Background on Strokes

Stroke: What it is, what causes it, how is it treated?

While strokes are a commonly known medical condition, many people may not be familiar with the causes, signs, and symptoms of a stroke. In order to spread awareness about the risk for and treatment of strokes, this article will answer a series of common questions about strokes including what a stroke is, what causes a stroke, and how to treat a stroke.

How common are strokes? 

Strokes are the fifth highest cause of death in the United States. They are also a huge contributor to adult disability. Roughly 800,000 Americans suffer from a stroke every year, and one American is killed by a stroke about every 4 minutes (Centers for Disease Control and Prevention, 2015). 

What is a stroke?

A stroke is known medically as a cerebrovascular accident (CVA). It is defined as an extreme reduction or even a total stoppage of the blood flow to the brain, which can cause various, severe, and usually long-term disabilities. The resulting impairments caused by a stroke depend on the portion of the brain which is affected by the loss of blood flow. Strokes are often preceded by transient ischemic attacks or TIAs. A TIA is a momentary deprivation of blood to the brain which often results in a brief loss of sight or a feeling of numbness (Berry, Wilson, & Fallon, 2014).

What causes a stroke?

There are two main causes of strokes. Most strokes, about 85%, are caused by restricted blood flow in the blood vessels of the brain; this type of stroke is known medically as ischemia. Strokes can also be caused by broken blood vessels resulting in blood leaking into the brain; these are known as hemorrhagic strokes (Berry, Wilson, & Fallon, 2014).

Strokes are often caused by a variety of other factors including smoking, high cholesterol levels, hypertension, diabetes, cerebral aneurysm, atherosclerosis, and transient ischemic attacks (TIA). Having a family history of strokes or TIAs also increases your risk of stroke (Berry, Wilson, & Fallon, 2014).

Hypertension is more commonly known as high blood pressure. This pre-existing medical condition can increase your risk for stroke. Hypertension can cause hemorrhagic strokes, which are brought on by bleeding in the brain (Berry, Wilson, & Fallon, 2014).

Cerebral aneurysms also cause hemorrhagic strokes. A cerebral aneurysm is when an artery weakens and enlarges causing it to rupture, which results in a hemorrhage within the brain. Tumors and genetic blood conditions may also contribute to hemorrhagic strokes (Berry, Wilson, & Fallon, 2014). 

Atherosclerosis is a disease which affects the arteries. If you have atherosclerosis disease in other parts of the body, such as the heart or legs, you may also have an increased risk of developing the disease in the arteries of the brain, which can affect the circulation of blood in the brain. The disease causes calcium, cholesterol, and fat to build up on the walls of the arteries. These substances eventually form into plaques which cause a narrowing or even complete closure of the artery. Plaque buildup caused by atherosclerosis can also cause blood clots which may block arteries and result in a stroke (Berry, Wilson, & Fallon, 2014).

Transient ischemic attacks (TIAs) are also known as mini-strokes. TIAs may precede a stroke. TIAs have similar symptoms to strokes, but they do not result in long-term damage like strokes do. TIAs usually last just a matter of minutes, and most last less than a day. TIAs are caused by emboli. An embolus happens when plaque buildup in a major artery breaks off and then stems blood flow to an area of the brain. When symptoms of a TIA last for longer than a day, a stroke has occurred (Berry, Wilson, & Fallon, 2014).

What are the warning signs and symptoms of a stroke?

The signs and symptoms of a stroke are dependent upon the portion of the brain which has lost blood flow. A major stroke occurring on one side of the brain usually impedes the movements and muscle control on the opposite side of the body. Hemiparesis, which is the loss of feeling or use of one side of the body, and hemiplegia, which is a sudden weakness of an arm or leg, are both possible signs of this occurrence. Aphasia, which is the loss of speech, or dysarthria, which is trouble speaking, may also occur. Changes in vision may also be symptoms of a stroke. Amaurosis fugax is the loss of vision in a single eye. Less commonly, a stroke may affect the same part of the visual field in both eyes. All of these symptoms are caused by a lack of blood in the carotid arteries located in the frontal portion of the brain. Other general warning signs of stroke may include dizziness and disorientation, which are caused by the lack of blood flow to the base of the brain. About 20% of people who have a stroke have no symptoms or warning signs, and these individuals may even remain unaware they have experienced a stroke (Berry, Wilson, & Fallon, 2014).

How is a stroke diagnosed? 

If a patient is suspected of suffering from a stroke, the diagnosis process usually begins with a complete medical history and a physical examination. After taking note of the symptoms and the relevant risk factors, the doctor can deduce the area of the brain most likely affected by the stroke. This information is then used to determine what further testing and therapy is appropriate (Berry, Wilson, & Fallon, 2014).

One older method of testing is the directional Doppler test. This is a noninvasive method which utilizes a Doppler device to send an ultrasonic signal through the brain. The flow of blood will cause a shift in the frequency sent back. This shift is then used to determine the speed and direction of blood flow. Duplex ultrasound machines were developed in the 1980s and utilized brightness-mode ultrasound to visualize blood vessels and plaque. Due to diagnostic limitations these methods are not commonly used today (Berry, Wilson, & Fallon, 2014).

An ocular pneumoplethysmograph (OPG) is another noninvasive method for diagnosing strokes. The OPG measures eye pressure through cups. A vacuum is created, which blocks the arteries. Once the vacuum is released, the arteries regain blood flow and the pulsations of the blood flow are measured to determine the amount of artery blockage. An OPG is not able to take into account blockages which may have occurred in the base of the brain, but despite this limitation, it is still used as a quick and noninvasive diagnostic tool (Berry, Wilson, & Fallon, 2014).

Computed tomography (CT) is one of the most common diagnostic tools used today. CT scanning provides 3D images of the brain using a radiological technique. Magnetic resonance imaging (MRI) is another technique used today to produce 3D images of the brain. MRIs are a non-radiological technique. Both techniques can detect cerebral infarcts (Berry, Wilson, & Fallon, 2014).

An angiography (also known as an arteriography) is conducted by placing a catheter into an artery and injecting an iodine dye. X-rays are then taken to track blood flow. Blockages are then determined and used in the planning of future surgical operations. An angiography is the most common diagnostic test for strokes (Berry, Wilson, & Fallon, 2014).

What is the difference between a stroke and a heart attack?

A stroke is defined as an extreme reduction in or complete stoppage of blood flow to the brain, which results in serious and permanent damage which varies depending on the region of the brain affected by the blood loss (Berry, Wilson, & Fallon, 2014). In comparison, a heart attack is defined as the abrupt failure of the heart’s muscles caused by a reduced flow of blood and oxygen to the muscles (Cannon, 2015). While both are caused by a loss of blood and, therefore, oxygen to a vital organ, the key difference is the location of blood loss with a stroke occurring in the brain and a heart attack affecting the muscles of the heart.

There are also differences in the symptoms experienced. A stroke can cause a wide range of symptoms based on the area of the brain affected. These may include loss of sight, loss of feeling, speech disorders, slack or weak muscles (especially in the face), dizziness, disorientation, and headaches (Berry, Wilson, & Fallon, 2014). Symptoms of a heart attack often include chest pain, sweating, and loss of breath (Cannon, 2015). Both strokes and heart attacks can occur without symptoms (Berry, Wilson, & Fallon, 2014; Cannon, 2015).

How can you prevent a stroke?

The most effective treatments for strokes are preventive changes in behavior to reduce your risk factors. Preventive changes may include decreasing your intake of sodium and saturated fats and increasing your intake of potassium, fruits, and vegetables in your diet in order to lower blood pressure and reduce hypertension. Similar measures also include weight loss and quitting smoking. Individuals at a high-risk level for stroke should discuss taking a low dose aspirin every two days with their doctor (Berry, Wilson, & Fallon, 2014). 

How should a stroke be treated during an emergency? 

A regimen of low-dose aspirin can be used to reduce the symptoms of a stroke. The regular use of aspirin is also recommended as a preventative measure for strokes in individuals who have previously experienced a stroke or a TIA (Berry, Wilson, & Fallon, 2014).

Percutaneous balloon angioplasty requires fitting a balloon catheter into the blocked artery during an angiogram. The balloon catheter is then inflated, which works to open the area and restore blood flow. This method is often used in treating blood clots in other parts of the body, but it is not commonly used in treating blood blockages within the brain due to the possibility the clot will simply move to a different vessel within the brain or eye (Berry, Wilson, & Fallon, 2014).

Drugs which help to dissolve clots can be used in the treatment of artery blockages by themselves or in addition to balloon angioplasty. This method is very successful in treating blood clots in other parts of the body, but these drugs carry additional bleeding complications, which limits their usefulness in effectively treating strokes (Berry, Wilson, & Fallon, 2014).

What are long-term treatments for a stroke?

Surgical revascularization is recommended for individuals with a history of TIAs or strokes. Endarterectomy is the most commonly used surgical procedure for the revascularization of the carotid arteries, but this surgical procedure can be used on other arteries as well. In an endarterectomy procedure, the walls of the carotid artery are scraped to free them from plaques (Berry, Wilson, & Fallon, 2014).

The best long-term treatments for strokes are the practice of preventative measures including aspirin regimens, a low-fat and low-sodium diet, and quitting smoking (Berry, Wilson, & Fallon, 2014).

References:

Berry, S.R., Wilson, B.P., & Fallon, L.M. (2014). Strokes. Magill’s Medical Guide (Online Edition).

Cannon, B.P. (2015). Myocardial Infarction (Heart attack). Magill’s Medical Guide (Online Edition).

Centers for Disease Control and Prevention (2015). Stroke. Retrieved from https://www.cdc.gov/stroke/.