Postischemic hyperperfusion

KaribeH.,ZarowG. J., GrahamS. H., and WeinsteinP.R. (1994) Mild intraischemic hypothermia reduces postischemic hyperperfusion, delayed postischemic hypoperfusion, blood-brain barrier disruption, brain edema, and neuronal damage volume after temporary focal cerebral ischemia in rats. J. Cereb. Blood Flow Metab. 14, 620-627. 

In many acnte stroke patients, spontaneons resoln-tion of the arterial lesion(s) before the time of presentation resnlts in spontaneous reperfusion of some or all of the previously ischemic tissue. Various studies have found that spontaneous reperfusion occurs in 16% of patients scanned within 8 h of stroke onset [10], and 33% of patients scanned within 48 h of onset [11], hi this reperfused tissue, vasodilation that persists even after the reduction in perfusion pressure has resolved often results in postischemic hyperperfusion, which is... 

Fig. 8.6 Postischemic hyperperfusion. The patient is a 77-year-old man who is status post successful dissolution of an embolus that had occluded the supracbnoid left internal carotid artery and proximal left anterior and middle cerebral arteries, by a combination of intravenous and intra-arterial injection of thrombolytic drugs, and mechanical clot disruption. The DWI image shows a large infarct in the left middle cerebral artery (MCA) territory.

Table 8.2 highlights some of the difficulties entailed in using PWl to identify the ischemic core and penumbra. One such difficulty is the use of PWl in delineating the infarct core. It has been suggested that the quantitative analysis of CBF maps could be used to identify the core, because only blood flow below a certain level would be expected to result in infarction. However, this cannot be done reliably for several reasons. First, non-viable core tissue may exhibit postischemic hyperperfusion, in which case, obviously, no threshold of hypoperfusion would identify the tissue as part of the core. Second, perfusion imaging techniques that rely on... 

Marchal G, Young AR, Baron JC. Early postischemic hyperperfusion Pathophysiologic insights from positron emission tomography. J Cereb Blood Flow Metab. 1999 19 467-482... 

Fig. 8.7 Nondeconvolution-based perfusion measurements in various hemodynamic conditions. Typical concentration-vs.-time curves are shown illustrating (U) underperfused brain tissue, (C) perfusion via collateral pathways resulting in preserved blood flow but delayed bolus arrival, and (H) postischemic hyperemia. A normal curve is presented for comparison (N). Bolus arrival time (Tmax) is late for collaterally perfused tissue, and is typically late for underperfused tissue, but is often early for hyperperfused tissue. TTP is late for underperfused and collaterally perfused tissue, and is often early for hyperperfused tissue...

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