Vasospasm occurs when a brain blood vessel narrows, blocking blood flow. It can occur in the two weeks following a subarachnoid hemorrhage or brain aneurysm. You are at greater risk for a cerebral vasospasm if you have had a recent subarachnoid hemorrhage or ruptured brain aneurysm.

Why does vasospasm occur after SAH?

Vasospasm is a common complication that may occur 5 to 10 days after SAH (Fig. 2). Irritating blood byproducts cause the walls of an artery to contract and spasm. Vasospasm narrows the inside diameter (lumen) of the artery and thereby reduces blood flow to that region of the brain, causing a secondary stroke.

Why does vasospasm occur in hypertension?

Vasoconstriction and blood pressure

Vasoconstriction reduces the volume or space inside affected blood vessels. When blood vessel volume is lowered, blood flow is also reduced. At the same time, the resistance or force of blood flow is raised. This causes higher blood pressure.