|A scanning electron micrograph of a blood clot. Image credit: Steve Gschmeissner/Science Photo Library (http://www.sciencephoto.com/media/203271/enlarge#)|
On Monday January 1st, I overheard my dad telling my mom how his left arm was numb and that he had no strength in his left hand. I immediately ran into the medicine cabinet, grabbed two aspirin, practically shoved them down my dad’s throat, and told him to get his coat. He was going to the ER.
As it turns out, my dad was having a stroke, which is basically the cessation of blood flow to an area in the brain. Luckily, my dad only suffered a very mild stroke, and after several days of monitoring and a battery of tests, he was released from the hospital.
While we are all relieved that he dodged what could have been a fatal bullet, I came to realize that there was only a superficial understanding of what was actually happening. So, to help demystify the process for my dad (and anyone else in this situation), I’ve decided to write a mini-guide on strokes. Below you will find some handy information about strokes, including what they are, as well as a glossary of relevant terms.
Why we need blood flow in the brain
Before I get into what happens to the brain when a stroke occurs, it is important to first understand why unrestricted blood flow in blood vessels in the brain is important. The brain is a type of tissue, and like all tissues in our body, it needs a constant access to nutrients and oxygen. Furthermore, tissues produce waste, and this waste needs to be removed.
|The human cardiovascular system. Image Credit: Wikipedia.|
Evolution’s solution to this problem is the development of a vast network of blood vessels existing within our tissues. For instance, take a good look at your very own eyeballs. Especially when we are tired, we can see tiny blood vessels called capillaries, which help to deliver key nutrients and oxygen, keeping our organs of sight healthy and happy. Now consider that this type of blood vessel network exists in all tissues in our bodies (because it does). Depending on the needs of the tissue, these vessels vary in size and number. Sometimes the blood vessels are large, like the aorta, and sometimes they are super tiny, like the capillaries in our eyes. However, all serve the same function: to make sure that cells can breath, eat, and get rid of waste.
When blood is prevented from traveling to a specific area within a tissue, the cells in that area will not get enough fuel and oxygen and will begin to die. For instance, the restriction of blood flow to the heart leads to the death of heart tissue, causing a heart attack. Similarly, the interruption of normal blood flow within the brain causes the affected cells in the brain to essentially starve, suffocate, and die, resulting in a stroke. The medical term for a lack of oxygen delivery to tissues due to a restriction in blood flow is ischemia. In general, the heart, brain, and the kidneys are the most sensitive to ischemic events, which, when occurring in these organs, can be fatal.
So, what exactly is a stroke?
Some strokes can be categorized as being ischemic. As mentioned above, an ischemic stroke occurs when blood flow (and the associated oxygen supply) is restricted in an area within the brain, leading to tissue death. A major cause of ischemic strokes is a progressive disease called atherosclerosis, which can be translated to mean “the hardening of the arteries.”
|Severe atherosclerosis of the aorta. |
Image Credit: Wikipedia.
Affecting the entire cardiovascular system, atherosclerosis is the result of cholesterol build-up inside of our blood vessels, causing their openings to become narrower. These cholesterol plaques can eventually burst, leading to the formation of a blood clot. Ischemic strokes occur as a result of a blood clot, medically known as a thrombus, that blocks the flow of blood to the brain, a phenomenon often related to complications from atherosclerosis. A ruptured cholesterol plaque and resulting blood clot can occur in the brain, or it can occur elsewhere in the body, such as in the carotid arteries, and then travel to the brain. Either way, the blood clot will block blood flow and oxygen delivery to sensitive brain tissue and cause a stroke.
Strokes that result from the bursting of a blood vessel in the brain can be categorized as being hemorrhagic. In this situation, there may be a pre-existing condition rendering the blood vessels in the brain defective, causing them to become weak and more susceptible to bursting. More often than not, a hemorrhagic stroke is the result of high blood pressure, which puts an awful lot of stress on the blood vessels. Hemorrhagic strokes are less common than ischemic strokes, but still just as serious.
How do you know if you’ve had a stroke?
The symptoms of a stroke can vary depending on which part of the brain is affected and can develop quite suddenly. It is common to experience a moderate to severe headache, especially if you are hemorrhaging (bleeding) in the brain. Other symptoms can include dizziness, a change in senses (hearing, seeing, tasting), muscle tingling and/or weakness, trouble communicating, and/or memory loss. If you are experiencing any of these warning signs, it is important to get to the hospital right away. This is especially important if the stroke is being caused by a blood clot since clot-busting medications are only effective within the first few hours hours of clot formation.
Once in the hospital, the caregiver will likely give anyone suspected of having a stroke a CT scan. From this test, doctors will be able to determine if you had a stroke, what type of stroke you had (ischemic versus hemorrhagic), or if there is some other issue. However, as was the case with my dad, a CT scan may not show evidence for a stroke. This issue can arise as a result of timing (test performed before brain injury set in) or size of affected area (too small to see). When not in an emergency situation, doctors may also or instead choose to prescribe an MRI test to look for evidence of a stroke.
If a stroke has been confirmed, the next steps will be to try and figure out the underlying cause. For ischemic strokes, it is important to find out if there is a blood clot and where it originated. Because my dad had an ischemic stroke, he had to undergo a series of tests that searched for a blood clot in his carotid arteries though ultrasound, as well as in the heart, using both an electrocardiogram (EKG) and an echocardiogram (ultrasound of the heart). The patient might also be asked to wear a Holter Monitor, which is a device worn for at least 24 hours and can detect potential heart abnormalities that may not be obvious from short-term observations, like those obtained via an EKG. If a stroke is due to a hemorrhagic event, an angiogram would be performed to try an pinpoint the compromised blood vessel.
A stroke you did have. Now what?
Once a stroke has been confirmed and categorized, the patient will most likely be transferred to the stroke unit of the hospital for both treatment and further observation. If a clot has been detected, a patient will receive clot-busting medications (assuming this detection occurs within several hours of clot formation). Alternatively, a clot can be mechanically removed with surgery (animation of clot removal, also known as a thrombectomy). Patients might also be given blood-thinning medications to either ensure that clots do not increase in size or to prevent new clots from forming. As for secondary prevention, meaning preventing another stroke from happening, patients might be given blood pressure and cholesterol lowering medications.
If a disability arises due to stroke, a patient might need to undergo rehabilitation. The type and duration of stroke rehabilitation is dependent on the area of brain that was affected, as well as the severity of the injury.
Major risk factors and predictors of stroke
There are many situations that could predispose one to having a stroke, and many of these conditions are treatable. The absolute greatest predictor of a stroke is blood pressure. High blood pressure, also known as hypertension, will significantly raise your risk of having a stroke. Other modifiable stroke risk factors include blood cholesterol levels, smoking, type 2 diabetes, diet, alcohol/drug use, and a sedentary life style. However, there are also risk factors that you cannot change including family history of stroke, age, race, and gender. But that shouldn’t stop one from practicing a healthy lifestyle!
In conclusion, strokes are no joke. I am glad that my dad is still here (yes, dad, if you are reading this, we are in fact friends) and that he escaped with relatively no real consequences. Let’s just not do this again, ok?
Anti-coagulants: These are medications that help to reduce the incidence of blood clotting. The repertoire includes aspirin, Plavix, Warfarin, and Coumadin. Also called blood thinners.
Atherosclerosis: Literally translated as “hardening of the arteries,” this condition is hallmarked by the build-up of cholesterol inside of blood vessels. Atherosclerosis can lead to many complications including heart disease and stroke.
Atherosclerotic Plaque: The build of fatty materials, cholesterol, various cell types, and calcium.
Cardiovascular System: The network of blood vessels and heart that works to distribute blood throughout the body.
Carotid Arteries: Arteries that carry blood away from the heart toward the head, neck, and brain.
CT Scan: Cross sectional pictures of the brain using X-rays.
Echocardiogram: An ultrasound of the heart. In stroke vicitms, electrocardiography is used to detect the presence of a blood clot in the heart.
Electrocardiogram (EKG or ECG): The measurement of the electrical activity of the heart. It is performed by attaching electrodes to a patient at numerous locations on the body, which function to measure electrical output of the heart.
Embolic Stroke: A type of ischemic stroke, an embolic stroke occurs when a blood clot forms (usually in the heart) and then travels to the brain, blocking blood flow and oxygen delivery to brain tissue.
Hemorrhagic Stroke: A type of stroke that results form the bursting of a blood vessel in the brain.
Hypertension: High blood pressure, defined as having 140/90 mmHg or above.
Ischemic Stroke: The restriction of blood flow to an area within the brain.
Magnetic Resonance Imaging (MRI): An imaging technique employing a magnetic field that can contrast different soft tissues in the body.
Thrombolytic Medications: Medications that are approved to dissolve blood clots. Also called “clot-busting” medications.
Thrombus: Blood clot.