Introduction to Stroke Rehabilitation

Types of Stroke

There are basically 2 types of stroke, hemorrhagic stroke and ischemic stroke:

Hemorrhagic Stroke

A hemorrhagic stroke is caused by a rupture of a blood vessel and may result in:

• Subarachnoid hemorrhage, in which the blood vessel that bursts (usually due to an outpouching or aneurysm in the wall of the blood vessel) is on the brain surface and the blood hemorrhages into the space between the skull and the brain. Subarachnoid hemorrhage can cause a sudden, intense headache with neck pain, nausea, or vomiting, which may be followed by a rapid loss of consciousness or death.
• Cerebral hemorrhage in which the blood vessel that bursts is deep in the brain and the blood hemorrhages into nearby brain tissue.

Both types of hemorrhage cause compression of brain tissue resulting in injury. The extent of compression and the amount of bleeding determine the severity of the stroke. If the hemorrhage occurs in the brainstem, it could lead to a coma or death. Many people die from hemorrhagic stroke, however, those who recover may not suffer long term damage since, when the compression eases, brain function may return. Hemorrhagic stroke accounts for 15-20% of strokes and carries a high risk of death. This type of stroke is associated with hypertension (high blood pressure), malformation of the vascular system, or disorders of blood clotting. Hemorrhagic strokes may occur at any age; the average age at occurrence is typically lower than that of ischemic stroke. Approximately 37% of patients who suffer a hemorrhagic stroke do not survive longer than 30 days.

Ischemic Stroke

Ischemic stroke accounts for approximately 85% of all strokes and is caused either by a cerebral thrombosis or cerebral embolism.

• Cerebral thrombosis - a blood clot forms in an artery in the brain which has already been injured (typically by atherosclerosis, a fatty buildup in the walls of the artery). The interruption of the smooth flow of blood can cause a blood clot to form which then travels through the blood vessels until it blocks the flow of blood in an artery. The blockage causes cell death or injury to the surrounding brain tissue by depriving it of oxygen. According to the American Heart Association, this is the most common etiology of stroke. Cerebral thrombosis is often preceded by a TIA and tends to occur at night or early in the morning when blood pressure is low. Approximately 8-12% of patients who suffer an ischemic stroke do not survive longer than 30 days.
• Cerebral embolism - a blood clot that forms in another part of the body, such as the heart or leg, is carried by the circulating blood until it finally lodges in an artery in the brain. The nerve cells are in that area of the brain are deprived of oxygen causing them to lose function and die within minutes. This type of clot is most typically caused by atrial fibrillation (a rhythm disorder in the atrial chamber of the heart).

Ischemic stroke tends to occur in older people above the age of 60 and the risk increases with older age. Approximately 75% of all ischemic strokes occur in people over the age of 65. It affects African-Americans more than whites; when compared with whites, young African-Americans have a 2-3 fold greater risk of experiencing an ischemic stroke. Ischemic stroke is more common in men until the age of 55, when the distribution equals between men and women.