“The evolution of hemodynamics during stroke recovery: from early hours to subsequent weeks”
Hosted by the Department of Biomedical Engineering (BME)
Faculty host: Song Hu (WashU BME)
Abstract: The dynamics of vascular and tissue damage following stroke are complex and highly integrative mechanisms that begin within a few minutes and lead to the loss of sensory and motor function . Some spontaneous behavioral recovery is usually seen in the weeks to months following a stroke . Correspondingly, various MRI techniques are used extensively to characterize and monitor stroke progression both in the acute and chronic stages [4,5]. However, the interpretations of these MR signals in terms of the underlying physiology are still poorly understood.
In the acute phase, perfusion weighted imaging (PWI) and diffusion weighted imaging (DWI) are MRI techniques used to characterize the extent of a stroke . The perfusion-diffusion mismatch, indicative of “tissue at risk”, is used to guide acute interventions such as thrombolysis. Reperfusion following transient ischemia, either spontaneously or through acute interventions, have shown temporary reversal of the DWI lesion, which may depend on the extent of tissue reperfusion . However, recanalization of the occluded vessel does not always lead to improved recovery. We hypothesize that recanalization is not sufficient for improved tissue outcome and that recanalization needs to be accompanied with capillary reperfusion in order to improve functional outcome. Additionally, fMRI, which shows hemodynamic responses to brain activation, is a valuable tool for longitudinal monitoring of stroke patients . These signals can be very useful as an objective evaluation of recovery, comparing treatments, as well as perhaps providing a long-term predictor of better recovery. Potential alterations in neurovascular coupling, structural changes in the underlying vasculature, and changes in baseline blood flow and blood volume following a stroke can confound fMRI measurements and make the signals difficult to interpret.
Therefore, preclinical animal studies are needed to evaluate the structural and functional consequences of stroke in the acute and chronic stages of stroke recovery to better understand MRI data . Towards this goal, we have optimized a translatable rodent model that more closely mimics the biology of a human stroke and allows long-term monitoring of recovery mechanisms through imaging. Utilizing multimodal imaging strategies and quantifying cerebral hemodynamics, we have identified acute and chronic prognostic indicators of functional recovery.
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