Over the past two decades developments in neuroimaging, especially in magnetic resonance imaging (MRI), have enabled enormous changes to be made in our knowledge and understanding of acute stroke. This knowledge is now being applied and extended in the clinical and translational research of the Stroke Neuroscience Unit at the National Institute of Neurological Disorders and Stroke. A recent advance in clinical MRI is rapid vascular imaging from the aortic arch to the circle of Willis using contrast-enhanced MR angiography (CE-MRA) and a neurovascular array. This has been evaluated and found to be a promising method for the rapid and early detection of extracranial vascular disease. CE-MRA may be added to acute stroke MRI protocols and could be of particular value for emergent decisions regarding acute stroke intervention (intravenous and intra-arterial thrombolysis), urgent surgical intervention and secondary stroke prevention. In new research applications, real-time, high resolution MRI is being combined with peripheral blood markers ? of gene and protein expression and inflammation - to study patterns of stroke risk, evolution and recovery. The peripheral blood is a practical source of samples as brain tissue is rarely available in the clinical setting. In a pilot study of patients with acute ischemic stroke confirmed on neuroimaging studies, a genomic fingerprint of acute stroke was defined and validated in peripheral blood mononuclear cells. The significance and potential applications of these results are under investigation: a 22 gene panel identified from the listing could form a basis for further diagnostic and prognostic fingerprinting of acute stroke. In further studies of the peripheral blood, expansion of a pro-inflammatory subset of T cell lymphocytes (CD4+CD28-) was found to be associated with stroke recurrence and death, in addition to being associated with prior stroke. Expansion of this T cell subset may occur after exposure to brain antigens, and may possibly be involved in the pathophysiological mechanisms leading to recurrent strokes and death. Ongoing and future studies include the correlation of genomic and proteomic profiles with MRI imaging patterns, and evaluation of their potential use for predicting stroke outcome and response to therapeutic interventions. A cohort from the Women?s Health Initiative is being followed to determine if a protein signature can be identified from the peripheral blood to predict future stroke risk. In bedside-to-bench studies, the pathogenic mechanisms and therapeutic potential of biomarkers such as CD4+CD28- are being determined, and promising candidate genes from gene expression profiling studies are being studied in genetic knock-out mouse models of stroke. In conjunction with accurate MR imaging patterns, these approaches may give information on new cellular and pathological mechanisms involved in the etiology and response to acute stroke, allow the development of surrogate biomarkers of stroke risk and prognosis, and ultimately lead to new drug therapies or preventive vaccines.
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