Types of Strokes

When the brain is deprived of its blood supply, a stroke occurs. The brain can be deprived of its blood supply in two major ways: a blood vessel is blocked, or the blood vessel in the brain bleeds or leaks. Any type of stroke is a medical emergency.

Blockages

• An ischemic stroke occurs when the blockage occurs within the blood vessel. The arteries that carry blood to the brain are similar to the branches of a tree. There are main arteries and these main arteries subdivide and subdivide into smaller and smaller branches. In an ischemic stroke, a blood clot travels through the arteries until it reaches a branch of an artery that is too small to allow it to pass through. The clot lodges itself and blocks the supply of blood to the area of the brain that is served by this artery. As a result, neurons or brain cells, in this area die. According to the American Stroke Association, about 83% of all strokes are due to a blockage. A blood clot can block the blood supply in two ways:
• Embolus is a blood clot that forms somewhere else in the body, breaks off, travels through the arteries until it reaches the small arteries in the brain, and causes a blockage.
• Thrombus is a blood clot that builds up on the wall of the blood vessel until it becomes so large that it blocks blood circulation.
  
  
  • Transient Ischemic Attack (TIA) is often referred to as a "mini-stroke". Symptoms of a stroke occur in a TIA but they pass very quickly. People who suffer a TIA return to normal. TIAs are considered as warnings that the conditions indicative of a major stroke are present.

Bleeds or Leaks

• A hemorrhagic stroke occurs when blood escapes from the artery and flows into the surrounding area of the brain. The blood flows into the space between the brain and the skull and increases the pressure on the brain. Blood is toxic to brain cells. When blood comes in contact with brain cells, they die. Seventeen percent of all strokes are hemorrhagic.
• Aneurysms are abnormal widening or ballooning of a portion of an artery, related to weakness in the wall of the blood vessel. Sometimes aneurysms can be present at birth but go undetected. Aneurysms may rupture, if the aneurysm is in a blood vessel on or near the brain, the bleeding may cause a stroke.
• Arteriovenous malformation, often called AVM is a rare type of bleeding stroke. Infrequently, people are born with an abnormal configuration of their arteries. This defect causes pressure to build up in the arteries and eventually, they break and bleed. Only about 2% of strokes are caused by an AVM, but it is the most common type of stroke for young people.