ABSTRACT
Ischemic stroke results when blood fl ow to the brain is disrupted due to occlusion of the cerebral vessels or cessation of cerebral blood fl ow (CBF). Normal CBF is approximately 50 mL/100 g brain tissue/min. Cerebral dysfunction begins to occur with CBF reductions in the range of 16 to 20 mL/100 g/min. Ionic pump failure and loss of ion homeostasis occurs with reductions to 10 to 12 mL/100 g/min, and cell death results when CBF is < 10 mL/100 g/min ( 1 ). The severity of ischemic injury within the cerebrovascular bed can be classifi ed into 2 broad regions depending on the extent of CBF reduction. The area with the most severe CBF reduction is often referred to as the infarct core because of the rapid necrosis seen within vulnerable neurons. The area around the infarct core is sometimes referred to as the penumbra. “Penumbra” is a term used to describe an intermediate area of marginally perfused tissue that might survive if blood fl ow is restored. The CBF within the penumbra has been estimated to be approximately 12 to 24 mL/100 g/min ( Fig. 1 ) ( 2 ). CBF and severity of ischemic injury are also time dependent; increased occlusion time of the parent vessel results in increased damage. However, cells within the penumbra are potentially salvageable in the presence of appropriate cytoprotective strategies ( 1,3 ).
