Acute cerebral ischemia ischemic penumbra

Fig. 4.12. Mismatch concept of diffusion lesion (smaller) and perfusion deficit (larger) in human territorial brain infarction. Acute MCA territory ischemia/oligemia with a smaller, centrally located diffusion disturbance showing the relationship between infarct core, ischemic penumbra and changes in DWI and PI. DWI, diffusion-weighted imaging PI, perfusion imaging ADC, apparent diffusion coefficient ATP, high energy phosphates MCA, middle cerebral artery...

Apoptosis is programed cell death and differs from necrosis in that it results in minimal inflammation and release of genetic material. Although necrosis is the predominant process that follows acute ischemia, apoptosis is important after more minor injury, particularly within the ischemic penumbra. Apoptosis is executed by the production, activation and action of caspases, which are protein-cleaving enzymes that dismantle cytoskeleton proteins and enzymes responsible for cellular repair (Zhang et al. 2004). Neurons are particularly susceptible to caspase-mediated cell death after cerebral ischemia, as demonstrated by the reduction in infarct size by caspase inhibitors in experimental models. 

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