Physiology and pathology of cerebral ischemia.

In this article the pathophysiology of cerebral ischemia is reviewed. The c oncept of penumbra is explained, and a distinction is made between ischemic necrosis, which occurs in the severely ischemic regions and is associated with loss of calcium and glutamate homeostasis, and programmed cell death, or apoptosis, which is more likely to occur in the moderately ischemic regi ons, evolves more slowly and depends on the activation of a sequence of gen es. Despite this knowledge, it is pointed out that currently only a small p ercentage of stroke patients can access therapies. Some thoughts are provid ed on future research directions and therapies.