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Among patients presenting acutely with ischaemic stroke who are being considered for intravenous thrombolysis, prompt brain imaging is used to exclude contraindications to treatment (chiefly haemorrhagic stroke or other conditions mimicking stroke) rather than to identify which patients are more or less likely to benefit from thrombolysis. For example, it is unclear whether the presence or absence of arterial obstruction on imaging should be used to guide thrombolysis treatment decisions. In this thesis I explore methods of imaging arterial patency among patients presenting acutely with ischaemic stroke and look for associations between these early imaging findings, response to intravenous thrombolysis and functional outcome six-months after stroke onset. I primarily use data from the Third International Stroke Trial (IST-3), the largest ever randomised-controlled trial testing the use of intravenous alteplase for the acute treatment of ischaemic stroke. I begin by summarising the main features of stroke, covering techniques for imaging the brain and for imaging arterial patency, and post-stroke outcomes. Next I describe two literature reviews which I compiled to increase my understanding of the topic with particular reference to imaging arterial patency. This is followed by a summary of IST-3. Then I describe the general methods I used to address my thesis aims exploring relationships between imaging characteristics of arterial patency, treatment with intravenous alteplase and functional outcome after ischaemic stroke. Specifically, I investigated the following imaging features: - The hyperattenuating artery sign (HAS), which is a non-contrast enhanced CT finding thought to be indicative of acute arterial obstruction by thrombus or embolus - Arterial patency or obstruction as demonstrated using contrast enhanced CT and MR angiographic imaging. In addition to providing better characterisation of the HAS and a better understanding of how angiography helps to assess ischaemic stroke patients, I found that arterial obstruction (however this is identified on imaging) is associated with more severe stroke at baseline and worse functional outcome six months after stroke. I also prove that intravenous alteplase is effective in the presence of arterial obstruction, counter to a widely held concern that it may not be effective in this context. Most of my work has been published in peer reviewed journals. My work should give front line clinicians greater confidence to use intravenous alteplase for the treatment of ischaemic stroke associated with arterial obstruction on imaging, but more work is needed to better understand the implications of apparently normal arterial patency on imaging among patients with ischaemic stroke.

The aim of this study was to assess the acute and post-acute services for ischaemic stroke patients in the Cape Metro Health District in relation to the South African ischaemic stroke guideline. Part A: Protocol - The protocol outlines the purpose of the study and highlights the importance of conducting this study by analysing the literature on stroke care in both high and low and middle-income countries. The literature also highlights the gaps in stroke care in South Africa which justify the need for this study. The protocol also outlines the methods of data collection and analysis as well as the ethical considerations. Part B: Literature Review - This expands on the literature on the different components of both acute and post-acute stroke care in both high and low and middle-income countries. It also elaborates on stroke in South Africa and why it is important to conduct this study. Part C: South African Medical Journal manuscript - The manuscript summarises the whole study and includes the literature on stroke care, justification of the study and how the data was collected and analysed. The manuscript also includes the results obtained and sections on the discussion and conclusions.

Ischaemic stroke occurs as a result of a blockage in one of the brain’s arteries, leading to neuronal injury and death. Although stroke is a major cause of death and disability, there is no widely available treatment. Inflammation occurs in the brain and in the periphery following stroke, and both contribute to the ischaemic damage. Leukocytes such as neutrophils are key mediators of brain damage and inflammation, particularly in the presence of systemic inflammatory challenges such as interleukin-1 (IL-1). Tumor necrosis factor-stimulated gene 6 (TSG-6) is a potent inhibitor of neutrophil migration, and also modulates the immune response by dampening expression of cytokines and stabilising the extra-cellular matrix (ECM). Mesenchymal stem cells (MSCs) have shown immunomodulatory actions in many inflammatory conditions, and their benefit has often been attributed to the production of TSG-6. This work aimed to evaluate the potential of TSG-6 and TSG-6-expressing MSCs as therapies in cerebral ischaemia, and to investigate the expression profile of endogenous TSG-6 in response to stroke. Mice were subjected to middle cerebral artery occlusion (MCAo) followed by reperfusion. We investigated whether IL-1-induced acute brain injury after stroke is reversed by TSG-6, and long-term recovery was evaluated in mice treated with TSG-6 or MSCs. Functional outcomes were assessed, and brains were sectioned and stained for analysis of lesion volume, haemorrhagic transformation, blood-brain barrier (BBB) disruption and neutrophil infiltration. The expression profile of TSG-6 was evaluated in mice allowed to recover for 4h, 24h, 3, 5 or 7 days. TSG-6 expression was determined by quantitative PCR and immunohistochemistry. Treatment with TSG-6 reduced IL-1-induced neutrophil infiltration into the striatum, and led to decreased BBB disruption and haemorrhagic transformation at 24h. Treatment with TSG-6 in the absence of a systemic inflammatory challenge had no significant effect on lesion volume, BBB disruption or haemorrhagic transformation after 7 days reperfusion, however thalamic neutrophil infiltration was significantly reduced. Treatment with human MSCs had no significant effect on behavioural or histological outcomes, however a heightened inflammatory response in MSC-treated mice suggested rejection of the cells by the murine immune system. TSG-6 expression peaked in the ischaemic hemisphere at 5 days post-reperfusion, and was associated with astrocytes in the glial scar surrounding the infarcted tissue. TSG-6 might be a promising therapy for the treatment of stroke in the presence of systemic inflammation. TSG-6-expressing MSCs might provide a broader therapeutic potential, and further work should optimise experimental conditions to prevent rejection of the cells. Expression of TSG-6 within the glial scar suggests a potential role in repair and recovery following ischaemic stroke. Modulating the peripheral immune response remains an attractive and accessible therapeutic target for the treatment of cerebral ischaemia.

Le pronostic à long-terme actuel après un accident ischémique transitoire (AIT) ou un infarctus cérébral reste mal connu. Ainsi, j’ai déterminé les risques absolus à long-terme de récidive d’infarctus cérébral et d’évènement coronarien aigu après un AIT ou un infarctus cérébral et identifié les individus qui restent à haut risque absolu de récidive ischémique malgré la prévention secondaire actuelle.Dans une cohorte populationnelle contemporaine de patients ayant eu un AIT ou un infarctus cérébral (OXVASC study, 2002-2014), les risques absolus de récidive d’infarctus cérébral et d’infarctus du myocarde après un AIT/infarctus cérébral ont significativement diminué au cours de la période d’étude, très probablement du fait de l’amélioration de la prévention secondaire avec le temps. Cependant, malgré la prévention secondaire actuelle les sous-groupes de patients avec un antécédent de pathologie coronarienne et ceux sans antécédent coronaire mais avec un score Essen 4 sont exposés à un risque absolu de récidive d’évènement ischémique suffisamment élevé pour justifier d’une intensification du traitement. Néanmoins, les thérapeutiques de prévention secondaire futures nécessitent de permettre d’obtenir une réduction absolue du risque de récidive d’évènement ischémique importante pour compenser un risque augmenté d’effets indésirables ou de surcoût par rapport aux thérapeutiques actuelles. En effet, chez ces sous-groupes de patients à haut risque de récidive ischémique, une réduction plus intensive du taux de cholestérol avec les inhibiteurs des PCSK-9 parait tout à fait justifiée, cependant nous avons montré que le coût de ces traitements excède la limite du rapport coût-efficacité généralement accepté tandis que le bénéfice d’une majoration du traitement antithrombotique semble contrebalancé par l’augmentation du risque hémorragique extracrânien. / The current long-term prognosis after transient ischaemic attack (TIA) or ischaemic stroke is not well known. I aimed to determine the long-term absolute residual risks of recurrent stroke and coronary events after TIA or ischaemic stroke and identify individuals who remain at high absolute risk of recurrent ischaemic events despite current secondary prevention management.In a population-based cohort of consecutive TIA or ischaemic stroke patients (OXVASC study, 2002-2014), the overall absolute risks of recurrent ischaemic stroke and coronary events after TIA/ischaemic stroke have decreased over the study period, and are likely to be explained by the improvement of secondary prevention over time. However, despite current secondary prevention, the subgroups of patients with prior coronary artery disease and those without prior coronary artery disease but with an Essen score of 4 remain at sufficiently high absolute risk of recurrent ischaemic events to justify more intensive treatment. Nevertheless, future secondary prevention therapies would need to achieve a substantial absolute risk reduction to outweigh increased side effects or cost compared to current therapies. Indeed, in these high-risk subgroups, more intensive lipid-lowering therapies might be justified, but we showed that the total cost of PCSK-9 inhibitors seems to exceed the generally accepted cost-effectiveness threshold while benefit from increased antithrombotic treatment might be offset by the higher risk of extracranial bleeding.

Ischaemic stroke represent more than 80% of the total stroke instances. The location of the occlusion and the amount of brain tissue involved determines the effect of the stroke. Stroke can result in paralysis, memory loss, speech impairment and even a “lock-in” state. The amount of neuronal damage will determine whether these symptoms will be temporary or permanent. Stroke is deemed the second leading cause of death for individuals over the age of 60. According to the World Stroke Organization (WSO) every six seconds stroke claims a life, regardless of age or gender. Stroke is a global burden and the medical costs and disability related to stroke in America for 2010 was projected at almost $73.7 billion. The morphology of platelets, fibrin networks and erythrocytes as well as the differential white blood cell counts of 20 thrombo-embolic ischaemic stroke patients were investigated. Internal and external alterations were revealed in the platelets of stroke patients when compared to healthy controls. The decreased numbers of alpha granules in the platelets of the stroke patients indicated these platelets to be activated. Substances released by activated platelets promote fibrin network structure, specifically the formation of fibrin strands and accumulation of additional platelets. The fibrin network of healthy individuals consists of major, thick fibers with minor, thin fibers distributed between them. The fibrin network of stroke patients exhibited an abnormally layered and matted ultrastructure comprising of mainly thin, minor fibrin fibers packed closely together. An uncharacteristic circular morphology was also observed. These alterations in the fibrin network indicate the activated platelets to be actively involved in the thrombotic event. Neuronal damage related to stroke is also advanced by the vasoactive substances released by activated platelets. It can therefore be deduced that the morphology of the fibrin network is altered long before the concrete thrombotic event transpire. Large numbers of abnormal erythrocytes were distinguished in the blood of stroke patients. Among these abnormal forms of erythrocytes specifically codocytes, knizocytes, stomatocytes and echinocytes were identified. Abnormal erythrocyte forms were significantly increased in hypertensive patients and females independently. Alterations in the ultrastructure of erythrocytes disturb blood flow in the microcirculation and could possibly augment the ischaemic event. Inflammation is closely related to ischaemic stroke. An increased monocyte count and a reduced number of neutrophils were a significant feature among all the stroke patients of this study. Patients with hypertension as well as patients consuming aspirin on a daily basis showed the greatest influence on the observed differential white blood cell counts. These morphological alterations observed in the platelets, fibrin network and erythrocytes as well as the differential white blood cell count could be incorporated in an analysis regime that could probably indicate an impending thrombotic event. Therefore treatment could be initiated before the ischaemic event to possibly prevent the stroke. For future studies a larger study population, a more refined patient enrolment as well as the analysis of follow-up blood samples from patients could substantiate the above-mentioned findings and provide additional information concerning the thrombotic event and the effectiveness of treatment procedures. / Dissertation (MSc)--University of Pretoria, 2010. / Anatomy / Unrestricted

Heat shock protein A12A (HSPA12A) is a newly discovered member of the Hsp70 family. The biological characteristics and functional roles of HSPA12A are poorly understood. This study investigated the effects of HSPA12A on ischaemic stroke in mice. Ischaemic stroke was induced by left middle cerebral artery occlusion for 1 h followed by blood reperfusion. We observed that HSPA12A was highly expressed in brain neurons, and neuronal HSPA12A expression was downregulated by ischaemic stroke and stroke-associated risk factors (aging, obesity and hyperglycaemia). To investigate the functional requirement of HSPA12A in protecting ischaemic brain injury, HSPA12A knockout mice (Hspa12a−/−) were generated. Hspa12a−/− mice exhibited an enlarged infarct volume and aggravated neurological deficits compared to their wild-type (WT) littermates after stroke. These aggravations in Hspa12a−/− mice were accompanied by more apoptosis and severer hippocampal morphological abnormalities in ischaemic hemispheres. Long-term examination revealed impaired motor function recovery and neurogenesis in stroke-affected Hspa12a−/− mice compared to stroke-affected WT controls. Significant reduced activation of GSK-3β/mTOR/p70S6K signalling was also observed in ischaemic hemispheres of Hspa12a−/− mice compared to WT controls. Administration with lithium (non-selective GSK-3β inhibitor) activated GSK-3β/mTOR/p70S6K signalling in stroke-affected Hspa12a−/− mice. Notably, lithium administration attenuated the HSPA12A deficiency-induced aggravation in infarct size, neurological deficits and neuronal death in Hspa12a−/− mice after stroke. Altogether, the findings suggest that HSPA12A expression encodes a critical novel prosurvival pathway during ischaemic stroke. We identified HSPA12A as a novel neuroprotective target for stroke patients.

Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine. Stroke is the leading cause of disability worldwide. HSPA12B, a heat-shock protein recently identified expression specifically in endothelial cells, is able to promote angiogenesis. Here, we have investigated its effects on functional recovery at chronic phase of ischaemic stroke. Ischaemic stroke was induced by 60 min. of middle cerebral artery occlusion in transgenic mice with overexpression of HSPA12B (HSPA12B Tg) and wild-type littermates (WT). HSPA12B Tg mice demonstrated a significant higher survival rate than WT mice within 28 days post-stroke. Significant improved neurological functions, increased spontaneous locomotor activity and decreased anxiety were detected inHSPA12B Tg mice compared with WT controls within 21 days post-stroke. Stroke-induced hippocampal degeneration was attenuated in HSPA12B Tg mice examined at day 28 post-stroke. Interestingly, HSPA12B Tg mice showed enhanced peri-infarct angiogenesis (examined 28 days post-stroke) and hippocampal neurogenesis (examined 7 days post-stroke), respectively, compared to WT mice. The stroke-induced eNOS phosphorylation and TGF-β1 expression were augmented in HSPA12B Tg mice. However, administration with eNOS inhibitor L-NAME diminished the HSPA12B-induced protection in neurological functional recovery and mice survival post-stroke. The data suggest that HSPA12B promoted functional recovery and survival after stroke in an eNOS-dependent mechanism. Targeting HSPA12B expression may have a therapeutic potential for the stroke-evoked functional disability and mortality.

In ischaemic stroke a disruption of cerebral blood flow leads to impaired metabolism and the formation of an ischaemic penumbra in which tissue at risk of infarction is sought for clinical intervention. In stroke trials, therapeutic intervention has largely been based on perfusion-weighted measures, but these have not been shown to be good predictors of tissue outcome. The aim of this thesis was to develop analysis techniques for magnetic resonance imaging (MRI) of chemical exchange saturation transfer (CEST) in order to quantify metabolic signals associated with tissue fate in patients with acute ischaemic stroke. This included addressing robustness for clinical application, and developing quantitative tools that allow exploration of the in-vivo complexity. Tissue-level analyses were performed on a dataset of 12 patients who had been admitted to the John Radcliffe Hospital in Oxford with acute ischaemic stroke and recruited into a clinical imaging study. Further characterisation of signals was performed on stroke models and tissue phantoms. A comparative study of CEST analysis techniques established a model-based approach, Bloch-McConnell model analysis, as the most robust for measuring pH-weighted signals in a clinical setting. Repeatability was improved by isolating non-CEST effects which attenuate signals of interest. The Bloch-McConnell model was developed further to explore whether more biologically-precise quantification of CEST effects was both possible and necessary. The additional model complexity, whilst more reflective of tissue biology, diminished contrast that distinguishes tissue fate, implying the biology is more complex than pH alone. The same model complexity could be used reveal signal patterns associated with tissue outcome that were otherwise obscured by competing CEST processes when observed through simpler models. Improved quantification techniques were demonstrated which were sufficiently robust to be used on clinical data, but also provided insight into the different biological processes at work in ischaemic tissue in the early stages of the disease. The complex array of competing processes in pathological tissue has underscored a need for analysis tools adequate for investigating these effects in the context of human imaging. The trends herein identified at the tissue level support the use of quantitative CEST MRI analysis as a clinical metabolic imaging tool in the investigation of ischaemic stroke.

Background: Patients with carotid artery dissection (CAD) have been reported to have different vascular risk factor profiles and clinical outcomes to those with vertebral artery dissection (VAD). However, there are limited data from recent, large international studies comparing risk factors and clinical features in patients with cervical artery dissection (CeAD) with other TIA or ischemic stroke (IS) patients of similar age and sex. Methods: We analysed demographic, clinical and risk factor profiles in TIA and IS patients ≤ 55 years of age with and without CeAD in the large European, multi-centre, Stroke In young FAbry Patients 1 (sifap1) study. Patients were further categorised according to age (younger: 18–44 years; middle-aged: 45–55 years), sex, and site of dissection. Results: Data on the presence of dissection were available in 4,208 TIA and IS patients of whom 439 (10.4%) had CeAD: 196 (50.1%) had CAD, 195 (49.9%) had VAD, and 48 had multiple artery dissections or no information regarding the dissected artery. The prevalence of CAD was higher in women than in men (5.9 vs. 3.8%, p < 0.01), whereas the prevalence of VAD was similar in women and men (4.6 vs. 4.7%, n.s.). Patients with VAD were younger than patients with CAD (median = 41 years (IQR = 35–47 years) versus median = 45 years (IQR = 39–49 years); p < 0.01). At stroke onset, about twice as many patients with either CAD (54.0 vs. 23.1%, p < 0.001) or VAD (63.4 vs. 36.6%, p < 0.001) had headache than patients without CeAD and stroke in the anterior or posterior circulation, respectively. Compared to patients without CeAD, hypertension, concomitant cardiovascular diseases and a patent foramen ovale were significantly less prevalent in both CAD and VAD patients, whereas tobacco smoking, physical inactivity, obesity and a family history of cerebrovascular diseases were found less frequently in CAD patients, but not in VAD patients. A history of migraine was observed at a similar frequency in patients with CAD (31%), VAD (27.8%) and in those without CeAD (25.8%). Conclusions: We identified clinical features and risk factor profiles that are specific to young patients with CeAD, and to subgroups with either CAD or VAD compared to patients without CeAD. Therefore, our data support the concept that certain vascular risk factors differentially affect the risk of CAD and VAD.