What is the main difference between a thrombotic stroke and an embolic stroke?
Thrombotic and embolic strokes are both types of ischemic strokes, but they differ in their causes and locations of clot formation. A thrombotic stroke occurs when a blood clot (thrombus) forms in an artery that supplies blood to the brain, often due to atherosclerosis. The clot obstructs blood flow, leading to brain injury. Risk factors include high cholesterol, high blood pressure, smoking, diabetes, obesity, and lack of exercise [11].
On the other hand, an embolic stroke happens when a blood clot or other debris (embolus) forms elsewhere in the body and travels through the bloodstream to the brain. The embolus gets lodged in a brain artery, blocking blood flow. The most common source of the clot is the heart, especially in conditions like atrial fibrillation [12].
In terms of treatment, thrombotic strokes are often treated with a clot-busting drug called alteplase, which must be given within 4.5 hours of stroke onset. If the clot is in a large vessel, a procedure called mechanical thrombectomy may be performed within six hours of the stroke [13].
Thrombotic Stroke Symptoms
Thrombotic stroke belongs to the group of ischemic strokes. The symptoms of a thrombotic stroke manifest in different ways depending on the location and severity of the brain damage. Common symptoms of thrombotic stroke independent of the location are headache, dizziness and confusion [1]. In the case of a basal ganglia stroke, symptoms may include Muscle weakness or paralysis difficulty walking, difficulty maintaining balance, and more.
In addition, other symptoms which may occur as a consequence of large vessel thrombosis include weakness or paralysis of your arm, leg and/or face on one side of your body. This can occur suddenly or gradually and it is known as hemiparesis [1]. Further, the patient may experience numbness or loss of sensation.
Some patients may experience more serious symptoms such as losing a part of their vision either in one or in both of their eyes. This then causes problems with balance. Patients may experience problems with walking and standing. When sitting, the balance problem manifests as a difficulty with staying upright.
However, other symptoms such as difficulties finding the right word to say, difficulty speaking clearly and problems with understanding what you hear or read (aphasia) can also occur [1]. Some of these symptoms are also prevalent in Frontotemporal dementia.
In the case of a lacunar stroke, which is typically caused by small vessel thrombosis, symptoms can include weakness or paralysis and loss of sensation, weakness and clumsiness in the arm or leg, and inability to form or pronounce words and clumsy hand movements [1].
Embolic Stroke Symptoms
An embolic stroke occurs as a consequence of a blood clot blocking the blood flow into the brain. The blood clot usually forms elsewhere in the body and then travels into the brain causing the blockage.
The symptoms of the embolic stroke vary from person to person, stroke to stroke and also similarly to the thrombotic stroke it depends on the location. However, some common symptoms include difficulty speaking or understanding words, which manifests as slurred speech or difficulty with finding the right words to use [2]. Further, it includes problems with walking, lack of coordination, stiff muscles, and feelings of weakness on one side or both sides of the body [2].
Another common symptom is feeling numbness in the limbs or one side of the face. This can also manifest as paralysis on one side of the body [2]. Further, the patient may experience mental confusion, visual agnosia and altered levels of consciousness. This means that the patient may be more lethargic than usual [2].
Other symptoms of embolic stroke include blurred vision, blindness, dizziness, feeling faint or having problems with swallowing, nausea and sleepiness [2].
It is important to remember that all of these symptoms usually start suddenly and if you notice any of these symptoms, you need immediate medical attention. Call your healthcare provider or your local emergency department [2].
Causes: Thrombotic Stroke vs Embolic Stroke
Thrombotic Stroke
Thrombotic stroke is usually triggered by inadequate blood flow to a part of the brain due to a blocked artery. Having a blocked artery is a result of a blood clot that worms within the artery known as a thrombus. Thrombus formation is typically made up of a hardened buildup of cholesterol and other substances like fat and this process is known as atherosclerosis [1].
Therefore, it is natural that high cholesterol, high blood pressure, smoking, diabetes, obesity and lack of exercise may increase the risk of developing thrombotic stroke.
In addition to this, age and family history of thrombotic stroke, cancer, hematologic disorders such as platelet dysfunction, prothrombotic coagulopathies and defective fibrinolysis or antiphospholipid antibody syndromes can also increase the risk of thrombotic stroke [1, 3, 4, 5].
In some cases, severe iron deficiency anaemia has been associated with stroke, particularly in young adults [6].
Embolic Stroke
On the other hand, an embolic stroke is caused by a blood clot or other debris which gets formed elsewhere in the body and then travels to the brain. Such a blood clot is called an embolus. Usually, it is formed in your heart and is swept through the bloodstream to narrower brain arteries.
One of the most prevalent causes of embolic stroke is atrial fibrillation, which is a heart rhythm disorder that increases the risk of clots in the heart. These clots then travel to the brain and cause the stroke []. Further non-rheumatoid and rheumatic atrial fibrillation, infective endocarditis, prosthetic heart valves, recent myocardial infarction, dilated cardiomyopathy, intracardiac tumours and rheumatic mitral stenosis may induce the formation of emboli which may lead to an embolic stroke [8].
Similarly to thrombotic stroke, at higher risk for embolic stroke are patients who have high blood pressure, high cholesterol, obesity, smoke, use drugs and lack exercise [2].
Sometimes it is hard to identify the cause of an embolic stroke. An example of such is when an embolic stroke occurs with infective endocarditis and antiphospholipid antibody syndrome simultaneously. In such cases, it is very challenging to determine the origin of the embolic stroke [9].
Treatment: Thrombotic Stroke vs Embolic Stroke
The treatment for thrombotic stroke and embolic stroke revolves around using medications, procedures and rehabilitation. Together these help to dissolve the blood clot and restore the blood flow to the brain.
Standard Treatment
The standard treatment for both of these strokes is alteplase. It is a clot-busting drug, a tissue plasminogen activator, which must be administered via vein within 4.5 hours of stroke onset. It helps break the clot up and open the artery, which ultimately allows blood flow to the brain again [1].
Additional Procedures
In some cases, doctors can inject alteplase directly into the area with the clot by inserting a catheter into the artery in the patient's groin and threading it up to the brain [1].
In addition to this, a procedure called mechanical thrombectomy may be performed after applying alteplase. This procedure must be performed within six hours of the stroke and it involves removing the clot and placing a stent to keep the artery open using a catheter inserted into an artery [1].
Mechanical thrombectomy is usually performed when there is a large vessel thrombosis in a carotid artery (in the neck) or the first part of the middle cerebral artery (in the brain).
Preventive Medication
In case you are at high risk of experiencing thrombotic or embolic stroke, your doctor may prescribe you an antiplatelet medication. This medication reduces the risk of blood clot formation and prevents future strokes. Such medication is for instance aspirin, clopidogrel or a combination of aspirin and dipyridamole [1].
Rehabilitation
Rehabilitation is often prescribed as an after-stroke treatment. It helps with regaining strength and recovering any lost function due to the stroke. Ongoing outpatient care, medication, and close monitoring are typically required for some time after a stroke [2].
Despite these treatments, there is still a need for treatments that improve the efficacy and safety of thrombotic and embolic stroke therapy [10].