Positron Emission Tomography (PET) in Acute Ischemic Stroke: Pathophysiological and Clinical Implications
Experimental studies in animal stroke models have shown that, at variance with global ischemia from cardiac arrest, the abrupt occlusion of a cerebral artery (e.g. the trunk of the middle cerebral artery, MCA) triggers complex regulatory mechanisms that tend to compensate for the decrease in perfusion pressure, such as distal bed vasodilatation and subsequent ‘opening’ of pial anastomoses. This results in a gradient of reduction in cerebral blood flow (CBF) and tissue oxygenation from the ischemic core, where perfusion is most reduced or may even be arrested, towards the borders of the affected vascular territory, where CBF may be only mildly reduced (oligemia) or even normal (autoregulated) (Pulsinelli 1992). The concept of the ‘ischemic penumbra’ dictates that, in each block of tissue, the level of residual perfusion will determine to what degree the cascade of ischemic-dependent biochemical events is triggered.
KeywordsMigration Depression Ischemia Neurol Peri
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