSCs derived from human iPSCs in a stroke model. Human iPSC-derived NSCs survived in the postischemic rat brain and appeared to differentiate, primarily into neurons. This cell transplantation approach for stroke appears to be feasible, but further optimization is needed. [Copyright &y& Elsevier]

Ischemic stroke is a leading cause of disability, and current treatments to improve recovery are limited. Part of the natural recovery process after brain injury is angiogenesis. The formation of new blood vessels around the infarct appears to be important for restoration of adequate perfusion to allow for healing of brain tissue. Many potential restorative treatments may affect, and be affected by, angiogenesis, so accurate quantification of this outcome is needed. We performed a systematic review of histological methods to quantify angiogenesis after cerebral infarction. We found reports of the use of a variety of histological and general and immunostaining techniques in conjunction with a variety of analysis methods. We found no direct comparison studies and concluded that more research is needed to optimize the assessment of this important stroke outcome. [ABSTRACT FROM AUTHOR]

Stroke is a leading cause of death and disability, leading to the development of various stroke models to test new treatments, most commonly in the rat. Human stroke trials focus on disability, related primarily to neurological deficits. To better model the clinical application of these treatments, many behavioral tests have been developed using the rat stroke model. We performed a systematic review of all the behavioral outcome measures used in published studies of human neural stem cell transplantation in rat stroke models. The reviewed tests include motor, sensory, cognitive, activity, and combination tests. For each test, we give a brief description, trace the origin of the test, and discuss test performance in the reviewed studies. We conclude that while many behavioral tests are available for this purpose, there does not appear to be consensus on an optimal testing strategy. [ABSTRACT FROM AUTHOR]

Reversible cerebral vasoconstriction syndrome (RCVS) is a cerebrovascular disorder associated with multifocal arterial constriction and dilation. RCVS is associated with nonaneurysmal subarachnoid hemorrhage, pregnancy and exposure to certain drugs. The primary clinical manifestation is recurrent sudden-onset and severe ('thunderclap') headaches over 1-3 weeks, often accompanied by nausea, vomiting, photophobia, confusion and blurred vision. The primary diagnostic dilemma is distinguishing RCVS from primary CNS arteritis. Diagnosis requires demonstration of the characteristic 'string of beads' on cerebral angiography with resolution within 1-3 months, although many patients will initially have normal vascular imaging. Many treatments have been reported to ameliorate the headaches of RCVS, but it is unclear whether they prevent hemorrhagic or ischemic complications. INSET: Key issues. [ABSTRACT FROM AUTHOR]