Introduction

Stroke is a major global health challenge, it is a leading cause of disability in adults and the second leading cause of death among developing and developed countries. Most strokes are ischemic, accounting for 85% of strokes. Ischemic stroke is a condition where the blood supply to the brain is reduced or blocked, which could be caused by carotid artery disease.¹

Carotid artery disease is when the carotid artery, a blood vessel that supplies amounts of blood to the brain, is narrowed or blocked. Understanding the relationship between both conditions is essential for improving the survival rate through prevention and management.

What is an ischemic stroke?

Ischemic stroke is a major health condition characterised by reduced or blocked blood flow to the brain. In many conditions, they manifest as frequent attacks known as transient ischemic attacks (TIAs), defined as focal ischemic neurologic deficits lasting less than 24 hours and usually less than 30 minutes. TIA are mini-strokes, which can be regarded as your warning signs for the occurrence of a stroke.²

What are the different types of stroke?

There are two types of  Strokes:³

• Ischemic 
• Hemorrhagic

The initial approach in your treatment is focused on finding out whether the stroke is of ischemic or hemorrhagic origin.

Ischemic strokes are classified based on their causes:⁴

• Thrombotic stroke
• Embolic stroke

Thrombotic stroke

Thrombotic strokes are caused mainly due to blockage by a blood clot or plaque (fatty buildup) in your brain, thrombotic strokes are often preceded by TIA. Thrombotic stroke is usually seen in older people, especially if they have high blood pressure, high cholesterol levels, atherosclerosis or diabetes. If a thrombotic stroke occurs in smaller arteries of your brain, it is called a lacunar stroke. In this condition, you will experience mild symptoms as only a small part of your brain was involved in damage.⁴

Embolic stroke

Embolic strokes are caused by moving blood clots (emboli) that are formed elsewhere in your body by platelet accumulation and other cell debris, which then dislodge from the site of formation and travel through the bloodstream to the brain, blocking arteries in your brain. This type usually occurs if you have heart diseases like arrhythmias or atrial fibrillation.⁴

Symptoms of a stroke 

Strokes manifest suddenly, hence, you should know their signs and symptoms. You might experience:³

• Sudden numbness in your face, arm, or leg especially on one side of the body
• A sudden confusion with an inability to speak or understand speech 
• You may not see properly because of loss of vision in one or both of your eyes
• You will have difficulty walking, feel tired, and dizzy, and fall or lose consciousness
• You might experience a severe headache 

There are certain warning signs known as FAST warning signs:⁵

• F - Face drooping
• A - Arm weakness
• S - Speech difficulty
• T - Time to call 999 as stroke is an emergency 

Risk factors associated with stroke 

Health conditions, lifestyle factors and genetics are considered risk factors for stroke.

Non-modifiable factors

• Age: older people and infants below the age of 1, especially babies that are born with low birth weight, are at higher risk of developing a stroke
• Gender: strokes usually occur more in males than in females, making males at higher risk
• Race: race plays a role as well. If you are African American, Asian, or Hispanic, you are at higher risk compared to other races
• Family history and Genetics: your risk for a stroke increases if a family member has a history of stroke. Certain genes, like the one that determines your blood type, can also pose a risk for stroke⁶

Modifiable risk

• Hypertension: puts pressure on the inside walls of your arteries, this pressure can cause damage to arteries, leading to the formation of blood clots which might block your arteries 
• Atrial fibrillation: in this condition, your heart pumps blood irregularly, leading to clot formation
• Coronary artery disease: blood flow to your heart is compromised, leading to clot formation that might move to the brain arteries, causing blockage⁶

Treatment of stroke

Early detection of stroke and taking the right treatment are essential to prevent complications. The treatment options for stroke include:⁴

• Medications: your healthcare consultant will prescribe medications such as tissue plasminogen inhibitors like alteplase and antiplatelet agents like aspirin. These medications will help to dissolve the clot and improve blood circulation in your brain
• Mechanical treatment includes surgical processes like thrombectomy or stenting, which removes clots from the arteries
• Other treatment strategies for secondary prevention of stroke include controlling and preventing complications resulting from other health conditions like atherosclerosis, hypertension, diabetes, atrial fibrillation, etc

Carotid artery disease

Carotid arteries are the blood vessels that supply blood to the brain through the neck. They are present on each side of the neck, and blockage of these vessels can interrupt the blood supply to the brain, resulting in a condition known as carotid artery disease (CAD).

The blockage in these blood vessels is mainly due to cholesterol deposits, which will break down or rupture into small and large clots, leading to blockage or narrowing of blood flow channels, causing disruption or stoppage of blood flow to your brain.⁷

Symptoms of carotid artery disease (CAD)

You may not experience any symptoms as carotid artery disease is usually asymptomatic. Symptoms will show up only when your brain vessels are severely narrowed or blocked. At that stage, you might experience:^7,8

• One or more episodes of TIA 
• You might find it difficult to speak and understand simple statements
• Muscle weakness occurs in your arms and legs 
• You might lose vision completely or partly (side vision), with the feeling of a curtain being drawn over your eyes
• The face might be droopy and numb 

Risk factors of CAD

Atherosclerosis is the primary risk factor that contributes to the accumulation of plaque in your arteries, which may occur due to elevated cholesterol levels, high blood pressure, obesity, or diabetes mellitus. Hence managing your comorbidities is essential to avoid plaque buildup

Other risk factors include gender, smoking, poor diet, not exercising, and having a sedentary lifestyle.⁸

Diagnosis of CAD

Early diagnosis of the carotid artery blockage is essential to understand the severity of your disease and to provide treatment as early as possible

• Carotid ultrasound: it is a cost-effective procedure that helps in finding out atherosclerosis.  also determines the  speed and direction of the blood flow in  your artery, which provides an idea regarding the presence of plaque
• Transcranial Doppler (TCD): this method is used to check blood circulation in your  arteries, which facilitates  the blood flow to your  eyes and brain, thus providing an indirect diagnosis of blockage based on your blood flow
• Computed tomography angiography (CT scan): this is the main diagnostic test as it is more sensitive in diagnosing your condition. It works by finding the poor blood flow in your artery, telling us about the potential blockage ⁹

Treatment for CAD

Managing carotid artery disease is quite challenging, especially when you are asymptomatic.

Medications, surgical methods and lifestyle modification can be used to treat and manage your condition. The medication and surgeries have to be chosen based on your signs, symptoms and risk factors. The treatment should focus mainly on:^10,11

• Correcting diabetes using antidiabetic drugs and lifestyle changes
• Managing blood pressure with medications and lifestyle changes
• Controlling weight by exercising
• Having a healthy lifestyle
• Controlling cholesterol levels by use of statin
• Quitting smoking
• Antiplatelet medications like aspirin 
• The surgical procedures include carotid endarterectomy, stenting and transcarotid artery revascularization (TCAR)

What is the relationship between ischemic stroke and carotid artery disease?

The main cause of ischemic stroke is thromboembolism in the arteries of the brain. Studies have shown that 34% of cases of ischemic stroke are due to a clot in the carotid artery. Carotid artery disease, a significant factor in stroke occurrence, primarily leads to strokes through two main processes.¹²

The first process is when there is a hemodynamic impairment in your brain, and a blood vessel becomes narrowed, the brain responds by boosting blood flow through that vessel by raising the pressure. Additionally, it enables greater oxygen uptake to meet the brain's blood requirements. However, if these mechanisms for increasing blood pressure and oxygen intake fail, it leads to a decline in both blood and oxygen flow to the brain, resulting in irreversible brain damage known as ischemia.

The second process is thromboembolism by atherosclerotic plaque with or without narrowing of the blood vessels. This mechanism occurs more commonly compared to the former one. In this condition, either plaque, a fatty buildup in the blood vessel, will cause blockage in brain arteries, or a clot will travel from any body site, for example, the heart, and enter into your brain artery causing a blockage which results in an ischemic stroke.¹³

How do we prevent strokes associated with carotid artery disease?

• Changes in lifestyle factors by including any physical activity and a healthy diet like low salts and Mediterranean diet, intake of fruits, vegetables, whole grains, animal protein and fish are recommended¹⁴
• Addressing risk factors such as diabetes, quitting smoking, managing lipids, and controlling hypertension can significantly help in the secondary prevention of stroke
• Obesity management is recommended, which can be achieved by caloric restrictions and dietary habits along with physical activity for 150 minutes per week 
• Cessation of alcohol
• Following the medication regimen recommended by your healthcare provider is crucial in preventing strokes that result from carotid artery disease¹⁵

Summary 

Stroke, particularly ischemic stroke, is a leading cause of disability and death worldwide. It occurs when the blood flow to the brain is blocked, often due to carotid artery disease, where arteries are narrowed by cholesterol buildup. Ischemic strokes can present as transient ischemic attacks (TIAs) and have symptoms like sudden numbness, confusion, vision loss, and difficulty walking. Key risk factors include hypertension, atrial fibrillation, and atherosclerosis. Early diagnosis and treatment, including medications, surgery, and lifestyle changes, are crucial for managing both ischemic stroke and carotid artery disease to improve survival and prevent complications.