What is a Stroke?

A stroke is an event that happens within the brain that causes the it to not receive the blood flow (and oxygen) that it needs.

It can happen to anyone at any time. It occurs when blood flow to an area of brain is cut off. When this happens, brain cells are deprived of oxygen and begin to die. When brain cells die during a stroke, abilities controlled by that area of the brain such as memory and muscle control are lost.
— National Stroke Association

There are two general types of strokes that a person can experience to cause this to occur:  ischemic or hemorrhagic strokes. In either event, this is a medical emergency that must be immediately addressed.  If you are at home, call 911.  If you are in the hospital, be sure to alert the provider immediately.

Ischemic Stroke

Illustration of an ischemic stroke.

Illustration of an ischemic stroke.

Ischemia is the term for what happens when a part of the body does not receive enough oxygen and begins to die. An ischemic stroke occurs when a vessel in the brain gets blocked by a clot or plaque.  When this happens, the portion of the brain that the vessel delivers blood and oxygen to begins to die.  There are two main methods by which this clot happens:

Embolic: Usually this plaque or clot forms in a different part of the body and then travels to the brain.  About 15% of strokes occur in individuals who have atrial fibrillation.

Thrombotic: This type of stroke occurs when a clot forms within one of the arteries giving blood to the brain.  This can be caused by high cholesterol levels and atherosclerosis. 

If you know when a patient started experiencing the stroke symptoms, they may be a candidate for alteplase (TPA).  This is a very potent medication that breaks up clots.  It must be delivered within three hours of onset of symptoms.  It does come with the risk of the stroke converting into a hemorrhagic stroke due to the potent nature of the medication.

Complications related to intravenous r-tPA include symptomatic intracranial hemorrhage, major systemic hemorrhage, and angioedema in approximately 6%, 2%, and 5% of patients, respectively.
— Miller et al.

Hemorrhagic Stroke

Illustration of a hemorrhagic stroke.

Illustration of a hemorrhagic stroke.

A hemorrhagic stroke occurs when a weakened vessel in the brain ruptures and bleeds into the surrounding brain tissue.  The blood continues to flow out of the ruptured vessel which creates increased pressure on the brain.  The two different types of weakened blood vessels that usually cause stroke are arteriovenous malformations and aneurysms.  

  • Arteriovenous Malformation (AVM): An AVM is an clustering of abnormally formed blood vessels that are weakened and prone to rupture. The arteries and veins are connected in this area without capillary beds connecting them.
  • Aneurysm: An aneurysm is the point in a blood vessel where there is weak vessel wall which results in the ballooning out or stretching of the blood vessel. 

Hemorrhagic strokes account for about 13% of all stroke cases.  It is essential that individuals who are experiencing a hemorrhagic stroke get to the emergency room immediately for medical and/or surgical interventions.  

Immediate emergency care is crucial for a hemorrhagic stroke. This treatment focuses on controlling the bleeding in your brain and reducing the pressure caused by the bleeding.
— Healthline

Surgical interventions may be necessary to repair the broken blood vessel and stop the bleeding.  AVMs can sometimes be removed as a surgical intervention.   Hemorrhagic strokes are not always operable and can cause life lasting deficits.

References

National Stroke Association

Miller et al. (2011). Safety of Thrombolysis in Acute Ischemic Stroke: A Review of Complications, Risk Factors, and Newer Technologies

American Stroke Association

Healthline

Posted
AuthorCourtney Tracy