After heart disease and cancer, stroke is the third leading cause of death and disability in the United States. A stroke or cerebrovascular accident (CVA) occurs when a blood vessel in or around the brain either bursts or becomes blocked. The term stroke, therefore, includes hemorrhagic (bleeding) stroke and ischemic (blood vessel blockage) stroke.
Ischemic stroke usually results from either a thrombus or an embolus. A thrombotic stroke or cerebral thrombosis occurs when a brain artery becomes blocked by a blood clot developing directly in the brain artery. Such clots usually develop at sites of arteriosclerosis (“hardening of the arteries”). In embolic stroke or cerebral embolism, a blood clot develops in another artery, or even the heart, and travels to the brain where it becomes lodged in a brain artery and prevents continued blood flow. In either case, oxygen rich blood is prevented from reaching areas of brain beyond the blockage. When deprived of oxygen, the brain tissue quickly begins to die resulting in a stroke or cerebral infarction.
A hemorrhagic stroke results when a cerebral blood vessel bursts. Subarachnoid hemorrhage and intracerebral hemorrhage are types of hemorrhagic stroke. A subarachnoid hemorrhage may be caused by the rupture of a cerebral (brain) aneurysm or an arteriovenous malformation (AVM). Intracerebral hemorrhage can also be caused by aneurysms and AVMs, as well as hypertension and other blood vessel abnormalities.