Stroke

What is a stroke?
A stroke, also called a "brain attack," happens when brain cells die because of inadequate blood flow. A stroke is considered to be a cardiovascular disease and a neurological disorder.

What causes a stroke/brain attack?
Most strokes are caused by the blockage of an artery in the neck or brain, and the rest by bleeding into or around the brain. When brain cells die, function of the body parts they control becomes damaged or destroyed. This may include paralysis, speech problems, memory and reasoning deficits, coma, and possibly death.

What happens during a stroke?
According to the American Heart Association:

A brain attack occurs when a blood vessel bringing oxygen and nutrients to the brain bursts or is clogged by a blood clot or some other particle.

When the brain doesn't get the needed blood flow, because of a rupture or blockage, it is deprived of oxygen. Thus, nerve cells cannot properly function and die within minutes.

And when nerve cells cannot function, the part of the body controlled by these cells cannot function either. The devastating effects of stroke are often permanent because dead brain cells are not replaced.

What are the types of strokes?
There are four main types of stroke:

1. Cerebral thrombosis - caused by blood clots
   
   
2. Cerebral embolism - caused by blood clots
   
   
3. Cerebral hemorrhages - caused by hemorrhages
   
   
4. Subarachnoid hemorrhages - caused by hemorrhages

Cerebral thrombosis and cerebral embolism:

• the most common types of brain attacks
• account for about 70-80 percent of all strokes
• are caused by clots that plug an artery

cerebral thrombosis

• the most common type of brain attack
  
  
• occurs when a blood clot (thrombus) forms and blocks blood flow in an artery bringing blood to part of the brain. Blood clots usually form in arteries damaged by atherosclerosis
  
  
• most often, cerebral thrombotic strokes occur at night or first thing in the morning when blood pressure is low
  
  
• this type of stroke is often preceded by a transient ischemic attack (TIA) or "mini-stroke"

cerebral embolism:

• occurs when a wandering clot (embolus) or some other particle forms in a blood vessel away from the brain -- usually in the heart
  
  
• the clot is carried by the bloodstream until it lodges in an artery leading to the brain or in it, blocking the flow of blood
  
  

• the most common cause is blood clots that form during atrial fibrillation, a disorder in which the two small upper chambers of the heart (the atria) quiver instead of beating effectively. Blood is not pumped completely out of them when the heart beats, allowing it to pool and clot. About 15 percent of strokes occur in people with atrial fibrillation

Cerebral hemorrhages and subarachnoid hemorrhages:

• caused by ruptured blood vessels
• have a much higher fatality rate than strokes caused by clots

cerebral hemorrhages:

• occurs when a defective artery in the brain bursts, flooding the surrounding tissue with blood

subarachnoid hemorrhages:

• occurs when a blood vessel on the surface of the brain ruptures and bleeds into the space between the brain and the skull (but not into the brain itself)