Types of stroke

A stroke is the death or damage of brain tissue that occurs when the brain does not get enough blood and oxygen. The result of this is a loss of function usually of an arm or leg or both or a loss of speech or sometimes the loss of balance and co-ordination. Strokes can cause a loss of vision also. The effect of a stroke is usually confined to one side of the body except where the stroke causes a generalized loss of balance (ataxia).

A stroke can be either ischemic or hemorrhagic. In an ischemic stroke, the blood supply to part of the brain is cut off. This can be due to plaque formation, or a blood clot blocking a blood vessel. In a hemorrhagic stroke, a blood vessel bursts. This allows blood to leak into an area of the brain and destroy it. The types of Ischemic stroke are:

• Transient ischemic attack (TIA) is a short-term stroke which lasts for less than 24 hours. The oxygen supply to the brain is restored quickly, and symptoms of the stroke disappear completely. A transient stroke needs prompt medical attention as it is a warning of serious risk of a major stroke.
• Cerebral thrombosis or the formation of a blood clot inside an artery that supplies the brain. Clogging of the arteries, known as atherosclerosis, can cause a stroke due to thrombosis. Stroke may occur from carotid stenosis, a blockage in a main artery in the neck called the carotid artery. Another cause of thrombosis is arteritis, or artery inflammation, in an artery that supplies the brain. This may be due to a condition called temporal arteritis, for example. Trauma or injury to arteries, such as in a condition called carotid dissection, can cause a stroke. Certain blood disorders can also cause thrombosis. Examples include an inherited condition called sickle cell disease that results in abnormal blood cells, or a blood cancer called polycythemia vera.
• Cerebral embolism is a blood clot which forms somewhere in the body before travelling through the blood vessels and lodging in the brain. This causes the brain cells to become starved of oxygen. Blood clots from the heart, which commonly occur with an irregular heartbeat or recent heart attack are another cause. These cases are sometimes referred to as stroke from a cardiogenic embolism. An embolism can also occur when a piece of cholesterol or fat plaque from an artery in the neck breaks off, blocking blood flow and causing a stroke.

Cerebral haemorrhage occurs when a blood vessel bursts inside the brain and bleeds (haemorrhages). With a haemorrhage, extra damage is done to the brain tissue by the blood that seeps into it. A haemorrhagic stroke may be due to an intracerebral haemorrhage where a tiny blood vessel within the brain bursts and bleeds, or due to a subarachnoid haemorrhage where a large bulging in the blood vessel wall (an aneurysm) bursts and causes brisk bleeding underneath the brain covering. Subarachnoid haemorrhage often affects younger people whereas intracerebral haemorrhage is commoner in the elderly.