What is watershed infarction?

Watershed infarction occurs in the boundary zone between the anterior, middle, and posterior cerebral arteries, which supply blood to the brain. Normally, collateral circulation compensates for the occlusion of one artery by providing blood flow from another artery. However, if there is a critical narrowing of several blood vessels, blood supply to the watershed area may become insufficient when one of the supplying arteries becomes occluded. This can result in a brain infarction in this watershed zone.