Ischemic penumbra refers to a rim of tissue lying just outside the core ischemic region (area most severely damaged by stroke or ischemic event). Within the core ischemic region, blood and oxygen flow is severely diminished, resulting in neuronal death. However, in the ischemic penumbra, cells are viable for a short amount of time. The penumbra receives its limited blood flow from the collateral arteries of the occluded vascular tree. Studies examining how long penumbral tissue remains viable have reported anywhere from 6 h to 3 days. However, it has been shown that once the subacute phase of the stroke sets in (6–11 days), the untreated penumbral area will succumb to necrosis (cell death). This is due to the fact that the demand for oxygen is too great for the occluded vascular tree to supply.
The absence of unequivocal signs of tissue death in the ischemic penumbra makes it a target for acute pharmacologic intervention following stroke.
References and Readings
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