Causes of Stroke

Causes of stroke are a blockage of an artery of the brain by a clot, leading to deprivation of blood and oxygen.

There are two main types of stroke.

• Ischemic stroke is caused by blockage of a blood vessel;
• Hemorrhagic stroke is caused by bleeding.

Bleeding strokes have a much higher death rate than strokes caused by clots.

Ischemic stroke (caused by blocked artery)

Ischemic stroke is the most common type, occurring more than five times as often as hemorrhagic stroke. It occurs when a blood clot forms and blocks blood flow in an artery that brings blood to part of the brain. Typically, a clot forms in a small blood vessel within the brain that has been previously narrowed due to a variety of risk factors including high blood pressure, high cholesterol, diabetes, and smoking.

There are two causes of stroke:

• Embolic stroke: In an embolic stroke, a blood clot or a piece of atherosclerotic plaque (cholesterol and calcium deposits on the wall of the inside of the heart or artery) breaks loose, travels through open arteries, and lodges in an artery of the brain. When this happens, the flow of oxygen-rich blood to the brain is blocked and a stroke occurs.
  
• Thrombotic stroke: As the blood flows through the arteries, it may leave behind cholesterol-laden 'plaques' that stick to the inner wall of the artery. Over time, these plaques can increase in size and narrow or block the artery and stop blood getting through. In the case of stroke, the plaques most often affect the major arteries in the neck taking blood to the brain.

more information on ischemic stroke

Hemorrhagic stroke (caused by bleed in the brain)

Hemorrhagic causes of strokes are a breakage or blowout a blood vessel in the brain . This causes blood to leak into the brain, again stopping the delivery of oxygen and nutrients. Hemorrhagic stroke can be caused by a number of disorders which affect the blood vessels, including long-standing high blood pressure and cerebral aneurysms.

Aneurysms are blood-filled pouches that balloon out from weak spots in the artery wall.  The weak spots that cause aneurysms are usually present at birth. Aneurysms develop over a number of years and usually don't cause detectable problems until they break.

There are two types of hemorrhagic stroke: subarachnoid and intracerebral. These two terms refer to areas of the brain where the stroke has occurred. In a subarachnoid hemorrhage, bleeding occurs under the thin, delicate membrane surrounding the brain.

• Subarachnoid hemorrhage usually causes a sudden, severe headache and stiff neck. If not recognized and treated, major neurological consequences, such as coma, and brain death will occur.

• In an intracerebral hemorrhage, bleeding occurs within the brain itself. High blood pressure is the primary cause of this type of hemorrhage.

more information on hemorrhagic stroke

Vasculitis

Another rare cause of stroke is vasculitis, a condition in which the blood vessels become inflamed.

Migraine headache

There appears to be a very slight increased occurrence of stroke in people with migraine headache. The mechanism for migraine or vascular headaches includes narrowing of the brain blood vessels and this may be a cause of stroke.

Some migraine headache episodes can even mimic stroke with loss of function of one side of the body or vision or speech problems. Usually, the symptoms resolve as the headache resolves.