Accidente Cerebrovascular
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Types of Stroke

What is a stroke?

Stroke is the 5th leading cause of death in the United States. It is also one of the leading causes of adult disability. More than 600,000 stroke cases are recorded in this country every year [1]. A stroke occurs when blood flow to the brain is cut off to a specific part of the brain by either a blood clot or a blood vessel rupture. Since the brain needs oxygen and nutrients like glucose to survive, the part of the brain that stops receiving blood begins to die. In fact, the cells that make up the brain (also known as neurons) can die within minutes without a constant supply of oxygen. If a stroke event is not treated within several hours after the presentation of symptoms, the part of the brain affected will die and cannot be recovered. There are 5 different types of stroke that will be covered in the following sections.

Ischemic stroke

Ischemic stroke occurs when blood supply to a specific part of the brain is partially or completely blocked by a blood clot. Over 85 percent of all stroke cases are ischemic [2]. The main cause of an ischemic stroke is atherosclerosis, the scientific name for the buildup of cholesterol and other fatty deposits that stick to the walls of blood vessels and mainly come from the food we eat. These fatty deposits increase the risk of having a stroke because if enough of the fatty deposits stick to the blood vessel walls, it can create a thrombus (the scientific name for blood clot) that blocks blood flow through the vessel. And since strokes involve blood vessels that travel to the brain, this blockage that causes a stroke is known as a cerebral thrombosis. These plaques are dangerous because they build up along blood vessel walls without any symptoms, and can suddenly culminate in an ischemic stroke.

Another cause of ischemic stroke is an embolism. An embolism is a blood clot that forms in a blood vessel in another part of your body, such as the heart, and only partially blocks blood flow. Since blood is still flowing in the vessel, the blood clot can become “dislodged” and unstick from the walls of that particular blood vessel. This clot can travel to a smaller blood vessel where it completely blocks blood flow. When that smaller blood vessel supplies a particular part of the brain with blood, it is known as a cerebral embolism [3].

Once symptoms appear, call 911 as soon as possible. These symptoms can be viewed on the symptoms page.

Transient ischemic attack (TIA)

A transient ischemic attack, or TIA, is a special subtype of ischemic stroke and is sometimes called a “mini-stroke.” Even though the body resolves the temporary blood clot on its own, it acts as a major wake up call. There is usually no permanent damage that results from a TIA and although people believe they have nothing to worry about, it must be taken seriously [4]. Even if the symptoms resolve quickly, you should still call 911 immediately. TIAs may suggest that you are at risk of having a real stroke in the future, which can lead to severe neurological complications, disability and death if not treated quickly. The symptoms are exactly the same as those of a real stroke and can be viewed on the stroke signs page.

Hemorrhagic stroke

Hemorrhagic stroke is another type of stroke caused by the rupture of a blood vessel inside of the brain that has weakened over time. It makes up about 13 percent of all stroke cases [5]. Hemorrhagic stroke is labeled by two major factors: what type of weakened blood vessel led to the stroke and the location of the rupture itself.

There are two types of weakened blood vessels that lead to hemorrhagic stroke: aneurysms and arteriovenous malformations (AVMs). Aneurysms refer to blood vessels that slowly get bigger and weaken as a result. If left untreated, they grow until they rupture. Aneurysms can be caused by a number of different risk factors: use of drugs such as cocaine and methamphetamine, bacterial or viral infections, and direct brain trauma [6].

AVMs are more complex and require more background information. There are two main types of blood vessels in our bodies: arteries and veins. Simply put, arteries carry oxygen and other nutrients to the brain and other organs to make sure they function properly while veins carry waste and carbon dioxide back to be expelled from the body. AVMs occur when arteries and veins get tangled and the blood with oxygen and waste, which is normally kept separate, begin to mix so that the brain tissue does not receive the proper nutrients it needs to function. When these blood vessels tangle, they are much more likely to rupture. Less than 1 percent of the population is born with an AVM and it is not hereditary [7].

Once the blood vessel ruptures, the stroke is then categorized by where the bleed is. If the bleed is within the brain, then it is called an intracranial hemorrhage. If the bleed is within the space between the brain and the skull, it is called a subarachnoid hemorrhage. Both of these allow blood to accumulate within the brain and put a lot of pressure on brain tissue.

Cryptogenic stroke

Cryptogenic stroke happens when the cause of stroke cannot be determined, despite running a lot of tests. These are very tough because 1 out of every 4 stroke patients will have another stroke event and it is very hard for doctors to find out how to treat it without knowing the cause of the event [8]. This means that if a cause is not found, the patient is more likely to have another stroke.

The American Stroke Association has wonderful guides and resources that help cryptogenic stroke patients and their loved ones navigate through this difficult time.

Brain stem stroke

Brain stem stroke occurs when blood flow to the area just below the base of the skull known as the brain stem is blocked. The brain stem is an area of the brain responsible for the processes that keep us alive and occur without any effort [9]. A stroke, whether it be hemorrhagic or ischemic, to this particular area can be fatal if the areas that control vital processes such as our heartbeat or breathing die because they did not receive enough oxygen.

References

  1. http://www.ninds.nih.gov
  2. https://www.stroke.org/en/about-stroke/types-of-stroke/ischemic-stroke-clots
  3. Roth E.J. (2011) Cerebral Embolism. In: Kreutzer J.S., DeLuca J., Caplan B. (eds) Encyclopedia of Clinical Neuropsychology. Springer, New York, NY. https://doi.org/10.1007/978-0-387-79948-3_2166
  4. https://www.stroke.org/en/about-stroke/types-of-stroke/tia-transient-ischemic-attack
  5. https://www.stroke.org/en/about-stroke/types-of-stroke/hemorrhagic-strokes-bleeds
  6. https://www.stroke.org/en/about-stroke/types-of-stroke/hemorrhagic-strokes-bleeds/what-you-should-know-about-cerebral-aneurysms
  7. https://medlineplus.gov/arteriovenousmalformations.html
  8. https://www.stroke.org/en/about-stroke/types-of-stroke/cryptogenic-stroke
  9. https://www.upstate.edu/stroke/about_stroke/types-of-stroke/brainstem-stroke.php