A vasospasm is a spasm of the blood vessels which leads to restricted to blood flow. It can lead to ischemia and, in extreme cases, necrosis. It is a common post-surgical complication and can lead to stroke. It is also the usual mechanism of death when a cerebral aneurysm starts bleeding. It is also often caused by atherosclerosis which can lead to a heart attack.
Treatment is with vasodilators, particularly nitroglycerine due to its fast acting effect. However, these can lead to low blood pressure, tachycardia, headache and palpitations. Calcium channel blockers are used for ongoing care, as are blood thinners, particularly aspirin.