Types of Stroke
What is a stroke?
A stroke occurs when blood stops flowing to a part of the brain and the cells do not get blood and oxygen. Deprived of oxygen, cells in the affected area of the brain can’t work and die within minutes. The devastating effects of a stroke can be permanent because dead brain cells are not replaced.
Ischemic Strokes (Clots)
- Ischemic stroke accounts for about 87% of all cases.
- Ischemic strokes occur as a result of an obstruction within a blood vessel supplying blood to the brain. The underlying condition for this type of obstruction is the development of fatty deposits lining the vessel walls. This condition is called atherosclerosis. These fatty deposits can cause two types of obstruction:
- Cerebral thrombosis refers to a thrombus (blood clot) that develops at the clogged part of the vessel.
- Cerebral embolism refers generally to a blood clot that forms at another location in the circulatory system, usually the heart and large arteries of the upper chest and neck. A portion of the blood clot breaks loose, enters the bloodstream and travels through the brain's blood vessels until it reaches vessels too small to let it pass. A second important cause of embolism is an irregular heartbeat, known as atrial fibrillation. It creates conditions where clots can form in the heart, dislodge and travel to the brain.
- Silent cerebral infarction (SCI), or "silent stroke," is a brain injury likely caused by a blood clot interrupting blood flow in the brain. It's a risk factor for future strokes that could lead to progressive brain damage due to these strokes.
Hemorrhagic Strokes (Bleeds)
- Hemorrhagic stroke accounts for about 13% of stroke cases.
- It results from a weakened vessel that ruptures and bleeds into the surrounding brain. The blood accumulates and compresses the surrounding brain tissue. The two types of hemorrhagic strokes are intracerebral (within the brain) hemorrhage or subarachnoid hemorrhage.
- Hemorrhagic stroke occurs when a weakened blood vessel ruptures. Two types of weakened blood vessels usually cause hemorrhagic stroke: aneurysms and arteriovenous malformations (AVMs).
- An aneurysm is a ballooning of a weakened region of a blood vessel. If left untreated, the aneurysm continues to weaken until it ruptures and bleeds into the brain.
- An arteriovenous malformation (AVM) is a cluster of abnormally formed blood vessels. Any one of these vessels can rupture, also causing bleeding into the brain.
TIA (Transient Ischemic Attack)
- While transient ischemic attack (TIA) is often labeled "mini-stroke," it is more accurately characterized as a "warning stroke," a warning you should take very seriously.
- TIA is caused by a clot; the only difference between a stroke and TIA is that with TIA the blockage is transient (temporary). TIA symptoms occur rapidly and last a relatively short time. Most TIAs last less than five minutes; the average is about a minute. When a TIA is over, it usually causes no permanent injury to the brain.
- Why do some clots dissolve while others don’t?
- The body has naturally occurring clot-busting agents. Whether there is damage depends on how long the clot is in place; because there is no way to predict when a clot will dissolve on its own, time is of the essence.
- While the vast majority of strokes are not preceded by TIA, about a third of people who experience TIA go on to have a stroke within a year. TIA is a warning stroke and gives a patient time to act and keep a permanent stroke from occurring.
- If a survivor experiences TIA after they have had a stroke, he or she should go to the emergency room immediately because something in his or her treatment plan has not worked.
- In essence, there should be no difference in response to a TIA or a stroke. Although a TIA resolves itself before there is damage, there is no way to predict which clots will dissolve on their own. Stroke — and TIA — are medical emergencies; dial 911 and tell the operator you think it's a stroke and note the time the symptoms started. Remember: Time lost is brain lost.
